scholarly journals The Photometric and Spectroscopic Properties of Remnant and Restarted Radio Galaxies in the Lockman Hole Field

Galaxies ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 122
Author(s):  
Nika Jurlin ◽  
Raffaella Morganti ◽  
Natasha Maddox ◽  
Marisa Brienza
Keyword(s):  
Life Cycle ◽  
Low Frequency ◽  
Optical Emission ◽  
Spectroscopic Properties ◽  
Radio Galaxies ◽  
Host Galaxy ◽  
Radio Sources ◽  
Wide Field ◽  
The Impact ◽  
Lockman Hole

Radio galaxies are known to undergo phases of activity, where the stage after the jets have switched off is referred to as the remnant phase. This state can be followed by a restarted phase when the activity reignites. Remnant and restarted radio sources are important for testing models of the evolution of radio active galactic nuclei (AGN) and for understanding the impact the recurrent jet activity has on their host galaxies. Although we now have statistical samples of radio sources in various stages of their life cycle, how this intermittent radio activity is reflected in the optical properties in this sample has not yet been addressed, and is overall a much less studied aspect in the literature. In this work, we use the Wide-field Infrared Survey Explorer and the Sloan Digital Sky Survey (SDSS) photometry, and SDSS spectra to study these properties in a sample of the remnant, candidate restarted, and active radio galaxies selected using the LOw Frequency ARray at 150 MHz in the Lockman Hole extragalactic field. Within the range of radio luminosities and stellar masses studied in this work, we find no difference between the properties of the host galaxy and of the optical emission lines for objects in different phases of their radio life cycle. The vast majority of our radio sources (either remnant, candidate restarted, or comparison sample) are associated with radiatively inefficient optical AGN and red galaxies dominated by old stellar populations. Thus, the radio and emission-line AGN activity appears to be independent and regulated by different mechanisms. This suggests that, at least for the radio luminosities of our sample, the life cycle of the radio may depend on intrinsic reasons, such as the stability of the accretion disc, more than variation in the accretion rate and fuelling of the central black hole.

scholarly journals Combining LOFAR and Apertif Data for Understanding the Life Cycle of Radio Galaxies

Galaxies ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 88
Author(s):  
Raffaella Morganti ◽  
Nika Jurlin ◽  
Tom Oosterloo ◽  
Marisa Brienza ◽  
Emanuela Orrú ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Phased Array ◽  
Low Frequency ◽  
Galactic Nuclei ◽  
Radio Galaxies ◽  
Host Galaxy ◽  
Evolutionary Stage ◽  
Spectral Indices ◽  
Feed System ◽  
Lockman Hole

Active galactic nuclei (AGN) at the centres of galaxies can cycle between periods of activity and of quiescence. Characterising the duty-cycle of AGN is crucial for understanding their impact on the evolution of the host galaxy. For radio AGN, their evolutionary stage can be identified from a combination of morphological and spectral properties. We summarise the results we have obtained in the last few years by studying radio galaxies in various crucial phases of their lives, such as remnant and restarted sources. We used morphological information derived from LOw Frequency ARray (LOFAR) images at 150 MHz, combined with resolved spectral indices maps, obtained using recently released images at 1400 MHz from the APERture Tile In Focus (Apertif) phased-array feed system installed on the Westerbork Synthesis Radio Telescope. Our study, limited so far to the Lockman Hole region, has identified radio galaxies in the dying and restarted phases. We found large varieties in their properties, relevant for understanding their evolutionary stage. We started by quantifying their occurrences, the duration of the ‘on’ (active) and ‘off’ (dying) phase, and we compared the results with models of the evolution of radio galaxies. In addition to these extreme phases, the resolved spectral index images can also reveal interesting secrets about the evolution of apparently normal radio galaxies. The spectral information can be connected with, and used to improve, the Fanaroff–Riley classification, and we present one example of this, illustrating what the combination of the LOFAR and Apertif surveys now allow us to do routinely.

scholarly journals The life cycle of radio galaxies in the LOFAR Lockman Hole field

