scholarly journals The Stripe 82 1–2 GHz Very Large Array Snapshot Survey: host galaxy properties and accretion rates of radio galaxies

2018 ◽  
Vol 480 (1) ◽  
pp. 358-370 ◽  
Author(s):  
I H Whittam ◽  
M Prescott ◽  
K McAlpine ◽  
M J Jarvis ◽  
I Heywood
Keyword(s):  
Radio Galaxies ◽  
Host Galaxy ◽  
Large Array ◽  
Very Large Array ◽  
Accretion Rates

Constraints on extragalactic-jet characteristics from lobe observations

1986 ◽  
Vol 64 (4) ◽  
pp. 378-380 ◽  
Author(s):  
Steven R. Spangler
Keyword(s):  
Hot Spot ◽  
Radio Galaxies ◽  
Large Array ◽  
Very Large Array ◽  
Upper Limits ◽  
Measured Speed ◽  
High Mach ◽  
Jet Characteristics ◽  
Double Radio Galaxies ◽  
Spot Motion

We discuss Very Large Array spectral and polarimetric observations of the lobes of luminous, double radio galaxies. These observations can provide information on the (typically undetected) jets responsible for the sources. Spectral steepening is usually observed in the lobes, with the radio spectral index increasing with distance from the hot spot. These data can be used to infer a "speed of separation" of the hot spot and lobe material. These speeds, typically 1.0 × 104–3.0 × 104 km/s, are in agreement with hydrocode models of jets, which interpret the measured speed of separation as a combination of hot-spot motion and backflow. Polarimetric observations indicate that in at least some sources, there is an undetectably small amount of internal Faraday rotation, indicating upper limits to the thermal-plasma density of a few times 10−5 cm−3 or less. These measurements are also in agreement with the numerical beam models, provided that the beam density is substantially less than that of the background medium. We conclude that the lobe observations indicate that these sources are powered by light, high-Mach-number beams.

scholarly journals WATCAT: a tale of wide-angle tailed radio galaxies

2019 ◽  
Vol 626 ◽  
pp. A8 ◽  
Author(s):  
V. Missaglia ◽  
F. Massaro ◽  
A. Capetti ◽  
M. Paolillo ◽  
R. P. Kraft ◽  
...  
Keyword(s):  
Radio Galaxies ◽  
Sloan Digital Sky Survey ◽  
Host Galaxy ◽  
Wide Angle ◽  
Host Galaxies ◽  
Very Large Array ◽  
Sky Survey ◽  
Black Hole Masses ◽  
Extended Emission ◽  
Radio Power

We present a catalog of 47 wide-angle tailed radio galaxies (WATs), the WATCAT, mainly built including a radio morphological classification; WATs were selected by combining observations from the National Radio Astronomy Observatory/Very Large Array Sky Survey (NVSS), the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST), and the Sloan Digital Sky Survey (SDSS). We included in the catalog only radio sources showing two-sided jets with two clear “warmspots” (i.e., jet knots as bright as 20% of the nucleus) lying on the opposite side of the radio core, and having classical extended emission resembling a plume beyond them. The catalog is limited to redshifts z ≤ 0.15, and lists only sources with radio emission extended beyond 30 kpc from the host galaxy. We found that host galaxies of WATCAT sources are all luminous (−20.5 ≳ Mr ≳ −23.7), red early-type galaxies with black hole masses in the range 108 ≲ MBH ≲ 109 M⊙. The spectroscopic classification indicates that they are all low-excitation galaxies (LEGs). Comparing WAT multifrequency properties with those of FR I and FR II radio galaxies at the same redshifts, we conclude that WATs show multifrequency properties remarkably similar to FR I radio galaxies, having radio power of typical FR IIs.

scholarly journals The radio properties of high-excitation radio galaxies with intermediate radio powers

2020 ◽  
Vol 494 (2) ◽  
pp. 2053-2067
Author(s):  
J C S Pierce ◽  
C N Tadhunter ◽  
R Morganti
Keyword(s):  
High Resolution ◽  
Large Scale ◽  
High Sensitivity ◽  
Seyfert Galaxies ◽  
Radio Galaxies ◽  
Host Galaxy ◽  
High Excitation ◽  
Power Sources ◽  
Very Large Array ◽  
Extended Radio

