期刊
ASTROPHYSICAL JOURNAL
卷 715, 期 1, 页码 506-540出版社
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/715/1/506
关键词
galaxies: ISM; infrared: galaxies; surveys; techniques: photometric
资金
- National Aeronautics and Space Administration (NASA) [1336000, 1407]
- National Science Foundation
- Science and Technology Facilities Council [ST/H00243X/1] Funding Source: researchfish
Using infrared photometry from the Spitzer Space Telescope, we perform the first inventory of aromatic feature emission (also commonly referred to as polycyclic aromatic hydrocarbon emission) for a statistically complete sample of star-forming galaxies in the local volume. The photometric methodology involved is calibrated and demonstrated to recover the aromatic fraction of the Infrared Array Camera 8 mu m flux with a standard deviation of 6% for a training set of 40 SINGS galaxies (ranging from stellar to dust dominated) with both suitable mid-infrared Spitzer Infrared Spectrograph spectra and equivalent photometry. A potential factor of 2 improvement could be realized with suitable 5.5 mu m and 10 mu m photometry, such as what may be provided in the future by the James Webb Space Telescope. The resulting technique is then applied to mid-infrared photometry for the 258 galaxies from the Local Volume Legacy (LVL) survey, a large sample dominated in number by low-luminosity dwarf galaxies for which obtaining comparable mid-infrared spectroscopy is not feasible. We find the total LVL luminosity due to five strong aromatic features in the 8 mu m complex to be 2.47 x 10(10) L(circle dot) with a mean volume density of 8.8 x 10(6) L(circle dot) Mpc(-3). Twenty-four of the LVL galaxies, corresponding to a luminosity cut at M(B) = -18.22, account for 90% of the aromatic luminosity. Using oxygen abundances compiled from the literature for 129 of the 258 LVL galaxies, we find a correlation between metallicity and the aromatic-to-total infrared emission ratio but not the aromatic-to-total 8 mu m dust emission ratio. A possible explanation is that metallicity plays a role in the abundance of aromatic molecules relative to the total dust content, but other factors, such as star formation and/or the local radiation field, affect the excitation of those molecules.
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