EDP Sciences
Free Access
Issue
A&A
Volume 587, March 2016
Article Number A78
Number of page(s) 27
Section Extragalactic astronomy
DOI https://doi.org/10.1051/0004-6361/201527373
Published online 19 February 2016

© ESO, 2016

1. Introduction

As already envisioned by Partridge & Peebles (1967), the hydrogen Lyman α (Lyα, λLyα = 1215.67 Å) line has become a prominent target in successful systematic searches for galaxies in the early Universe. Redshifted into the optical, this narrow high equivalent width line provides enough contrast to be effectively singled out in specifically designed observational campaigns. As of yet, mostly narrowband selection techniques have been employed (e.g. Hu et al. 1998; Taniguchi et al. 2003; Malhotra & Rhoads 2004; Shimasaku et al. 2006; Tapken et al. 2006; Gronwall et al. 2007; Ouchi et al. 2008; Grove et al. 2009; Shioya et al. 2009; Hayes et al. 2010; Ciardullo et al. 2012; Sandberg et al. 2015), but multi-object and integral-field spectroscopic techniques are now also frequently used to deliver large Lyman α emitter (LAE) samples (Cassata et al. 2011, 2015; Adams et al. 2011; Mallery et al. 2012; Bacon et al. 2015). Moreover, all galaxy redshift record holders in the last decade were spectroscopically confirmed by virtue of their Lyα line (Iye 2011; Ono et al. 2012; Finkelstein et al. 2013; Oesch et al. 2015; Zitrin et al. 2015) and a bright LAE at z = 6.6 is even believed to contain a significant amount of stars made exclusively from primordial material (so called Pop-III stars; Sobral et al. 2015).

As important as Lyα radiation is in successfully unveiling star formation processes in the early Universe, its correct interpretation appears notoriously complicated. Resonant scatterings in the interstellar and circum-galactic medium diffuse the intrinsic Lyα radiation field in real and frequency space. These scatterings increase the path length of Lyα photons within a galaxy and consequently Lyα is more susceptible to being destroyed by dust (see Dijkstra 2014, for a comprehensive review covering the Lyα radiative transfer fundamentals). Consequently, a galaxy’s Lyα observables are influenced by a large number of its physical properties. Understanding these influences is crucial to correctly interpret high-z LAE samples. In other words, we have to answer the question: What differentiates an LAE from other star-forming galaxies that do not show Lyα in emission?

Regarding Lyα radiation transport in individual galaxies, a large body of theoretical work investigated analytically and numerically how within simplified geometries certain parameters (e.g. density, temperature, dust content, kinematics, and clumpiness of the interstellar medium) affect the observed Lyα radiation field (e.g. Neufeld 1990; Ahn et al. 2003; Dijkstra et al. 2006; Verhamme et al. 2006; Laursen et al. 2013; Gronke & Dijkstra 2014; Duval et al. 2014). Commonly a spherical shell model is adopted. In this model, a thin shell of expanding, contracting, or static neutral gas represents the medium responsible for scattering Lyα photons. As a result, from scattering in the shell complex Lyα line morphologies arise and the expansion velocity and the neutral hydrogen column density of the shell are of pivotal importance in shaping the observable Lyα line. By introducing deviations from pure spherical symmetry, Zheng & Wallace (2014) and Behrens et al. (2014) show that the observed Lyα properties also depend on the viewing angle under which a system is observed. The Behrens et al. result is also found in large-scale cosmological simulations that were post-processed with Lyα radiative transport simulations (e.g. Laursen & Sommer-Larsen 2007; Laursen et al. 2009; Barnes et al. 2011). Recently more realistic hydrodynamic simulations of isolated galaxies have been paired with Lyα radiation transport simulations (Verhamme et al. 2012; Behrens & Braun 2014). These studies again underline the viewing angle dependence of the Lyα observables. In particular, they show that disks observed face-on are expected to exhibit higher Lyα equivalent widths and Lyα escape fractions than if they were observed edge-on. More importantly, these state-of-the-art simulations also emphasise the importance of small-scale interstellar medium structure that was previously not included in simple models. For example Behrens & Braun (2014) demonstrate how supernova-blown cavities are able to produce favoured escape channels for Lyα photons.

Observationally, when Lyα is seen in emission, the spectral line profiles can be typified by their distinctive shapes. In a large number of LAE spectra the Lyα line often appears asymmetric, with a relatively sharp drop on the blue and a more extended wing on the red side. A significant fraction of spectra also shows characteristic double peaks, with the red peak often being stronger than the blue (e.g. Tapken et al. 2004, 2007; Yamada et al. 2012; Hong et al. 2014; Henry et al. 2015; Yang et al. 2015). Interestingly, a high percentage of double peaked and asymmetric Lyα profiles appear well explained by the spherical symmetric scenarios mentioned above. Double-peaked profiles are successfully reproduced by slowly-expanding shells (vexp ≲ 100 km s-1) or low neutral hydrogen column densities NH i ≲ 1019cm-2, while high expansion velocities (vexp ~ 150 300 km s-1) with neutral hydrogen column densities of NH i ≳ 1020cm-2 produce the characteristic asymmetric profile with an extended red wing (Tapken et al. 2006, 2007; Verhamme et al. 2008; Schaerer et al. 2011; Gronke & Dijkstra 2014).

Further observational constraints on the kinematics of the scattering medium can be obtained by measuring the offset from non-resonant, rest-frame optical emission lines (e.g. Hα or [O iii]) to low-ionisation state metal absorption lines (e.g. O iλ1302 or Si ii λ1304). While the emission lines provide systemic redshift, some of metal absorption lines in a low ionisation state trace the kinematics of the cold neutral gas phase. Both observables are challenging to obtain for high-z LAEs and require long integration times on 8–10 m class telescopes (e.g. Shapley et al. 2003; Tapken et al. 2004) or even additional help from gravitational lenses (e.g. Schaerer & Verhamme 2008; Christensen et al. 2012). As the continuum absorption often remains undetected, just the offset between the rest-frame optical lines and the Lyα peaks are measured (e.g. McLinden et al. 2011; Guaita et al. 2013; Erb et al. 2014). Curiously, the observed Lyα profiles also agree well with those predicted by the simple shell model, when the measured offsets (typically Δv ~ 200 km s-1) are associated with shell expansion velocities in the simple shell model (Verhamme et al. 2008; Hashimoto et al. 2013; Song et al. 2014; Hashimoto et al. 2015). Only a few profiles appear incompatible with the expanding shells (Chonis et al. 2013). These profiles are characterised by extended wings or bumps in the blue side of the profile (Martin et al. 2014; Henry et al. 2015). However, given the aforementioned viewing angle dependencies in more complex scenarios, this overall success of the simple shell model appears surprising and is therefore currently under scrutiny (Gronke et al. 2015). Nevertheless, at least qualitatively the observations demonstrate, in concert with theoretical predictions, that LAEs predominantly have outflow kinematics and that such outflows promote the Lyα escape (see also Kunth et al. 1998; Mas-Hesse et al. 2003).

Kinematic information is moreover encoded in the rest-frame optical line emission alone. These emission lines trace the ionised gas kinematics and, in particular, the hydrogen recombination lines such as Hα relate directly to the spatial and spectral properties of a galaxy’s intrinsic Lyα radiation field. Therefore spatially resolved spectroscopy of a galaxy’s Hα radiation field constrains the initial conditions for the subsequent Lyα radiative transfer through the interstellar, circum-galactic, and intergalactic medium to the observer. At high z, however, most LAEs are so compact that they cannot be spatially resolved from the ground and, hence, all spatial information is lost in the analysis of the integrated spectra. Resolving the intrinsic Lyα radiation of typical high-z LAEs spatially and spectrally at such small scales would require integral field spectroscopy, preferably with adaptive optics, in the near infrared with long integration times. Although large samples of continuum-selected z ~ 2−3 star-forming galaxies have already been observed with this method (see Glazebrook 2013, for a comprehensive review), little is known about the Lyα properties of the galaxies in those samples.

In this paper we present results obtained from our integral-field spectroscopic observations with the aim to relate spatially and spectrally resolved intrinsic Lyα radiation field to its observed Lyα properties. Therefore we targeted the Hα line in all galaxies of the z ~ 0.030.18 Lyman alpha reference sample (LARS). The sample consists of 14 nearby laboratory galaxies, that have far-UV (FUV, λ ~ 1500 Å) luminosities similar to those of high-z star-forming galaxies. Moreover, to ensure a strong intrinsic Lyα radiation field, galaxies with large Hα equivalent widths were selected (EWHα ≥ 100 Å). The backbone of LARS is a substantial program with the Hubble Space Telescope (HST). In this program, each galaxy was observed with a combination of ultraviolet long-pass filters, optical broadband filters, as well as Hα and Hβ narrowband filters. These images were used to accurately reconstruct Lyα images of those 14 galaxies. Moreover, UV spectroscopy with HSTs Cosmic Origins Spectrograph (COS) is available for the whole sample.

This paper is the seventh in a series presenting results of the LARS project. In Östlin et al. (2014; hereafter Paper I) we detailed the sample selection, the observations with HST and the process to reconstruct Lyα images from the HST data. In Hayes et al. (2014; hereafter Paper II) we presented a detailed analysis of the imaging results. We found that six of the 14 galaxies are indeed analogous to high-z LAEs, i.e. they would be selected by the conventional narrowband survey selection requirement1: EWLyα> 20 Å. The main result of Paper II is that a galaxy’s morphology seen in Lyα is usually very different compared to its morphological appearance in Hα and the FUV; in particular, Lyα is often less centrally concentrated and so these galaxies are embedded in a faint low surface brightness Lyα halo. The results in Paper II (see also Hayes et al. 2013) therefore provide clear observational evidence for resonant scattering of Lyα photons in the neutral interstellar medium. Pardy et al. (2014; hereafter Paper III) subsequently presented 21 cm observations tracing the neutral hydrogen content of the LARS galaxies and the results supported the complex coupling between Lyα radiative transfer and the properties of the neutral medium. In Guaita et al. (2015; hereafter Paper IV), the morphology of the LARS galaxies was thoroughly re-examined. By artificially redshifting the LARS imaging data-products, it was confirmed that morphologically LARS galaxies indeed resemble z ~ 2−3 star forming galaxies. Rivera-Thorsen et al. (2015; hereafter Paper V) then presented high-resolution FUV COS spectroscopy of the full sample. Analysing the neutral interstellar medium kinematics as traced by the low-ionisation state metal absorption lines, it was shown that all galaxies with global Lyα escape fractions >5% appear to have outflowing winds. Finally, in Duval et al. (2016; hereafter Paper VI), a detailed radiative transfer study of one LARS galaxy was performed using all the observational constraints assembled within the LARS project, and including data that is presented in this paper. In particular it was shown that this galaxy’s spatial and spectral Lyα emission properties are consistent with scattering of Lyα photons by outflowing cool material along the minor axis of the disk.

Now, in the first analysis of our LARS integral-field spectroscopic data presented here, we focus on a comparison of results obtainable from spatially resolved Hα kinematics to results from the LARS HST Lyα imaging and 21 cm H i observations. In a subsequent publication (Orlitova, in prep.) we will combine information from our 3D Hα spectroscopy with our COS UV spectra to constrain the parameters of outflowing winds.

This paper is not the first in relating observed spatially resolved Hα observations to a local galaxy’s Lyα radiation field. Recently in a pioneering study exploiting MUSE (Bacon et al. 2014) science verification data, Bik et al. (2015) showed that an asymmetric Lyα halo around the main star-forming knot of ESO338-IG04 (Hayes et al. 2005; Östlin et al. 2009; Sandberg et al. 2013) can be linked to outflows seen in the Hα radial velocity field. Moreover, the kinematic constraints provided by our observations were already used for modelling the Lyα scattering in one LARS galaxy (Paper VI), and also here galactic scale outflows were required to explain the galaxy’s Lyα radiation. With the full data set presented here, we now study whether such theoretical expected effects are indeed common among Lyα-emitting galaxies.

The outline of this manuscript is as follows: in Sect. 2 our PMAS observations of the LARS sample are detailed. The reduction of our PMAS data is explained in Sect. 3. Ancillary LARS data products used in this manuscript are described briefly in Sect. 4. The derivation and analysis of the Hα velocity and dispersion maps is presented in Sect. 5. In Sect. 6 the results are discussed and finally we summarise and conclude in Sect. 7. Notes on individual objects are given in Appendix A.

2. Observations with PMAS

Table 1

Log of PMAS lens array observations of the LARS sample.

