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
We report the results of a statistical analysis of the space distribution of galaxies of the 2MRS catalog, which contains redshifts of 43533 galaxies of the 2MASS all-sky IR survey. Because of the unique features of the 2MRS survey, such as its 90% sky coverage, galaxy selection in the IR, the complete incorporation of the old stellar population of galaxies, weakness of the dust extinction effects, and the smallness of the k- and e-corrections allowed us to determine the statistical properties of the global distribution of galaxies in the Local Universe. We took into account the main methodological factors that distort the theoretically expected relations compared to those actually observed. We construct the radial galaxy number counts N(R), SL(R, r) statistics, and the complete correlation function (conditional density) Γ(r) for volume-limited (VL) galaxy samples. The observed conditional density Γ(r) in the redshift space is independent of the luminosity of galaxies and has the form of a power-law function with exponent γ ≈ 1.0 over a large range scale-length spanning from 0.1 to 100 Mpc. We compare the statistical properties of the space distribution of galaxies of the 2MRS catalog with the corresponding properties of simulated catalogs: stochastic fractal distributions and galaxies of the Millennium catalog. 相似文献
A galaxy that is a good candidate for polar-ring galaxies has been detected in the Hubble Ultra Deep Field (HUDF). The galaxy HUDF 1619 (V ≈ 25m, z ～ 1) is the most distant object of this type known to date. A large-scale structure crosses the highly warped disk of the main galaxy seen almost edge-on at an angle of about 70°. The luminosity of this structure (the possible polar ring) reaches ～1/3 of the luminosity of the central galaxy. A strong absorption lane is seen in the region where this structure is projected onto the disk of the central object. There are two galaxies of comparable luminosity adjacent to HUDF 1619 (in projection). One of them may be the donor galaxy the interaction with which gave rise to the ring structure. 相似文献
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
We study the variations of the properties of groups of galaxies with dynamical masses of 1013M⊙<M200<1014M⊙, 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 MK = ?23.m 3. We also measured the magnitude gap between the first and the fourth brightest galaxies ΔM14 located within one half of the selected radius R200, the fraction of early-type galaxies, and the ratio of bright dwarf galaxies (Mr = [?18.m 5,?16.m 5]) to giant galaxies (Mr < ?18.m 5) (DGR) within the radius R200. 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 MK = [?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
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
For a sample of 8156 emission-line galaxies from the Sloan Digital Sky Survey Data Release 4 (SDSS DR4), we have determined the current star formation rates (SFR) from three parameters: the Hα luminosity of H II regions corrected for the aperture and interstellar extinction (N = 7006 galaxies), the far-infrared luminosity (IRAS data, N = 350), and the monochromatic luminosity in the radio continuum at ν = 1.4 GHz (NVSS data, N = 475). A Salpeter initial mass function with the range of stellar masses 0.1–100 M⊙ was assumed in the SFRFIR calculations. In calculating SFR1.4, we assumed that the fraction of the thermal emission in the total radio continuum emission of the galaxy at 1.4 GHz was 10%. An upper limit for the starburst age has been determined for galaxies with known abundances of heavy elements. We compare our results with those of similar studies for isolated and Markarian H II galaxies. 相似文献
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 LB 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
Based on archived images obtained with the Hubble Space Telescope, stellar photometry for 105 irregular galaxies has been conducted. We have shown the red supergiant and giant branches in the obtained Hertzsprung-Russel diagrams. Using the TRGB method, distances to galaxies and metallicity of red giants have been determined. The color index (V ? I) of the supergiant branch at the luminosity level MI = ?7 was chosen as the metallicity index of red supergiants. For the galaxies under study, the diagrams have been built, in which the correlation can be seen between the luminosity of galaxies (MB) and metallicity of red giants and supergiants. The main source of variance of the results in the obtained diagrams is, in our opinion, uncertainty inmeasurements of galaxy luminosities and star-forming outburst. The relation between metallicity of young and old stars shows that main enrichment of galaxies with metals has taken place in the remote past. Deviations of some galaxies in the obtained relation can possibly be explained with the fall of the intergalactic gas on them, although, this inconsiderably affects metallicities of the stellar content. 相似文献
