Star Formation in High Redshift Submillimeter Galaxies and QSO Hosts Dieter Lutz MPE Elisabetta Valiante, Eckhard Sturm, Reinhard Genzel, Linda Tacconi, Mario Schweitzer, Andrew Baker, Hagai Netzer, Roberto Maiolino, Paola Andreani, Sylvain Veilleux Gas Accretion and Star Formation in Galaxies, September 14, 2007

Starburst/AGN co-evolution… Hopkins et al GOODS-S Hughes et al. 1998

This talk: Use rest frame mid-infrared spectroscopy to quantify current star formation and AGN activity in high z populations Spitzer QUEST Veilleux et al.

SMGs - a key phase of massive galaxy evolution Smail et al Genzel et al. 2003, Greve et al Swinbank et al Spitzer-IRS:  Redshifts  Energy Sources  Constraints on source structure (from SED)

Sample 13 bright objects from blank field or lens assisted SCUBA 850  m and MAMBO 1.2mm surveys – no radio pre-selection GO1 selection, not including Spitzer fluxes Accurate positions from radio or mm interferometry Wide range of optical/near-infrared counterpart brightnesses 6/13 with known optical redshifts Up to 2 hours per IRS low resolution order, to reach sub-mJy sensitivity Bertoldi et al Smail et al Ivison et al Cowie, Barger & Kneib 2002 Dannerbauer et al Frayer et al. 2000

IRS spectra Lutz et al ApJL 625, L83 Valiante et al ApJ 660,1060 z~2.8

IRS redshifts of SMGs Can be obtained at S 24  m <1mJy! 6 optical redshifts confirmed, within  z~ new PAH redshifts: 2.38, 2.73, sources remain without redshift – z>3.6? Median z~2.8 - support for an SMG median redshift modestly higher than the Chapman 05 value of 2.2 from optical spectroscopy Chapman et al. 2005

SMGs: Starburst and AGN Average SMG spectrum at z~2.7 (Valiante et al. 2007) Strong PAH emission: Luminosity star-formation dominated Additional AGN continuum: AGN typically 10-20% of luminosity, X-ray must be noticeably obscured …consistent with and extending to Compton-thick objects the X-ray based work of Alexander et al. See also Menendez-Delmestre et al (slightly different selection of SMGs)

ULIRG-like SEDs - consistent with compact (few kpc) sizes Bouche et al arXiv: Tacconi et al ApJ 8 SMGs median d(CO)<4kpc

Evidence for star formation in high z QSOs? Omont et al Walter et al. 2003, Maiolino et al. 2005

Elvis et al Local studies: What is the origin of QSO rest frame FIR emission? Rowan-Robinson (1995): Radiative transfer model of pure AGN SED Strong far-infrared (if observed) must be star formation Optical post-starburst signatures: e.g. Canalizo & Stockton 01, Kauffmann et al. 03 Sanders et al. 1989: warped disk could provide enough cold but AGN-heated dust Ho 2005: [OII] 3727 study - Little star formation, inhibited by QSO?

Average local PG QSO spectra: PAH emissions is widespread Schweitzer et al. 2006

Star formation tracers and QSO far-infrared emission correlate PAH/FIR and [NeII]/FIR Ratios in QSOs = Ratios in starbursting ULIRGs Star formation!

Reconstructing the intrinsic AGN SED Netzer et al ApJ 666, ~L Fir /L Bol = L SB /L Bol → Currently: Bulge growth rate ~ 20*BH growth rate *(η/0.1) Lifetime/Duty cycle of bright QSO short, or shifted 3μm bump Silicates

Using PAHs to quantify star formation in ‘Quasar epoch’ QSOs Spitzer-IRS studies: 12 QSOs 1.8<z<2.8 with robust submm/mm detections (e.g. Omont et al. 03, Priddey et al. 03, Barvainis & Ivison 02) –mm-bright end of the z~2.5 QSO population, but not extreme IR excess objects –Long integrations to individually measure PAH emission Cycle 3, Lutz et al ApJ 661, L25 and in preparation 25 QSOs 2<z<3.5 without mm preselection –Short integrations insufficient for individual PAH study, but meaningful stack Cycle 2, Maiolino et al A&A 468, 979

PAH detection in the z=2.56 Cloverleaf lensed QSO Lutz et al. 2007, ApJ 661, L25 Kneib et al L AGN ~ L Sun L SB ~ L Sun → SFR ~1000 M Sun /yr Gas exhaustion time yr

Star formation: PAH emission is consistent with rest frame FIR

Extrapolation to other luminous high-z QSOs Maiolino et al A&A 468, 979 PAH limit for average of 25 luminous 2<z<3.5 QSOs NOT preselected in the mm → SFR < 700 Msun/yr Schweitzer et al. PG QSOs Cloverleaf PAH detection strongly supports ~1000Msun/yr star formation rates in mm- detected high-z QSOs These have similar ratio of PAH (and FIR) to the AGN luminosity as local PG QSOs Bulk of z~2.5 QSO population has somewhat lower ratios of mm to AGN luminosity, typical SFRs will not exceed a few hundred Msun/yr Local relation between star formation and AGN luminosity must flatten at high L/high z)

Summary IRS spectroscopy of a small sample of SMGs suggests them to be z~2.8, dominated by luminous compact starbursts but with frequent coexisting minor AGN (sometimes Compton-thick). IRS spectroscopy detects strong star formation in the hosts of local PG QSOs, and massive ~1000Msun/yr star forming events in submm-bright high z QSOs. Stars are sufficient for producing their rest frame FIR emission. The typical z~2.5 luminous QSOs has less intense star formation, and a lower ratio of star formation to AGN luminosity.