The VLA-COSMOS survey: Tracing star-forming and AGN galaxies through cosmic time

1. 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

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

3. 1.4 GHz 20 cm 1.4 GHz z ~ 5 Star forming galaxies Radio – IR correlation M82 Synchrotron emission (radio) Thermal dust emission (FIR) Condon 1992 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 Thermal (free-free) emission (radio)

4. 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]

5. AGN feedback • 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 Faber et al. 2007 Croton et al. 2006; Bower et al. 2006; Sijacki et al. 2006, Hopkins et al. 2006… galaxy cluster MS0735.6+7421 (z=0.2); white = HST,blue = Chandra,red = VLA; NASA.gov Different phases of galaxy merger (gas); MPA

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

7. 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

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

9. 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) sub-mJy radio population: star forming gals + low-power AGN  Robust SF/AGN classfier needed !!! n S2.5 (sr-1 Jy1.5) FIRST / NVSS Cambridge S (mJy) Bondi et al. (2008)

10. The COSMOS Survey

11. 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

12. VLA-COSMOS 20 cm survey 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 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

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

14. The composition of the sub-mJy radio population 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 @ z≤1.3: ~ 350 SF & ~ 600 AGN gals. Differential 20 cm source counts Baldwin-Phillips-Terlevich (1981) diagram n S2.5 (sr-1 Jy1.5) 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) FIRST / NVSS Cambridge S (mJy) Bondi et al. (2008) Kauffmann et al. (2003), Kewley et al. (2001,2006), Obrić et al. (2006), Smolčić et al. (2006, 2008a)

15. 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: • 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)

16. The dust-unbiased cosmic star formation history @ z≤1.3 from the VLA-COSMOS survey Good agreement between VLA-COSMOS and • 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 20cm lumiosity functions for VLA-COSMOS star forming galaxies (blue) Cosmic star formation history Dust attenuation at intermediate redshifts is well understood Smolčić et al. (2009, ApJ, 690, 610)

17. 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 (Steidel et al. 1999, Adelberger & Steidel 2000, Reddy & Steidel 2004) Star formation history derived from UDS/UKIDSS BzK selected galaxies stacked in radio (Dunne et al. 2008) Carilli et al. (2008; ApJ, 689, 883) Dust attenuation at high redshifts may be smaller than at lower redshifts c

18. The evolution of VLA-COSMOS (weak) radio AGN 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 Smolčić et al. (ApJ, sub.) 20cm lumiosity functions for VLA-COSMOS AGN (red) Comoving BH accretion rate density Volume averaged mechanical heating rate

19. 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