The HI content of early-type galaxies from the ALFALFA survey

Abstract

Aims. We are using the Arecibo Legacy Fast ALFA survey (ALFALFA), which is covering 17% of the sky at 21 cm, to study the HI content of early-type galaxies (ETG) in an unbiased way. The aim is to get an overall picture of the hot, warm and cold ISM of ETG, as a function of galaxy mass and environment, to understand its origin and fate, and to relate it to the formation and evolution history of these objects. Methods. This paper deals with the first part of our study, which is devoted to the 8-16 deg. declination strip in the Virgo cluster. In this sky region, using the Virgo Cluster Catalogue (VCC), we have defined an optical sample of 939 ETG, 457 of which are brighter than the VCC completeness limit at B T = 18.0. We have correlated this optical sample with the catalogue of detected HI sources from ALFALFA. Results. Out of the 389 ETG from the VCC with B T ≤ 18.0, outside the 1 deg. region of poor HI detection around M 87, and corrected for background contamination of VCC galaxies without a known radial velocity, only 9 galaxies (2.3%) are detected in HI with a completeness limit of 3.5 and 7.6 × 10 7 M of HI for dwarf and giant ETG, respectively. In addition 4 VCC ETG with fainter magnitudes are also detected. Our HI detection rate is lower than previously claimed. The majority of the detected ETG appear to have peculiar morphology and to be located near the edges of the Virgo cluster. Conclusions. Our preliminary conclusion is that cluster ETG contain very little neutral gas, with the exceptions of a few peculiar dwarf galaxies at the edge of the ETG classification and of very few larger ETG, where the cold gas could have a recent external origin.

TheHerschelVirgo Cluster Survey

“…Indeed, Hi detected dEs are preferentially located in the outskirts of the cluster and may not have been dramatically affected so far by the intracluster medium and interactions with other galaxies (Conselice et al 2003;Buyle et al 2005). di Serego Alighieri et al (2007) also report that the majority of the detected Hi-sources are located near the edges of the Virgo cluster. If gas and dust are tightly coupled and dust is as easily removed from the galaxy as gas by ram pressure stripping, harassment, or tidal effects, we expect that the dEs in the central regions of the Virgo cluster will also be the most dust deficient.…”

“…Atomic and molecular gas was discovered for the first time in the Local Group dEs NGC 185 and NGC 205 using deep VLA and BIMA observations (Young & Lo 1997). In the Virgo cluster, Conselice et al (2003) estimate a Hi detection rate of 15% for dEs down to a 3σ limit of 8 × 10 6 M , while di Serego Alighieri et al (2007) report a 1.7% Hi detection rate with a 3σ detection limit of 3.5 × 10 7 M . Large amounts of cold Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.…”

ALMA observations of cold molecular gas filaments trailing rising radio bubbles in PKS 0745−191

“…Young et al 2011). Observations of Virgo cluster members have shown that galaxies with strong HI deficiencies have minimal molecular gas deficiencies (Kenney & Young 1989;di Serego Alighieri et al 2007;Grossi et al 2009). In PKS 0745-191, the filaments have low velocities, radial morphologies and shallow velocity gradients with no indication of the high velocities and large-scale rotation expected from the stripping of a merging galaxy (eg.…”

TheHerschelVirgo Cluster Survey

“…Table 4 also contains complete information about the neutral atomic hydrogen (Hi) content of the ETG detected in HeViCS. This information is obtained from the Hi survey of ETG in the Virgo cluster done by di Serego Alighieri et al (2007), using the Arecibo Legacy Fast ALFA (ALFALFA, Giovanelli et al 2005Giovanelli et al , 2007. Appendix B of the present paper contains an update of that survey to extend it to the 4-8 deg, declination strip, which has recently become available in ALFALFA (Haynes et al 2011).…”

“…Table 4 also contains the Hi mass for VCC 450 and VCC 758, which have been detected in Hi in the deeper Arecibo survey AGES (Taylor et al 2012). The upper limits are described in di Serego Alighieri et al (2007) for an assumed distance of 16.7 Mpc to the whole of the Virgo cluster, and are given in Table 4 for the distances assumed in this paper. Figure 6 shows the dust-to-atomic-gas mass ratio for Virgo ETG, showing large variations, even for objects with the same luminosity.…”