vandana desai spitzer science center with lee armus, colin borys, mark brodwin, michael brown, shane...
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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. 2009 after Sanders et al. 1988
9 deg9 deg22
Bw, R, I, K ~ 27.1, 26.1, 25.4, 19.0 mag (Vega)Bw, R, I, K ~ 27.1, 26.1, 25.4, 19.0 mag (Vega)MIPS-24 ~0.3 mJyMIPS-24 ~0.3 mJy
PIs: A. Dey & B. Jannuzi
NOAO Deep Wide-Field SurveyGround-based Data for Bootes Field
Dust-Obscured Galaxies (DOGs)
€
R −[24] ≥14
fν (24)
fν (R)≥1000
νfν (24)
νfν (R)≥ 27
Most extreme 10%
R-[24] (Vega mag)
Frac
tion
Redshift
R-[2
4] (V
ega
mag
)DOG Selection
Warning: Need better data on UV emission from local ULIRGs.
Dey+08
Dey +08
DO
G F
racti
on
...where we find the peak of the 24m counts!
increasingly significant numbers at fainter fluxes... Papovich et al. 2004
24 micron flux (mJy)
24 micron flux (mJy)
Papovich +04
24 micron flux (mJy)Eucl
id N
orm
# C
ount
s
The DOG criterion selects for z = 2
Dey+08
LIR = ULIRGs (large error)
Space density = (2.82+-0.05)x10-5h70
Mpc-3
(like 4L* galaxies)
Log(IRLD) = 8.23+0.18
-0.30 Lsun Mpc-3
•60% of all z=2 ULIRGs•25% of IRLD at z = 2
Spectroscopy of Power-Law DOGsHouck+05, also Weedman+06, Yan+06IRS NIRSPEC Brand+07
•7/10 are broad-line AGN•Extinction to narrow and broad-lines high – host obscured?
•AGN-like: •silicate absorption•Weak PAHs
NIR spectra of bump DOGs
No NIR spectra of bump sources due to inconvenient redshift.
70 micron selection? Casey+09, Farrah+09Desai+09
Morphology - HST
• Extended emission dominates
• Few on-going mergers
2” Morphologies of power-law DOGs
rest-UV rest-UV rest-opticalrest-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. 2009
Fainter (bump/SF) DOGs are more diffuse than bright (PL/AGN) DOGs.
Clustering
Strong clustering
Comparable to SMGs & QSOs
Large uncertaintiesF(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 DOGs5/12 detected at 350m with CSO
0/2 of these detected at 1.3mm with CARMA
Preferred SED:Mrk231
Tdust > 45 K (Warmer than SMGs)
Mdust ~ 3x108 Msun
Bussmann et al. 2009b
FIR SEDs of bump DOGs
Pope+08, see also Lonsdale+09,Fiolet09
PACS 110 mSCUBA-2 450 m
70 faint DOGs in GOODs-N
Stack 70, 160, 850, 1.2mm
TBDOG ~ TSMG
Need some extra hot dust (10% of LIR) compared to SMGs
SFR = 200 Msun/yr
Stacked X-rays consistent with SF, but see Fiore+08
Herschel GTO observations of Bootes5- instrumentaltotal sensitivity (mJy)
110 mPACS
160 mPACS
250 mSPIRE
350 mSPIRE
500 mSPIRE
Level 5 2 deg2 20.4 29.331 1426 19.328 16.326
Level 6 8 deg2 38.2 54.856 26.234 36.141 30.436Herschel 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 mSCUBA-2 450 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. 2009 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!