scholarly journals Rotating Gas and the Shapes of Radio Sources

1982 ◽  
Vol 97 ◽  
pp. 25-26
Author(s):  
L. S. Sparke
Keyword(s):  
Seyfert Galaxies ◽  
External Pressure ◽  
Opening Angle ◽  
Radio Sources ◽  
Extragalactic Radio Source ◽  
Radio Structure ◽  
Radio Jets ◽  
Extended Radio ◽  
The Galaxy ◽  
Scale Properties

The power for a strong extragalactic radio source comes from deep within the nucleus, but the extended radio structure is clearly related to the larger-scale properties of the galaxy in which it lives. Very large sources are found in elliptical rather than spiral galaxies, and big galaxies have stronger radio sources than small ones. The narrow jets mapped in weaker radio galaxies do not expand with a constant opening angle, but become better focussed along their length, suggesting that they are confined by an external pressure. This paper discusses how the rotation of a radio galaxy affects the distribution of gas within it, and consequently the radio structure in elliptical and Seyfert galaxies. A model is proposed which leads to a specific prediction, relating the width of radio jets to the rotation speed of the galaxy in which they lie.

scholarly journals Optical Observations of Radio Jets

1980 ◽  
Vol 5 ◽  
pp. 671-675
Author(s):  
Wil van Breugel ◽  
George Miley ◽  
Harvey R. Butcher
Keyword(s):  
Energy Transport ◽  
Optical Observations ◽  
Radio Sources ◽  
Optical Counterpart ◽  
Radio Structure ◽  
The Past ◽  
Radio Jets ◽  
Extended Radio ◽  
Considerable Body ◽  
Good Agreement

Over the past several years a considerable body of evidence has accumulated, suggesting that extended radio sources are powered quasi-continuously from the nuclei of their parent galaxies. This view is supported by the recent discovery that several radio galaxies have narrow radio jets which connect their active nuclei with the large radio lobes and which often extend for several tens of kiloparsecs. Because of their presumed association with the energy transport outward from the active nuclei, radio jets are at present being intensively studied with high-resolution radio techniques.The closest galaxy known to have a radio jet is the giant elliptical M87 (e.g., Wilkinson 1974), and in this case there is a well-known optical counterpart (e.g., Curtis 1918; de Vaucouleurs, Angione and Fraser 1968), This optical jet is highly polarized (Baade 1956), implying that at least part of the emission is non-thermal. This and the good agreement between the optical and radio structure suggests that these features are closely related.

scholarly journals Unified Models: Religion and Science

1994 ◽  
Vol 159 ◽  
pp. 301-309 ◽  
Author(s):  
Robert Antonucci
Keyword(s):  
Elliptical Galaxy ◽  
Opening Angle ◽  
Radio Sources ◽  
Religion And Science ◽  
Radio Structure ◽  
Radio Jets ◽  
Line Region ◽  
Superluminal Motion ◽  
Bulk Motion

The Unified Model states that the classification of individual AGN is a function of orientation, and that orientation effects are key to understanding the different classes. In its most extreme form, it states that every AGN has a featureless continuum (FC) source and a broad line region (BLR), both enclosed in an opaque torus. The torus is perpendicular to the associated radio structure axis. For the powerful radio sources (in Elliptical galaxy hosts), the jets undergo bulk relativistic motion, giving rise to phenomena such as superluminal motion associated with the blazar class. All strong radio sources have diffuse double radio lobes, although in the blazars one is sometimes seen projected onto the other. To take this to the extreme, we can suppose that all opaque tori are made of dust and have the same opening angle and that the radio jets are all narrow and have the same bulk-motion Γ factor.

scholarly journals Infrared Observations of Radio Galaxies

1982 ◽  
Vol 97 ◽  
pp. 239-246
Author(s):  
George H. Rieke
Keyword(s):  
Thermal Emission ◽  
Optical Emission ◽  
Seyfert Galaxies ◽  
Radio Sources ◽  
Extragalactic Radio Source ◽  
Extragalactic Source ◽  
Infrared Observations ◽  
Infrared Studies ◽  
Complete Identification ◽  
Ultraviolet Photons

