WSRT detection of HI absorption in the z=3.4 damped Ly alpha system in PKS 0201+113

We report the detection of a faint narrow HI absorption line at a redshift of 3.38 against the quasar PKS 0201+113 which itself has an emission redshift of 3.61. The absorption line redshift agrees, to within the errors, with that of a damped Ly alpha line. The line has a halfwidth of about 9 km s(-1). Comparing the line equivalent width with the HI column density of the neutral gas we deduce a spin temperature for the gas of about 1100 K. In view of the fact that the spin temperature is remarkably similar to that derived for other high redshift absorption systems we consider it unlikely that it is due to different lines-of-sight for the ultraviolet continuum and the compact radio source. The high spin temperature may reflect a high kinetic temperature in most of the intervening HI. The HI in high redshift damped Ly alpha absorbers may therefore contain relatively more warm gas than our own and nearby galaxies. The damped Ly alpha system in PKS 0201+113 is currently the most distant system detected through the 21 cm line of atomic hydrogen. Its properties appear to be remarkably similar to those of systems at redshifts around 1. If damped Ly alpha systems are due to protodisks and/or disks of spiral galaxies, then galaxies similar to those of present day spiral galaxies were already forming at a redshift of 3.4. Following Wolfe ct al. (1976) we use the agreement between the redshifts of the 21 cm line and the optical resonance lines to constrain the possible variation, over the lookback time to the absorber, of the product of the fine structure constant, nuclear g factor for the proton, and the masses of the electron and proton. We obtain a 3 sigma upper limit of 5 x 10(-4) on the change in the ratio alpha(2)g(p)m(e)/m(p) at a redshift of z = 3.4. The corresponding 3 sigma upper limit to the rate of change of this ratio is 6 x 10(-14) yr(-1)

Radio spectra of Gigahertz Peaked Spectrum radio sources

A well defined sample of 72 Gigahertz Peaked Spectrum radio sources is compiled, having turnover frequencies in the range of 0.5 - 10 GHz. Using this sample, the canonical GPS radio spectrum is constructed, which is found to have a constant shape, independent of AGN type, redshift or radio luminosity. A possible deficiency of low turnover frequencies at high redshift is found, which may reflect a physical mechanism where turnover frequency and radio luminosity are correlated

WSRT detection of HI absorption in the z=3.4 damped Ly alpha system in PKS 0201+113

We report the detection of a faint narrow HI absorption line at a redshift of 3.38 against the quasar PKS 0201+113 which itself has an emission redshift of 3.61. The absorption line redshift agrees, to within the errors, with that of a damped Ly alpha line. The line has a halfwidth of about 9 km s(-1). Comparing the line equivalent width with the HI column density of the neutral gas we deduce a spin temperature for the gas of about 1100 K. In view of the fact that the spin temperature is remarkably similar to that derived for other high redshift absorption systems we consider it unlikely that it is due to different lines-of-sight for the ultraviolet continuum and the compact radio source. The high spin temperature may reflect a high kinetic temperature in most of the intervening HI. The HI in high redshift damped Ly alpha absorbers may therefore contain relatively more warm gas than our own and nearby galaxies. The damped Ly alpha system in PKS 0201+113 is currently the most distant system detected through the 21 cm line of atomic hydrogen. Its properties appear to be remarkably similar to those of systems at redshifts around 1. If damped Ly alpha systems are due to protodisks and/or disks of spiral galaxies, then galaxies similar to those of present day spiral galaxies were already forming at a redshift of 3.4. Following Wolfe ct al. (1976) we use the agreement between the redshifts of the 21 cm line and the optical resonance lines to constrain the possible variation, over the lookback time to the absorber, of the product of the fine structure constant, nuclear g factor for the proton, and the masses of the electron and proton. We obtain a 3 sigma upper limit of 5 x 10(-4) on the change in the ratio alpha(2)g(p)m(e)/m(p) at a redshift of z = 3.4. The corresponding 3 sigma upper limit to the rate of change of this ratio is 6 x 10(-14) yr(-1)

Hubble Space Telescope imaging of compact steep spectrum radio sources

We present Hubble Space Telescope WFPC2 images taken through a broad red filter (F702W) of 30 Third Cambridge Catalog compact steep spectrum (CSS) radio sources. We have overlaid radio maps taken from the literature on the optical images to determine the radio-optical alignment and to study detailed correspondence. All CSS sources for which the relative orientation between the optical and radio can be measured display good alignment between the optical and radio emission down to the lowest redshift in the sample, z similar to 0.1. The alignment effect does not occur at this relatively low redshift for the large-scale 3CR radio sources, which tend to show a significant alignment only at z > 0.6, as shown by McCarthy et al., Chambers et al., and de Koff et al. We find candidates for optical synchrotron hot spots in 3C 213.1 and 3C 380 and an optical jet in 3C 346