2020 ◽  
Vol 638 ◽  
pp. A34 ◽  
Author(s):  
N. Jurlin ◽  
R. Morganti ◽  
M. Brienza ◽  
S. Mandal ◽  
N. Maddox ◽  
...  
Keyword(s):  
Life Cycle ◽  
Strong Dependence ◽  
Preliminary Investigation ◽  
Radio Galaxies ◽  
Elliptical Galaxies ◽  
Host Galaxy ◽  
Host Galaxies ◽  
Low Surface Brightness ◽  
Optical Identifications ◽  
Lockman Hole

Radio galaxies are known to go through cycles of activity, where phases of apparent quiescence can be followed by repeated activity of the central supermassive black hole. A better understanding of this cycle is crucial for ascertaining the energetic impact that the jets have on the host galaxy, but little is known about it. We used deep LOFAR images at 150 MHz of the Lockman Hole extragalactic field to select a sample of 158 radio sources with sizes > 60″ in different phases of their jet life cycle. Using a variety of criteria (e.g. core prominence combined with low-surface brightness of the extended emission and steep spectrum of the central region) we selected a subsample of candidate restarted radio galaxies representing between 13% and 15% of the 158 sources of the main sample. We compare their properties to the rest of the sample, which consists of remnant candidates and active radio galaxies. Optical identifications and characterisations of the host galaxies indicate similar properties for candidate restarted, remnant, and active radio galaxies, suggesting that they all come from the same parent population. The fraction of restarted radio galaxies is slightly higher with respect to remnants, suggesting that the restarted phase can often follow after a relatively short remnant phase (the duration of the remnant phase being a few times 107 years). This confirms that the remnant and restarted phases are integral parts of the life cycle of massive elliptical galaxies. A preliminary investigation does not suggest a strong dependence of this cycle on the environment surrounding any given galaxy.

scholarly journals The XXL Survey

2018 ◽  
Vol 620 ◽  
pp. A16 ◽  
Author(s):  
Andrew Butler ◽  
Minh Huynh ◽  
Ivan Delvecchio ◽  
Anna Kapińska ◽  
Paolo Ciliegi ◽  
...  
Keyword(s):  
Star Formation ◽  
Spectral Energy Distribution ◽  
Optical Emission ◽  
Radio Galaxies ◽  
Host Galaxy ◽  
Spectral Energy ◽  
Radio Sources ◽  
Source Population ◽  
Host Galaxies ◽  
X Ray

The classification of the host galaxies of the radio sources in the 25 deg2 ultimate XMM extragalactic survey south field (XXL-S) is presented. XXL-S was surveyed at 2.1 GHz with the Australia Telescope Compact Array (ATCA) and is thus far the largest area radio survey conducted down to rms flux densities of σ ~ 41 μJy beam−1. Of the 6287 radio sources in XXL-S, 4758 (75.7%) were cross-matched to an optical counterpart using the likelihood ratio technique. There are 1110 spectroscopic redshifts and 3648 photometric redshifts available for the counterparts, of which 99.4% exist out to z ~ 4. A number of multiwavelength diagnostics, including X-ray luminosities, mid-infrared colours, spectral energy distribution fits, radio luminosities, and optical emission lines and colours, were used to classify the sources into three types: low-excitation radio galaxies (LERGs), high-excitation radio galaxies (HERGs), and star-forming galaxies (SFGs). The final sample contains 1729 LERGs (36.3%), 1159 radio-loud HERGs (24.4%), 296 radio-quiet HERGs (6.2%), 558 SFGs (11.7%), and 1016 unclassified sources (21.4%). The XXL-S sub-mJy radio source population is composed of ~75% active galactic nuclei and ~20% SFGs down to 0.2 mJy. The host galaxy properties of the HERGs in XXL-S are independent of the HERG selection, but the XXL-S LERG and SFG selection is, due to the low spectral coverage, largely determined by the known properties of those populations. Considering this caveat, the LERGs tend to exist in the most massive galaxies with low star formation rates and redder colours, whereas the HERGs and SFGs exist in galaxies of lower mass, higher star formation rates, and bluer colours. The fraction of blue host galaxies is higher for radio-quiet HERGs than for radio-loud HERGs. LERGs and radio-loud HERGs are found at all radio luminosities, but radio-loud HERGs tend to be more radio luminous than LERGs at a given redshift. These results are consistent with the emerging picture in which LERGs exist in the most massive quiescent galaxies typically found in clusters with hot X-ray halos and HERGs are associated with ongoing star formation in their host galaxies via the accretion of cold gas.

