Free Access
Volume 575, March 2015
Article Number A44
Number of page(s) 17
Section Extragalactic astronomy
Published online 20 February 2015

Online material

Appendix A: Notes on the individual detections

1: B3 0754+401

This source is part of the low luminosity CSS sample presented by Kunert-Bajraszewska & Labiano (2010). The largest linear size of the source is 0.25 kpc, and the morphology remains unresolved in the multi-element radio linked interferometer network (MERLIN) observations. Kunert-Bajraszewska & Labiano (2010) classified this object as a High Excitation Galaxy (HEG). We detect H I in this source at the systemic velocity. The width and asymmetry parameters of the H I suggest that the gas in this galaxy is not entirely settled.

2: 2MASX J08060148+1906142

This source has never been studied individually before. The relatively large width (FW20 = 266 km s-1) and double-peaked nature of the H I profile suggest that unsettled gas is present in this galaxy.

3: B2 0806+35

This source shows radio emission both on the kpc and pc scale. It has been observed with VLBA at 5 GHz as part of a polarization survey of BL-Lac objects (Bondi et al. 2004) as a possible BL-Lac candidate. On the parsec scale (beam size of 3.2 × 1.7 mas) the source reveals a radio core with an extended jet towards the south. The jet extends for about 10 milliarcsec (mas) (~15 pc at z = −0.0825). Among the BL-Lac candidates, this source is the weakest object, and has the steepest radio spectrum. It is also the only object not showing polarized emission neither in the jet or the core. In this galaxy, the narrow H I line is detected at blueshifted velocities with respect to the systemic.

4: B3 0833+442

In the CORALZ sample this source is classified as a CSO. However, the 1.6 GHz VLBI image (de Vries et al. 2009) shows a C-shaped radio structure. The LLS of the source is 1.7 kpc. Chandola et al. (2011) did not find H I in this source. In our observations, we detect a narrow H I profile, slightly redshifted from the systemic velocity. The data cube also reveals (faint) H I emission.

5: B3 0839+458

This source has been observed as part of the Combined Radio All-Sky Targeted Eight GHz Survey (CRATES) sample (Healey et al. 2007). It has been classified as a point source with flat spectrum (spectral index α = −0.396). The VLBA observations at 5 GHz, as part of the VLBA Imaging and Polarimetry survey (VISP, Helmboldt et al. 2007), classify it as a core-jet source. The lobes have sizes of approximately 3.5 mas and are separated by 6 mas (=0.2 kpc at z = 0.1919). The radio power of the source is P1.4GHz ~ 3 × 1025 W Hz-1. In our work, we detect the H I at the systemic velocity of the galaxy (Δv = 57 km s-1). The line is narrow and deep, suggesting that the H I is settled in a rotating disk around the host galaxy. The line has a slight asymmetry along the blueshifted edge not fitted by the BF.

6: Mrk 1226

This source has been observed as part of the CRATES sample (Healey et al. 2007). It has been classified as a point source with flat spectrum (spectral index α = 0.284). The object has also been observed as part of the VISP survey at 5 GHz (Helmboldt et al. 2007). The approximate size of the radio source is 15 mas (~8 pc at z = 0.0279). We detect H I absorption close to the systemic velocity of the host galaxy. This, along with the symmetry of the line, suggests that we are tracing neutral hydrogen rotating in a disk. The host galaxy may have experienced a gas rich merger which has formed the H I disk.

7: UGC 05101 – IRAS F09320+6134

This radio source is hosted by an ultra-luminous far-infrared (ULIRG) Galaxy. The galaxy is undergoing a merger event, as also suggested by its optical morphology. The source has also been observed with a ~11.6 × 9.9 mas resolution using VLBI (Lonsdale et al. 2003). These observations show three compact (34 pc) cores connected by a fainter component. The size of the overall structure is 48 × 24 pc. These VLBI observations also show that the radio continuum is dominated by the AGN and not by the starburst activity. The radio power of the source is P1.4 GHz ~ 3 × 1023 W Hz-1. At the resolution of our observations, we are not able to disentangle the absorption seen against the different components: we detect a broad, blended line. The profile is also multi-peaked, reflecting the unsettled state of the neutral hydrogen disk and of the overall host galaxy. The H I has been detected in emission via Effelsberg Telescope observations, through the study of polar-ring galaxy candidates (Huchtmeier 1997). The emission line is broad and asymmetric, with a peak flux of + 2.2 mJy beam-1. The low sensitivity of the spectrum does not allow us to set further constraints. The detection in emission has been confirmed by observations with the Nançay decimetric radio telescope, with higher sensitivity (van Driel et al. 2000)2.

