Integral field observations of damped Lyman‐α galaxies

We report preliminary results from a targeted investigation on quasars containing damped Lyman‐α absorption (DLA) lines as well strong metal absorption lines, carried out with the Potsdam Multi Aperture Spectrophotometer (PMAS). We search for line‐emitting objects at the same redshift as the absorption lines and close to the line of sight of the QSOs. We have observed and detected the already confirmed absorbing galaxies in Q2233+131 (z_abs = 3.15) and Q0151+045 (z_abs=0.168), while failing to find spectral signatures for the z = 0.091 absorber in Q0738+313. From the Q2233+131 DLA galaxy, we have detected extended Lyα emission from an area of 3″ ×5″. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Redshift distribution in extragalactic objects and evolution of galaxies

In order to see whether the study of redshift distribution in different classes of extragalactic objects, suspected of belonging to different phases in the evolutionary sequence of galaxies, helps in arriving at a possible picture of the evolutionary sequence of galaxies, histograms have been plotted between the number and the redshift for each of the five classes of extragalactic objects, namely, the QSOs, N-galaxies, Seyfert galaxies, radio galaxies and normal galaxies. It is found that: (i) the highest peaks in the five histograms occur at distinctly different redshifts in the order (Z _peak)_QSOs>(Z _peak)_N-galaxies>(Z _peak)_{Seyfert galaxies}>(Z _peak)_{radio galaxies}> (Z _peak)_{normal galaxies} and (ii) sufficient overlap occurs in the redshift ranges of (a) QSOs and N-galaxies, (b) N-galaxies and Seyfert galaxies, (c) Seyfert galaxies and radio galaxies and (d) radio galaxies and normal galaxies. These facts suggest that the extragalactic objects might be evolving in the sequence: QSOsN-galaxiesSeyfert galaxiesradio galaxiesnormal galaxies. Other independent evidences in support of such an evolutionary sequence have been given. Finally, various aspects of the problem associated with the picture of the evolutionary sequence of galaxies have been critically examined.     

Faint companions of isolated 2MIG galaxies

We present the results of a search for companions around the isolated galaxies from the 2MIG catalog. Among 3227 2MIG galaxies we detected 125 objects with a total of 214 neighbors having radial velocity differences of ΔV < 500 km/s and projected separations of R _p < 500 kpc relative to the 2MIG galaxies. The median luminosity of the companions is 1/25 of the luminosity of catalog galaxies, which has little effect on the dynamic isolation of the latter. The median ratio of the orbital mass to the K-luminosity determined from 60 companions of E and S0 2MIG galaxies, 63M _⊙/L _⊙, is significantly greater than that found from the spiral galaxy companions (17M _⊙/L _⊙). We note that a fraction of 2MIG galaxies with companions may be a part of low-contrast diffuse structures: clouds and filaments.     

Catalog of equatorial coordinates and <Emphasis Type="Italic">B</Emphasis>-magnitudes of stars of the FON project

The catalog of equatorial coordinates α and δ and B-magnitudes of stars of the northern sky (from–4° to +90°) was created as a part of the FON project at the Main Astronomical Observatory of the National Academy of Sciences of Ukraine. The data accumulated in the Joint Digital Archive of the Ukrainian Virtual Observatory were used. The total number of processed plates is 2260. Astronegatives were digitized with Microtek ScanMaker 9800XL TMA and Epson Expression 10000XL scanners in the 1200 dpi scanning mode. The majority of plates have a size of 30 × 30 cm (13000 × 13000 pixels). The catalog contains the data on 19451751 stars and galaxies with B ≤ 16.5m at the epoch of 1988.1. The coordinates of stars and galaxies were obtained in the Tycho-2 reference system, and B-magnitudes were determined in the system of photoelectric standards. The mean internal errors of the catalog are σ_αδ = 0.23″ and σ_B = 0.14^m for all objects or σ_αδ = 0.10″ and σ_B = 0.07^m for stars in the B = 7^m–14^m range. The convergence between the catalog and Tycho-2 is characterized by the following values: 0.06′′ and 0.15^m. The mean-square difference in coordinates from the catalog and from UCAC-4 is σ_αδ = 0.30′′ (18 742 932 objects, or 96.36% of stars and galaxies, were cross-identified).     

