The Redshift-Distance Relation. 111. Photometry and the Hubble Diagram for Radio Sources and the Possible Turn-On Time for QSOS

Abstract

view Abstract Citations (285) References (47) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Redshift-Distance Relation. 111. Photometry and the Hubble Diagram for Radio Sources and the Possible Turn-On Time for QSOS Sandage, Allan Abstract UBVphotometry is given for 59 radio galaxies, and is summarized for 103 radio and 25 radio- quiet quasars. The Rubble diagram for the radio galaxies is similar to that for first-ranked cluster galaxies, but is displaced faintward by 0.3 mag in the mean. If H0 = 50km s ' Mpc-1, then M = -22.98 with a = 0.49 mag for radio galaxies, and = -23.26 with a = 0.32 mag for first-ranked cluster galaxies. Radio galaxies can be as bright as the brightest E galaxies in clusters, but their luminosity distribution is asymmetric, reaching fainter limits. If the mass-to-light ratio is 30 in visual solar units, a galaxy must have a mass greater than 1012 to be a strong radio source. First-ranked cluster galaxies and the brightest radio galaxies have an upper limit to their mass that is of order l0' . The Rubble diagram for quasars is scattered, but no quasars lie to the right (fainter) of the radio galaxy distribution. This can be understood if a quasar consists of a normal strong radio galaxy upon which a nonthermal component is superposed which has a wide intrinsic dispersion (factor of 50) to its optical luminosity. Quasars are then at their Rubble distance. The apparent cutoff in quasar redshifts near z = 2.8 is examined for selection effects that could produce it artificially. If the cutoff is real, it may be the time of the birth of the first quasars, although the suggested redshift is unexpectedly small. At z = 3 in a q0 = + 1 universe, the look-back time is 89 percent of the Friedmana age. Assessment of the observational selection effects shows that none are positively established that would produce the cutoff artificially. Special observations to test its reality are straightforward and can be made with existing ground-based telescopes, but they have not yet been done. Previously unreported photometry for 22 quasars is listed in an appendix. Publication: The Astrophysical Journal Pub Date: November 1972 DOI: 10.1086/151764 Bibcode: 1972ApJ...178...25S full text sources ADS | data products NED (235) SIMBAD (97) Related Materials (9) Part 1: 1972ApJ...173..485S Part 2: 1972ApJ...178....1S Part 4: 1973ApJ...180..687S Part 5: 1973ApJ...183..711S Part 6: 1973ApJ...183..731S Part 7: 1973ApJ...183..743S Part 8: 1975ApJ...202..563S Part 9: 1986ApJ...307....1S Part 10: 1987ApJ...317..557S