Nearby galaxies. IV. The global Hubble parameter and the dispersion of the Hubble relation

Using a spherically symmetric model of the Virgo flow the global Hubble parameter has been estimated from the observed radial velocities and the photometrically measured distances of nearby galaxies. Adopting the observed recession velocity of the Virgo Cluster to about 1000 km s⁻¹ and the infall velocity of the Local Group to 350 km s⁻¹ the global Hubble constant results to 73 ± 10 km s⁻¹ Mpc⁻¹. This value corresponds with the distance of the Virgo Cluster of 18 ± 2 Mpc. The cosmic dispersion of the galaxies around the Hubble relation is of order of 35 km s⁻¹.     

The cosmic distance scale

Summary The status of the cosmic distance scale problem in early 1989 is reviewed. Internally consistent distances to Local Group galaxies are given in Tables 5 and 6. Within the Local Group the distance scale is found to be 11±5% smaller than that previously adopted by Sandage and Tammann. Distances to nearby galaxies are used as stepping stones to the Virgo cluster. The interpretation of the Tully-Fisher observations of Virgo spirals is found to be ambiguous because it is not yet clear which spirals are cluster members and which are background objects. Distance estimates of the Virgo cluster obtained by different techniques are listed in Table 11. The distance modulus of the Virgo cluster is found to be 31.5±0.2, corresponding to a distance of 20±2 Mpc. The elliptical galaxies in the core of the Virgo cluster haveV ₀=1200±46 kms^–1, which corresponds toV _LG=1082±48 km s^–1. With an infall velocity of 250±50 km s^–1 this yields a cosmological redshiftV=1332±69 km s^–1, from which a Hubble parameter H₀=67±8 km s^–1 Mpc^–1 is obtained. Space Telescope observations of distant Cepheids, Tully-Fisher observations of spirals in the Hercules eluster, and interference filter observations of Virgo planetary nebulae in the light of [O_III], should soon result in a major improvement in the accuracy with which H₀ is known.     

The Ursa Major supercluster of galaxies: II. The structure and peculiar velocities

Kormendy’s relation (μ_e-logR _e) is used to investigate the structure of the compact Ursa Major supercluster of galaxies (11^h30^m+55°, cz=18 000 km s^?1); this relation allows the distances of early-type galaxies to be estimated. The relative distances of 13 clusters in the supercluster and their peculiar velocities are determined with a mean statistical accuracy of 6%. In general, the supercluster obeys the Hubble relation between radial velocity and distance. However, there is reason to suggest that the supercluster consists of two subsystems with mean radial velocities of 16 200 and 19 700 km s^?1. For a velocity dispersion in the subsystems of ～1100 km s^?1, the fact that each of them is gravitationally bound is not ruled out.     

Blueshifted galaxies in the virgo cluster

We examine a sample of 65 galaxies in the Virgo cluster with negative radial velocities relative to the Local Group. Some features of this sample are pointed out. All of these objects are positioned compactly within a virial zone of radius 6o in the cluster, but their centroid is displaced relative to the dynamic center of the cluster, M87, by 1o.1 to the northwest. The dwarf galaxies in this sample are clumped on a scale of ∼10' (50 kpc). The observed asymmetry in the distribution of the blueshifted galaxies may be caused by infall of a group of galaxies around M86 onto the main body of the cluster. We offer another attempt to explain this phenomenon, assuming a mutual tangential velocity of ∼300 km/s^-1 between the Local Group and the Virgo cluster owing to their being repelled from the local cosmological void.     

Nearby groups of galaxies in the Hercules–Bootes constellations

We consider a sample of 412 galaxies with radial velocities V _LG < 2500 kms^?1 situated in the sky region of RA = 13_. ^m 0–19_. ^m 0, Dec = +10?...+40? between the Local Void and the Supergalactic plane. One hundred and eighty-one of them have individual distance estimates. Peculiar velocities of the galaxies as a function of Supergalactic latitude SGB show signs of Virgocentric infall at SGB < 10? and motion from the Local Void at SGB > 60?. A half of the Hercules–Bootes galaxies belong to 17 groups and 29 pairs, with the richest group around NGC5353. A typical group is characterized by the velocity dispersion of 67 km s^?1, the harmonic radius of 182 kpc, the stellar mass of 4.3 × 10¹⁰ M _⊙ and the virialto- stellar mass ratio of 32. The binary galaxies have the mean radial velocity difference of 37 kms^?1, the projected separation of 96 kpc, the mean integral stellar mass of 2.6×109M _⊙ and the mean virial-to-stellar mass ratio of about 8. The total dark-matter-to-stellar mass ratio in the considered sky region amounts to 37 being almost the same as that in the Local Volume.     

