Spitzer Deep and Wide Legacy Mid- and Far-Infrared Number Counts and Lower Limits of Cosmic Infrared Background

Béthermin, M., Dole, H., Beelen, A., Aussel, H., submitted to AandA, 2009

Aims: We want to place stronger lower limits on the Cosmic Infrared Background (CIB) brightness at 24, 70 and 160 um and measure the extragalactic number counts at these wavelengths in an homogeneous way from various surveys.

Methods: Using Spitzer legacy data over 53.6 deg^2 of various depths, we build catalogs with the same extraction method at each wavelength. Completeness and photometric accuracy are estimated with Monte-Carlo simulations. Number count uncertainties are estimated with a counts-in-cells moment method, in order to take into account galaxy clustering. Furthermore, we use a stacking analysis to estimate number counts of sources not detected at 70 and 160 um. This method is validated by simulations. The integration of the number counts gives new CIB lower limits.

Results: Number counts reach 35 muJy (resp. 3.5 mJy and 40 mJy) at 24 um (resp. 70 and 160um). We reach deeper flux densities of 0.38 mJy at 70 and 3.1 at 160 um using a stacking analysis. We confirm the number count turnover at 24 and 70 um, and observe it for the first time at 160 um at about 20 mJy, together with a power-law behaviour below 10 mJy. These mid- and far-infrared counts: 1) are homogeneously built by combining fields of different depths and sizes, providing a legacy over about three orders of magnitude in flux density; 2) are the deepest to date at 70 and 160 um; 3) agree with previous published results in the common measured flux density range; 4) globally agree with the Lagache et al. (2004) model, except at 160 um where the model slightly overestimates the counts around 20 and 200 mJy.

Conclusions: These counts are integrated to estimate new CIB firm lower limits of 2.21-0.09+0.09 nW.m^-2.sr^-1 (resp. 5.2-0.4+0.4 and 9.0-1.1+1.1 nW.m^-2.sr^-1) at 24 um (resp. 70 and 160 um), and extrapolated to give new estimates of the CIB due to galaxies of 2.78-0.16+0.18 nW.m^-2.sr^-1 (resp. 6.4-0.6+0.7 and 14.6-2.9+7.1 nW.m^-2.sr^-1). Products (PSF, counts, CIB contributions, software) are publicly available for download at http://www.ias.u-psud.fr/irgalaxies/.

The 24 micron Source Counts in Deep Spitzer Surveys

Papovich, C., Dole, H., Egami, E., Le Floc'h, E., Perez-Gonzalez, P., Alonso-Herrero, A., Bai, L., Beichman, C., Blaylock, M., Engelbracht, C., Gordon, K., Hines, D., Misselt, K., Morrison, J., Mould, J., Muzerolle, J., Neugebauer, G., Richards, P., Rieke, G., Rieke, M., Rigby, J., Su, K., Young, E., ApJSS, 2004, 154, in press

Galaxy source counts in the infrared provide strong constraints on the evolution of the bolometric energy output from distant galaxy populations. We present the results from deep 24 micron imaging from Spitzer surveys, which include approximately 50,000 sources to an 80% completeness of 60 uJy. The 24 micron counts rapidly rise at near-Euclidean rates down to 5 mJy, increase with a super-Euclidean rate between 0.4 - 4 mJy, and converge below 0.3 mJy. The 24 micron counts exceed expectations from non-evolving models by a factor >10 at 0.1 mJy. The peak in the differential number counts corresponds to a population of faint sources that is not expected from predictions based on 15 micron counts from ISO. We argue that this implies the existence of a previously undetected population of infrared-luminous galaxies at z ~ 1-3. Integrating the counts to 60 uJy, we derive a lower limit on the 24 micron background intensity of 1.9 +/- 0.6 nW m-2 sr-1 of which the majority (~ 60%) stems from sources fainter than 0.4 mJy. Extrapolating to fainter flux densities, sources below 60 uJy contribute 0.8 {+0.9/-0.4} nW m-2 sr-1 to the background, which provides an estimate of the total 24 micron background of 2.7 {+1.1/-0.7} nW m-2 sr-1.

