arXiv subjects

P. N. Fedorov

Publications and source records attributed to P. N. Fedorov.

13 recordsLinked to original sources

arXiv2026

Milky Way Near Twins (MWNeTs). I. A Hierarchical Framework for Identifying the Evolutionary Counterparts of the Milky Way

The search for Milky Way (MW) analogues has traditionally relied on similarity in a limited set of present-day global properties, including morphology. However, galaxies with similar current properties may have experienced different assembly histories, secular evolution, nuclear activity, and environmental histories. We introduce Milky Way Near Twins (MWNeTs) as galaxies that resemble the Milky Way in present-day properties and exhibit observational signatures consistent with broadly similar evolutionary pathways. We reformulate the search for the closest extragalactic counterparts of the MW by shifting from parameter-based similarity toward evolutionary similarity. We propose a hierarchical methodology consisting of five stages: isolation and cosmic-web context, morphological and structural constraints, nuclear activity and supermassive black hole properties, global spectrophotometric and dynamical constraints, and advanced evolutionary diagnostics. The first four stages identify galaxies consistent with the present-day environmental, structural, nuclear, spectrophotometric, and dynamical state of the MW, while the fifth stage tests this similarity using independent signatures of comparable evolutionary histories. We introduce the concept of evolutionary memory, in which complementary diagnostics preserve information about physical processes operating on different timescales and probing different layers of galaxy formation and evolution. These diagnostics include the integrated spectral energy distribution, rotation-curve morphology, chemo-dynamical signatures, globular-cluster systems, merger history, circumgalactic-medium properties, and multiwavelength fossil tracers. Together, the MWNeT framework establishes an observational bridge between Galactic and extragalactic astronomy and supports future searches for the closest evolutionary counterparts of the Milky Way.

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arXiv2026

NGC 3521 as the Milky Way near twin: spectral energy distribution from UV to radio decameter ranges

Milky Way analogues (MWAs) are usually selected from structural and kinematic properties, but robust SED-based similarity criteria are limited by heterogeneous photometry and incomplete wavelength coverage. We present a homogeneous, aperture-photometry SED of the Milky Way near-twin NGC~3521 from the ultraviolet to the radio decameter range. Fluxes are measured within a fixed elliptical isophotal aperture using GALEX, SDSS, WISE, Spitzer/MIPS, Herschel/PACS+SPIRE, and VLA data, and supplemented by meter/decameter constraints. We report new observations obtained in Jan-Feb 2022 with the Ukrainian T-shape radio telescope and derive, for the first time, an upper limit in the 24--32~MHz band. The UV-to-decameter SED (27 points) is modelled with \textsc{CIGALE}, including a dedicated low-frequency radio prescription (\texttt{radio_extra}) that accounts for emission and absorption effects. Using ZTF and NEOWISE data (2014--2025), we detect genuine nuclear variability; optical trends at $\sim2^{\prime\prime}$ primarily trace the compact nucleus, while NEOWISE variability reflects a mix of nuclear changes and warm-dust emission within the larger aperture. The preferred fit yields $M_\star \simeq 6.0\times10^{10},M_\odot$, ${\rm SFR}\simeq1.65,M_\odot,{\rm yr}^{-1}$, $M_{\rm dust}\simeq1.3\times10^{8},M_\odot$, and an effective dust temperature of $\sim23$~K. The decameter constraint gives $S_{28,{\rm MHz}}<11.22$~Jy, consistent with expectations for a Milky Way-like system placed at 10.7~Mpc. We conclude that an integrated, homogeneous SED, especially below 100~MHz, provides a complementary diagnostic for identifying and validating MWAs and for interpreting how Milky Way properties would appear to an external observer.

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arXiv2026

Milky Way galaxy-analogs and isolated galaxies with bars: environmental density in the Local Volume

