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1.
Based on archival Hubble Space Telescope images, we have performed stellar photometry for the galaxy M 101 and other neighboring galaxies located at a small angular distance from M 101 and having radial velocities similar to that of M 101: M 51, M 63, NGC 5474, NGC 5477, UGC 9405, Ho IV, KUG1413+573, and others. Based on the TRGB method, we have determined the distances to these galaxies. We have found that the M 101 group lies at a distance of 6.8 Mpc and is a small compact galaxy group consisting of four galaxies: NGC 5474, NGC 5477, UGC 9405, and Ho IV. The bright massive galaxies M 51 and M 63 are considerably farther (D = 9.0 and 9.3 Mpc, respectively) than the M 101 group and do not belong to it. Applying the virial theorem to 27 objects (H II regions and galaxies),M 101 satellites located at different distances from the galaxy, has revealed an increase in the dynamical mass of M 101 with increasing sizes of the system of satellites used in calculating the mass. The maximum calculated mass of M 101 is 7.5 × 1011 M ⊙. The dynamical mass of M 101 calculated on the basis of the four galaxies constituting the group is 6.2 × 1011 M ⊙. The mass-to-light ratio for this mass is M/L = 18 (at the adopted luminosity of M 101, M B = ?20.8).  相似文献   

2.
We analyze the properties of the clusters of galaxies in the region of the Ursa Major (UMa) supercluster using observational data from SDSS and 2MASS catalogs. The region studied includes a supercluster (with a galaxy and cluster overdensity of 3 and 15, respectively) and field clusters inside the 150-Mpc diameter surrounding region. The total dynamical mass of 10 clusters of galaxies in UMa is equal to 2.25 × 1015 M ⊙, and the mass of 11 clusters of galaxies in the UMa neighborhood is equal to 1.70 × 1015 M ⊙. The fraction of early-type galaxies brighter than M K * + 1 in the virialized regions of clusters is, on the average, equal to 70%, and it is virtually independent on the mass of the cluster. The fraction of these galaxies and their average photometric parameters are almost the same both for UMa clusters and for the clusters located in its surroundings. Parameters of the clusters of galaxies, such as infrared luminosities up to a fixed magnitude, the mass-to-luminosity ratio, and the number of galaxies have almost the same correlations with the cluster mass as in other samples of galaxies clusters. However, the scatter of these parameters for UMa member clusters is twice smaller than the corresponding scatter for field clusters, possibly, due to the common origin of UMa clusters and synchronized dynamical evolution of clusters in the supercluster.  相似文献   

3.
We present our B, V, Rc, and Ic observations of a \(3'.6 \times 3'\) field centered on the host galaxy of GRB 000926 (α2000.0=17h04m11s, \(\delta _{2000.0} = + 51^ \circ 47'9\mathop .\limits^{''} 8\)). The observations were carried out on the 6-m Special Astrophysical Observatory telescope using the SCORPIO instrument. The catalog of galaxies detected in this field includes 264 objects for which the signal-to-noise ratio is larger than 5 in each photometric band. The following limiting magnitudes in the catalog correspond to this limitation: 26.6 (B), 25.7 (V), 25.8 (R), and 24.5 (I). The differential galaxy counts are in good agreement with previously published CCD observations of deep fields. We estimated the photometric redshifts for all of the cataloged objects and studied the color variations of the galaxies with z. For luminous spiral galaxies with M(B)z～1.  相似文献   

4.
We report a catalog of 168 galaxy triplets with line-of-sight velocities V LG < 3500 km/s identified using a percolation criterion, which takes individual properties of galaxies into account. The catalog contains the line-of-sight velocities, K-band magnitudes, and morphological types of galaxies. Our sample of galaxy triplets is characterized by the median values of the line-of-sight velocity dispersion, projected harmonic radius, and crossing time of 40 km/s, 155 kpc, and 3 Gyr, respectively. The median projectedmass and K-band luminosity of our triplets are equal to 5 × 1011 M ⊙ and 15M ⊙/L ⊙, respectively, with the uncertainty of these parameters due mostly to the errors of radial-velocity measurements. The basic properties of triple systems in the Local Supercluster are compared to those of more distant isolated triplets from the KTG and KTS samples. The fraction of triplet members among all galaxies is found be more than 5%.  相似文献   

