THE {approx}0.9 mJy SAMPLE: A MID-INFRARED SPECTROSCOPIC CATALOG OF 150 INFRARED-LUMINOUS, 24 {mu}m SELECTED GALAXIES AT 0.3 {<=} z {<=} 3.5
- Spitzer Science Center, California Institute of Technology, Mail Code 220-6, 1200 East California Boulevard, Pasadena, CA 91125 (United States)
- Infrared Processing and Analysis Center, California Institute of Technology, Mail Code 100-22, Pasadena, CA 91125 (United States)
- Department of Astronomy, Haverford College, Haverford, PA 19041 (United States)
- Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544-1001 (United States)
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 {approx}0.9 mJy at 24 {mu}m 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 {approx}> 1 and luminous IR galaxies at z < 1, as estimated from their monochromatic rest-frame 14 {mu}m 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 {mu}m 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 {mu}m PAH, the H{sub 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 {mu}m 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 {mu}m. The comparison of the 11.3 {mu}m PAH EW and the H-band effective radius, measured from Hubble Space Telescope data, indicates that sources with EWs {>=} 2 {mu}m, are typically more extended than {approx}3 kpc. However, there is no strong correlation between the MIR spectral type and the near-IR extent of the sources.
- OSTI ID:
- 21319590
- Journal Information:
- Astrophysical Journal, Vol. 701, Issue 2; Other Information: DOI: 10.1088/0004-637X/701/2/1123; Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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