排序方式： 共有40条查询结果，搜索用时 127 毫秒
1.
2.
M. V. Gyulzadyan J. A. Stepanian A. R. Petrosian D. Kunth B. McLean G. Comte 《Astrophysics》2003,46(2):131-143
The Second Byurakan Survey (SBS) is a well known combined survey, which uses the presence of UV-excess radiation in the continuum, or the presence of emission-lines in the spectra for the identification of active and star-forming galaxies. This paper reports on a comparative study of 77 galaxies identified with UV-excess, and 34 galaxies identified via emission-line techniques in the fields of the SBS. The spectroscopic parameters used for the comparison are the [OII]3727/H and [OIII]5007/H emission-lines ratios, the equivalent widths of [OII]3727, [OIII]5007 and H emission-lines, and the C
[OII]-C
H index. Spectroscopic parameters as well as new redshifts were determined from the spectra obtained with the 6m telescope of the Special Astrophysical Observatory (Russia). The main results are: 1) Galaxies discovered via UV-excess technique are preferably more active. 2) Galaxies discovered via emission-line technique are preferably high-excitation low-luminosity star-forming galaxies. 3) UV-excess galaxies with faintest UV-excess radiation are likely candidates to be LINER or Sy2 type objects. 相似文献
3.
The subclustering within the Local Group is studied by means of the recently developed treediagram technique, enabling one to establish substructures of different boundness. Thirty-two galaxies from 39 listed are shown to form an interacting system which includes Milky Way and M31 giant spirals; we define the Local Group as that interacting system only. Second-level boundness indicates two clear subsystems, influenced by Milky Way and that of M31. The search of systems bound stronger, specifies several pair galaxies of similar morphology. 相似文献
4.
The observed correlations between X-ray and type III radio emissions from solar bursts are described by means of a bivariate distribution function. Procedures for determining the form of this distribution are described using a sample of data analyzed by Kane (1981). With the help of this distribution a model is constructed to explain the correlation between the X-ray spectral index and the ratio of X-ray to radio intensities. Implications of the model are discussed. 相似文献
5.
We analyze the data presented in a previous paper by Gyulzadyan and Petrosian, and discuss the results of a statistical investigation
of the relationship between SBS galaxies and Zwicky clusters. The main results are that SBS galaxies follow the overall galaxy
distribution in clusters and they do not avoid any type of Zwicky cluster. There is a significantly higher probability of
finding SBS galaxies occurring in medium compact clusters than in open clusters. They also follow the well-established morphology-density
relation. Earlier morphological type, higher luminosity, larger linear size, and redder SBS galaxies tend to be found in clusters
with higher compactness, or in more compact regions of the clusters. The number distribution of SBS galaxies in Zwicky open
clusters probably follows the distribution of normal galaxies. The number distribution of SBS galaxies in medium compact and
compact clusters shows two-maxima structure.
Published in Astrofizika, Vol. 52, No. 2, pp. 225–236 (May 2009). 相似文献
6.
A statistical study of the dependence of the star formation rate in the nuclear regions of 39 Kazarian galaxies on the integral
parameters of these galaxies is carried out on the basis of spectra from SDSS DR6. The value of SFR/kpc2 for our sample lies in the range 0.013÷2.04M
⨀ year−1kpc−2 (with the maximum value of 2.04 corresponding to the Kaz 98 (merger)). It is found that the surface density of the rate of
star formation correlates positively with the bar structure parameter and EW(Hα), and that, for spiral galaxies of early morphological types, SFR/kpc2 is greater than for the later types. It is shown that the color B-R for the galaxies and the color (u − g)
nucl
for the nuclear region correlate positively with the total absorption A(Hα) in the Ha line for the nuclear region. The average value of A(Hα) for our samples is found to be A(Hα)=1.3±0.09 magnitudes.
Translated from Astrofizika, Vol. 52, No. 2, pp. 211–224 (May 2009). 相似文献
7.
8.
A list is presented of 122 new galaxies with UV excess observed on plates obtained using the 40″ Schmidt telescope at the Byurakan Observatory with a 1°.5 objective prism. It is shown that the relative number of galaxies with a strong UV excess (classes 1 and 2) listed in Table 1 is roughly 55.7%. This is 6.7% higher than for the previously observed galaxies. These samples also differ in terms of the morphology of the spectra. The largest deviation, approximately 9.9%, occurs for type “sd.”__________Published in Astrofizika, Vol. 48, No. 3, pp. 393–408 (August 2005). 相似文献
9.
Widespread Plio-Pleistocene (2.43-0.06 Ma) tephra zones recognised in deep-sea cores from high latitudes (>60°) in the Southern Pacific Ocean were thought to have originated from calc-alkaline rhyolitic eruptions in New Zealand, some 5000 km distant. Electron microprobe analyses of the glasses reveal a wide diversity of alkalic felsic compositions, as well as minor components of basic and intermediate glasses, incompatible with a New Zealand Neogene source but similar to contemporaneous eruptives from the Antarctic region. Most tephra zones are trachytic; seven zones are peralkaline rhyolite. The rhyolitic zones represent a deep-sea record of widespread silicic eruptions from continental Antarctica, possibly Marie Byrd Land. The extent of these rhyolitic zones suggest a greater frequency of large explosive eruptions in Antarctica than previously documented. The coarse grain size of some of the shards (up to 3 mm), their great distance from the closest sources (>1600 km for some cores), and the presence of nonvolcanic ice-rafted debris indicate some of the glasses, especially the more basic compositions, may have been ice-rafted, contrary to previous suggestions of a fallout origin. 相似文献
10.
J. M. Mas-Hesse D. Kunth H. Atek G. Östlin C. Leitherer A. Petrosian D. Schaerer 《Astrophysics and Space Science》2009,320(1-3):35-38
The Lyα line is an important diagnostic of star formation and activity in galaxies. The analysis of Lyα is complicated due to the resonant nature of the line and radiative transfer effects. High spectral resolution studies of local starburst galaxies with the unprecedented UV capabilities of the HST have shown that this line is either seen in absorption or in emission and in the latter case with a P?Cygni profile indicative of a large scale outflow of neutral gas. Moreover, HST imaging obtained with HST-ACS of a sample of 6 star-forming galaxies has revealed that a substantial fraction of the Lyα photons are diffused far away from the emissive knots. Since the importance of Lyα for tracing large scale structure, correlation functions, and galaxy formation is recognized, Lyα will remain a very important probe of the distant universe for the foreseeable future, and it is therefore imperative to acquire a better understanding of what mechanisms regulate our ability to detect this line. 相似文献