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.

Quasar host galaxies and environments in the GAMA survey

2019 ◽  
Vol 15 (S356) ◽  
pp. 170-170
Author(s):  
Jari Kotilainen
Keyword(s):  
Galaxy Evolution ◽  
Large Scale ◽  
Group Membership ◽  
Host Galaxy ◽  
Host Galaxies ◽  
Cluster Group ◽  
First Results ◽  
Triggering Mechanisms ◽  
Mass Assembly

AbstractWe present first results from our study of the host galaxies and environments of quasars in Galaxy And Mass Assembly (GAMA), a multiwavelength photometric and spectroscopic survey for ∼300,000 galaxies over ∼300 deg2, to a limiting magnitude of r ∼ 20 mag. We use a GAIA-selected sample of ∼350 quasars at z < 0.3 in GAMA. For all the quasars, we determine all surrounding GAMA galaxies and measure their star formation (SF) rate and SF history, and the host galaxy morphology and group membership of the quasars. As a comparison sample of inactive galaxies, we use 1000 subsets of galaxies in GAMA, matched in redshift and galaxy stellar mass to the quasars. We find that quasar activity does not depend on the large-scale environment (cluster/group/void), although quasars tend to prefer satellite location in their environment. Compared to inactive galaxies, quasars are preferentially hosted in bulge-dominated galaxies and have higher SF rates, both overall and averaged over the last 10 and 100 Myr. Quasars also have shorter median SF timescales, shorter median time since the last SF burst, and higher metallicity than inactive galaxies. We discuss these results in terms of triggering mechanisms of the quasar activity and the role of quasars in galaxy evolution.

scholarly journals Different Types of Radio Sources and Possible Evolution of Radio Galaxies

2002 ◽  
Vol 184 ◽  
pp. 301-303
Author(s):  
Gabriel A. Ohanian
Keyword(s):  
Radio Source ◽  
Large Scale ◽  
Large Range ◽  
Host Galaxy ◽  
Radio Sources ◽  
Powerful Radio ◽  
Host Galaxies ◽  
Radio Structure ◽  
Different Types ◽  
The Universe

Extragalactic radio sources have been studied for many years, but it is still unclear how they are formed and evolve. The sizes of the most powerful radio emitters in the Universe vary from less than one parsec to more than 1 Mpc. This large range of sizes has been interpreted as evidence for the evolution of the linear sizes of radio structure (e.g., O’Dea and Baum, 1997). A crucial element in the study of their evolution is the identification of the young compact counterparts of “old” FRI/FRII extended objects. Good candidates for young radio sources are those with peaked spectra (Gigahertz Peaked Spectrum - GPS and Compact Steep Spectrum - CSS, e.g., O’Dea 1998). Radio sources are presumably born in the very compact GPS phase, then they expand beyond 1 kpc into the CSS regime and finally, they reach a size of 20 kpc, and afterwards evolve into large-scale radio sources (young scenario, e.g., O’Dea 1998). Alternatively, GPS sources may be compact because a particularly dense environment prevents them from growing larger (old scenario, e.g., O’Dea 1998). In either scenario, the radio source host galaxy determines the time evolution of the radio structure. By studying the optical environments and host galaxies we hope to obtain clues to the evolution of the radio sources. Similarities or differences in host galaxy properties over a range of radio source types and sizes enable us to investigate possible differences or similarities of the radio size class as a whole.

scholarly journals The role of scatter and satellites in shaping the large-scale clustering of X-ray AGN as a function of host galaxy stellar mass

2021 ◽  
Author(s):  
A Viitanen ◽  
V Allevato ◽  
A Finoguenov ◽  
F Shankar ◽  
C Marsden
Keyword(s):  
Large Scale ◽  
Theoretical Models ◽  
Stellar Mass ◽  
Current Data ◽  
Host Galaxy ◽  
Host Galaxies ◽  
Mass Scaling ◽  
Clustering Data ◽  
Semi Empirical

Abstract The co-evolution between central supermassive black holes (BH), their host galaxies, and dark matter haloes is still a matter of intense debate. Present theoretical models suffer from large uncertainties and degeneracies, for example, between the fraction of accreting sources and their characteristic accretion rate. In recent work we showed that Active Galactic Nuclei (AGN) clustering represents a powerful tool to break degeneracies when analysed in terms of mean BH mass, and that AGN bias at fixed stellar mass is largely independent of most of the input parameters, such as the AGN duty cycle and the mean scaling between BH mass and host galaxy stellar mass. In this paper we take advantage of our improved semi-empirical methodology and recent clustering data derived from large AGN samples at z ∼ 1.2, demonstrate that the AGN bias as a function of host galaxy stellar mass is a crucial diagnostic of the BH–galaxy connection, and is highly dependent on the scatter around the BH mass–galaxy mass scaling relation and on the relative fraction of satellite and central active BHs. Current data at z ∼ 1.2 favour relatively high values of AGN in satellites, pointing to a major role of disc instabilities in triggering AGN, unless a high minimum host halo mass is assumed. The data are not decisive on the magnitude/covariance of the BH-galaxy scatter at z ∼ 1.2 and intermediate host masses M⊙ ≲ 1011 M⊙. However, future surveys like Euclid/LSST will be pivotal in shedding light on the BH–galaxy co-evolution.