5.
We used the Revised Flat Galaxy Catalog (RFGC) to select 817 ultra-flat (UF) edge-on disk galaxies with blue and red apparent axial ratios of (a/b)B > 10.0 and (a/b)R > 8.5. The sample covering the whole sky, except the Milky Way zone, contains 490 UF galaxies with measured radial velocities. Our inspection of the neighboring galaxies around them revealed only 30 companions with radial velocity difference of | ΔV |< 500 kms?1 inside the projected separation of Rp < 250 kpc. Wherein, the wider area around the UF galaxy within Rp < 750 kpc contains no other neighbors brighter than the UF galaxy itself in the same velocity span. The resulting sample galaxies mostly belong to the morphological types Sc, Scd, Sd. They have a moderate rotation velocity curve amplitude of about 120 km s?1 and a moderate K-band luminosity of about 1010L⊙. The median difference of radial velocities of their companions is 87 km s?1, yielding the median orbital mass estimate of about 5 × 1011M⊙. Excluding six probable non-isolated pairs, we obtained a typical halo-mass-to-stellar-mass of UF galaxies of about 30, what is almost the same one as in the principal spiral galaxies, like M31 and M81 in the nearest groups. We also note that ultra-flat galaxies look two times less “dusty” than other spirals of the same luminosity.  相似文献   

6.
We have estimated the dark matter content in galaxy pairs and triplets selected from SDSS DR5 by a higher-order Voronoi tesseleration method. Specifically, the median mass-to-light ratios M vir/L are 12 M ⊙/L ⊙ for isolated pairs, 44 M ⊙/L ⊙ for isolated triplets, and 7 (8) M ⊙/L ⊙ for compact pairs (triplets) with a characteristic distance between the galaxies of R < 50 (100) kpc. We show that the less isolated a system, the larger its mass-to-light ratio. This suggests that galaxy groups in a denser environment have a higher velocity dispersion.  相似文献   

7.
Based on data from the Two-Micrometer All-Sky Survey (2MASS), we analyzed the infrared properties of 451 Local-Volume galaxies at distances D ≤ 10 Mpc. We determined the K-band luminosity function of the galaxies in the range of absolute magnitudes from ?25m to ?11m. The local luminosity density within 8 Mpc is 6.8 × 108L⊙ Mpc?3, a factor of 1.5 ± 0.1 higher than the global mean K-band luminosity density. We determined the ratios of the virial mass to the K-band luminosity for nearby groups and clusters of galaxies. In the luminosity range from 5 × 1010 to 2 × 1013L⊙, the dependence log(M/LK) ∝ (0.27 ± 0.03) log LK with a dispersion of ～0.1 comparable to the measurement errors of the masses and luminosities of the systems of galaxies holds for the groups and clusters of galaxies. The ensemble-averaged ratio, 〈M/LK〉 ? (20–25) M⊙/L⊙, was found to be much smaller than the expected global ratio, (80–90)M⊙/L⊙, in the standard model with Ωm = 0.27. This discrepancy can be eliminated if the bulk of the dark matter in the Universe is not associated with galaxies and their systems.  相似文献   

