Are quiescent galaxies truly devoid of star formation?

26 Pages·2015·4.6 MB·English

Are quiescent galaxies truly
devoid of star formation?
A mid-, far-infrared & radio stacking analysis
Allison Man
ESO Garching
with Thomas Greve, SuneToft, Benjamin Magnelli, Alexander Karim,
Olivier Ilbert, Mara Salvato, Emeric Le Floc’h, Frank Bertoldi, Caitlin Casey,
Nicholas Lee, Yanxia Li, Felipe Navarrete, Kartik Sheth, Vernesa Smolcic,
David Sanders, Eva Schinnerer, and Andrew Zirm
ApJ under review, arXiv: 1411.2870
S
SED Workshop, Cambridge, 17th September 2015
Quiescent galaxies
“Red Sequence”
- Low SFR
SED
- Dominate at
high stellar mass
- Mostly spheroids
Wuyts+11
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Quiescent galaxies
Hopkins et al 2006, Wuytset al 2010, Toftet al 2014
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Quiescent galaxies
Hopkins et al 2006, Wuytset al 2010, Toftet al 2014
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Selecting quiescent galaxies
S Red galaxies can be…
S Old (evolved stellar populations), or
S Heavily dust attenuated
S Candidates selected by colour cuts from
photometry
S (e.g. NUV-r & r-K, U-V & V-J)
Bergstrom & Wiklind 2004
- - - 100 Myr starburst, E(B-V)=2
1Gyr elliptical
For a galaxy at z=2
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UV-to-NIR spectra
for quiescent galaxies at z>1
S No strong emission lines
S Absorption line studies indicate
evolved stellar population
S Age ~ 1-2Gyr at z~2
S inferred z at z~3-4
form
van de Sande+13, also Kriek+09; van de Sande+11; 6 Allison Man, ESO, arXiv: 1411.2870
Toft+12, +14, Belli+14ab,+15, Onodera+10,+12,+14
Consistency for different
SFR indicators?
SFR indicator True quiescence? Caveats
Rest-frame UV slope ✔ (photometry) - Need to correct for dust
Nebular emission line ✔ - Need to correct for dust
(No strong emission lines) - Spectroscopy time-costly
Mid-infrared continuum ✔ AGN vs SF
(Fumagalli+14, Utomo+14)
Far-infrared continuum ✗ (Viero+13) Large beam à Source blending
Radio continuum ? AGN vs SF
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True quiescence or
dusty starbursts?
S FIR stacking à Dusty starbursts (Viero+2013)
S Average stacking with deblending on Herschel data
S Found that z>2 quiescent galaxies are (U)LIRGs on average
S MIR stacking à True quiescence (Fumagalli+2014 & Utomo+2014)
S Median stacking on 24μm data
S Found that quiescent galaxies do not host strong dust-obscured SF
8 Allison Man, ESO, arXiv: 1411.2870
True quiescence or
dusty starbursts?
S FIR stacking à Dusty starbursts (Viero+2013)
S Average stacking with deblending on Herschel data
S Found that z>2 quiescent galaxies are (U)LIRGs on average
S MIR stacking à True quiescence (Fumagalli+2014 & Utomo+2014)
S Median stacking on 24μm data
S Found that quiescent galaxies do not host strong dust-obscured SF
9 Allison Man, ESO, arXiv: 1411.2870
Sample & Data
S 14,200 Quiescent galaxy candidates from
COSMOS/UltraVISTA
S Selected by rest-frame NUV-r and r-J colors
(Ilbert+13)
S log(M /M ) ~ 10, 10.4, 10.8, 11.2
* ¤
S z ~ 0.4, 0.8, 1.2, 1.7, 2.2, 2.6
S Ancillary infrared & radio data
S Spitzer 24μm
S Hershel PACS + SPIRE: 100, 160, 250, 350 & 500μm
S VLA 1.4GHz (20cm)
10 Allison Man, ESO, arXiv: 1411.2870