THE DEEP SWIRE FIELD. IV. FIRST PROPERTIES OF THE SUB-mJy GALAXY POPULATION: REDSHIFT DISTRIBUTION, AGN ACTIVITY, AND STAR FORMATION

Journal Article · Mon May 10 04:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/714/2/1305· OSTI ID:21448826

Strazzullo, Veronica; Pannella, Maurilio; Owen, Frazer N; Wang, Wei-Hao ^[1]; Bender, Ralf ^[2]; Morrison, Glenn E ^[3]

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1. National Radio Astronomy Observatory, 1003 Lopezville Rd., Socorro, NM 87801 (United States)
2. Universitaets-Sternwarte, Scheinerstrasse 1, Munich D-81679 (Germany)
3. Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 (United States)

We present a study of a 20 cm selected sample in the Deep Spitzer Wide-area InfraRed Extragalactic Legacy Survey Very Large Array Field, reaching a 5{sigma} limiting flux density at the image center of S{sub 1.4{sub GHz}} {approx} 13.5 {mu}Jy. In a 0.6 x 0.6 deg{sup 2} field, we are able to assign an optical/IR counterpart to 97% of the radio sources. Up to 11 passbands from the NUV to 4.5 {mu}m are then used to sample the spectral energy distribution (SED) of these counterparts in order to investigate the nature of the host galaxies. By means of an SED template library and stellar population synthesis models, we estimate photometric redshifts, stellar masses, and stellar population properties, dividing the sample into three sub-classes of quiescent, intermediate, and star-forming galaxies. We focus on the radio sample in the redshift range 0.3 < z < 1.3 where we estimate to have a redshift completeness higher than 90% and study the properties and redshift evolution of these sub-populations. We find that, as expected, the relative contributions of active galactic nuclei (AGNs) and star-forming galaxies to the {mu}Jy population depend on the flux density limit of the sample. At all flux levels, a significant population of 'green-valley' galaxies is observed. While the actual nature of these sources is not definitely understood, the results of this work may suggest that a significant fraction of faint radio sources might be composite (and possibly transition) objects, thus a simple 'AGN versus star-forming' classification might not be appropriate to fully understand what faint radio populations really are.

• OSTI ID: 21448826
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 714; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CLASSIFICATION
COSMOLOGY
ENERGY SPECTRA
EVOLUTION
FLUX DENSITY
GALACTIC EVOLUTION
GALAXIES
GALAXY NUCLEI
RED SHIFT
SPECTRA
STARS