scholarly journals Fast Radio Bursts: An Extragalactic Enigma

2019 ◽  
Vol 57 (1) ◽  
pp. 417-465 ◽  
Author(s):  
James M. Cordes ◽  
Shami Chatterjee
Keyword(s):  
Radiation Energy ◽  
Compact Objects ◽  
Host Galaxy ◽  
Dispersion Measure ◽  
Radio Bursts ◽  
Host Galaxies ◽  
Alternative Source ◽  
Propagation Effects ◽  
Source Models

We summarize our understanding of millisecond radio bursts from an extragalactic population of sources. Fast radio bursts (FRBs) occur at an extraordinary rate, thousands per day over the entire sky with radiation energy densities at the source about ten billion times larger than those from Galactic pulsars. We survey FRB phenomenology, source models and host galaxies, coherent radiation models, and the role of plasma propagation effects in burst detection. The FRB field is guaranteed to be exciting: New telescopes will expand the sample from the current ∼80 unique burst sources (and only a few secure localizations and redshifts) to thousands, with burst localizations that enable host-galaxy redshifts emerging directly from interferometric surveys. ▪ FRBs are now established as an extragalactic phenomenon. ▪ Only a few sources are known to repeat. Despite the failure to redetect other FRBs, they are not inconsistent with all being repeaters. ▪ FRB sources may be new, exotic kinds of objects or known types in extreme circumstances. Many inventive models exist, ranging from alien spacecraft to cosmic strings, but those concerning compact objects and supermassive black holes have gained the most attention. A rapidly rotating magnetar is a promising explanation for FRB 121102 along with the persistent source associated with it, but alternative source models are not ruled out for it or other FRBs. ▪ FRBs are powerful tracers of circumsource environments, “missing baryons” in the intergalactic medium (IGM), and dark matter. ▪ The relative contributions of host galaxies and the IGM to propagation effects have yet to be disentangled, so dispersion measure distances have large uncertainties.

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 Impact of the Early Stages of Radio Source Evolution on the ISM of the Host Galaxies

2003 ◽  
Vol 20 (1) ◽  
pp. 129-133 ◽  
Author(s):  
R. Morganti ◽  
C. N. Tadhunter ◽  
T. A. Oosterloo ◽  
J. Holt ◽  
A. Tzioumis ◽  
...  
Keyword(s):  
Radio Source ◽  
Radio Galaxy ◽  
Optical Emission ◽  
The Other ◽  
Emission Lines ◽  
Radio Sources ◽  
Host Galaxies ◽  
Cygnus A ◽  
Intermediate Size ◽  
The Impact

AbstractThe study of both neutral and ionised gas in young radio sources is providing key information on the effect the radio plasma has on the ISM of these objects. We present results obtained for the compact radio sources PKS 1549–79, 4C 12.50 and PKS 1814–63 and for the intermediate-size radio galaxy 3C 459. At least in the first two, low ionisation optical emission lines and HI absorption appear to be associated with the extended, but relatively quiescent, dusty cocoon surrounding the nucleus. The [OIII] lines are, on the other hand, mostly associated with the region of interaction between the radio plasma and the ISM, indicating a fast outflow from the centre. A case of fast outflow (up to ∼1000 km s-1) is also observed in HI in the radio source 4C 12.50. As the radio source evolves, any obscuring material along the radio axis is swept aside until, eventually, cavities (of the same kind as observed e.g. in Cygnus A) are hollowed out on either side of the nucleus. We may witness this phase in the evolution of a radio source in the radio galaxy 3C 459.

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 Weathering the Largest Storms in the Universe: Understanding environmental effects on extended radio emission in clusters

2021 ◽  
Author(s):  
◽  
Siamak Dehghan
Keyword(s):  
Structure Analysis ◽  
Large Scale ◽  
Radio Galaxy ◽  
Radio Galaxies ◽  
Radio Sources ◽  
Radio Luminosity ◽  
Star Forming ◽  
Extended Radio ◽  
The Universe

