The statistical investigation of type Ib/c and II supernovae and their host galaxies

This is a statistical study of the properties of type Ib/c and II supernovae and of the integral parameters of their spiral host galaxies. The methods of one-dimensional and multivariate statistics were applied to the data sample. It was found that the Ib/c supernovae are more concentrated radially toward the centers of the galaxies than those of type II. The distributions of the radial distances R_SN/R₂₅ for the type Ib/c and II supernovae in active galaxies are more concentrated toward the center than in normal galaxies. This effect is stronger for type Ib/c than for type II supernovae. __________ Translated from Astrofizika, Vol. 51, No. 1, pp. 89–98 (February 2008).     

Tidal structures of z ∼ 1 galaxies in the Hubble Deep Field

An analysis of the images of objects in the Northern Hubble Space Telescope Deep Field has revealed twelve galaxies with tidal tails at redshifts from 0.5 to 1.5. The integrated characteristics of the newly discovered tidal structures are found to be similar to those of the tails of local interacting galaxies. The space density of galaxies with tidal tails is found to depend on z as (1+z)^4±1(q ₀=0.05), according to the data on objects with z=0.5–1.0. The exponent decreases to 3.6 if barred galaxies are included. The change in the rate of close encounters between galaxies of comparable masses (i.e., those that produce extended tidal structures) is estimated. If the rate of galactic mergers is governed by the same process, our data are indicative of the rapid evolution of galaxy merger rate toward z ～ 1.     

Structure of the Cluster of Galaxies A 548

The hierarchical and dynamical structure of the bimodal cluster of galaxies A 548, consisting of the two components A 548E and A 548W, was investigated. An HTree cluster analysis was used for this purpose. Based on the results of the analysis, three main nuclei, five subgroups, and six triplets of galaxies were distinguished in the cluster. These subgroups lie in regions of local density maxima of the entire cluster. The average radial velocities of the subgroups coincide with local maxima in the V _r distribution of the entire cluster. The members of subgroups are 1.25 stellar magnitudes brighter, on the average, than other galaxies. Based both on the projected positions of the galaxies and on their radial velocities, the field of the cluster has a more uniform structure than does the entire system as a whole. Galaxies with different V _r are unevenly distributed in the cluster: radial velocity increases from the periphery toward the center.     

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.     

Flattening of galaxies of different morphological types in subclusters of Coma

This paper deals with the observed variation in the flattening of galaxies with the density of galaxies in the subclusters of Coma surrounding NGC 4889, NGC 4874, and NGC 4839 based on data from the Abastumani Combined Catalog of Galaxies. The mean values of the observed ratios of the diameters of the galaxies, as well as histograms of their distributions, indicate that in the central, dense regions of the subclusters within a volume of 0.5h ₇₅ ⁻¹ Mpc³, E and S0 type galaxies are close to spheroidal. A significant reduction in the mean values of the diameters of the galaxies in the subclusters is noted, regardless of their morphology relative to the galaxies in the halo of the Coma cluster. In the subclusters, spiral galaxies are found with a hydrogen deficit that is more than 5 times the hydrogen deficit in spirals within the halo of the cluster. According to their 3-D coordinates, most of the galaxies with a hydrogen deficit are located closer to the south-east edge of the subcluster surrounding NGC 4874 near an extended gas filament in the x-ray region. This may indicate that the subcluster is moving toward a central condensation of faint galaxies in the Coma cluster and a possible merger with it. __________ Translated from Astrofizika, Vol. 50, No. 3, pp. 355–368 (August 2007).     

