Free Access
Issue
A&A
Volume 574, February 2015
Article Number A126
Number of page(s) 30
Section Extragalactic astronomy
DOI https://doi.org/10.1051/0004-6361/201424866
Published online 05 February 2015

Online material

Appendix A: HeViCS BGC, DGS, KINGFISH stellar masses: comparison to previous estimates

Different stellar-mass estimation methods can yield mass values that disagree by factors up to ~2 (Kannappan & Gawiser 2007; McGaugh & Schombert 2014). To assess the reliability of our estimates based on MIR photometry, in this appendix we compare the stellar masses of the BGC, DGS, and KINGFISH samples to those derived by previous studies. In Fig. A.1 we show the results for the HeViCS BGC galaxies which are compared to Gavazzi et al. (2013a), where stellar masses were calculated using a relation combining the gi colour and the i magnitude, calibrated on the MPA-JHU sample. We find a fair good agreement between the two estimates for this sample (purple diamonds), as we found for the HeViCS SFDs (blue dots, see Sect. 5.1): the residual distribution for the BGC sample (purple histogram) is slightly asymmetric, and peaks at 0.06 dex, with a dispersion of 0.13 dex.

Regarding the DGS, comparison to Rémy-Ruyer et al. (2013), where stellar masses were derived from IRAC 3.6 and 4.5 μm photometry following the method of Eskew et al. (2012), shows that our estimates are on average systematically smaller by a factor of ~0.17 ± 0.05 dex.

thumbnail Fig. A.1

Upper panel: comparison between stellar masses estimated in this work from WISE photometry, , and those derived from the i magnitude and (gi)0 colour following Gavazzi et al. (2013a), extracted from the GOLDMine database . Blue dots and purple diamonds correspond to the HeViCS SFDs and BGC galaxies, respectively. The dotted line shows the one-to-one relation. Lower panel: distribution of the residuals of the two stellar mass estimates for the HeViCS dwarfs (blue histogram) and BGC galaxies (purple histogram). The resulting gaussian fit is overlaid to both histograms.

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Finally, comparison to the stellar masses of the KINGFISH sample calculated by Skibba et al. (2011) based on optical colours (Zibetti et al. 2009) shows that our estimates are on average systematically larger by a factor of ~0.5 dex. However for those galaxies with available SDSS photometry we compared our estimates with the stellar masses determined from i-band luminosities Li using the gi colour-dependent stellar mass-to-light ratio relation (Zibetti et al. 2009), and found an average difference of 0.11 dex with a dispersion of 0.17 dex. The discrepancy is larger when the relations using BV, or BR colours are used for those objects without SDSS photometry.

Appendix B: Two-component modified black-body SED fitting

Analysing two-component MBB models is important to begin to assess the dust temperature mixing along the line of sight, which could in principle lead to a lower β value when the SED fitting takes only into account one dust component. We combined MIR photometry from the literature with our FIR-submm observation for a subset of 14 galaxies with available mid-infrared (MIR) observations (see Sect. 5.5), and we fitted the SED using two modified black-body models, one for the warm component and one for the cold component. We fixed the emissivity index of the warm component at βw = 2, an approximation of the opacity in the standard Li & Draine (2001) dust models, and that of the cold component at βc = 1.5. We used the 22 μm data point in the fit as an upper limit to better constrain the warm dust modified blackbody. The result is shown in Fig. B.1. For two galaxies an additional dust component is not necessary to fit observations at 60 and 100 μm (VCC213, VCC1725).

The temperature of the warm component ranges between 43 and 54 K, while the change in the cold dust temperature, compared to a single temperature MBB fit (see Tables B.1 and 4), varies between –0.1 and –4.3 K.

Table B.1

Two-component MBB SED fitting for the subset of Virgo dwarfs with IRAS and ISO photometry.

thumbnail Fig. B.1

2-component MBB fits for 14 dwarfs with available IRAS and ISO photometry. Filled red dots correspond to IRAS or ISO data, while black dots show Herschel photometry. The emissivity index of the cold dust component (dotted line) is fixed at βc = 1.5, while the warm dust component (dashed line) has βw = 2.0. The VCC catalogue ID is given at the upper-left corner of each plot.

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Appendix C: Data Tables and SED fitting results

Table C.1

Herschel photometry of the sample of Virgo star-forming dwarf galaxies.

Table C.2

Stellar masses, Hi masses, dust masses, star formation rates, metallicities, Hi deficiency, and distances of the 27 objects selected from the Dwarf Galaxy Survey.

Table C.3

Stellar masses, Hi masses, dust masses, star formation rates, metallicities, Hi deficiency, and distances of the KINGFISH dwarf galaxy sample.

Table C.4

Stellar masses, Hi masses, dust masses, star formation rates, H2 masses, Hi deficiency and distances of KINGFISH spiral galaxies (from Sa to Sd).

Table C.5

Stellar masses, Hi masses, dust masses, star formation rates, H2 masses, Hi deficiency, and distances of HeViCS BGC galaxies.

thumbnail Fig. C.1

Free-β MBB fitting for 30 Virgo SFDs detected in four bands (100, 160, 250, 350 μm). The best-fit emissivity index is displayed at the upper-right corner, and the VCC catalogue ID is given at the lower-left corner of each plot.

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thumbnail Fig. C.2

Fixed-β MBB fitting (β = 1.5) for the whole sample of Virgo dwarfs detected with Herschel (black solid line). The reduced χ2 value of the fitting is displayed at the upper-right corner of each plot. The VCC catalogue ID is given at the lower-left corner of each plot. The red dotted lines correspond to the MBB obtained by fitting only three points of the SED (160–350 μm) instead of four points (100–350 μm). The three-point fits are shown only for those galaxies where the difference between the dust masses derived with the two methods, , is larger than ~0.1 dex, the mean uncertainty on .

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