8.
We study the variations of the properties of groups of galaxies with dynamical masses of 1013 M ⊙<M 200<1014 M ⊙, represented by two samples: one has redshifts of z < 0.027 and is located in the vicinity of the Coma cluster, the other has z > 0.027, and is located in the regions of the following superclusters of galaxies: Hercules, Leo, Bootes, Ursa Major, and Corona Borealis. Using the archived data of the SDSS and 2MASX catalogs, we determined the concentration of galaxies in the systems by measuring it as the inner density of the group within the distance of the fifth closest galaxy from the center brighter than M K = ?23. m 3. We also measured the magnitude gap between the first and the fourth brightest galaxies ΔM 14 located within one half of the selected radius R 200, the fraction of early-type galaxies, and the ratio of bright dwarf galaxies (Mr = [?18. m 5,?16. m 5]) to giant galaxies (M r < ?18. m 5) (DGR) within the radius R 200. The main aim of the investigation is to find among these characteristics the ones that reflect the evolution of groups of galaxies.We determined that the ratio of bright dwarf galaxies to early-type giant galaxies on the red sequence depends only on the x-ray luminosity: the DGR increases with luminosity. The fraction of early-type galaxies in the considered systems is equal, on average, to 0.65 ± 0.01, and varies significantly for galaxies with σ200 < 300 kms?1. Based on the luminosity of the brightest galaxy, the magnitude gap between the first and the fourth brightest galaxies in the groups, and on model computations of these parameters, we selected four fossil group candidates: AWM4, NGC0533, NGC0741, and NGC6098 (where the brightest galaxy is a double).We observe no increase in the number of faint galaxies (the α parameter of the Schechter function is less than 1) in our composite luminosity function (LF) for galaxy systems with z < 0.027 in the M K = [?26m,?21. m 5] range, whereas earlier we obtained α > 1 for the LF of the Hercules and Leo superclusters of galaxies.  相似文献   

9.
We analyze the statistical properties of normal galaxies to be detected in the all-sky survey by the eROSITA X-ray telescope of the Spectrum-X-Gamma observatory. With the current configuration and parameters of the eROSITA telescope, the sensitivity of a 4-year-long all-sky survey will be ≈10?14 erg s?1 in the 0.5–2 keV band. This will allow ～(1.5–2) × 104 normal galaxies with approximately the same contribution of star-forming and elliptical galaxies to be detected. All galaxies of the X-ray survey are expected to enter into the existing far-infrared (IRAS) or near-infrared (2MASS) catalogs; the sample of star-forming galaxies will be approximately equivalent in sensitivity to the sample of star-forming galaxies in the IRAS catalog of infrared sources. Thus, a large homogeneous sample of normal galaxies with measured X-ray, near-infrared, and far-infrared fluxes will be formed. About 90% of the galaxies in the survey are located within ～200–400 Mpc. A typical (most probable) galaxy will have a luminosity log L X ～ 40.5–41.0, will be located at a distance of ～70–90 Mpc, and will be either a star-forming galaxy with a star formation rate of ～20M ⊙ yr?1 whose X-ray emission is produced by ultraluminous X-ray sources (ULXs) or an elliptical galaxy with amass log M * ～ 11.3 emitting through to a hot interstellar gas. The galaxies within 35 Mpc will collectively contain ～102 ULXs with luminosities log L X > 40, ～80% of whichwill be the only luminous source in the galaxy. Thus, although the angular resolution of the eROSITA telescope is too low for the luminosity function of compact sources in galaxies to be studied in detail, the survey data will allow one to investigate its bright end and, possibly, to impose constraints on the maximum luminosity of ULXs.  相似文献   

10.
We present the results of our photometric (BV R) and spectroscopic CCD observations of NGC 304 and NGC 7625, candidate polar-ring galaxies, performed with the 6-m Special Astrophysical Observatory telescope. For NGC 304, such a study has been carried out for the first time. We have obtained basic integrated characteristics of the galaxies and determined their morphological types (S0 for NGC 304 and Sa for NGC 7625). The absolute magnitudes of the galaxies, M B = ?20m.81 for NGC 304 and M B = ?19m.34 for NGC7625, are indicative of their fairly high luminosities. The disk and bulge parameters have been determined forNGC 304 (µ0 = 20m.60, h = 3.86 kpc, µ e = 21m.59, r e = 1.26 kpc in the B band); these correspond to the parameters of S0-type objects. The rotation velocity for NGC 304 (200 km s?1) reaches its maximum at a galactocentric distance of 3.1 kpc, which yields a mass estimate for the galaxy of 2.8 × 1010 \(\mathcal{M}_ \odot \). The observed photometric features at the center of NGC 304 indicate that it may have an inner ring structure, although we have failed to confirm the existence of two kinematic systems based on our spectroscopic observations. In NGC 7625, the disk makes a dominant contribution to the total brightness. The derived integrated color indices (B-V = 0m.81 and V-R = 0m.61) agree with previous determinations of other authors. We have estimated the учештсешщт in the inner galactic regions. In the outer regions, we have detected structures with bluer colors (B-V = 0m.60), which may be indicative of a polar ring with a minor stellar component.  相似文献   