ABSTRACT In the past decade, high-sensitivity radio surveys have revealed that the local radio active galactic nucleus population is dominated by moderate-to-low power sources with emission that is compact on galaxy scales. High-excitation radio galaxies (HERGs) with intermediate radio powers (22.5 < log (L1.4 GHz) < 25.0 W Hz−1) form an important sub-group of this population, since there is strong evidence that they also drive multiphase outflows on the scales of galaxy bulges. Here, we present high-resolution Very Large Array observations at 1.5, 4.5, and 7.5 GHz of a sample of 16 such HERGs in the local universe (z < 0.1), conducted in order to investigate the morphology, extent, and spectra of their radio emission in detail, down to sub-kpc scales. We find that the majority (56 per cent) have unresolved structures at the limiting angular resolution of the observations (∼0.3 arcsec). Although similar in the compactness of their radio structures, these sources have steep radio spectra and host galaxy properties that distinguish them from local low-excitation radio galaxies that are unresolved on similar scales. The remaining sources exhibit extended radio structures with projected diameters ∼1.4–19.0 kpc and a variety of morphologies: three double-lobed; two large-scale diffuse; one jetted and ‘S-shaped’; one undetermined. Only 19 per cent of the sample therefore exhibit the double-lobed/edge-brightened structures often associated with their counterparts at high and low radio powers: radio-powerful HERGs and Seyfert galaxies, respectively. Additional high-resolution observations are required to investigate this further, and to probe the ≲300 pc scales on which some Seyfert galaxies show extended structures.

scholarly journals A Distant Fast Radio Burst Associated with Its Host Galaxy by the Very Large Array

2020 ◽  
Vol 899 (2) ◽  
pp. 161 ◽  
Author(s):  
Casey J. Law ◽  
Bryan J. Butler ◽  
J. Xavier Prochaska ◽  
Barak Zackay ◽  
Sarah Burke-Spolaor ◽  
...  
Keyword(s):  
Radio Burst ◽  
Host Galaxy ◽  
Large Array ◽  
Very Large Array ◽  
Fast Radio Burst

scholarly journals Optical Morphologies of Millijansky Radio Galaxies Observed by theHubble Space Telescopeand in the Very Large Array FIRST Survey

2008 ◽  
Vol 179 (2) ◽  
pp. 306-318 ◽  
Author(s):  
J. Russell ◽  
R. E. Ryan, Jr. ◽  
S. H. Cohen ◽  
R. A. Windhorst ◽  
I. Waddington
Keyword(s):  
Radio Galaxies ◽  
Large Array ◽  
Very Large Array

scholarly journals Unveiling the nature of the unidentified gamma-ray sources: blazar counterparts at low radio frequencies

2013 ◽  
Vol 9 (S304) ◽  
pp. 95-95
Author(s):  
Francesco Massaro ◽  
R. D'Abrusco ◽  
M. Giroletti ◽  
A. Paggi ◽  
N. Masetti ◽  
...  
Keyword(s):  
Radio Emission ◽  
Gamma Ray ◽  
Low Frequency ◽  
Radio Galaxies ◽  
Large Array ◽  
New Approach ◽  
Very Large Array ◽  
Very Low Frequency ◽  
Sky Survey ◽  
Order Of Magnitude

AbstractAbout one third of the gamma-ray sources detected by Fermi have still no firmly established counterpart at lower energies. Here we propose a new approach to find candidate counterparts for the unidentified gamma-ray sources (UGSs) based on the 325 MHz radio survey performed with Westerbork Synthesis Radio Telescope (WSRT) in the northern hemisphere. First we investigate the low-frequency radio properties of blazars, the largest known population of gamma-ray sources; then we search for sources with similar radio properties combining the information derived from the Westerbork Northern Sky Survey (WENSS) with those of the NRAO VLA Sky survey (NVSS). We present a list of candidate counterparts for 32 UGSs with at least one counterpart in the WENSS. We also performed an extensive research in literature to look for infrared and optical counterparts of the gamma-ray blazar candidates selected with the low-frequency radio observations to confirm their nature. On the basis of our multifrequency research we identify 23 new gamma-ray blazar candidates out of 32 UGSs investigated. I will also present the first analysis of very low frequency radio emission of blazars based on the recent Very Large Array Low-Frequency Sky Survey (VLSS) at 74 MHz. I show that blazars present radio flat spectra when evaluated at 74 MHz, about an order of magnitude in frequency lower than previous analyses. The implications of these findings in the contest of the blazars – radio galaxies connection will be discussed.

scholarly journals The faint radio source population at 15.7 GHz – IV. The dominance of core emission in faint radio galaxies

2020 ◽  
Vol 493 (2) ◽  
pp. 2841-2853
Author(s):  
I H Whittam ◽  
D A Green ◽  
M J Jarvis ◽  
J M Riley
Keyword(s):  
High Frequency ◽  
Angular Size ◽  
Radio Galaxies ◽  
Mixed Population ◽  
Source Population ◽  
Large Array ◽  
High Excitation ◽  
Complete Sample ◽  
Very Large Array ◽  
Upper Limit