8: 4C +48.29

This extended AGN is an X-shaped radio source (Jaegers 1987; Mezcua et al. 2011; Landt et al. 2010). We detect a double-peaked H I profile close to the systemic velocity. Before Hanning smoothing, the two peaks are more separated, suggesting the presence of two H I components (one at the systemic and one blueshifted).

9: J105327+205835

In the literature there are no records of individual observations of this radio source. The NVSS and FIRST images suggest that it is a compact source. In our observations, we detect a broad profile peaked at the systemic velocity and slightly asymmetric towards blueshifted velocities. The SDSS image shows that the host galaxy of this source is very close to a companion. Past interaction with a companion could explain the presence of the H I in the system.

10: 2MASX J112030+273610

There are no individual radio observation of this source reported in the literature. According to our classification, it is a compact source. The detected H I profile is narrow and blueshifted with respect to the optical velocity. This may indicate that we are tracing neutral hydrogen which is not settled in a rotating disk.

11: 2MASX J12023112+1637414

This source has never been studied individually before. According to our classification it is a compact source, showing a shallow, blueshifted profile, indicative of outflowing gas.

12: NGC 4093 - MCG +04-29-02

VLA observations reveal compact radio morphology in this source (Burns et al. 1987; del Castillo et al. 1988). We detect a regular H I component at the systemic velocity, likely tracing the kinematics of a rotating disk.

13: B3 1206+469

This radio source has been selected as part of the Cosmic Lens All Sky Survey (CLASS) as a possible BL-Lac object and then classified as a lobe dominated steep spectrum source. This radio source is extended with a central core and two symmetric lobes oriented in the north-south direction. The distance between the lobes is ~4 arcmin (~550 kpc at z = 0.100). The spectral index has been measured in the wavelength intervals 1.44.8 GHz and 1.48 GHz: , ; (Marchã et al. 2001). Being extended, the steepness of the spectrum can be explained by the fact that some of the flux is missed by the VLA observations at 8.4 GHz. In our observations, we detect a narrow and shallow absorption line close to the systemic velocity.

14: B2 1229+33

This extended source was classified as an FR II by Cohen et al. (2004). Based on the SDSS optical spectrum and image, it appears to be a High Excitation Radio Galaxy (HERG). Optically, the galaxy appears to be blue (gr = 0.6), hence it has been excluded from the analysis of the overall sample presented in Sects. 4 and 5. The H I profile shows a narrow detection at the systemic velocity and, a second, redshifted component is also seen. These H I properties suggest the presence of a disk and infalling gas in this object.

15: 4C +49.25

The size of this CSS source is 6 kpc (Saikia & Gupta 2003; Fanti et al. 2000). The 5 GHz VLA map reveals a core and two jets on the opposite sides (Saikia & Gupta 2003). It was suggested by Saikia & Gupta (2003) that the higher degree of polarization asymmetry in CSS objects, including 4C +49.25, could be the result of interactions with clouds of gas which possibly fuel the radio source. Indeed, we find a blueshifted, shallow H I component in this source. This could be the result of outflowing gas, induced by jet-ISM interactions. At the systemic velocity, however, we do not detect H I.

16: 2MASX J125433+185602

The source belongs to the CRATES sample (Healey et al. 2007). It has been classified as a point source with flat spectrum (spectral index α = 0.282). Observations at 5 GHz, as part of the VISP survey (Helmboldt et al. 2007), identify this source as a CSO. Its lobes are separated by 7.3 mas (~15 pc at z ~ 0.0115). We detect H I at redshifted velocities compared to the systemic. The line is narrow and asymmetric, with a broader wing towards lower velocities. The redshift of the line, along with the compactness of the source, suggests that the neutral hydrogen may have motions different from simple rotation in a disk.

17: 2MASX J13013264+4634032

According to Augusto et al. (2006), this radio source is a point source. We detect a faint, blueshifted H I profile, which can indicate interactions between the AGN and the surrounding gaseous medium. The radio source is a Blazar candidate in the CLASS and CRATES surveys (Caccianiga et al. 2002; Healey et al. 2007). However, it remains classified as an AGN by Caccianiga et al. (2002).

18: B3 1315+415

VLBI observations of the CORALZ sample (de Vries et al. 2009) reveal complex radio morphology in this object. The source has a small size of LLS = 5 pc. From the lobe expansion speed analysis (de Vries et al. 2010), a dynamical age of 130 yr is estimated in this source. Chandola et al. (2011) detected H I absorption redshifted by + 77 km s-1 relative to the systemic velocity, indicating in-falling gas towards the nuclear region. Our observations confirm the H I detection.

