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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 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 Star forming galaxies Radio – IR correlation M82 1 . 4 G H z 2 0 Condon 1992 c m 1 . 4 G H z z ~ 5 Bell 2003 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 Cosmic star formation history 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) Star formation rate density [M / yr / Mpc3] AGN feedback 1. QUASAR MODE 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 - 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 Faber et al. 2007 Allows good reproduction of observed galaxy properties Croton et al. 2006; Bower et al. 2006; Sijacki et al. 2006, Hopkins et al. 2006… Different phases of galaxy merger (gas); MPA galaxy cluster MS0735.6+7421 (z=0.2); white = HST, blue = Chandra, red = VLA; NASA.gov 2. Radio mode 1. Quasar mode Allows good reproduction of observed galaxy properties 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 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 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) Differential 20 cm source counts (norm. to Euclidian space) star forming gals + low-power AGN Robust SF/AGN classfier needed !!! n S2.5 (sr-1 Jy1.5) sub-mJy radio population: Bondi et al. (2008) FIRST / NVSS S (mJy) Cambridge The COSMOS Survey 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) 5σ depth for all existing data and the expected 5σ depth for upcoming or ongoing guaranteed time observations Radio view of COSMOS field: VLA-COSMOS 20 cm survey NRAO Very Large Array VLA-COSMOS core team: Schinnerer, Smolčić, Carilli, Bondi, Ciliegi, Scoville, NRAO Very Large Array Bertoldi, Blain, Impey, Jahnke, Koekemoer, Le Fevre, Urry, Martínez Sansigre, Wang, Datta, Riechers VLA-COSMOS team: Schinnerer (PI) Smolcic, Bondi, Ciliegi, Scoville, Large projectCarilli, (275hr) : Schinnerer et al. (2004, 2007) Bertoldi, Blain, Impey, Jahnke, ~ 2,400 sources (catalogKoekemoer, - public) O Le Fevre, Martinez Wang, Datta ~ 2 □Urry, ; mean rms Sansigre, ~ 10 Jy/beam, 1.5” resolution unique complementary COSMOS data set enabling Pilot project (10hr): A array evolution (Schinnererthrough et al. 2004) studies of AGN/SF cosmic times ~ 250 sources (catalog - public) ~ 1 sqrdeg; rms ~et 30al. Jy/beam Deep project (62hr): Schinnerer (to be submitted) ~ 1 □O; rms ~ 7 Jy/beam Large project (275hr): A+C array (Schinnerer et al. 2007) ~ 3,642 sources (catalog - public) 327 MHz project (24hr): Smolčić et al. (in prep) O sqrdeg; rms ~ 15(10) Jy/beam; ~ 2 □~ 2(1) ; rms ~ 0.5mean mJy/beam Deep project (62hr): A array ~ 1 sqrdeg; rms ~ 7-8 Jy/beam (central 30’) What have we (so far) learned from VLA-COSMOS? The composition of the sub-mJy radio population @ z≤1.3: ~ 350 SF & ~ 600 AGN gals. Baldwin-Phillips-Terlevich (1981) diagram Differential 20 cm source counts n S2.5 (sr-1 Jy1.5) 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 FIRST / NVSS Cambridge S (mJy) Bondi et al. (2008) 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, 14) Kauffmann et al. (2003), Kewley et al. (2001,2006), Obrić et al. (2006), Smolčić et al. (2006, 2008a) The radio - (F)IR correlation - 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 Future work: Little or no evolution of the IR/radio ratios at least out to z~1 Smolčić et al. (2008); Sargent et al. (in prep) - 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 The dust-unbiased cosmic star formation history @ z≤1.3 from the VLA-COSMOS survey Good agreement between VLA-COSMOS and 20cm lumiosity functions for VLA-COSMOS star forming galaxies (blue) Cosmic star formation history previous radio results (1 order of magnitude smaller sample; Haarsma et al. 2000) other SFRD estimates from Hα, OII, UV, IR with dust correction applied where needed Dust attenuation at intermediate redshifts is well understood Smolčić et al. (2009, ApJ, 690, 610) Probing SFRs at high z via stacking COSMOS Lyman break galaxy sample of Lee, Capak et al. Stacking detection: U band drop-outs (2.5 < z < 3.5) Median flux: 0.90 ± 0.21 μJy <SFRradio> = 31 ± 7 MSUN/yr <SFRUV> ~ 17 MSUN/yr dust attenuation factor ~1.8 << standard attenuation factor of 5 Star formation history derived from UDS/UKIDSS BzK selected galaxies stacked in radio (Dunne et al. 2008) (Steidel et al. 1999, Adelberger & Steidel 2000, Reddy & Steidel 2004) Carilli et al. (2008; ApJ, 689, 883) Dust attenuation at high redshifts may be smaller than at lower redshifts c The evolution of VLA-COSMOS (weak) radio AGN Ledlow & Owen (1996) FRI / FRII diagnostic plot for VLA-COSMOS AGN 20cm lumiosity functions for VLACOSMOS AGN (red) Qualitative agreement between cosmological model and observations is very encouraging for the idea of ‘radio mode’ feedback Smolčić et al. (ApJ, sub.) Volume averaged mechanical heating rate Comoving BH accretion rate density 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 VLA-COSMOS Large Project limits EVLA-COSMOS: Deeper 20 cm imaging: probing radio LIRGs (>10 MSUN/yr) through cosmic time complete sample of ULIRGs (>100 MSUN/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