We observed all LARS galaxies with the Potsdam Multi-Aperture Spectrophotometer (PMAS; Roth et al. 2005) at the Calar Alto 3.5 m telescope during four nights from March 12 to March 15, 2012 (PMAS run212), except for LARS 13, which was observed on October 10 2011 (PMAS run197). We used PMAS in the lens array configuration, where 256 fibers are coupled to a 16 × 16 lens array that contiguously samples the sky. Depending on the extent of the targeted galaxy, we used either the standard magnification mode, which provides an 8′′×8′′ field of view (FoV) or the double magnification mode2, where the FoV is 16′′× 16′′. The backwards-blazed R1200 grating was mounted on the spectrograph. To ensure proper sampling of the line spread function the 4k×4k CCD (Roth et al. 2010) was read out unbinned along the dispersion axis. This set-up delivers a nominal resolving power from R ~ 5000 to R ~ 8000 within the targeted wavelength ranges3. In Sect. 3.3 we show that while the nominal resolving powers are met on average, the instrumental broadening varies at small amplitudes from fibre to fibre.

On-target exposures were usually flanked by 400 s exposures of empty sky near the target. These sky frames serve as a reference for removing the telluric background emission. Owing to an error in our observing schedule, no sky frames were taken for LARS 4, LARS 7, and LARS 9 (2012-03-12 pointing). Fortunately, this did not render the observations unusable, since there are enough blank-sky spectral pixels (so called spaxels) within those on-target frames to provide us with a reference sky (cf. Sect. 3.2).

Observing blocks of one hour were usually flanked by continuum and HgNe arc lamp exposures used for photometric and wavelength calibration. We obtained several bias frames throughout each night when the detector was idle during target acquisition. Spectrophotometric standard stars were observed at the beginning and at the end of each astronomical night (BD+75d325 & Feige 67 from Oke 1990, texp. = 600 s). Twilight flat exposures were taken during dawn and dusk.

In Table 1 we provide a log of our observations. By changing the rotation of the grating, we adjusted the wavelength ranges covered by the detector, such that the galaxies Hα – [N ii] complex is located near the centre of the CCD. We emphasise that ± 350 Å at the upper/lower end of the quoted spectral ranges are affected by vignetting (a known “feature” of the PMAS detector; see Roth et al. 2010). We also quote the average spectral resolution of our final data sets near Hα. The determination of this quantity is described in Sect. 3.3. The tabulated seeing values refer always to the average full width at half maximum (FWHM) of the guide star point-spread function (PSF) measured during the exposures with the acquisition and guiding camera of PMAS. This value is on average 0.2′′higher than the DIMM measurements (see also Husemann et al. 2013).

In Fig. 1 we show the wavelengths of the redshifted Hα line for all LARS galaxies overlaid on the typical night sky emission spectrum at Calar Alto from Sánchez et al. (2007a). As can be seen for two galaxies (LARS 13 and LARS 14), the Hα line signal is contaminated by telluric line emission and two other galaxies (LARS 9 and LARS 12) have their Hα line within an absorption band. This, however, has no effect on the presented analysis. For LARS 13 and LARS 14, we could optimally subtract the interfering sky lines from the science exposures using the separate sky frames. Moreover, as we use only spaxels with high signal-to-noise Hα lines in our analysis (see also Sect. 5), the high frequency changes within the telluric absorption bands do not alter the quantified features, i.e. width and peak position, of the profiles.

thumbnail Fig. 1

Wavelengths of the redshifted Hα lines of the LARS galaxies (vertical dashed lines) compared to the night sky emission spectrum at Calar Alto (Sánchez et al. 2007a). Grey regions indicate the telluric absorption bands (O2B-Band: 6887 Å6919 Å, O2A-Band: 7607 Å7633 Å, and H2O a-Band: 7168 Å7304 Å, see e.g. Cox 2000).

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3. The PMAS data reduction

3.1. Basic reduction with p3d

For reducing the raw data the p3d-package4 (Sandin et al. 2010, 2012) was utilised. This pipeline covers all basic steps needed for reducing fiber-fed integral field spectroscopic data: bias subtraction, flat fielding, cosmic ray removal, tracing and extraction of the spectra, correction of differential atmospheric refraction, and co-addition of exposures (see also Turner 2010). We now describe how we applied the tasks of p3d on our raw data for each of these steps5:

  • Bias subtraction: Master bias frames were created by p3d_cmbias. These master bias frames were then subtracted from the corresponding science frames. Visual inspection of the bias subtracted frames showed no measurable offsets in unexposed regions between the four quadrants of the PMAS CCD, which attests to optimal bias removal.

  • Flat fielding: Each of the 256 fibers has its own wavelength dependent throughput curve. To determine these, the task p3d_cflatf was applied on the twilight flats. The determined curves are then applied in the extraction step of the science frame (see below) to normalise the extracted spectra.

  • Cosmic ray removal: Cosmic ray hits on the CCD were removed with p3d_cr. Visual inspections guided by the parameter study of Husemann et al. (2012) lead us to apply the L.A. Cosmic algorithm (van Dokkum 2001) with σlim = 5, σfrac = 1, flim = 15, a grow radius of 2 and a maximum of four iterations.

  • Tracing and extraction: Spectra were extracted with the modified Horne (1986) optimal extraction algorithm (Sandin et al. 2010). The task p3d_ctrace was used to determine the traces and the cross-dispersion profiles of the spectra on the detector. Spectra were then extracted with p3d_cobjex, also using the median recentring recommended in Sandin et al. (2012).

  • Wavelength calibration: We obtained dispersion solutions (i.e. mappings from pixel to wavelength space) from the HgNe lamp frames using a sixth-order polynomial with p3d_cdmask . The wavelength sampling of the extracted science spectra is typically 0.46 Å px-1. We further improved the wavelength calibration of the science frames by applying small shifts (typically 0.1−0.3 px) determined from the strong 6300 Å and 6364 Å [O i] sky lines (not available within the targeted wavelength range for LARS 12, 13, and 14)

  • Sensitivity function and flux calibration: Using extracted and wavelength-calibrated standard star spectra, we created a sensitivity function utilising p3d_sensfunc. Absorption bands in the standard star spectra, as well as telluric absorption bands (see Fig. 1), were masked for the fit. Extinction curves were created using the empirical formula presented in Sánchez et al. (2007b) with the extinction in V-band as measured by the Calar Alto extinction monitor6. We flux-calibrated all extracted and wavelength-calibrated science frames with the derived sensitivity function and extinction curve with p3d_fluxcal.

The final data products from the p3d-pipeline are flux- and wavelength-calibrated data cubes for all science exposures, as well as the corresponding error cubes. From here we now perform the following reduction steps with our custom procedures written in python7.

3.2. Sky subtraction and co-addition

  • Sky subtraction: All sky frames were reduced as science frames, as described in the previous section. These extracted, wavelength- and flux-calibrated sky frames were then subtracted from the corresponding science frames and errors were propagated accordingly. Unfortunately, no separate sky exposures were taken for three targets (LARS 4, LARS 7, and LARS 9; see also Sect. 2). For these targets we created a narrowband image of the Hα-[N ii] region by summing up the relevant layers in the datacube. In this image, we selected spaxels that do not contain significant amounts of flux. From these spaxels then an average sky spectrum was created, which was then subtracted from all spaxels. As the spectral resolution varies across the FoV (see also Sect. 3.3), this method produces some residuals at the position of the sky lines, which however do not touch the Hα lines of the affected targets.

  • Stacking: We co-added all individual flux-calibrated and sky-subtracted data cubes using the variance-weighted mean. For this calculation the input variances were derived from squaring the error cubes. Before co-addition we ensured by visual inspection that there are no spatial offsets between individual exposures.

3.3. Spectral resolving power determination

thumbnail Fig. 2

Representative resolving power map for the observation of LARS 1. The resolution is expressed as vFWHM of a 1D Gaussian fit. Black spaxels at the positions (x,y) = (0,14) and (8,15) are dead fibres.

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To determine the intrinsic width of our observed Hα lines, we need to correct for instrumental broadening by the spectrograph’s line spread function (the spectrograph’s resolving power; Robertson 2013). It is known that for PMAS the resolving power varies from fibre to fibre and with wavelength (e.g. Sánchez et al. 2012). To determine the broadening at the wavelength of the Hα line, we use the HgNe arc lamp exposures, which were originally used to wavelength calibrate the on-target exposures. We first create wavelength-calibrated data cubes from these arc frames. Next, we select two strong arc lamp lines that are nearest in wavelength to the corresponding galaxy’s Hα line. Finally, we fit 1D Gaussians in each spaxel to each of those lines (e.g. similar to Alonso-Herrero et al. 2009). Typically the separation from a galaxy’s Hα line to one of those arc lamp lines is ~50 Å. The difference between the FWHM of the fits to the different lines is typically ~1 km s-1, hence we take the average of both at the position of Hα as the resolving power for each spaxel. We point out that the arc-lamp lines FWHM is always sampled by more than 2 pixels, therfore aliasing effects can be neglected (Turner 2010).

This procedure provides us with resolving power maps. As an example, we show a so-derived map for the observations of LARS 1 in Fig. 2. We note that the spatial gradient seen in Fig. 2 is not universal across our observations (see Sánchez et al. 2012, for an explanation). We further note that the formal uncertainties on the resolving power determination are negligible in comparison to the uncertainties derived on the Hα profiles in Sect. 5.

In Table 1 we give the mean resolving power at the position of Hα for each galaxy as . Variations within the FoV typically have an amplitude of ~30 km s-1. The average resolving power of all our observations is R = 5764 or 52 km s-1, which is consistent with the values given in the PMAS online grating manual8.

3.4. Registration on astrometric grid of HST observations

To facilitate a comparison of our PMAS observations with the HST imaging results from Hayes et al. (2014), we have to register our PMAS data cubes with respect to the LARS HST data products. As explained in Östlin et al. (2014), all HST images are aligned with respect to each other and have a common pixel scale of 0.04′′ px-1. We use the continuum-subtracted Hα line image as a reference. From this image we create contours that highlight the most prominent morphological features in Hα. We then produce a continuum-subtracted Hα map from the PMAS data cubes by subtracting a version of the data cube that is median-filtered in spectral direction. Finally, we visually match the contours from the reference image with the PMAS Hα map. This constrains the position of the PMAS FoV relative to the HST imaging. We emphasise that we make full use of the FITS header world-coordinate representation in our method, i.e. the headers of our final data cubes are equipped with keyword value pairs to determine the position of each spaxel on the sky (Greisen & Calabretta 2002; Calabretta & Greisen 2002).

For galaxies with a single PMAS pointing, we present the final result of our registration procedure in Fig. 5 (or Figs. 6 and 7, for the two galaxies with two PMAS pointings). For each LARS galaxy, the Hα line intensity map extracted from our HST observations is shown in the top panel and can be compared to the PMAS Hα signal-to-noise ratio (S/N) map in the panel below. The S/N values for each spaxel are calculated by summation of all flux values within a narrow spectral window centred on Hα and subsequent division by the square root of the sum of the variance values in that window. The width of the summation window is taken as twice the Hα lines FWHM. Our display of the HST Hα images uses an asinh-scaling (Lupton et al. 2004) cut at 95% of the maximum value (see Sect. 4 and Fig. 3 of Hayes et al. 2014, for absolute Hα intensities) and we scaled our PMAS Hα S/N maps logarithmically. The inferred final position of the PMAS FoV is indicated with a white square (or two squares for the galaxies with two pointings) within the Hα panel. Also shown are the Hα contours used for visual matching. As can be seen, most of the prominent morphological characteristics present in the HST Hα maps are unambiguously identifiable in the lower resolution PMAS maps, exemplifying the robustness of our registration method.

4. Ancillary LARS data products

We compare our PMAS data to the HST imaging results of the LARS project presented in Hayes et al. (2013) and Paper II. Specifically, we use the continuum-subtracted Hα and Lyα images that were presented in Paper II. These images were produced from our HST observation using the LARS extraction software LaXs (Hayes et al. 2009). Details on the observational strategy, reduction steps, and analysis performed to obtain these HST data products used in the present study are given in Paper II and Paper I.

We also compare with the published results of the LARS H i imaging and spectroscopy observations that were obtained with the 100m Robert C. Byrd Green Bank Telescope (GBT) and the Karl G. Jansky Very Large Array (VLA). The GBT single-dish spectra are present for all systems, except that the H i signal could not be detected in the three LARS galaxies with the largest distances (LARS 12, LARS 13, and LARS 14). The VLA interferometric imaging results are only available for LARS 2, LARS 3, LARS 4, LARS 8, and LARS 9. We emphasise that with beam sizes from 59′′ to 72′′ (VLA D-configuration) the spatial scale that is resolved within the VLA H i images is much larger than our PMAS observations. Moreover, the single-dish GBT spectra are sensitive to H i at the observed frequency range within 8 of the beam. Full details on data acquisition, reduction, and analysis are presented in Paper III.

5. Analysis and results

5.1. Hα velocity fields

thumbnail Fig. 3

Integrated continuum-subtracted Hα profiles of the LARS galaxies (black) compared to summed 1D Gaussian model profiles (grey) from which radial-velocity and velocity-dispersion maps were generated.

