共查询到20条相似文献，搜索用时 406 毫秒
1.
The surroundings of 75 active SB galaxies are investigated. It is shown with a fairly high degree of certainty that more galaxies are observed in the direction of the bar than in other directions. It is concluded that this may be a consequence of the galaxy-forming activity of these galaxies. It is noted that the influence of the surroundings on a galaxy is traditionally discussed, although there is much evidence that the surroundings of a galaxy are shaped due to its activity. 相似文献
2.
We report on the statistical analysis of a sample of AGNs (Seyferts and LINERs) selected from an RBSC-NVSS sample of the brightest X-ray sources. The sample is large enough and unbiased for a detailed study of multi-frequency (radio to X-ray) properties of AGN. There are no significant differences in X-ray, optical, far-infrared, and radio powers, core dominance, radio loudness, radio spectral index, and two-point radio-to-optical and optical-to-X-ray spectral indices of Seyfert types 1 and 2. These findings strongly support the unification model, and the observed differences between Sy1 and Sy2 are due to both the variable obscuration and different geometric orientation effects. The correlation between the X-ray and radio emission over many decades is primary and indicates the intrinsically similar origin of both radiations in Seyfert galaxies, powered mainly by AGN, rather than compact starbursts. For Seyfert galaxies we found that the slopes of the relations L
X - L
R and L
X - L
B are flat, which indicate the existence of components unrelated with X-ray. Perhaps only for LINERs is the observed L
X - L
R relation completely due to AGNs. The Sy1, Sy2, and LINER galaxies show different slopes in the relation L
X - L
1.4, and the relative contribution of extended radio components may be the cause of these differences. The possible effects of unresolved extended radio and X-ray components are quantitatively discussed. 相似文献
3.
The results of the spectroscopic observation of 23 galaxies with a UV excess from Kazarian's lists are presented. The spectra were obtained on the 2.6-m telescope of Byurakan Observatory with a Byu FOSC-2 camera. Two grisms, red and green, were used in the observations. Emission lines are observed in the spectra of 21 of the galaxies. 相似文献
4.
The results of spectroscopic observations of 28 galaxies of the Second Byurakan Sky Survey, completing the follow-up spectroscopy of galaxies in the survey field with central coordinates = 12h22m, = +35°, are presented. The spectra were obtained on the 2.6 m telescope of the Byurakan Astrophysical Observatory, National Academy of Sciences of the Republic of Armenia, and the 6 m telescope of the Special Astrophysical Observatory, Russian Academy of Sciences. The redshifts and absolute stellar magnitudes of all the galaxies have been determined. A preliminary analysis of the spatial distribution of all galaxies in this sample is given. 相似文献
5.
Data from the H I Parkes All-Sky Survey (HIPASS) of the southern sky in the neutral hydrogen line are used to determine the radial velocities and widths of the H I line for flat spiral galaxies of the Revised Flat-Galaxy Catalog (RFGC) seen edge-on. The sample of 103 flat galaxies detected in HIPASS is characterized by a median radial velocity of +2037 km/sec and a median width of the H I line at the level of 50% of maximum of 242 km/sec. For RFGC galaxies the 50% detection level in HIPASS corresponds to an apparent magnitude B
t = 14
m
.5 or an angular diameter a = 2.9. The relative number of detected galaxies increases from 2% for the morphological types Sbc and Sc to 41% for the type Sm. The median value of the ratio of hydrogen mass to total mass for RFGC galaxies is 0.079. With allowance for the average internal extinction for edge-on galaxies, <B
t< = 0
m
.75, the median ratio of hydrogen mass to luminosity, M
H I/L
B = 0.74 M
/L
, is typical for late-type spirals. Because of its small depth, HIPASS reveals only a few RFGC galaxies with previously unknown velocities and line widths. 相似文献
6.
7.
In this paper we present the H map, the 2D velocity field and the rotation curve of the galaxy NGC 784 obtained with the ByuFOSC2 scanning Fabry-Perot interferometer, attached at the prime focus of the 2.6-m telescope of Byurakan Observatory. The H image shows several HII condensations along the major axis of the galaxy. The galaxy has an asymmetric distribution of the H emission. The rotation curve is quite symmetric with a low gradient in the central part of the galaxy. 相似文献
8.
A sample of galaxy groups is investigated for the occurence of Seyfert objects within them. The velocity dispersion in groups with Seyfert galaxies is significantly larger than in groups without Seyfert galaxies. But there was not found any correlation between the galaxy density within the groups and the content of Seyfert galaxies. 相似文献
9.
H.M. Tovmassian 《Astronomische Nachrichten》2001,322(2):87-91
It is shown that the samples of Seyfert galaxies used to study different parameters of Seyferts are largely incomplete. The way of estimation of the number of the missed, not detected Seyferts is proposed. It is based on the assumption that distribution of inclinations of Seyferts should be similar to that of spiral galaxies. Addition of the estimated number of the missed Seyferts allows to deduce more correct value of the ratio of numbers of Sy2s to Sy1s, N2/N1. The more real value of the ratio N2/N1 is the one deduced by using the results of counts of bright, nearby Seyferts, and is equal to ∼4. The opening angle of the dust torus is ∼76°. 相似文献
10.