Catalog of nearby isolated galaxies in the volume <Emphasis Type="Italic">z</Emphasis> < 0.01

We present a catalog of 520 most isolated nearby galaxies with angular velocities V _LG < 3500 km/s, covering the entire sky. This population of “space orphans” makes up 4.8% among 10 900 galaxies with measured radial velocities. We describe the isolation criterion used to select our sample, called the “Local Orphan Galaxies”(LOG), and discuss their basic optical and HI properties. A half of the LOG catalog is occupied by the Sdm, Im and Ir morphological type galaxies without a bulge. The median ratio M _gas/M _star in the LOG galaxies exceeds 1. The distribution of the catalog galaxies on the sky looks uniform with some signatures of a weak clustering on the scale of about 0.5 Mpc. The LOG galaxies are located in the regions where the mean local density of matter is approximately 50 times lower than the mean global density. We indicate a number of LOG galaxies with distorted structures, which may be the consequence of interaction of isolated galaxies with massive dark objects.     

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.     

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).     

X-ray and radio emission by clusters of galaxies

analysis of new X-ray and optical data confirms that the X-ray luminosityL _x of a cluster of galaxies is strongly dependent on its richness. The radio powerP ₁₄₄₅ of clusters at 1445 MHz is independent of richness, but is greater on the average for clusters with dominant cD galaxies than for those withou. The radio emission depends on the activity of one of the brightest galaxies; dominant cD galaxies are often responsible for radio emission, especially if they have double or multiple nuclei. For a given richness, high values ofL _x andP ₁₄₄₅ sometimes occur together, but no strict correlation betweenL _x andP ₁₄₄₅ exists. Possible tests of thermal-bremsstrahlung and inverse-Compton theories for the X-ray emission are mentioned.     

Orbits of colliding galaxies

A simple, semi-analytic method is developed for obtaining the orbits of galaxies undergoing fast collisions in which the galaxies are represented by Plummer models. The results are found to agree fairly well with those of N-body simulations.A simple formula for obtaining the angle of deflection is deduced. The maximum angle of deflection is 180° forV _p/V _esc(p)=1.00, about 36° forV _p/V _esc(p)=1.50, and about 18° forV _p/V _esc(p)=2.00, whereV _p is the velocity at closest approachp, andV _esc(p) is the parabolic velocity of escape atp. The angle of deflection of a pair of colliding elliptical galaxies without halos is about twice that for a pair of galaxies with halos for the same relative velocity at infinite separation.     

Edge-on Galaxies in the Hubble Ultra Deep Field

We have produced a sample of 58 edge-on spiral galaxies at redshifts z ~ 1 selected in the Hubble Ultra Deep Field. For all galaxies we have analyzed the 2D brightness distributions in the V₆₀₆ and i₇₇₅ filters and measured the radial (h_r) and vertical (h_z) exponential scale lengths of the brightness distribution. We have obtained evidence that the relative thickness of the disks of distant galaxies, i.e., the ratio of the vertical and radial scale lengths, on average, exceeds the relative thickness of the disks of nearby spiral galaxies. The vertical scale length h_z of the stellar disks of galaxies shows no big changes at z = 1. The possibility of the evolution of the radial scale length h_z for the brightness distribution with redshift is discussed.

     

Dark matter influence on velocity dispersion profiles of clusters of galaxies

We have performed a series ofN-body experiments including the effects of a massive dominant background which follows Schuster's density law in order to simulate clusters of galaxies in which a smoothly distributed dark component is present. The existence of this background is inferred from the weak luminosity segregation observed in clusters which, however, show several characteristics of well-relaxed systems. The comparison of the velocity dispersion profiles of three clusters of galaxies (Coma, Perseus, and Virgo) with those obtained in the numerical experiments allows us to place some constraints on both the distribution and amount of distributed dark material in these clusters. The profiles are rather insensitive to variations in the ratio of the background mass to the mass attached to galaxies (M _b/M_g), but exhibit a strong dependence on their relative concentration. We conclude that highly concentrated background models are not consistent with observations. We find a maximum value for the ratio of the gravitational radius of the galaxies and the background (R _g/R_b) (approximately 0.6) and using previous results (Navarroet al., 1986) we conclude that virial theorem masses underestimate the total mass (M _b+M _g) of the clusters. As a final result, we derive a minimum value for theM _b/M_g ratio. All these conclusions could apply in general if Coma, Perseus, and Virgo constitute a fair sample of the rich clusters of galaxies in the Universe.     