11.
In this paper we study the relations between the main characteristics of groups and clusters of galaxies using the archival data of the SDSS and 2MASX catalogs. We have developed and implemented a new method of determining the size of galaxy systems and their effective radius which contains half of the galaxies and not half the luminosity, since the luminosity of the brightest galaxy in a group can account for over 50% of the total luminosity of the group. The derived parameters (log LK, logRe, and log σ200) for 94 systems of galaxies (0.0038 < z < 0.09) determine the Fundamental Plane (FP), which, with a scatter of 0.15, is similar in form to the FP of galaxy clusters obtained by Schaeffer et al. (1993) and D’Onofrio et al. (2013) with other methods and for different bands. We show that the FP in the near-infrared region (NIR) for 94 galaxy systems has the form of LK ∝ \(R_e^{0.70 \pm {{0.13}_\sigma }1.34 \pm 0.13}\), whereas in x-rays it has the form of—LX ∝ \(R_e^{1.15 \pm {{0.39}_\sigma }2.56 \pm 0.40}\). The form of the FP for groups and clusters is consistent with the FP for early-type galaxies determined in the same way. The form of the FP for galaxy systems deviates from the shape that one would expect from virial predictions. Adding the mass-to-light ratio as a fourth independent parameter has little effect on this deviation, but decreases the scatter of the FP for a sample of rich galaxy clusters by 12%.  相似文献   

12.
Available velocity dispersion estimates for the old stellar population of galactic disks at galactocentric distances r?2L (where L is the photometric radial scale length of the disk) are used to determine the threshold local surface density of disks that are stable against gravitational perturbations. The mass of the disk Md calculated under the assumption of its marginal stability is compared with the total mass Mt and luminosity L B of the galaxy within r=4L. We corroborate the conclusion that a substantial fraction of the mass in galaxies is probably located in their dark halos. The ratio of the radial velocity dispersion to the circular velocity increases along the sequence of galactic color indices and decreases from the early to late morphological types. For most of the galaxies with large color indices (B–V)0>0.75, which mainly belong to the S0 type, the velocity dispersion exceeds significantly the threshold value required for the disk to be stable. The reverse situation is true for spiral galaxies: the ratios Md/LB for these agree well with those expected for evolving stellar systems with the observed color indices. This suggests that the disks of spiral galaxies underwent no significant dynamical heating after they reached a quasi-equilibrium stable state.  相似文献   

13.
We have identified 22 galaxies with photometric redshifts zph=5–7 in the northern and southern Hubble Space Telescope deep fields. An analysis of the images of these objects shows that they are asymmetric and very compact (～1 kpc) structures with high surface brightness and absolute magnitudes of MB≈?20m. The average spectral energy distribution for these galaxies agrees with the distributions for galaxies with active star formation. The star formation rate in galaxies with zph=5–7 was estimated from their luminosity at λ=1500 Å to be ~30 M⊙yr?1. The spatial density of these objects is close to the current spatial density of bright galaxies. All the above properties of the distant galaxies considered are very similar to those of the so-called Lyman break galaxies (LBGs) with z ～ 3–4. The similarity between the objects considered and LBGs suggests that at z ～6, we observe the progenitors of present-day galaxies that form duringmergers of protogalactic objects and that undergo intense starbursts.  相似文献   

