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HI in galaxies at intermediate redshifts Philip Lah (ANU) Frank Briggs (ANU) Matthew Colless (AAO) Roberto De Propris (CTIO) Michael Pracy (ANU) Erwin de Blok (ANU) Jayaram N Chengalur NCRA/TIFR Evolution of Wgas Star formation Rate Cold gas density SDSS DLAS Very limited constraints on the gas content (i.e. raw material Ly-a line not observable from for star formation) exist in the redshift range in which the star the earth HIPASS HI emission survey formation shows very rapid evolution at z =rate 0 (Zwaan et al. 2005 ) Sensitivity Issues – need for SKA The flux from an MHI* galaxy at z ~ 1 is M HI 200km / s 6.2 103 Mpc 1 z S 7 Jy ( )( )( )( ) 9 6 10 M sun V DL 2 The time required to make a 3s detection with the GMRT is 9000hr ( Tsys / 70 K ( N / 30)(G / 0.25K / Jy)( S / 7 Jy) )2 ( 200km / s ) V 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 Proof of concept A3128 • Naively if one co-adds the HI emission signal from N galaxies, the SNR should improve by N½ – 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” Begum, Chengalur, Karachentsev et al. (2008) A3128 • A 3128 is a z ~ 0.06, richness class 3, Bautz-Morgan type I-II cluster Chengalur et al. 2001 (also Zwaan et al. 2001) All late types • 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 • MHI = 16.7 ± 2.6 • MHI = 8.6 ± 2 (late type, outer) (all galaxies) Late types outside X-ray contours Control Sample The Subaru field Fujita et al. (2003), narrow band Ha imaging at z ~0.24 Narrow band Ha selected galaxies 24’ × 30’ Fujita et al. 2003 did a narrow band imaging survey for Ha emission at z=0.24 Total of 348 galaxies in the sample Ha at z = 0.24 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. 1 km x 1 km • Hybrid configuration • 14 dishes in central compact array • Remaining along 3 “Y” Low and high angular resolution arms GMRT images of CH3CHO • Allows one to emission from Sgr B2 (Chengalur simultaneously make & Kanekar 2003) made from a low and high resolution single GMRT observation. images 14 km 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 DHI Dopt relation from Broeils & Rhee (1997) Stacked HI Spectrum and WHI 121 redshifts - weighted average MHI = (2.26 ± 0.90) ×109 M GMRT Measurement Star Formation Rate at z = 0.24 shows same correlations as for z=0 galaxies SFR vs MHI z = 0 relation from Doyle & Drinkwater (2006) 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 followup with the AAT GMRT ~34 hours on cluster AbellAbell 370370galaxy cluster galaxy cluster Extent of X-ray gas 324 galaxies 105 blue (B-V 0.57) R200 radius at which cluster 200 times denser than the general field 219 red (B-V > 0.57) redshift histogram 324 useful redshifts GMRT sideband frequency limits HI all spectrum 324 redshifts (all available) MHI = (6.6 ± 3.5) ×109 M HI Mass in the inner regions of clusters HI mass within 2.5 Mpc of cluster centers A 370 has substantially more HI mass than the comparable richess Coma cluster HI mass to luminosity ratios 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 vs Star Formation Rate in Abell 370 all 168 [OII] emission galaxies Average line from Doyle & Drinkwater 2006 Summary • Galaxies in A370 (z ~ 0.37, Tlookback ~ 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 156 galaxies 168 galaxies 110 galaxies 214 galaxies A3128: Inhomogeneous distribution of gas rich galaxies Gas Rich Co-added spectra of the most gas rich group MHI ~ 26 x 109 Msun Gas Poor