No full-text available
To read the full-text of this research,
you can request a copy directly from the author.
6 CM observations of LBDS radio sources - Radio properties of blue radio galaxies
Abstract
The results of 6 cm observations of sources detected at 21 cm in the
Leiden-Berkeley Deep Survey are used to study the radio spectra of blue
radio galaxies. The mean spectral index between 6 and 21 cm of the
present sources is found to be steep. The blue radio galaxies are shown
to fall into two classes, those with radio morphologies similar to those
of classical red radio galaxies, and those which are very compact. Both
sets of characteristics can be interpreted as being typical of small
optically thick nonthermal cores no more than a few parsec in size.
Deep images were made with 10 arcsec resolution at 8.44 GHz with microjansky sensitivity of two regions previously imaged at several lower frequencies. The differential microjansky source count fits a power-law distribution with slope 2.3 +/- 0.2. This slope is roughly constant between 1.41 and 8.44 GHz and between S(v) = about 4 and X(v) = 1000 microJy. Unless the majority of radio sources at microJy levels are local, their average luminosity and/or space density probably has evolved with cosmic epoch in order to sustain the steep and nearly Euclidean value of the slope over such a large range in flux density. The 8.44 GHz counts probably converge at less than the 1 microjansky level if the evolutionary properties of these weak sources are similar to those of luminous gE radio galaxies and quasars. The median angular size of sources detected at 8.44 GHz at microjansky levels is 2.6 +/- 1.4 arcsec, and 40 percent of the source are larger than 5 arcsec.
Results are presented on an extensive project of direct CCD imaging of a
number of milliJansky and microJansky radio samples. The magnitude
distribution of the samples has a distribution which rises strongly for
r between 18 and 21, indicating the cosmological evolution of the mJy
radio sources, and gradually declines for r between 21 and 27, perhaps
signifying a redshift cutoff. Spectroscopy of the microJansky sources
shows that the blue, actively star-forming galaxies constitute the
majority group among the sub-mJy identifications and are probably
responsible for the upturn in the 1.4 GHz source counts at milliJansky
levels.