19: IC 883 – ARP 193 – UGC 8387

The host galaxy of this radio source is undergoing a major merger. The galaxy is a luminous infrared galaxy (LIRG) where LIR = 4.7 × 1011L at z = 0.0233 (Sanders et al. 2003). The radio source has been observed with e-Merlin (beam size =165.23 × 88.35 mas) and VLBI e-EVN (beam size =9.20 × 6.36 mas) (Romero-Cañizales et al. 2012). The radio source consists of 4 knots and extends for about ~750 pc. The innermost 100 pc of the galaxy show both nuclear activity and star formation. The nuclear activity originates in the central core, while the radio emission from the other knots is attributed to transient sources. This galaxy has already been observed in H I in the study of polar ring galaxy candidates (Huchtmeier 1997). Two complementary observations have been performed using the Green Bank Telescope and the Effelsberg Telescope. Because of the different sensitivity of the instruments, the H I has been detected in emission only in the Green Bank observations (Richter et al. 1994), with a peak flux =2.4 mJy. In IC 883, CO(10) and CO(32) are detected by Yao et al. (2003) in the same range of velocities as the H I emission. The resolution of our observations does not allow the disentanglement of different absorption components. Hence, the H I line in our observations is blended, spanning the same velocity range of the H I seen in emission, and of the molecular gas. The morphology of the absorption line, along with the overall properties of the cold gas detected in emission, suggests that in this galaxy the cold gas is rotating in a disk, which is unsettled because of the ongoing merger event2.

20: SDSS J132513.37+395553.2

In the CORALZ sample this source is classified as a compact symmetric object (CSO), with largest (projected) linear size (LLS) of 14 pc (de Vries et al. 2009). Our observations show two H I components, one blueshifted, and the other redshifted relative to the systemic velocity. The newly detected H I profiles suggest that unsettled gas structures are present in this galaxy, e.g., infalling clouds, outflowing gas.

21: IRAS F13384+4503

This galaxy is optically blue (gr = 0.6), and the SDSS image revels a Seyfert galaxy with late-type morphology. This object is not included in the analysis presented in Sect. 4 and Sect. 5. In the CORALZ sample, the radio source is classified as a compact core-jet (CJ) source with two components which are significantly different in flux density and/or spectral index (de Vries et al. 2009). The largest linear size of the source is 4.1 pc. Against the small continuum source, a very narrow H I absorption profile is detected at the systemic velocity, indicative of a gas disk.

22: Mrk 273

This object is the host of an ongoing merger. The optical morphology shows a long tidal tail extending 40 kpc to the south (Iwasawa et al. 2011, and references therein). Low-resolution 8.44 GHz radio maps by Condon et al. (1991) show three radio components, a northern (N), south-western (SW), and a south-eastern (SE) region. The origin of the SE and SW component is unclear (Knapen et al. 1997; Carilli & Taylor 2000). The N radio component is slightly resolved in the observations of Knapen et al. (1997); Carilli & Taylor (2000); Bondi et al. (2005), showing two peaks embedded in extended radio emission. It is thought that the northern component is hosting a weak AGN, however it is also the site of very active star-formation. Using Very Long Baseline Array (VLBA) observations, Carilli & Taylor (2000) detected H I absorption against the N component supposedly coming from a disk (showing velocity gradient along the major axis), and estimated an H I gas mass of 2 × 109M. Molecular CO gas of similar amount (109M) was also detected by Downes & Solomon (1998). Carilli & Taylor (2000) also detect extended gas and an infalling gas cloud towards the SE component, suggesting that the SE component is indeed an AGN. Our low-resolution observations cannot distinguish between the different absorbing regions, we detect the blended signal, coming from all the H I absorbing regions. The broad H I absorption was also detected with the single dish Green Bank Telescope (GBT) by Teng et al. (2013).

23: 3C 293

This object is a compact steep spectrum (CSS) radio source, whose emission is divided in multiple knots (Beswick et al. 2004). It is a restarted radio source, possibly activated by a recent merger event (Heckman et al. 1986). Massaro et al. (2010) classify the radio source as FRI. A rotating H I disk has been detected in absorption by Baan & Haschick (1981). WSRT observations (Morganti et al. 2005) show an extremely broad absorption component at blueshifted velocities (FWZI = 1400 km s-1). VLA-A array observations, with 1.2 × 1.3 arcsec of spatial resolution, identify this feature as a fast H I outflow pushed by the western radio jet, located at 500 pc from the core (Mahony et al. 2013). The radio jet is thought to inject energy into the ISM, driving the outflow of H I at a rate of 850 M yr-1. The broad shallow outflowing component is also detected. The fit of the spectrum with the BF identifies the rotating component, while it fails in fitting the shallow wings, highlighting the different nature of these clouds.