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thumbnail Fig. 4

Uncertainties on derived velocity dispersions (left panel) and radial velocities (right panel) for Gaussian profile fits to Hα for all galaxies. All uncertainties for a specific galaxy have the same symbol according to the legend in the right panel.

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thumbnail Fig. 5

Comparison of LARS HST imaging results of the LARS sample to spatially resolved PMAS Hα spectroscopy. North is always up and east is always to the left. For each galaxy from top to bottom: the first panel shows the LaXs Hα line intensity map; tick labels indicate right ascension and declination and an asinh-scaling is used cut at 95% of the maximum value. The second panel shows a S/N map of the continuum-subtracted Hα signal observed with PMAS. Tick labels in the PMAS S/N map are in arc-seconds; the scaling is logarithmic from 1 to 103 and only spaxels with S/N> 1 are shown. The third panel shows the LARS Lyα images with a colour bar indicating the flux scale in cgs-units; scaling is the same as in the Hα map. The fourth panel shows resolution-corrected HαvFWHM maps from our PMAS observations and the corresponding HαvLOS maps are shown in the fifth panel. In the first and third panel, we indicate the position and extent of the PMAS field of view with a white box. Cyan contours in the HST Hα image are contours of constant surface brightness, adjusted to highlight the most prominent morphological features. Similarly, magenta contours in the HST Lyα images indicate the Lyα morphology; these contours are also shown in the fourth and fifth panel. To highlight the difference between Lyα and Hα, the Lyα and Hα panels contain as dashed yellow lines the contours from the Hα and Lyα panels, respectively.

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thumbnail Fig. 6

Comparison of LARS HST imaging results to spatially resolved PMAS Hα spectroscopy for LARS 9. For detailed description of individual panels see caption of Fig. 5. This galaxy was covered with 2 PMAS pointings. Hatched regions in the vLOS map indicate regions, where the Hα emission shows a more complex profile that could not be described by a simple Gaussian (see also Appendix A.9).

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thumbnail Fig. 7

Same as Fig. 6, but for LARS 13. Hatched region in the vLOS map indicates the region, where the Hα emission shows a more complex profile that could not be described by a simple Gaussian (see also Appendix A.13).

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We condense the kinematical information traced by Hα in our data cubes into two-dimensional maps depicting velocity dispersion and line-of-sight radial velocity at each spaxel. Both quantities are derived from 1D Gaussian fits to the observed line shapes from the continuum-subtracted cube (see Sect. 3.4). We calculate the radial velocity offset vLOS to the central wavelength value given by the mean of all fits and the FWHM of the fitted line in velocity space vFWHM. To obtain higher S/N ratios in the galaxies’ outskirts we use the weighted Voronoi tessellation binning algorithm by Diehl & Statler (2006), which is a generalisation of the Voronoi binning algorithm of Cappellari & Copin (2003).

We visually scrutinised the fits to the spectra and decided that lines observed at a S/N of six were still reliably fit. Hence, six defines the minimum S/N in the Voronoi binning algorithm. Furthermore, we adopted a maximum bin size of 3 × 3 pixels. In those calculations signal and noise are defined as in Sect. 3.4. In what follows, only results from the fits to bins that meet the minimum S/N requirement are considered. Most of the bins used are actually only a single spaxel, and very few bins in the outskirts of the galaxies meeting the minimum S/N criterion do consist of 2 or 3 spaxels. In practice this means that we are typically sensitive to regions at Hα surface brightness higher than 5 × 10-16 erg s-1 cm-2 arcsec-2. Using the Kennicutt (1998) conversion and neglecting extinction, this translates to a detection limit of star-formation rate surface densities ~3 × 10-2M yr-1 kpc-2, more than an order of magnitude deeper than probed by high redshift integral field spectroscopy studies (~1 M yr-1 kpc-2, see e.g. Law et al. 2009).

By visual inspection we also ensured that 1D Gaussian profiles are a sufficient model of the observed Hα profiles seen in the PMAS LARS data cubes. We only have some spaxels where a 1D Gaussian certainly fails to reproduce the complexity of the observed spectral shape in two galaxies (LARS 9 and LARS 13). Moreover, in LARS 14 weak broad wings are visible in the individual Hα profiles. We have not attempted to model these special cases, but we describe their qualitative appearance in detail in the Appendices A.9, A.13, and A.14, and acknowledge their existence in our interpretation in Sect. 6. To demonstrate the overall quality of our Hα velocity fields, we compare in Fig. 3 the integrated Hα profiles of the LARS galaxies to the sum of the fitted 1D Gaussians used to generate the vFWHM and vLOS maps. As can be seen, the observed profile and that derived from the models are largely in agreement. The strongest deviation between data and models is apparent in LARS 14, where the broad wings of the observed Hα profile are not reproduced at all by 1D Gaussian models (cf. Sect. 6.1 and Appendix A.14).

To estimate formal uncertainties on vFWHM and vLOS, we use a Monte Carlo technique: we perturb our spectra 100 times with the noise from our noise cubes and then fit the 1D Gaussian profile in exactly the same way to each of these 100 realisations. The width of the distribution of all fit results characterised by their standard deviation gives a robust measure for the uncertainty on the derived quantities (cf. Appendix B.4. in Davies et al. 2011). The central moment of the distribution is the final value that is shown in our maps. In Fig. 4 we indicate, for all performed fits, the error on the velocity dispersion ΔvFWHM and on radial velocity ΔvLOS as a function of the lines S/N. On average our uncertainties on vFWHM and vLOS follow the scaling laws expected for fitting Gaussian profiles to noisy emission-line spectra (Landman et al. 1982; Lenz & Ayres 1992). For reference, at our minimum S/N = 6 we have typical errors of ΔvFWHM ≈ 30 km s-1 and ΔvLOS ≈ 10 km s-1, and at the median (mean) S/N of our data – S/Nmedian = 22 (S/Nmean = 50), we obtain ΔvFWHM ≈ 7 km s-1 (3 km s-1) and ΔvLOS ≈ 3 km s-1 (1 km s-1).

In Fig. 5 we show the resulting vFWHM and vLOS maps together with the LaXs Lyα images (lower three panels). Maps and images of the galaxies observed with two pointings are shown in Figs. 6 and 7 for LARS 9 and LARS 13, respectively. All vFWHM maps have been corrected for instrumental broadening using the spectral resolving power maps derived in Sect. 3.3. In all vLOS and vFWHM panels, we overlay contours derived from the Lyα image to emphasise distinctive morphological Lyα properties.

Individual maps are discussed in Appendix A. Using the classification scheme introduced by Flores et al. (2006; see also Sect. 3.3 in Glazebrook 2013) the LARS galaxies can be characterised by the qualitative appearance of their velocity fields:

  • Rotating disks: LARS 8 and LARS 11. Both galaxies show a regular symmetric dipolar velocity field with a steep gradient in the central regions. This steep gradient is also the reason for artificially broadened emission near the kinematical centre. Morphologically both galaxies also bear resemblance to a disk and the kinematical axis is aligned with the morphological axis. However, we point out in Appendix A.8 that LARS 8 can also be classified as a shell galaxy, hinting at a recent merger event.

  • Perturbed rotators: LARS 1, LARS 3, LARS 5, LARS 7, and LARS 10. In those galaxies traces of orbital motion are still noticeable, but the maps look either significantly perturbed compared to a classical disk case (LARS 3, LARS 5, LARS 7, and LARS 10) and/or the observed velocity gradient is very weak (LARS 1, LARS 5 and LARS 10). Based solely on morphology, we previously classified two of those galaxies as dwarf edge-on disks (LARS 5 and LARS 7; Paper II; Paper III). Moreover, LARS 3 is a member of a well known merger of two similar massive disks (see also Appendix A.3). From our imaging data alone LARS 7 and LARS 10 bear resemblance to shell galaxies (see also Appendices A.7 and A.10).

  • Complex kinematics: LARS 2, LARS 4, LARS 6, LARS 9, LARS 12, LARS 13, and LARS 14. These seven galaxies are characterised by more chaotic vLOS maps and they all have also irregular morphologies. Four of the irregulars consist of photometrically well-separated components that are also kinematically distinct (LARS 4, LARS 6, LARS13 and LARS 14), while the other three each have their own individual peculiarities (LARS 2, LARS 9 and most spectacularly LARS 12 see also Appendices A.2, A.9, and A.12).

These kinematic classes are also listed in Table 2.

Notably, in all LARS galaxies, except for LARS 6, we observe high-velocity dispersions (vFWHM ≳ 100 km s-1); the most extreme case is LARS 3 where locally lines as broad as vFWHM ~ 400 km s-1 are found. The observed width of the Hα line seen in our vFWHM maps can be described as a successive convolution of the natural Hα line (7 km s-1 FHWM) with the thermal velocity distribution of the ionised gas (21.4 km s-1 FWHM at 104 K) and with non-thermal motions in the gas (e.g. Jiménez-Vicente et al. 1999). Since all our dispersion measurements are significantly higher than the thermally broadened profile non-thermal motions dominate the observed linewidths. Non-thermal motions could be centre-to-centre dispersions of the individual H ii regions and turbulent motions of the ionised gas. The latter appears to be the main driver for the observed line widths, since the observed velocity dispersions are highly supersonic (i.e. 10 km s-1 for H ii at 104 K; see also Sect. 5.1 in Glazebrook 2013).

5.2. Global kinematical properties: vshear, σ0, σtot and vshear/σ0

Table 2

Global kinematic parameters from Hα for the LARS galaxies, calculated as described in Sect. 5.2.

We now quantify the global kinematical properties of our Hα velocity fields that were qualitatively discussed in the previous section. Therefore, we compute three non-parametric estimators that are commonly adopted in the literature for this purpose (e.g. Law et al. 2009; Basu-Zych et al. 2009; Green et al. 2010; Gonçalves et al. 2010; Glazebrook 2013; Green et al. 2014; Wisnioski et al. 2015): shearing velocity vshear, intrinsic velocity dispersion σ0, and their ratio vshear/σ0. We describe the physical meaning of those parameters and our method to determine them in the following three subsections. Furthermore, we also calculate the integrated velocity dispersion σtot. This measure provides a useful comparison for unresolved distant galaxies. Our results on vshear, σ0, σtot and vshear/σ0 are tabulated in Table 2.

5.2.1. Shearing velocity vshear

The shearing velocity vshear is a measure for the large-scale gas bulk motion along the line of sight. We calculate it via (1)Here we take the median of the lower and upper fifth percentile of the distribution of values in the vLOS maps for vmin and vmax, respectively. This choice ensures that the calculation is robust against outliers while sampling the true extremes of the distribution. We conservatively estimate the uncertainty by propagating the full width of the upper and lower fifth percentile of the velocity map. We list our results for vshear in the second column of Table 2. Our derived vshear values for the LARS sample range from 30 km s-1 to 180 km s-1, with 65 km s-1 being the median. This is less than half the typical maximum velocity vmax of Hα rotation curves observed in spiral galaxies, e.g. vmax = 145 km s-1 is the median of 153 local spirals (Epinat et al. 2010). In contrast to our vshear measurement, vmax values are inclination corrected. In a sample with random inclinations on average the correction is expected (e.g. Law et al. 2009), but even with this correction classical disks appear still incompatible with most of our measurements by a factor larger than two. We only find vshear values compatible with local rotators for the two galaxies that we classified as rotating disks in Sect. 5.1. Nevertheless, high vshear values do not necessarily imply the presence of a disk. Large-scale bulk motions at high amplitude also occur in close encounters of spatially and kinematically distinct companions (e.g. LARS 13).

Sensitivity is an important factor in the determination of the observed vshear. An observation of less depth does not detect fainter regions at larger radii, which may have the highest velocities. Indeed, for most of our galaxies the spatial positions of vmin and vmax values are in those outer lower surface-brightness regions. Hence observations of lower sensitivity are biased to lower vshear values. This sensitivity bias is strongly affecting high-z studies because these kinds of observations are often only limited to the brightest regions (Law et al. 2009; Gonçalves et al. 2010).

5.2.2. Intrinsic velocity dispersion σ0

The intrinsic velocity dispersion σ0 (sometimes also called resolved velocity dispersion or local velocity dispersion, cf. Glazebrook 2013, Sect. 1.2.1) is in our case a measure for the typical random motions of the ionised gas within a galaxy. We calculate it by taking the flux weighted average of the observed velocity dispersions in all spaxels, i.e. (2)Here is the Hα flux in each spaxel and σspaxel is the velocity dispersion measured in that spaxel; the sum runs over all spaxels with S/N ≥ 6 (Sect. 5.1). This kind of flux-weighted summation σ0 has been widely adopted in the literature to quantify the typical intrinsic velocity dispersion component (e.g. Östlin et al. 2001; Law et al. 2009; Gonçalves et al. 2010; Green et al. 2010, 2014; Glazebrook 2013).

