scholarly journals The Role of Environment in the Origin of Radio Emission from Galaxies

1987 ◽  
Vol 121 ◽  
pp. 411-414
Author(s):  
T.K. Menon
Keyword(s):  
Radio Emission ◽  
Compact Group ◽  
Radio Source ◽  
Spiral Galaxies ◽  
Compact Groups ◽  
Radio Radiation ◽  
Luminosity Functions ◽  
Group Galaxy ◽  
Absolute Luminosity

The influence of the environment on the origin of radio radiation from galaxies is studied by compairing the occurence of radio emission in galaxies in compact high density groups of Hickson (1982) with that in field galaxies of similar types. The study shows that the fractional luminosity functions of elliptical and spiral galaxies in compact groups are similar in shape to that of field galaxies but the probability of a compact group galaxy being a radio source is 5 to 10 times greater than that of an isolated galaxy of the same type. Radio Loud group ellipticals tend to be the optically brightest galaxy in the group independent of their absolute luminosity.

scholarly journals Mass Distribution in Compact Groups

2000 ◽  
Vol 174 ◽  
pp. 377-380 ◽  
Author(s):  
J. Perea ◽  
A. del Olmo ◽  
L. Verdes-Montenegro ◽  
M. S. Yun ◽  
W.K. Huchtmeier ◽  
...  
Keyword(s):  
Compact Group ◽  
Mass Distribution ◽  
Spiral Galaxies ◽  
Main Group ◽  
Stable System ◽  
Compact Groups ◽  
Dark Halo ◽  
Potential Well ◽  
Redshift Surveys ◽  
Satellite Galaxies

AbstractNew redshift surveys of galaxies in the field of compact groups have discovered a population of faint galaxies which act as satellites orbiting in the potential well of the bright group. Here we analyze the mass distribution of the groups by comparing the mass derived from the bright members and the mass obtained from the satellite galaxies. Our analysis indicates the presence of a dark halo around the main group with a mass roughly four times that measured for the dominant galaxies of the compact group.We found that heavier halos are ruled out by the observations when comparing the distribution of positions and redshifts of the satellite galaxies with the distribution of satellites of isolated spiral galaxies. The results agree with a picture where compact groups may form a stable system with galaxies moving in a common dark halo.

scholarly journals Observations of Radio Emission from Normal Galaxies

1963 ◽  
Vol 16 (3) ◽  
pp. 360 ◽  
Author(s):  
DS Mathewson ◽  
JM Rome
Keyword(s):  
Radio Emission ◽  
Radio Source ◽  
Spiral Galaxies ◽  
Radio Sources ◽  
Early Type ◽  
General Belief ◽  
Normal Galaxies ◽  
Discrete Radio Sources

The results of observations of 37 normal galaxies using the 21O-ft steerable reflector of the A.N.R.A.O. at 1410 and 408 Mcls are presented. All southern galaxies brighter than tenth magnitude were studied. Twenty galaxies were detected, fourteen of which were new identifIcationis. Sc galaxies were found to have a mean radio index at 1410 Mcls of +3�3 with an r.m.s. deviation of 0�6. The ratio of optical to radio emission was signifIcantly higher for irregular and early type galaxies than for Sb and Sc galaxies_ Contrary to general belief, no constant relationship was found between the optical and radio sizes of spiral galaxies. Two discrete radio sources were detected in the Pegasus I cluster, one of which may be identified with the El galaxy, NGC 7626. The radio source found in Pegasus II coincided in position with the E3 galaxy, NGC 7501, in the cluster.

scholarly journals Blue Ellipticals in Compact Groups

1990 ◽  
Vol 124 ◽  
pp. 99-103
Author(s):  
Stephen E. Zepf ◽  
Bradley C. Whitmore
Keyword(s):  
Compact Group ◽  
Stellar Evolution ◽  
Spiral Galaxies ◽  
Elliptical Galaxy ◽  
Elliptical Galaxies ◽  
Compact Groups ◽  
Blue Color ◽  
Random Errors ◽  
Dynamical Models ◽  
Group Environment

