527 research outputs found
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.Comment: Poster presented at JENAM-2000 (Joint European and National
Astronomical meeting - S02. Morphology and dynamics of stellar systems: star
clusters, galactic arms and rings
Simultaneous spectra and radio properties of BL Lac's
We present the results of nine years of the blazar observing programme at the
RATAN-600 radio telescope (2005-2014). The data were obtained at six frequency
bands (1.1, 2.3, 4.8, 7.7, 11.2, 21.7 GHz) for 290 blazars, mostly BL Lacs. In
addition, we used data at 37 GHz obtained quasi-simultaneously with the
Metsahovi radio observatory for some sources. The sample includes blazars of
three types: high-synchrotron peaked (HSP), low-synchrotron peaked (LSP), and
intermediate-synchrotron peaked (ISP). We present several epochs of flux
density measurements, simultaneous radio spectra, spectral indices and
properties of their variability. The analysis of the radio properties of
different classes of blazars showed that LSP and HSP BL Lac blazars are quite
different objects on average. LSPs have higher flux densities, flatter spectra
and their variability increases as higher frequencies are considered. On the
other hand, HSPs are very faint in radio domain, tend to have steep low
frequency spectra, and they are less variable than LSPs at all frequencies.
Another result is spectral flattening above 7.7 GHz detected in HSPs, while an
average LSP spectrum typically remains flat at both the low and high frequency
ranges we considered.Comment: 14 pages, 6 figures. Accepted for publication in Astronomische
Nachrichte
Modulation of Circumstellar Extinction in a Young Binary System with a Low-Mass Companion in a Noncoplanar Orbit
The cyclic activity model of a young star with the low-mass secondary
component (q = M2/M1 <= 0.1) accreting a matter from circumbinary disk is
considered. It is assumed that the orbit is circular and the disk and orbital
planes are non-coplanar. Sets of hydrodynamics models of such a system have
been calculated by the SPH method and then the variations of the circumstellar
extinction and phase light curves were determined. The calculations showed that
depending on the model parameters and orientation of the system in regards to
an observer the different in shape and amplitude light curves can be observed.
An important property of the considered models is also the dependence of the
mass accretion rate onto the components on the phase of the orbital period. The
results of the calculation can be used for analysis of the cyclic activity of
UX Ori stars and young stars with the long-lasting eclipses.Comment: 14 pages, 7 figure
Estimating the Dark Halo Mass from the Relative Thickness of Stellar Disks
We analyze the relationship between the mass of a spherical component and the
minimum possible thickness of stable stellar disks. This relationship for real
galaxies allows the lower limit on the dark halo mass to be estimated (the
thinner the stable stellar disk is, the more massive the dark halo must be). In
our analysis, we use both theoretical relations and numerical N-body
simulations of the dynamical evolution of thin disks in the presence of
spherical components with different density profiles and different masses. We
conclude that the theoretical relationship between the thickness of disk
galaxies and the mass of their spherical components is a lower envelope for the
model data points. We recommend using this theoretical relationship to estimate
the lower limit for the dark halo mass in galaxies. The estimate obtained turns
out to be weak. Even for the thinnest galaxies, the dark halo mass within four
exponential disk scale lengths must be more than one stellar disk mass.Comment: 20 pages including 6 figures. To be published in Astronomy Letters
(v. 32, No. 10, pp. 649-660, 2006
RATAN-600 multi-frequency data for the BL Lacertae objects
We present a new catalogue of the RATAN-600 multi-frequency measurements for BL Lac objects. The purpose of this catalogue is to compile the BL Lac multi-frequency data that is acquired with the RATAN-600 simultaneously at several frequencies. The BL Lac objects emit a strongly variable and polarized non-thermal radiation across the entire electromagnetic spectrum from radio to gamma rays and represent about 1% of known AGNs. They belong to the blazar population and differ from other blazars' featureless optical spectrum, which sometimes have absorption lines, or have weak and narrow emission lines. One of the most effective ways of studying the physics of BL Lacs is the use of simultaneous multi-frequency data.
The multi-frequency broadband radio spectrum was obtained simultaneously with an accuracy of up to 1-2 min for four to six frequencies: 1.1, 2.3, 4.8, 7.7, 11.2, and 21.7 GHz. The catalogue is based on the RATAN-600 observations and on the data from: equatorial coordinate and redshift, R-band magnitude, synchrotron peak frequency, SED classes, and object type literature.