The PSF smearing in the presence of strong velocity gradients broadens the Hα line at the position of the gradients9. This kind of broadening could bias our calculation of the intrinsic velocity dispersion. At the distances of the LARS galaxies, our typical seeing-disk PSF FWHM of 1′′ corresponds to scales of 0.6 kpc to 3 kpc. In most of our observations, this average PSF FWHM is comparable to the size of one PMAS spaxel (1′′×1′′) and most of the LARS galaxies exhibit rather weak velocity gradients. The PSF smearing effect is only seen in galaxies with strong velocity gradients (e.g. LARS 8; see also Appendix A.8), especially when observed with PMAS’ 0.5′′×0.5′′ magnification mode (e.g. LARS 12; see also Appendix A.12). In principle, the effect could be corrected by subtracting a PSF-smeared kinematical model of the vLOS velocity field. Given the complexity of our observed velocity fields, however, this is not practicable. And, moreover, at z ~ 0.1Green et al. (2014) find that for classical rotating disk kinematics the velocity dispersions corrected by a kinematical model are, on average, negligible. Comparisons between adaptive-optics derived PSF-smearing unaffected σ0 values to those derived from seeing-limited observations were presented by Bassett et al. (2014). They find that while for one galaxy σ0 remains unaffected by an increase in spatial resolution, for the other galaxy σ0 decreases by ~10 km s-1. Bassett et al. (2014) attribute the ~10 km s-1 discrepancy in one of their galaxies to a strong velocity gradient that is co-spatial with the strongest emission. A similar comparison is possible for three of our LARS galaxies – LARS 12, LARS 13 and LARS 14. For these galaxies adaptive optics IFS observations were presented by Gonçalves et al. (2010) (see Appendices A.12A.14). Gonçalves et al. (2010) derive σ0 = 67 km s-1, σ0 = 74 km s-1 and σ0 = 71 km s-1 for LARS 12, LARS 13, and LARS 14, respectively. These values are in agreement with our measurements of σ0 = 73 km s-1, σ0 = 69 km s-1, and σ0 = 67 km s-1 for those galaxies10. From all these considerations we are certain, that the adopted formalism in Eq. (2) gives a robust estimate of the intrinsic velocity dispersion.

We list our derived values for σ0 in the third column of Table 2. In general, the ionised gas kinematics of the LARS galaxies are characterised by high intrinsic velocity dispersions ranging from 40 km s-1 to 100 km s-1 with 54 km s-1 being the median of the sample. Such high intrinsic dispersions are in contrast to H ii velocity dispersions of ~10−50 km s-1 typically found in local spirals (e.g. Epinat et al. 2008a,b, 2010; Erroz-Ferrer et al. 2015). In high-z, star-forming galaxies intrinsic dispersions 50 km s-1 appear to be the norm (e.g. Puech et al. 2006; Genzel et al. 2006; Law et al. 2009; Förster Schreiber et al. 2009; Erb et al. 2014; Wisnioski et al. 2015). In the local z ≲ 0.1 Universe, high intrinsic velocity dispersions are also found in the studies of blue compact galaxies (BCGs; Östlin et al. 1999, 2001), local Lyman break analogues (Basu-Zych et al. 2009; Gonçalves et al. 2010) and (ultra-)luminous infrared galaxies (e.g. Monreal-Ibero et al. 2010). Finally, σ0 values of comparable amplitude are also common in a sample of 67 bright Hα emitters (1040.6LHα ≤ 1042.6) (Green et al. 2010, 2014). Indeed, Green et al. (2010) and Green et al. (2014) show that star formation rate (SFR) is positively correlated with intrinsic velocity dispersion. We confirm this trend among our LARS galaxies and discuss its implications on Lyα observables in Sect. 6.3.

5.2.3. vshear/σ0 ratio

The ratio vshear/σ0 is a metric to quantify whether the gas kinematics are dominated by turbulent or ordered (in some cases orbital) motions. Our results for this quantity are listed in Table 2. Given the above (Sects. 5.2.1 and 5.2.2) mentioned differences to disks, it appears cogent that our vshear/σ0 ratios (median 1.4, mean 1.6) are much smaller than typical disk vshear/σ0 ratios ~4−8 (first to last quartile of the Epinat et al. sample).

Objects with vshear/σ0< 1 are commonly labelled dispersion-dominated galaxies (Newman et al. 2013; Glazebrook 2013). According to this criterion, five galaxies of the 14 LARS sample are dispersion dominated: LARS 2, LARS 5, LARS 7, LARS 10, and LARS 14; three perturbed rotators and two with complex kinematics. Dispersion-dominated galaxies are frequently found in kinematic studies of high-z, star-forming galaxies. Local samples with a similar percentage (~35%) of dispersion-dominated galaxies are the blue compact galaxies studied by Östlin et al. (2001) or the Lyman break analogues studied by Gonçalves et al. (2010). In Sect. 6.3, we show that dispersion-dominated systems are more likely to have a significant fraction of Lyα photons escaping.

5.2.4. Integrated velocity dispersion σtot

For reference we also compute the integrated (spatially averaged) velocity dispersion σtot. This measure provides a useful comparison for studies of unresolved distant galaxies where no disentanglement between ordered and disordered, random motions are possible (e.g. McLinden et al. 2011; Guaita et al. 2013; McLinden et al. 2014; Rhoads et al. 2014; Erb et al. 2014).

We obtain σtot by calculating the square root of the second central moment of the integrated Hα profiles shown in Fig. 3. The results are given in the fourth column of Table 2. Our integrated velocity dispersions for the LARS sample range from 46 km s-1 to 115 km s-1, with 70 km s-1 being the median of the sample. Given the high S/N of the integrated profiles the formal uncertainties on this σtot are very small (~10-2 km s-1). As expected, when large-scale motions dominate in the integrated spectrum (i.e. high vshear/σ0 ratios), σtot is significantly larger than σ0, but for dispersion-dominated systems the discrepancy becomes less extreme.

6. Discussion: influence of Hα kinematics on a galaxy’s Lyα emission

6.1. Clues on Lyα escape mechanisms via spatially resolved Hα kinematics

Recent theoretical modelling of the Lyα radiative transport within realistic interstellar medium environments predicts that small-scale interstellar medium physics are a decisive factor in regulating the Lyα escape from galaxies (Verhamme et al. 2012; Behrens & Braun 2014). In particular, Behrens & Braun (2014) demonstrate how supernova blown outflow cavities become favoured escape channels for Lyα radiation. These cavities naturally occur in zones of enhanced star formation activity, where the input of kinetic energy from supernovae and stellar winds into the surrounding interstellar medium is also expected to drive highly turbulent gas flows. Do we see supporting evidence for this scenario in our IFS observations of the LARS galaxies?

As described in Sect. 5.1, all our velocity fields are characterised by broad profiles that are best explained by turbulent flows of ionised gas. The more violent these flows are, the more likely they carve holes or bubbles through the interstellar medium through which the ionised gas eventually flows out into the galaxy’s halo. Close inspection of Fig. 5 reveals, that in LARS 1, LARS 3, and LARS 13 (Fig. 7) zones of high Lyα surface brightness occur near or even co-spatial to zones where for these galaxies the maximum velocity dispersions are observed. In both LARS 1 and LARS 13, these zones are also co-spatial with the regions of highest Hα surface-brightness, hence, here the SFR density is highest. Moreover, in LARS 1 the Hα image shows a diffuse fan-like structure emanating outwards from this star-forming knot (Paper II; Paper I). Finally, the analysis of the COS spectra in Paper V shows blueshifted, low-ionisation state interstellar absorption lines in LARS 1 and LARS 13 indicative of outflowing neutral gas. Hence, for those two galaxies, together with the high-resolution HST imaging data, our IFS data provides further evidence for the relevance of localised outflows in shaping the observed Lyα morphology.

However, in LARS 3 the interpretation is already not as straightforwards. Here the broadest Hα lines do not occur co-spatial with the highest SFR density. Although also here the COS spectrum shows a bulk outflow of cold neutral gas (Paper V), the locally enhanced dispersion values seen in the PMAS maps appear not to be related to this outflow. Instead, it appears more naturally that the high turbulence within the ionised gas is not primarily driven by star formation activity, but is rather the result of the violent interaction with the north-western companion (see e.g. Teyssier et al. 2010 for theoretical support). The interpretation is further complicated by the fact that the HST imaging data resolves the local Lyα knot on smaller scales than which we are probing with our PMAS observations.

Nevertheless, there is another example among the LARS galaxies for Lyα escape being related to an outflow: LARS 5 (cf. paper VI). For this galaxy, we already presumed in Paper II the existence of a starburst-driven wind based solely on the filamentary structure seen in the HST Hα image. Our dispersion map now reveals that these filaments fill the interior of a biconical structure, with its base confined on the most prominent star-forming clump (see also Appendix A.5), which is fully in accordance with theoretical expectations for an evolved starburst-driven superwind (e.g. Cooper et al. 2008). Also, here Lyα photons could preferentially escape the disk through the cavity blown by the wind. The strongest Lyα enhancement is found directly above and below the main star-forming clump and the low surface brightness Lyα halo is then produced by those photons scattering on a bipolar shell-like structure of ambient neutral gas swept up by the superwind. Unfortunately, the brightest hot spots in Lyα above and below the plane are at the base of this outflowing cone and occur at scales that we cannot resolve in our PMAS data. Similar but less spectacular examples of elevated velocity dispersions above and below a disk can be seen in LARS 7 and LARS 11, with both galaxies also embedded in low surface brightness Lyα halos.

Another possible example for the importance of outflow kinematics in facilitating direct Lyα escape is the most luminous LAE in the sample: LARS 14 (see also Appendix A.14). Here the observed Hα profiles are always characterised by an underlying fainter broad component (see Fig. 3) that is believed to be directly related to outflowing material (e.g. Yang et al. 2015).

We conclude that while in some individual cases a causal connection between spatially resolved Hα kinematics and localised outflow scenarios might be conjectured, globally this is not a trend seen in our observations. Furthermore, Hα kinematics tell only one part of the whole story, and the suggested outflow scenarios should also be traceable by gas with a high degree of ionisation. At least for one galaxy with Lyα imaging similar to the LARS galaxies, such a connection has been demonstrated: ESO338-IG04. Recently, Bik et al. (2015) analysed observations of this galaxy obtained with the MUSE integral field spectrograph (Bacon et al. 2014). They show that the Lyα fuzz seen around the main star-forming knot of this galaxy (Hayes et al. 2005; Östlin et al. 2009) can be related to an outflow, which can be traced both with Hα kinematics and by a high degree of ionisation. In contrast to our observations, Bik et al. (2015) see the fast outflowing material in their vLOS map as significantly redshifted Hα emission. No similar prominent effect is apparent in our vLOS maps. Nevertheless, the vLOS fields of LARS 7 and LARS 12 display strongly localised redshifts in Hα that are spatially coincident with filamentary Hα fingers, hence, here we might also see a fast outflow pointed away from the observer. In addition, in those galaxies, no co-spatial relation between Lyα emissivity and the suspected outflows can be established.

6.2. Comparison of Hα to HI observations

thumbnail Fig. 8

Comparison of integrated H i linewidth W50 to FWHM of the Hα integrated velocity dispersion . The dashed line indicates the one-to-one relation. For LARS 6, (encircled point) we plot as W50, a preliminary result based upon VLA C-configuration interferometry, as the beam of the GBT profile (used to derive W50 in Paper III) is too broad to separate LARS 6 from a neighbouring galaxy.

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Radiative transfer of Lyα photons depends on the relative velocity differences between scattering H i atoms and Lyα sources. If the Lyα sources are out of resonance with the bulk of the neutral medium, they are less likely scattered, and in turn more likely to escape the galaxy. It is exactly this interplay between the ionised and neutral ISM phases that is determining the whole Lyα radiative transfer. In Paper III we studied LARS galaxies in the H i 21 cm line, using single-dish GBT and VLA D-configuration observations. We now attempt a comparison between the neutral and ionised gas kinematics in the LARS galaxies, cognisant of the fact that the spatial scales probed by both instruments are much larger than our PMAS H ii observations.

Generally, our GBT H i spectra have low S/N, and for the three most distant LARS galaxies, LARS 12, LARS 13, and LARS 14, we could not detect any significant signal at all. The profiles are mostly single or multiple peaked, but rarely show a classical double-horn profile that would be expected for a flat rotation curve. Hence, qualitatively our observed GBT H i line profiles are consistent with our PMAS results that most of the LARS galaxies are kinematically perturbed or sometimes even strongly interacting systems.