AbstractWe examine the hypothesis that mergers of spiral galaxies make elliptical galaxies by studying galaxies in compact groups. We combine dynamical models of the merger-rich compact group environment with stellar evolution models and predict that roughly 15% of compact group ellipticals should be 0.15 mag bluer in B – R color than normal ellipticals. The published colors of these galaxies suggest the existence of this predicted blue population, but a normal distribution with large random errors can not be ruled out based on these data alone. However, we have new UBVRI data which confirm the blue color of the two ellipticals with blue B – R colors for which we have our own colors. This confirmation of a population of blue ellipticals indicates that interactions are occurring in compact groups, but a blue color in one index alone does not require that these ellipticals are recent products of the merger of two spirals. We demonstrate how optical spectroscopy in the blue may distinguish between a true spiral + spiral merger and the swallowing of a gas-rich system by an already formed elliptical. We also show that the sum of the luminosity of the galaxies in each group is consistent with the hypothesis that the final stage in the evolution of a compact group is an elliptical galaxy.

scholarly journals On the Correlation of the FIR and Radio Radiation of Spiral Galaxies

1994 ◽  
Vol 159 ◽  
pp. 337-337
Author(s):  
H. M. Tovmassian
Keyword(s):  
Radio Emission ◽  
Spiral Galaxies ◽  
Radio Radiation ◽  
Radio Observations ◽  
Definite Correlation

The comparison of the Byurakan classification of central parts of galaxies with the results of their radio observations showed that there is a definite correlation: the radio emission is more often observed in those galaxies which were suggested to have active nuclei.

scholarly journals The Radio Properties of a Complete Sample of Bright Galaxies

1982 ◽  
Vol 35 (3) ◽  
pp. 321 ◽  
Author(s):  
JI Harnett
Keyword(s):  
Radio Emission ◽  
Radio Telescope ◽  
Spiral Galaxies ◽  
Radio Continuum ◽  
Spectral Indices ◽  
Radio Luminosity ◽  
Complete Sample ◽  
Luminosity Functions ◽  
The Mean

Results are given for the radio continuum properties of an optically complete sample of 294 bright galaxies, 147 of which have been detected. Data were obtained with the 408 MHz Molonglo Radio Telescope. The radio luminosity functions for all galaxies and for spiral galaxies alone are derived and the radio emission for different galaxy types is investigated. Spectral indices of 73 galaxies which had been detected at other frequencies were derived; the mean index of a reliable subsample is <ex) = -0,71.

scholarly journals The Large Scale Distribution of Radio Continuum in E and SO Galaxies

1978 ◽  
Vol 77 ◽  
pp. 49-55
Author(s):  
R.D. Ekers
Keyword(s):  
Radio Emission ◽  
Radio Source ◽  
Large Scale ◽  
Spiral Galaxies ◽  
Elliptical Galaxy ◽  
Elliptical Galaxies ◽  
The Other ◽  
Radio Continuum ◽  
Radio Structure ◽  
Similar Morphology

If we look at the radio properties of the nearby ellipticals we find a situation considerably different from that just described by van der Kruit for the spiral galaxies. For example NGC 5128 (Cen A), the nearest giant elliptical galaxy, is a thousand times more powerful a radio source than the brightest spiral galaxies and furthermore its radio emission comes from a multiple lobed radio structure which bears no resemblance to the optical light distribution (e.g. Ekers, 1975). The other radio emitting elliptical galaxies in our neighbourhood, NGC 1316 (Fornax A), IC 4296 (1333–33), have similar morphology. A question which then arises is whether at lower levels we can detect radio emission coming from the optical image of the elliptical galaxies and which may be more closely related to the kind of emission seen in the spiral galaxies.

scholarly journals Compact groups with a set of positive Haar measure satisfying a nilpotent law

