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1.
Results are presented from CCD BVRI observations of comparison stars in the neighborhoods of 22 galaxies with active nuclei having right ascensions ranging from 0 to 12 hours, of which 19 are Seyfert galaxies. The observed stars have magnitudes ranging from V=11 to V=17. For stars brighter than V=14 the typical photometic error is 0.01m. The B, V, Rc, and Ic magnitudes of most of these stars were not known previously. 14′×14′ finding charts are included. These results can be used for differential photometry of the AGNs in the B, V, Rc, and Ic bands.__________Translated from Astrofizika, Vol. 48, No. 2, pp. 191–211 (May 2005).  相似文献   

2.
The characteristics of gravitational bursts from active galactic nuclei, and globular clusters are obtained for three astrophysical situations:(i) scattering of stars by massive black holes residued at the centers of galaxies and globular clusters; (ii) the close encounters of stars in the nuclear regions of these objects; (iii) scattering of stars by black holes of stellar mass containing in the stellar population of galactic nuclei and clusters. The most effective source of gravitational bursts appears to be a scattering of stars by the massive central black holes which produces the bursts with dimensionless amplitudeh10–19–10–21 and frequencies from 10–1 to 10–5 Hz. The characteristics obtained correspond to the possiblities of a future gravitational-wave experiment with use of laser Doppler tracking of interplanetary spacecrafts.  相似文献   

3.
Stellar photometry of images from the ACS and WFPC2 cameras on the Hubble Space Telescope (HST) is used to study the star composition and spatial distribution of stars in three edge-on visible spiral galaxies: NGC 891, NGC 4144, and NGC 4244. Measurements of the surface number density of old stars revealed two stellar subsystems in these galaxies: a thick disk and a halo. The boundaries of these subsystems, which consist mainly of red giants, are determined from the change in the gradient of the number density of the stars. The halos are flattened at the poles of the galaxies and extend to distances of 8–25 kpc from the planes of the galaxies. The present results on the number density distribution of stars with different ages perpendicular to the planes of these galaxies make it possible to improve our model for the stellar structure of spiral galaxies. The distances to these galaxies are calculated using a determination of the tip of the red giant branches (the TRGB method): D = 9.82 Mpc (NGC 891), D = 7.24 Mpc (NGC 4144), and D = 4.29 Mpc (NGC 4244).__________Translated from Astrofizika, Vol. 48, No. 2, pp. 261–280 (May 2005).  相似文献   

4.
It is shown that a universal steady X-ray background with the energy flux 10–7 erg cm–2 s–1 sr–1 can arise as a superposition of radiation from pulsars (neutron stars) in various galaxies when it is taken into account that supernova outburst occurs in a galaxy at the rate of 10–2/year.  相似文献   

5.
Results are presented from CCD BVRI-observations of 145 comparison stars in the neighborhoods of 14 Seyfert galaxies, 3 quasars, and 5 BL Lac objects with right ascensions of 12 to 24 hours. The magnitudes of the observed stars ranged from V=11 to V=17. The typical photometric error for stars brighter V=14 is 0m.01. The B, V, Rc, and Ic magnitudes of most of these stars were not known previously. 14′ x 14′ finding charts are provided. These results can be used for differential photometry of the nuclei of active galaxies in the B, V, Rc, and Ic bands.__________Translated from Astrofizika, Vol. 48, No. 3, pp. 365–379 (August 2005).  相似文献   

6.
To study the spatial distribution of galaxies lying between the Virgo cluster and the Local Group, a search was made for probable nearby galaxies. Using the method of brightest stars and of blue and red supergiants made it possible to determine the distances to 24 galaxies, among which six relatively nearby galaxies were identified. The results of the distance determinations showed that the maximum in the number distribution of galaxies lies at 17.0 Mpc, which we take as the distance to the Virgo cluster. Using the difference between the distance moduli of two clusters of galaxies, in Virgo and Coma Berenices, from literature sources and the velocity of the latter cluster, we determined the Hubble constant to be H 0 = 77 ± 7 km·sec–1·Mpc–1.  相似文献   

