The infrared bright nuclei in the mid-infrared
- Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, Massachusetts 02138 (United States)
- Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, Hawaiian Islands 96822 (United States)
- Boston University Astronomy Department, 725 Commonwealth Avenue, Boston, Massachusetts 02215 (United States)
- Steward Observatory, University of Arizona, Tucson, Arizona 85721 (United States)
- Institute of Geophysics and Planetary Physics, Lawrence Livermore National Laboratory, POB 808-L413, Livermore, California 94550 (United States)
- University of Illinois, 103 Astronomy Building, 1002 West Green Street, Urbana, Illinois 61801 (United States)
- Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, Maryland 21218 (United States)
- Space Sciences Laboratory, University of California, Berkeley, California 94720 (United States)
We present arcsecond angular-resolution mid-IR images of three IR-bright galaxies, NGC 6240, IRAS 0518-25, and the NGC 3690-IC 694 (Arp 299) system, and we compare the sizes of their emission regions in the mid-IR and near-IR. In all these galaxies, most ({approximately}75{percent}) of the mid-IR flux, as measured in the IRAS 12 {mu}m observations, is found in our images to be concentrated within the central few hundred parsecs. In the two galaxies which show a single IR source in the nucleus, IRAS 0518-25 and IC 694, the mid-IR emission is more compact than the near-IR. This suggests that the mid-IR source, warm dust heated by an active galactic nucleus or an unresolved starburst, is more compact than the population of cooler, older stars. In the two galaxies which show double sources in the nucleus, the reverse is the case. That is, the mid-IR is more extended than the near-IR. Similar results are obtained for a handful of other galaxies for which we have high-resolution mid-IR data. Thus in our small sample, the double source nuclei contain starbursts which are more extended than the older stars and the single source nuclei do not. Some of the double sources seen in the IR bright galaxies, for example NGC 3690, are probably starbursts in conjunction with a galactic nucleus rather than twin galactic nuclei. {copyright} {ital 1997} {ital The American Astronomical Society}
- OSTI ID:
- 543761
- Journal Information:
- Astrophysical Journal, Vol. 485, Issue 2; Other Information: PBD: Aug 1997
- Country of Publication:
- United States
- Language:
- English
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