Optically Faint Microjansky Radio Sources Richards, E. A; Fomalont, E. B; Kellermann, K. I ...
Astrophysical journal/The Astrophysical journal,
12/1999, Letnik:
526, Številka:
2
Journal Article
Recenzirano
Odprti dostop
We report on the identifications of radio sources from our survey of the Hubble Deep Field (HDF) and the Small Selected Area 13 fields, both of which comprise the deepest radio surveys to date at 1.4 ...and 8.5 GHz, respectively. About 80% of the microjansky radio sources are associated with moderate-redshift starburst galaxies or active galactic nuclei within the I-magnitude range of 17-24 with a median of I=22 mag. Thirty-one (20%) of the radio sources are (1) fainter than I>25 mag, with two objects in the HDF IAB>28.5, (2) often identified with very red objects I-K>4, and (3) not significantly different in radio properties than the brighter objects. We suggest that most of these objects are associated with heavily obscured starburst galaxies with redshifts between 1 and 3. However, other mechanisms are discussed and cannot be ruled out with the present observations.
We made two new sensitive (rms noise Jy beam−1) high-resolution (θ = 3 0 and θ = 0 66 FWHM) S-band (2 < < 4 GHz) images covering a single JVLA primary beam (FWHM 14′) centered on J2000 , δ = +59°01′ ...in the Lockman Hole. These images yielded a catalog of 792 radio sources, 97.7 0.8% of which have infrared counterparts stronger than S 2 Jy at λ = 4.5 m. About 91% of the radio sources found in our previously published, comparably sensitive low-resolution (θ = 8″ FWHM) image covering the same area were also detected at 0 66 resolution, so most radio sources with S(3 GHz) 5 Jy have angular structure φ 0 66. The ratios of peak brightness in the 0 66 and 3″ images have a distribution indicating that most Jy radio sources are quite compact, with a median Gaussian angular diameter FWHM and an rms scatter φ 0 3 of individual sizes. Most of our Jy radio sources obey the tight far-infrared/radio correlation, indicating that they are powered by star formation. The median effective angular radius enclosing half the light emitted by an exponential disk is , so the median effective radius of star-forming galaxies at redshifts z ∼ 1 is .
This is the second of two papers describing the observations and source catalogues derived from sensitive 3-GHz images of the Lockman Hole North using the Karl G. Jansky Very Large Array (VLA). We ...describe the reduction and cataloguing process, which yielded an image with 8 arcsec resolution and instrumental noise of sn = 1.01 muJy beam^sup -1^ rms (before primary-beam corrections) and a catalogue of 558 sources detected above 5... We include details of how we estimate source spectral indices across the 2-GHz VLA bandwidth, finding a median index of -0.76 ± 0.04. Stacking of source spectra reveals a flattening of spectral index with decreasing flux density. We present a source count derived from the catalogue. We show a traditional count estimate compared with a completely independent estimate made via a P(D) confusion analysis, and find very good agreement. Cross-matches of the catalogue with X-ray, optical, infrared, radio, and redshift catalogues are also presented. The X-ray, optical and infrared data, as well as active galactic nuclei (AGN) selection criteria allow us to classify 10 per cent as radio-loud AGN, 28 per cent as radio-quiet AGN, and 58 per cent as star-forming galaxies, with only 4 per cent unclassified. (ProQuest: ... denotes formulae/symbols omitted.)
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