Peculiar motions of galaxy clusters in the regions of the Corona Borealis,Bootes, Z 5029/A 1424, A 1190, A 1750/A 1809 superclusters of galaxies

We present results of the study of peculiar motions of 57 clusters and groups of galaxies in the regions of the Corona Borealis (CrB), Bootes (Boo), Z5029/A1424, A1190, A1750/A1809 superclusters of galaxies and the galaxy clusters located beyond massive structures (0.05 < z < 0.10). Using the SDSS (Data Release 8) data, a sample of early-type galaxies was compiled in the systems under study, their fundamental planes were built, and relative distances and peculiar velocities were determined. Within the galaxy superclusters, significant peculiar motions along the line of sight are observed with rms deviations of 652 ± 50 kms^?1—in CrB, 757 ± 70 kms^?1—in Boo. In the most massive A2065 cluster in the CrB supercluster, no peculiar velocity was found. Peculiar motions of the other galaxy clusters can be caused by their gravitational interaction both with A2065 and with the A2142 supercluster. It has been found that there are two superclusters projected onto each other in the region of the Bootes supercluster with a radial velocity difference of about 4000 kms^?1. In the Z 5029/A1424 supercluster near the rich Z5029 cluster, the most considerable peculiar motions with a rms deviations of 1366 ± 170 kms^?1 are observed. The rms deviations of peculiar velocities of 20 clusters that do not belong to large-scale structures is equal to 0 ± 20 kms^?1. The whole sample of the clusters under study has the mean peculiar velocity equal to 83 ± 130 kms^?1 relative to the cosmic microwave background.     

Normal galaxies in the all-sky survey by the eROSITA X-ray telescope of the Spectrum-X-Gamma observatory

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.     

The structure of clusters with bimodal distributions of galaxy radial velocities,I. A1035

The structure of the A1035 cluster of galaxies (10^h32^m + 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.     

A Catalog of Isolated Galaxy Pairs Limited to Absolute Magnitude -18.5 Drawn from HyperLEDA Database

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 r_p < 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/r_p 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 r_p 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.     

Analysis of the properties of clusters of galaxies in the region of the Ursa Major supercluster

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.     

On the detectability of turbulence and bulk flows in X-ray clusters

Coolingflows, cluster mergers, and the motions of galaxies through cluster gas with supersonic and sonic velocities must lead to large scale motions of the intracluster medium (ICM). A high-resolution numerical simulation of X-ray cluster formation by Norman and Bryan (1999) predicts cluster-wide turbulence with ν_turb ≈300–600 km s^?1 and eddy scales l_outer ≈100–500 kpc, the larger numbers being characteristic of turbulence near the virial radius, while the smaller numbers pertain to the core. The simulation also predicts the existence of ordered bulk flows in the core with v≈400 km s^?1 on scales of several hundred kpc. In this paper, we consider the observability of such fluid motions via the distortions they induce in the CMB via the kinematic SZ effect, as well as via Doppler broadening and shifting of metal lines in the X-ray spectrum. We estimate |ΔT/T|_kinematic?6—at or below current limits of detectability. However, we find that an energy resolution of a few eV is sufficient to detect several Doppler shifted components in the 6.7 keV Fe line in the cluster core.     

Ultra-flat galaxies selected from RFGC catalog. II. Orbital estimates of halo masses

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 R_p < 250 kpc. Wherein, the wider area around the UF galaxy within R_p < 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.     

Local Field of Galaxy Velocities

A sample of 145 galaxies having radial velocities relative to the centroid of the Local Group V _LG < 500 km/sec and estimated photometric distances D < 8 Mpc is considered. The field of peculiar velocities of these galaxies is estimated using the tensor of the local value of the Hubble constant H _ij , with principal values of 81:62:48 in km/sec·Mpc, which have a standard error of 4 km/sec·Mpc. The minor axis of the Hubble ellipsoid is oriented almost along the polar axis of the Local Supercluster, while the major axis forms an angle = (29 ± 5)° with the direction toward the center of the Virgo Cluster. Such a configuration of the peculiar-velocity field shows unsatisfactory agreement with the model of a spherically symmetric flow of galaxies toward the Virgo Cluster. Rotation of the Local Supercluster may be one reason for this difference. The peculiar velocities of galaxies within a volume with D < 8 Mpc are characterized by a dispersion _V = 74 km/sec, a considerable part of which is due to the virial motions of galaxies in groups and to distance errors. For field galaxies, located in a layer of 1 < D < 3 Mpc around the Local Group, the radial-velocity dispersion does not exceed 25 km/sec. The velocity—distance relation, constructed from the 20 closest galaxies around the Local Group with D < 3 Mpc and with errors (D) < 0.2 Mpc, exhibits the expected effect of gravitational deceleration. Using the estimate of R ₀ = (0.96 ± 0.05) Mpc for the observed radius of the zero-velocity sphere, we determined the total mass of the Local Group to be (1.2 ± 0.2)·10¹² M , which agrees well with the sum of the virial masses of the subgroups of galaxies around the Local Group and M31. The ratio of the Local Group's total mass (within R ₀) to its luminosity is M/L = (23 ± 4) M /L , which does not require the existence of supermassive dark halos around our Galaxy and M31.     

