TheHerschelVirgo Cluster Survey

Abstract

Aims. We study the dust content of a large optical input sample of 910 early-type galaxies (ETG) in the Virgo cluster, also extending to the dwarf ETG, and examine the results in relation to those on the other cold ISM components. Methods. We have searched for far-infrared emission in all galaxies in the input sample using the 250 μm image of the Herschel Virgo Cluster Survey (HeViCS). This image covers a large fraction of the cluster with an area of ∼55 square degrees. For the detected ETG we measured fluxes in five bands from 100 to 500 μm, and estimated the dust mass and temperature with modified black-body fits. Results. Dust is detected above the completeness limit of 25.4 mJy at 250 μm in 46 ETG, 43 of which are in the optically complete part of the input sample. In addition, dust is present at fainter levels in another six ETG. We detect dust in the four ETG with synchrotron emission, including M 87. Dust appears to be much more concentrated than stars and more luminous ETG have higher dust temperatures. Considering only the optically complete input sample and correcting for the contamination by background galaxies, dust detection rates down to the 25.4 mJy limit are 17% for ellipticals, about 40% for lenticulars (S0 + S0a), and around 3% for dwarf ETG. Dust mass does not correlate clearly with stellar mass and is often much greater than expected for a passive galaxy in a closedbox model. The dust-to-stars mass ratio anticorrelates with galaxy luminosity, and for some dwarf ETG reaches values as high as for dusty late-type galaxies. In the Virgo cluster slow rotators appear more likely to contain dust than fast ones. Comparing the dust results with those on Hi there are only eight ETG detected both in dust and in Hi in the HeViCS area; 39 have dust but only an upper limit on Hi, and eight have Hi but only an upper limit on dust. The locations of these galaxies in the cluster are different, with the dusty ETG concentrated in the densest regions, while the Hi rich ETG are at the periphery.

The bivariateK-band-submillimetre luminosity functions of the local HRS galaxy sample

“…Boquien et al (2011), Bendo et al (2012, Groves et al (2012), and Smith et al (2012b) all show that it is even possible for dust to be heated by evolved stars in a large bulge even if the dust and stars have different distributions (as is the case in M31 and M81) and that the temperature of the cold dust is tightly driven by the evolved stellar populations. Mathews et al (2013) suggest that this lack of dependency is due to the relocation of variable masses of cold dust away from the central reservoir, eventually triggered by the central AGN and then destroyed by sputtering (see also Smith et al 2012a;di Serego Alighieri et al 2013). Indeed, among the HRS earlytype galaxies, M86 shows dust that is displaced with respect to the nucleus, and probably accreted from an external object during a merging process (Gomez et al 2010), M87 whose submm emission is mainly due to synchrotron , and M84 whose 500 µm and partially likely 350 µm emissions are dominated by synchrotron radiation (Boselli et al 2010b).…”

A star formation study of the ATLAS3Dearly-type galaxies with the AKARI all-sky survey

“…It has already been shown that AKARI fluxes are in good agreement with analogous measurements by Spitzer and Herschel (Suzuki et al 2010;Hattori et al 2016), but we nevertheless check the quality of our measurement here by comparing our AKARI 90 and 140 µm flux densities with Spitzer and Herschel measurements. Among our sample, 89 galaxies have published Spitzer 70 µm measurements (Amblard et al 2014), and 22 galaxies have both Herschel 100 and 160 µm measurements (Dale et al 2012;di Serego Alighieri et al 2013;Baes et al 2014). In all cases (AKARI 90 µm vs. Spitzer 70 µm, AKARI 90 µm vs. Herschel 100 µm and AKARI 140 µm vs. Herschel 160 µm), we find that most measurements are consistent within the uncertainties, and that they are proportional with a slope of approximately unity and a small intrinsic scatter of 0.2 dex, thus confirming the reliability of our measurements.…”

Formation of S0 galaxies through mergers

“…Bedregal et al 2006;Davis et al 2011). Nevertheless, many recent works claim that the dust content of S0s may have been significantly underestimated (Patil et al 2007;Riad et al 2010;Rowlands et al 2012;di Serego Alighieri et al 2013) and that an improper dust correction could lead to underestimation of the luminosity of a galaxy (or, equivalently, its stellar mass) to ∼ 40% of its real value (Zibetti et al 2009). …”