14.
The structure of the A1035 cluster of galaxies (10h32m + 40°13′, cz ～ 22000 kms?1), which exhibits a bimodal distribution of galaxy radial velocities (ΔV ≈ 3000 kms?1), is analyzed using three methods of determining the relative distances to clusters from early-type galaxies: the Kormendy relation corrected for the dependence of residuals on galaxy magnitude, the photometric plane, and the fundamental plane. We use the data obtained with the l-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences and SDSS (DR5) data to show that A1035 consists of two gravitationally unbound independent clusters. These clusters with the velocity dispersions of 566 km s?1 and 610 km s?1 and masses within R 200 equal to 2.7 · 1014 and 3.5 · 1014 M ⊙, respectively, obey the Hubble law.  相似文献   

15.
We consider the relationship between the total HI mass in late-type galaxies and the kinematic properties of their disks. The mass MHI for galaxies with a wide variety of properties, from dwarf dIrr galaxies with active star formation to giant low-brightness galaxies, is shown to correlate with the product VcR0 (Vc is the rotational velocity, and R0 is the radial photometric disks cale length), which characterizes the specific angular momentum of the disk. This correlation, along with the decrease in the relative mass of the gas in a galaxy with increasing Vc, can be explained in terms of the previous assumption that the gas density in the disks of most galaxies is maintained at a level close to the threshold (marginal) stability of a gaseous layer to local gravitational perturbations. In this case, the regulation mechanism of the star formation rate associated with the growth of local gravitational instability in the gaseous layer must play a crucial role in the evolution of the gas content in the galactic disk.  相似文献   

16.
We present the results of our hydrodynamic calculations of radial pulsations in helium stars with masses 1 M⊙ ≤ M ≤ 10 M⊙, luminosity-to-mass ratios 1 × 103L⊙/M⊙ ≤ L/M ≤ 2 × 104L⊙/M⊙, and effective temperatures 2 × 104 K ≤ Teff ≤ 105 K for mass fractions of helium Y=0.98 and heavy elements Z=0.02. We show that the lower boundary of the pulsation-instability region corresponds to L/M ～ 103L⊙/M⊙ and that the instability region for L/M ? 5 × 103L⊙/M⊙ is bounded by effective temperatures Teff ? 3 × 104 K. As the luminosity rises, the instability boundary moves into the left part of the Hertzsprung-Russell diagram and radial pulsations can arise in stars with effective temperatures Teff ? 105 K at L/M ? 7 × 103L⊙/M⊙. The velocity amplitude for the outer boundary of the hydrodynamic model increases with L/M and lies within the range 200 ? ΔU ? 700 km s?1 for the models under consideration. The periodic shock waves that accompany radial pulsations cause a significant change of the gas-density distribution in the stellar atmosphere, which is described by a dynamic scale height comparable to the stellar radius. The dynamic instability boundary that corresponds to the separation of the outer stellar atmospheric layers at a superparabolic velocity is roughly determined by a luminosity-to-mass ratio L/M ～ 3 × 104L⊙/M⊙.  相似文献   

17.
The stellar population of the blue compact dwarf galaxy SBS 1415+437 is investigated using the archive database of the Hubble space telescope. The color index-magnitude diagram for stars reaches a magnitude of 29 m in the V and I bands. It comprises young main-sequence stars, blue and red supergiants, and the old population of red giant branch and asymptotic giant branch. The tip of the red giant branch αTRGB) was used to calculate the distance modulus, which turned out to be m ? M = 30.65 ± 0.08 m . The corresponding distance to the galaxy is D = 13.5 ± 1.0 Mpc. The youngest stars are distributed irregularly near the bright H II region in the southwest part of SBS 1415+437. The old population occupies a larger area, it is distributed more evenly and forms the galactic halo. The spatial distribution of young stars shows that the star formation in the galaxy spread in the direction from northeast to southwest over the last 5 × 107 yr with an average rate of 60 km/s. The TRGB of SBS 1415+437 was found to be appreciably shifted to the blue range: (V ? I) TRGB ≈ 1.30. The galaxy age turns out to be not smaller than the age of Galactic globular clusters (about 1010 yr), provided that the galaxy originally had a very low metallicity (our photometric estimate is [Fe/H] = ?2.4). If the metallicity of SBS 1415+437 changed almost not at all in the course of evolution and was equal to [Fe/H] = ?1.3 (as estimated from the emission lines of ionized gas), the galaxy age is no more than 2 × 109 yr.  相似文献   