In Paper III we measured the width of the H i lines at 50% of the line peak from the GBT spectra. In Fig. 8 we compare this quantity, W50, to the FWHM of the integrated Hα velocity dispersion σtot (Sect. 5.2.4). Notably, two systems deviate significantly from the one-to-one relation: LARS 7 and LARS 10. LARS 10 shows the lowest S/N H i spectrum and moreover our PMAS FoV does not capture two smaller star-forming clumps in the south-east. Therefore, we believe that observational difficulties are the source of the σtotW50 difference in this galaxy. In LARS 7, however, we suspect the difference to be genuine. In this galaxy, the Hα morphology is significantly puffed up and rounder compared to the disk-like continuum (see also Appendix A.7). Therefore, we suspect that the smaller W50 measurement indicates that bulk of H i is in a kinematically more quiescent state then the ionised gas. This galaxy is one of the stronger LAEs in the sample ( and EWLyα = 40 Å). That considerable amounts of Lyα photons escape from LARS 7 was noted as peculiar in Paper V, since the metal absorption lines indicated there was a large amount of neutral gas sitting at the systemic velocity of the galaxy. Our observations now indicate that the intrinsic Lyα photons are produced in gas that is less quiescent than the scattering medium, which therefore is more transparent for a significant fraction of the intrinsic Lyα photons.

Spatially resolved VLA velocity fields are available for only a subset of five LARS galaxies (LARS 2, LARS 3, LARS 4, LARS 8, and LARS 9). They represent rotations disturbed by interactions with neighbours. In four of them, H i kinematical axes have similar orientations as those of the PMAS Hα velocity field. In the fifth object, the complex interacting system LARS 9, the Hα and H i velocity fields show different characteristics, but the complexities seen in the PMAS maps of this galaxy are on scales far beyond the spatial resolving power of the VLA D configuration (see also Appendix A.9). However, some of the LARS galaxies have already been observed with the VLA in C and B configuration and the analysis is currently in progress. For the first time, these data will allow a comparison between Hα, H i and Lyα on meaningful physical scales. It is evident that these comparisons will provide a critical benchmark for our understanding of Lyα radiative transfer in interstellar and circum-galactic environments.

6.3. Relations between kinematical properties and galaxy parameters

thumbnail Fig. 9

Global Hα kinematical parameters vshear (left panel), σ0 (middle panel), and vshear/σ0 (right panel) in comparison to stellar mass for LARS galaxies (from Paper II) and in comparison to literature values: DYNAMO z ~ 0.1 [compact] perturbed rotators from Green et al. (2014) as [small] green circles; DYNAMO z ~ 0.1 [compact] complex kinematics from Green et al. (2014) as [small] green squares; Local Lyman Break Analogues from Gonçalves et al. (2010) as blue circles; Keck/OSIRIS resolved z ~ 2−3 star-forming galaxies from Law et al. (2009) as red circles; SINS z ~ 2−3 galaxies from Förster Schreiber et al. (2009) as orange squares (only in the left panel). Uncertainties given where available. The LARS galaxies are represented by symbols according to the legend in the left panel. Spearman rank correlation coefficients ρs and corresponding p0 values for the LARS galaxies are shown in each panel.

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thumbnail Fig. 10

Global Hα kinematical parameters vshear (left panel), σ0 (middle panel), and vshear/σ0 (right panel) in comparison to SFR for LARS galaxies (from Paper II) and in comparison to literature values (same symbols as in Fig. 9). Uncertainties given where available. Spearman rank correlation coefficients ρs and corresponding p0 values for the LARS galaxies are shown in each panel.

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In Sect. 5.2 we quantified the global kinematical properties of the LARS galaxies using the non-parametric estimators vshear, σ0 and vshear/σ0. Before linking these observables to global Lyα properties of the LARS galaxies (cf. Sect. 6.4), we need to understand which galaxy parameters are encoded in them.

We find strong correlations between stellar mass M and vshear, as well as SFR and σ0 (M and SFR from Paper II). Graphically we show these correlations in Fig. 9 (left panel) and Fig. 10 (centre panel). The Spearman rank correlation coefficients (e.g. Wall 1996) are ρs = 0.763 for the M-vshear relation and ρs = 0.829 for the SFR-σ0 relation. This corresponds to likelihoods of the null hypothesis that no monotonic relation exists between the two parameters of p0 = 0.02% and p0 = 0.3% (two-tailed test11) for the SFR-σ0 and M-vshear relation, respectively. We discuss these two relations in more detail in Sect. 6.3.1 and Sect. 6.3.2, where we also introduce the comparison samples shown in Fig. 9 and Fig. 10.

Besides this tight correlation between SFR and σ0, there is also a weaker correlation between SFR and vshear in our sample (ρs = 0.775, p0 = 0.1%). We show the data in Fig. 10 (left panel). While not shown graphically, the DYNAMO disks would scatter over the whole SFR-vshear plane, also filling the upper left corner in this diagram. Finally, in Fig. 10 (right panel) we find that vshear/σ0 is not significantly correlated with the SFR in LARS (ρs = 0.507, p0 = 6%).

We also check in Fig. 9 (centre panel) for a M-σ0 correlation, but with ρs = 0.362 the null hypothesis that the variables are uncorrelated cannot be rejected (p0 = 20%). Similar low correlation-coefficients are found for the comparison samples in Fig. 9 (centre panel). Since there is likely a monotonic relation between M-vshear and M-σ0 are uncorrelated, the monotonic relation M-vshear/σ0 (ρs = 0.723, p0 = 0.3%) – Fig. 9 (right panel) – is expected.

From these results, we conclude that dispersion-dominated galaxies in our sample are preferentially low-mass systems with M ≲ 1010M. This result is also commonly found in samples of high-z, star-forming galaxies (Law et al. 2009; Förster Schreiber et al. 2009; Newman et al. 2013).

6.3.1. SFR-σ0 correlation

The highly significant correlation between σ0 and SFR has long been established for giant H ii regions (Terlevich & Melnick 1981). Recently, it has been shown that it extends over a large dynamical range in star formation and mass, not only locally but also at high redshifts (Green et al. 2010, 2014). The physical nature of the σ0-SFR relation might be that star formation feedback powers turbulence in the interstellar medium. On the other hand, the processes that lead to a high SFR might also be responsible for producing a high σ0. In particular, inflows of cold gas that feed the star formation processes are expected to stir up the interstellar medium and thus lead to turbulent flows (e.g. Wisnioski et al. 2015, and references therein).

Graphically we compare, in Fig. 10 (centre panel), the LARS SFR-σ0 points to the values from the DYNAMO galaxies (Green et al. 2014) with complex kinematics and the DYNAMO perturbed rotators. To put this result in context with high-z studies, in Fig. 10 we also show the SFR-σ0 points from the Keck/OSIRIS z ~ 2−3 star-forming galaxies by Law et al. (2009), and the local Lyman break analogues by Gonçalves et al. (2010). An exhaustive compilation of SFR-σ0 measurements is presented in Green et al. (2014), and the LARS SFR-σ0 points do not deviate from this relation.

6.3.2. M-vshear correlation

Given the complexity of the ionised gas velocity fields seen in the LARS galaxies, a tight relation between our measured, inclination-uncorrected vshear values with stellar mass appears surprising. It indicates that, at least in a statistical sense, vshear is tracing systemic rotation in our systems and that the scatter in our relation is dominated by the unknown inclination correction (see also Law et al. 2009).

To put our data in context with other studies, we compare our M-vshear data points in Fig. 9 (left panel) to the Green et al. (2014) DYNAMO sample and to the Gonçalves et al. (2010) local Lyman break analogues. Our high-z comparison samples are the Keck/OSIRIS z ~ 2−3 star-forming galaxies Law et al. and the z ~ 1−3 SINS sample by Förster Schreiber et al. (2009). For the rotation-dominated and perturbed rotators in the DYNAMO sample, Green et al. tabulate rotation velocity at 2.2 disk scale lengths obtained from fitting model disks to their velocity fields. We convert these to an inclination-uncorrected value via multiplication with sini. Again, for the DYNAMO sample we only compare to their objects with complex kinematics or their perturbed rotators, as they are dominant in our sample.

It is apparent from Fig. 9 (left panel) that while our data points line up well with the z ~ 0.1 galaxies, a significant number of high-z galaxies shows lower vshear values at given stellar mass in the range 1010M−1011M. The reason for this is that high-z studies are not sensitive enough to reach the outer faint isophotes, hence, they are biased towards lower vshear values (see Sect. 5.2.1). Indeed, Law et al. (2009) report a detection limit of ~1  M yr-1 kpc-2, while Förster Schreiber et al. (2009) report 0.03M yr-1kpc-2 as an average for their sample, which is comparable to our depth (Sect. 5.1).

6.4. Relations between global kinematical properties and Lyα observables

thumbnail Fig. 11

Relations between global Lyα properties of the LARS galaxies to global kinematical parameters vshear, σ0 and vshear/σ0.

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We now explore trends between global kinematical properties derived from the ionised gas in the LARS galaxies and their Lyα observables determined in Paper II, namely Lyα escape fraction , ratio of Lyα to Hα flux Lyα/ Hα, and Lyα equivalent width EWLyα. For reference, we list these quantities here again in Table 2. We recall that Lyα/Hα is the observed flux ratio, while fesc is determined from the intrinsic luminosities, i.e. after correcting the fluxes for dust reddening.

Regarding the qualitative classification of the vLOS maps in Sect. 5.1 into rotating disks, perturbed rotators and objects showing complex kinematics there is no preference in any of the globally integrated Lyα observables. Both the maximum and minimum of these observables occur in the complex kinematics class. Therefore, just the qualitative appearance of the velocity field seems not to predict whether the galaxy is a LAE or not.

In the previous section, we showed that within the LARS sample higher SFRs are found in galaxies that have higher σ0 and higher vshear measurements and that galaxies of higher mass also show higher vshear values and higher vshear/σ0 ratios (Figs. 9 and 10). We now compare our vshear, σ0 and vshear/σ0-ratios to the aperture integrated Lyα observables EWLyα, Lyα/Hα and from Paper II. We do this in form of a graphical 3 × 3 matrix in Fig. 11. In each panel, we include the Spearman rank correlation coefficient ρs and the likelihood p0 to reject the null hypothesis.

From the centre row in Fig. 11 it is obvious that none of the Lyα observables correlates with the averaged intrinsic velocity dispersion σ0. As σ0 correlates positively with SFR, this signifies that the observed Lyα emission is a bad SFR calibrator. In Fig. 11 it is also evident that galaxies with higher shearing velocities (vshear ≳ 50 km s-1) have preferentially lower EWLyα, lower Lyα/Hα, and lower . Therefore, according to the above presented M-vshear relation (Sect. 6.3.2) LAEs are preferentially found among the systems with M ≲ 1010M in LARS. This deficiency of strong LAEs among high-mass systems was already noted in Paper II. Here we see this trend from a kinematical perspective now. Also, a low vshear value, although a necessary condition, seems not to be sufficient to have significant amounts Lyα photons escaping (e.g. LARS 6). Again, this shows that Lyα escape from galaxies is a complex multi-parametric problem.

thumbnail Fig. 12

Relations between ξLyα, the “relative Petrosian extension of Lyα” as defined in Hayes et al. (2013), and global kinematical parameters vshear, σ0 and vshear/σ0 with symbols according to the legend in Fig. 9. For galaxies with no Lyα emission (LARS 4 and LARS 6, circled symbols) ξLyα is defined as zero and for LARS 9 the measured ξLyα presents a lower limit (see also Hayes et al. 2013). Spearman rank correlation coefficients ρs and corresponding p0 values are calculated excluding LARS 4 and LARS 6.

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Although the LARS sample is small, the result that seven of eight non-LAEs have vshear/σ0> 1 and four of six LAEs have vshear/σ0< 1 signals that dispersion-dominated kinematics are an important ingredient in Lyα escape. Again, lower vshear/σ0 ratios are found in lower M objects in our sample and σ0 is uncorrelated with M. Therefore, the correlation between Lyα observables and vshear/σ0 is a consequence of the correlation between Lyα observables and M. Nevertheless, low vshear/σ0 ratios also state that the ionised gas in those galaxies must be in a turbulent state. High SFR appears to be connected to an increase turbulence, but it is currently not clear whether the processes that cause star formation or feedback from star formation are responsible for the increased turbulence (Sect. 6.3.1). Regardless of the causal relationship between SFR and σ0, our results support that Lyα escape is being favoured in low-mass systems undergoing an intense star formation episode. Similarly Cowie et al. (2010) found that in a sample of UV bright z ~ 0.3 galaxies, LAEs are primarily the young galaxies that have recently become strongly star forming. In the local Universe dispersion-dominated systems with vshear/σ0< 1 are rare, but they become much more prevalent at higher redshifts (Wisnioski et al. 2015). Coincidentally, the number density of LAEs rises towards higher redshifts (Wold et al. 2014). Therefore we speculate, that dispersion-dominated kinematics are indeed a necessary requirement for a galaxy to have a significant amount of Lyα photons escaping.