The environmental density of galaxies within the cosmic web constrains their 3D locations in filaments, voids, groups, and clusters. It traces the distribution of baryons and the influence of dark-matter halos on galaxy evolution, and helps diagnose external processes such as supernova and AGN feedback, tidal interactions, ram-pressure stripping, and large-scale flows. We focus on isolated barred galaxies, the parent population that includes Milky Way analogs. To measure local environmental density and verify isolation (|Delta v| <= 500 km s^-1), we built a Python pipeline that works in two redshift regimes: low (z0 < 0.02) and high (z0 >= 0.02). Densities were estimated with k-nearest neighbors and Voronoi tessellations and classified as void (Sigma < 0.05), filament (0.05 <= Sigma < 0.5), group (0.5 <= Sigma < 2.0), and cluster (Sigma >= 2.0). Our northern-sky sample contains 311 isolated barred galaxies from 2MIG plus Milky Way analog systems (z < 0.07). We find 157 void, 84 filament, 27 group, and 11 cluster galaxies; 30 have no detected neighbors. Sixty-seven lie in extremely low-density regions (Sigma_3D < 0.01 gal Mpc^-3), and 22 have the nearest companion beyond 5 Mpc, indicating residence in extended voids. The Milky Way (Sigma_5NN ~ 0.13 gal Mpc^-3, R ~ 2.1 Mpc) and its close analog NGC 3521 both lie in filamentary environments at the edge of a nearby void. For z > 0.02 we identify three additional Milky Way analog candidates from the density metrics: CGCG 208-043 (3D Voronoi) and NGC 5231 and CGCG 047-026 (5th-nearest neighbor). These results show that local environmental density is an effective, physically motivated criterion for selecting Milky Way analogs.

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arXiv2025

Galaxy rotation curve based on RGB stars from the Gaia DR3 catalogue

In this paper, we construct a detailed circular velocity curve of the Milky Way out to 20 kpc based on the radial component of the Jeans equation in cylindrical coordinates, assuming an axisymmetric gravitational potential, and show its dependence on azimuth. We use only Gaia DR3 data and aim to minimize the use of model data and various assumptions. To build the rotation curves, we used a sample of 4,547,980 RGB stars with measured spatial velocities, covering the Galactic plane in the range of Galactocentric cylindrical coordinates $150^\circ < θ< 210^\circ$ and 0 < R < 20 kpc. We exclude systematics in the data that may arise from neglecting higher-order moments of the velocity distribution and their dispersions, as well as due to random measurement errors in Gaia. At the distance of the Sun, the circular velocity $V_{\rm c}(R_0)$ turned out to be ($229.63\pm0.30$) km s$^{-1}$, which is in good agreement with many previous estimates. The average slope of the circular velocity is $(-2.29\pm0.05)$ km s$^{-1}$ kpc$^{-1}$ obtained in the range of $R$ from 6 to 20 kpc and $θ$ from 150 to 210 degrees. The determined circular velocity curve has some peculiarities in behavior near $R\sim$13 and 18 kpc, but in general it does not contradict the results of other authors up to distances where our statistics are reliable.

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arXiv2024

Spatial orientation and shape of the velocity ellipsoids of the Gaia DR3 giants and subgiants in the Galactic plane

We present the results of determining the parameters characterizing the shape and orientation of residual velocity ellipsoids from the Gaia DR3 red giants and subgiants. We show the distribution of velocity dispersions in the Galactic plane obtained from three components of the spatial velocity, as well as the coordinate distribution of the intersection points of the velocity ellipsoid axes with the celestial sphere, in particular the deviations of the longitudes and latitudes of the vertices of stellar regions located within spheres with a radius of 1 kpc centered in the Galactic mid-plane. The area of the Galactic disk under study is in the range of Galactocentric coordinates 0 < R < 15 kpc and $120^\circ < θ< 240^\circ$. We show that the vertex deviations in some regions of the Galactic mid-plane can reach $30^\circ$ in longitude, and $15^\circ$ in latitude. This indicates the presence of kinematic distortions of the stellar velocity field, especially noticeable in the angular range of $150^\circ < θ< 210^\circ$ at a distance of approximately 13 kpc. We propose the angles of deviation of longitudes and latitudes of the ellipsoid axes of residual stellar velocities to be considered as kinematic signatures of various Galactic deformations determined from real fields of spatial velocities. We present the distribution of parameters characterizing the shapes of velocity ellipsoids, as well as their distribution of the semi-axes length ratios. We note a local feature in this distribution and in the distribution of the elongation measurements of the ellipsoids. We perform a comparison of the results obtained from the tensor of deformation velocities and from the observed spatial velocities.

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arXiv2023

Determining the parameters of the spiral arms of the Galaxy from kinematic tracers based on Gaia DR3 data

We present the results of determining the parameters of the spiral arms of the Galaxy using the stars Gaia DR3, whose absolute magnitude is $M_G$ < 4, and which allow tracing spiral arms at large distances from the Sun. As tracers of spiral arms, we use the centroids of stellar spherical regions with a radius of 0.5 kpc, in which the deformation velocities along the coordinate axis R are insignificant. These kinematic tracers cover the Galactic plane within the Galactocentric coordinate ranges 140° < $θ$ < 220° and 4 kpc < R < 14 kpc. The numerical values of the pitch angles of the spirals and their Galactocentric distances to the point of intersection of the spiral with the direction of the Galactic center - the Sun are in good agreement with the results of other authors. By extrapolating beyond the data we have, we present a schematic four-arm global pattern, consisting of the Scutum-Centaurus, Sagitarius-Carina, Perseus, Norma-Outer arms, as well as the local arm Orion. The uncertainties of the determined spiral parameters confirm that the structures identified are not false, but are reliable from the statistical point of view.

