véronique buat & sebastien heinis with the contribution of laure ciesla
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Far-infrared properties of UV selected galaxies from z=4 to z=1.5: unveiling obscured star formation. Véronique Buat & Sebastien Heinis With the contribution of Laure Ciesla Based on HerMES /SPIRE data in the COSMOS field Heinis , Buat et al. 2013. - PowerPoint PPT PresentationTRANSCRIPT
Far-infrared properties of UV selected galaxies from z=4 to z=1.5: unveiling obscured star
formationVéronique Buat & Sebastien Heinis
With the contribution of Laure Ciesla
Based on HerMES/SPIRE data in the COSMOS fieldHeinis, Buat et al. 2013
From Exoplanets to Distant Galaxies: SPICA’s New Window on the Cool Universe18-21 june 2013-University of Tokyo, Japan
Elbaz’s lectures (david.elbaz3.free.fr/coursJ1.html), adapted from Devriendt+99
Visible
Infrared mm
UV
wavelength
inte
nsit
y
dust
Both UV and IR are related to recent star formationThey are anti-correlated because of dust attenuation
IR selected objects are usually obscured with a low residual emission in UV
Conversely: we expect a UV selection to be dominated by IR faint sources
Only few words about the physical link between UV and IR emissions
We perform a UV rest-frame selection in the COSMOS field @ z=1.5, 3 & 4
Based on photometric redshifts (Ilbert+13)Down to u, r, i ≈ 26 ABmag
What do we find within HerMES/ SPIRE images?
Almost nothing…….
Z = 1.5
Stacking per bin of LFUV
LIR measured by fitting Dale & Helou (2002) templates on SPIRE data
AFUV = f(LIR/LFUV) (Buat+05) LIRGs and sub-LIRGs
Stacking per bin of M*(again on the UV selection)
Z=1.5Z=3Z=4
Stacking per bin of (LFUV,M*)
Dust attenuation increases with M* for a given LFUV
Dust attenuation decreases with LFUV for a given M*
The dispersion in dust attenuation decreases with LFUV
See also Burgarella+06, Buat+09,12
A recipe to derive LIR/LFUV=IRXHeinis+13, very close to be submitted
IRX=log(LIR/LFUV)=IRX0(LFUV)+0.72*log(M*/1010.35)@z=1.5 & 3
SFR versus M* : a well defined ‘Main Sequence’
for star-forming galaxies
SFR= SFR0 M*0.7
slope< 1
see also Noeske+07, Oliver+10, Whitaker+12
slope~1 found by Elbaz+07, Daddi+07, Wuyts+11
(from Kennicutt, 98)
Z=1.5Z=3Z=4
Specific SFR (sSFR=SFR/M*) : very active galaxies at z =3 & 4, a challenge for the models
sSFR(z,M*) high redshift galaxies (z~2.5-4) stay only around 1 Gyr on the Main Sequence, this time increasing with decreasing redshift
What can we do with SPICA?• Herschel was unable to detect individual
galaxies selected in UV at z >= 1.5 (less than 1% of the galaxies directly detected)
Studies based on a stacking technics: average trends only, no or little dispersion measured
• We must increase the number of individual detections if we want to discuss the variety of physical properties of individual galaxies
Individual detections with SPICA?
Dale & Helou 02 templates
α=2
α=1.5
Assuming 50 µJy @ 70 µm
How many galaxies in the COSMOS field?•z=1.5 9419 galaxies/deg2
•z=3 3162 galaxies/deg2
Assuming a Dale & Helou template with α = 2
As a function of LFUV
How many galaxies could be detected in the COSMOS field?•z=1.5 9731 galaxies/deg2
•z=3 3493 galaxies/deg2
•z=4 952 galaxies/deg2
As a function of M*
Which template to measure LIR? What do we learn from
Herschel? Z=0Z=1.5
Ciesla+13, in prep.
The determination of LIR with a single monochromatic measurement might lead to large uncertainties
Several bands might be very useful to constrain the SED
Still some work to be made to refine SEDs……
Ciesla+13, in preparation
Conclusions• To measure the dust emission of UV bright high
redshift galaxies is challenging• HERSCHEL was not able to detect them
individually at z ≥1.5• Deep photometric observations with SPICA @
λ≈70 μm will allow direct detections of several thousands of galaxies per deg2 also observed in optical (UV rest-frame)
• Coordinated deep surveys with SPICA instruments (SAFARI-MCS-FPF) would provide full SEDs of these galaxies, allowing physical analyses.
Stacking per bin of M*(again on the UV selection)
Stacking per bin of LFUV
LIR measured by fitting Dale & Helou (2002) templates on SPIRE data
AFUV = f(LIR/LFUV) (Buat+05) LIRGs and sub-LIRGs