6.5. Lyα extension and Hα kinematics

All of the LARS LAEs show a significantly more extended Lyα morphology compared to their appearance in Hα or UV continuum. These large-scale Lyα haloes appear to completely encompass the star-forming regions. LARS 1, LARS 2, LARS 5, LARS 7, LARS 12 and LARS 14 are the most obvious examples of extended Lyα emission, but the phenomenon is visible in all our objects, even for those galaxies that show Lyα in absorption (Figs. 57; cf. Hayes et al. 2013 and Paper II). At high redshift the ubiquity of extended Lyα haloes around LAEs was recently revealed by Wisotzki et al. (2015) on an individual object-by-object basis. However, in contrast to the LARS Lyα haloes, the high-z haloes appear to have ~10× larger extents at a given continuum radius (Wisotzki et al. 2015, their Fig. 12). In order to quantify the spatial extent of observed relative to intrinsic Lyα emission in Hayes et al. (2013) we defined the “Relative Petrosian Extension” ξLyα as the ratio of the Petrosian radii (Petrosian 1976) at η = 20% measured in Lyα and Hα: . For reference, we list the ξLyα values of the LARS galaxies here again in Table 2. Based on an anti-correlation between ξLyα and UV slope we conjectured that smaller Lyα haloes occur in galaxies that have converted more of their circum-galactic neutral gas into forming stars and subsequently dust (Hayes et al. 2013). In such a scenario, the larger extent of high-z Lyα haloes could be related to the circum-galactic gas-reservoirs being larger in the early universe.

In Fig. 12 we show that there are no significant correlations between ξLyα and the global kinematical Hα parameters vshear, σ0 and vshear/σ0. Therefore, we reason that the kinematics of the interstellar medium do not strongly influence the appearance of the haloes and that the Lyα halo phenomenon is only related to the presence of a full gas reservoir. Further, 21 cm HI imaging of the LARS galaxies at high spatial resolution is needed to test this scenario.

7. Summary and conclusions

We obtained the following results from our integral field spectroscopic observations of the Hα line in the LARS galaxies:

  • 1.

    Half of the LARS galaxies show complex Hα kinematics. There are kinematical properties consistent with a rotating disk in only two galaxies and in five a disturbed rotational signature is apparent. With respect to Lyα escape, we find no preference of high EWLyα or high values towards any of those classes, but the minimum and maximum values both occur in objects showing complex kinematics in our sample.

  • 2.

    A common feature in all LARS galaxies are high Hα velocity dispersions. With vFWHM ≳ 100 km s-1 our measurements are in contrast to values typically seen in local spirals, but in high-z star-forming galaxies such high values appear to be the norm.

  • 3.

    While we could not infer a direct relation between spatially resolved kinematics of the ionised gas and photometric Lyα properties for all LARS galaxies, in individual cases our maps appear qualitatively consistent with outflow scenarios that promote Lyα escape from high-density regions.

  • 4.

    Currently, a spatially resolved comparison of our H ii velocity fields to our H i data is severely limited since the scales resolved by the radio observations are significantly larger. However, for one galaxy (LARS 7) the difference between globally integrated velocity dispersion of ionised and neutral gas offers a viable explanation for the escape of significant amounts of Lyα photons.

  • 5.

    From our Hα velocity maps, we derive the non-parametric statistics vshear, σ0 and vshear/σ0 to quantify the kinematics of the LARS galaxies globally. Our vshear values range from 30 km s-1 to 180 km s-1 and our σ0 values range from 40 km s-1 to 100 km s-1. For our ratios vshear/σ0, we find a median of 1.4, and five of the LARS galaxies are dispersion-dominated systems with vshear/σ0< 1.

  • 6.

    A positively correlated σ0 with SFR in the LARS galaxies is fully consistent with other IFS studies. We also find strong correlations between M and vshear, M and vshear/σ0, and SFR and vshear. In view of the M-vshear correlation the SFR-vshear correlation implies that more massive galaxies have higher overall star formation rates in our sample.

  • 7.

    The Lyα properties EWLyα, Lyα/Hα and do not correlate with σ0, but they correlate with vshear and vshear/σ0 (Fig. 11). We find no correlation between the global kinematical statistics and the extent of the Lyα halo.

  • 8.

    Four of six LARS LAEs are dispersion-dominated systems with vshear/σ0< 1 and 7 of 8 non-LAEs have vshear/σ0> 1.

Observational studies of Lyα emission in local-Universe galaxies have so far focused on imaging and UV spectroscopy (for a recent review see Hayes 2015). For the first time, we provided empirical results from IFS observations for a sample of galaxies with known Lyα observables. In our pioneering study, we focused on the spectral and spatial properties of the intrinsic Lyα radiation field as traced by Hα. We found a direct relation between the global non-parametric kinematical statistics of the ionised gas and the Lyα observables and EWLyα, and our main result is that dispersion-dominated systems favour Lyα escape. The prevalence of LAEs among dispersion-dominated galaxies could be simply a consequence of these systems being the lower mass systems in our sample, which is a result already found in Paper II. However, the observed turbulence in actively star-forming systems should be related to ISM conditions that ease Lyα radiative transfer out of high-density environments. In particular, if turbulence is a direct consequence of star formation, then the energetic input from the star formation episode might also be powerful enough to drive cavities through the neutral medium into the lower density circum-galactic environments. Of course, the kinematics of the ionised gas offer only a limited view of the processes at play, and in future studies we will attempt to connect our kinematic measurements to spatial mappings of the ISMs ionisation state. The synergy between IFS data, space-based UV imaging, and high-resolution H i observations of nearby star-forming galaxies will be vital to build a coherent observational picture of Lyα radiative transport in galaxies.


1

We adopt the convention established in high-z narrowband surveys of designating galaxies with EWLyα ≥ 20 Å, LAEs, and galaxies with EWLyα< 20 Å, non-LAEs.

2

The naming of the mode refers to the instruments internal magnification of the telescopes focal plane; doubling the magnification of the focal plane doubles the extent of the FoV.

3

Values taken from the PMAS online grating tables, available at http://www.caha.es/pmas/PMAS_COOKBOOK/TABLES/pmas_gratings.html#4K_1200_1BW

5

As the amount of raw data from the observations was substantial, we greatly benefited from the scripting capabilites of p3d (Sandin et al. 2011). Our shell scripts and example parameter files can be found at https://github.com/Knusper/pmas_data_red

9

This effect is similar to beam smearing in radio interferometric imaging observations.

10

For LARS 13, Gonçalves et al. (2010) do not sample the entire galaxy in their observations; see Sect. A.13.

11

We consider correlations as significant when the likelihood of the null hypothesis, p0, is smaller than 5%.

Acknowledgments

E.C.H. especially thanks Sebastian Kamann and Bernd Husemann for teaching him how to operate the PMAS instrument. We thank the support staff at Calar Alto observatory for help with the visitor-mode observations. All plots in this paper were created using matplotlib (Hunter 2007). Intensity related images use the cubhelix colour scheme by Green (2011). This research made extensive use of the astropy pacakge (Astropy Collaboration et al. 2013). M.H. acknowledges the support of the Swedish Research Council, Vetenskapsrådet, and the Swedish National Space Board (SNSB) and is Academy Fellow of the Knut and Alice Wallenberg Foundation. HOF is currently granted by a Cátedra CONACyT para Jóvenes Investigadores. I.O. has been supported by the Czech Science Foundation grant GACR 14-20666P. D.K. is funded by the Centre National d’Études Spatiales (CNES). F.D. is grateful for financial support from the Japan Society for the Promotion of Science (JSPS) fund. P.L. acknowledges support from the ERC-StG grant EGGS-278202.

References

Appendix A: Notes on individual objects

In the following, we detail the observed Hα velocity fields for each galaxy. We compare our maps to the photometric Lyα properties derived from the HST images from Paper II and H i observations from Paper III (see Sect. 4).

Appendix A.1: LARS 1 (Mrk 259)

With LLyα = 8 × 1041 erg s-1 and EWLyα = 33 Å LARS 1 is a strong Lyα emitting galaxy. A detailed description of the photometric properties of this galaxy was presented in Paper I. If LARS 1 were at high-z, it would easily be selected in conventional narrowband imaging surveys (Paper IV). The galaxy shows a highly irregular morphology. Its main feature is UV bright complex in the north-east that harbours the youngest stellar population. As already noted in Paper II a filamentary structure emanating from the north-eastern knot is seen in Hα. Towards the south-east, numerous smaller star-forming complexes are found that blend in with an older stellar population.

In contrast with the irregular appearance, the line-of-sight velocity field of LARS 1 is rather symmetric. The velocity field is consistent with a rotating galaxy. The kinematical centre is close to centre of the PMAS FoV and the kinematical axis appears to run from the north-west to the south-east. We measure vshear = 56 ± 1 km s-1. The GBT single dish H i spectrum of this source is reminiscent of a classic double-horn profile, also an obvious sign of rotation, with a peak separation consistent with our vshear measurement.

The highest velocity dispersions (vFWHM ≈ 150 km s-1) are found in the north-eastern region. Here LARS 1 also shines strong in Lyα, but while a fraction of Lyα appears to escape directly towards us, a more extended Lyα halo around this part is indicative of resonant scatterings in the circum-galactic gas (see also Paper I). In constrast, in the south-western part of the galaxy, where we observe the lowest velocity dispersions (vFWHM ≈ 70 km s-1), Lyα photons do not escape along the line of sight.

Appendix A.2: LARS 2 (Shoc 240)

Anywhere in LARS 2 where Hα photons are produced, Lyα photons emerge along the line of sight. LARS 2 is the galaxy with the highest global escape fraction of Lyα photons (%) and the highest Lyα/Hα ratio (Lyα/Hα = 4.53).

With vshear = 23 ± 2 km s-1, LARS 2 shows the smallest vshear in our sample. However, we consider this value as a lower limit since we missed in our pointing the southernmost star-forming knot. Our observed velocity field appears to be disturbed, but we could envision a kinematical axis orthogonal to the photometric major axis, i.e. roughly from west to east. This idea is supported by our VLA imaging of this source (see Fig. 7 in Paper III). The H i velocity field also indicates vshear ≈ 30 km s-1, meaning that our incomplete measurement gives a sensible lower limit. Within the observed region, our velocity dispersion map is rather uniform, with vVFWHM ≈ 100 km s-1.

Appendix A.3: LARS 3 (Arp 238)

LARS 3 is the south-eastern nucleus of the violently interacting pair of similar sized spiral galaxies Arp 238. With a global and LLyα = 1041 erg s-1, this dust-rich, luminous infrared galaxy is a relatively weak Lyα emitter. Imaging by VLA H i reveals an extended tail towards the west. This tidal tail is much larger than the optical dimensions of the pair Arp 238 (see also Cannon et al. 2004, for similar extended tidal H i structures around the Lyα emitting star bursts Tol 1924-416 and IRAS08339+6517).

In Hα the main kinematical axis runs from west to east and the radial velocity field appears symmetric, although slightly disturbed towards the north and the south. We measure vshear ≈ 140 km s-1, a value that is in the domain of typical maximum velocities of inclination corrected Hα rotation curves of spiral galaxies (e.g. Epinat et al. 2008a, 2010; Erroz-Ferrer et al. 2015). With vFWHM ≳ 300 km s-1 highest velocity dispersions are observed in the western part. The largest Lyα surface brightness is also observed in the western part of the nucleus. Lyα appears in absorption in the eastern region, where we also see a minimum in velocity dispersions with vFWHM ≈ 70 km s-1.

Appendix A.4: LARS 4 (SDSS J130728.45+542652.3)

Although LARS 4 is similar to LARS 1 in terms of dust content and star formation rate, globally this galaxy shows Lyα in absorption. The galaxy can be photometrically decomposed into two main components: an elongated lower surface brightness structure in the west and a more puffed up and luminous companion in the east. The eastern structure is tilted at 40° with respect to the western one.

Compared to the highly irregular morphology in UV and Hα, the radial velocity field appears rather regular, with a moderate amplitude of vshear ≈ 75 km s-1 along a well-defined axis from west to east. The kinematic centre appears to be right between the two photometric components, indicating that the observed shearing is the velocity difference between the merging components and not a consequence of rotation. The lack of a well-defined simple and organised disk is further supported by the absence of a double-horn profile in the GBT single-dish H i profile. Nevertheless, higher sensitivity VLA imaging results show a coherent velocity field on larger scales with an amplitude comparable to vshear (Paper III, Fig. 9).

In the dispersion map, the two components are clearly distinguishable, with the eastern component showing higher velocity dispersions (vFWHM ≈ 100 km s-1) than the western (vFWHM ≈ 65 km s-1). In both regions, however, Lyα is seen in absorption. The highest velocity dispersions are observed at the boundary region where the two components are separated photometrically, but here only a little Lyα is escaping.

