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The 12 μm ISO-ESO-Sculptor and 24 μm Spitzer faint counts reveal a population of ULIRGs as dusty massive ellipticals: Evolution by types and cosmic star formation

Rocca-Volmerange, B. and de Lapparent, V. and Seymour, N. and Fioc, M. (2007) The 12 μm ISO-ESO-Sculptor and 24 μm Spitzer faint counts reveal a population of ULIRGs as dusty massive ellipticals: Evolution by types and cosmic star formation. Astronomy and Astrophysics, 475 (3). pp. 801-812. ISSN 0004-6361. doi:10.1051/0004-6361:20065217.

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Context. Multi-wavelength galaxy number counts provide clues to the nature of galaxy evolution. The interpretation per galaxy type of the mid-IR faint counts obtained with ISO and Spitzer, consistent with the analysis of deep UV-optical-near IR galaxy counts, provide new constraints on the dust and stellar emission. Discovering the nature of new populations, such as high redshift ultra-luminous (≥10^(12) L_⊙) infrared galaxies (ULIRGs), is also crucial for understanding galaxy evolution at high redshifts. Aims. We first present the faint galaxy counts at 12 μm from the catalogue of the ISO-ESO-Sculptor Survey (ISO-ESS) published in a companion article (Seymour et al. 2007a, A&A, 475, 791). They go down to 0.31 mJy after corrections for incompleteness. We verify the consistency with the existing ISO number counts at 15 μm. Then we analyse the 12 μm (ISO-ESS) and the 24 μm (Spitzer) faint counts, to constrain the nature of ULIRGs, the cosmic star formation history and time scales for mass buildup. Methods. We show that the “normal” scenarios in our evolutionary code PÉGASE, which had previously fitted the deep UV-opticalnear IR counts, are unsuccessful at 12 μm and 24 μm. We thus propose a new ULIRG scenario adjusted to the observed cumulative and differential 12 μm and 24 μm counts and based on observed 12 μm and 25 μm IRAS luminosity functions and evolutionary optical/mid-IR colours from PÉGASE. Results. We succeed in simultaneously modelling the typical excess observed at 12 μm, 15 μm (ISO), and 24 μm (Spitzer) in the cumulative and differential counts by only changing 9% of normal galaxies (1/3 of the ellipticals) into ultra-bright dusty galaxies evolving as ellipticals, and interpreted as distant ULIRGs. These objects present similarities with the population of radio-galaxy hosts at high redshift. No number density evolution is included in our models even if minor starbursts due to galaxy interactions remain compatible with our results. Conclusions. Higher spectral and spatial resolution in the mid-IR, together with submillimeter observations using the future Herschel observatory, will be useful to confirm these results.

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Seymour, N.0000-0003-3506-5536
Additional Information:© ESO 2007. Received 16 March 2006. Accepted 20 June 2007. Seymour acknowledges financial support from the European Network “Probing the Origin of the Extragactic Background Radiation” (POE) while at the Institut d’Astrophysique de Paris (IAP). We also thank Prof. L. Woltjer for his stimulating interest in this ISO observational program and Damien Le Borgne for his fruitful suggestions.
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European NetworkUNSPECIFIED
Subject Keywords:infrared : galaxies; galaxies : evolution; galaxies : photometry; cosmology : observations
Issue or Number:3
Record Number:CaltechAUTHORS:20100223-111955718
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Official Citation:The 12 μm ISO-ESO-Sculptor and 24 μm Spitzer faint counts reveal a population of ULIRGs as dusty massive ellipticals - Evolution by types and cosmic star formation B. Rocca-Volmerange, V. de Lapparent, N. Seymour and M. Fioc A&A 475 (3) 801-812 (2007) DOI: 10.1051/0004-6361:20065217
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:17564
Deposited By: Tony Diaz
Deposited On:02 Mar 2010 17:16
Last Modified:08 Nov 2021 23:36

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