scholarly journals Weak Radio Galaxies: Narrow-Band Optical Imaging

1996 ◽  
Vol 175 ◽  
pp. 236-237
Author(s):  
René Carrillo ◽  
Irene Cruz-González
Keyword(s):  
Emission Line ◽  
Narrow Band ◽  
Radio Galaxies ◽  
Convincing Evidence ◽  
Host Galaxy ◽  
Ultraviolet Continuum ◽  
Physical Relationship ◽  
Radio Jets ◽  
Extended Radio ◽  
Extended Emission

Previous studies show that: a) radio galaxies and radio-loud quasars have emission-line gas (ELG) which is extended on scales of tenths of kiloparsecs; b) there is convincing evidence that the kinematics and excitation of the very extended emission-line gas is governed by its interaction with the outflowing radio plasma; c) the evidence for an interaction is weaker in some radio galaxies. It is argued that the ionization of the ELG may be predominantly produced by the nuclear ultraviolet continuum and the kinematics of the gas due to the gravitational potential of the host galaxy, but it is not yet known whether there is a physical relationship between the ELG and the extended radio jets.

scholarly journals Discovery of a giant and luminous Lyα+C IV+He II nebula at z = 3.326 with extreme emission line ratios

2019 ◽  
Vol 629 ◽  
pp. A23 ◽  
Author(s):  
R. Marques-Chaves ◽  
I. Pérez-Fournon ◽  
M. Villar-Martín ◽  
R. Gavazzi ◽  
D. Riechers ◽  
...  
Keyword(s):  
Emission Line ◽  
Continuum Emission ◽  
Host Galaxy ◽  
Emission Characteristic ◽  
Ionized Gas ◽  
Radio Jets ◽  
Unique Object ◽  
Total Luminosity ◽  
Gas Interactions ◽  
Extended Emission

We present the discovery of HLock01-LAB, a luminous and large Lyα nebula at z = 3.326. Medium-band imaging and long-slit spectroscopic observations with the Gran Telescopio Canarias reveal extended emission in the Lyα 1215 Å, C IV 1550 Å, and He II 1640 Å lines over ∼100 kpc, and a total luminosity LLyα = (6.4 ± 0.1)×1044 erg s−1. HLock01-LAB presents an elongated morphology aligned with two faint radio sources contained within the central ∼8 kpc of the nebula. The radio structures are consistent with faint radio jets or lobes of a central galaxy, whose spectrum shows nebular emission characteristic of a type-II active galactic nucleus (AGN). The continuum emission of the AGN at short wavelengths is however likely dominated by stellar emission of the host galaxy, for which we derive a stellar mass M* ≃ 2.3 × 1011 M⊙. Our kinematic analysis shows that the ionized gas is perturbed almost exclusively in the inner region between the radio structures, probably as a consequence of jet–gas interactions, whereas in the outer regions the ionized gas appears more quiescent. The detection of extended emission in C IV and C III] indicates that the gas within the nebula is not primordial. Feedback may have enriched the halo at at least 50 kpc from the nuclear region. Using rest-frame UV emission-line diagnostics, we find that the gas in the nebula is likely heated by the AGN. Nevertheless, at the center of the nebula we find extreme emission line ratios of Lyα/C IV ∼60 and Lyα/He II ∼80, one of the highest values measured to date, and well above the standard values of photoionization models (Lyα/He II ∼30 for case B photoionization). Our data suggest that jet-induced shocks are likely responsible for the increase of the electron temperature and, thus, the observed Lyα enhancement in the center of the nebula. This scenario is further supported by the presence of radio structures and perturbed kinematics in this region. The large Lyα luminosity in HLock01-LAB is likely due to a combination of AGN photoionization and jet-induced shocks, highlighting the diversity of sources of energy powering Lyα nebulae. Future follow-up observations of HLock01-LAB will help to reveal the finer details of the excitation conditions of the gas induced by jets and to investigate the underlying cooling and feedback processes in this unique object.

scholarly journals A Powerful Jet/Cloud Interaction in the Radio Galaxy PKS 2250-41

1996 ◽  
Vol 175 ◽  
pp. 227-229
Author(s):  
R. Morganti ◽  
C.N. Tadhunter ◽  
N. Clark ◽  
N. Killeen
Keyword(s):  
Emission Line ◽  
Strong Evidence ◽  
Radio Galaxy ◽  
High Redshift ◽  
Radio Galaxies ◽  
Radio Sources ◽  
Excitation Mechanism ◽  
Powerful Radio ◽  
Radio Jets ◽  
Extended Emission

