Kasparova A.V.,Universitetskii Pr 13
Astronomy Letters | Year: 2012
Based on two models, we investigate the molecular-to-atomic gas ratio in Virgo cluster galaxies in comparison with field galaxies. We show that the enhanced metallicity for cluster members and the ram pressure stripping of atomic gas from the disk periphery cannot fully explain the observed gas component ratios. The additional environmental factors affecting the interstellar medium and leading to an increase in the molecular gas fraction should be taken into account for cluster galaxies. © 2012 Pleiades Publishing, Ltd.
Sazhina O.S.,Universitetskii Pr 13
Journal of Experimental and Theoretical Physics | Year: 2013
The dependences of the mean expected number of cosmic strings on their redshift up to the surface of last scattering have been derived. The calculations are based on the geometric probability of a straight string segment crossing a given field and on information about the absence of strings when they are searched for via their gravitational lensing effects in optical catalogs. It is shown that there are no strings for redshifts 0 < z < 1.954, but the expected number of strings for 0 < z < 5 can be no more than 2.1 × 103 at the 95% confidence level. The expected number of strings for redshifts up to z = 1100 can be no more than 2.4 × 10 4 at the 95% confidence level. The latter estimate is sensitive to a priori information about the absence of cosmic strings in the redshift range 0 < z < 1.954 in a field of 4.48 square degrees in optical catalogs; it is smaller than the estimate without allowance for this information by 6%. © 2013 Pleiades Publishing, Ltd.
Busarev V.V.,Universitetskii Pr 13
Solar System Research | Year: 2010
Asteroid 21 Lutetia is one of the objects of the Rosetta mission carried out by the European Space Agency (ESA). The Rosetta spacecraft launched in 2004 is to approach Lutetia in July 2010, and then it will be directed to the comet Churyumov-Gerasimenko. Asteroid 4 Vesta is planned to be investigated in 2011 from the Dawn spacecraft launched by the National Aeronautics and Space Administration (NASA) in 2007 (its second object is the largest asteroid, 1 Ceres). The observed characteristics of Lutetia and Vesta are different and even contradictory. In spite of the intense and versatile ground-based studies, the origin and evolution of these minor planets remain obscure or not completely clear. The types of Lutetia and Vesta (M and V, respectively) determined from their spectra correspond to the high-temperature mineralogy, which agrees with their albedo estimated from the Infrared Astronomical Satellite (IRAS) observations. However, according to the opinion of some researchers, Lutetia is of the C type, and, therefore, its mineralogy is of the lowtemperature type. In turn, hydrosilicate formations have been found in some places on the surface of Vesta. Our observations also testify that at some relative phases of rotation (RP), the reflectance spectra of Lutetia and Vesta demonstrate features confirming the presence of hydrosilicates in the surface material. However, this fact can be reconciled with the magmatic nature of Lutetia and Vesta if the hydrated material was delivered to their surfaces by falling primitive bodies. Such small bodies are probably present everywhere in the main asteroid belt and can be the relicts of silicate-icy planetesimals from Jupiter's formation zone or the fragments of primitive-type asteroids. When interpreting the reflectance spectra of Lutetia and Vesta, we discuss the spectral classification by Tholen (1984) from the standpoint of its general importance for the estimation of the mineralogical type of the asteroids and the study of their origin and evolution. © 2010 Pleiades Publishing, Ltd.
Busarev V.V.,Universitetskii Pr 13
Solar System Research | Year: 2011
The reflectance spectra of asteroids 10 Hygiea (C-type), 135 Hertha (M-type), and 196 Philomela (S-type) are obtained in a range of 0.40-0.91 μm with different time intervals. In this paper, the technique of the spectral measurements of asteroids is analyzed and the reflectance spectra of Hygiea, Hertha, and Philomela are interpreted. The main physical and chemical factors and processes influencing the spectral characteristics of asteroids are considered. It is determined that the spectra of Hertha and Hygiea contain variations exceeding the measurement errors several times at different relative rotation phases, whereas spectral variations of Philomela caused by its rotation hardly exceed the error limits. Most probably, these variations are caused by local manifestations of the impact metamorphism of the material of asteroids in serious impact events. Results show that, to determine the prevailing spectral type and the corresponding mineralogy of each asteroid, one should estimate and take into account the changes in its spectral characteristics for a time interval comparable to the rotation period. © 2011 Pleiades Publishing, Ltd.
Somov B.V.,Universitetskii Pr 13
Astronomy Letters | Year: 2011
We discuss the peculiarities of fast magnetic reconnection in the essentially nonequilibrium magnetosphere of a compact relativistic object: a neutron star, a magnetar, a white dwarf. Such a magnetosphere is produced by the interaction of a large-amplitude shock wave with a strong stellar magnetic field. We present an analytical solution of the generalized two-dimensional problem on the magnetosphere's structure, the shape of its boundary, and the direct and reverse currents in a reconnecting current sheet. The uncompensated magnetic force acting on the reverse current is determined. Characteristic parameters of the nonequilibrium magnetosphere of compact stellar objects are estimated. We show that the excess magnetic energy of the magnetosphere is comparable to the mechanical energy brought into it by the shock at the instant of impact. The possibility of particle acceleration to enormous energies is discussed. © 2011 Pleiades Publishing, Ltd.