We report a catalog of 168 galaxy triplets with line-of-sight velocities VLG < 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 × 1011M⊙ 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
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 LX ～ 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 LX > 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
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
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 × 1011M⊙. The dynamical mass of M 101 calculated on the basis of the four galaxies constituting the group is 6.2 × 1011M⊙. The mass-to-light ratio for this mass is M/L = 18 (at the adopted luminosity of M 101, MB = ?20.8). 相似文献
Using the method of searching for arbitrary shaped voids in the distribution of volume-limited samples of galaxies from the DR5 SDSS survey, we have identified voids and investigated their characteristics and the change in these characteristics with decreasing Mlim (from ?19.7 to ?21.2, H0 = 100 km s?1 Mpc?1)—the upper limit on the absolute magnitude of the galaxies involved in the construction of voids. The total volume of the 50 largest voids increases with decreasing Mlim with a break near M* = ?20.44—the characteristic value of the luminosity function for SDSS galaxies. The mean overdensity in voids increases with decreasing Mlim also with a weak break near M*. The exponent of the dependence of the volume of a void on its rank increases significantly with decreasing Mlim starting from Mlim ～ ?20.4 in the characteristic range of volumes, which reflects the tendency for greater clustering of brighter galaxies. The averaged profile of the galaxy overdensity in voids has a similar pattern almost at all Mlim. The galaxies mostly tend to gravitate toward the void boundaries and to avoid the central void regions; the overdensity profile is flat in the intermediate range of distances from the void boundaries. The axial ratios of the ellipsoids equivalent to the voids are, on average, retained with changing Mlim and correspond to elongated and nonoblate void shapes, but some of the voids can change their shape significantly. The directions of the greatest void elongations change chaotically and are distributed randomly at a given Mlim. The void centers show correlations reflecting the correlations of the galaxy distribution on scales (35–70)h?1 Mpc. The galaxy distribution in the identified voids is nonrandom—groups and filaments can be identified. We have compared the properties of the galaxies in voids (in our case, the voids are determined by the galaxies with absolute magnitudes Mabs < Mlim = ?20.44, except for the isolated galaxies) and galaxies in structures identified using the minimum spanning tree. A bimodal color distribution of the galaxies in voids has been obtained. A noticeable difference is observed in the mean color indices and star formation rates per unit stellar mass of the galaxies in dense regions (structures)—as expected, the galaxies in voids are, on average, bluer and have higher log (SFR/Mstar). These tendencies become stronger toward the central void regions. 相似文献
Low-mass galaxies are known to have played the crucial role in the hydrogen reionization in the Universe. In this paper we investigate the contribution of soft x-ray radiation (E ~ 0.1–1 keV) from dwarf galaxies to hydrogen ionization during the initial reionization stages. The only possible sources of this radiation in the process of star formation in dwarf galaxies during the epochs preceding the hydrogen reionization epoch are hot intermediate-mass stars (M ~ 5–8 M⊙) that entered the asymptotic giant branch (AGB) stage and massive x-ray binaries. We analyze the evolution of the intergalactic gas in the neighborhood of a dwarf galaxy with a total mass of 6 × 108M⊙ formed at the redshift of z ~ 15 and having constant star-formation rate of 0.01–0.1 M⊙ yr?1 over a starburst with a duration of up to 100 Myr. We show that the radiation from AGB stars heats intergalactic gas to above 100 K and ensures its ionization xe ? 