Environmental effects on the cold gas content of group galaxies Barbara Catinella ARC Future Fellow Swinburne University of Technology The Role of Hydrogen in the Evolution of Galaxies, Sarawak, Sep 18 2014
The HI window on galaxies Reservoir for future star formation kinematical tracer best tracer of tidal interactions key role in every step of galaxy evolution blue, SF galaxies red and dead galaxies M81 group, Yun et al. (1994)
HI deficiency in galaxy clusters 90% of HI removed! Chung et al. (2009) Boselli & Gavazzi (2006) HI deficiency (Haynes & Giovanelli 1984, Solanes et al. 1996...) HI def Log <M(HI, Dopt,Type)> Log M(HI)obs
HI scaling relations and environment Powerful tools to study effects of environment on galaxy evolution Herschel Reference Survey (Boselli et al 2010): 322 galaxies (62 E/SO, 260 Sp./Irr) Volume/Stellar Mass limited - from isolated to cluster galaxies Cortese, Catinella et al. (2011) HI content determined primarily by stellar mass, environment is secondary. Environmental comparisons must be done at fixed stellar mass.
Scaling relations and models Models of Boissier & Pranzos (2000) calibrated on pure disk galaxies Starvation (stop of gas infall) Gas stripped from the disk Cortese, Catinella et al. (2011) (see also Boselli & Gavazzi 2006, Chung et al. 2007, Vollmer et al. 2009)
Most galaxies are not in clusters Optical studies show that environment acts well before reaching the dense cluster environment (Dressler 1980, Lewis et al 02, Gomez et al 03...) HI stripping in Virgo galaxies Chung et al. (2009) Clusters are rare! Only 10% of local galaxies reside in clusters. What about groups? Adapted from Dressler (1980) HI deficient galaxies found sometimes also in groups (e.g. Verdes-Montenegro et al. 2001, Kilborn et al. 2009)
This talk is about... Probing galaxy evolution across environments using gas fraction scaling relations Take home messages: The study of environmental effects on gas require large samples and enough sensitivity to probe the gas-poor regime We now have clear statistical evidence that HI is removed in the group environment
GASS: The GALEX Arecibo SDSS Survey Targeted HI survey: ~800 galaxies with homogeneously measured M, SFR and gas properties. Arecibo large program (2008-2012). Volume-limited: 0.025< z <0.05 Stellar mass selected: 10< log M /M <11.5 Gas fraction limited: MHI/M > 1.5% Red sequence GASS reference paper: Catinella, Schiminovich et al 2010 HI det non-det All data (incl. HI spectra) available at: www.mpa-garching.mpg.de/gass/ Blue sequence
Gas content vs structural / SF properties of galaxies Log MHI/M det non-det Stellar Mass Stellar Mass Surface Density, M /2πR50 2 Color (SFR/M ) Catinella et al. 2010, 2012b & 2013 HI mass fraction most tightly correlated with µ and NUV-r
Probing the gas-poor regime HI-blind surveys such as ALFALFA (Giovanelli et al 2005) are too shallow to detect HI-poor galaxies at their median redshift... ALFALFA GASS Huang et al. (2012) Two solutions: (1) deeper HI targeted surveys (such as GASS) (2) stacking of HI-blind surveys
(1) GASS: HI content (and SF) suppressed in groups! HI MH < 10 13 M ssfr Virgo (HRS) MH = 10 13-10 14 M Catinella, Schiminovich, Cortese et al. 2013 First statistical evidence for suppression of HI gas at fixed stellar mass in groups with halo mass MH 10 13 M Extend to lower stellar mass and larger samples. Need to probe gas-poor regime and variety of environments. Stacking science.
HI stacking Bin galaxies by e.g. M extract HI spectra at known positions, z align in velocity, co-add and measure signal Log MHI/M GASS HI STACKING ALFALFA (Giovanelli et al 2005) ~5000 galaxies, log M /M > 10 HI stacking well reproduces GASS scaling relations Log Stellar Mass Fabello, Catinella et al. 2011
The power of stacking Toby Brown s PhD Thesis at Swinburne ALFALFA stacking, HI detections only ALFALFA stacking, full sample GASS Stellar mass selected sample of 30,000 galaxies: log M /M =9-11.5, z=0.01-0.05 See Toby s poster!
(2) ALFALFA stacking Toby Brown s PhD Thesis at Swinburne large groups Virgo (HRS) Field+small groups (Mh<10 13 M ) MH = 10 11.5-10 13 M Large groups (10 13 <Mh<10 14 M ) MH = 10 13-10 14 M Clusters (Mh>10 14 M ) MH = 10 14-10 15 M Virgo Cluster (LC et al. 2011) field/small groups Gas removed in groups with MH > 10 13 M clusters Stellar mass selected sample of 30,000 galaxies: log M /M =9-11.5, z=0.01-0.05 See Toby s poster!
Summary We cannot understand galaxies without knowing about their gas component Galaxy properties depend on mass, environment is second order environmental comparisons must be done at fixed stellar mass The study of environmental effects on gas require large samples and enough sensitivity to probe the gas-poor regime First statistical evidence for gas depletion in the group environment
J Thanks! J Background image: Hickson 44 Galaxy Group (NASA APOD)