Infrared Luminosities and Aromatic Features in the 24 μm Flux-limited Sample of 5MUSES

November 2010 • 2010ApJ...723..895W

Authors • Wu, Yanling • Helou, George • Armus, Lee • Cormier, Diane • Shi, Yong • Dale, Daniel • Dasyra, Kalliopi • Smith, J. D. • Papovich, Casey • Draine, Bruce • Rahman, Nurur • Stierwalt, Sabrina • Fadda, Dario • Lagache, G. • Wright, Edward L.

Abstract • 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 new empirical spectral templates from Spitzer data. The infrared luminosities of this sample range mostly from 10⁹ L _sun to 10^13.5 L _sun, with 83% in the range 10¹⁰ L _sun < L _IR < 10¹² L _sun. 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 6.2 μm 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.

Links

• PREPRINT http://arxiv.org/abs/1009.1633
• NED https://ned.ipac.caltech.edu/uri/NED::InRefcode/2010ApJ...723..895W
• ELECTR https://doi.org/10.1088%2F0004-637X%2F723%2F1%2F895
• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2010ApJ...723..895W
• PDF https://stacks.iop.org/0004-637X/723/895/pdf
• DATA http://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/723/895
• DATA https://irsa.ipac.caltech.edu/bibdata/2010/W/2010ApJ...723..895W.html