The Hubble relation: Differences between galaxy types Sb and Sc

The most accurate data on galaxy types, corrected apparent magnitudes and redshifts as given in the Sandage-TammanRevised Shapley-Ames catalog are analyzed. It is shown that Sb galaxies of the same luminosity class as M31 and M81 define a narrow Hubble relation withH ₀=65 _–6 ⁺¹⁵ km s^–1 Mpc^–1.In contrast, Sc galaxies deviate strongly towars higher redshift from a linear, log redshift—apparent magnitude relation. Not all this deviation can be selection effect due to increasing volume sampled at increasing redshift (Malmquist bias). Physical associations of groups of galaxies in theRSA Catalog are used to establish the existence of various amounts of excess (non-velocity) redshifts among Sc and allied types of galaxies.Independent distances fromHi line width — luminosity criterion (Tully-Fisher) are analyzed. It is shown that this criterion gives much smaller distances than redshifts do for galaxies which deviate above the Hubble line. Unless the Tully-Fisher relation gives too small distances for more luminous galaxies, this confirms the excess redshift to be intrinsic to the Galaxy. But it is next demonstrated, that for low redshift galaxies, there is no discrepancy between redshift and Tully-Fisher distance even though there is a wide range of absolute magnitudes.If Tully-Fisher distances are accepted, the onlly alternative to having a Hubble constant which increases strongly with distance is to have a component of the higher redshift Sc's contributed by a non-recessional redshift. Streaming motions would have to be large, increase with distance and be always in the receding sence. It is shown here that the Sc's which deviate most from the Hubble relation and have the largest discrepancies with Tully-Filsher distances lie predominantly in the sky toward very nearby groups of galaxies. If they were at these closer distances the discordant galaxies, mostly ScI's, would have dwarfish physical properties but not so unprecedented as the large sizes which result from redshift distances.Finally the interaction of specific high redshift ScI's with nearby galaxies is presented as an independent proof that ScI's are generally small, low luminosity galaxies. This result furnishes insight into the long standing puzzle of how apparently distant ScI's can interact with nearby galaxies such as in Stephan's Quintet, Seyfert's Sextet and NGC 4151/4156.     

Classical cosmological tests for galaxies of the Hubble Ultra Deep Field

Images of the Hubble Ultra Deep Field are analyzed to obtain a catalog of galaxies for which the angular sizes, surface brightness, photometric redshifts, and absolute magnitudes are found. The catalog contains a total of about 4000 galaxies identified at a high signal-to-noise ratio, which allows the cosmological relations angular size—redshift and surface brightness-redshift to be analyzed. The parameters of the evolution of linear sizes and surface brightness of distant galaxies in the redshift interval 0.5–6.5 are estimated in terms of a grid of cosmological models with different density parameters (Ω _V ; Ω _m ). The distribution of photometric redshifts of galaxies is analyzed and possible superlarge inhomogeneities in the radial distribution of galaxies are found with scale lengths as large as 2000 Mpc.     

Radio continuum and far-infrared emission from the galaxies in the Eridanus group

The Eridanus galaxies follow the well-known radio—FIR correlation. The majority (70%) of these galaxies have their star formation rates below that of the Milky Way. The galaxies that have a significant excess of radio emission are identified as low luminosity AGNs based on their radio morphologies obtained from the GMRT observations. There are no powerful AGNs (L _20cm > 10²³ W Hz⁻¹) in the group. The two most far-infrared and radio luminous galaxies in the group have optical and HI morphologies suggestive of recent tidal interactions. The Eridanus group also has two far-infrared luminous but radio-deficient galaxies. It is believed that these galaxies are observed within a few Myr of the onset of an intense star formation episode after being quiescent for at least a 100 Myr. The upper end of the radio luminosity distribution of the Eridanus galaxies (L _20cm ∼ 10²² W Hz⁻¹) is consistent with that of the field galaxies, other groups, and late-type galaxies in nearby clusters.     

A Model for Structure Formation Seeded by Gravitationally Produced Matter

The Arecibo H i Strip Survey probed the halos of approximately 300 cataloged galaxies and the environments of approximately 14 groups with sensitivity to neutral hydrogen masses >/=107 M middle dot in circle. The survey detected no objects with properties resembling the high-velocity clouds (HVCs) associated with the Milky Way or Local Group. If the HVCs were typically MHi=107.5 M middle dot in circle objects distributed throughout groups and galaxy halos at distances of approximately 1 Mpc, the survey should have made approximately 70 HVC detections in groups and approximately 250 detections around galaxies. The null detection implies that HVCs are deployed at typical distances of 相似文献   