<p>This thesis presents an investigation of the habitat of extended radio sources, and the way in which the generation and properties of these radio sources are affected by environmental factors. We begin with a detailed structure analysis of the 0.3 deg² area of the MUSYC-ACES field, generated by applying a density-based clustering method, known as DBSCAN, to our spectroscopic and photometric samples of the field. As a result, we identify 62 over-dense regions across the field. Based on the properties of the detected structures, we classify 13 as clusters, of which 90% are associated with diffuse soft-band X-ray emission. This provides a strong and independent confirmation that both the clustering and classification methodologies are reliable for use in investigation of the environment of the radio sources in the Chandra Deep Field South (CDFS).  Using an interpolation-based method followed by a new calibration technique of using clusters of similar mass as standard candles, we are able to estimate the local environmental richness for a desired region. This methodology is applied to a sample of AGNs and star forming galaxies in the CDFS to probe whether or not the radio luminosity of the different radio sources is correlated to their environments. As a result, we do not find a significant correlation between the radio luminosity and the environment of star-forming galaxies and radio-quiet AGNs, however, a weak positive dependency is spotted for radio-loud AGNs. This may indicate that over-populated environments trigger or enhance the radio activity processes in the AGNs. We find that star-forming galaxies, unlike radio-loud AGNs, tend to avoid overpopulated environments especially at low redshifts. However, radio-loud AGN are found in both poor and rich environments. As a result, we find neither of these radio sources suitable for tracing the over-dense regions of the Universe, unlike tailed radio galaxies.  It is believed that tailed radio galaxies reside in the dense environments of clusters and groups, and therefore, may be the signatures of overdensities in large-scale structure. To evaluate the idea of using tailed radio galaxies as tracers of dense environments, a systematic study of these sources as a function of density is required. For this reason and by using the 1.4 GHz Australia Telescope Large Area Survey (ATLAS) data, we examined over four deg² area of the ATLAS-CDFS field, which includes the entire CDFS. We present a catalogue of 56 non-linear, extended, and low surface brightness sources including 45 tailed radio galaxies, two relic candidates, and a possible radio halo. We report the detection of the most distant tailed radio galaxy to date, at a redshift of 2.1688. In addition, despite the lack of deep spectroscopic data in the ATLAS field, we find two of the detected tailed radio galaxies are associated with clusters. We find three Head-Tail galaxy candidates in the CDFS field, all of which are located at high redshifts, where the magnitude constraint of our redshift sample prevents any structure detection.  One of the primary objectives of this research is to investigate the association between the morphology of tailed radio galaxies and the physical characteristics of the surrounding environment. In order to understand the role of the variety of factors that influence the radio morphology, we constructed a simple model that generates the overall radio structure of the sources in different habitats. We report the results of the simulation of the wide-angle tail radio galaxy PKS J0334-3900, which shows that both the gravitation interactions and a cluster wind are required to generate the observed radio tails. As a result, we find the morphology of the tailed radio galaxies as an invaluable tool to probe environmental characteristics.  In a supplementary study, we investigate the role of cluster dynamics on generation and alternation of extended radio sources. We present a comprehensive structure and sub-structure analysis of the Abell 3266 galaxy cluster. Based on the results of the sub-structure test, position and orientation of a radio relic candidate, and morphology of a prominent tailed radio galaxy in the cluster, we propose an ongoing merger scenario for this chaotic cluster environment. Furthermore, we verify our theory by an N-body simulation of a pre-merger cluster and an in-falling group. The results of the simulation supports our merger scenario by explaining both the orientation of the radio relic and the observed morphology of the tailed radio galaxy.  While there is a weak correlation between the luminosity of radio-loud AGNs and environmental density, tailed radio galaxies make superior probes of over-dense regions. Thus, overall we find tailed radio galaxies can be used to trace overdensities out to z ~ 2 and probe the details of the environments in which they are found.</p>

scholarly journals Molecular gas in the central region of NGC 7213

2020 ◽  
Vol 641 ◽  
pp. A151
Author(s):  
F. Salvestrini ◽  
C. Gruppioni ◽  
F. Pozzi ◽  
C. Vignali ◽  
A. Giannetti ◽  
...  
Keyword(s):  
Star Formation ◽  
Emission Line ◽  
Large Scale ◽  
Host Galaxy ◽  
Molecular Gas ◽  
X Ray ◽  
Gas Kinematics ◽  
Star Formation Activity ◽  
Multi Wavelength

We present a multi-wavelength study (from X-ray to mm) of the nearby low-luminosity active galactic nucleus NGC 7213. We combine the information from the different bands to characterise the source in terms of contribution from the AGN and the host-galaxy interstellar medium. This approach allows us to provide a coherent picture of the role of the AGN and its impact, if any, on the star formation and molecular gas properties of the host galaxy. We focused our study on archival ALMA Cycle 1 observations, where the CO(2–1) emission line has been used as a tracer of the molecular gas. Using the 3DBAROLO code on ALMA data, we performed the modelling of the molecular gas kinematics traced by the CO(2–1) emission, finding a rotationally dominated pattern. The molecular gas mass of the host galaxy was estimated from the integrated CO(2–1) emission line obtained with APEX data, assuming an αCO conversion factor. Had we used the ALMA data, we would have underestimated the gas masses by a factor ∼3, given the filtering out of the large-scale emission in interferometric observations. We also performed a complete X-ray spectral analysis on archival observations, revealing a relatively faint and unobscured AGN. The AGN proved to be too faint to significantly affect the properties of the host galaxy, such as star formation activity and molecular gas kinematics and distribution.

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
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