The radio and optical axes of radio elliptical galaxies

Sansom, A. E.; Danziger, I. J.; Ekers, R. D.; Fosbury, R. A. E.; Goss, W. M.; Monk, A. S.; Shaver, P. A.; Sparks, W. B.; Wall, J. V.

doi:10.1093/mnras/229.1.15

Cited by 27 publications

(19 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Several previous studies also reported the same lack of relation between the radio and host optical axes for FR-IIs (Palimaka et al 1979;Guthrie 1980;Sansom et al 1987). Curiously, it was only more recently that this study was performed for FR-I type radio galaxies.…”

Section: Relative Orientations Of Radio and Host Optical Axes And Thesupporting

confidence: 66%

Understanding the Fanaroff–riley Radio Galaxy Classification

Saripalli

2012

The Astronomical Journal

View full text Add to dashboard Cite

A simple, yet profoundly far-reaching classification scheme based on extended radio morphologies of radio galaxies, the Fanaroff-Riley (FR) classification has been a cornerstone in our understanding of radio galaxies. Over the decades since the recognition that there are two basic types of radio galaxy morphologies, there have been several findings in different wavebands that have reported properties on different scales. Although it is realized that there may be intrinsic as well as external causes, an overarching view of how we may understand the two morphological types is missing. With the radio-power-absolute-magnitude relation (the Owen-Ledlow diagram) as a backdrop, we review and develop an understanding of the two radio galaxy types in light of what is known about them. We have for the first time included the dust properties of the two FR classes together with the relative orientations of dust, host major axis, and the radio axis to present a qualitative framework within which to understand the conditions under which they form. We discuss how the host elliptical and its history can explain the distribution of radio galaxies in the Owen-Ledlow diagram. The mass of the host elliptical galaxy is a crucial player in deciding what type of a radio galaxy it can host in what conditions. Benign conditions, characterized by natural evolutionary processes, most easily give rise to FR-I-type sources in ellipticals of all mass regimes, whereas with FR-IIs we reason that it is hard to form them without mergers. In undisturbed conditions elliptical galaxies appear to acquire stable states where the black hole axis settles along the host minor axis. With the steady conditions and the continuous supply of ambient gas, the FR-Is in principle may be powered for a long time. Aided by mergers and interactions, low-mass ellipticals more easily form FR-II-type sources than more massive hosts. LEG FR-IIs may include dying as well as restarted FR-II radio galaxies.

show abstract

Section: Relative Orientations Of Radio and Host Optical Axes And Thesupporting

confidence: 66%

Understanding the Fanaroff–riley Radio Galaxy Classification

Saripalli

2012

The Astronomical Journal

View full text Add to dashboard Cite

show abstract

“…These are likely to be negligible in the case of star-forming galaxies which can be assumed to be disc-like with roughly cospatial radio and optical emission, but could be important in ellipticals which can be triaxial (Binney 1978). The possible effects of triaxiality on the observed radio/optical PA distribution were simulated by Sansom et al (1987). Their simulations show that, for oblate spheroidal galaxies, those with jets along the minor axis should show the kind of alignments we observe, whereas other configurations lead to much less well-defined PA difference distributions; any triaxiality only serves to blur to the kind of biases we observe.…”

Section: Intrinsic Alignment Between the Radio And Optical Structuresmentioning

confidence: 99%

“…There has been a long history of searching for alignments between the structures of radio sources and those of their host galaxies and generally the results have been inconclusive (e.g. Mackay 1971;Palimaka et al 1979;Valtonen 1983;Birkinshaw & Davies 1985;Sansom et al 1987), though in most investigations there appear to be a preponderance of objects where the radio elongation is more aligned with the optical minor axis than the major axis. The clearest result was obtained by Condon, Frayer & Broderick (1991) who found that extended radio jets in 125 UGC galaxies were preferentially aligned with the optical minor axes of their hosts, with the effect being strongest for elliptical galaxies.…”

