Relations between abundance characteristics and rotation velocity for star-forming MaNGA galaxies

We derive rotation curves, surface brightness profiles, and oxygen abundance distributions for 147 late-type galaxies using the publicly available spectroscopy obtained by the MaNGA survey. Changes of the central oxygen abundance (O/H)_0, the abundance at the optical radius (O/H)_R25, and the abundance gradient with rotation velocity V_rot are examined for galaxies with rotation velocities from 90 km/s to 350 km/s. We found that each relation shows a break at V_rot^* ~200 km/s. The central (O/H)_0 abundance increases with rising V_rot and the slope of the (O/H)_0 - V_rot relation is steeper for galaxies with V_rot < V_rot^*. The mean scatter of the central abundances around this relation is 0.053 dex. The relation between the abundance at the optical radius of a galaxy and its rotation velocity is similar; the mean scatter in abundances around this relation is 0.081 dex. The radial abundance gradient expressed in dex/kpc flattens with the increase of the rotation velocity. The slope of the relation is very low for galaxies with V_rot > V_rot^*. The abundance gradient expressed in dex/R25 is rougly constant for galaxies with V_rot < V_rot^*, flattens towards V_rot^*, and then again is roughly constant for galaxies with V_rot > V_rot^*. The change of the gradient expressed in terms of dex/h_d (where h_d is the disc scale length) with rotation velocity is similar to that for gradient in dex/R25. The relations between abundance characteristics and other basic parameters (stellar mass, luminosity, and radius) are also considered.Comment: Accepted for publication in the Astronomy and Astrophysic

Breaks in surface brightness profiles and radial abundance gradients in the discs of spiral galaxies

We examine the relation between breaks in the surface brightness profiles and radial abundance gradients within the optical radius in the discs of 134 spiral galaxies from the CALIFA survey. The distribution of the radial abundance (in logarithmic scale) in each galaxy was fitted by simple and broken linear relations. The surface brightness profile was fitted assuming pure and broken exponents for the disc. We find that the maximum absolute difference between the abundances in a disc given by broken and pure linear relations is less than 0.05 dex in the majority of our galaxies and exceeds the scatter in abundances for 26 out of 134 galaxies considered. The scatter in abundances around the broken linear relation is close (within a few percent) to that around the pure linear relation. The breaks in the surface brightness profiles are more prominent. The scatter around the broken exponent in a number of galaxies is lower by a factor of two or more than that around the pure exponent. The shapes of the abundance gradients and surface brightness profiles within the optical radius in a galaxy may be different. A pure exponential surface brightness profile may be accompanied by a broken abundance gradient and vise versa. There is no correlation between the break radii of the abundance gradients and surface brightness profiles. Thus, a break in the surface brightness profile does not need to be accompanied by a break in the abundance gradient.Comment: 18 pages, 17 figures, accepted for publication in A&

Validity of abundances derived from spaxel spectra of the MaNGA survey

We measured the emission lines in the spaxel spectra of MaNGA galaxies in order to determine the abundance distributions therein. It has been suggested that the strength of the low-ionization lines, R_2, N_2, and S_2 may be increased (relative to Balmer lines) in (some) spaxel spectra of the MaNGA survey due to a contribution of the radiation of the diffuse ionized gas. Consequently, the abundances derived from the spaxel spectra through strong-line methods may suffer from large errors. We examined this expectation by comparing the behaviour of the line intensities and the abundances estimated through different calibrations for slit spectra of HII regions in nearby galaxies, for fibre spectra from the SDSS, and for spaxel spectra of the MaNGA survey. We found that the S_2 strength is increased significantly in the fibre and spaxel spectra. The mean enhancement changes with metallicity and can be as large as a factor of 2. The mean distortion of R_2 and N_2 is less than a factor of 1.3. This suggests that Kaufmann et al.'s demarcation line between AGNs and HII regions in the BPT diagram is a useful criterion to reject spectra with significantly distorted strengths of the N_2 and R_2 lines. We find that the three-dimensional R calibration, which uses the N_2 and R_2 lines, produces reliable abundances in the MaNGA galaxies. The one-dimensional N2 calibration produces either reliable or wrong abundances depending on whether excitation and N/O abundance ratio in the target region (spaxel) are close to or differ from those parameters in the calibrating points located close to the calibration relation. We then determined abundance distributions within the optical radii in the discs of 47 MaNGA galaxies. The optical radii of the galaxies were estimated from the surface brightness profiles constructed based on the MaNGA observations.Comment: 19 pages, 15 figures, accepted for publication in A&

Use of long-term models for analysis of comet Encke's motion

© 2016 COSPARThis paper is focused on the problem of the reactive non-gravitational effects change in the cometary motion caused by the comet's activity fading. The modern researches have been reviewed. The necessity of a new model compatible with Marsden's model of non-gravitational forces is shown. Modifications of Marsden's model for the cases in which the main factors of the parameters change are the deposition of the significant non-volatile mass and the growth of the superficial crust are developed. They contain besides the usual Marsden's parameters two and three additional values correspondingly. The developed equations have been used to explain the known change of Marsden's non-gravitational parameters for the comet Encke during 225 years of its observational interval. Although the model with significant non-volatile mass contains less free values, it explains the characteristic features of the comet's non-gravitational parameters behavior better. The model can be further applied for the comet's observed astrometric positions fitting