18.
We present some results of the photometric analysis of the stellar population of the irregular dwarf galaxy KK 230 on the basis of the archive database of the Hubble space telescope. The color index-magnitude diagram for KK 230 gets to magnitude 27 m in the V and I bands, and it comprises stellar populations of various ages. The age of the youngest main-sequence stars is 3.2 × 107 yr. These stars are distributed along the north-south direction in the picture plane, and this fact can be linked to the observed kinematics of the neutral gas in the galaxy. Older blue and red supergiants are no less than 1.6 × 108 years old, and such an age implies that the star formation was episodic over the last several hundreds of millions of years. As judged from the position of the tip of the red giant branch, the distance modulus for KK 230 is m ? M = 26.5 m . The corresponding distance is D = 2 Mpc. Based on the average absolute magnitude M I,RC and color index (V ? I)I,RC of the red clump, we conclude that the majority of KK 230 stars have an age of no more than (2–3) × 109 yr, their metallicity being Z ≈ 0.0004.  相似文献   

19.
The present paper is devoted to the construction of a catalog of isolated galaxy pairs from the Uppsala Galaxy Catalog (UGC), using accurate radial velocities. The UGC lists 12 921 galaxies to δ > ?2?30′ and is complete to an apparent diameter of 1′. The criteria used to define the isolated galaxy pairs are based on velocity, interdistance, reciprocity and isolation information. A peculiar investigation has allowed to gather very accurate radial velocities for pair members, from high quality HI and optical measurements (median uncertainty on velocity differences 10 kms?1). Our final catalog contains 1005 galaxy pairs with ρ > 2.5, of which 509 have ρ > 5 (50% of the pairs, i.e. 8%of the UGC galaxies) and 273 are highly isolated with ρ > 10 (27% of the pairs, i.e. 4% of the UGC galaxies). Some global properties of the pair catalog are given.  相似文献   

20.
The present paper is devoted to the construction of a catalog of isolated galaxy pairs extracted from the HyperLEDA extragalactic database. The radial velocities of the galaxies in the pairs are in the range [3000, 16000] km s?1. In order to get an unbiased pair catalog as complete as possible, we have limited the absolute magnitude of the galaxies to M ≤ ?18.5. The criteria used to define the isolated galaxy pairs are the following: 1) velocity criterion: radial velocity difference between the pair members ΔV < 500 kms?1; 2) interdistance criterion: projected distance between the members rp < 1 Mpc; 3) reciprocity criterion: each member is the closest galaxy to the other one, which excludes multiplets; 4) isolation criterion: we define a pair as isolated if the ratio ρ = r3/rp of the projected distance of the pair to its closest galaxy (this one having a velocity difference lower than 500 km s?1 with respect to the pair) and the members projected interdistance rp is larger than 2.5.We have searched for these closest galaxies first in HyperLEDA M-limited source catalog, then in the full one.We have managed not to suppress the small number of pairs having close-by but faint dwarf galaxy companions. The galaxy pair catalog lists the value of ρ for each isolated pair. This method allows the user of the catalog to select any isolation level (beyond the chosen limit ρ > 2.5). Our final catalog contains 13 114 galaxy pairs, of which 57% are fairly isolated withρ > 5, and 30% are highly isolated with ρ ≥ 10.  相似文献   

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