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MAMBO 1.2 mm OBSERVATIONS OF LUMINOUS STARBURSTS AT z similar to 2 IN THE SWIRE FIELDS

TitleMAMBO 1.2 mm OBSERVATIONS OF LUMINOUS STARBURSTS AT z similar to 2 IN THE SWIRE FIELDS
Publication TypeJournal Article
Year of Publication2009
AuthorsLonsdale, CJ, Polletta, MD, Omont, A, Shupe, D, Berta, S, Zylka, R, Siana, B, Lutz, D, Farrah, D, Smith, HE, Lagache, G, De Breuck, C, Owen, F, Beelen, A, Weedman, D, Franceschini, A, Clements, D, Tacconi, L, Afonso-Luis, A, Perez-Fournon, I, Cox, P, Bertoldi, F
JournalAstrophysical Journal
Volume692
Pagination422-442
Date PublishedFeb
ISBN Number0004-637X
Accession NumberWOS:000263553000038
Abstract

We report on-off pointed MAMBO observations at 1.2 mm of 61 Spitzer-selected star-forming galaxies from the Spitzer Wide Area Infrared Extragalactic Legacy survey (SWIRE). The sources are selected on the basis of bright 24 mu m fluxes (f(24 mu m) > 0.4 mJy) and of stellar dominated near-infrared spectral energy distributions in order to favor z similar to 2 starburst galaxies. The average 1.2 mm flux for the whole sample is 1.5 +/- 0.2 mJy. Our analysis focuses on 29 sources in the Lockman Hole field where the average 1.2 mm flux (1.9 +/- 0.3 mJy) is higher than in other fields (1.1 +/- 0.2 mJy). The analysis of the multiwavelength spectral energy distributions indicates that these sources are starburst galaxies with far-infrared luminosities from 10(12) to 10(13.3) L(circle dot), and stellar masses of similar to 0.2-6 x 10(11) M(circle dot). Compared to submillimeter selected galaxies (SMGs), the SWIRE-MAMBO sources are among those with the largest 24 mu m/1.2 mm flux ratios. The origin of such large ratios is investigated by comparing the average mid-infrared spectra and the stacked far-infrared spectral energy distributions of the SWIRE-MAMBO sources and of SMGs. The mid-infrared spectra, available for a handful of sources, exhibit strong polycyclic aromatic hydrocarbon (PAH) features, and a warm dust continuum. The warm dust continuum contributes similar to 34% of the mid-infrared emission, and is likely associated with an AGN component. This contribution is consistent with what is found in SMGs. The large 24 mu m/1.2 mm flux ratios are thus not due to AGN emission, but rather to enhanced PAH emission compared to SMGs. The analysis of the stacked far-infrared fluxes yields warmer dust temperatures than typically observed in SMGs. Our selection favors warm ultraluminous infrared sources at high-z, a class of objects that is rarely found in SMG samples. Indeed SMGs are not common among bright 24 mu m sources (e. g., only about 20% of SMGs have f(24 mu m) > 0.4 mJy). Our sample is the largest Spitzer-selected sample detected at millimeter wavelengths currently available.

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