Extended emission line regions aligned with the radio axis are a common feature of powerful radio galaxies and there is much interest in the origin of the extended gas and excitation mechanism. One model that can produce this alignment is photoionization by anisotropic nuclear continuum radiation. However, strong evidence exists, especially in high redshift radio galaxies, for powerful interactions between the relativistic radio jets and the ISM/IGM. Here we present the results of our study of the southern radio galaxy PKS 2250–41 (z = 0.308). This object is the most spectacular found in a sample of southern radio sources studied by Tadhunter et al. (1993) and it displays particularly clear evidence for such an interaction (Tadhunter et al. 1994; Dickson et al. 1995).

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 Dynamical Models of Emission-Line Gas in Radio Galaxies

1996 ◽  
Vol 175 ◽  
pp. 471-472
Author(s):  
A. M. Koekemoer ◽  
G. V. Bicknell
Keyword(s):  
Emission Line ◽  
Dynamical Evolution ◽  
Radio Galaxies ◽  
Disk Galaxy ◽  
Trace Gas ◽  
Dynamical Models ◽  
Velocity Amplitude ◽  
Wide Range ◽  
Large Velocity ◽  
Extended Emission

Extended emission-line regions (EELRs) in radio ellipticals are generally thought to trace gas acquired externally, eg. through interaction with a gas-rich disk galaxy (Athanassoula and Bosma 1985, Barnes and Hernquist 1992, Hernquist and Mihos 1995). We examine here the dynamical evolution of gas in mergers, focussing on the conditions required for collisions between streams of gas. We find that such collisions can occur over a relatively wide range of encounter geometries, producing large-velocity-amplitude kinematic signatures characteristic of those observed in EELRs. This is relevant to the formation of shocks, which can account for the ionization properties of EELRs (Koekemoer and Bicknell, this conference).

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 Excitation Mechanisms in Seyfert Galaxies

1997 ◽  
Vol 159 ◽  
pp. 392-393
Author(s):  
M.G. Allen ◽  
M.A. Dopita ◽  
Z. I. Tsvetanov
Keyword(s):  
Emission Line ◽  
Spatial Dependence ◽  
Seyfert Galaxies ◽  
Host Galaxy ◽  
Excitation Mechanism ◽  
Shock Excitation ◽  
Excitation Mechanisms ◽  
Extended Emission

The excitation mechanism of the extended emission-line regions (EELRs) in Seyfert galaxies is commonly thought to be nuclear photoionization. However, some Seyfert galaxies have EELRs with disturbed kinematics, outflows, and morphology which is indicative of interaction between radio plasma and the ISM of the host galaxy. In these cases shock excitation must also be considered (BickneU 1993).To investigate the importance of shocks and photoionization, we have taken two approaches: mapping the spatial dependence of the line ratios, and using UV line ratios which are sensitive discriminants between shocks and photoionization.

scholarly journals Extended Emission Line Gas in Radio Galaxies: PKS 0349−27

1999 ◽  
Vol 521 (1) ◽  
pp. 121-133 ◽  
Author(s):  
B. I. Grimberg ◽  
E. M. Sadler ◽  
S. M. Simkin
Keyword(s):  
Emission Line ◽  
Radio Galaxies ◽  
Extended Emission

scholarly journals Evidence for a Circumnuclear Torus in Edge-On Radio Galaxies

2001 ◽  
Vol 205 ◽  
pp. 194-195
Author(s):  
A.B. Peck ◽  
G.B. Taylor
Keyword(s):  
Strong Evidence ◽  
Atomic Structure ◽  
Radio Galaxies ◽  
The Other ◽  
Host Galaxy ◽  
Absorption Imaging ◽  
Other Hand ◽  
Extended Radio

We have used VLBI HI absorption imaging to search for evidence for a circumnuclear atomic structure in five radio galaxies. Of these, we have found that two, (PKS 2322-123 and 1946+708), are very symmetric on parsec scales and exhibit strong evidence for a circumnuclear torus, confirming the prediction of the unified scheme. The two nearby extended radio galaxies NGC 5128 and NGC 315, on the other hand, have asymmetric core-jet morphologies on parsec scales, and their HI absorption profiles appear to arise from gas in the host galaxy which is not associated with the AGN at all. This is also consistent with the unified scheme of AGN. One remaining source, NGC 3894, also has symmetric jets, but has a very complicated HI structure which changes on parsec scales. This source requires further study.

Sign in / Sign up

Export Citation Format

Share Document