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Star formation at high redshift (2 < z < 7) Methods for deriving star formation rates •UV continuum = ionizing photons (dust obscuration?) •Ly a = ionizing photons (dust obscuration?) •Far IR = bolometric (covering factor?) •Radio continuum (synchrotron) = empirical (radio – FIR correlation?) •Radio free-free/RRLs = ionizing photons (sensitivity, spectral confusion?) •All relate mostly to massive stars (> 5 M_sun) => total SFR depends on extrapolation of IMF, and temporal behavior Cosmic (proper) time Radio-FIR correlation: tightest correlation in extragalactic astronomy Separating FF – Synch is difficult M82 Synch. Free-free Thermal dust SKA in context EVLA z=8 Cosmic ‘background’: ½ starlight reprocessed by dust Madau-Lilly plot: evolution of cosmic star formation rate density Evolution of space density of luminous QSOs (Fan et al. 2003) Galaxy populations at high redshift (2 < z < 7) •Radio galaxies: only z > 0.5 galaxies before 90’s •UV dropouts/Ly-break: broadband colors •Ly a: narrow band imaging •Submm: (sub)mm bolometer camera imaging •QSO Hosts: HST, (sub)mm •QSO absorption lines: metalicity evolution, parent galaxies •z=0.3 to 2: EROs, faint blue, Butcher-Oemler, mJy radio sources, ISO •GRB hosts •Pop III stars: early reionization by 100 M_sun stars in minihalos at z = 20? High z radio galaxies (L_1.4 > 1e28 W/Hz) z=0.057 1954 z=3.8 1990 10kpc 10kpc z=0.49 1980 z = 5.2 2000 K-z relation: HzRGs = Giant Ellipticals z>8 radio galaxies? Alignment effect: Jet-induced star formation? Clumpy morphologies => forming ellipticals? 1138-262 z=2.2 Alignement effect: Radio-Xray 18kpc Radio-Lya halo Clustering on Mpc scales around HzRGs (1138-262 z=2.2) => protoclusters? Dusty radio galaxies at high z? Overdensity of submm galaxies? UV dropouts/Ly break (Ly a) Star formation rates in Ly break galaxies Extinction uncorrected corrected Correlation between extinction and SFR => L_UV is independent of SFR Ly break galaxies = highly biased (ie. clustered) galaxy formation Ly break galaxies with Ly a halos SUBMM galaxies: dust obscured galaxy formation HDF - optical HDF – 850 mm Dust obscured star formation dominates at z>2? Submm galaxies: L_FIR = 1e12 to 1e13 L_sun => SFR = 100 to 1000 M_sun /yr M_dust = 1e8-9 M_sun Magic of submm 350 GHz 250 GHz Brightest mm source in HDF: K = 23.5 Radio photometric redshifts: two colors, or ‘dropouts’ Redshift distribution Next step: photometric redshifts CO emission => M(H_2) = 1e10-11 M_sun Submm galaxies QSO host galaxies •Most low z spheroidal galaxies have SMBH •M_BH = 0.002 M_bulge => ‘Causal connection between SMBH and spheroidal galaxy formationn’ (Gebhardt et al. 2002)? z=6.4 2322+1944 30% of luminous QSOs have S_250 > 2 mJy L_FIR > 7e12 M_sun Dust heating: starburst or AGN? S_250=5.5mJy Radio-to-IR SED = M82 CO(1-0) w. VLA: L_FIR = 3e13 L_sun M(H_2) = 1e11 M_sun A Molecular Einstein Ring: VLA 45 GHz observations of CO2-1 emission from the gravitationally lensed QSO 2322+1944 at z=4.12 (Carilli et al. 2003) Keck Rband VLA CO2-1 2” Using the gravitational lens to probe sub-kpc scales in 2322+1944: A starburst disk surrounding a SMBH => coeval SMBH – galaxy formation? Optical QSO Starburst disk: molecular gas, dust, radio continuum Starbursts in QSO host galaxies? •30% of luminous QSOs (M_B < -27) have L_FIR = 1e13 L_sun (independent of redshift) •Z= 2 sample: All L_FIR luminous QSOs detected at 1.4 GHz, and in all cases ‘q’ consistent with star forming galaxy (2.3 +/- 0.3) Questions •Relationships between different high z galaxy types? •Halos masses and end-products (spirals, ellipticals)? •Is > 1000 M_sun/yr possible, sustainable (Heckman limit)? •IMF: top heavy? Star formation in extreme environments (P=100xISM)? Timescales? •Dust formation at z>6: >1e8 M_sun in < 0.7 Gyr? •What fraction of high z galaxy formation is dust-obscured? •Submm galaxies – redshift distribution? •radio – FIR correlation: mechanism? vs. redshift? •M-s relation – coeval SMBH and galaxy formation? •QSO dust heating: star formation or AGN? •L_FIR from S_250? •X = gas mass to CO luminosity conversion? L_FIR to dust mass conversion? •Pop III stars, minihalos, and first luminous objects: role of radio astronomy?
