Cambridge, September 9th 2004 Spitzer discovery of luminous infrared galaxies at 1

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 !


Spitzer discovery of luminous infrared galaxies at 1<z<2.5

Emeric Le Floc’hUniversity of Arizona


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



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



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’


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 !


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)


new templates

old templates

new evolution of the IR luminosity

old evolution


24 m

0<z<0.3

0<z<0.8

0<z<1

0<z<1.3

0<z<2

0<z<


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)


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.)


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

?


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 ?


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 )


IR luminosities in the CDFS

Redshift10.10.01

L_I

R (

L ) LIRGs (~15<SFR<150 M /yr)

ULIRGs

HyLIRGs

(COMBO-17)


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)


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)


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)


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)


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’)


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)

Cambridge, September 9th 2004 Spitzer discovery of luminous infrared galaxies at 1

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