1. December 17, 2008 The EVLA Vision Galaxies Through CosmicTime 1 Microjansky Radio Sources: AGN or Star Formation? Ken Kellermann & EdFomalont NRAO in collaboration with Neal Miller, Paolo Padovani, Vincenzo Mainieri, Paolo Tozzi

2. December 17, 2008 The EVLA Vision Galaxies Through CosmicTime 2 Star-formation, AGN, or ? History of star and BH formation similar –Does star formation trigger BH formation? –Do BH’s trigger star formation? –Is there a common underlying cause? –Jet feedback? + or - No single criteria to distinguish AGN & SF –UV/Optical observations Morphology, spectra Obscuration –FIR observations Good tracer of star formation Limited sensitivity/resolution –X-ray observations Good tracer of AGN Weak x-ray emission from star formation –Radio observations AGN and SF detectable to large z See through gas and dust Morphology/T b (resolution) Spectra (α > -0.4 indicates AGN) (S α ν α ) Polarization, Variability No redshift Quasars Star formation rate Shaver et al., 1999 Hopkins & Beacon, 2007

3. December 17, 2008 The EVLA Vision Galaxies Through CosmicTime 3 Chandra Deep Field South 1 (2) Msec exposure 366 X-ray sources 5 x 10 -17 ergs/sec Extended CDFS 250 ks per field 16 arcmin Hubble UDF 976 ks exposure B, V, I, z 10,000 galaxies mag 29 GOODS ACS B, V, I, z < 28 GEMS/ACS, VLT/FORS ESO2.2m/WFI VLA data (30% sensitivity level) Spitzer – IRAC/MIPS

4. December 17, 2008 The EVLA Vision Galaxies Through CosmicTime 4 CDFS - 20 cm VLA image 266 radio sources in CDFS – σ = 8.5 μJy – S > 43 μJy – < 0.5 arcsec position accuracy 89 have X-ray counterparts

5. December 17, 2008 The EVLA Vision Galaxies Through CosmicTime 5 Optical/X-ray Counterparts in the VLA CDFS 254 O/IR counterparts – 10 Radio galaxies – AGN + SFR – 107 spectroscopic redshifts – 79 photo z’s (17 bands) – 12 Sources remain unidentified 9 are ambiguous 3 no counterpart at any λ – OIR quiet

6. December 17, 2008 The EVLA Vision Galaxies Through CosmicTime 6 RID-97 R_WFI R> 25.5 b> 27.5v> 27.5 K> 24.4

7. December 17, 2008 The EVLA Vision Galaxies Through CosmicTime Radio Loud- 63% R=log(S r /S o) RL AGN RQ AGN

8. December 17, 2008 The EVLA Vision Galaxies Through CosmicTime 8 Large scatter in μJy count Cosmic variance? NO! Instrumental errors – N(S) depends on instrument! – incompleteness – primary beam, bandwidth, time smearing corrections – Statistical weight corrections – Resolution corrections Fomalont et al 2008 ApJ S 179, 71 Padovani et al. ApJ submitted L x > 10 42 W/Hz R < 1.4 Star forming galaxies R < 1.7 L r < 10 24.5 W/Hz Not E galaxy L x not > 10 42 ergs/sec

9. December 17, 2008 The EVLA Vision Galaxies Through CosmicTime 9 θ = 3.5 arcsec θ = 13.3 arcsec Miller et al., unpublished Kellermann et al. ApJS, v179, 90 Chandra Deep Field South – VLA 20 cm: S > 55 μJy

10. December 17, 2008 The EVLA Vision Galaxies Through CosmicTime 10 Resolution vs. confusion Resolution < few asec to avoid confusion at 20 cm If the nanoJy population has dimensions of ∼ 1 arcsec, natural confusion may be a limiting factor VLA+MERLIN Muxlow et al. MNRAS 358, 1159

11. December 17, 2008 The EVLA Vision Galaxies Through CosmicTime 11Summary Classification as SF or AGN – Radio and X-ray Luminosity – Ratio radio/optical flux density – Optical morphology and spectra reaching faint magnitudes μJy radio population includes RQ and RL AGN and SFG SF & BH probably co-exist There is no “correct” resolution to use for EVLA deep surveys – Good compromise ≈ 1 arcsec (35 km at 2.5 GHz) – 0.1 arcsec (300 km) to image sub-microJy sources (EVLA+eMERLIN) – 0.01 arcsec (3000 km) to distinguish between SF and AGN (VLBA +EVN) AGN: T b > 10 5 for 1 μJy Issues for the EVLA and for design of the SKA – Determine the submicroJy source density - confusion – Angular structure – natural confusion? – The importance of cosmic variance – Optimum frequency for studying faint radio sources – Very high dynamic range (~ 10 5) needed if EVLA is to reach the thermal noise limits in a few hundred hours Primary beam Pointing stability Source spectra Variability

12. December 17, 2008 The EVLA Vision Galaxies Through CosmicTime 12 CDFS/ECDFS 20 & 6 cm CDFS – I. Kellermann et al., ApJS, 179, 90 (CDFS – VLA) 8 μ σ ∼ Jy, θ ~ 3.5 arsec – II. Mainieri et al. ApJS, 179, 95 (CDFS – optical) – III. X-ray sources, Tozzi et al. ApJ, (submitted) – IV. Population Studies, Padovani et al. ApJ, in press – V. Fomalont et al., 6 cm, σ ∼ 5 μJy, θ ~ 3.5 arcsec (in prep) – VI. CDFS, Miller et al., 20 cm, σ ∼ 10 μJy, θ ~ 13 arcsec (in prep) 20 cm ECDF – Miller et al. ApJS, 179, 105 σ ∼ 8 μJy, θ ~ 2 arcsec (S >55 μJy) – Miller et al., 20 cm, θ ~ 2 arcsec (in prep) σ ∼ 7 μJy, θ ~ 2 arcsec (S > 35 μJy)