A mid-infrared spectroscopic study of submillimeter galaxies: Luminous starbursts at high redshift

E. Valiante, D. Lutz, E. Sturm, R. Genzel, L. J. Tacconi, M. D. Lehnert, Andrew Baker

Research output: Contribution to journalArticle

108 Scopus citations

Abstract

We present rest-frame mid-infrared spectroscopy of a sample of 13 submillimeter galaxies, obtained using the Infrared Spectrograph (IRS) on board the Spitzer Space Telescope, The sample includes exclusively bright objects from blank fields and cluster lens-assisted surveys that have accurate interferometric positions. We find that the majority of spectra are well fitted by a starburst template or by the superposition of PAH emission features and a weak mid-infrared continuum, the latter a tracer of active galactic nuclei (AGNs; including Compton-thick ones). We obtain mid-infrared spectroscopic redshifts for all nine sources detected with IRS. For three of them the redshifts were previously unknown. The median value of the redshift distribution is z ∼ 2.8 if we assume that the four IRS nondetections are at high redshift. The median for the IRS detections alone is z ∼ 2.7. Placing the IRS nondetections at similar redshift would require rest-frame mid-IR obscuration larger than is seen in local ULIRGs. The rest-frame mid-infrared spectra and mid- to far-infrared spectral energy distributions are consistent with those of local ultraluminous infrared galaxies but scaled up further in luminosity. The mid-infrared spectra support the scenario that submillimeter galaxies are sites of extreme star formation, rather than X-ray-obscured AGNs, and represent a critical phase in the formation of massive galaxies.

Original languageEnglish (US)
Pages (from-to)1060-1071
Number of pages12
JournalAstrophysical Journal
Volume660
Issue number2 I
DOIs
StatePublished - May 10 2007

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • Galaxies: active
  • Galaxies: distances and redshifts
  • Galaxies: starburst
  • Infrared: galaxies

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    Valiante, E., Lutz, D., Sturm, E., Genzel, R., Tacconi, L. J., Lehnert, M. D., & Baker, A. (2007). A mid-infrared spectroscopic study of submillimeter galaxies: Luminous starbursts at high redshift. Astrophysical Journal, 660(2 I), 1060-1071. https://doi.org/10.1086/513306