Radio evolution of quasars at Z less than 1

Abstract

view Abstract Citations (64) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Radio Evolution of Quasars at Z <1 Hutchings, J. B. ; Price, Rob ; Gower, Ann C. Abstract We present and discuss a sample of 128 quasars with redshifts less than 1.0 observed at 6 cm and 20 cm with the A array of the VLA. Most of the data (91) are from observations made for the program in 1985 January of objects of redshift 0.35-1.0. For 40 of these, we used the 20 cm maps of Hintzen, Ulvestad, and Owen and obtained only 6 cm snapshots. The low-redshift objects in the sample are those of Gower and Hutchings. The sample is selected only to be well distributed in redshift and total radio luminosity, so that luminosity and redshift dependencies can be separated in significant subsamples. We present summaries of source types, sizes, luminosities, spectral indices, and detailed morphology (including core-lobe distances, lobe luminosities and their ratios, S-distortions, and curvatures). We discuss the distributions and correlations among these, and also among optical luminosities. We find that the source size envelope varies with both redshift and core luminosity, being smaller for high values of both. More luminous sources have greater core dominance, and the largest sources tend to have low-luminosity cores. Core variability tends to increase with luminosity and with redshift. Core luminosities range evenly over 4 orders of magnitude, but lobe luminosities are spread over only 2 orders of magnitude, near to 10^26^ W Hz^-1^. The optical luminosities have a much smaller range, but they appear to correlate with the core radio luminosity. This correlation is weaker at higher redshifts. The distribution of the ratio of core-lobe distances is consistent with a simple model of initial alternating ejection at nonrelativistic velocities. The ratios of lobe luminosities also show no evidence of relativistic beaming. In ~15% of the two-sided sources, there is evidence of continued alternating ejection, and in 30%, evidence for a small precession of the beam. Apparent bending angles of the lobes are largest for small sources, consistent with aspect effects and nonrelativistic motions. The evidence suggests a general evolution of individual sources as follows: the source is initially a luminous core only, whose luminosity falls with the passage of time. The lobes develop initially as a one-sided structure, but eventually form large triple sources with a fading core. We argue that this scenario is more likely than one of mildly relativistic beaming effects in the large-scale structure, as proposed by others. It seems likely that most sources have alternating ejection in two directions throughout their history. Many sources appear to precess in direction, indicating a long-term core duplicity, perhaps as a result of the tidal encounter, which is believed to initiate the sources, or of earlier merging events in their history. Publication: The Astrophysical Journal Pub Date: June 1988 DOI: 10.1086/166363 Bibcode: 1988ApJ...329..122H Keywords: Quasars; Radio Sources (Astronomy); Red Shift; Stellar Luminosity; Morphology; Sky Surveys (Astronomy); Astrophysics; QUASARS; RADIO SOURCES: GENERAL full text sources ADS | data products SIMBAD (91) NED (91)