The paper is in press, ApJSS, 2004, 154, .
The paper is also available on the SSC web site and on astro-ph/0406035

Far Infrared Source Counts at 70 and 160 microns in Spitzer Deep Surveys

Dole, H., LeFloc'h, E., Perez-Gonzales, P., Papovich, C., Egami, E., Lagache, G., Alonso-Herrero, A., Engelbracht, C., Gordon, K., Hines, D., Krause, O., Misselt, K., Morrison, J., Rieke, G., Rieke, M., Rigby, J., Young, E., Bei, L., Blaylock, M., Neugebauer, G., Beichman, C., Frayer, D., Mould, J., Richards, P., 2004, ApJSS, 154, in press

We derive galaxy source counts at 70 and 160 microns using the Multiband Imaging Photometer for Spitzer (MIPS) to map the Chandra Deep Field South (CDFS) and other fields. At 70 microns, our observations extend upwards about two orders of magnitude in flux density from a threshold of 15 mJy, and at 160 microns they extend about an order of magnitude upward from 50 mJy. The counts are consistent with previous observations on the bright end. Significant evolution is detected at the faint end of the counts in both bands, by factors of two to three over no-evolution models. This evolution agrees well with models that indicate most ofthe faint galaxies lie at redshifts between 0.7 and 0.9. The new Spitzer data already resolves about 23% of the Cosmic Far Infrared Background at 70 microns and about 7% at 160 microns.

The paper is in press, ApJSS, 2004, 154, .
The paper is also available on the SSC web site and on astro-ph/0406021

Legacy Source Counts: Bethermin et al., 2009

all 2009 MIPS number counts in tgz

MIPS 24 Source Counts: differential [ascii table]
MIPS 70 Source Counts: differential [ascii table]
MIPS 160 Source Counts: differential [ascii table]

MIPS 70 Stacking Counts: differential [ascii table]
MIPS 160 Stacking Counts: differential [ascii table]

MIPS 24 CIB contribution [ascii table]
MIPS 70 CIB contribution [ascii table]
MIPS 160 CIB contribution [ascii table]



MIPS 24 micron Source Counts (2004, outdated)
MIPS 24 Source Counts: differential and integral [ascii table]

MIPS 70 micron Source Counts (2004, outdated)
MIPS 70 Source Counts: differential, CDFS [ascii table]
MIPS 70 Source Counts: differential, Marano [ascii table]
MIPS 70 Source Counts: differential, Bootes [ascii table]

MIPS 70 Source Counts: integral, CDFS [ascii table]
MIPS 70 Source Counts: integral, Marano [ascii table]
MIPS 70 Source Counts: integral, Bootes [ascii table]

MIPS 160 micron Source Counts (2004, outdated)
MIPS 160 Source Counts: differential, CDFS [ascii table]
MIPS 160 Source Counts: differential, Marano [ascii table]

MIPS 160 Source Counts: integral, CDFS [ascii table]
MIPS 160 Source Counts: integral, Marano [ascii table]

ALL 2004 MIPS Source Counts (outdated)
ALL MIPS Source Counts: all ascii tables [tgz]

PAHs contribution to the infrared output energy of the Universe at z~2

G. Lagache, H. Dole, J-L. Puget, P. G. Perez-Gonzalez, E. Le Floc'h, G. H. Rieke, C. Papovich, E. Egami, A. Alonso-Herrero, C. W. Engelbracht, K.D. Gordon, K. A. Misselt, and J. E. Morrison, ApJSS, 2004, in press

We present an updated phenomenological galaxy evolution model to fit the Spitzer 24, 70 and 160 micron number counts as well as all the previous mid and far infrared observations. Only a minor change of the co-moving luminosity density distribution in the previous model, combined with a slight modification of the starburst template spectra mainly between 12 and 30 microns, are required to fit all the data available. We show that the peak in the MIPS 24 microns counts is dominated by galaxies with redshift between 1 and 2, with a non negligible contribution from the z>2 galaxies (~30% at S=0.2 mJy). The very close agreement between the model and number counts at 15 and 24 microns strikingly implies that
(1) the PAHs (Policyclic Aromatic Hydrocarbons) features remain prominent in the redshift band 0.5 to 2.5 and
(2) the IR energy output has to be dominated by ~3 10^11 Lo to ~10^12 Lo galaxies from redshift 0.5 to 2.5.
Combining Spitzer with the Infrared Space Observatory (ISO) deep cosmological surveys gives for the first time an unbiased view of the infrared Universe from z=0 to z=2.5.

The paper is in press in ApJS (Spitzer Special Issue), 2004, 154

Go to the Model Web Page where you can download for instance the model, the predicted source counts.