HI in galaxies at intermediate redshifts Jayaram N Chengalur NCRA/TIFR Philip Lah (ANU) Frank Briggs (ANU) Matthew Colless (AAO) Roberto De Propris (CTIO) Michael Pracy (ANU) Erwin de Blok (ANU)

Evolution of  gas Cold gas density Star formation Rate HIPASS HI emission survey at z = 0 (Zwaan et al ) Ly -  line not observable from the earth SDSS DLAS Very limited constraints on the gas content (i.e. raw material for star formation) exist in the redshift range in which the star formation rate shows very rapid evolution

Sensitivity Issues – need for SKA The flux from an M HI * galaxy at z ~ 1 is The time required to make a 3  detection with the GMRT is Clearly a much larger sensitivity is needed, i.e. the SKA

What can one do now? The volume of space observed by the GMRT telescope in a single observation ~ (FoV x Bandwidth) could contain ~ 100 or more bright galaxies One could try to detect the average HI emission of all of these galaxies by stacking Stacking requires one to know the position and redshift of all galaxies

Naively if one co-adds the HI emission signal from N galaxies, the SNR should improve by N ½ –Redshift measurement errors lead to errors in aligning HI spectra –Unknown HI mass of each galaxy leads to non optimal weights while co-adding HI mass depends on morphological type, optical diameter. –Unknown HI extent of each galaxy also leads to non optimal SNR HI diameter correlates with optical diameter. Low redshift cluster A3128 observed as “proof of concept ” Proof of concept A3128 Begum, Chengalur, Karachentsev et al. (2008)

A3128 A 3128 is a z ~ 0.06, richness class 3, Bautz-Morgan type I-II cluster Redshifts available for 193 galaxies, of which 148 lie inside the ATCA cube Co-added emission detected from cluster galaxies. Late type galaxies located outside the X-ray contours have the highest HI content M HI = 16.7 ± 2.6 (late type, outer) M HI = 8.6 ± 2 ( all galaxies) All late typesControl Sample Late types outside X-ray contours Chengalur et al (also Zwaan et al. 2001)

The Subaru field Fujita et al. (2003), narrow band H  imaging at z ~0.24

Narrow band H  selected galaxies H  at z = ’ × 30’ Fujita et al did a narrow band imaging survey for H  emission at z=0.24 Total of 348 galaxies in the sample

The Giant Meterwave Radio Telescope (GMRT) Aperture Synthesis Radio Telescope (interferometer) 30 Antennas each 45m in diameter About 70 km N of Pune, 160 km E of Mumbai. Hybrid configuration 14 dishes in central compact array Remaining along 3 “Y” arms Allows one to simultaneously make low and high resolution images 14 km 1 km x 1 km Low and high angular resolution GMRT images of CH 3 CHO emission from Sgr B2 (Chengalur & Kanekar 2003) made from a single GMRT observation.

GMRT Observations 121 galaxies within the GMRT data cube Total of ~ 40 hours of on source time Most of these galaxies are fainter than L * (i.e. low HI mass) Redshifts obtained using the 2dF instrument on the AAT Optical imaging with the ANU 40” telescope. Smoothing sized fixed using D HI - D opt relation from Broeils & Rhee (1997)

Stacked HI Spectrum and  HI 121 redshifts - weighted average M HI = (2.26 ± 0.90) ×10 9 M  GMRT Measurement

Star Formation Rate at z = 0.24 shows same correlations as for z=0 galaxies z = 0 relation from Doyle & Drinkwater (2006) SFR vs M HI SFR vs Radio Continuum z = 0 relation from Sullivan (2001)

Abell 370 a Galaxy Cluster at z = 0.37

Abell 370, a galaxy cluster at z = 0.37 large galaxy cluster of order same size as Coma optical imaging ANU 40 inch telescope spectroscopic follow- up with the AAT GMRT ~34 hours on cluster

Abell 370 galaxy cluster 324 galaxies 105 blue (B-V  0.57) 219 red (B-V > 0.57) Abell 370 galaxy cluster Extent of X-ray gas R 200  radius at which cluster 200 times denser than the general field

redshift histogram 324 useful redshifts GMRT sideband frequency limits

HI all spectrum 324 redshifts (all available) M HI = (6.6 ± 3.5) ×10 9 M 

HI mass within 2.5 Mpc of cluster centers HI Mass in the inner regions of clusters A 370 has substantially more HI mass than the comparable richess Coma cluster

HI Mass to Light Ratios HI mass to optical B band luminosity for Abell 370 galaxies Uppsala General Catalog Local Super Cluster (Roberts & Haynes 1994) HI mass to luminosity ratios

HI Mass vs Star Formation Rate in Abell 370 all 168 [OII] emission galaxies line from Doyle & Drinkwater 2006 Average

Summary Galaxies in A370 (z ~ 0.37, T lookback ~ 4 Gyr) have significantly more gas than those in the similar size nearby Coma cluster A370 shows similar trends as for nearby clusters, e.g. –decrease in HI mass for central galaxies –Correlation of SFR with total HI content –Calibration between O[II] derived SFR and radio continuum derived SFR is the same as in the local universe At the observed SFR, A370 will evolve into a gas poor cluster like Coma by z ~ 0 Co-adding is a powerful method to study the HI content of star forming galaxies, galaxy evolution in clusters, substructure in clusters etc.

Thank you

HI mass 324 galaxies 219 galaxies 105 galaxies 94 galaxies 168 galaxies 156 galaxies 110 galaxies 214 galaxies

A3128: Inhomogeneous distribution of gas rich galaxies Gas Rich Gas Poor Co-added spectra of the most gas rich group M HI ~ 26 x 10 9 Msun