scholarly journals Radio Galaxy Zoo: machine learning for radio source host galaxy cross-identification

2018 ◽  
Vol 478 (4) ◽  
pp. 5547-5563 ◽  
Author(s):  
M J Alger ◽  
J K Banfield ◽  
C S Ong ◽  
L Rudnick ◽  
O I Wong ◽  
...  
Keyword(s):  
Machine Learning ◽  
Radio Source ◽  
Radio Galaxy ◽  
Host Galaxy

scholarly journals Properties of Radio Source Host Galaxies

2003 ◽  
Vol 20 (1) ◽  
pp. 6-11 ◽  
Author(s):  
Wim de Vries
Keyword(s):  
Radio Source ◽  
Large Scale ◽  
Radio Galaxy ◽  
Host Galaxy ◽  
Host Galaxies ◽  
State Of Affairs

AbstractA brief overview of the current radio source host galaxy state of affairs is given. All the evidence appears to point towards a scenario in which the young radio source expands through the host galaxy on timescales of 105–106 yr, before it ends its life as a large scale FR II radio galaxy. The place and role of the quasars in this evolutionary picture is unclear, however, and remains an issue of debate.

scholarly journals Hydrodynamical backflow in X-shaped radio galaxy PKS 2014−55

2020 ◽  
Vol 495 (1) ◽  
pp. 1271-1283 ◽  
Author(s):  
W D Cotton ◽  
K Thorat ◽  
J J Condon ◽  
B S Frank ◽  
G I G Józsa ◽  
...  
Keyword(s):  
Radio Source ◽  
Radio Galaxy ◽  
Angular Resolution ◽  
Position Angle ◽  
Host Galaxy ◽  
Field Orientation ◽  
Hot Gas ◽  
Bright Region ◽  
Projected Length ◽  
The Magnetic Field

ABSTRACT We present MeerKAT 1.28 GHz total-intensity, polarization, and spectral-index images covering the giant (projected length l ≈ 1.57 Mpc) X-shaped radio source PKS 2014−55 with an unprecedented combination of brightness sensitivity and angular resolution. They show the clear ‘double boomerang’ morphology of hydrodynamical backflows from the straight main jets deflected by the large and oblique hot-gas halo of the host galaxy PGC 064440. The magnetic field orientation in PKS 2014−55 follows the flow lines from the jets through the secondary wings. The radio source is embedded in faint ($T_\mathrm{b} \approx 0.5 \mathrm{\, K}$) cocoons having the uniform brightness temperature and sharp outer edges characteristic of subsonic expansion into the ambient intragroup medium. The position angle of the much smaller (l ∼ 25 kpc) restarted central source is within 5° of the main jets, ruling out models that invoke jet re-orientation or two independent jets. Compression and turbulence in the backflows probably produce the irregular and low polarization bright region behind the apex of each boomerang as well as several features in the flow with bright heads and dark tails.

scholarly journals The Extraordinary Radio Galaxy MRC B1221–423

2003 ◽  
Vol 20 (1) ◽  
pp. 1-5 ◽  
Author(s):  
V. Safouris ◽  
R. W. Hunstead ◽  
O. R. Prouton
Keyword(s):  
Radio Source ◽  
Radio Galaxy ◽  
Early Stage ◽  
Elliptical Galaxy ◽  
Empirical Relationship ◽  
Host Galaxy ◽  
Narrow Line ◽  
Powerful Radio ◽  
Double Structure ◽  
The Core

AbstractMRC B1221–423 is a compact steep spectrum (CSS) radio source in the core of a remarkable elliptical galaxy. We examine its environment with long-slit spectra and multicolour images. A high-resolution synthesis image shows the radio source to have a 1″.5 (5.7 kpc) double structure. We use the empirical relationship between jet kinetic power and narrow line luminosity to infer a source age of ˜105 yr. The z = 0.1706 host galaxy is clearly disturbed, with tidal features and shells providing plausible evidence for a merger with one or more close companions. This evidence leads us to conclude that B1221–423 may be the progenitor of a much larger source, caught at an early stage in its radio evolution. We speculate that it is the interaction and accompanying events which have triggered this young powerful radio source.

scholarly journals Disc galaxy resolved in H I absorption against the radio lobe of 3C 433: Case study for future surveys