0.03 within about 4–10 kpc from the galaxy in the case of a star-formation rate of star formation 0.03–0.1 M⊙ yr?1, and that after the end of the starburst this region remains quasi-stationary over the following 200–300 Myr, i.e., until z ~ 7.5. Formation of x-ray binaries form in dwarf galaxies at z ~ 15 results in a 2–3 and 5–6 times greater size of the ionized and heated region compared to the case where ionization is produced by AGB stars exclusively, if computed with the “x-ray luminosity–star-formation rate” dependence (LX ~ fXSFR) factor fX = 0.1 and fX ~ 1, respectively. For fX ? 0.03 the effect of x-ray binaries is smaller that that of AGB star population. Lyα emission, heating, and ionization of the intergalactic gas in the neighborhood of dwarf galaxies result in the excitation of the 21 cm HI line. We found that during the period of the starburst end at z ~11.5–12.5 the brightness temperature in the neighborhood of galaxies is 15–25 mK and the region where the brightness temperature remains close to its maximum has a size of about 12–30 kpc. Hence the epoch of the starburst end is most favorable for 21 cm HI line observations of dwarf galaxies, because at that time the size of the region of maximum brightness temperature is the greatest over the entire evolution of the dwarf galaxy. In the case of the sizes corresponding to almost 0.’1 for z ~ 12 regions with maximum emission can be detected with the Square Kilometre Array, which is currently under construction. 相似文献
We report the results of the study of red-sequence (RS) galaxies in 47 galaxy clusters (0.023 < z < 0.047) located in different environments: in the superclusters Hercules and Leo, and in the field, based on the SDSS catalog data. In the
interval, the number of bright RS dwarf galaxies in galaxy clusters increaseswith the X-ray luminosity of the cluster as logN ∝ logX0.64. The dwarf-to-giant ratio (DGR) does not depend on the surroundings, mass, or richness of the cluster. This ratio is seen to increase for galaxy clusters with log LX > 43.5 erg/s or σ > 520 km/s. The compositeDGR of galaxy clusters, determined both from the membership in different structures and the X-ray luminosity along the radius R200, is minimum in the central regions of the clusters (about 0.6 ± 0.06), reaches a maximum within 0.3–0.9R200 (about 0.9 ± 0.10), and decreases approximately to 0.7 ± 0.03 upon reaching the radius 1.4 R200.
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
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
We analyze the structure of the cluster of galaxies Abell 1775 (α = 13h42m, δ = +26°22′, cz ≈ 21000 km/s), which exhibits a bimodal distribution of radial velocities of the containing galaxies. The difference of the subcluster radial velocities is ΔV ≈ 2900 km/s. We use the results of our photometric observations made with the 1-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences and the spectroscopic and photometric data from the SDSS DR6 catalog to determine independent distances to the subclusters via three different methods: the Kormendy relation, photometric plane, and fundamental plane. We find that the A1775 cluster consists of two independent clusters, A1775A (cz = 19664 km/s) and A1775B (cz = 22576 km/s), each located at its own Hubble distance and having small peculiar velocities. Given the velocity dispersions of 324 km/s and 581 km/s and the dynamic masses within the R200 radius equal to 0.6 × 1014 and 3.3 × 1014 M⊙, the A1775A and A1775B clusters have the K-band luminosity-to-mass ratios of 29 and 61, respectively. A radio galaxy with an extended tail belongs to the A1775B cluster. 相似文献
We present the HI observations of 94 flat spiral galaxies from RFGC (Revised Flat Galaxy Catalog) and 14 galaxies from 2MFGC (the 2MASS selected Flat Galaxy Catalog) performed with the 100-m radio telescope in Effelsberg (Germany). HI fluxes, heliocentric radial velocities, and HI line widths are given for 65 detected galaxies. We present a mosaic of HI profiles. We calculated some of the global parameters of the galaxies and analyzed the linear correlations between them. The ratios of the total (indicative) masses of the galaxies to their luminosities lie within the range 0.4–8.2 with a mean of 3.8 (M⊙/L⊙), and the mean mass fraction of neutral hydrogen is 13%. Upper limits are given for the radio fluxes from 43 undetected galaxies. 相似文献
