Spitzer 70 Micron Source Counts in GOODS-North

We present ultradeep Spitzer 70 μm observations of GOODS-North (Great Observatories Origins Deep Survey). For the first time, the turnover in the 70 μm Euclidean-normalized differential source counts is observed. We derive source counts down to a flux density of 1.2 mJy. From the measured source counts and fluctuation analysis, we estimate a power-law approximation of the faint 70 μm source counts of dN/dS ∝ S-1.6, consistent with that observed for the faint 24 μm sources. An extrapolation of the 70 μm source counts to zero flux density implies a total extragalactic background light (EBL) of 7.4 ± 1.9 nW m-2 sr-1. The source counts above 1.2 mJy account for about 60% of the estimated EBL. From fluctuation analysis, we derive a photometric confusion level of σc = 0.30 ± 0.15 mJy (q = 5) for the Spitzer 70 μm band.

[1]  M. Im,et al.  The Spitzer Space Telescope Extragalactic First Look Survey: 24 μm Data Reduction, Catalog, and Source Identification , 2006, astro-ph/0603488.

[2]  G. Rieke,et al.  The Cosmic Infrared Background Resolved by Spitzer. Contributions of Mid-Infrared Galaxies to the Far-Infrared Background. , 2006, astro-ph/0603208.

[3]  Ssc,et al.  Spitzer Observations of Massive, Red Galaxies at High Redshift , 2005, astro-ph/0511289.

[4]  J. Dunlop,et al.  Linking Stellar Mass and Star Formation in Spitzer MIPS 24 μm Galaxies , 2005, astro-ph/0510070.

[5]  D. Padgett,et al.  Spitzer 70 and 160 μm Observations of the Extragalactic First Look Survey , 2005, astro-ph/0509649.

[6]  M. Giavalisco,et al.  The Population of BzK-selected ULIRGs at z ~ 2 , 2005, astro-ph/0507504.

[7]  Tucson,et al.  Infrared Luminosity Functions from the Chandra Deep Field-South: The Spitzer View on the History of Dusty Star Formation at 0 ≲ z ≲ 1* , 2005, astro-ph/0506462.

[8]  Christopher D. Martin,et al.  Spitzer View on the Evolution of Star-forming Galaxies from z = 0 to z ~ 3 , 2005, astro-ph/0505101.

[9]  Soojong Pak,et al.  Far-infrared detection limits¿ I. Sky confusion due to Galactic cirrus , 2005 .

[10]  W. Brandt,et al.  The unresolved hard X-ray background: the missing source population implied by the Chandra and XMM-Newton deep fields , 2004, astro-ph/0412266.

[11]  Marcia J. Rieke,et al.  Confusion of Extragalactic Sources in the Mid- and Far-Infrared: Spitzer and Beyond , 2004 .

[12]  Paul S. Smith,et al.  The Multiband Imaging Photometer for Spitzer (MIPS) , 2004 .

[13]  P. R. M. Eisenhardt,et al.  The Nature of Faint 24 Micron Sources Seen in Spitzer Space Telescope Observations of ELAIS-N1 , 2004 .

[14]  G. Rieke,et al.  Polycyclic Aromatic Hydrocarbon Contribution to the Infrared Output Energy of the Universe at z ≃ 2 , 2004, astro-ph/0406016.

[15]  O. Krause,et al.  Far-infrared Source Counts at 70 and 160 Microns in Spitzer Deep Surveys , 2004, astro-ph/0406021.

[16]  F. Masci,et al.  Characterization of Extragalactic 24 Micron Sources in the Spitzer First Look Survey , 2004, astro-ph/0405637.

[17]  E. Wright.  COBE observations of the cosmic infrared background , 2003, astro-ph/0306058.

[18]  G. Lagache,et al.  Predictions for Cosmological Infrared Surveys from Space with the Multiband Imaging Photometer for SIRTF , 2002, astro-ph/0211312.

[19]  G. Lagache,et al.  Power spectrum of the cosmic infrared background at 60 and 100 μm with IRAS , 2002, astro-ph/0207312.

[20]  David Elbaz,et al.  The Bulk of the Cosmic Infrared Background Resolved by ISOCAM , 2002, astro-ph/0201328.