Far infrared emission from galaxies

Until recently far infrared (FIR) observations of galaxies were limited to about a dozen bright and/or active galaxies. New photometric data has become available from Infrared Astronomical Satellite (IRAS) on 33 galaxies (most of them faint) from IRAS Circular Nos. 1, 2, and 3 The FIR spectra of these galaxies are similar. The far infrared fluxF _FIR in the wavelength interval 9–118 m of the brighter galaxies is seen to be correlated with the integrated optical magnitudeB _T ⁰ . The 12 and 25 m fluxes of these galaxies exhibit the same dependence onB _T ⁰ as the 10 and 21 m fluxes from Seyferts and other emission-line galaxies. This suggests that the galaxies detected by IRAS are some type of active galaxies in accord with the high percentage of these galaxies predicted by Lock and Rowan-Robinson (1983).     

A Catalogue of Galaxies within 10 MPC

A catalogue is given of the 179 known galaxies within 10 Mpc. The inclusion of a galaxy depends on its redshift (v₀ ≤ 500 km s⁻¹) or, in the case of 7 dwarf galaxies, on the fact that their distances are known to be small. The catalogue contains in addition 52 more distant galaxies with v₀ ≤ 500 km s⁻¹: 50 are bona fide Virgo cluster members and 2 are members of the Leo group. Positions, types, absorption-corrected luminosities, and velocities are given for the catalogue galaxies. The catalogue is believed to be nearly complete for galaxies brighter than ∽ – 18^m.5, but it contains also many considerably fainter galaxies. The galaxies within 10 Mpc form the Local Group with 28 members and seven additional groups with a total of 92 known members. 59 galaxies (33%) do not seem to belong to any group.     

Study of galaxies in the Lynx-Cancer void. IV. Photometric properties

We present the results of a photometric study of 85 objects from the updated sample of galaxies residing in the nearby Lynx-Cancer void. We perform our photometry on u, g, r, and i-band images of the Sloan Digital Sky Survey. We determine model-independent galaxy parameters such as the integrated magnitudes and colors, effective radii and the corresponding surface brightness values, optical radii and Holmberg radii. We analyze the radial surface brightness profiles to determine the central brightness values and scale lengths of the model disks. We analyze the colors of the outer parts of the galaxies and compare them with model evolutionary tracks computed using the PEGASE 2 software package. This allowed us to estimate the time T _SF elapsed since the onset of star formation, which turned out to be on the order of the cosmological time T ₀ for the overwhelming majority of the galaxies studied. However, for 13 galaxies of the sample the time T _SF does not exceed T ₀/2 ～ 7 Gyr, and for 7 of them T _SF ? 3.5 Gyr. The latter are mostly unevolved objects dominated by low-luminosity galaxies with M _B > ?13.2. We use the integrated magnitudes and colors to estimate the stellar masses of the galaxies.We estimate the parameter M(H I)/L _B and the gas mass fractions for void galaxies with known HI-line fluxes. A small subgroup (about 10%) of the gas-richest void galaxies with M(H I)/L _B ? 2.5 has gas mass fractions that reach 94–99%. The outer regions of many of these galaxies show atypically blue colors. To test various statistical differences between void galaxies and galaxies from the samples selected using more general criteria, we compare some of the parameters of void galaxies with similar data for the sample of 195 galaxies from the Equatorial Survey (ES) based on a part of the HIPASS blind HI survey. The compared samples have similar properties in the common luminosity interval ?18.5<M _g < ?13.5. The faintest void galaxies differ appreciably from the ES survey galaxies. However, the ES survey also contains about 7% of the so-called “inchoate” galaxies with highM(H I)/L _B ratios, most of which are located far from massive neighbors and are probably analogs of void galaxies.     

The observed structure of extremely distant galaxies

We have identified 22 galaxies with photometric redshifts z_ph=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 M_B≈?20^m. 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 z_ph=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.     