Appendix A.5: LARS 5 (Mrk 1486)

In the HST images LARS 5 appears as a small (i.e. projected diameter d ≈ 5 kpc) highly inclined edge-on disk. Within the apparent disk Lyα appears in absorption but the galaxy shows an extended halo, which is azimuthally symmetric at low surface brightness isophotes, while brighter isophotes resemble more the elongated Hα shape. Most prominent in the Hα image are filamentary finger-like structures extending below and above the disk, reminiscent of an outflowing wind.

Although the profile of our single-dish H i observations shows multiple peaks close to the noise level that might correspond to the peaks of a faint double-horn profile (Paper III), our Hα kinematics appear incompatible with a typical disk scenario: Firstly, our measured vshear = 37 km s-1 would indicate a rotation curve with a very low amplitude, which is untypical even for a small disk (e.g. in the largest Hα disk sample of Epinat et al. 2010, for d ≤ 5 kpc the maximum rotation curve velocity is on average 95 km s-1). Secondly, there is apparent asymmetry in the spatial distribution of the vLOS values, i.e. a large sector in the south-west is characterised by similar line-of-sight velocities (vLOS ~ + 20 km s-1), while only a small sector in the north-east shows blueshifted Hα emission (vLOS ~ −40 km s-1).

The most prominent feature in the velocity dispersion map is a biconical zone of increasing velocity dispersions (from ~120 km s-1 to ~220 km s-1) with increasing distance from the centre. The base of this zone coincides the brightest region in UV and Hα in the south-western sector. We emphasise that the seeing PSF FWHM for this observation is 1.3′′, thus ~2× the extent of the 0.5′′×0.5′′ spaxels used on LARS 5. However, as the kinematical centre is not co-spatial with the base of the cones, and since the velocity gradient around the base of the cone is very weak we are confident that this feature is real and not caused by PSF smearing effects.

Appendix A.6: LARS 6 (KISSR 2019)

With 1 M yr-1 conversion of gas into stars, LARS 6 shows the lowest SFR in the sample (Paper II). The main star-forming knot is in the north with a tail of much smaller and fewer luminous knots extending to the south. In our seeing limited data cubes we cannot disentangle these individual knots photometrically. Lyα is seen in absorption, even on the smallest scales.

Shearing is observed between the main component and the tail, although the amplitude is moderate (vshear = 52 km s-1). The main component also shows higher velocity dispersions (vVFWHM ≈ 70 km s-1) than the tail (vVFWHM ≈ 50 km s-1). Overall this galaxy has the lowest observed velocity dispersion in the sample.

Our GBT single-dish H i measurements are severely contaminated by the nearby field spiral UGC 10028. However, newly obtained but as of yet unpublished VLA D-configuration images allow a first-order separation from LARS 6 and this companion. From these data, coherent rotation is present in the H i gas associated with LARS 6 at a level roughly consistent with the vshear estimate we obtain from PMAS.

Appendix A.7: LARS 7 (IRAS F13136+2938)

In the continuum LARS 7 resembles a highly inclined disk comparable to LARS 5, but in Hα an almost azimuthally symmetric structure emerges that is highly distended with respect to the elongated continuum morphology. Moreover, two extended low surface brightness red lobes are found at the opposite ends of the inclined disk, reminiscent of a shell-like structure. This is suggestive of a recent merger event (e.g. Bettoni et al. 2011). In Lyα images LARS 7 appears even more extended, with the bright isophotes following the Hα shape and low surface brightness isophotes resembling a more scaled up version of the apparent disk.

For similar reasons as outlined for LARS 5 in Sect. A.5, our Hα kinematics argue against a typical disk scenario: we observe a low shearing amplitude; with vshear = 31 km s-1 even lower than in LARS 5. Moreover, the line of sight velocity maps appears disturbed compared to that expected for a classical disk. Our GBT single dish H i observations reveal a single broad (92 km s-1) line. LARS 7 is the only object where the GBT linewidth is incompatible to its integrated Hα linewidth (cf. Sect. 6.2). A main kinematical axis can be envisioned to run from north-east to south-west along the continuum major axis, but in the north-west and south-east the vLOS values do not follow this weak gradient at all. Overall the galaxy shows high velocity dispersion in Hα (vFWHM ≳ 160 km s-1), with the lowest values occurring in north-east (vFWHM ≈ 120 km s-1), where the brightest fluxes in Lyα and the highest Lyα/Hα ratios are observed.

Appendix A.8: LARS 8 (SDSS-J125013.50+073441.5)

LARS 8 appears as a face-on disk with the highest metalicity of the sample. The apparent disk also possesses a highly dust obscured nucleus. Nevertheless, there is a high degree of irregularity compared to classical disks and spiral arms are not well defined. As traces of shell-like structures are visible in the inner parts and in the outskirts of the galaxy (cf. Fig. 6 in Paper I), LARS 8 could be classified as a shell system hinting at a recent merger event (e.g. Bettoni et al. 2011). The Lyα light distribution of LARS 8 does not resemble that seen in Hα. The brightest Lyα zone is in the north of the disk, while in the south Lyα appears only in absorption. At lower surface brightness isophotes a Lyα halo becomes visible. With an equivalent width EWLyα = 20.3 Å this galaxy would be selected as LAE in conventional narrowband surveys.

Our vLOS map seems disk-like. Assuming an infinitely thin disk the ellipticity of 0.2 (Paper IV) implies an inclination of 40°, hence, our observed vshear = 155 km s-1 translates to vmax = 241 km s-1. The GBT single-dish H i profile shows a broad, possibly double-peaked profile. Although these peaks are not significantly separated from the overall H i signal, the implied velocity difference of ~300 km s-1 appears consistent with our vshear measurement. The orientation of the velocity field from VLA interferometric H i observations is qualitatively consistent with our PMAS Hα observations, although at the VLA D-configuration beam size of 72′′ LARS 8 appears only marginally resolved.

Elevated velocity dispersions with vFWHM ≳ 160 km s-1 are apparent to extend orthogonally to the kinematical axis along the 0 km s-1 iso vLOS contour. In the other regions, the vFWHM map is rather flat, typically with vFWHM ~ 100 km s-1 – a value that is also still commonly observed within the sample of 153 local spirals by Epinat et al. (2010). Given the strong gradient in the velocity field, the observed elevated velocity dispersions are likely a result of PSF smearing effects.

Appendix A.9: LARS 9 (IRAS 08208+2816)

thumbnail Fig. A.1

Representative LARS 9 Hα line profiles in blue hatched region of Fig. 6 described by a fit using two Gaussian components. The red dashed lines show the individual components and the blue line shows the sum, while the black line shows the profile as observed. For all profiles shown the single component fit used to create the map shown in Fig. 6 converged on the stronger red component.

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thumbnail Fig. A.2

Representative LARS 9 Hα line profiles in red hatched region of Fig. 6, similar to Fig. A.1. The single component fit used to create the map shown in Fig. 6 converged on the stronger blue component in the centre panel, but for the profiles shown in the left and right panels the single component fit is artificially broadened.

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thumbnail Fig. A.3

Representative LARS 13 Hα line profiles in blue hatched region of Fig. 7, similar to Fig. A.1. The single component fit used to create the map shown in Fig. 7 converged on the stronger blue component in the right panel, but for the profiles shown in the left and centre panels the single component fit is artificially broadened.

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This luminous infrared galaxy has highly irregular morphology. Numerous star-forming knots are visible in Hα along two arms of large extend that are connected to a central, very bright Hα nucleus. At the end of the southern tail, a foreground star appears in projection; contributions from this star have been masked out in the PMAS data. In LARS 9 Lyα is absorbed almost everywhere along the line of sight towards the star-forming regions. Nevertheless, this galaxy is embedded in a faint extended Lyα fuzz. Morphologically, this fuzz broadly traces a scaled up version of its optical and Hα shape. Having a globally integrated Lyα luminosity of LLyα ≈ 3 × 1041 erg s-1 and an equivalent width of EWLyα ≈ 8 Å, this galaxy would not be selected by its Lyα emission at high-z in conventional narrowband surveys.

Since LARS 9 extends more than ~0.5on the sky, we needed to cover it with two PMAS 16′′×16′′ pointings (Fig. 6). The line-of-sight velocity field for this galaxy is very peculiar. From the north to the centre, a weak (~100 km s-1) gradient from blueshifted to systemic velocity is apparent. From the centre this weak gradient continues towards the south. The southern tail then shows an opposite gradient from red- to blueshifts. In this south- and south-western zone, a single Gaussian often is not an optimal representation of the observed Hα lines. In this zone the spectral profile is sometimes asymmetric with an extended red or blue wing, but often it also shows clearly double-peaked morphology (for examples see Fig. A.1). In some of these regions, our fit tries to capture both lines, hence, the obtained line-of-sight velocity is centred between the peaks and the linewidth appears very broad (e.g. left and right panels of Fig. A.2). In some other spaxels, when the secondary peak is very weak or when only an extended wing is seen, the fit converges to the stronger line. The affected zones have hatched rectangles overlaid in Fig. 6. These zones harbour a kinematical distinct secondary component. This secondary component does not follow the large-scale motions of the northern component, to which the nucleus also belongs. We indicate, with red and blue hatchings in Fig. 6, the regions of this component that are red- and blueshifted with respect to the systemic velocity (as given by the nucleus). As a natural outcome from this qualitative analysis the emission in south-eastern tail of LARS 9 is solely coming from this secondary component. Also, a significant fraction of Lyα photons appear to escape towards the observer only at the end of this tail.

From our PMAS observation we conclude that LARS 9 is a closely interacting pair of galaxies in an advanced stage of merging. The interaction scenario is also supported by our 21 cm observations. The integrated GBT spectrum shows a broad single line, indicating that the bulk of the H i is not partaking in an ordered flat rotation. LARS 9 was only marginally resolved in our VLA H i maps (Paper III). However, as of yet unpublished VLA C configuration observations (K. Fitzgibbon, in prep.) show extended H i towards the west, enclosing the galaxy SDSS J082353.65+280622.2. For this galaxy, no spectroscopic redshift is available, but the photometric redshift agrees with being associated to LARS 9. These observations therefore strongly suggest that a third system is significantly involved in the interaction. Moreover, the VLA C-configuration observations of LARS 9 show a peak in the second-moment maps that trace the random motions of H i that coincides spatially with the zones of multiple H ii components in our PMAS maps. Hence, at these locations (hatched regions in Fig. 6) Lyα photons of both distinct kinematical components are likely scattered by H i at resonance.

Appendix A.10: LARS 10 (Mrk 0061)

Similar to LARS 1 this galaxy appears morphologically to be in an advanced merger state. It possesses a large UV bright core in the north-west and a spur of smaller, less luminous star-forming regions towards the south-east. Several redder low surface brightness structures are seen outside the main body of the galaxy, reminiscent of the appearance of shell galaxies (e.g. Marino et al. 2009; Bettoni et al. 2011). From the central star-forming parts Lyα is only seen in absorption, while a faint halo emerges at larger radii. When considering solely the central parts the galaxy would remain undetected in high-z LAE surveys since EWLyα = 8 Å. However, when integrating over the lower surface brightness emission EWLyα rises to 31 Å and with its luminosity of LLyα = 2 × 1041erg s-1 the galaxy would be within the sensitivity of the deepest contemporary LAE surveys (Rauch et al. 2008; Bacon et al. 2015).

The line-of-sight velocity field is symmetric and consistent with rotation and contrasts the irregular continuum morphology. The velocity gradient running from the south-east to the north-west is weak and we measure vshear = 36 km s-1. The seeing for this observation was very substantial (1.5′′ FWHM, i.e 3× the size of the 0.5′′×0.5′′ spaxels). Despite the weak gradient, this leads to non-negligible PSF smearing effects in the dispersion map. Moreover, because of the short exposure time and the rather low Hα flux, this galaxy has the lowest S/N per spaxel of the whole sample; this manifests in a noisy vFWHM map. Both of these effects essentially make local disturbances in the velocity dispersion untraceable in our LARS 10 data set, but our flux weighted global measurement of σ0 ≈ 40 km s-1 is robust against these nuisances.

The GBT integrated H i spectrum shows a broad single line profile (~280 km s-1 FWHM), however, at low signal to noise. This appears hard to reconcile with the Hα results. If real, it might indicate that a large fraction of neutral gas in and around LARS 10 is kinematically in a different state than the gas around the galaxy’s star-forming regions.

Appendix A.11: LARS 11 (SDSS J140347.22+062812.1)

This galaxy appears as a highly inclined edge-on disk in the continuum and UV that is slightly thicker when seen in Hα. According to the Hα and UV emission, stronger star formation occurs in the south-eastern zone of the projected disk. In Lyα a mildly extended halo above and below the plane is visible, with the isophotal contours approximately preserving the axis ratio of Hα. Within the disk Lyα occurs exclusively in absorption.

