The Radio Galaxy 3C 265 Contains a Hidden Quasar Nucleus

Abstract

We report the discovery of broad MgII emission from the high redshift radio galaxy 3C265 (z=0.81). We detect the broad line in the nuclear spectrum and in the spatially extended galaxian component, both near the nucleus and in the spectrum of an o -nuclear knot located 31 kpc south east of the nucleus of the galaxy. These data provide strong support for the simplest form of the uni cation hypothesis, that radio galaxies are quasars whose optical radiation is directed in the plane of the sky rather than into our line of sight. These data also strongly support the scattering model for the alignment of the UV continuum emission with the radio axis. In 3C265, if the axis of the anisotropically emitted UV continuum radiation is identi ed with the major axis of the radio source, then the observed rest frame UV continuum emission implies that the opening angle of the radiation cone is large (half angle 45 ).We also derive a mass estimate of 8 10 10 M for the central region of 3C265 from its rotation curve. The implied mass-to-light ratio is low (M/L 2), and suggests that a signi cant fraction of the rest frame UV continuum emission from this galaxy is dominated by reprocessed radiation from the buried AGN. Finally, we detect the CaII 3933 K line in absorption in the integrated spectrum of 3C265. This provides direct spectroscopic evidence for the existence of stars in a high redshift radio galaxy.

Thermal-infrared imaging of 3C radio galaxies at z 1

“…The quantitative results of this analysis are presented in Table 5; also listed are the fluxes estimated using the intrinsic nuclear fluxes and extinctions listed in Table 4, accounting for the Galactic extinctions given in Table 6. The exclusion of 3C 265 from this analysis is not a great problem, because its predicted transmitted nuclear flux is several orders of magnitude fainter than the detection limit in the HST images, and spectropolarimetry (Dey & Spinrad 1996) suggests that any compact component is more likely to be light scattered close to the nucleus. The agreement between predicted and observed HST fluxes is generally very good, with the exception of the F555W flux of 3C 41, which is predicted to be much fainter than is observed.…”

The radio galaxy K-z relation: The $\mathsf{10^{12}}~$M\odot mass limit

“…At high z, mass estimates of radio galaxy hosts are rare. From an incomplete rotation curve, Dey et al (1996) derived a mass of 10 11 M for 3C 265 (z = 0.81). Using HST/NICMOS observations, Zirm et al (2003) confirmed that radio galaxy hosts are massive, even at high z. Stellar masses estimated by fitting stellar energy distributions (SEDs) to the NICMOS data are between 3 and 8 × 10 11 M .…”

The radio--optical correlation in steep-spectrum quasars

“…If the compact quasar nucleus is hidden from our direct view, as is now known to be the case in some radio galaxies (e.g. Dey & Spinrad 1996), then in the context of the orientation-based unified schemes the radio-optical relation predicts that a high narrow-line luminosity L NLR is inescapable. The radio-optical relation is then an obvious candidate for the cause of the relation between narrow-line luminosity L NLR and L 408 for radio sources (Baum & Heckman 1989;Rawlings & Saunders 1991;McCarthy 1993;Rawlings 1993;Jackson & Rawlings 1997).…”

“…Antonucci 1993;Antonucci, Hurt & Kinney 1994;Dey & Spinrad 1996;Ogle et al 1997). However, the popular notion that the probability of obscuration is a strong function of the angle between the jet axis and the line of sight (e.g.…”