7.
Multi-aperture photometry of 262 bright southern galaxies in the JohnsonUBV system is given. Most of these are south of =–30°, although some northward to =–10° are included. A total of 169 objects have published radial velocity determinations. These provide distances, and enable construction of colour-magnitude diagrams for this subset of bbjects through a physical diameter of 2.0 kpc (withH o=100). The two-colour diagrams for the inner regions of the galaxies differ from those of integrated galaxies due to the colour changes towards their centres. Comparison with theoretical models of Larson and Tinsley (1978) suggest that the colours of the inner portions of most ellipticals and lenticulars are consistent with their having all stars formed at nearly one epoch with little subsequent star formation, while for spirals larger amounts of star formation, either in bursts or continuously, are suggested. This simple picture is complicated by the presence of certain objects having peculiar colours indicative of large amounts of recent star formation.  相似文献   

8.
Self-consistent simulations of seven groups of galaxies with halos have been performed to find a constraint upon the size of missing halos around spiral galaxies. An initial galaxy, which consists of 100 superstars, has half-mass radius 41 kpc and central velocity dispersion 235 km s–1. The simulations start from the epoch of maximum expansion. The initial conditions involve a variety of spatial distributions of galaxies, and the velocity dispersion of galaxies as would be permitted for maximum expansion. Dense groups having collapse times shorter than (2/3)H 0 –1 are shown to form multiple mergers in a Hubble timeH 0 –1 . From a comparison of the frequencies of cD galaxies, or multiple mergers, in observed and simulated groups, it is concluded that the effective radius of missing halos is less than 41 kpc.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.  相似文献   

9.
The distributionsf(z) of the redshifts for active galaxies (Seyfert galaxies, radio galaxies, and quasars) have been studied. Some statistically-significant maxima and minima are observed in the distributionsf(z) for these objects. The significance of peaks and gaps increases for the brighter objects, for which the samples are more complete. The clustering of the Seyfert galaxies is significantly different from that of the nearby normal galaxies. The distributionf(z) for the radio galaxies is similar to the analogous distribution for the galaxy clusters. Three of the five peaks in the distributionf(z) for the radio quasars may be caused by the selection effects. Two peaks within the intervalsz (0.5, 0.7) and (1.0, 1.1) are probably real. The corresponding scales of the QSO clustering along the line-of-sight are about 100h –1 Mpc (h is the Hubble constant in the units of 75 km s–1 Mpc–1). The possibility of some global quasi-periodical cycles for the processes of activity is discussed. The period of a cycle for the Seyfert and radio galaxies is about 1×108 years that corresponds to the distances of about 30h –1 Mpc between the shells.  相似文献   

10.
OASIS observations obtained at the Canada–France–Hawaii Telescope for the spiral galaxies NGC 4900 and NGC 5430 produce one spectrum for each 0.41″ element of the 11″ × 15″ field of view. This allows for the spatial characterisation of the different stellar populations. From these observations we study the young (10 Myr) and older stellar populations using evolutionary synthesis codes. Based on the gas emission lines, we find that the young populations are located in relatively small regions and dominate the integrated flux. In NGC 4900, the young populations are distributed in a bar-like structure featuring a hole near the position of the galaxy’s centre. The young stellar populations of NGC 5430 form a nuclear ring and two patches at the base of the spiral arms. Based on Mg2 and FeI absorption lines, we find that in both galaxies, the young stars are superimposed on a relatively homogenous population of a few Gyr.  相似文献   

11.
Evolutionary model sequences for (X, Z)=(0.7,4×10–3) are constructed by using the same input physics and programming code as those of Saioet al. (1977). From these results the ages of globular clusters are estimated under the assumption of constant helium abundance (Y=0.3). The results suggest that there is a correlation between age and metal abundance for the globular clusters and that metal enrichment in the Galaxy slowly proceeded in several billion years from the value of the extreme Population II stars to that of the Population I stars. Comparison with some models of chemical evolution of galaxies is briefly made.  相似文献   