For technical reasons, infrared studies of active galaxies have lagged far behind optical and radio ones. This is unfortunate, since entirely new aspects of these sources are often revealed in the infrared. The extreme efficiency of dust at degrading ultraviolet photons into cool thermal emission frequently makes the luminosity of an extragalactic source inaccessible to optical and radio astronomers. At the same time, the effects of dust on optical emission line ratios and continuum shapes can be profound. The complete identification of samples of radio sources will require infrared observations to supplement the optical techniques now generally employed, and the extreme properties of the sources bright in the infrared can provide new insights to conditions in extragalactic nonthermal sources. To illustrate these points, I will discuss three cases: 1.) galaxies undergoing a powerful burst of star formation, 2.) intermediate type Seyfert galaxies, and 3.) an extreme infrared identification of an extragalactic radio source.

scholarly journals The Extended Radio Structure of Quasars

1986 ◽  
Vol 119 ◽  
pp. 173-179 ◽  
Author(s):  
Frazer N. Owen
Keyword(s):  
Energy Supply ◽  
Relativistic Effects ◽  
Activity Level ◽  
Intrinsic Activity ◽  
Radio Sources ◽  
Radio Structure ◽  
Extended Structure ◽  
Outstanding Problem ◽  
Extended Radio

Modern radio maps usually allow quasars to be recognized from their radio morphology alone. Most have strong central components, double lobed outer structure and one-sided jets connecting the inner and outer structures. The physics of the sources is poorly understood. The observed bending of the jets, the high minimum pressures observed, and the required energy supply to the lobes are major problems. However, the outstanding problem regarding the extended structure is whether or not this morphology is produced by special relativistic effects or the intrinsic activity level and physics of the radio sources.

Optical spectroscopy of radio jets in 3C 31, 3C 75, 3C 83.1B, and 3C 465

1986 ◽  
Vol 64 (4) ◽  
pp. 369-372 ◽  
Author(s):  
Christopher P. O'Dea ◽  
Frazer N. Owen ◽  
William C. Keel
Keyword(s):  
Optical Spectroscopy ◽  
External Medium ◽  
Line Emission ◽  
Radio Sources ◽  
Ionized Gas ◽  
Radio Jets ◽  
Upper Limits ◽  
The Galaxy ◽  
Lower Limits ◽  
Total Velocity

We present preliminary results of optical spectroscopy of four radio galaxies with jets (3C 75, 3C 465, 3C 31, and 3C 83. 1B (NGC 1265)). We examined selected regions in and around the radio jets for evidence of the interaction of the jets with their external medium (e.g., entrainment or bending through collision with clouds). We searched for the emission lines expected from ionized gas at a temperature of T ~ 104 K (e.g., Hα and [NII]) as well as those expected at higher temperatures (T ~ 106 K, Fe X (λ6374) and Fe XIV (λ5303)).We found no extranuclear emission in the regions searched in 3C 75, 3C 465, and 3C 83.1B. Assuming values for the pressure in the environment of the radio sources, we found the upper limits to the line emission correspond to model-dependent lower limits to the temperature in the range T ≥ 1.5–3 × 106 K and upper limits to the electron density in the range ne ≤ 5 × 10−2−5 × 10−3 cm−3.In 3C 31, we detected extended Hα and [NII] emission that is peaked on the nucleus and exhibits a velocity gradient. The [NII] emission has a total velocity width of ~800 km∙s−1. It is not yet clear whether any of this emission is associated with the jet (e.g., entrained gas) or whether it is associated with a known dust lane in the galaxy NGC 383.