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arXiv2023

The vertex coordinates of the Galaxy's stellar systems according to the Gaia DR3 catalogue

We present the results of determining the coordinates of the vertices of various stellar systems, the centroids of which are located in the Galactic plane. To do this, the positions, parallaxes, proper motions, and radial velocities of red giants and subgiants contained in the $Gaia$~DR3 catalogue have been used. When determining the components of the deformation velocity tensors in local coordinate systems, we found the coordinates of the vertices of the stellar systems under study. It turned out that there is a complex dependence of vertex deviations $l_{xy}$ in Galactocentric cylindrical ($R, θ$) and Galactic rectangular ($X,Y$) coordinates. Based on the approach proposed in this paper, heliocentric distances to vertices have been determined for the first time. The results obtained show that in addition to the fact that the angular coordinates of the Galactic center and the vertices of stellar systems do not coincide, their heliocentric distances do not coincide as well. This presumably indicates that there are structures in the Galaxy that noticeably affect its axisymmetry.

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arXiv2022

Mapping the kinematic parameters of the Galaxy from the Gaia EDR3 red giants and sub-giants

We present the results of a kinematic analysis of red giants and subgiants whose centroids are in the plane of our Galaxy. For this, the positions, parallaxes, proper motions, and radial velocities of these stars from the $Gaia$ EDR3 catalog were used. We applied two approaches to obtain kinematic parameters. The first approach -- solving the equations of the Ogorodnikov--Milne model with respect to 12 kinematic parameters -- is generally accepted, but has a number of disadvantages. The second approach developed by us is to find the components of galactocentric centroid's velocity and their partial derivatives with respect to coordinates directly from differential equations for the stellar velocity field. To calculate the kinematic parameters by the methods mentioned above, same stellar samples were used. From these samples spherical regions with a radius of 1 kpc were selected, the centers of which were located strictly in the Galactic mid-plane at the nodes of the coordinate grid ($x_{gal}$, $y_{gal}$) of a rectangular Galactocentric coordinate system with step 100 pc. The region of the Galaxy under study occupies the coordinate interval $115^\circ < θ< 245^\circ$, 0 kpc$ < R < $16 kpc, -1 kpc$ < z < $1 kpc. We show the behavior of local kinematic parameters as well as global parameters such as the circular velocity of stars as a function of galactocentric coordinates. For the first time, the components of centroids' spatial velocities and all their partial derivatives as well as their behavior as a function of galactic coordinates have been derived. The behavior of the $\partial V_R/\partial θ$ and $\partial V_θ/\partial θ$ parameters as a function of galactic coordinates has been derived for the first time.

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arXiv2021

Kinematics of the Milky Way from the Gaia EDR3 red giants and sub-giants

We present the results of the kinematic investigations carried out with the use of spatial velocities of red giants and sub-giants containing in the $Gaia$~EDR3 catalogue. The twelve kinematic parameters of the Ogorodnikov--Milne model have been derived for stellar systems with radii 0.5 and 1.0 kpc, located along the direction the Galactic center -- the Sun -- the Galactic anticenter within the range of Galactocentric distances $R$ 0--8--16~kpc. By combining some of the local parameters the information related to the Galaxy as a whole has been received in the distance range 4--12~kpc, in particular the Galactic rotational curve, its slope, velocity gradients. We show that when using this approach, there is an alternative possibility to infer the behaviour of the Galactic rotational curve and its slope without using the Galactocentric distance $R_\odot$. The kinematic parameters derived within the Solar vicinity of 1~kpc radius are in good agreement with those given in literature.