scholarly journals Spatially resolved studies of extragalactic jets in high redshift radio galaxies

2014 ◽  
Vol 10 (S313) ◽  
pp. 231-235
Author(s):  
Leah K. Morabito ◽  
Adam Deller ◽  
J. B. R. Oonk ◽  
Huub Röttgering ◽  
George Miley
Keyword(s):  
High Redshift ◽  
Low Frequency ◽  
Radio Galaxies ◽  
Radio Sources ◽  
Spatially Resolved ◽  
Long Baseline ◽  
Early Results ◽  
Spectrum Radio ◽  
Extragalactic Jets ◽  
Frequency Survey

AbstractThe correlation between radio spectral steepness and redshift has been successfully used to find high redshift (z ⩾ 2) radio galaxies, but the origin of this relation is unknown. The ultra-steep spectra of high-z radio sources make them ideally suited for studies with the Low Band Antenna of the new Low Frequency Array, which covers 10–80 MHz and has baselines up to about 1300 km. As part of an ongoing survey, we use the longest baselines to map the low-frequency (< 70 MHz) spatial distributions along the jets of 5 bright extended steep spectrum high-z radio sources. From this, we will determine whether the spectra change over these spatially resolved sources, thereby constraining particle acceleration processes. We present early results from our low-frequency survey of ultra-steep spectrum radio galaxies. The first low frequency long baseline images of these objects are presented.

scholarly journals Spectral Index - Redshift Relation for Radio Galaxies and Quasars

1996 ◽  
Vol 175 ◽  
pp. 569-570
Author(s):  
R.D. Dagkesamanskii
Keyword(s):  
Flux Density ◽  
Spectral Index ◽  
Low Frequency ◽  
Radio Galaxies ◽  
Cosmological Evolution ◽  
Radio Sources ◽  
Spectral Indices ◽  
Extragalactic Radio Sources

Cosmological evolution of synchrotron spectra of the powerful extragalactic radio sources was studied by many authors. Some indications of such an evolution had been found firstly by analysis of ‘spectral index - flux density’ (α – S) relation for the sample of relatively strong radio sources. Later Gopal-Krishna and Steppe extended the analysis to weaker sources and found that the slope of αmed(S) curve changes dramatically at intermediate flux densities. Gopal-Krishna and Steppe pointed out that the maxima of the αmed(S) curve and of differential source counts are at almost the same flux density ranges (see, Fig. 2). It has to be noticed that the all mentioned results were obtained using the low-frequency spectral indices and on the basis of low frequency samples.

scholarly journals General Properties of Giant Radio Galaxies

1996 ◽  
Vol 175 ◽  
pp. 311-312
Author(s):  
U. Klein ◽  
K.-H. Mack ◽  
L. Saripalli
Keyword(s):  
Intergalactic Medium ◽  
Surrounding Medium ◽  
Low Frequency ◽  
Radio Galaxies ◽  
Radio Sources ◽  
Low Density ◽  
General Properties

So far, the number of so-called giant radio galaxies (GRGs) is small. We define them as radio sources with linear sizes larger than 1 Mpc (H0 = 75 km s–1 Mpc–1). On-going low-frequency surveys may come up with many more candidates for this species. Their very existence may ultimately be connected with their environment. For instance, for a source like 3C236, which exhibits a linear and undisturbed structure over some 4 Mpc, the surrounding medium must have a low density. GRGs may thus serve to probe large volumes of the most tenuous intergalactic medium (IGM), e.g. via depolarization studies.

scholarly journals Radio and optical observations of “optically quiet quasars”