Gravitationally lensed QSOs in the ISSIS/WSO-UV era

Gravitationally lensed QSOs (GLQs) at 1≤z≤2 play a key role in understanding the cosmic evolution of the innermost parts of active galaxies (black holes, accretion disks, coronas and internal jets), as well as the structure of galaxies at intermediate redshifts. With respect to studies of normal QSOs, GLQ programmes have several advantages. For example, a monitoring of GLQs may lead to unambiguous detections of intrinsic and extrinsic variations. Both kinds of variations can be used to discuss central engines in distant QSOs, and mass distributions and compositions of lensing galaxies. In this context, UV data are of particular interest, since they correspond to emissions from the immediate surroundings of the supermassive black hole. We describe some observation strategies to analyse optically bright GLQs at z∼1.5, using ISSIS (CfS) on board World Space Observatory-Ultraviolet.     

X-ray emission from dwarf galaxies: IC 2574 revisited

Until recently, few unequivocal detections had been reported of the hot, X-ray emitting gas thought to be associated with the large, coherent structures variously described as supershells or superbubbles in dwarf irregular (dIrr) galaxies. In this contribution we report follow-up XMM-Newton and Chandra observations of our ROSAT detection of X-ray emission associated with the supergiant shell in the nearby dIrr galaxy IC 2574, a member of the M 81 group of galaxies. The spectral properties of the X-ray source suggest that we are dealing with a young (age < 2000 yr) supernova remnant (SNR). This SNR is most likely one of the many supernovae which have exploded in that region and which have created the impressive supergiant HI shell. This revised version was published online in August 2006 with corrections to the Cover Date.     

Investigation of barred galaxies. vi. a comparative statistics of sb and sa galaxies. the cold gas properties

The gas properties of barred and unbarred spiral galaxies are compared in two complete samples. It is found that two types of spiral galaxies do not differ from each other in atomic and molecular gas contents. On average there is 6 times more HI than H₂ in spiral galaxies and the ratio MH2/MHI decreases from early to late types. The barred and unbarred spirals in general show a similar behaviors of the gas-to-luminosity relationships, but also there are certain differences between them such as correlation of two gas phases (HI and H₂)for unbarred galaxies. It is suggested that different behaviors of two types galaxies are due to the higher star forming activity of barred with respect unbarred spirals. The expected values of HI and H₂ gas contents have been estimated using blue and far-infrared emission. Published in Astrofizika, Vol. 43, No. 3, pp. 405-410, July–September, 2000.     

Interacting galaxies in sparsely populated groups

We calculated the median values of the following parameters for 87 groups of galaxies with three to eight components: the mean rms velocity of the galaxies in the group, S _v = 166 km s^?1; the harmonic mean radius, R _h = 29 kpc; and the mass-to-light ratio, M _vir/L = 33 M _⊙/L _⊙. The M _vir/L ratio depends on the population of the system, while S _v does not depend on R _h. To ascertain the relationship between the activity of galaxies in groups and their morphological composition and the effect of the “environment” on the evolutionary processes in groups, we consider the fraction of galaxies with UV excess in the sample of interacting galaxies in groups (6%), single peculiar galaxies (8%), and isolated galaxies (4%) and their morphological composition. We also show that the number of active galaxies decreases with increasing population of the group of galaxies, while the frequency of occurrence of early-type (E/S0) galaxies increases.     

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.     

Optical identifications of 230 HIPASS radio sources

We present the coordinates, apparent magnitudes, and morphological types for 230 galaxies presumably identified with HIPASS (HI Parkes All-Sky Survey) sources. The new optical counterparts of the HIPASS sources follow the well-known statistical relationships between the hydrogen mass, luminosity, and type of galaxies. Low-surface-brightness galaxies constitute a significant fraction among these objects. The median value of the hydrogen mass-to-luminosity ratio for them is a factor of 2 or 3 higher than that for bright HIPASS galaxies, reaching 1.7M _⊙/L _⊙. A number of our objects are located near the boundary log(M _HI/L _B ) = 0.2(M _B + 20) that defines the zone of gravitational stability of disk galaxies against large-scale star formation.     

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.