Redshifts and spectroscopy of very distant radio galaxies with strong emission lines

Abstract

The optical spectra of six newly observed 3CR radio galaxies, mostly with redshifts near unity, are unique with enormously strong [O II] emission. The observed equivalent widths of A 0 3727 range from 100 Á to about 2000 Á, and the luminosity in this single line exceeds 10 10 L© in the extreme case of 3C 368 (z = 1.13).The coarse line ratios and linewidths of [Oïl], [NeIII], [Ne v], and the occasional presence of MgII suggest a shock-excitation model for the gas in 3C 368, 3C 184, 3C 175.1, and possibly 3C 34. 3C 356 and 3C 280 have moderately strong [Nev] and may require a uv power-law continuum. A rough inverse-correlation exists between the emission lines velocity width and relative strengths of the high-ionization [Nev] and the strong low-ionization [Oil] lines. The energetics of a shock-origin for the low-ionization lines may be difficult unless a large reservoir of neutral gas is available.The shape of the thermal continuum of 3C 280 has been measured-this galaxy consists of old stars with a spectral distribution consistent with Bruzual models which have a last epoch of star formation ceasing at 2 > 4.We note that these very luminous radio galaxies are the ones which experience rapid evolution needed to explain the radio source counts. They are about 300 times more abundant (per unit co-moving volume) at 2 ~ 1.0 than locally (z ~ 0.1). Perhaps this rapid evolutionary turnoff at the present epoch represents some efficient utilization and later unavailability of an external fuel source, much more commonly available to gE galaxies a half-Hubble-time ago.

A search for distant radio galaxies from SUMSS and NVSS - III. Radio spectral energy distributions and the z- correlation

“…Kristian, Sandage & Katem 1974, 1978Smith & Spinrad 1980;Gunn et al 1981;Laing, Riley & Longair 1983;Perryman et al 1984;Spinrad & Djorgovski 1984;Spinrad et al 1985). Indeed, the first galaxy discovered above redshift one was found in this way (Spinrad 1982).…”

Ionization, shocks and evolution of the emission-line gas of distant 3CR radio galaxies

“… a Values of the [Ne iii ] 3869 / [Ne v ] 3426 ratio are taken from: 3C 22 –Rawlings et al (1995); 3C 217 & 3C 340 – Spinrad, private communication; 3C 265 & 3C 352 –Smith et al (1979); 3C 280 –Spinrad (1982); 3C 324 – Paper I; 3C 356 –Lacy & Rawlings (1994); 3C 368 –Stockton, Ridgway & Kellogg (1996); 3C 441 –Lacy et al (1998). …”

Deep spectroscopy of distant 3CR radio galaxies: the data

“…Their emission‐line luminosities are large, with the rest‐frame equivalent width of the [O ii ] 3727 line frequently exceeding 100 Å (e.g. Spinrad 1982). Indeed, the strong correlation between emission‐line luminosity and radio power (e.g.…”