The VLA-COSMOS survey: Tracing star-forming and AGN galaxies through cosmic time Vernesa Smolčić (Caltech) E. Schinnerer (MPIA), C.L. Carilli (NRAO), M. Bondi (INAF), P. Cilliegi (INAF), G. Zamorani (INAF), K. Jahnke (MPIA), M. Sargent (MPIA) & the (VLA-)COSMOS collaboration

Radio emission at 1.4 GHz (20cm) Dominated by synchrotron radiation Dominated by synchrotron radiation Two dominant populations in extragalactic radio surveys: Two dominant populations in extragalactic radio surveys: 1 Star forming (SF) galaxies Radio emission is not sensitive to dust 2 Active galactic nuclei (AGN) Radio emission directly traces the population of low radio power AGN, deemed important for galaxy formation Condon 1992

1.4 GHz 20 cm1.4 GHz 20 cm 1.4 GHz z ~ 51.4 GHz z ~ 5 M82 Thermal (free-free) emission (radio) Thermal dust emission (FIR) Synchrotron emission (radio) Condon 1992 van der Kruit 1971; Helou et al. 1985; Condon et al. 1992, Yun et al. 2001; Bell 2003; Obric et al. 2006; Mauch & Sadler 2007 Bell 2003 Radio – IR correlation Star forming galaxies

Star formation rate density [M  / yr / Mpc 3 ] Short-wavelength radiation (e.g. UV) sensitive to dust  radio emission overcomes this bias Compilation based on different star formation estimators (Hα, OII, UV; Hopkins 2004 ) Cosmic star formation history

AGN feedback AGN feedback Faber et al galaxy cluster MS (z=0.2); white = HST, blue = Chandra, red = VLA; NASA.gov 1.QUASAR MODE -Merger driven -Vigorous BH mass growth -Qusar wind gas expells gas out of the galaxy’s center  termination of quasar & starburst phase -Not necessarily linked to radio outflows 2. RADIO MODE - Once a static hot gas halo forms around the galaxy - Modest BH mass growth - Radio outflows heat surrounding gas  truncation of further stellar mass growth Allows good reproduction of observed galaxy properties Different phases of galaxy merger (gas); MPA Croton et al. 2006; Bower et al. 2006; Sijacki et al. 2006, Hopkins et al. 2006…

Allows good reproduction of observed galaxy properties 1. Quasar mode 2. Radio mode Luminosity function of galaxies Croton et al. 2006

Croton et al. 2006: mean BH accretion rate per unit volume averaged over the entire simulation This theoretically derived curve can directly be inferred from radio observations

HOWEVER HOWEVER Deep radio data (rms<15μJy/beam) of a large sample needed !!!

The faint (<1 mJy) radio population 1.4 GHz (20 cm) differential radio source counts (normalized to Euclidian space) flatten below 1 mJy 1.4 GHz (20 cm) differential radio source counts (normalized to Euclidian space) flatten below 1 mJy  rise of a new population not contributing significantly at higher flux levels  rise of a new population not contributing significantly at higher flux levels The composition of this faint radio population is highly controversial (Seymour et al. 2004, 2008, Simpson et al. 2006, Fomalont et al. 2007, Padovani et al. 2007, Smolcic et al. 2008, Kellermann et al. 2008) The composition of this faint radio population is highly controversial (Seymour et al. 2004, 2008, Simpson et al. 2006, Fomalont et al. 2007, Padovani et al. 2007, Smolcic et al. 2008, Kellermann et al. 2008) Bondi et al. (2008) S (mJy) n S 2.5 (sr -1 Jy 1.5 ) FIRST / NVSSCambridge Differential 20 cm source counts (norm. to Euclidian space) sub-mJy radio population: star forming gals + low-power AGN !!!  Robust SF/AGN classfier needed !!!

The COSMOS Survey

COSMOS overview (Scoville et al. 2007)  2 □ O equatorial field  X-ray to radio imaging (~30 bands)  galaxy photo-z accuracy, 0.7% (Ilbert et al 2008)  quasar photo-z accuracy, 1.5% (Salvato et al. 2008)  spectroscopy (VLT-VIMOS + Magellan-IMACS) The COSMOS survey 5σ depth for all existing data and the expected 5σ depth for upcoming or ongoing guaranteed time observations

VLA-COSMOS 20 cm survey NRAO Very Large Array NRAO Very Large Array VLA-COSMOS team: Schinnerer (PI) Smolcic, Carilli, Bondi, Ciliegi, Scoville, Bertoldi, Blain, Impey, Jahnke, Koekemoer, Le Fevre, Urry, Martinez Sansigre, Wang, Datta Pilot project (10hr): A array (Schinnerer et al. 2004) ~ 250 sources (catalog - public) ~ 1 sqrdeg; rms ~ 30  Jy/beam Large project (275hr): A+C array (Schinnerer et al. 2007) ~ 3,642 sources (catalog - public) ~ 2(1) sqrdeg; mean rms ~ 15(10)  Jy/beam; Deep project (62hr): A array ~ 1 sqrdeg; rms ~ 7-8  Jy/beam (central 30’) Radio view of COSMOS field: NRAO Very Large Array NRAO Very Large Array VLA-COSMOS core team: Schinnerer, Smolčić, Carilli, Bondi, Ciliegi, Scoville, Bertoldi, Blain, Impey, Jahnke, Koekemoer, Le Fevre, Urry, Martínez Sansigre, Wang, Datta, Riechers Large project (275hr) : Schinnerer et al. (2004, 2007) ~ 2,400 sources (catalog - public) ~ 2 □ O ; mean rms ~ 10  Jy/beam, 1.5” resolution unique complementary COSMOS data set enabling studies of AGN/SF evolution through cosmic times Deep project (62hr): Schinnerer et al. (to be submitted) ~ 1 □ O ; rms ~ 7  Jy/beam 327 MHz project (24hr): Smolčić et al. (in prep) ~ 2 □ O ; rms ~ 0.5 mJy/beam

What have we (so far) learned from VLA-COSMOS?