The environmental dependence of u-, g-, r-, i-, and z-band luminosities for galaxies above and below the value of Mr*

Using two volume-limited Main galaxy samples of the Sloan Digital Sky Survey Data Release 6 (SDSS DR6), we have explored the difference of the environmental dependence of u-, g-, r-, i-, and z-band luminosities between galaxies above and below the value of M _r^*. It turns out that in the luminous volume-limited sample, all the five band luminosities strongly correlate with local environments. Because the u-band luminosity of galaxies still strongly depends on local environments in the faint volumelimited sample, we conclude that M _r^* is not an important characteristic parameter for the environmental dependence of the u-band luminosity. It is worth noting that for the u-band, the subsample at low density has a higher proportion of luminous galaxies and a lower proportion of faint galaxies than the one at high density, which is opposite to widely accepted conclusion: luminous galaxies exist preferentially in the densest regions of the universe, but faint galaxies are located preferentially in low density regions. Our results show that the environmental dependence of luminosity is not a single trend in different luminosity regions and for different bands.     

The role of diffuse matter in galactic coronas

An upper limit to the gas content in the coronas of giant galaxiesM _gas<0.04M _cor has been calculated on the basis of observational data on the emission of clusters of galaxies in different wavelength ranges. An analysis of companion galaxies has revealed a correlation of their morphological types with the distances to central giant galaxies. A gasodynamical interpretation of this regularity is suggested and a possible picture of the evolution of the galactic coronas is presented.     

Studying the first galaxies with ALMA

We discuss observations of the first galaxies, within cosmic reionization, at centimeter and millimeter wavelengths. We present a summary of current observations of the host galaxies of the most distant QSOs (z∼6). These observations reveal the gas, dust, and star formation in the host galaxies on kpc-scales. These data imply an enriched ISM in the QSO host galaxies within 1 Gyr of the big bang, and are consistent with models of coeval supermassive black hole and spheroidal galaxy formation in major mergers at high redshift. Current instruments are limited to studying truly pathologic objects at these redshifts, meaning hyper-luminous infrared galaxies (L _FIR ∼10¹³ L _⊙). ALMA will provide the one to two orders of magnitude improvement in millimeter astronomy required to study normal star forming galaxies (i.e. Ly-α emitters) at z∼6. ALMA will reveal, at sub-kpc spatial resolution, the thermal gas and dust—the fundamental fuel for star formation—in galaxies into cosmic reionization.     

On the relation between radius,luminosity, surface brightness,and surface density in elliptical galaxies

We have analyzed luminosity profiles of E galaxies studied by Strom and Strom in six clusters of galaxies. We have found a relationship between radius, luminosity, and surface brightness for galaxies in each of the clusters. A dependence of the zero point of the relation with the local projected density of galaxies is likewise found:r _{e proj} ^–0.14 L ^0.445 I _e ^–0.413 . This relationship implies (i) that there is not a universal luminosity profile for elliptical galaxies, (ii) the environmental variation of radius is larger than that produced by mergers of galaxies, (iii) distance to a galaxy can be estimated from apparent magnitude, surface brightness, angular size, and apparent local projected density of galaxies.     

The phenomenon of the galaxy NGC 6286: A forming polar ring or a superwind?

We present our observations of the pair of interacting galaxies NGC 6285/86 carried out with the 6-m Special Astrophysical Observatory (SAO) telescope using 1D and 2D spectroscopy. The observations of NGC 6286 with a long-slit spectrograph (UAGS) near the Hα line revealed the rotation of the gaseous disk around an axis offset by 5″–7″ from the photometric center and a luminous gas at a distance up to 9 kpc in a direction perpendicular to the galactic plane. Using a multipupil fiber spectrograph (MPFS), we constructed the velocity fields of the stellar and gaseous components in the central region of this galaxy, which proved to be similar. The close radial velocities of the pair and the wide (5′×5′) field of view of the scanning Fabry-Perot interferometer (IFP) allowed us to simultaneously obtain images in the Hα and [N II]λ6583 lines and in the continuum, as well as to construct the radial velocity fields and to map the distribution of the [N II]λ6583/Hα ratio for both galaxies. Based on all these data, we studied the gas kinematics in the galaxies, constructed their rotation curves, and estimated their masses (2 × 10¹¹M_⊙ for NGC 6286 and 1.2 × 10¹⁰M_⊙ for NGC 6285). We found no evidence of gas rotation around the major axis of NGC 6286, which argues against the assumption that this galaxy has a forming polar ring. The IFP observations revealed an emission nebula around this galaxy with a structure characteristic of superwind galaxies. The large [N II]λ6583/Hα ratio, which suggests the collisional excitation of its emission, and the high infrared luminosity are additional arguments for the hypothesis of a superwind in the galaxy NGC 6286. A close encounter between the two galaxies was probably responsible for the starburst and the bipolar outflow of hot gas from the central region of the disk.     