Section: Introductionmentioning

confidence: 99%

Radio and optical orientations of galaxies

Battye

Browne

2009

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

We investigate the correlations between optical and radio isophotal position angles for 14302 SDSS galaxies with $r$ magnitudes brighter than 18 and which have been associated with extended FIRST radio sources. We identify two separate populations of galaxies using the colour, concentration and their principal components. Surprisingly strong statistical alignments are found: late-type galaxies are overwhelmingly biased towards a position angle differences of $0^{\circ}$ and early-type galaxies to $90^{\circ}$. The late-type alignment can be easily understood in terms of the standard picture in which the radio emission is intimately related to areas of recent star-formation. In early-type galaxies the radio emission is expected to be driven by accretion on to a nuclear black hole. We argue that the observed correlation of the radio axis with the minor axis of the large-scale stellar distribution gives a fundamental insight into the structure of elliptical galaxies, for example, whether or not the nuclear kinematics are decoupled form the rest of the galaxy. Our results imply that the galaxies are oblate spheroids with their radio emission aligned with the minor axis. Remarkably the strength of the correlation of the radio major axis with the optical minor axis depends on radio loudness. Those objects with a low ratio of FIRST radio flux density to total stellar light show a strong minor axis correlation while the stronger radio sources do not. This may reflect different formation histories for the different objects and we suggest we may be seeing the different behaviour of rationally supported and non-rotationally supported ellipticals.Comment: Version to appear in MNRA

show abstract

“…No relation was found between galaxy and jet orientation (e.g., Battistini et al 1980;Birkinshaw & Davies 1985;Sansom et al 1987) apart from a tendency to avoid large > ∼ 70…”

Section: Introductionmentioning

confidence: 99%

A dichotomy in the orientation of dust and radio jets in nearby low-power radio galaxies

Kleijn

Zeeuw

2005

A&A

View full text Add to dashboard Cite

Abstract.We examine the properties of central dust in nearby quiescent and active early-type galaxies. The active galaxies are low-power radio galaxies with Fanaroff & Riley type I or I/II radio jets. We focus on (a) the comparison of the dust distributions in the active and quiescent galaxy samples; and (b) the relation between the radio jet and dust orientations. Our main observational conclusions are: (i) in line with previous studies, the dust detection rate is higher in radio-jet galaxies than in non radio-jet galaxies; (ii) radio galaxies contain a higher fraction of regular dust "ellipses" compared to quiescent galaxies which contain more often irregular dust distributions; (iii) the morphology, size and orientation of dust ellipses and lanes in quiescent early-types and active early-types with kpc-scale radio jets is very similar; (iv) dust ellipses are aligned with the major axis of the galaxy, dust lanes do not show a preferred alignment except for large (>kpc) dust lanes which are aligned with the minor axis of the galaxy; and (v) as projected on the sky, jets do not show a preferred orientation relative to the galaxy major axis (and hence dust ellipses), but jets are preferentially perpendicular to dust lanes. We show that the dust ellipses are consistent with being nearly circular thin disks viewed at random viewing angles. The lanes are likely warped dust structures, which may be in the process of settling down to become regular disks or are being perturbed by a non-gravitational force. We use the observed dust-jet orientations to constrain the three-dimensional angle θ DJ between jet and dust. For dust-lane galaxies, the jet is approximately perpendicular to the dust structure, while for dust-ellipse galaxies there is a much wider distribution of θ DJ . We discuss two scenarios that could explain the dust/jet/galaxy orientation dichotomy. If lanes are indeed settling, then the jet orientation apparently is roughly aligned with the angular momentum of the dust before it settles. If lanes are perturbed by a jet-related force, it appears that it causes the dust to move out of its equilibrium plane in the galaxy into a plane which is perpendicular to the jet.

show abstract

The radio and optical axes of radio elliptical galaxies

Cited by 27 publications

References 0 publications

Understanding the Fanaroff–riley Radio Galaxy Classification

Understanding the Fanaroff–riley Radio Galaxy Classification

Radio and optical orientations of galaxies

A dichotomy in the orientation of dust and radio jets in nearby low-power radio galaxies

Contact Info

Product

Resources

About