2020 ◽  
Vol 643 ◽  
pp. A74
Author(s):  
Suma Murthy ◽  
Raffaella Morganti ◽  
Bjorn Emonts ◽  
Montserrat Villar-Martín ◽  
Tom Oosterloo ◽  
...  
Keyword(s):  
Star Formation ◽  
Radio Source ◽  
Radio Galaxy ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Stellar Mass ◽  
Radio Continuum ◽  
Host Galaxy ◽  
Disc Galaxy ◽  
Link Type

The neutral atomic gas content of galaxies is usually studied in the H I 21 cm emission line of hydrogen. However, as we go to higher redshifts, owing to the weak strength of the transition, we need very deep integrations to detect H I emission. The H I absorption does not suffer from this dependence on distance as long as there is a sufficiently bright radio source to provide the background continuum. However, resolved H I absorption studies of galaxies are rare. We report one such rare study of resolved H I absorption against the radio galaxy 3C 433 at z = 0.101, detected with the Very Large Array. The absorption was known from single-dish observations, but owing to the higher spatial resolution of our data, we find that the absorber is located against the southern lobe of the radio galaxy. The resolved kinematics shows that the absorber has regular kinematics with an H I mass ≲3.4 × 108 M⊙ for Tspin = 100 K. We also present deep optical continuum observations and Hα observations from the Gran Telescopio CANARIAS (GTC), which reveal that the absorber is likely to be a faint disc galaxy in the same environment as 3C 433, with a stellar mass of ∼1010 M⊙ and a star-formation rate of 0.15 M⊙ yr−1 or less. Considering its H I mass, H I column density, stellar mass, and star-formation rate, this galaxy lies well below the main sequence of star forming galaxies. Its H I mass is lower than the galaxies studied in H I emission at z ∼ 0.1. Our GTC imaging has revealed, furthermore, interesting alignments between Hα and radio synchrotron emission in the H I companion and in the host galaxy of the active galactic nucleus as well as in the circumgalactic medium in between. This suggests that the shock ionization of gas by the propagating radio source may happen across a scale spanning many tens of kpc. Overall, our work supports the potential of studying the H I content in galaxies via absorption in the case of a fortuitous alignment with an extended radio continuum source. This approach may allow us to trace galaxies with low H I masses which would otherwise be missed by deep H I emission surveys. In conjunction with the deep all-sky optical surveys, the current and forthcoming blind H I surveys with the Square Kilometre Array (SKA) pathfinder facilities will be able to detect many such systems, though they may not be able to resolve the H I absorption spatially. Phase 1 of the SKA, with its sub-arcsecond resolution and high sensitivity, will be all the more able to resolve the absorption in such systems.

scholarly journals VLBA+GBT observations of the COSMOS field and radio source counts at 1.4 GHz

2018 ◽  
Vol 616 ◽  
pp. A128 ◽  
Author(s):  
N. Herrera Ruiz ◽  
E. Middelberg ◽  
A. Deller ◽  
V. Smolčić ◽  
R. P. Norris ◽  
...  
Keyword(s):  
Radio Source ◽  
Flux Density ◽  
Lower Limit ◽  
High Sensitivity ◽  
Host Galaxy ◽  
Radio Sources ◽  
Source Population ◽  
Star Forming ◽  
Brightness Temperatures ◽  
Long Baseline

We present very long baseline interferometry (VLBI) observations of 179 radio sources in the COSMOS field with extremely high sensitivity using the Green Bank Telescope (GBT) together with the Very Long Baseline Array (VLBA) (VLBA+GBT) at 1.4 GHz, to explore the faint radio population in the flux density regime of tens of μJy. Here, the identification of active galactic nuclei (AGN) is based on the VLBI detection of the source, meaning that it is independent of X-ray or infrared properties. The milli-arcsecond resolution provided by the VLBI technique implies that the detected sources must be compact and have large brightness temperatures, and therefore they are most likely AGN (when the host galaxy is located at z ≥ 0.1). On the other hand, this technique only allows us to positively identify when a radio-active AGN is present, in other words, we cannot affirm that there is no AGN when the source is not detected. For this reason, the number of identified AGN using VLBI should be always treated as a lower limit. We present a catalogue containing the 35 radio sources detected with the VLBA+GBT, ten of which were not previously detected using only the VLBA. We have constructed the radio source counts at 1.4 GHz using the samples of the VLBA and VLBA+GBT detected sources of the COSMOS field to determine a lower limit for the AGN contribution to the faint radio source population. We found an AGN contribution of >40−75% at flux density levels between 150 μJy and 1 mJy. This flux density range is characterised by the upturn of the Euclidean-normalised radio source counts, which implies a contribution of a new population. This result supports the idea that the sub-mJy radio population is composed of a significant fraction of radio-emitting AGN, rather than solely by star-forming galaxies, in agreement with previous studies.