The present version of the catalogue contains RATAN-600 flux densities measurements over nine years (2006-2014), radio spectra at different epochs, and their parameters of the catalogue for more than 300 BL Lacs objects and candidates. The BL Lacs list is constantly updated with new observational data of RATAN-600.</p
Theoretical and methodological approaches to the preservation and strengthening of health of children by means of rhythmic gymnastics
The article refers to the preservation and strengthening of health of children by means of rhythmic gymnastics, its beneficial effects on the body when performing exercises with rope and HoopВ статье говорится о сохранении и укреплении здоровья детей по средствам художественной гимнастики, о ее полезном влиянии на организм при выполнении упражнений со скакалкой и обруче
An Iterative Method for Constructing Equilibrium Phase Models of Stellar Systems
We present a new method for constructing equilibrium phase models for stellar
systems, which we call the iterative method. It relies on constrained, or
guided evolution, so that the equilibrium solution has a number of desired
parameters and/or constraints. This method is very powerful, to a large extent
due to its simplicity. It can be used for mass distributions with an arbitrary
geometry and a large variety of kinematical constraints. We present several
examples illustrating it. Applications of this method include the creation of
initial conditions for N-body simulations and the modelling of galaxies from
their photometric and kinematic observations.Comment: 14 pages, 13 figures, Accepted for publication in MNRA
37 GHz observations of narrow-line Seyfert 1 galaxies
Observations at 37 GHz, performed at Mets\"ahovi Radio Observatory, are
presented for a sample of 78 radio-loud and radio-quiet narrow-line Seyfert 1
(NLS1) galaxies, together with additional lower and higher frequency radio data
from RATAN-600, Owens Valley Radio Observatory, and the Planck satellite. Most
of the data have been gathered between February 2012 and April 2015 but for
some sources even longer lightcurves exist. The detection rate at 37 GHz is
around 19%, comparable to other populations of active galactic nuclei presumed
to be faint at radio frequencies, such as BL Lac objects. Variability and
spectral indices are determined for sources with enough detections. Based on
the radio data, many NLS1 galaxies show a blazar-like radio spectra exhibiting
significant variability. The spectra at a given time are often inverted or
convex. The source of the high-frequency radio emission in NLS1 galaxies,
detected at 37 GHz, is most probably a relativistic jet rather than star
formation. Jets in NLS1 galaxies are therefore expected to be a much more
common phenomenon than earlier assumed.Comment: Accepted for publication in A&A. Table of 37 GHz data will be
available at the CDS soo
Optoelectronic Methods of IR-Photometry in Solving Thermal and Physical Problems
Results of the application of optoelectronic IR-photometry methods for solving the actual thermophysical problems using high-speed photodiode temperature (pyrometric) sensors are presented. The latest achievements of the Ioffe Institute in the field of middle IR spectral range (3-6 μm) photodiode production technology are used in the sensor development. The above-mentioned middle-IR photodiode sensors are based on heterostructures from A3B5 solid solutions and they do not require forced cooling. New data on thermophysical processes taking place under the complex experimental conditions, including dynamically changing properties of the object, have been obtained. The new experimental results are based on high-speed non-contact measurements of the absolute temperature of objects directly in the exposure region of laser radiation and / or powerful electromagnetic fields. In the context of creating new experimental techniques for determining the thermophysical parameters of new promising materials the efficiency of middle- IR photodiode temperature sensors has been shown. In particular, a simple and effective measuring method for determining the heat transfer coefficient of solid objects and the pyroelectric coefficient of ferro- and pyroelectric materials is offered. The measuring method is based on laser thermowave techniques and direct noncontact measurements of the sample surface temperature under the pulsed / periodic laser action. The proposed experimental techniques make it possible to significantly improve the accuracy of measurements of thermophysical parameters of materials, and in particular, to eliminate a considerable spread of data on the parameters of the pyroelectric effect in ferroelectric materials.
Keywords: Pyrometric sensors, mid-IR photodiodes, laser thermowave techniques, heat transfer coefficient, pyroelectric coefficien
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