scholarly journals Radio Frequency Observations of the Nuclei of Galaxies

1974 ◽  
Vol 58 ◽  
pp. 257-277 ◽  
Author(s):  
R. D. Ekers
Keyword(s):  
Seyfert Galaxies ◽  
Morphological Type ◽  
Elliptical Galaxies ◽  
Infrared Emission ◽  
Radio Sources ◽  
Extended Radio ◽  
Median Diameter ◽  
Extended Sources ◽  
Highly Correlated ◽  
Ngc 1275

For spiral galaxies the nuclear radio emission is usually dominated by a complex distribution of emission with median diameter of 200 pc and median power of 1019 W Hz−1 sr−1 at 1400 MHz. There is a large range in both power and diameter. The power is independent of morphological type for the normal spirals but is correlated with the absolute optical magnitude and with the infrared emission. For Seyfert galaxies the emission is generally stronger, in some cases by several orders of magnitude (e.g. NGC 1275, 3C 120).Elliptical galaxies have been found with very compact radio sources, some less than a parsec in diameter. These are as powerful as the strongest spirals (~ 1021 W Hz−1 sr−1). Even stronger compact nuclear sources are now being found in the nuclei of those elliptical galaxies which also have extended radio sources (the radio galaxies). The presence of nuclear sources of this strength is so highly correlated with the presence of extended sources that this suggests a continuing involvement of the nucleus.

The Giant Radio Galaxy 0319-45 (MSH 03-43)

1989 ◽  
Vol 8 (1) ◽  
pp. 81-85 ◽  
Author(s):  
P. A. Jones
Keyword(s):  
Radio Galaxy ◽  
Level Structure ◽  
Radio Galaxies ◽  
Radio Sources ◽  
Low Level ◽  
Extended Radio ◽  
The Galaxy ◽  
Galaxy Redshift ◽  
Nearby Source ◽  
Extended Radio Source

AbstractThe extended radio source 0319-453 (MSH 03-43) was observed with the Molonglo Observatory Synthesis Telescope as part of a program to study a large sample of southern extragalactic radio sources. The low level structure showed a ridge pointing towards the nearby source 0317-456, which also showed low level structure. It is suggested that the two sources are the asymmetric lobes of a radio galaxy identified with the magnitude 15 peculiar dust-land galaxy AM 0319-452. The galaxy redshift of z = 0.0633 and the radio size of 25.6 arcmin give a projected size of 1.27 Mpc (H = 100 kms−1 Mpc−1). Thus it is one of the largest radio galaxies.

scholarly journals A molecular absorption line survey towards the AGN of Hydra-A

2020 ◽  
Vol 496 (1) ◽  
pp. 364-380
Author(s):  
Tom Rose ◽  
A C Edge ◽  
F Combes ◽  
S Hamer ◽  
B R McNamara ◽  
...  
Keyword(s):  
Elliptical Galaxy ◽  
Cluster Galaxy ◽  
Cluster Galaxies ◽  
Continuum Source ◽  
Radio Jets ◽  
Extended Radio ◽  
Brightest Cluster Galaxies ◽  
The Galaxy ◽  
Absorption Features ◽  
Recession Velocity

ABSTRACT We present Atacama Large Millimetre/submillimetre Array observations of the brightest cluster galaxy Hydra-A, a nearby (z = 0.054) giant elliptical galaxy with powerful and extended radio jets. The observations reveal CO(1−0), CO(2–1), 13CO(2–1), CN(2–1), SiO(5–4), HCO+(1–0), HCO+(2–1), HCN(1–0), HCN(2–1), HNC(1–0), and H2CO(3–2) absorption lines against the galaxy’s bright and compact active galactic nucleus. These absorption features are due to at least 12 individual molecular clouds that lie close to the centre of the galaxy and have velocities of approximately −50 to +10 km s−1 relative to its recession velocity, where positive values correspond to inward motion. The absorption profiles are evidence of a clumpy interstellar medium within brightest cluster galaxies composed of clouds with similar column densities, velocity dispersions, and excitation temperatures to those found at radii of several kpc in the Milky Way. We also show potential variation in a ∼10 km s−1 wide section of the absorption profile over a 2 yr time-scale, most likely caused by relativistic motions in the hot spots of the continuum source that change the background illumination of the absorbing clouds.

