| タイトル | Origin of 12 micrometer Emission Across Galaxy Populations from Wise and ADSS Surveys |
| 著者（英） | Eisenhardt, P; Jarrett, T. H.; Stern, D.; Tsai, C.; Assef, R. J.; Yan, Lin; Leisawitz, D.; Donso, E.; Stanford, S. A. |
| 著者所属（英） | NASA Goddard Space Flight Center |
| 発行日 | 2012-03-01 |
| 言語 | eng |
| 内容記述 | We cross-matched Wide-field Infrared Survey Explorer sources brighter than 1 mJy at 12 micron with the Sloan Digital Sky Survey galaxy spectroscopic catalog to produce a sample of approx. 10(exp 5) galaxies at z = 0.08, the largest of its kind. This sample is dominated (70%) by star-forming (SF) galaxies from the blue sequence, with total IR luminosities in the range approx 10(exp 8)-10(exp 12) Solar L. We identify which stellar populations are responsible for most of the 12 micron emission. We find that most (approx 80%) of the 12 micron emission in SF galaxies is produced by stellar populations younger than 0.6 Gyr. In contrast, the 12 micron emission in weak active galactic nuclei (AGNs; L [O iii] < 10(exo 7) solar L ) is produced by older stars, with ages of approx 1-3 Gyr. We find that L(sub 12 micron) linearly correlates with stellar mass for SF galaxies. At fixed 12 micron luminosity, weak AGNs deviate toward higher masses since they tend to be hosted by massive, early-type galaxies with older stellar populations. SF galaxies and weak AGNs follow different L(sub 12 micron) - SFR (star formation rate) relations, with weak AGNs showing excess 12 micron emission at low SFR (0.02-1 solar M /yr). This is likely due to dust grains heated by older stars. While the specific star formation rate (SSFR) of SF galaxies is nearly constant, the SSFR of weak AGNs decreases by approx 3 orders of magnitude, reflecting the very different star formation efficiencies between SF galaxies and massive, early-type galaxies. Stronger type II AGNs in our sample (L(sub [O iii]) > 10(exp 7) solar L ), act as an extension of massive SF galaxies, connecting the SF and weak AGN sequences. This suggests a picture where galaxies form stars normally until an AGN (possibly after a starburst episode) starts to gradually quench the SF activity. We also find that 4.6-12 micron color is a useful first-order indicator of SF activity in a galaxy when no other data are available. |
| NASA分類 | Astronomy |
| レポートNO | GSFC.JA.01169.2012 |
| 権利 | Copyright |
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