Gravitational potential energy of a disk-sphere pair of galaxies

Algebraic expressions are obtained for the interaction potential energy of a pair of galaxies in which one is disk shaped and the other spherical. The density distribution in the disk galaxy is represented by a polynomial in ascending powers of the distance from the centre of the disk while the density distribution in the spherical galaxy is represented by the superposition of spherical polytropes of integral indices. The basic functions required for obtaining the interaction potential energy of a coplanar disk-sphere pair of galaxies are tabulated. The forces of attraction between a coplanar disk-sphere pair of galaxies are shown graphically for two density models of disk and spherical galaxies. An overlapping coplanar disk-sphere pair of galaxies attract just like two mass-points at a certain separation,r _c, of their centres. The force of attraction is less than that of two mass-points having masses equal to the masses of the two galaxies, if the separation of the centres is less thanr _c, and greater if the separation is greater thanr _c.For a typical coplanar disk-sphere pair of galaxies (the density of the disk is represented by Model II and of the sphere by a polytropic indexn=4) of equal radii, we note the following. At a separation of 0.79R, R being the common radius of the two galaxies, the force of attraction between the pair is the same as if the entire mass of each galaxy is concentrated at its centre. The mass-point model for the two galaxies will overestimate the force of attraction by more than a factor of 10 if the separation is less than 0.36R. For separation greater than the radii of the galaxies the mass-point model will underestimate the force but the departure in this case is less than 33%.     

Flat Galaxies of the RFGC Catalog Detected in the HIPASS Survey

Data from the H I Parkes All-Sky Survey (HIPASS) of the southern sky in the neutral hydrogen line are used to determine the radial velocities and widths of the H I line for flat spiral galaxies of the Revised Flat-Galaxy Catalog (RFGC) seen edge-on. The sample of 103 flat galaxies detected in HIPASS is characterized by a median radial velocity of +2037 km/sec and a median width of the H I line at the level of 50% of maximum of 242 km/sec. For RFGC galaxies the 50% detection level in HIPASS corresponds to an apparent magnitude B _t = 14 ^m .5 or an angular diameter a = 2.9. The relative number of detected galaxies increases from 2% for the morphological types Sbc and Sc to 41% for the type Sm. The median value of the ratio of hydrogen mass to total mass for RFGC galaxies is 0.079. With allowance for the average internal extinction for edge-on galaxies, <B _t< = 0 ^m .75, the median ratio of hydrogen mass to luminosity, M _{H I}/L _B = 0.74 M /L , is typical for late-type spirals. Because of its small depth, HIPASS reveals only a few RFGC galaxies with previously unknown velocities and line widths.     

The surface brightness of IRAS galaxies

Using IRAS measurements, we find positive correlations between both the infrared to optical flux ratio (L _FIR/L _B) and infrared colour temperature (L ₆₀/L ₁₀₀) with optical surface brightness. These correlations can be understood by high surface brightness galaxies having (i) a high star formation rate, or (ii) a high-space density of stars and dust.In an attempt to interpret (ii) above, we have produced radiative transfer models for the dust absorption in a galactic disc. These models indicate that the highest surface brightness galaxies may be the most dust obscured (i.e., optically thick) and that the total luminosity (and, hence, mass) of these galaxies may be considerably underestimated.     

Search for companions of nearby isolated galaxies

The radial velocities are measured for 45 galaxies located in the neighborhoods of 29 likely isolated galaxies in a new catalog. We find that about 85% of these galaxies actually are well isolated objects. 4% of nearby galaxies with V _LG < 3500 km/s are this kind of cosmic "orphan" Translated from Astrofizika, Vol. 52, No. 2, pp. 203–210 (May 2009).