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arXiv2021

Analysis of modern astrometric catalogues in the Gaia era

We investigate of the systems of proper motions of stars in the ground-based catalogues HSOY, UCAC5, GPS1 and PMA derived by combining with the Gaia DR1 space data. Assuming the systematic differences of stellar proper motions of two catalogues to be caused by the mutual solid-body rotation and glide of the coordinate systems produced by the data of the catalogues under comparison, we analyse the components of the mutual rotation vector and displacement of the origins of these systems. The equatorial components of the vector of mutual rotation velocity of the compared coordinate systems, as well as velocities of the mutual displacement of their origins, varying within the range from 0.2 to 2.9 mas/yr, were derived from a comparison of proper motions of the sources that are common for Gaia EDR3 and the TGAS, UCAC5, HSOY, GPS1 and PMA catalogues, respectively. The systematic errors of proper motions of stars in the HSOY, GPS1, PMA and Gaia EDR3 catalogues in the range of faint stellar magnitudes were estimated by analysing the formal proper motions of extragalactic objects contained in these catalogues. The coordinate system realised by the Gaia EDR3 data at the level of < 0.1 mas/yr is shown to have no rotation and glide relative to the LQAC-5, ALLWISEAGN, Milliquas extragalactis sources within the range from 15 to 21 stellar G magnitude. Among the ground-based catalogues, the system of proper motions of the PMA stars, which is independent of the Gaia EDR3 data, is the closest to the Gaia EDR3 system of proper motions in G magnitude range from 15 to 21.

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arXiv2017

Testing stellar proper motions of the TGAS using data of the HSOY, UCAC5 and PMA catalogues

We present an investigation of stellar proper motions of the TGAS catalogue and ground-based HSOY, UCAC5 and PMA catalogues derived by combining with the Gaia DR1 space data. This investigation concerns with only those stars of ground-based catalogues that are contained in the TGAS. We analyze components of the mutual rotation vector between these systems. It has been found that in all three cases of comparison of the HSOY, UCAC-5 and PMA catalogues with TGAS, the $ω_{y}$ component of the mutual rotation vector depends on magnitude nonlinearly within the range $9.5<m<11.5$, and has an amplitude reaching 1.5 mas/yr. The analysis has shown that the reason causing this effect is presence in proper motions of the Tycho-2-stars containing in the TGAS, of some inexplicable dependency on magnitude. It has been shown that proper motions of the TGAS stars derived using AGIS differ from those derived as a result of application the conventional (classical) method. At the same time, such a difference in proper motions of Hipparcos-stars from TGAS derived by both methods was not found. Investigation of systematic differences between proper motions of the TGAS stars derived by the classical method and proper motions of the HSOY, UCAC5 and PMA stars has shown that the values of the $ω_{y}$ component in this case do not undergo any jumps and do not depend on magnitude. That fact unambiguously indicates that some magnitude error is contained in proper motions of Tycho2-stars derived by the use of AGIS. In the framework of the solid-body rotation model the coordinate systems set by the TGAS catalogue with classical proper motions (on the one hand) and by the HSOY, UCAC5 and PMA catalogues (on the other hand) have mutual rotation with the components along axis less than 0.2-0.3mas/yr.

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arXiv2010

The investigation of absolute proper motions of the XPM Catalogue

The XPM-1.0 is the regular version of the XPM catalogue. In comparison with XPM the astrometric catalogue of about 280 millions stars covering entire sky from -90 to +90 degrees in declination and in the magnitude range 10^m<B<22^m is something improved. The general procedure steps were followed as for XPM, but some of them are now performed on a more sophisticated level. The XPM-1.0 catalogue contains star positions, proper motions, 2MASS and USNO photometry of about 280 millions of the sources. We present some investigations of the absolute proper motions of XPM-1.0 catalogue and also the important information for the users of the catalogue. Unlike previous version, the XPM-1.0 contains the proper motions over the whole sky without gaps. In the fields, which cover the zone of avoidance or which contain less than of 25 galaxies a quasi absolute calibration was performed. The proper motion errors are varying from 3 to 10 mas/yr, depending on a specific field. The zero-point of the absolute proper motion frame (the absolute calibration) was specified with more than 1 million galaxies from 2MASS and USNO-A2.0. The mean formal error of absolute calibration is less than 1 mas/yr.

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arXiv2010

Determining the Orientation Parameters of the ICRS/UCAC2 System Using the Kharkov Catalog of Absolute Stellar Proper Motions

The absolute proper motions of about 275 million stars from the Kharkov XPM catalog have been obtained by comparing their positions in the 2MASS and USNO--A2.0 catalogs with an epoch difference of about 45 yr for northern-hemisphere stars and about 17 yr for southern-hemisphere stars. The zero point of the system of absolute proper motions has been determined using 1.45 million galaxies. The equatorial components of the residual rotation vector of the ICRS/UCAC2 coordinate system relative to the system of extragalactic sources have been determined by comparing the XPM and UCAC2 stellar proper motions: ω_{x,y,z}=(-0.06,0.17,-0.84)+/-(0.15,0.14,0.14) mas yr^{-1}. These parameters have been calculated using about 1 million faintest UCAC2 stars with magnitudes R_{UCAC2}>16^m and J>14^m.7,for which the color and magnitude equation effects are negligible.

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