THE TWO-COMPONENT RADIO LUMINOSITY FUNCTION OF QUASI-STELLAR OBJECTS: STAR FORMATION AND ACTIVE GALACTIC NUCLEUS

Journal Article · Tue Sep 20 04:00:00 EDT 2011 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/739/1/L29· OSTI ID:21565463

Kimball, Amy E; Kellermann, K I; Condon, J J ^[1]; Ivezic, Zeljko ^[2]

---

1. National Radio Astronomy Observatory, 520 Edgemont Rd., Charlottesville, VA 22903 (United States)
2. Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States)

Despite decades of study, it remains unclear whether there are distinct radio-loud and radio-quiet populations of quasi-stellar objects (QSOs). Early studies were limited by inhomogeneous QSO samples, inadequate sensitivity to probe the radio-quiet population, and degeneracy between redshift and luminosity for flux-density-limited samples. Our new 6 GHz Expanded Very Large Array (EVLA) observations allow us for the first time to obtain nearly complete (97%) radio detections in a volume-limited color-selected sample of 179 QSOs more luminous than M{sub i} = -23 from the Sloan Digital Sky Survey (SDSS) Data Release Seven in the narrow redshift range 0.2 < z < 0.3. The dramatic improvement in radio continuum sensitivity made possible with the new EVLA allows us, in 35 minutes of integration, to detect sources as faint as 20 {mu}Jy, or log [L{sub 6GHz}(W Hz{sup -1})] {approx} 21.5 at z = 0.25, well below the radio luminosity, log [L{sub 6}(W Hz{sup -1})] {approx} 22.5, that separates star-forming galaxies from radio-loud active galactic nuclei (AGNs) driven by accretion onto a supermassive black hole. We calculate the radio luminosity function (RLF) for these QSOs using three constraints: (1) EVLA 6 GHz observations for log [L{sub 6}(W Hz{sup -1})] < 23.5, (2) NRAO-VLA Sky Survey observations for log [L{sub 6}(W Hz{sup -1})] > 23.5, and (3) the total number of SDSS QSOs in our volume-limited sample. We show that the RLF can be explained as a superposition of two populations, dominated by AGNs at the bright end and star formation in the QSO host galaxies at the faint end.

• OSTI ID: 21565463
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 1 Vol. 739; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
COSMIC RADIO SOURCES
EVOLUTION
FLUX DENSITY
GALAXIES
GALAXY NUCLEI
LUMINOSITY
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
QUASARS
RED SHIFT
STAR EVOLUTION