Extended radio structure of BL Lac type objects

AO 0235+164 is a very compact, flat-spectrum radio source. It is identified with a BL Lac object, and has optical absorption-line systems at z = 0.524 and z = 0.852. A complex set of HI absorption lines is seen at z = 0.524 (932 MHz), and several of these lines change significantly in depth over periods of less than a year. This is the only known case of variable extragalactic absorption lines. A faint nebulosity 2 arcsec south of AO 0235 + 164 has an emission-line redshift of z = 0.52 and may be an intervening galaxy. The radio spectrum of this source (between major outbursts) is remarkably flat, with the total flux density staying between about 1 and 3 Jy over a range of at least 1000 in frequency. Such a flat spectrum would lead one to expect a complex, wavelength-dependent structure consisting of several components with different self-absorption frequencies. However, the observed radio structure of 0235+164 is about as simple as one could imagine – it is a nearly unresolved point source in VLBI experiments from 900 MHz to 22 GHz. Recent VLBI experiments at 6 and 13 cm have shown evidence for some elongation of the source in a generally NE-SW direction, but only at low contour levels (< 15% of the peak). The major portion of the flux density appears to come from a core which is unresolved in VLBI experiments over a range of ~ 25 in frequency.

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Optical Observations of Radio Jets

Highlights of Astronomy ◽

10.1017/s1539299600004585 ◽

1980 ◽

Vol 5 ◽

pp. 671-675

Author(s):

Wil van Breugel ◽

George Miley ◽

Harvey R. Butcher

Keyword(s):

Energy Transport ◽

Optical Observations ◽

Radio Sources ◽

Optical Counterpart ◽

Radio Structure ◽

The Past ◽

Radio Jets ◽

Extended Radio ◽

Considerable Body ◽

Good Agreement

Over the past several years a considerable body of evidence has accumulated, suggesting that extended radio sources are powered quasi-continuously from the nuclei of their parent galaxies. This view is supported by the recent discovery that several radio galaxies have narrow radio jets which connect their active nuclei with the large radio lobes and which often extend for several tens of kiloparsecs. Because of their presumed association with the energy transport outward from the active nuclei, radio jets are at present being intensively studied with high-resolution radio techniques.The closest galaxy known to have a radio jet is the giant elliptical M87 (e.g., Wilkinson 1974), and in this case there is a well-known optical counterpart (e.g., Curtis 1918; de Vaucouleurs, Angione and Fraser 1968), This optical jet is highly polarized (Baade 1956), implying that at least part of the emission is non-thermal. This and the good agreement between the optical and radio structure suggests that these features are closely related.

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The Extended Radio Structure of Quasars

Symposium - International Astronomical Union ◽

10.1017/s0074180900152593 ◽

1986 ◽

Vol 119 ◽

pp. 173-179 ◽

Cited By ~ 1

Author(s):

Frazer N. Owen

Keyword(s):

Energy Supply ◽

Relativistic Effects ◽

Activity Level ◽

Intrinsic Activity ◽

Radio Sources ◽

Radio Structure ◽

Extended Structure ◽

Outstanding Problem ◽

Extended Radio

Modern radio maps usually allow quasars to be recognized from their radio morphology alone. Most have strong central components, double lobed outer structure and one-sided jets connecting the inner and outer structures. The physics of the sources is poorly understood. The observed bending of the jets, the high minimum pressures observed, and the required energy supply to the lobes are major problems. However, the outstanding problem regarding the extended structure is whether or not this morphology is produced by special relativistic effects or the intrinsic activity level and physics of the radio sources.

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QSO2 outflow characterization using data obtained with OSIRIS at the Gran Telescopio Canarias

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935270 ◽

2019 ◽

Vol 626 ◽

pp. A89 ◽

Cited By ~ 1

Author(s):

Enrica Bellocchi ◽

Montserrat Villar Martín ◽

Antonio Cabrera–Lavers ◽

Bjorn Emonts

Keyword(s):

