The Stellar to Baryonic Mass Function of Galaxies: from SDSS to GAMA with ASKAP

Transcription

1 The Stellar to Baryonic Mass Function of Galaxies: from SDSS to GAMA with ASKAP SDSS: Sloan Digital Sky Survey GAMA: Galaxy And Mass Assembly survey ASKAP: Australian Square Kilometer Array Pathfinder Ivan Baldry (Liverpool JMU)

2 Credits BGD08 paper (IB, K. Glazebrook, S. Driver) GAMA team (SD, IB, S. Bamford, A. Hopkins, J. Liske, J. Loveday, P. Norberg, J. Peacock ) see for full team list ASKAP-DINGO project (M. Meyer, L. Staveley-Smith [UWA] )

3 The stellar mass density Assuming Ω b =0.045, H 0 =70, then Ω s /Ω b = 3.5% (Li & White 2009) (Chabrier IMF, SDSS data) 8.3% (Driver et al. 2007) (diet Salpeter IMF, Millennium Galaxy Catalog data) 4 to 8% (BGD08), 3 to 7% (Gallazzi et al. 2007) Uncertainties/considerations: IMF, priors, SP model, dust treatment definition (remaining versus formed stellar mass) corrections to galaxy total magnitudes volume corrections, cosmic variance

4 A solution for the sub-structure problem? applies to field galaxies as well. Photo-ionization suppresses the formation of small galaxies, so that surviving satellites are preferentially those that formed before the universe re-ionized [at z~6-10]. Benson, Frenk, Lacey, Baugh & Cole 2002

5 Sloan Digital Sky Survey NYU-VAGC sample galaxies <z<0.05 (Blanton et al. 2005) Photometry checked Flow corrections for z<0.02 e.g. impact discussed by Masters et al. 04 Stellar masses (Kauffmann et al. 03; Gallazzi et al. 05; KG; Panter et al. 07) Visibility volumes for each galaxy

6 Surface brightness (SB) limit Low completeness (> 23), as determined by Blanton et al BGD08

7 Field galaxy stellar MF lower limits At faint end, slopes of lines are -1.6 (dashed), -1.8 (dotted), -2.0, (for alpha 2 ). Dashed line is a double Schechter function fit to M>10 8 M solar data. Excess of faint galaxies above single Schechter fit seen in CfA2 and LCRS; Huchra 1999 BGD08

8 Distribution of stellar mass Fits only are shown. The double- Sch. function is a very good fit to the BGD08 data.

9 Estimating (cold) gas masses cf. Kannappan (2004), Zhang et al. (2009) BGD08

10 Baryonic Mass Functions scaled by Ω b /Ω m this paper solid line: using simple stars to stars+gas conversion (function of stellar mass) Bell et al BGD08

11 Galaxy And Mass Assembly (GAMA) [spectroscopy using AAOmega, the 2dF upgrade on the Anglo-Australian Telescope; with to come: VISTA (IR), VST (optical), Herschel (far-ir), GALEX (UV), ASKAP (21cm+) ]

12 GAMA primary science goals Group halo mass function Galaxy stellar (baryonic) mass function Merger rates Selection (~1000 / deg 2 ) r<19.4, 19.8 (SDSS) K<15.7 (17.5AB) (UK IR Telescope) & r<20.5 Area: 140 (250 planned) square degrees

13 IB et al in prep.

14 Halo mass function: using group finder, velocity dispersions, mock catalogues. PREDICTED Figure by P. Norberg

15 Preliminary GSMF Figure by S. Driver

16 Results from redshifts - projected to complete 120K n(z) for GAMA survey: next two slides focus on z<0.03 shown by red box.

17 Low-mass galaxies from mag-limited z surveys SDSS r<17.8 centi-l* galaxies GAMA r<19.8 milli-l* galaxies

18 Cyan oval shows objects consistent with being high-sb end of the low-l galaxy distribution. Yellow oval shows objects that are possibly star clusters or nucleated cores of galaxies.

19 Blind neutral Hydrogen surveys HI Parkes All-Sky Survey (HIPASS) finished ~10000 sources; 15 res. Arecibo Legacy Fast ALFA (ALFALFA) survey in progress ~25000 sources; 7000 sq. deg; 3.5 res. Australian SKA Pathfinder (ASKAP) from 201? Widefield ASKAP L-band Legacy All-sky Blind survey (WALLABY); > sources expected. Deep Investigation of Neutral Gas Origins (DINGO) (GAMA regions); 10 arcsec res.

20 Australian SKA Pathfinder PREDICTED M. Meyer et al. DINGO survey (and WALLABY survey) 10 resolution possible Measure baryonic MF down to ~ M solar at z<0.03

21 Conclusions/Summary Careful analysis of GSMF shows an upturn with slope -1.6 (or steeper) projected >0.1 galaxy Mpc -3 dex -1 (at ~ 10 7 M solar ) Implied galaxy baryonic MF has upturn with slope about -1.9 (possibly) Upturn is consistent with CDM and photoionization suppression model (?) New survey GAMA (r<19.4, 19.8): 140+ deg Deep g-to-k imaging to come from end of this year?

22 Extra Slides

23 M-L ratio limit in r<17.8 sample BGD08

24 Mr > galaxies in GAMA

25 Deep optical-ir imaging is still needed! SB limit implies missing galaxies and incorrect photometry Targeting everything fainter than 19.5 is very inefficient for z<0.05 dwarfs (and it is hard to get spectra) Optimised filters for 4000-A break, emission lines (+ J-K for stellar bump)

26 GAMA regions

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29 Galaxy Evolution versus Environment and Mass (with GAMA - over last 5 Gyr) GAMA Hopkins & Beacom 2006