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Cambridge, September 9th 2004
Spitzer discovery of luminous infrared galaxies at 1<z<2.5
Emeric Le Floc’hUniversity of Arizona
“A starry sunset seen by MIPS”
… and
* Casey Papovich* Pablo Pérez-González* Eiichi Egami* Hervé Dole* Almudena Alonso-Herrero* George & Marcia Rieke
+ the MIPS instrum. team
see also Casey’s talk tomorrow !
Cambridge, September 9th 2004
Spitzer discovery of luminous infrared galaxies at 1<z<2.5
Emeric Le Floc’hUniversity of Arizona
“A starry sunset seen by MIPS”
I) MIPS capability for deep surveys
2) What we learnt from the counts
3) A possible new model ?
4) IR luminosity functions
5) IR luminous sources in the redshift desert
“A starry sunset seen by MIPS”
Cambridge, September 9th 2004
MIPS GTO cosmological surveys
Cambridge, September 9th 2004
MIPS GTO cosmological surveys
N
E
Bootes field - 24 μm
© Houck/Rieke/Soifer/ Weedman
MIPS : - 24, 70 and 160 μm - large area coverage - unprecedented sensitivity in the IR
* Shallow survey (~90s) :(IRS team/M.Rieke)
- 9 deg, ~32000 sources- Comp. 80% : 0.3 mJy @ 24 μm
2
3.2 deg
Cambridge, September 9th 2004
MIPS GTO cosmological surveys
MIPS : - 24, 70 and 160 μm - large area coverage - unprecedented sensitivity in the IR
* Shallow survey (~90s) :(IRS team/M.Rieke)
- 9 deg, ~32000 sources- Comp. 80% : 0.3 mJy @ 24 μm
2
* Deep surveys (~1400s) :
- CDFS, HDF-N, Lockman Groth Strip ..... (~0.6 deg )- Comp. 80% : 80 μJy @ 24 μm
2
Bootes
CDFS
N
E
Bootes field - 24 μm
© Houck/Rieke/Soifer/ Weedman
2’
Cambridge, September 9th 2004
The MIPS number counts
The strong evolution revealedby ISO and SCUBA is clearlyobserved by MIPS at 24, 70and 160 m.
24 m(Dole et al. 2004)
(Papovich et al. 2004)
no evolution
no evolution
but the turn-over in the 24 m different. counts is at lower flux than expected based on pre-launch models !
Cambridge, September 9th 2004
Phenomenological model
* 2 populations of sources : starburst and cold galaxies
Lagache et al. 2004 (an update of Lagache et al. 2003) :
* Library of IR templates
* A z=0 IR luminosity function
based on the IRAS data
Find the evolution to fit the ISO/Spitzer/SCUBA number counts
(Lagache et al. 2004)
(Lagache et al. 2004)
new templates
old templates
new evolution of the IR luminosity
old evolution
(Lagache et al. 2004)
24 m
0<z<0.3
0<z<0.8
0<z<1
0<z<1.3
0<z<2
0<z<
Cambridge, September 9th 2004
old templates
Results and Predictions
Lagache et al. 2004
Lagache et al. 2003
* 30% of sources at z>2 for 24m fluxes~0.2mJy
(3x more sources at z>1.5 than predicted before)
* The peak of the contribution of sources at 0<z<z_lim is shifting to lower fluxes when z_lim increases
(Papovich et al. 2004)
LIRGs/ULIRGs in the
redshift desert
(for fluxes > 80 μJy at 24 μm)
Cambridge, September 9th 2004
old templates
MIPS observations of the CDFS
Lagache et al. 2003
24217 sources from COMBO-17 (x1/5)
MIPS 24 m sources
(MIPS sources with spec. z)
* Spectr. z : VVDS, GOODS, Chandra follow-up* Photometric z : COMBO-17
775 arcmin^2, 5240 MIPS sources, 442 with spec.z (8%), 2678 with phot.z : total=3120 sources
MIPS
COMBO-17VVDS
30’
N
E
(Le Fèvre et al., Vanzella et al., Szokoly et al., Wolf et al.)
Cambridge, September 9th 2004
MIPS sources at 0<z<1
Flux 24 μm (mJy)0.1 1
dN
/dS
x S
^2.
5 (a
rbit
rary
un
it)
Papovich et al. 2004
Total “MIPS/COMBO” area
0<z<0.3
0<z<0.8
0<z<1
0<z<1.3
?
