A Polarimetric Search for Hidden Quasars in Three Radio-selected Ultraluminous Infrared Galaxies
- Institute of Geophysics and Planetary Physics, Lawrence Livermore National Laboratory, 7000 East Avenue, P.O. Box 808, L413, Livermore, CA 94550 (United States)
- Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States)
- Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States)
- Department of Physics, University of California, Santa Barbara, CA 93106 (United States)
We have carried out a spectropolarimetric search for hidden broad-line quasars in three ultraluminous infrared galaxies (ULIRGs) discovered in the positional correlations between sources detected in deep radio surveys and the {ital IRAS} Faint Source Catalog. Only the high-ionization Seyfert 2 galaxy TF J1736{plus}1122 is highly polarized, displaying a broad-line spectrum visible in polarized light. The other two objects, TF J1020{plus}6436 and FF J1614{plus}3234, display spectra dominated by a population of young (A type) stars similar to those of {open_quotes}E{plus}A{close_quotes} galaxies. They are unpolarized, showing no sign of hidden broad-line regions. The presence of young starburst components in all three galaxies indicates that the ULIRG phenomenon encompasses both active galactic nuclei (AGNs) and starburst activity, but the most energetic ULIRGs do not necessarily harbor {open_quotes}buried quasars.{close_quotes} We find that a luminous infrared galaxy is most likely to host an obscured quasar if it exhibits a high-ionization ([O iii] {lambda}5007/H{beta} {approx_gt}5) spectrum typical of a {open_quotes}classic{close_quotes} Seyfert 2 galaxy with little or no Balmer absorption lines, is {open_quotes}ultraluminous{close_quotes} (L{sub IR} {approx_gt}10{sup 12} {ital L}{sub {circle_dot}}), and has a {open_quotes}warm{close_quotes} IR color (f{sub 25} /f{sub 60} {approx_gt}0.25). The detection of hidden quasars in this group but not in the low-ionization, starburst-dominated ULIRGs (classified as LINERs or H ii galaxies) may indicate an evolutionary connection, with the latter being found in younger systems. {copyright} {ital {copyright} 1999.} {ital The American Astronomical Society}
- OSTI ID:
- 357209
- Journal Information:
- Astrophysical Journal, Vol. 516, Issue 1; Other Information: PBD: May 1999
- Country of Publication:
- United States
- Language:
- English
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