arXiv subjects

N. Ya. Sotnikova

Publications and source records attributed to N. Ya. Sotnikova.

24 records · Page 2Linked to original sources

arXiv2004

The Disk Wind in the Young Binaries and the Origin of the Cyclic Activity of Young Stars

We present results of numerical modeling of the cyclic brightness modulation in the young binary systems with the eccentric orbits and low-mass secondary components. Brightness variations of the primary is due to the periodical extinction variations on the line-of-sight caused by the disk wind of the secondary and a common envelope it produces. A matter distribution in the envelope has been calculated in the ballistic approach. Calculations showed that for the young binaries with the elliptic orbits parameters of the photometric minima (their depth, duration and the shape of light curves) depend not only on the disk wind parameters and an inclination of the binary orbit to the line-of-sight but also on the longitude of the periastron. A modulation of the scattered radiation of the common envelope with a phase of the orbital period has been investigated in the single scattering approach. It is shown that an amplitude of the modulation is maximal when the system is seen edge-on and has also a non-zero value in the binaries observed pole-on. Possible applications of the theory to the young stellar objects are discussed. In particular, an attention is payed to a resemblance of the light curves in some models with light curves of the objects suspected as candidates to FUORs.

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arXiv2003

Mechanisms of the Vertical Secular Heating of a Stellar Disk

We investigate the nonlinear growth stages of bending instability in stellar disks with exponential radial density profiles.We found that the unstable modes are global (the wavelengths are larger than the disk scale lengths) and that the instability saturation level is much higher than that following from a linear criterion. The instability saturation time scales are of the order of one billion years or more. For this reason, the bending instability can play an important role in the secular heating of a stellar disk in the $z$ direction. In an extensive series of numerical $N$-body simulations with a high spatial resolution, we were able to scan in detail the space of key parameters (the initial disk thickness $z_0$, the Toomre parameter $Q$, and the ratio of dark halo mass to disk mass $M_{\rm h} / M_{\rm d}$). We revealed three distinct mechanisms of disk heating in the $z$ direction: bending instability of the entire disk, bending instability of the bar, and heating on vertical inhomogeneities in the distribution of stellar matter.

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arXiv2001

Effect of the environment on the Fundamental Plane of elliptical galaxies

We present an analysis of the location of interacting E/S0 galaxies on the Fundamental Plane (FP). Using the NEMO package, we performed N-body simulations of close encounters and mergers of two self-gravitating spherical galaxies. Two models for encounting galaxies - Plummer's and Hernquist's - were used. The number of particles ranged from 20000 to 50000 per galaxy. The changes of central density, half-mass radius and central velocity dispersion were analysed. It was found that close encounters between galaxies alter noticeably the above parameters within a very short time interval (10^7 - 10^8 years) just before the final merger. The amplitudes of parameter changes strongly depend on the initial mass concentration of a model. In some experiments we considered an encounter of two spherical galaxies with dark matter components. The effect of parameter changes was less pronounced than for the experiments without a dark halo. The results of the simulations were used to discuss the FP for interacting early-type galaxies.

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arXiv2000

Tidal Tails and Galaxy Evolution

We review recent results on the tidal structures of spiral galaxies. Topics included are general characteristics of tails; kinematics of tidal structures and dark haloes of host galaxies; frequency of tidal distortions at z~1.

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arXiv2000

The Polar Stellar Ring and Dark Halo of NGC 5907

Numerical simulations of the disruption of a dwarf companion moving in the polar plane of a massive galaxy are presented. The constructed model is compared with observational data on the recently discovered low-surface-brightness stellar ring around galaxy NGC 5907. Constraints on the ring lifetime (<=1.5 gyr after the first approach of the galaxies), on the structure of companion -- the ring presecursor, and on mass of dark halo of the main galaxy in whose gravitational field the companion moves are provided. The dark halo mass within 50 kpc of NGC 5907 center cannot exceed 3 or 4 "visible" masses.

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arXiv2000

Effect of the Environment on the Fundamental Plane of Elliptical Galaxies

We present an analysis of interacting E/S0 galaxies location on the Fundamental Plane. Using the NEMO package, we performed N-body simulations of close encounters and mergers between two spherical galaxies. We followed how structural and dynamical parameters (central density, half-mass radius and velocity dispersion)of galaxies are changed during the encounter. We analysed the dependence of these changes on initial mass concentration and presence of dark halo. The results of our simulations are used to discuss the Fundamental Plane for interacting early-type galaxies.

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