Use of long-term nongravitational force models for fitting astrometric observations of comet Encke

© 2017 COSPAR Based on the equations derived in (Usanin et al., 2016) a new solution combining the observations of 30 apparitions of the comet Encke from 1911 to 2010 is obtained. For the first time in the worldwide practice the solution is obtained by using converging differential correction of all 60 observed returns of the comet, however, the deviations are still unsatisfactory. The single solution has allowed to draw some preliminary conclusions. The contributions of planetary and nongravitational perturbations to the change of the elements of the orbit during the entire period of observation are determined. The extrapolation of the solution shows that for the past two thousand years the elements of the orbit orientation could change for a half of turnover, which should be taken into account when identifying the comet and associated meteor showers in ancient records. The predictions made by Z. Sekanina and I. Ferrín about oncoming termination of the comet activity are confirmed

Use of an Analytical Theory for the Physical Libration of the Moon to Detect Free Nutation of the Lunar Core

© 2018, Pleiades Publishing, Ltd. A brief review of modern observational achievements and the theoretical basis of physical libration of the Moon is presented. Special attention is given to the inferred existence of a lunar core and determination of its parameters. The creation of a theory of physical libration of the Moon, which requires analyses of semi-empirical series of long-term laser observations and the use of the highly accurate DE421 dynamical ephemeris, is related to this. A large role in this area has been played by the analytical theory of physical libration of the Moon constructed by Yu.V. Barkin, which made it possible for the first time to derive parameters of the free nutation of the lunar core from observations. This paper is based on a talk given at the conference “Modern Astrometry 2017,” dedicated to the memory of K.V. Kuimov (Sternberg Astronomical Institute, Moscow State University, October 23–25, 2017)

Cataloque of selenocentric referense obgects (CSRO): database

This database provides a global selenocentric catalogue containing 272 931 coordinates of selenocentric positions reference objects. The selenocentric coordinate network was made in a dynamic system of coordinates. In catalogue are given rectangular coordinates and radius - vector craters. The catalog is intended for undergraduate and graduate students of all disciplines studying the celestial mechanics and astrometry. It will be useful to teachers and researchers interested in issues the navigational orientation on the lunar surface to

The fractal analysis of the gravitational field and topography of the Mars

The aim of this paper is to represent the results of a structured fractal analysis of gravitational and topographical parameters of Mars on the basis of data obtained from the space missions. To analyze Martian fractal structures the observations from the data received from boards of the space missions including «Mars Global Surveyor" has been used. The models of relief and Mars gravitational field have been constructed on the basis of harmonic analysis of the expansion in spherical functions of the satellite observations data. As a result, fractal dimensions of Martian reliefs anomalies and Mars gravitational potential by longitude and latitude have been determined. Mean values of the fractal dimensions D have been obtained as well: mean fractal dimensions of Martian topographic model by latitude D = 0.86, by longitude D = 0.88; mean fractal dimensions of Martian gravitational potential anomalies by latitude D = 1.06, by longitude D = 1.092

Analysis of the terrestrial global digital model using fractal geometry and harmonic expansion into spherical functions

© 2018 by IOP Publishing Ltd. During the implementation of space missions on study of the Solar system a large amount of information on planets geophysics and their morphological properties has been obtained, that could be investigated using fractal geometry. The present paper describes the analysis of the GDEM terrestrial digital model built from the ASTER's observations. GDEM is global digital elevation model and ASTER is advanced spaceborne thermal emission and reflection radiometer. ASTER was installed on the platform of Terra (NASA) orbiter. In our study we used robust methods and fractal analysis. The fractal dimension values for the terrestrial surface, which has a heterogeneous structure, are obtained. The fractal dimensions are determined for geographical latitudes. Independent estimates of the Earth's macrostructure that could be used for a new interpretation of geophysical processes have been obtained as well

The method for celestial bodies' center of mass position relative to their figures determination on the basis of harmonic analysis of the expansion in spherical functions in order to refine the physical libration parameters

© Published under licence by IOP Publishing Ltd. In this paper the problem of the lunar center of mass relative to the center of its figure determination on the basis of space observations is considered, since the Moon is the most studied celestial object and there is a complete database on it. The future prospects for lunar laser ranging and radio interferometry require development of adequate theoretical support for modern technologies. The aim of these studies is the distances' measurement between the Moon and the Earth with an accuracy of 1 mm. Thus, determination of the lunar center of mass position, represented in this paper, and development of the selenocentric system will allow to solve the above mentioned problem more accurately and reliably. The new values of the lunar center of mass relative to its center of figure in orthogonal selenographic coordinate system Δξ, Δη, Δζ have been determined; they are: -1.75, -0.75, 0.11 km respectively