12.
The observational approach to the early stages of stellar evolution has been applied to some problems relating to the formation and dissipation of stellar associations, the origin of OB field stars, and low-mass star formation in OB associations. The OB field stars ejected from parent associations are older on the average than the OB stars in the associations. The average duration of active OB-star formation in associations is evaluated. It is suggested that, under the conditions in OB associations, low-mass stars may be formed from dense protostellar objects.Translated fromAstrofizika, Vol. 39, No. 3, pp. 393–406, July–September, 1996.  相似文献   

13.
On the basis of extensive observational material it is statistically demonstrated that dwarf galaxies appear more often around barred galaxies than around normal spiral galaxies. Moreover, the more barred spiral galaxies there are in a given region, the more dwarf galaxies are found there as well.Translated from Astrofizika, Vol. 38, No. 1, pp. 45–53, January–March, 1995.  相似文献   

14.
Summary In the solar neighborhood, approximately half of all intermediate mass main sequence stars with initially between 1 and about 5 Mbecome carbon stars with luminosities near 104 L for typically less than 106 years. These high luminosity carbon stars lose mass at rates nearly always in excess of 10–7 M yr–1 and sometimes in excess of 10–5 M yr–1. Locally, close to half of the mass returned into the interstellar medium by intermediate mass stars before they become white dwarfs is during the carbon star phase. A much greater fraction of lower metallicity stars become carbon-rich before they evolve into planetary nebulae than do higher metallicity stars; therefore, carbon stars are much more importan t in the outer than in the inner Galaxy.  相似文献   

15.
We consider a galaxy moving in a cluster of galaxies and study the effects of compression of the gas disc by both thermal and dynamical pressures of intergalactic gas. As the result of compression, massive gas clouds are formed. They are not stripped by dynamical pressure of the intergalactic gas but stay in the galaxy until they are disrupted by formation of massive stars.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.  相似文献   

16.
Far-ultraviolet photometric data for early type stars in Orion, in the 1050–1180 and 1230–1350 Å wavelength ranges, were obtained in an Aerobee rocket flight on 30 January 1969. The results corrected for interstellar extinction, appear in good agreement with model atmospheres in the case of main-sequence stars. Bright giant and supergiant stars, however, appear to be up to one magnitude fainter than main-sequence stars of similar spectral class in the 1050–1180 Å range.The present results indicate that the detectors used in a previous flight were lower in sensitivity than was thought, so the results from that flight have been corrected using the present data for stars in common with the previous flight.The far-ultraviolet extinction law for Orionis is shown to be abnormal, with the observed extinction far less than predicted on the basis of ultraviolet extinction measurements of other stars, and the observedE(B-V).  相似文献   

17.
We present new interferometric observations of the molecular gas distribution and kinematics in the nuclei of different active galaxies at high angular resolution and high sensitivity carried out with the IRAM Plateau de Bure interferometer (PdBI). The observations cover galaxies in a redshift range of 0.03–1.4. We have so far observed five different active galaxies: NGC3718, NGC1068, HE1029–1831, 3C48 and Q0957+561. The first two objects belong to the NUGA (NUclei of GAlaxies) project – an international collaboration mainly between Spain, France and Germany – containing about 30 Seyfert and LINER galaxies. Both are at the same distance of 14Mpc and show a warped gas and dust disk. The new mosaic map of NGC3718 corrected for short-spacing effects with IRAM 30 m observations well demonstrates the existence of the warped gas disk with several secondary maxima in the projected gas distribution caused by orbit crowding effects. Based on these new data we have improved recent simulations of the warped disk in NGC3718. HE1029–1831 and 3C48 are nearby QSOs. HE1029–1831 is taken out of the Cologne nearby QSO sample. The maps of the integrated CO(1–0) and CO(2–1) emission clearly show that the molecular gas is mostly related to the central bulge with a non-negligible fraction distributed along the bar known from optical observations. Our new CO data of 3C48 unveil new information about the kinematics of its molecular gas complementing and improving further studies based on previous infrared observations and detailed multi-particle simulations. Finally, new measurements of the CO(1–0) line in Q0957+561 – a highly-red-shifted, gravitationally lensed quasar – will be presented as a link to earlier evolutionary stages of active galaxies and their hosts.  相似文献   

