FIRST "Winged" and X-Shaped Radio Source Candidates

Cheung, C. C.; Springmann, Alessondra

doi:10.1086/513095

Cited by 111 publications

(190 citation statements)

References 118 publications

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“…These objects show, in addition to the main lobes, a pair of wings that produce their peculiar radio morphology. We obtain our sample by selecting from the initial list of Cheung (2007( , AJ, 133, 2097) the 53 galaxies with the better defined wings and with available SDSS images. We identify the host galaxies and measure their optical position angle, obtaining a positive result in 22 cases.…”

Section: Introductionmentioning

confidence: 99%

Origin of X-shaped radio-sources: further insights from the properties of their host galaxies

Gillone

Capetti

Rossi

2016

A&A

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We analyze the properties of a sample of X-shaped radio-sources (XRSs). These objects show, in addition to the main lobes, a pair of wings that produce their peculiar radio morphology. We obtain our sample by selecting from the initial list of Cheung (2007( , AJ, 133, 2097) the 53 galaxies with the better defined wings and with available SDSS images. We identify the host galaxies and measure their optical position angle, obtaining a positive result in 22 cases. The orientation of the secondary radio structures shows a strong connection with the optical axis, with all (but one) wing forming an angle larger than 40 • with the host major axis. The probability that this is compatible with a uniform distribution is P = 0.9 × 10 −4 . For all but three sources of the sample, spectroscopic or photometric redshifts are avaliable. The radio luminosity distribution of XRSs has a high power cut-off at L ∼ 10 34 erg s −1 Hz −1 at 1.4 GHz. Spectra are available from the SDSS for 28 XRSs. We modeled them to extract information on their emission lines and stellar population properties. The sample is formed by approximately the same number of high and low excitation galaxies (HEGs and LEGs); this classification is essential for a proper comparison with non-winged radio-galaxies. XRSs follow the same relations between radio and line luminosity defined by radio-galaxies in the 3C sample. While in HEGs a young stellar population is often present, this is not detected in the 13 LEGs, which is, again, in agreement with the properties of non-XRSs. The lack of young stars in LEGs supports the idea that they have not experienced a recent gas-rich merger. The connection between the optical axis and the wing orientation, as well as the stellar population and emission-line properties, provide further support for a hydro-dynamic origin of the radio-wings (for example, associated with the expansion of the radio cocoon in an asymmetric external medium) rather than with a change of orientation of the jet axis. In this framework, the high luminosity limit of XRSs can be interpreted as being due to high power jets being less affected by the properties of the surrounding medium.

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Section: Introductionmentioning

confidence: 99%

Origin of X-shaped radio-sources: further insights from the properties of their host galaxies

Gillone

Capetti

Rossi

2016

A&A

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“…The observed sample comprises 13 X-shaped radio galaxies retrieved from a list of 100 candidates (Cheung 2007). We selected all the objects with bright (m R < 19), optical counterparts for which neither spectroscopic redshifts had been reported nor spectra were available in the Sloan Digital Sky Survey (SDSS), and which were observable during the period of the observations (i.e., across a range of right ascension between 07:00:00 and 17:00:00).…”

Section: Observations and Data Reductionmentioning

confidence: 99%

Starbursts and black hole masses in X-shaped radio galaxies: Signatures of a merger event?

Mezcua

Chavushyan

Lobanov

2012

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We present new spectroscopic identifications of 12 X-shaped radio galaxies and use the spectral data to derive starburst histories and masses of the nuclear supermassive black holes in these galaxies. The observations were done with the 2.1-m telescope of the Observatorio Astronómico Nacional at San Pedro Mártir, México. The new spectroscopic results extend the sample of X-shaped radio galaxies studied with optical spectroscopy. We show that the combined sample of the X-shaped radio galaxies has statistically higher black-hole masses and older episodes of star formation than a control sample of canonical double-lobed radio sources with similar redshifts and luminosities. The data reveal enhanced star-formation activity in the X-shaped sample on the timescales expected in galactic mergers. We discuss the results obtained in the framework of the merger scenario.

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“…Th ree decades ago approximately a dozen radio galaxies displaying two sets of jets emitting from the central supermassive black hole, forming a distinctive "X"-shape were known [2]. Over the past three decades, the number of known sources possessing the X-shaped morphology has grown to over a hundred candidates, allowing for more detailed studies of these objects, particularly regarding their shape and origin.…”

Section: Introductionmentioning

confidence: 99%

“…Using the ellipse package for Image Reduction and Analysis Facility (IRAF) 2 to model the elliptically-shaped isophotes, or regions of equal brightness, of the galaxies, the ellipticity and extent of the host galaxies and ___________ 1 An elliptical galaxy is an ellipsoid, or a three-dimensional ellipse, as shown in Figure 4. Viewed from Earth, it appears as an ellipse in the sky.…”

Section: Introductionmentioning

confidence: 99%

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Host Galaxies of X-Shaped Radio Sources

Springmann¹,

Coll.²

2006

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Most radiation from galaxies containing active galactic nuclei (AGNs) is emitted not by the stars composing the galaxy, but from an active source at the galactic center, most likely a supermassive black hole. Of particular interest are radio galaxies, active galaxies that emit much of their radiation at radio wavelengths. Within each radio galaxy, an AGN powers a pair of collimated jets of relativistic particles, forming a pair of giant lobes at the end of the jets and thus giving a characteristic double-lobed appearance. A particular class of radio galaxies has an "X"-or winged-shaped morphology: in these, two pairs of lobes appear to originate from the galactic center, producing a distinctive X-shape. Two main mechanisms have been proposed to explain the X-shape morphology: one being a realignment of the black hole within the AGN and the second positing that the radio jets are expanding into an asymmetric medium, causing backflow and producing secondary wings. By analyzing radio host galaxy shapes, the distribution of the stellar mass is compared to the differing model expectations regarding the distribution of the surrounding gas and stellar material about the AGN. Results show elliptical host galaxies with an orthogonal offset between the semi-major axis of the host galaxy and the secondary radio wings, which lends support to the hydrodynamical model. However, results also show circular host galaxies with radio wings, making the realignment scenario a more likely model to describe the formation of these X-shaped radio sources.

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FIRST "Winged" and X-Shaped Radio Source Candidates

Cited by 111 publications

References 118 publications

Origin of X-shaped radio-sources: further insights from the properties of their host galaxies

Origin of X-shaped radio-sources: further insights from the properties of their host galaxies

Starbursts and black hole masses in X-shaped radio galaxies: Signatures of a merger event?

Host Galaxies of X-Shaped Radio Sources

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