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Star Formation in the Cosmic Web

Hervé Aussel, AIMDave Sanders, Mara Salvato,

Olivier Ilbert, David Frayer, Jason Surace, Nick Scoville, and the S-

Cosmos team

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The Cosmic Infrared Background

Dole et al. (2006)

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The Cosmic Infrared Background

• COB:– 23nW/m2/sr

• CIB:– 24 nW/m2/sr

• COB/CIB~1• Locally:

– O/I = 0.3

Dole et al. (2006)

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The Resolution of the CIB• COB/CIB ~1 indicates that

– There is a strong evolution of the infrared emission of galaxies

– Directly probed by SCUBA (850 µm)– Indirectly probed by

• ISOCAM (15 µm)• MIPS (24 µm)

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ISOCAM surveys• Resolved the CIB at 15

µm • Resolved 70% of the

CIB at 140µm– LIRGs ~60 %– ULIRG ~ 25 %

• Massive disks galaxies between z=0.5 and z=1.2

• Liittle AGN contribution (< 20%)

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MIPS 24 µm Surveys• Strong Evolution also

observed at 24µm• Strong evolution of

LIRGs and ULIRGs• Massive galaxies

– 40 % of the M > 2x1010Msol are undergoing a starburst at z~0.7 (Bell et al, 2005)

• Little AGN contribution

Papovich et al. (2004)

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MIPS 24 µm surveys

Le Floc’h et al (2005)

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Open Questions:

• What drives the SB?• Most of the galaxies

responsible for the evolution belong to “Structures”– Elbaz & Cesarsky (2003)

• Bias: is mass a main parameter or are we biased by environment?

• Major Merger?– Hammer et al. (2005)

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Open Questions• What about dense environments ?

– Infrared MDR in some clusters:• A1689: 30 galaxies detected at 15µm (Duc et

al., 2002)• Verified in some clusters, not in others • Age of the structure might be a key parameter

(Coia et al., 2005)

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S-Cosmos• Map the 2 sq degree of the Cosmos

field with IRAC and MIPS.• MIPS:

– goal is to reach 67 µJy (5 ) at 24µm– 36 hrs

• Full area at 420 µJy (5 ) • Test field at 67 µJy (5 )

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COSMOS Field• Low Extinction• Low Background

– IRAS 100 m:• COSMOS: 0.9 MJy/sr• Lockman: 0,5 MJy/sr• XMM-LSS: 1.3 Mjy/sr:

• No bright radio/X-ray source

• 10:00:28.6+02:12:21

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COSMOS Field• Low Extinction• Low Background

– IRAC 8 m:• COSMOS: 6.9 MJy/sr• Lockman: 5.0 MJy/sr• XMM-LSS: 7.1 Mjy/sr:

• No bright radio/X-ray source

• 10:00:28.6+02:12:21

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COSMOS Field• Low Extinction• Low Background

– MIPS 24 m:• COSMOS: 32.3 MJy/sr• Lockman: 18.4 MJy/sr• XMM-LSS: 31.1 MJy/sr

– At most a loss of 20% in sensitivity w/r to non equatorial fields

• No bright radio/X-ray source

• 10:00:28.6+02:12:21

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Zodiacal Background

Reach, private communication

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Asteroids in the Cosmos Field

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2sq degrees• No cirrus emission• Detection limit to

420µJy (5)

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Main and Deep Area

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Deep area

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MIPS, IRAC and Galex

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Submm sources

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Conclusions• S-Cosmos MIPS pilot project has

demonstrated the • Need to probe below 100 µJy

– to resolve a significant fraction of the CIB– To probe the LIRG regime out to z~2

Z 0.5 1 1.5 2

67 µJy 10.5 11.0 11.7 12.0

420 µJy 11.2 11.8 12.5 12.8