The spitzer infrared nearby galaxies survey: A high-resolution spectroscopy anthology

  • D. A. Dale
  • , J. D.T. Smith
  • , E. A. Schlawin
  • , L. Armus
  • , B. A. Buckalew
  • , S. A. Cohen
  • , G. Helou
  • , T. H. Jarrett
  • , L. C. Johnson
  • , J. Moustakas
  • , E. J. Murphy
  • , H. Roussel
  • , K. Sheth
  • , S. Staudaher
  • , C. Bot
  • , D. Calzetti
  • , C. W. Engelbracht
  • , K. D. Gordon
  • , D. J. Hollenbach
  • , R. C. Kennicutt
  • S. Malhotra

Research output: Contribution to journalArticlepeer-review

74 Scopus citations

Abstract

High-resolution mid-infrared spectra are presented for 155 nuclear and extranuclear regions from the Spitzer Infrared Nearby Galaxies Survey (SINGS). The fluxes for nine atomic forbidden and three molecular hydrogen mid-infrared emission lines are also provided, along with upper limits in key lines for infrared-faint targets. The SINGS sample shows a wide range in the ratio of [S III] 18.71 μm/[S III] 33.48 μm, but the average ratio of the ensemble indicates a typical interstellar electron density of 300-400 cm-3 on ∼23″ × 15″ scales and 500-600 cm-3 using ∼11″ × 9″ apertures, independent of whether the region probed is a star-forming nuclear, a star-forming extranuclear, or an active galactic nuclei (AGN) environment. Evidence is provided that variations in gas-phase metallicity play an important role in driving variations in radiation field hardness, as indicated by [Ne III] 15.56 μm/[Ne II] 12.81 μm, for regions powered by star formation. Conversely, the radiation hardness for galaxy nuclei powered by accretion around a massive black hole is independent of metal abundance. Furthermore, for metal-rich environments AGN are distinguishable from star-forming regions by significantly larger [Ne III] 15.56 μm/[Ne II] 12.81 μm ratios. Finally, [Fe II] 25.99 μm/[Ne II] 12.81 μm versus [Si II] 34.82 μm/[S III] 33.48 μm also provides an empirical method for discerning AGN from normal star-forming sources. However, similar to [Ne III] 15.56 μm/[Ne II] 12.81 μm, these mid-infrared line ratios lose their AGN/star-formation diagnostic powers for very low metallicity star-forming systems with hard radiation fields.

Original languageEnglish (US)
Pages (from-to)1821-1834
Number of pages14
JournalAstrophysical Journal
Volume693
Issue number2
DOIs
StatePublished - Mar 10 2009
Externally publishedYes

Keywords

  • accretion, accretion
  • disks
  • galaxies: active
  • galaxies: jets

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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