ABSTRACT We present 15-GHz Karl G. Jansky Very Large Array observations of a complete sample of radio galaxies selected at 15.7 GHz from the Tenth Cambridge (10C) survey. 67 out of the 95 sources (71 per cent) are unresolved in the new observations and lower frequency radio observations, placing an upper limit on their angular size of ∼2 arcsec. Thus, compact radio galaxies, or radio galaxies with very faint jets, are the dominant population in the 10C survey. This provides support for the suggestion in our previous work that low-luminosity ($L\lt 10^{25} \, \textrm{W~Hz}^{-1}$) radio galaxies are core dominated, although higher resolution observations are required to confirm this directly. The 10C sample of compact, high-frequency selected radio galaxies is a mixture of high-excitation and low-excitation radio galaxies and displays a range of radio spectral shapes, demonstrating that they are a mixed population of objects.

Very Large Array imaging of five Fanaroff-Riley II 3CR radio galaxies

1993 ◽  
Vol 105 ◽  
pp. 1690 ◽  
Author(s):  
Ilias Fernini ◽  
Jack O. Burns ◽  
Alan H. Bridle ◽  
Rick A. Perley
Keyword(s):  
Radio Galaxies ◽  
Large Array ◽  
Very Large Array ◽  
Array Imaging

scholarly journals Unveiling the cause of hybrid morphology radio sources (HyMoRS)

2019 ◽  
Vol 491 (1) ◽  
pp. 803-822 ◽  
Author(s):  
Jeremy J Harwood ◽  
Tessa Vernstrom ◽  
Andra Stroe
Keyword(s):  
Radio Galaxies ◽  
Core Region ◽  
Line Of Sight ◽  
Radio Sources ◽  
Large Array ◽  
Very Large Array ◽  
Array Configuration ◽  
The Core ◽  
Vlbi Observations ◽  
Rare Group

ABSTRACT Hybrid morphology radio sources (HyMoRS) are a rare group of radio galaxies in which differing Fanaroff & Riley morphologies (FR I/II) are observed for each of the two lobes. While they potentially provide insights into the formation of lobe structure, particle acceleration, and the FR dichotomy, previous work on HyMoRS has mainly been limited to low-resolution studies, searches for new candidates, and milliarcsecond-scale VLBI observations of the core region. In this paper, we use new multi-array configuration Very Large Array (VLA) observations between 1 and 8 GHz to determine the morphology of HyMoRS on arcsecond scales and perform the first well-resolved spectral study of these unusual sources. We find that while the apparent FR I lobe is centre brightened, this is the result of a compact acceleration region resembling a hotspot with a spectrum more consistent with an FR II (‘strong-flavour’) jet. We find that the spectra of the apparent FR I lobes are not similar to their classical counterparts and are likely the result of line-of-sight mixing of plasma across a range of spectral ages. We consider possible mechanisms that could lead to the formation of HyMoRS under such conditions, including environment asymmetry and restarted sources, concluding through the use of simple modelling that HyMoRS are the result of orientation effects on intrinsically FR II sources with lobes non-parallel to the inner jet.

Multiwavelength analysis of OH Megamaser galaxies: The case of IRAS11506-3851

2020 ◽  
Vol 15 (S359) ◽  
pp. 347-349
Author(s):  
Carpes P. Hekatelyne ◽  
Thaisa Storchi-Bergmann
Keyword(s):  
Active Galactic Nuclei ◽  
Hubble Space Telescope ◽  
Galactic Nuclei ◽  
Large Array ◽  
Very Large Array ◽  
Star Forming ◽  
Star Forming Regions ◽  
Field Unit ◽  
Mixed Transition ◽  
Integral Field

AbstractWe present Multi-Object Spectrograph (GMOS) Integral Field Unit (IFU), Hubble Space Telescope (HST) and Very Large Array (VLA) observations of the inner kpc of the OH Megamaser galaxy IRAS 11506-3851. In this work we discuss the kinematics and excitation of the gas as well as its radio emission. The HST images reveal an isolated spiral galaxy and the combination with the GMOS-IFU flux distributions allowed us to identify a partial ring of star-forming regions surrounding the nucleus with a radius of ≍500 pc. The emission-line ratios and excitation map reveal that the region inside the ring present mixed/transition excitation between those of Starbursts and Active Galactic Nuclei (AGN), while regions along the ring are excited by Starbursts. We suggest that we are probing a buried or fading AGN that could be both exciting the gas and originating an outflow.

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