The composition of the sub-mJy radio population Bondi et al. (2008) S (mJy) n S 2.5 (sr -1 Jy 1.5 ) Differential 20 cm source counts FIRST / NVSSCambridge Baldwin-Phillips-Terlevich (1981) diagram Kauffmann et al. (2003), Kewley et al. (2001,2006), Obrić et al. (2006), Smolčić et al. (2006, 2008a) New rest-frame color-based method for separating SF from low-luminosity AGN galaxies (i.e. Seyfert, LINERs; Smolčić et al. 2008a)  applied to VLA-COSMOS data Sub-mJy radio population: 1) not dominated by star forming galaxies 2) fair mix of SF and (low-L) AGN galaxies Smolčić et al. (2008; ApJS; 177, z≤1.3: ~ 350 SF & ~ 600 AGN gals.

The radio - (F)IR correlation Current focus on (Sargent et al., in prep.): Current focus on (Sargent et al., in prep.): - quantification of selection effects in view of future deep EVLA & Herschel data - statistically sound treatment of flux limits using survival analysis  evolution of radio-IR relation for star forming systems out to z~1  evolution of radio-IR relation for star forming systems out to z~1 Future work: - Effects of environment (E. Murphy et al., in prep) - separation of star forming systems into different classes of objects (e.g. optical morphology, mass) - stacking of radio population at faint IR fluxes Little or no evolution of the IR/radio ratios at least out to z~1 Smolčić et al. (2008); Sargent et al. (in prep)

The dust-unbiased cosmic star formation z≤1.3 from the VLA-COSMOS survey Good agreement between VLA-COSMOS and Good agreement between VLA-COSMOS and previous radio results (1 order of magnitude smaller sample; Haarsma et al ) previous radio results (1 order of magnitude smaller sample; Haarsma et al ) other SFRD estimates from Hα, OII, UV, IR other SFRD estimates from Hα, OII, UV, IR with dust correction applied where needed with dust correction applied where needed Smolčić et al. (2009, ApJ, 690, 610) Dust attenuation at intermediate redshifts is well understood 20cm lumiosity functions for VLA-COSMOS star forming galaxies (blue) Cosmic star formation history

The dust-unbiased cosmic star formation history for star forming ULIRGs The dust-unbiased cosmic star formation history for star forming ULIRGs (~100 M sol /yr) VLA-COSMOS star forming ULIRGs : VLA-COSMOS star forming ULIRGs : Flatter evolutionary curve compared to IR derived (Le Floc’h et al. 2005) : possibly partially due to AGN contribution at IR wavelengths Flatter evolutionary curve compared to IR derived (Le Floc’h et al. 2005) : possibly partially due to AGN contribution at IR wavelengths Caputi et al. (2007): contribution of AGN dominated ULIRGs in MIR samples higher at z=2 than at z=1 Caputi et al. (2007): contribution of AGN dominated ULIRGs in MIR samples higher at z=2 than at z=1 Smolčić et al. (2009; ApJ, 690, 610) Star formation rate density at z>1 may not be dominated by star forming ULIRGs

Probing SFRs at high z via stacking COSMOS Lyman break galaxy sample of Lee, Capak et al. Carilli et al. (2008; ApJ, 689, 883) Stacking detection: U band drop-outs (2.5 < z < 3.5) Median flux: 0.90 ± 0.21 μJy = 31 ± 7 M SUN /yr = 31 ± 7 M SUN /yr ~ 17 M SUN /yr ~ 17 M SUN /yr  dust attenuation factor ~1.8 << standard attenuation factor of 5  dust attenuation factor ~1.8 << standard attenuation factor of 5 (Steidel et al. 1999, Adelberger & Steidel 2000, Reddy & Steidel 2004) Dust attenuation at high redshifts may be smaller than at lower redshifts Star formation history derived from UDS/UKIDSS BzK selected galaxies stacked in radio (Dunne et al. 2008) c

The evolution of VLA-COSMOS (weak) radio AGN Smolčić et al. (ApJ, sub.) Volume averaged mechanical heating rate Comoving BH accretion rate density 20cm lumiosity functions for VLA- COSMOS AGN (red) Ledlow & Owen (1996) FRI / FRII diagnostic plot for VLA-COSMOS AGN Qualitative agreement between cosmological model and observations is very encouraging for the idea of ‘radio mode’ feedback

Summary & EVLA outlook VLA-COSMOS:  Composition of sub-mJy radio population: fair mix of SF and low-power AGN galaxies  z ≤1.3:  Cosmic evolution of VLA-COSMOS SF and AGN galaxies  First observational insight into ‘radio mode’ feedback beyond the local universe  z ~ 3: stacking down to 1μJy levels that EVLA will be able to observe EVLA-COSMOS:  Deeper 20 cm imaging:  probing radio LIRGs (>10 M SUN /yr) through cosmic time  complete sample of ULIRGs (>100 M SUN /yr) out to high z  probing weak radio AGN out to high z  testing cosmological models  6 cm imaging:  high resolution: radio morphology, composite objects  spectral indices  probing thermal (free-free) radio emission for z>3.5 VLA-COSMOS Large Project limits