The Herschel Virgo Cluster Survey - VIII. The Bright Galaxy Sample★

Abstract

We describe the Herschel Virgo Cluster Survey and the first data that cover the complete survey area (four 4 × 4 deg2 regions). We use these data to measure and compare the global far‐infrared properties of 78 optically bright galaxies that are selected at 500 μm and detected in all five far‐infrared bands. We show that our measurements and calibration are broadly consistent with previous data obtained by the IRAS, ISO, Spitzer and Planck. We use SPIRE and PACS photometry data to produce 100‐, 160‐, 250‐, 350‐ and 500‐μm cluster luminosity distributions. These luminosity distributions are not power laws, but ‘peaked’, with small numbers of both faint and bright galaxies. We measure a cluster 100–500 μm far‐infrared luminosity density of 1.6(7.0) ± 0.2 × 109 L⊙ Mpc−3. This compares to a cluster 0.4–2.5 μm optical luminosity density of 5.0(20.0) × 109 L⊙ Mpc−3, some 3.2(2.9) times larger than the far‐infrared. A ‘typical’ photon originates from an optical depth of 0.4 ± 0.1. Most of our sample galaxies are well fitted by a single modified blackbody (β= 2), leading to a mean dust mass of log MDust= 7.31 M⊙ and temperature of 20.0 K. We also derive both stellar and atomic hydrogen masses from which we calculate mean values for the star‐to‐gas (atomic) and gas (atomic)‐to‐dust mass ratios of 15.1 and 58.2, respectively. Using our derived dust, atomic gas and stellar masses, we estimate cluster mass densities of 8.6(27.8) × 106, 4.6(13.9) × 108 and 7.8(29.7) × 109 M⊙ Mpc−3 for dust, atomic gas and stars, respectively. These values are higher than those derived for field galaxies by factors of 39(126), 6(18) and 34(129), respectively. In the above, the luminosity/mass densities are given using the whole sample with the values in brackets using just those galaxies that lie between 17 and 23 Mpc. We provide a data table of flux densities in all the Herschel bands for all 78 bright Virgo Cluster galaxies.

TheHerschelVirgo Cluster Survey

“…Eales et al (2012) proposed that dust emission can be used to map the ISM in high redshift galaxies: adopting the emissivity of Galactic dust, they derived a linear correlation between the monochromatic luminosity at 250 μm and the total mass of hydrogen (using the Galactic X CO and calibrating the relation on a few nearby galaxies observed with Herschel and with gas mass estimates). With the dust temperatures measured on our maps (T ∼ 20 K, see Davies et al 2012), their correlation can be converted to log Σ gas = log F 250 + 1.62, in good agreement with Eq. (3).…”

“…Each pixel was fitted with a single temperature modified black body, with dust emissivity κ ∝ ν β and β = 2; the filter response function was taken into account for the color correction. As shown by Davies et al (2012) for global fluxes, and by Magrini et al (2011) for pixel-by-pixel surface brightness analysis, our choice of the dust emissivity provides a satisfactory fit to the spectral energy distribution. If we exclude the notorious uncertainty of the dust emissivity, the uncertainties due to the fitting procedure amounts to 10-15% for the full depth HeViCS data set.…”

HERschelObservations of Edge-on Spirals (HEROES)

“…Furthermore, this value of β and the average temperature T d = (19.8 ± 1.6) K, that we obtain, are very typical values for the interstellar dust medium in spiral galaxies (e.g. Dunne et al 2011;Davies et al 2012;Smith et al 2012;Boselli et al 2012;Galametz et al 2012). As the latter model only reproduces datapoints longwards of 100 μm, the dust mass values we give do not take into account the possible presence of warmer dust, whose signature would show up at shorter wavelengths.…”

“…A quantitative comparison of these spiral galaxy radiative transfer models based on optical extinction with FIR/sub-mm emission observations leads to an interesting discrepancy: the rather optically thin dust discs determined from the optical modelling absorb about 10% of the stellar radiation, whereas the FIR/sub-mm observations of normal spiral galaxies indicate they typically reprocess about 30% of the UV and optical radiation Davies et al 2012). This dust energy balance problem is particularly evident when studying individual edge-on spiral galaxies: self-consistent radiative transfer models which successfully explain the optical extinction, predict FIR/sub-mm fluxes that underestimate the observed values by a factor of about three (Popescu et al 2000;Misiriotis et al 2001;Alton et al 2004;Dasyra et al 2005;Baes et al 2010;De Looze et al 2012a).…”

The GALEX Ultraviolet Virgo Cluster Survey (GUViCS)

“…Boselli 2011). Several blind surveys of the Virgo cluster have been recently completed in the optical bands (NGVS; Ferrarese et al 2012), the mid-(WISE; Wright et al 2010) and far-infrared (HeViCS; Davies et al 2010Davies et al , 2012, and the 21 cm HI line (ALFALFA; Giovanelli et al 2005). The GALEX Ultraviolet Virgo Cluster Survey (GUViCS; Boselli et al 2011), a deep blind survey in two UV photometric bands of ∼300 deg 2 , which is centred on M87, has been recently completed.…”