24: 2MASX J142210+210554

There are no individual observations of this source available in the literature. In our classification, the radio source is compact. The SDSS observations show that it is hosted by an early-type galaxy. We detect an absorption line, blueshifted with respect to the systemic velocity. The line is broad and asymmetric with a smoother blueshifted edge.

25: 2MASX J14352162+5051233

This is an unresolved CORALZ AGN, the size of the radio source is estimated to be 270 pc. This galaxy has been observed in H I by Chandola et al. (2011), however no components were detected. Our observations show a shallow, broad, blueshifted H I profile without deep/narrow component at the systemic velocity. Likely we are seeing gas interacting with the radio source.

26: 3C 305 – IC 1065

The H I profile of this source shows a deep, narrow component, which could be associated with rotating gas. Furthermore, Morganti et al. (2005) reported the presence of a jet-driven H I outflow in this galaxy. The outflow is also detected in our observations, and it is successfully fitted by the BF. The column density of the outflow is N(H I) = 2 × 1021, assuming Tspin = 1000 K, and the corresponding H I mass was estimated to be M(H I) = 1.3 × 107M (Morganti et al. 2005). X-ray observations suggest that the power supplied by the radio jet to the H I outflow is ~1043 erg s-1 (Hardcastle et al. 2012). Molecular H II gas was also detected in this source by Guillard et al. (2012). However the molecular phase of the gas is inefficiently coupled to the AGN jet-driven outflow. Massaro et al. (2010) classified this source as a high excitation galaxy (HEG).

27: 2MASX J150034+364845

In the literature, there is no record of targeted observations of this radio source. According to our classification it is a compact source. We detect a deep absorption line. The line lies at the systemic velocity of the host galaxy and traces a regularly rotating H I disk. The line is slightly asymmetric in the blueshifted range of velocities. This asymmetry is not recovered by the BF fit, suggesting that non-circular motions characterize the neutral hydrogen.

28: 2MASX J15292250+3621423

We find no individual observations of this source in the literature. In our sample it is classified as a compact source. We detect H I in this object close to the systemic velocity. However, similarly to the case of source #9 the profile is not entirely smooth.

29: 4C +52.37

This source is classified as a compact symmetric object (CSO) in the CORALZ sample. High-resolution observations reveal a core, and jet-like emission on the opposite sides (de Vries et al. 2009). The main H I absorption component in 4C +52.37 was detected by Chandola et al. (2011), using the Giant Metrewave Radio Telescope (GMRT). Besides the main H I line, we detect a broad, shallow profile of blueshifted H I absorption. The broad component was not detected by Chandola et al. (2011), most likely because of the higher noise of the GMRT spectra. The kinematical properties of the newly detected blueshifted wing are indicative of a jet-driven H I outflow in this compact radio source.

30: NGC 6034

This radio source is hosted by a S0 optical galaxy, which belongs to cluster A2151 of the Hercules Supercluster. The radio source is extended, with two jets emerging toward the north and the south (Mack et al. 1993). The spectrum is flat with no variation of the spectral index (α = −0.65). The line is very narrow and it is centred at the systemic velocity. This suggests that the H I may form a rotating disk in the host galaxy. The neutral hydrogen in NGC 6034 has been first detected in absorption by VLA observations (Dickey 1997)2.

31: Abell 2147

Based on the SDSS optical images, the host galaxy of this source is an early-type galaxy with a very red bulge. Taylor et al. (2007) classified this object as a flat-spectrum radio quasar. The size of the radio source is about 10 mas (~20 pc at z = 0.1), and the morphology remains unresolved in the 5 GHz VLBA images. Therefore, it is intriguing that we find a broad H I detection against this very compact radio source. It is likely that along the line of sight the H I has non-circular motions.

32: 2MASX J161217+282546

The radio source is hosted by an S0 galaxy and has been observed with the VLA-A configuration by Feretti & Giovannini (1994). At the resolution of the VLA-A observations (1.4 × 1.1 arcsec, ~0.7 kpc at z = 0.0320), the radio source is unresolved. We detect an absorption line at the systemic velocity of the host galaxy, indicative of neutral hydrogen rotating in a disk.

Appendix B: Summary table of non-detections

Table B.1

H I non-detections.

© ESO, 2015

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