Peculiar motions of galaxy clusters and groups in the Hercules and Leo supercluster regions

We present the results of our study of the peculiar motions for 41 galaxy clusters and groups in the regions of the Hercules and Leo superclusters (0.027 < z < 0.045). For this purpose, based on SDSS (Data Release 8) data, we compiled a sample of early-type galaxies in the investigated clusters and groups, constructed their fundamental planes (FPs), and determined independent distances and peculiar velocities. The Hubble law between the radial velocities galaxy clusters and the distances derived from the FPs holds for the rich Hercules supercluster as a whole. At the same time, however, significant peculiar motions along the line of sight with rms deviations of 736 ± 50 and 584 ± 50 km s^?1 are observed within this supercluster and in its immediate neighborhood. In the poor Leo supercluster, the rms deviation is also large, 625 ± 70 km s^?1. Its Hubble diagram exhibits the approach of galaxy clusters and groups along the line of sight relative to the most massive cluster A1185. In the immediate neighborhood of the Leo supercluster (virtually in its field), the rms deviation of the peculiar velocities is minimal, 287 ± 60 km s^?1.     

Analysis of the clustering of 2dFGRS galaxies using the method of a modified correlation gamma function

The apparatus of a correlation gamma function is used to analyze a sample of 2dFGRS galaxies. We suggest a modified gamma-function algorithm with nonintersecting working spheres, which ensures that the counts are independent at each step. The method of nonintersecting spheres has revealed a change in the regime of clustering (a break of the gamma function) on a scale of 10–16h^?1 Mpc (H₀ = 65 km s^?1 Mpc^?1). The standard method yields a scale of 30h^?1 Mpc. An artificial distribution is used as an example to show that, in some cases, the modified algorithm is more responsive to a mixture of distributions with various properties than the standard method.     

M 101 group galaxies

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).     

Infrared luminosities of local-volume galaxies

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 ?25^m to ?11^m. 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/L_K) ∝ (0.27 ± 0.03) log L_K 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/L_K〉 ? (20–25) M_⊙/L_⊙, was found to be much smaller than the expected global ratio, (80–90)M_⊙/L_⊙, in the standard model with Ω_m = 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.     

Voids in the SDSS galaxy survey

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 M _lim (from ?19.7 to ?21.2, H ₀ = 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 M _lim 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 M _lim 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 M _lim starting from M _lim ～ ?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 M _lim. 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 M _lim 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 M _lim. 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 M _abs < M _lim = ?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/M _star). These tendencies become stronger toward the central void regions.     

New probable dwarf galaxies in northern groups of the Local Supercluster

We have searched for nearby dwarf galaxies in 27 northern groups with characteristic distances 8–15 Mpc based on the Second Palomar Sky Survey prints. In a total area of about 2000 square degrees, we have found 90 low-surface-brightness objects, more than 60% of which are absent from known catalogs and lists. We have classified most of these objects (～80%) as irregular dwarf systems. The first 21-cm line observations of the new objects with the 100-m Effelsberg radio telescope showed that the typical linear diameters (1–2 kpc), internal motions (～30 km s^?1), and hydrogen masses (～2 × 10⁷ M _⊙) of the new galaxies correspond to those expected for the dwarf population of nearby groups.     

Kinematics of the galaxy from Cepheids with proper motions from the Gaia DR1 catalogue

A sample of classical Cepheids with known distances and line-of-sight velocities has been supplemented with proper motions from the Gaia DR1 catalogue. Based on the velocities of 260 stars, we have found the components of the peculiar solar velocity vector (U, V, W)_⊙ = (7.90, 11.73, 7.39) ± (0.65, 0.77, 0.62) km s^?1 and the following parameters of the Galactic rotation curve: Ω₀ = 28.84 ± 0.33 km s^?1 kpc^?1, Ω′₀ = ?4.05 ± 0.10 km s^?1 kpc^?2, and Ω″₀ = 0.805 ± 0.067 km s^?1 kpc^?3 for the adopted solar Galactocentric distance R ₀ = 8 kpc; the linear rotation velocity of the local standard of rest is V ₀ = 231 ± 6 km s^?1.