Wu, Yanling and Helou, George and Armus, Lee and Cormier, Diane and Shi, Yong and Dale, Daniel and Dasyra, Kalliopi and Smith, J. D. and Papovich, Casey and Draine, Bruce and Rahman, Nurur and Stierwalt, Sabrina and Fadda, Dario and Lagache, G. (2010) Infrared luminosities and aromatic features in the 24 μm flux-limited sample of 5muses. Astrophysical Journal, 723 (1). pp. 895-914. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20101208-080506134
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We study a 24 μm selected sample of 330 galaxies observed with the infrared spectrograph for the 5 mJy Unbiased Spitzer Extragalactic Survey. We estimate accurate total infrared luminosities by combining mid-IR spectroscopy and mid-to-far infrared photometry, and by utilizing newempirical spectral templates from Spitzer data. The infrared luminosities of this sample range mostly from 10^9 L_⊙ to 10^(13.5) L_⊙,with 83% in the range 10^(10) L_⊙ < L_(IR) < 10^(12) L_⊙. The redshifts range from 0.008 to 4.27, with a median of 0.144. The equivalent widths of the 6.2 μm aromatic feature have a bimodal distribution, probably related to selection effects. We use the 6.2μm polycyclic aromatic hydrocarbon equivalent width (PAH EW) to classify our objects as starburst (SB)-dominated (44%), SB-AGN composite (22%), and active galactic nucleus (AGN)-dominated (34%). The high EW objects (SB-dominated) tend to have steeper mid-IR to far-IR spectral slopes and lower L_(IR) and redshifts. The low EW objects (AGN-dominated) tend to have less steep spectral slopes and higher L_(IR) and redshifts. This dichotomy leads to a gross correlation between EW and slope, which does not hold within either group. AGN-dominated sources tend to have lower log(L_(PAH7.7 μm)/L_(PAH11.3 μm)) ratios than star-forming galaxies, possibly due to preferential destruction of the smaller aromatics by the AGN. The log(L_(PAH7.7 μm)/L_(PAH11.3 μm)) ratios for star-forming galaxies are lower in our sample than the ratios measured from the nuclear spectra of nearby normal galaxies, most probably indicating a difference in the ionization state or grain size distribution between the nuclear regions and the entire galaxy. Finally, we provide a calibration relating the monochromatic continuum or aromatic feature luminosity to L_(IR) for different types of objects.
|Additional Information:||© 2010 The American Astronomical Society. Received 2010 May 25; accepted 2010 September 2; published 2010 October 15. We thank the anonymous referee whose comments have helped to improve this paper. This work was based on observations made with the Spitzer Space Telescope, which is operated by JPL/Caltech under a contract with NASA. The observations are associated with the Spitzer Legacy Program 40539. The authors acknowledge support by NASA through awards issued by JPL/Caltech. This research has made use of the NASA/ IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.|
|Subject Keywords:||galaxies: active, galaxies: starburst, infrared: galaxies, surveys|
|Classification Code:||PACS: 95.80.+p; 95.85Hp; 98.54,Ep; 98.62.Ai; 98.54.Cm; 98.62.Qz|
|Official Citation:||Yanling Wu et al 2010 ApJ 723 895 doi: 10.1088/0004-637X/723/1/895|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Benjamin Perez|
|Deposited On:||08 Dec 2010 16:43|
|Last Modified:||26 Dec 2012 12:44|
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