Large Scale ◽

Spatial Scales ◽

Host Galaxies ◽

Radio Structure ◽

Dynamical State ◽

Gas Kinematics ◽

Very Large Telescope ◽

Extended Radio ◽

Using Data ◽

S0 Galaxies

Context. Ionized outflows are ubiquitous in non-radio-loud obscured quasars (QSO2s) at different redshifts. However, the actual size of the outflows and their efficiency for gas ejection and star formation truncation are controversial. Large-scale (exceeding several kiloparsec) extended radio structures might be necessary to identify (even to trigger) outflow signatures across such large spatial scales. Aims. We search for large-scale ionized outflows associated with six optically selected QSO2 (five non-radio-loud and one radio-loud) at z ∼ 0.2−0.5, targeting objects with extended radio structures. We also investigate the dynamical state of the QSO2 host galaxies. Methods. We obtained data with the optical imager and long-slit spectrograph (OSIRIS) mounted on the 10.4m Gran Telescopio Canarias Spanish telescope (GTC) for these six QSO2 with the slit located along the radio axis. We traced the gas kinematics with the [OIII]λλ4959,5007 lines to investigate ionized outflows and characterize the dynamical state of the host galaxies. This second study was complemented with previously published spectroscopic data obtained with the multimode focal reducer and low dispersion spectrograph (FORS2) mounted on the Very Large Telescope (VLT) of 13 more QSO2 at similar z. Results. We identify ionized outflows in four out of the six QSO2 observed with the GTC. The outflows are spatially unresolved in two QSO2 and compact in a third (radial size of R = 0.8 ± 0.3 kpc). Of particular interest is the radio-quiet QSO2 SDSS 0741+3020 at z = 0.47. It is associated with a giant ∼112 kpc nebula. An ionized outflow probably induced by the radio structures has been detected along the axis defined by the central ∼1″ radio structure, extending up to at least ∼4 kpc from the active galactic nucleus (AGN). Turbulent gas (σ ∼ 130 km s−1) has also been detected across the giant gas nebula up to ∼40 kpc from the AGN. This turbulence may have been induced by outflows triggered by the interaction between a so-far undetected large-scale radio source and the nebula. Regarding the dynamical state of the host galaxies, we find that the majority of the QSO2 show v/σ < 1, implying that they are dominated by random motions (so-called dispersion-dominated systems). Most (17 of 19) fall in the area of the E/S0 galaxies in the dynamical diagram v/σ versus σ. None are consistent with spiral or disk galaxies.

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Extended radio emission in BL Lac objects

Astronomy and Astrophysics Supplement Series ◽

10.1051/aas:1999511 ◽

1999 ◽

Vol 139 (3) ◽

pp. 601-616 ◽

Cited By ~ 57

Author(s):

P. Cassaro ◽

C. Stanghellini ◽

M. Bondi ◽

D. Dallacasa ◽

R. Della Ceca ◽

...

Keyword(s):

Radio Emission ◽

Bl Lac Objects ◽

Extended Radio ◽

Bl Lac

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Bent It Like FRs: Extended Radio AGN in the COSMOS Field and Their Large-Scale Environment

Galaxies ◽

10.3390/galaxies9040093 ◽

2021 ◽

Vol 9 (4) ◽

pp. 93

Author(s):

Eleni Vardoulaki ◽

Franco Vazza ◽

Eric F. Jiménez-Andrade ◽

Ghassem Gozaliasl ◽

Alexis Finoguenov ◽

...

Keyword(s):

Large Scale ◽

Ambient Medium ◽

Adaptive Mesh ◽

Radio Structure ◽

X Ray ◽

Galaxy Groups ◽

Extended Radio ◽

Wide Range ◽

Jet Interactions ◽

Host Properties

A fascinating topic in radio astronomy is how to associate the complexity of observed radio structures with their environment in order to understand their interplay and the reason for the plethora of radio structures found in surveys. In this project, we explore the distortion of the radio structure of Fanaroff–Riley (FR)-type radio sources in the VLA-COSMOS Large Project at 3 GHz and relate it to their large-scale environment. We quantify the distortion by using the angle formed between the jets/lobes of two-sided FRs, namely bent angle (BA). Our sample includes 108 objects in the redshift range 0.08<z<3, which we cross-correlate to a wide range of large-scale environments (X-ray galaxy groups, density fields, and cosmic web probes) in the COSMOS field. The median BA of FRs in COSMOS at zmed∼0.9 is 167.5−37.5+11.5 degrees. We do not find significant correlations between BA and large-scale environments within COSMOS covering scales from a few kpc to several hundred Mpc, nor between BA and host properties. Finally, we compare our observational data to magnetohydrodynamical (MHD) adaptive-mesh simulations ENZO-MHD of two FR sources at z = 0.5 and at z = 1. Although the scatter in BA of the observed data is large, we see an agreement between observations and simulations in the bent angles of FRs, following a mild redshift evolution with BA. We conclude that, for a given object, the dominant mechanism affecting the radio structures of FRs could be the evolution of the ambient medium, where higher densities of the intergalactic medium at lower redshifts as probed by our study allow more space for jet interactions.

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