Dasyra, Kalliopi M. and Yan, Lin and Helou, George and Sajina, Anna and Fadda, Dario and Zamojski, Michel and Armus, Lee and Draine, Bruce and Frayer, David (2009) The ~0.9 mJy Sample: A Mid-Infrared Spectroscopic Catalog of 150 Infrared-Luminous, 24 μm Selected Galaxies at 0.3 ≤ z ≤ 3.5. Astrophysical Journal, 701 (2). pp. 1123-1146. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20090825-141510421
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We present a catalog of mid-infrared (MIR) spectra of 150 infrared (IR) luminous galaxies in the Spitzer extragalactic first look survey obtained with the IR spectrograph on board the Spitzer Space Telescope. The sample is selected to be brighter than ~0.9 mJy at 24 μm and it has a redshift distribution in the range [0.3, 3.5], with a peak at z = 1. It primarily comprises ultraluminous IR galaxies (ULIRGs) at z ≳ 1 and luminous IR galaxies at z < 1, as estimated from their monochromatic rest-frame 14 μm luminosities. The number of sources with spectra that are dominated by an active galactic nucleus (AGN) continuum is 49, while 39 sources have strong, star formation related features. For this classification, we used the equivalent width (EW) of the 11.3 μm polycyclic aromatic hydrocarbon (PAH) feature. Several intermediate and high z starbursts have higher PAH EW than local ULIRGs, which could be indicative of an elevated star formation activity. Moreover, an increase in the AGN activity is observed with increasing z and luminosity, based on the decreasing EW of PAHs and the increasing [Ne III]/ [Ne II] ratio. Spectral stacking leads to the detection of weak features such as the 3.3 μm PAH, the H_2 0-0 S(1) and S(3) lines, and the [Ne V] line. We observe differences in the flux ratios of PAHs in the stacked spectra of IR-luminous galaxies with redshift or luminosity, which cannot be attributed to extinction effects since both the depth and the profile of the silicate absorption feature at 9.7 μm remain the same at z < 1 and z ≥ 1. When placing the observed galaxies on IR color-color diagrams, we find that the wedge defining AGNs comprises most sources with continuum-dominated spectra, but also contains many starbursts and sources with strong silicate absorption at 9.7 μm. The comparison of the 11.3 μm PAH EW and the H-band effective radius, measured from Hubble Space Telescope data, indicates that sources with EWs ≥ 2 μm, are typically more extended than ~3 kpc. However, there is no strong correlation between the MIR spectral type and the near-IR extent of the sources.
|Additional Information:||© 2009. The American Astronomical Society. Received 2009 April 21; accepted 2009 June 29; published 2009 July 29. This work was based on observations made with the Spitzer Space Telescope, which is operated by JPL/Caltech under a contract with NASA, and on observations made with the NASA/ ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. The observations are associated with the Spitzer programs 20629 and 40025, and the HST program 11142. The authors acknowledge support by NASA through awards issued by JPL/Caltech and through the grant HST-GO-11142.06-A awarded by the Space Telescope Science Institute.|
|Subject Keywords:||dust, extinction; galaxies: active; galaxies: evolution; galaxies: formation; galaxies: high-redshift; galaxies: interactions; galaxies: starburst; infrared: galaxies|
|Official Citation:||The ~0.9 mJy Sample: A Mid-Infrared Spectroscopic Catalog of 150 Infrared-Luminous, 24 μm Selected Galaxies at 0.3 ≤ z ≤ 3.5 Kalliopi M. Dasyra, Lin Yan, George Helou, Anna Sajina, Dario Fadda, Michel Zamojski, Lee Armus, Bruce Draine, and David Frayer 2009 ApJ 701 1123-1146 doi: 10.1088/0004-637X/701/2/1123|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||26 Aug 2009 15:55|
|Last Modified:||26 Dec 2012 11:15|
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