Ultra-Luminous Infrared Galaxies at high redshift - The Spitzer perspective E. Le Floc’h (Steward Observatory, University of Arizona) * Spitzer-NDWFS : A.Dey, K.Brand, B.Jannuzi (NOAO), V.Desai, T.Soifer, L.Armus, C.Borys (Caltech), S.Higdon, J.Higdon, D.Weedman (Cornell), K.Tyler (Arizona) * MIPS team : C.Papovich, G.Rieke (Arizona), H.Dole (IAS-Orsay) Galaxies and Structures through Cosmic Times, March 29 th, 2006 * DEEP : C.Willmer, K.Noeske, D.Koo, E.Laird, P.Nandra, N.Konidaris, J.Lotz, A.Coil, C.Conselice, P.Barmby, M.Ashby, R.Ivison, … + R.Gilli, R.Maiolino, E.Bell, V.Charmandaris, D.Elbaz, ….

IRAS and the ULIRGs at low redshift ( Mirabel et al. 1991) Infrared UV (visible). (Sanders & Mirabel 1996) (Adapt. Devriendt et al. 1999) ULIRGs: - L(  m) > L  - only a few % of the IR energy density in the local Universe Galaxies and Structures through Cosmic Times, March 29 th, 2006 ULIRGs Spirals

Infrared luminosity functions Local IRAS LF Galaxies and Structures through Cosmic Times, March 29 th, 2006 Faint-end slope constrained from the deep source counts in GOODS-N as well as stacking analysis with COMBO-17 (Zheng et al. 2005) 1000x ! < 10 LF05

ULIRG evolution with redshift 1<z<3  Galaxies and Structures through Cosmic Times, March 29 th, 2006 LF05 ? ( © Hughes et al.) SCUBA

Spitzer ULIRGs at z>1 - «template» selection : e.g., Le Floc’h et al. 04, Lonsdale et al. 04, Rowan-Robinson et al LBGs : e.g., Huang et al DRGs : e.g., Papovich et al BzKs : e.g., Daddi et al. 05 (also X.Kong’s talk) ULIRGs … no single approach with a uniform selection. Which connection between these populations ? (Papovich et al. 2006) Galaxies and Structures through Cosmic Times, March 29 th, 2006 DRGs

Galaxies and Structures through Cosmic Times, March 29 th, 2006 R-24 selection of z>2 ULIRGs Bootes CDFS > 0.3 mJy > 0.08 mJy - F 24  m > ~1mJy - R > ~24-25 mag (extreme IR/opt ratios) IRS spectra : 2<z<3  coeval to the SCUBA sources  but 5-10x brighter in the mid-IR (Houck et al. 2005, Yan et al. 2005, Weedman et al. 2006) (deep) (shallow) R - 24  m > 15 

Galaxies and Structures through Cosmic Times, March 29 th, 2006 AGNs or starbursts ? Starburst also lots of feature-less power-laws (no redshift) - in most cases : features from Si - rarer but still detected : PAHs Bias toward AGNs / warm sources (Brand et al. 2006) Starbursts * AGNs * X-ray sources * > 1mJy pop. Wavelength (micron) AGN

Galaxies and Structures through Cosmic Times, March 29 th, 2006 AGNs or starbursts ?  Cold Warm (Chapman et al. 2005) MIPS SCUBA (2004)

Galaxies and Structures through Cosmic Times, March 29 th, 2006 Far-IR properties of z>2 ULIRGs - 70  m and 160  m stacking at the positions of the 24  m-selected ULIRGs (K.Tyler et al.) - Spitzer GO2 : deep imaging at 70  m and 160  m 70  m 24  m 160  m Z=2.46 (Borys et al. 06, Desai et al. 06) Starburst-dominated HyLIRG Z=1.3

CXO-J , L X ~ 2x10 44 erg/s - N H ~ cm  m z = 1.15 Galaxies and Structures through Cosmic Times, March 29 th, mid-IR spectrum : no Si absorption, very weak PAHs, …

(Page et al. 01, Alexander et al. 05…) Coeval growth buldge / SM-BH Galaxies and Structures through Cosmic Times, March 29 th, L bol ~ 9x10 12 L  - 50% cold, 50% warm, … - 20% emitted below 8  m  E sbt ~ E AGN CXO-J  H  He ~ 0.7%  Acc. ~ 10% - -  E sbt ~ 5 x E AGN to satisfy the Magorrian relation *if* T sbt = T AGN

Galaxies and Structures through Cosmic Times, March 29 th, 2006 Summary * ULIRGs at 0<z<1 : increasing contribution to the IR energy density, reaching ~10% at z~1 * ULIRGs at z>1 : not a uniform selection yet * Connection between SCUBA- and optical/near-IR selections still to be addressed * A « new » population selected with extreme IR/opt. ratios and located at 2<z<3 - AGN-dominated in the mid-IR, but evidence for starburst emission in the FIR - Might witness the coeval growth of stellar buldges and SM black holes, but with different time scales