scholarly journals Active Galaxies and Candidate Remnants in the Core of the Shapley Concentration

2002 ◽  
Vol 199 ◽  
pp. 161-162
Author(s):  
T. Venturi ◽  
S. Bardelli ◽  
D. Dallacasa ◽  
R.W. Hunstead ◽  
R. Morganti ◽  
...  
Keyword(s):  
Spectral Properties ◽  
Radio Galaxies ◽  
Active Galaxies ◽  
Radio Sources ◽  
Nuclear Activity ◽  
The Core ◽  
Radio Jets ◽  
Extended Radio ◽  
Cluster Mergers ◽  
Compact Array

We present preliminary results of a multifrequency and multiresolution study carried out with the Australia Telescope Compact Array for nine of the ten extended radio galaxies located in the merging cluster complexes A3558 and A3528, at the centre of the Shapley Concentration. We found that 5 out of the 9 extended radio galaxies are active radio galaxies, i.e. they have a clear active radio nucleus coincident with the central region of the associated optical galaxy, radio jets and extended lobes; the remaining four lack an obvious radio nucleus, have a very diffuse and amorphous morphology and exhibit peculiar spectral properties. We call these radio sources as remnants and propose that they are (a) either radio galaxies where the nuclear activity has ceased; or (b) regions where pre-existing electrons have been reaccelerated as consequence of shocks due to cluster mergers.

scholarly journals A multiwavelength study of the dual nuclei in Mrk 212

2020 ◽  
Vol 500 (3) ◽  
pp. 3908-3919
Author(s):  
K Rubinur ◽  
P Kharb ◽  
M Das ◽  
P T Rahna ◽  
M Honey ◽  
...  
Keyword(s):  
Radio Source ◽  
Galactic Nuclei ◽  
Optical Emission ◽  
Radio Observations ◽  
Radio Structure ◽  
Very Large Array ◽  
Extended Radio ◽  
The Galaxy ◽  
Double Radio Source ◽  
Tidal Tails

ABSTRACT We present radio observations of the galaxy merger remnant Mrk 212 with the Karl G. Jansky Very Large Array (VLA) and the upgraded Giant Meter Radio Telescope (uGMRT). Mrk 212 has two previously known radio sources associated with the two optical nuclei, S1 and S2, with a projected separation of ∼6 kpc, making it a dual active galactic nuclei (AGN) candidate. Our new 15-GHz VLA observations reveal that S1 is a double radio source centred around the optical nucleus; its total extent is ∼750 pc its average 1.4−8.5 GHz spectral index is −0.81 ± 0.06. S1 therefore resembles a compact symmetric object. The 15-GHz VLA image identifies the radio source at S2 to be a compact core. Our radio observations therefore strongly support the presence of a dual AGN in Mrk 212. The optical emission line flux ratios obtained from the Himalayan Chandra Telescope (HCT) observations however, show that S1 and S2 both fall in the AGN + star formation (SF) region of the Baldwin, Philips and Terlevich (BPT) diagram. Weak AGN lying in the SF or AGN + SF intermediate regions in the BPT diagram have indeed been reported in the literature; our sources clearly fall in the same category. We find an extended radio structure in our newly reduced 8.5-GHz-VLA data, that is offset by ∼1 arcsec from the optical nucleus S2. New deep FUV and NUV observations with the Ultraviolet Imaging Telescope aboard AstroSat reveal SF knots around S2 as well as kpc-scale tidal tails; the SF knots around S2 coincide with the extended radio structure detected at 8.5 GHz. The radio spectral indices are consistent with SF. Any possible association with the AGN in S2 is unclear at this stage.

Sign in / Sign up

Export Citation Format

Share Document