arXiv subjects

M. V. Ryabova

Publications and source records attributed to M. V. Ryabova.

3 recordsLinked to original sources

arXiv2020

The Stellar Population and Orbit of the Galactic Globular Cluster Palomar 3

Deep stellar photometry of one of the most distant Galactic globular clusters, Palomar 3, based on frames taken with the VLT in Johnson-Cousins broadband V and Ifilters is presented, together with medium-resolution stellar spectroscopy in the central region of the cluster obtained with the CARELEC spectrograph of the Observatoire de Haute Provence and measurements of the Lick spectral indices for the integrated spectrum. Computations of the orbital parameters of Palomar 3 and nine Galactic globular clusters with similar metallicities and ages are also presented. The orbital parameters, age, metallicity, and distance of Palomar 3 are estimated. The interstellar absorption is consistent with and supplements values from the literature. The need to obtain more accurate data on the proper motions, ages, and chemical compositions of the cluster stars to elucidate the origin of this globular cluster is emphasized.

astro-ph.GA↗

arXiv2014

Extended OVI haloes of starforming galaxies

We consider evolution of metal-enriched gas exposed to a superposition of time-dependent radiation field of a nearby starburst galaxy and nearly invariant (on timescales 100 Myr) extragalactic ionization background. Within nonequilibrium (time-dependent) photoionization models we determine ionization fraction of the OVI ion commonly observed in galactic circumference. We derive then conditions for OVI to appear in absorptions in extended galactic haloes depending on the galactic mass and star formation rate. We have found that the maximum OVI fraction can reach $\sim 0.4-0.9$ under combined action of the galactic and the extragalactic ionizing radiation fields. We conclude that soft X-ray emission with $E\simgt 113$~eV from the stellar population of central starforming galaxies is the main source of such a high fraction of OVI. This circumstance can explain high column densities ${\rm N(OVI)} \sim 10^{14.5 - 15.3}$~cm$^{-2}$ observed in the haloes of starforming galaxies at low redshifts (Tumlinson etal 2011) {\it even} for a relatively low ({ $\sim 0.01-0.1\zsun$}) metallicity. As a result, the requirements to the sources of oxygen in the extended haloes relax to a reasonably conservative level. We show that at $z\simlt 0.5$ ionization kinetics of oxygen in a relatively dense plasma $n\simgt 10^{-4}$ cm$^{-3}$ of outer halo exposed to a low extragalactic ionizing flux is dominated by nonequilibrium effects.

astro-ph.GA↗

arXiv2008

The Multiplicity of Main Sequence Turnoffs in Globular Clusters

We present color-magnitude diagrams of globular clusters for models with self-enrichment and pre-enrichment. The models with self-enrichment turn out to have two or more main sequence turnoff points in the color-magnitude diagram if the fraction of mass lost by the globular cluster under supernova explosions does not exceed 95-97%. The models with pre-enrichment can have only one main sequence turnoff point. We argue that the cluster wCen evolved according to a self-enrichment scenario.

astro-ph↗