Alignment of radio and optical orientations in high-redshift radio galaxies

Chambers, K.; Miley, G. K.; Breugel, Wil van

doi:10.1038/329604a0

Cited by 297 publications

(212 citation statements)

References 20 publications

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“…HzRGs are often surrounded by giant halos of ionized gas, which radiate luminous emission lines in the UV/optical part of the spectrum. The continuum and the line emission, which can be spatially extended by as much as 100 kpc, are often elongated along the direction of the radio axis (Chambers et al 1987; for a review see McCarthy 1993).…”

Section: Introductionmentioning

confidence: 99%

Deep VLT spectroscopy of the $\vec{z}=$ 2.49 radio galaxy MRC 2104-242

Overzier

Röttgering

Kurk

et al. 2001

A&A

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Abstract. We present spectroscopic observations of the rest-frame UV line emission around radio galaxy MRC 2104-242 at z = 2.49, obtained with FORS1 on VLT Antu. The morphology of the halo is dominated by two spatially resolved regions. Lyα is extended by >12 along the radio axis, C IV and He II are extended by ∼8 . The overall spectrum is typical for that of high redshift radio galaxies. The most striking spatial variation is that N V is present in the spectrum of the region associated with the center of the galaxy hosting the radio source, the northern region, while absent in the southern region. Assuming that the gas is photoionized by a hidden quasar, the difference in N V emission can be explained by a metallicity gradient within the halo, with the northern region having a metallicity of Z ≈ 1.5 Z and Z ≤ 0.4 Z for the southern region. This is consistent with a scenario in which the gas is associated with a massive cooling flow or originates from the debris of the merging of two or more galaxies.

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Section: Introductionmentioning

confidence: 99%

Deep VLT spectroscopy of the $\vec{z}=$ 2.49 radio galaxy MRC 2104-242

Overzier

Röttgering

Kurk

et al. 2001

A&A

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“…This is reminiscent of the so-called 'alignment effect', in which optically luminous radio galaxies at intermediate and high redshifts tend to show alignments between the radioemitting structures and the UV-optical continuum and line emission (Chambers et al 1987;McCarthy et al 1987), as a result of illumination by the anisotropic radiation field of the AGN (e.g. Tadhunter et al 1998), or by the ionization of gas by shocks driven by the radio jets (e.g.…”

Section: Excitation: Diagnostic Diagramsmentioning

confidence: 99%

Witnessing the transformation of a quasar host galaxy at z = 1.6

Humphrey

Roche

Gomes

et al. 2015

Monthly Notices of the Royal Astronomical Society

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A significant minority of high redshift radio galaxy (HzRG) candidates show extremely red broad band colours and remain undetected in emission lines after optical 'discovery' spectroscopy. In this paper we present deep GTC optical imaging and spectroscopy of one such radio galaxy, 5C 7.245, with the aim of better understanding the nature of these enigmatic objects. Our g-band image shows no significant emission coincident with the stellar emission of the host galaxy, but does reveal faint emission offset by ∼3 ′′ (26 kpc) therefrom along a similar position angle to that of the radio jets, reminiscent of the 'alignment effect' often seen in the optically luminous HzRGs. This offset g-band source is also detected in several UV emission lines, giving it a redshift of 1.609, with emission line flux ratios inconsistent with photoionization by young stars or an AGN, but consistent with ionization by fast shocks. Based on its unusual gas geometry, we argue that in 5C 7.245 we are witnessing a rare (or rarely observed) phase in the evolution of quasar hosts when stellar mass assembly, accretion onto the back hole, and powerful feedback activity has eradicated its cold gas from the central ∼20 kpc, but is still in the process of cleansing cold gas from its extended halo.

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“…The second observation that may pertain to the uni cation of radio galaxies and quasars is that the restframe UV morphologies of high redshift (z > 1) radio galaxies tend to be aligned with their radio axes (McCarthy et al 1987, Chambers, Miley & van Breugel 1987. Understanding the origin of this alignment e ect is extremely important since radio galaxies are the most often used probes of galaxy evolution and cosmology (Lilly & Longair 1984, Spinrad 1986.…”

Section: Introductionmentioning

confidence: 99%

The Radio Galaxy 3C 265 Contains a Hidden Quasar Nucleus

Dey¹,

Spinrad

1996

ApJ

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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.

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Alignment of radio and optical orientations in high-redshift radio galaxies

Cited by 297 publications

References 20 publications

Deep VLT spectroscopy of the $\vec{z}=$ 2.49 radio galaxy MRC 2104-242

Deep VLT spectroscopy of the $\vec{z}=$ 2.49 radio galaxy MRC 2104-242

Witnessing the transformation of a quasar host galaxy at z = 1.6

The Radio Galaxy 3C 265 Contains a Hidden Quasar Nucleus

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