The relevance of interaction to the presence of Seyfert or starburst activity in the nuclei of galaxies is examined. We focus the attention on the close environments of spectroscopically selected samples of Seyfert-1, Seyfert-2 and starburst galaxies. In particular the results of a statistical procedure aimed at finding physical pairs are tested with redshift measurements of the identified pairs. Seyfert and starburts galaxies show an excess of physical companions compared to normal galaxies. This excess tends to increase as one moves from Seyfert to starburst galaxies. 相似文献
11.
Spectroscopic data are presented for 35 galaxies from selected fields of the Second Byurakan Survey (SBS). The observations were made on the 2.6 m telescope at the BAO using the SCORPIO spectral camera. A majority of the objects were observed for the purpose of improving the classification of types in accordance with an adapted scheme presented in this paper. 相似文献
12.
The local face-on disk galaxies are selected as galaxy sample from the main galaxy sample of the Seventh Data Release of Sloan Digital Sky Survey (SDSS DR7). The correlations between the colors and sizes of disk galaxies with equivalent total stellar masses are statistically investigated and their realities are tested. It is found that for the disk galaxies with equivalent masses, the correlation between u-r color and size is very weak. However, there are anticorrelations between g-r, r-i, r-z colors and sizes, i.e., the larger are the sizes of galaxies, the bluer are their colors. This result means that the mass distribution of disk galaxies has a significant influence on their star formation history. The galaxies with more extended mass distributions evolve more slowly. 相似文献
13.
14.
15.
Tian-Zhi Zhang Xue-Bing WuDepartment of Astronomy School of Physics Peking University Beijing 《中国天文和天体物理学报》2002,2(6)
The sizes of the Broad Line Region (BLR) of some Seyfert 1 galax-ies and nearby quasars can be determined by the reverberation mapping method.Combining with the observed FWHM of Hβ emission line and assuming that themotion of BLR clouds is virialized, the black hole masses of these objects have beenestimated. However, this method strongly depends on the poorly-understood geom-etry and inclination of the BLR. On the other hand, a tight correlation between theblack hole mass and the bulge velocity dispersion was recently found for both activeand nearby inactive galaxies. This may provide another method, independent of theBLR geometry, for estimating the black hole mass. Using this method for estimatingthe black hole mass and combining with the measured BLR size and FWHM of Hβemission line, we derived the BLR inclination angles for 20 Seyfert I galaxies underthe assumption that the BLR is disk-like. The derived inclination angles agree wellwith those derived previously by fitting the UV continuum and Hβ emission lineprofiles. Adopting a relation between the FWHMs of [OⅢ]λ5007 forbidden line andthe stellar velocity dispersion, we also estimated the BLR inclinations for 50 nar-row line Seyfert 1 galaxies (NLSls). We found that the inclinations of broad LineSeyfert 1 galaxies (BLS1s) are systematically greater than those of NLS1s, whichseldom exceed 30. This may be an important factor that leads to the differencesbetween NLS1s and BLS1s if the BLR of NLS1s is really disk-like. 相似文献
16.
We summarize here some ongoing work by our group on the formation and evolution of barred galaxies. We first discuss the evolution
of bars in isolated disc galaxies. Then we address the problem of bar destruction during interactions and mergers. Finally
we describe work on generation and regeneration of bars in interactions.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
17.
R. Caimmi 《Astronomische Nachrichten》1992,313(3):165-182
This paper investigates the effect of the initial shape of expanding, homogeneous, ellipsoidal density perturbations, at some special stages of evolution, namely at the occurrence of: (i) turn-around along the axes, (ii) maximum volume, (iii) strong decoupling from the Hubble flow, assumed to take place at overdensities equal to unity. To this aim, previous theory is reviewed and extended involving – among others – a deep analysis on the gravitational force induced on the unit mass at the top axes of the ellipsoid, an explicit expression of the overdensity, and a detailed investigation on the limiting cases of flat (two-dimensional) and oblong (one-dimensional) configurations. Then some physical parameters related to the above mentioned stages of evolution are computed for a wide range of initial shapes, in connection with an Einstein-de Sitter universe and an initial overdensity, which is typical for inhomogeneities with galactic masses in a classical CDM scenario. If the gain of spin by tidal torques grows in proportion to time until either the stage of evolution (i) or (ii), or (iii) is attained, it is found a difference in angular momentum related to the initial shape, which never exeeds a factor of about 3.6, 2.0, 1.4, respectively. 相似文献
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20.
R.I. Davies A. Burston M.J. Ward 《Monthly notices of the Royal Astronomical Society》2002,329(2):367-376
We present 0.5-arcsec-resolution near-infrared images of six ultraluminous infrared galaxies with known redshifts. Six of the eight bright nuclei are resolved on kiloparsec scales, suggesting that there is significant circumnuclear star formation or close progenitor nuclei. At this spatial resolution, the nuclei have very red colours that cannot in general be reproduced by reddening stellar light, but require an additional component of hot dust emission. In five of the six primary nuclei more than 20 per cent of the K -band continuum originates in hot dust, but the temperature cannot be determined by JHK broad-band colours alone. Comparison with the spectral shapes, however, does allow the temperature to be constrained, and we find in every case that it is at the upper end of the permissible range, ≳1000 K. This does not necessarily imply that there is an active galactic nucleus present, since there is evidence that stellar processes can also generate dust this hot via stochastic heating of small grains. The quantities of hot dust we have found here can make up to 0.5-mag difference to the K -band magnitude even at , with implications for observations and population synthesis models of higher-redshift objects. Observations in the L or M bands, where hot dust is most important at , could help to discriminate between models of dusty starbursts and ellipticals. 相似文献