Vandana Desai Spitzer Science Center with Lee Armus, Colin Borys, Mark Brodwin, Michael Brown, Shane Bussmann, Arjun Dey, Buell Jannuzzi, Emeric Le Floc’h, Jason Melbourne, Alexandra Pope, Tom Soifer Dust-Obscured Galaxies (DOGs)

The role of high-z ULIRGs Merger Starburst AGN “on” Quasar Massive Galaxy and their relation to mergers, star formation, AGN, and the formation of massive galaxies Dey et al after Sanders et al. 1988

The z=2 ULIRG zoo Caitlin’s MIPS-70 ULIRGs Alejo’s Host-obscured Quasars SMGs

9 deg 2 Bw, R, I, K ~ 27.1, 26.1, 25.4, 19.0 mag (Vega) MIPS-24 ~0.3 mJy PIs: A. Dey & B. Jannuzi NOAO Deep Wide-Field Survey Ground-based Data for Bootes Field

Dust-Obscured Galaxies (DOGs) Most extreme 10% R-[24] (Vega mag) Fraction

Redshift R-[24] (Vega mag) DOG Selection Warning: Need better data on UV emission from local ULIRGs. Dey+08

DOG Fraction...where we find the peak of the 24  m counts! increasingly significant numbers at fainter fluxes... Papovich et al micron flux (mJy) Papovich micron flux (mJy) Euclid Norm # Counts

The DOG criterion selects for z = 2 Dey+08 LIR = ULIRGs (large error) Space density = ( )x10 -5 h 70 Mpc -3 (like 4L* galaxies) Log(IRLD) = L sun Mpc -3 60% of all z=2 ULIRGs 25% of IRLD at z = 2

Power Laws and Bumps Bright Power-Law AGN Faint “Bump” starforming

Spectroscopy of Power-Law DOGs Houck+05, also Weedman+06, Yan+06 IRS NIRSPEC Brand+07 7/10 are broad-line AGN Extinction to narrow and broad- lines high – host obscured? AGN-like: silicate absorption Weak PAHs

Desai+09, Huang+09, Farrah08 Spitzer/IRS spectra of bump DOGs

NIR spectra of bump DOGs No NIR spectra of bump sources due to inconvenient redshift. 70 micron selection? Casey+09, Farrah+09 Desai+09

Morphology - HST Extended emission dominates Few on-going mergers 2” Morphologies of power-law DOGs rest-UV rest-optical Bussmann et al. 2009a; See also Dasyra et al. 2009

Morphology - HST On-going interactions more common More similar to SMGs (Borys et al., in prep) 2” Morphologies of bump DOGs rest-optical Bussmann et al. 2010, in prep.

Morphology – Keck AO Melbourne et al Fainter (bump/SF) DOGs are more diffuse than bright (PL/AGN) DOGs.

Clustering Strong clustering Comparable to SMGs & QSOs Large uncertainties F (24) [mJy] Brodwin et al. 2008, Magliocchetti+08, Farrah+06 2<z<2.5 QSOs (Shen et al. 2008) 1.4<z<2 QSOs (Shen et al. 2008) 2<z<2.5 QSOs (Shen et al. 2008) R 0 (h -1 Mpc)

FIR SEDs of PL DOGs 5/12 detected at 350  m with CSO 0/2 of these detected at 1.3mm with CARMA Preferred SED:Mrk231 T dust > 45 K (Warmer than SMGs) M dust ~ 3x10 8 M sun Bussmann et al. 2009b

FIR SEDs of bump DOGs Pope+08, see also Lonsdale+09,Fiolet09 PACS 110  m SCUBA  m 70 faint DOGs in GOODs-N Stack 70, 160, 850, 1.2mm T BDOG ~ T SMG Need some extra hot dust (10% of LIR) compared to SMGs SFR = 200 M sun /yr Stacked X-rays consistent with SF, but see Fiore+08

Herschel GTO observations of Bootes 5-  instrumental  total sensitivity (mJy) 110  m PACS 160  m PACS 250  m SPIRE 350  m SPIRE 500  m SPIRE Level 52 deg  3114    26 Level 68 deg     36 Herschel probes peak of DOG SED! Bright, rare Bootes DOGs likely detected in L5 250  m data depending on: confusion the power of priors FIR SEDs Bulk properties attainable through stacking

Herschel Key Program in GOODS PACS 110  m SCUBA  m PACS and SCUBA-2 will detect most (fainter) DOGs in GOODs. Pope et al. 2008

The role of high-z ULIRGs Merger SMG – bump DOG PL DOG Quasar Massive Galaxy and their relation to mergers, star formation, AGN, and the formation of massive galaxies Dey et al after Sanders et al. 1988

Summary ~Half of z = 2 ULIRGs are DOGs Contribute a ~quarter of the total IR luminosity density at z~2 Space density + clustering => ~ 3-4L* elliptical at z=0 Bright DOGs ~ Power-Law ~ compact ~ (obscured) AGN Faint DOGs ~ Bump ~ diffuse, interacting ~ SF Herschel will help pin down FIR SED, which is a major existing uncertainty. Need FIR SEDs to reassess!

What is a DOG? A ULIRG at z = 2, selected at 24 micron