A preferred orientation for large radio sources relative to their elliptical galaxies

Palimaka, J. J.; Bridle, A. H.; Fomalont, Ed; Brandie, G. W.

doi:10.1086/182995

Cited by 37 publications

(22 citation statements)

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“…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

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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.

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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

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“…Our sample exhibits an anticorrelation between radio and optical major axes, which is shown as the solid histogram in Figure 12. This controversial phenomenon has been observed early on by Palimaka et al (1979) but has not been confirmed in subsequent studies (Sansom et al 1987). Nevertheless, a K-S test yields only a 1.1% probability for the null hypothesis of uncorrelated orientations in our small sample of 11 galaxies with both available radio and optical major axes.…”

Section: Implications For Agn Feedback In Elliptical Galaxiesmentioning

confidence: 91%

The Hot Interstellar Medium of Normal Elliptical Galaxies. II. Morphological Evidence for Active Galactic Nucleus Feedback

Diehl

Statler

2008

ApJ

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We report on the discovery of a new quantitative relationship between X-ray gas morphology and radio and X-ray AGN luminosities in normal elliptical galaxies. This is the second paper in a series using data on 54 objects from the Chandra public archive and builds on the findings of Paper I, which demonstrated that hydrostatic equilibrium in elliptical galaxies holds, at best, only approximately and that the shape of the X-ray isophotes is unrelated to the shape of the gravitational potential. Instead, the gas is almost always asymmetrically disturbed. In this paper we quantify the amount of asymmetry and study its correlation with other galaxy properties. We also determine radio powers and derive X-ray AGN luminosities for our galaxy sample. We find that the amount of asymmetry in the gas is correlated with both measures of AGN activity, in the sense that the hot gas is more disturbed in galaxies with higher radio and X-ray AGN luminosities. We find no evidence that galaxy density has significant effects on gas morphology. We do, however, find evidence for a correlation between gas asymmetry and the presence of hot ambient gas, which we interpret as a signature of hydrodynamic interactions with an external ambient medium. Surprisingly, the AGNmorphology connection persists all the way down to the weakest AGN luminosities in rather X-rayYfaint galaxies. This is strong morphological evidence that supports the general importance of AGN feedback, even in normal elliptical galaxies.

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“…Fig. 3 shows that there is a preference for the radio major axis to be parallel to the optical minor axis, as Guthrie (1979) and Palimaka et al (1979) also found. This preference may be somewhat stronger for iso lated and/or more flattened galaxies.…”

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confidence: 68%

A Complete Sample of Radio Galaxies

Shaver

Danziger

Ekers

et al. 1982

Symp. - Int. Astron. Union

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We report here some preliminary results of a multi-wavelength study of a complete sample of radio galaxies. The sample is comprised of 93 radio sources from the Parkes 11 cm catalog which are identified with galaxies of 17th magnitude or brighter in the declination zone -17 to -40 . Our objective is to cross-correlate the radio, infrared, optical, and other properties of a properly defined sample of radio galaxies.By going to relatively low flux densities and using an optical mag nitude limit we are approximating a volume-limited sample and consequently have a class of objects which are more representative of radio galaxies as a whole than the 3C sample. Since the 3C radio galaxies are generally of high luminosity, many are also very distant and therefore difficult to study optically. Another common difficulty in the study of radio galaxies is that radio astronomers usually only have access to the heterogeneous optical data which happen to be published on the relevant galaxies and vice-versa. It is the objective of the present work to obtain uniform and comprehensive data at radio, infrared, and optical wavelengths of a com plete sample of relatively nearby radio galaxies.We have mapped all the galaxies in the sample using the VLA, with supplementary data for the larger sources from Molonglo, Fleurs, and Parkes. Near-infrared photometry is being done using the 3.6m telescope at La Silla, and UKIRT. Spectrophotometry of all the radio galaxies and many of their companions has been completed using telescopes at La Silla and Las Campanas, and the AAT. In addition we have UV and X-ray data for several of the galaxies. This sample contains a smaller fraction of classical double radio sources than the 3C sample; these galaxies exhibit more distorted radio structures and are of lower radio and optical luminosity. 90% of them are within z = 0.1. Radio cores, mostly of the flat-spectrum type, have been detected in 80% of the galaxies. Only 6% have obvious radio jets, although there may be some indication of possible jet structure in as many as a third of them. Half of these radio galaxies are smaller than 75 kpc, as

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A preferred orientation for large radio sources relative to their elliptical galaxies

Cited by 37 publications

References 0 publications

Understanding the Fanaroff–riley Radio Galaxy Classification

Understanding the Fanaroff–riley Radio Galaxy Classification

The Hot Interstellar Medium of Normal Elliptical Galaxies. II. Morphological Evidence for Active Galactic Nucleus Feedback

A Complete Sample of Radio Galaxies

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