ACTIVE GALACTIC NUCLEUS AND STARBURST RADIO EMISSION FROM OPTICALLY SELECTED QUASI-STELLAR OBJECTS
- National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States)
- Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States)
We used the 1.4 GHz NVSS to study radio sources in two color-selected QSO samples: a volume-limited sample of 1313 QSOs defined by M{sub i} < -23 in the redshift range 0.2 < z < 0.45 and a magnitude-limited sample of 2471 QSOs with m{sub r} {<=} 18.5 and 1.8 < z < 2.5. About 10% were detected above the 2.4 mJy NVSS catalog limit and are powered primarily by active galactic nuclei (AGNs). The space density of the low-redshift QSOs evolves as {rho}{proportional_to}(1 + z){sup 6}. In both redshift ranges the flux-density distributions and luminosity functions of QSOs stronger than 2.4 mJy are power laws, with no features to suggest more than one kind of radio source. Extrapolating the power laws to lower luminosities predicts the remaining QSOs should be extremely radio quiet, but they are not. Most were detected statistically on the NVSS images with median peak flux densities S{sub p}(mJy beam{sup -1}) Almost-Equal-To 0.3 and 0.05 in the low- and high-redshift samples, corresponding to spectral luminosities log [L{sub 1.4GHz}(W Hz{sup -1})] Almost-Equal-To 22.7 and 24.1, respectively. We suggest that the faint radio sources are powered by star formation at rates M-dot{approx}20M{sub Circled-Dot-Operator }yr{sup -1} in the moderate luminosity (median (M{sub i}) Almost-Equal-To -23.4) low-redshift QSOs and M-dot{approx}500M{sub Circled-Dot-Operator }yr{sup -1} in the very luminous ((M{sub i}) Almost-Equal-To -27.5) high-redshift QSOs. Such luminous starbursts [(log (L{sub IR}/L{sub Sun })) {approx} 11.2 and 12.6, respectively] are consistent with ''quasar mode'' accretion in which cold gas flows fuel both AGN and starburst.
- OSTI ID:
- 22126827
- Journal Information:
- Astrophysical Journal, Vol. 768, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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