scholarly journals High Frequency Peakers

2003 ◽  
Vol 20 (1) ◽  
pp. 79-84 ◽  
Author(s):  
Daniele Dallacasa
Keyword(s):  
Radio Source ◽  
High Frequency ◽  
Peak Frequency ◽  
Source Size ◽  
Host Galaxy ◽  
Radio Sources ◽  
Inner Region

AbstractThere is quite a clear anticorrelation between the intrinsic peak frequency and the overall radio source size in compact steep spectrum (CSS) and gigahertz peaked spectrum (GPS) radio sources. This feature is interpreted in terms of synchrotron self-absorption (although free–free absorption may play a role as well) of the radiation emitted by a small radio source which is growing within the inner region of the host galaxy. This leads to the hypothesis that these objects are young and that the radio source is still developing/expanding within the host galaxy itself.Very young radio sources must have the peak in their radio spectra occurring above a few tens of gigahertz, and for this reason they are termed high frequency peakers (HFPs). These newly born radio sources must be very rare given that they spend very little time in this stage. Ho = 100 km s−1 Mpc−1 and qo = 0.5 are used throughout this paper.

scholarly journals Radio and X-ray Observations of the Restarted Radio Galaxy in the Galaxy Cluster CL 0838+1948

Galaxies ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 108
Author(s):  
Simona Giacintucci ◽  
Tracy Clarke ◽  
Namir E. Kassim ◽  
Wendy Peters ◽  
Emil Polisensky
Keyword(s):  
Radio Source ◽  
Survey Data ◽  
Radio Galaxy ◽  
Galaxy Cluster ◽  
Gas Emission ◽  
Low Frequencies ◽  
Nuclear Activity ◽  
X Ray ◽  
Hot Gas ◽  
The Galaxy

We present VLA Low-band Ionosphere and Transient Experiment (VLITE) 338 MHz observations of the galaxy cluster CL 0838+1948. We combine the VLITE data with Giant Metrewave Radio Telescope 610 MHz observations and survey data. The central galaxy hosts a 250 kpc source whose emission is dominated by two large lobes at low frequencies. At higher frequencies, a pair of smaller lobes (∼30 kpc) is detected within the galaxy optical envelope. The observed morphology is consistent with a restarted radio galaxy. The outer lobes have a spectral index αout=1.6, indicating that they are old, whereas the inner lobes have αinn=0.6, typical for an active source. Spectral modeling confirms that the outer emission is a dying source whose nuclear activity switched off not more than 110 Myr ago. Using archival Chandra X-ray data, we compare the radio and hot gas emission. We find that the active radio source is contained within the innermost and X-ray brightest region, possibly a galactic corona. Alternatively, it could be the remnant of a larger cool core whose outer layers have been heated by the former epoch of activity that has generated the outer lobes.

scholarly journals Co-Evolution of Brightest Cluster Galaxies and Galaxy Activity in the Host Clusters

2009 ◽  
Vol 5 (S267) ◽  
pp. 110-110
Author(s):  
Mei-Ling Huang ◽  
Lin-wen Chen
Keyword(s):  
Galaxy Clusters ◽  
Radio Galaxy ◽  
Host Galaxy ◽  
Radio Sources ◽  
Wide Angle ◽  
Cluster Galaxies ◽  
Brightest Cluster Galaxies ◽  
Radio Power

AbstractWe have identified ~500 relatively relaxed galaxy clusters at low redshift (z < 0.3) from the maxBCG catalog with double radio lobes at the center; about 200 radio counterparts of brightest cluster galaxies (BCGs) of these clusters appear to be wide-angle tailed (WAT) radio sources, indicating ongoing interaction between its host galaxy and the surrounding ICM. Our analysis suggests that the radio power of WAT is positively correlated with the optical luminosities of host BCGs, and increases with redshift; whereas the cluster ellipticity-radio galaxy fraction relation shows no obvious difference between WAT and non-WAT clusters.

The compact radio source 2021 + 614 - A peculiar narrow-line radio galaxy

1984 ◽  
Vol 279 ◽  
pp. 112 ◽  
Author(s):  
N. Bartel ◽  
I. I. Shapiro ◽  
J. P. Huchra ◽  
H. Kuhr
Keyword(s):  
Radio Source ◽  
Radio Galaxy ◽  
Narrow Line ◽  
Compact Radio Source
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