Running along the disk from the north-west to the south-east a strong gradient in the vLOS map is apparent. The observed shearing amplitude vshear = 150 km s-1 is consistent with this gradient being caused by rotation (e.g. Epinat et al. 2008a, 2010; Erroz-Ferrer et al. 2015). Unfortunately the beam of our GBT single-dish H i observations is likely contaminated by other sources. Nevertheless, within the multiple peaks in the GBT spectrum a double-horn profile at a velocity separation consistent with our Hαvshear measurement is visible. Although the projected height of the disk is similar to the PSF FWHM, the dispersion map shows traces of higher velocity dispersions above and below the disk (vVFWHM ≈ 200 km s-1) than within (vVFWHM ≈ 150 km s-1), especially around the star-forming regions in the south-east. However, the elevated dispersions near the kinematic centre are caused by PSF smearing of the strong gradient in the vLOS field.

Appendix A.12: LARS 12 (LEDA 27453)

Because of its modest EWLyα = 13 Å, this UV bright merger would not be selected as a LAE at high-z. At its brightest knot in UV and Hα the galaxy shows Lyα only in absorption. Lyα only appears in emission at larger radii, where a number of fainter star-forming regions can be appreciated. Moreover, LARS 12 is embedded in a faint, low surface brightness Lyα halo.

The non-regular Hα velocity field indicates complex kinematics. In the north-western corner a strong ~140 km s-1 gradient over ~1.5′′(~2.8 kpc at dLARS12 = 470.5 Mpc) is observed, but the velocity field is essentially flat from there towards the south-west. The high velocity and velocity dispersion in the values seen in the south are not significant, as the low S/N of this broad line in these binned spaxels lead to a 50% error on the determined vLOS and σ0 value. Because of PSF smearing effects the strong velocity gradient is responsible for the region of elevated velocity dispersions in the north-western corner.

For LARS 12 adaptive optics Paschen α IFS observations have been presented in Gonçalves et al. (2010); object ScUVLG 093813 in their nomenclature. Their line-of-sight velocity field is qualitatively fully consistent with ours, but their higher resolution data allows them to pinpoint the highest redshifted values directly to the two filaments that extend towards the north-west. Since they are not affected by PSF smearing their dispersion map is not contaminated by high-velocity dispersions in the north-west. Of course, our artifact in the south is also absent from their map. Nevertheless, their σ0 value of 62 km s-1 is in good agreement with our measurement of 72 km s-1.

Appendix A.13: LARS 13 (IRAS 01477+1254)

Based on its highly irregular morphology this starburst system is clearly interacting. As LARS 13 shows a narrow Lyα equivalent width (EWLyα = 6 Å), it would not be selected as a LAE at high redshift in conventional narrowband surveys. Overall, only 1% of Lyα photons are escaping and the resulting Lyα luminosity is LLyα = 7 × 1041 erg s-1.

The complex vLOS map of this galaxy is characterised by a gradient from blue- to redshifts along the east-western axis for the northern component, as well as an gradient from blue-to redshifts from south to north for the eastern component. In the north-western zone where the longitudinally aligned structure overlaps with the latitudinally aligned one, our single component Gaussian is not an optimal representation of the observed Hα line profiles. In this region, the profile is often asymmetric with an extended blue wing (e.g. right panel of Fig. A.3). Some spaxels show a double-peaked Hα profile (e.g. left and centre panels of Fig. A.3). The affected zone has a hatched rectangle overlaid in Fig. 7. In the region where two equally strong peaks are prominent in the spectrum, our fit tries to fit a broad line that encloses both lines; these spaxels can be seen in the east running as a diagonal line of broad velocity dispersions from north-west to south-east. Spaxels east of this demarcation show an extended blue wing. We interpret this to mean that we are seeing separate components of ionised gas kinematics, where one component belongs to the latitudinal elongated structure while the other belongs to the longitudinal elongated structure. The spatial and spectral proximity of both regions indicates that the galaxy is still in an ongoing interaction with both progenitors not having fully coalesced.

For LARS 13 adaptive optics Paschen α IFS observations have been presented in Gonçalves et al. (2010); object ScUVLG 015028 in their nomenclature. However, their small FoV allows them only to sample emission from the strongest star-forming region in the western part, and so they do not have any information on the longitudinally aligned eastern part. Consequently, their observed vshear = 78 km s-1 is lower than our value (vshear = 173 km s-1), since the north-eastern zone with highest vLOS values in our map is not present in their data. In the zone where they have signal, there is good qualitative and quantitative agreement between our maps and their maps. In particular, they found high velocity dispersions vFWHM ≳ 200 km s-1 and a weak velocity gradient in the north-western star-forming knot. In this region of high velocity dispersions Lyα appears to escape directly towards the observer.

Appendix A.14: LARS 14 (SDSS J092600.41+442736.1)

LARS 14 is the most luminous LAE in the sample (LLyα = 4.2 × 1042 erg s-1). It is also classified as a green pea galaxy (Cardamone et al. 2009, see also their Fig. 7). Green pea galaxies show commonly strong Lyα emission and are also thought to be Lyman continuum leaking galaxies (Jaskot & Oey 2014; Henry et al. 2015; Yang et al. 2015). Visible in the HST images is a small companion in the south and tidal tails extending to the east and south (Cardamone et al. 2009). Our seeing limited data does not provide enough resolution to disentangle this structure photometrically from the main component within the datacube. Kinematically, however, we observe that the southern region shears at 60−70 km s-1 with respect to the northern, with not much velocity substructure seen. In the main part we observe high velocity dispersions with vFWHM ≈ 175 km s-1, dropping to 80−90 km s-1 towards the companion. Our modelling of the Hα profile with a simple 1D Gaussian did not capture the extended broad wings seen in the Hα profiles. These broad wings likely trace outflowing ionised gas, and are a feature regularly observed in pea galaxies (Yang et al. 2015).

For this galaxy, adaptive optics Paschen α IFS observations have been presented in (Gonçalves et al. and 2009, object ScUVLG 92600 in their nomenclature). They report slightly higher values, both for the shear and the dispersion. Nevertheless, our derived vshear/σ0 = 0.6 ± 0.1 is consistent with their value of 0.51. This ratio would be lowered by about a factor of two, if only the northern main component is considered, since its velocity offset relative to the companion dominates the shear. The main component as such therefore presents the structure with the lowest vshear/σ0 of our whole sample.

All Tables

Table 1

Log of PMAS lens array observations of the LARS sample.

Table 2

Global kinematic parameters from Hα for the LARS galaxies, calculated as described in Sect. 5.2.

All Figures

thumbnail Fig. 1

Wavelengths of the redshifted Hα lines of the LARS galaxies (vertical dashed lines) compared to the night sky emission spectrum at Calar Alto (Sánchez et al. 2007a). Grey regions indicate the telluric absorption bands (O2B-Band: 6887 Å6919 Å, O2A-Band: 7607 Å7633 Å, and H2O a-Band: 7168 Å7304 Å, see e.g. Cox 2000).

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In the text
thumbnail Fig. 2

Representative resolving power map for the observation of LARS 1. The resolution is expressed as vFWHM of a 1D Gaussian fit. Black spaxels at the positions (x,y) = (0,14) and (8,15) are dead fibres.

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In the text
thumbnail Fig. 3

Integrated continuum-subtracted Hα profiles of the LARS galaxies (black) compared to summed 1D Gaussian model profiles (grey) from which radial-velocity and velocity-dispersion maps were generated.

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In the text
thumbnail Fig. 4

Uncertainties on derived velocity dispersions (left panel) and radial velocities (right panel) for Gaussian profile fits to Hα for all galaxies. All uncertainties for a specific galaxy have the same symbol according to the legend in the right panel.

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In the text
thumbnail Fig. 5

Comparison of LARS HST imaging results of the LARS sample to spatially resolved PMAS Hα spectroscopy. North is always up and east is always to the left. For each galaxy from top to bottom: the first panel shows the LaXs Hα line intensity map; tick labels indicate right ascension and declination and an asinh-scaling is used cut at 95% of the maximum value. The second panel shows a S/N map of the continuum-subtracted Hα signal observed with PMAS. Tick labels in the PMAS S/N map are in arc-seconds; the scaling is logarithmic from 1 to 103 and only spaxels with S/N> 1 are shown. The third panel shows the LARS Lyα images with a colour bar indicating the flux scale in cgs-units; scaling is the same as in the Hα map. The fourth panel shows resolution-corrected HαvFWHM maps from our PMAS observations and the corresponding HαvLOS maps are shown in the fifth panel. In the first and third panel, we indicate the position and extent of the PMAS field of view with a white box. Cyan contours in the HST Hα image are contours of constant surface brightness, adjusted to highlight the most prominent morphological features. Similarly, magenta contours in the HST Lyα images indicate the Lyα morphology; these contours are also shown in the fourth and fifth panel. To highlight the difference between Lyα and Hα, the Lyα and Hα panels contain as dashed yellow lines the contours from the Hα and Lyα panels, respectively.

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In the text
thumbnail Fig. 6

Comparison of LARS HST imaging results to spatially resolved PMAS Hα spectroscopy for LARS 9. For detailed description of individual panels see caption of Fig. 5. This galaxy was covered with 2 PMAS pointings. Hatched regions in the vLOS map indicate regions, where the Hα emission shows a more complex profile that could not be described by a simple Gaussian (see also Appendix A.9).

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In the text
thumbnail Fig. 7

Same as Fig. 6, but for LARS 13. Hatched region in the vLOS map indicates the region, where the Hα emission shows a more complex profile that could not be described by a simple Gaussian (see also Appendix A.13).

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In the text
thumbnail Fig. 8

Comparison of integrated H i linewidth W50 to FWHM of the Hα integrated velocity dispersion . The dashed line indicates the one-to-one relation. For LARS 6, (encircled point) we plot as W50, a preliminary result based upon VLA C-configuration interferometry, as the beam of the GBT profile (used to derive W50 in Paper III) is too broad to separate LARS 6 from a neighbouring galaxy.

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In the text
thumbnail Fig. 9

Global Hα kinematical parameters vshear (left panel), σ0 (middle panel), and vshear/σ0 (right panel) in comparison to stellar mass for LARS galaxies (from Paper II) and in comparison to literature values: DYNAMO z ~ 0.1 [compact] perturbed rotators from Green et al. (2014) as [small] green circles; DYNAMO z ~ 0.1 [compact] complex kinematics from Green et al. (2014) as [small] green squares; Local Lyman Break Analogues from Gonçalves et al. (2010) as blue circles; Keck/OSIRIS resolved z ~ 2−3 star-forming galaxies from Law et al. (2009) as red circles; SINS z ~ 2−3 galaxies from Förster Schreiber et al. (2009) as orange squares (only in the left panel). Uncertainties given where available. The LARS galaxies are represented by symbols according to the legend in the left panel. Spearman rank correlation coefficients ρs and corresponding p0 values for the LARS galaxies are shown in each panel.

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In the text
thumbnail Fig. 10

Global Hα kinematical parameters vshear (left panel), σ0 (middle panel), and vshear/σ0 (right panel) in comparison to SFR for LARS galaxies (from Paper II) and in comparison to literature values (same symbols as in Fig. 9). Uncertainties given where available. Spearman rank correlation coefficients ρs and corresponding p0 values for the LARS galaxies are shown in each panel.

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In the text
thumbnail Fig. 11

Relations between global Lyα properties of the LARS galaxies to global kinematical parameters vshear, σ0 and vshear/σ0.

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In the text
thumbnail Fig. 12

Relations between ξLyα, the “relative Petrosian extension of Lyα” as defined in Hayes et al. (2013), and global kinematical parameters vshear, σ0 and vshear/σ0 with symbols according to the legend in Fig. 9. For galaxies with no Lyα emission (LARS 4 and LARS 6, circled symbols) ξLyα is defined as zero and for LARS 9 the measured ξLyα presents a lower limit (see also Hayes et al. 2013). Spearman rank correlation coefficients ρs and corresponding p0 values are calculated excluding LARS 4 and LARS 6.

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In the text
thumbnail Fig. A.1

Representative LARS 9 Hα line profiles in blue hatched region of Fig. 6 described by a fit using two Gaussian components. The red dashed lines show the individual components and the blue line shows the sum, while the black line shows the profile as observed. For all profiles shown the single component fit used to create the map shown in Fig. 6 converged on the stronger red component.

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In the text
thumbnail Fig. A.2

Representative LARS 9 Hα line profiles in red hatched region of Fig. 6, similar to Fig. A.1. The single component fit used to create the map shown in Fig. 6 converged on the stronger blue component in the centre panel, but for the profiles shown in the left and right panels the single component fit is artificially broadened.

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In the text
thumbnail Fig. A.3

Representative LARS 13 Hα line profiles in blue hatched region of Fig. 7, similar to Fig. A.1. The single component fit used to create the map shown in Fig. 7 converged on the stronger blue component in the right panel, but for the profiles shown in the left and centre panels the single component fit is artificially broadened.

Open with DEXTER
In the text

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