2021 ◽  
pp. 1-4
Author(s):  
ALIREZA ABDOLLAHI ◽  
MEISAM SOLEIMANI MALEKAN
Keyword(s):  
Compact Group ◽  
Haar Measure ◽  
Positive Answer ◽  
Nilpotent Subgroup ◽  
Compact Groups

Abstract The following question is proposed by Martino, Tointon, Valiunas and Ventura in [4, question 1·20]: Let G be a compact group, and suppose that \[\mathcal{N}_k(G) = \{(x_1,\dots,x_{k+1}) \in G^{k+1} \;|\; [x_1,\dots, x_{k+1}] = 1\}\] has positive Haar measure in $G^{k+1}$ . Does G have an open k-step nilpotent subgroup? We give a positive answer for $k = 2$ .

scholarly journals Understanding the origin of radio outflows in Seyfert galaxies using radio polarimetry

2019 ◽  
Vol 15 (S356) ◽  
pp. 247-251
Author(s):  
Biny Sebastian ◽  
Preeti Kharb ◽  
Christopher P. O’ Dea ◽  
Jack F. Gallimore ◽  
Stefi A. Baum ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Radio Emission ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Seyfert Galaxy ◽  
Seyfert Galaxies ◽  
Starburst Galaxies ◽  
Galactic Magnetic Fields ◽  
5 Ghz

AbstractThe role of starburst winds versus active galactic nuclei (AGN) jets/winds in the formation of the kiloparsec scale radio emission seen in Seyferts is not yet well understood. In order to be able to disentangle the role of various components, we have observed a sample of Seyfert galaxies exhibiting kpc-scale radio emission suggesting outflows, along with a comparison sample of starburst galaxies, with the EVLA B-array in polarimetric mode at 1.4 GHz and 5 GHz. The Seyfert galaxy NGC 2639, shows highly polarized secondary radio lobes, not observed before, which are aligned perpendicular to the known pair of radio lobes. The additional pair of lobes represent an older epoch of emission. A multi-epoch multi-frequency study of the starburst-Seyfert composite galaxy NGC 3079, reveals that the jet together with the starburst superwind and the galactic magnetic fields might be responsible for the well-known 8-shaped radio lobes observed in this galaxy. We find that many of the Seyfert galaxies in our sample show bubble-shaped lobes, which are absent in the starburst galaxies that do not host an AGN.

scholarly journals Ends of locally compact groups and their coset spaces

1974 ◽  
Vol 17 (3) ◽  
pp. 274-284 ◽  
Author(s):  
C. H. Houghton
Keyword(s):  
Compact Group ◽  
Direct Product ◽  
Compact Space ◽  
Locally Compact Group ◽  
Locally Compact Groups ◽  
Compact Groups ◽  
Countable Base ◽  
Locally Compact ◽  
Coset Spaces ◽  
Compact Boundary

Freudenthal [5, 7] defined a compactification of a rim-compact space, that is, a space having a base of open sets with compact boundary. The additional points are called ends and Freudenthal showed that a connected locally compact non-compact group having a countable base has one or two ends. Later, Freudenthal [8], Zippin [16], and Iwasawa [11] showed that a connected locally compact group has two ends if and only if it is the direct product of a compact group and the reals.

scholarly journals 12. The measurement of the distance of the radio sources

1957 ◽  
Vol 4 ◽  
pp. 71-79 ◽  
Author(s):  
R. D. Davies ◽  
D. R. W. Williams
Keyword(s):  
Radio Emission ◽  
Surface Area ◽  
Radio Astronomy ◽  
Angular Size ◽  
Radio Sources ◽  
Absolute Luminosity

In radio astronomy it is becoming increasingly important to know the distance of the radio sources. An identification with astronomical objects observed optically is then more readily obtained and this in turn may allow further investigation of the mechanism of radio emission. A measurement of the distance of sources will also resolve the problem of their distribution in space, showing which are galactic and which are extra-galactic. Furthermore the surface area and absolute luminosity can be estimated from a knowledge of the distance and angular size of a source.

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