Evolution of dwarf galaxies in the Centaurus A group

We consider star formation properties of dwarf galaxies in Cen A group observed within our HST/ACS projects number 9771 and 10235. We model color-magnitude diagrams of the galaxies under consideration and measure star formation rate and metallicity dependence on time. We study environmental dependence of the galaxy evolution and probable origin of the dwarf galaxies in the group.Comment: To appear in proceedings IAU Symp 244, 'Dark Galaxies and Lost Baryons', June 200

HI properties of nearby galaxies from a volume-limited sample

We consider global HI and optical properties of about three hundred nearby galaxies with V$_0 < 500$ km/s. The majority of them have individual photometric distance estimates. The galaxy sample parameters, e.g. their linear diameters, their HI mass-to-luminosity ratio, their total mass-to-luminosity ratio, their mean optical surface brightness show some known and some new correlations implying a meaningful dynamic explanation. For the LV galaxies their HI mass and angular momentum follow a nearly linear relation expected for rotating gaseous disks being near the threashold of gravitational instability, favourable for active star formation.Comment: 5 pages, 9 figures, uses laa.sty accepted by A&A Suppl. Serie

Electron loss of fast projectiles in the collisions with molecules

The single and multiple electron loss of fast highly charged projectiles in the collisions with neutral molecules are studied within the framework of a nonperturbative approach. The cross sections for single, double, and triple electron losses are calculated for the collision system $Fe^{q+}\to N_2$ ($q$=24, 25, 26) at the collision energies 10, 100, and 1000 MeV/u. The effects caused by the collision multiplicity and the orientation of the axis of target molecule are treated. It is shown that collision multiplicity effect leads to considerable differences for the cases of perpendicular and parallel orientations of the molecular axes with respect to the direction of the projectile motion, while for chaotic orientation such effect is negligible

Suites of dwarfs around nearby giant galaxies

We consider a sample of the Updated Nearby Galaxy Catalog that contains eight hundred objects within 11 Mpc. Environment of each galaxy was characterized by a tidal index $\Theta_1$ depending on the separation and mass of the galaxy's Main Disturber (=MD). We ascribed the UNGC galaxies with a common MD to its suite, and ranked suite members according to their $\Theta_1$. All suite members with positive $\Theta_1$ are assumed to be physical companions of the MD. The distribution of suites by the number of members, n, follows to a relation $N(n) \sim n^{-2}$. The twenty most populated suites contain 468 galaxies, i.e. 59% of the UNGC sample. About 58% of our sample are members of physical groups. The fraction of MDs among the brightest galaxies is almost 100% and drops to 50% at $M_B = -18^m$. We discuss various properties of MDs, as well as galaxies belonging to their suites. The suite abundance practically does not depend on morphological type, linear diameter or hydrogen mass of MD, revealing the tightest correlation with the MD dynamical mass. Dwarf galaxies around MDs exhibit well-known segregation effects: the members of outskirts have later morphological types, richer HI-contents and higher rates of star formation activity. Nevertheless, there are some intriguing cases when dwarf spheroidal galaxies occur at the far periphery of the suites, as well as some late-type dwarfs residing close to MDs. The multiplicity of nearby groups according to number of their physical members can be described by the Hirsh-like index $h_g = 9$, indicating that the Local Volume contains 9 groups with populations exceeding 9 members. (abridged)Comment: 5 tables, 7 figures. Accepted for The Astronomical Journal. The electronic version of tables as well as the article with figures in high resolution are available at the Local Volume Galaxies database web-page http://www.sao.ru/lv/lvgd