Cambridge, September 9th 2004
MIPS sources at 0<z<1
Flux 24 μm (mJy)0.1 1
dN
/dS
x S
^2.
5 (a
rbit
rary
un
it)
Papovich et al. 2004
Total “MIPS/COMBO” area
* Contribution of z<1 sources could be under- estimated
* Need better statistics (i.e., add other fields)
* Peaking at constant flux
How to refine the model ?
* LF evolution ?* PAH templates ?
Cambridge, September 9th 2004
24 μm IR luminosity ?
Redshift
Ob
serv
ed 2
4 μ
m f
lux
(mJy
)
80 μJy
10 , 10 , 10 , 10 , 10 L9 10 11 12 13
* A tight mid-IR / far-IR / total IR in the local Universe (e.g., Chary & Elbaz 2001)* Seems to be still OK at high z (P. Appleton ‘s talk)* SEDs consistent with PAHs at z~0.8 (D.Elbaz ‘s talk)
- If using local templates, L_IR should be accurate within a factor of 2, depending on the library- Possible caveats : evolution with metallicity ?
(Dale et al. 2001, Lagache et al. 2003/4, Chary & Elbaz 2001, Chanial 2003)
Z>1.5
(24 μm + 70 μm ?? see Casey’s talk )
Cambridge, September 9th 2004
IR luminosities in the CDFS
Redshift10.10.01
L_I
R (
L ) LIRGs (~15<SFR<150 M /yr)
ULIRGs
HyLIRGs
(COMBO-17)
Cambridge, September 9th 2004
IR luminosity functions in the CDFS
* Faint-end slope steeper than predicted by Lagache et al.
but no steepening of the local LF
* Strong evolut. in luminosity :
(1+z) 3-4
* Modest evolut. in density (exclude a pure density evol.)
L_IR (L ) L_IR (L )
L_IR (L )L_IR (L )
LF
(/M
pc
^3
/ma
g)
LF
(/M
pc
^3
/ma
g)
LF
(/M
pc
^3
/ma
g)
LF
(/M
pc
^3
/ma
g)
0.85<z<10.7<z<0.85
0.6<z<0.70.5<z<0.6
Lagache et al. 2004
(local LF)
Cambridge, September 9th 2004
old templates
MIPS in the redshift desert
* Use of “IRAC” photo-z : (probing the **hump** of the old stellar population continuum)
* Spectroscopy with medium resolution, catching absorption lines (data from DEEP)
(Le Floc’h et al. 2004)
Cambridge, September 9th 2004
old templates
Multi- propert. of z>1 MIPS sources
Lagache et al. 2003
IRAC 8μm MIPS 24μm R band
VLA/SCUBA IRAC 3.6μm IRAC 4.5μm
(Alonso-Herrero et al. 2004)(Egami et al. 2004, Ivison et al. 2004)
* Detection of VLA/SCUBA/MAMBO sources with MIPS :
* Detection of X-ray sources at 24 μm :
submm wavelengths ( efficient way to catch Infrared luminous galaxies at z>1 )
(e.g. Egami et al. 2004)
pre-selection at radio/
up to z~1.6 with IRAC photo-z’s so far (Alonso-Herrero et al. 2004)
Cambridge, September 9th 2004
Perspectives...
* Source density, luminosity functions at z>1 ???
- Cosmic variance ? same work must be done in other fields- MIPS sources without z, which consequence for LF at z<1 ?- AGN contamination ?- SED templates, PAHs ??- How does the LF depend on SEDs ?
* Issues
STILL A LOT OF WORK !!
too early !…. (need good photo-zs)
Cambridge, September 9th 2004
Cosmic variance in the CDFS
Courtesy Eric Bell
Redshift
Redshift
B-b
an
d l
um
in.
de
ns
ity
To
tal/
CD
FS
CDFS
Total COMBO-17 (3 fields 30’x30’)
Cambridge, September 9th 2004
60 μm lumin. Functions in the CDFS
L_IR (L )
LF
(/M
pc^
3/m
ag)
0.85<z<10.7<z<0.85
0.6<z<0.70.5<z<0.6
(local LF)
L_IR (L )L
F (
/Mp
c^3/
mag
)
L_IR (L )
LF
(/M
pc^
3/m
ag)
L_IR (L )
LF
(/M
pc^
3/m
ag)
L_IR (L )
LF
(/M
pc^
3/m
ag)
L_IR (L )
LF
(/M
pc^
3/m
ag)
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