18.
There is strong evidence for some kind of massive dark object in the centres of many galaxy bulges. The detection of flares from tidally disrupted stars could confirm that these objects are black holes (BHs). Here we present calculations of the stellar disruption rates in detailed dynamical models of real galaxies, taking into account the refilling of the loss cone of stars on disruptable orbits by two-body relaxation and tidal forces in non-spherical galaxies. The highest disruption rates (one star per 104 yr) occur in faint ( L ≲1010 L⊙) galaxies, which have steep central density cusps. More luminous galaxies are less dense and have much longer relaxation times and more massive BHs. Dwarf stars in such galaxies are swallowed whole by the BH and hence do not emit flares; giant stars could produce flares as often as every 105 yr, although the rate depends sensitively on the shape of the stellar distribution function. We discuss the possibility of detecting disruption flares in current supernova searches. The total mass of stars consumed over the lifetime of the galaxy is of the order of 106 M⊙, independent of galaxy luminosity; thus, disrupted stars may contribute significantly to the present BH mass in galaxies fainter than ∼109 L⊙.  相似文献   

19.
It is argued that a Salpeter initial luminosity function is consistent with the observed integral properties of giant elliptical galaxies if the gaseous material lost by evolving stars can be retained in the system for times of the order of 108 yr. One model which emerges is of a highly condensed system consisting mainly of metal-poor population II stars with an admixture (1.5%–15%) of super-metalrich stars born from the gaseous debris, which at the present time constitutes 0.05%–0.5% of the total mass. HighM/L ratios result from obscuration of the starlight, and the missing radiation reappears in the form of a strong I-R flux at wavelengths of the order of 100 . The difference in colour betweengE anddE galaxies is explained in terms of interstellar reddening, and strong interstellar metallic absorption lines are also expected. The model leads to a negligible evolutionary correction to the cosmological deceleration parameterq 0. An alternative model, in which the stars arenot metal poor, has a more condensed, heavily obscured nucleus, surrounded by the unobscured central bulge of the Galaxy which provides most of the light. In this version a large evolutionary correction would be required.  相似文献   

20.
IntegratedUBV colours have been computed for synthetic clusters older than one billion years and for two chemical composition: (a)Y=0.30;Z=10–4 and (b)Y=0.30;Z=10–2, taking into account the contribution to the integrated light of Main Sequence, subgiant, red giant and horizontal branch stars. It has been found that integrated colours depend onZ and allow an estimate of the metal content, however not generally. Horizontal branch stars contribute to the integrated colours of clusters not significantly and the contribution of stars in more advanced phases (e.g., asymptotic branch stars) is almost negligible.Old clusters in LMC and SMC have been studied in terms of colour calibrations and this analysis has been supplemented, when possible, by photometric and spectroscopic data of individual stars. It was found that in the LMC clusters withZ=10–2 andt>5×109 yr are lacking, clusters with relatively blue colours are similar, both in age and chemical composition, to the halo galactic globular clusters. Moreover, there is a group of clusters with 1×109t5×109. In the SMC clusters withZ=10–2 andt>5×109 yr are lacking and clusters with 1×109t5×109 are rare. Clusters with relatively blue colours are interpreted with the following parameters:t=5×109 yr, 10–4Z10–3 andY=0.20.The implication of these results on the chemical history of the two galaxies is discussed.  相似文献   

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