1986 ◽  
Vol 119 ◽  
pp. 113-115
Author(s):  
W. D. Cotton ◽  
F. N. Owen ◽  
M. J. Mahoney
Keyword(s):  
Large Particle ◽  
Low Frequency ◽  
Optical Emission ◽  
Optical Observations ◽  
Radio Sources ◽  
Optical Counterpart ◽  
Vlbi Observations ◽  
Compact Radio Source ◽  
Weak Magnetic Fields ◽  
Sky Survey

In recent years a number of very steep spectrum, compact radio sources have been discovered (e.g. Cotton 1983, Cotton and Owen 1985, Ulvestad 1985) which have no optical counterpart to the limit of the Palomar Sky Survey. VLBI observations of a number of these have confirmed the very compact (<10 mas) nature of several of these sources. Analysis of the available data in terms of the standard synchrotron modal suggest that they contain very weak magnetic fields, large particle densities and may emit detectable infrared and optical emission by inverse Campton scattering in the compact radio source (Cotton 1983). This paper will report on an analysis including new VLBI observations, infrared and optical imaging at KPNO and low frequency radio observations at CLRO of a number of these objects.

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 Feeding and feedback in nuclei of galaxies

2020 ◽  
Vol 15 (S359) ◽  
pp. 307-311
Author(s):  
Anelise Audibert ◽  
Françoise Combes ◽  
Santiago García-Burillo ◽  
Kalliopi Dasyra
Keyword(s):  
High Resolution ◽  
Active Galactic Nuclei ◽  
Galaxy Evolution ◽  
Galactic Nuclei ◽  
Radio Galaxies ◽  
Host Galaxy ◽  
Molecular Gas ◽  
Molecular Outflows ◽  
Radio Jets ◽  
The Impact

AbstractOur aim is to explore the close environment of Active Galactic Nuclei (AGN) and its connection to the host galaxy through the morphology and dynamics of the cold gas inside the central kpc in nearby AGN. We report Atacama Large Millimeter/submillimeter Array (ALMA) observations of AGN feeding and feedback caught in action in NGC613 and NGC1808 at high resolution (few pc), part of the NUclei of GAlaxies (NUGA) project. We detected trailing spirals inside the central 100 pc, efficiently driving the molecular gas into the SMBH, and molecular outflows driven by the AGN. We present preliminary results of the impact of massive winds induced by radio jets on galaxy evolution, based on observations of radio galaxies from the ALMA Radio-source Catalogue.

scholarly journals Relationship between X-shaped radio sources and double-double radio galaxies

2006 ◽  
Vol 2 (S238) ◽  
pp. 341-342
Author(s):  
Xian Chen ◽  
Fukun Liu
Keyword(s):  
Accretion Disk ◽  
Accretion Rate ◽  
Evolutionary Relationship ◽  
Control Sample ◽  
Major Axis ◽  
Radio Galaxies ◽  
Host Galaxy ◽  
Radio Sources ◽  
Two Samples ◽  
Double Radio Galaxies

AbstractBoth the X-shaped radio galaxies and double-double radio galaxies (DDRGs) are suggested in the literature to be due to the binary-accretion disk interaction or to the coalescence of SMBBHs. These models suggest some relationship between the two types of radio sources. In this paper, we collected data from literatures for two samples of X-shaped and double-double radio galaxies together with a control sample of FRII radio galaxies and statistically investigate their properties.We find that the wings of X-shaped radio galaxies and the outer and inner lobes of DDRGs tend to be perpendicular to the major axis of the host galaxy (or dust structures), while the active lobes orient randomly. Both X-shaped and double-double radio galaxies are low luminous FRII or FRI/FRII transitional radio sources with the similar dimensionless accretion rate ṁ ∼ 0.01, which is about the transitional accretion rate given in the literature.All the statistic results can be reconciled if there is an evolutionary relationship between X-shaped and double-double radio galaxies, in the sense that X-shaped radio galaxies may be due to the interaction of active SMBBHs and accretion disk and DDRGs due to the removal of inner disk region and the coalescence of SMBBHs.

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