MORPHOLOGIES OF RADIO-, X-RAY-, AND MID-INFRARED-SELECTED ACTIVE GALACTIC NUCLEI
- Jet Propulsion Laboratory, California Institute of Technology, MS 169-327, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)
We investigate the optical morphologies of candidate active galaxies identified at radio, X-ray, and mid-infrared wavelengths. We use the Advanced Camera for Surveys General Catalog (ACS-GC) to identify 372, 1360, and 1238 active galactic nucleus (AGN) host galaxies from Very Large Array, XMM-Newton, and Spitzer Space Telescope observations of the COSMOS field, respectively. We investigate both quantitative (GALFIT) and qualitative (visual) morphologies of these AGN host galaxies, split by brightness in their selection band. We find that the samples are largely distinct, though extensive overlap exists between certain samples, most particularly for the X-ray- and mid-IR-selected sources with unresolved optical morphologies. We find that the radio-selected AGNs are most distinct, with a very low incidence of having unresolved optical morphologies and a high incidence of being hosted by early-type galaxies. In comparison to X-ray-selected AGNs, mid-IR-selected AGNs have a slightly higher incidence of being hosted by disk galaxies. These morphological results conform to the results of Hickox et al. who studied the colors and large-scale clustering of AGNs and found a general association of radio-selected AGNs with 'red sequence' galaxies, mid-IR-selected AGNs with 'blue cloud' galaxies, and X-ray-selected AGNs straddling these samples in the 'green valley'. We also find that optical brightness scales with X-ray and mid-IR brightnesses, while little correlation is evident between optical and radio brightnesses. This suggests that X-ray- and mid-IR-selected AGNs have similar Eddington ratios, while radio-selected AGNs represent a different accretion mechanism with a lower and wider range of Eddington ratios. In the general scenario where AGN activity marks and regulates the transition from late-type disk galaxies into massive elliptical galaxies, this work suggests that the earlier stages are most evident as mid-IR-selected AGNs. Mid-IR emission is less susceptible to absorption than the relatively soft X-rays probed by XMM-Newton, which are seen at later stages in the transition. Radio-selected AGNs are then typically associated with minor bursts of activity in the most massive galaxies.
- OSTI ID:
- 21443260
- Journal Information:
- Astronomical Journal (New York, N.Y. Online), Vol. 140, Issue 2; Other Information: DOI: 10.1088/0004-6256/140/2/533; ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
COSMOLOGY AND ASTRONOMY
ABSORPTION
BRIGHTNESS
CAMERAS
CATALOGS
EMISSION
GALACTIC EVOLUTION
GALAXIES
GALAXY NUCLEI
MORPHOLOGY
SOFT X RADIATION
TELESCOPES
UNIVERSE
DOCUMENT TYPES
ELECTROMAGNETIC RADIATION
EVOLUTION
IONIZING RADIATIONS
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS
SORPTION
X RADIATION