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Mid-infrared spectroscopy of Spitzer-selected ultra-luminous starbursts at z ~ 2

Fiolet, N. and Omont, A. and Lagache, G. and Bertincourt, B. and Fadda, D. and Baker, A. J. and Beelen, A. and Berta, S. and Boulanger, F. and Farrah, D. and Kovács, A. and Lonsdale, A. and Owen, F. and Polletta, M. and Shupe, D. and Yan, L. (2010) Mid-infrared spectroscopy of Spitzer-selected ultra-luminous starbursts at z ~ 2. Astronomy and Astrophysics, 524 . A33. ISSN 0004-6361.

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Context. Spitzer's wide-field surveys and followup capabilities have allowed a new breakthrough in mid-IR spectroscopy up to redshifts ≥ 2, especially for 24 μm detected sources. Aims. We want to study the mid-infrared properties and the starburst and AGN contributions, of 24 μm sources at z ~ 2, through analysis of mid-infrared spectra combined with millimeter, radio, and infrared photometry. Mid-infrared spectroscopy allows us to recover accurate redshifts. Methods. A complete sample of 16 Spitzer-selected sources (ULIRGs) believed to be starbursts at z ~ 2 (“5.8 μm-peakers”) was selected in the (0.5 deg^2) J1064+56 SWIRE Lockman Hole field (“Lockman-North”). These sources have S_(24µ) > 0.5 mJy, a stellar emission peak redshifted to 5.8 μm, and r'_(Vega) > 23. The entire sample was observed with the low resolution units of the Spitzer/IRS infrared spectrograph. These sources have 1.2 mm observations with IRAM 30 m/MAMBO and very deep 20 cm observations from the VLA. Nine of our sources also benefit from 350 μm observation and detection from CSO/SHARC-II. All these data were jointly analyzed. Results. The entire sample shows good quality IRS spectra dominated by strong PAH features. The main PAH features at 6.2, 7.7, 8.6, and 11.3 μm have high S/N average luminosities of 2.90±0.31, 10.38±1.09, 3.62±0.27, and 2.29±0.26×10^(10) L_☉, respectively. Thanks to their PAH spectra, we derived accurate redshifts spanning from 1.750 to 2.284. The average of these redshifts is 2.017±0.038. This result confirms that the selection criteria of “5.8 μm-peakers” associated with a strong detection at 24 μm are reliable to select sources at z ~ 2. We have analyzed the different correlations between PAH emission and infrared, millimeter, and radio emissions. Practically all our sources are strongly dominated by starburst emission, with only one source showing an important AGN contribution. We have also defined two subsamples based on the equivalent width at 7.7 μm to investigate AGN contributions. Conclusions. Our sample contains strong starbursts and represents a particularly 24 μm-bright class of SMGs. The very good correlation between PAH and far-IR luminosities is now confirmed in high-z starburst ULIRGs. These sources show a small AGN contribution to the mid-IR, around ~20% or less in most cases.

Item Type:Article
Related URLs:
URLURL TypeDescription
Omont, A.0000-0002-4721-3922
Lagache, G.0000-0003-1492-2519
Fadda, D.0000-0002-3698-7076
Berta, S.0000-0002-0320-1532
Farrah, D.0000-0003-1748-2010
Polletta, M.0000-0001-7411-5386
Shupe, D.0000-0003-4401-0430
Yan, L.0000-0003-1710-9339
Additional Information:© 2010 ESO. Received 30 July 2010; Accepted 26 August 2010; Published online 22 November 2010. We thank Karin Menéndez-Delmestre and Hélène Roussel for their helpful contributions. This work is based primarily on IRS observations and observations made within the context of the SWIRE survey with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract. This work includes observations made with IRAM, which is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain). The VLA is operated by NRAO, the National Radio Astronomy Observatory, a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. The CSO is funded by NSF Cooperative Agreement AST-083826. G.L., B.B., A.B. and F.B. had support for this work provided by ANR “D-SIGALE” ANR-06–BLAN-0170 grant.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Agence Nationale pour la Recherche (ANR)ANR-06– BLAN-0170
Subject Keywords:galaxies: high-redshift; galaxies: starburst; galaxies: active; infrared: galaxies; submillimeter: galaxies; techniques: spectroscopic
Record Number:CaltechAUTHORS:20101222-113213930
Persistent URL:
Official Citation:Mid-infrared spectroscopy of Spitzer-selected ultra-luminous starbursts at z ~ 2 N. Fiolet, A. Omont, G. Lagache, B. Bertincourt, D. Fadda, A. J. Baker, A. Beelen, S. Berta, F. Boulanger, D. Farrah, A. Kovács, C. Lonsdale, F. Owen, M. Polletta, D. Shupe and L. Yan A&A 524 A33 (2010) DOI: 10.1051/0004-6361/201015504
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:21504
Deposited By: Jason Perez
Deposited On:23 Dec 2010 16:41
Last Modified:20 Nov 2019 05:15

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