Elena V. Glushkova

The Luminosity Function of the Milky Way Satellites

We quantify the detectability of stellar Milky Way satellites in the Sloan Digital Sky Survey (SDSS) Data Release 5. We show that the effective search volumes for the recently discovered SDSS–satellites depend strongly on their luminosity, with their maximum distance, Dmax, substantially smaller than the Milky Way halo’s virial radius. Calculating the maximum accessible volume, Vmax, for all faint detected satellites, allows the calculation of the luminosity function for Milky Way satellite galaxies, accounting quantitatively for their detectability. We find that the number density of satellite galaxies continues to rise towards low luminosities, but may flatten at MV ∼ −5; within the uncertainties, the luminosity function can be described by a single power law dN/dMV = 10 × 10 0.1(M V +5) , spanning luminosities from MV = −2 all the way to the luminosity of the Large Magellanic Cloud. Comparing these results to several semi-analytic galaxy formation models, we find that their predictions differ significantly from the data: either the shape of the luminosity function, or the surface brightness distributions of the models, do not match. Subject headings: Galaxy: halo – Galaxy: structure – Galaxy: formation – Local Group

Automated search for Galactic star clusters in large multiband surveys - I. Discovery of 15 new open clusters in the Galactic anticenter region

Aims. According to some estimations, there are as many as 100 000 open clusters in the Galaxy, but less than 2000 of them have been discovered, measured, and cataloged. We plan to undertake data mining of multiwavelength surveys to find new star clusters. Methods. We have developed a new method to search automatically for star clusters in very large stellar catalogs, which is based on convolution with density functions. We have applied this method to a subset of the Two Micron All Sky Survey catalog toward the Galactic anticenter. We also developed a method to verify whether detected stellar groups are real star clusters, which tests whether the stars that form the spatial density peak also fall onto a single isochrone in the color–magnitude diagram. By fitting an isochrone to the data, we estimate at the same time the main physical parameters of a cluster: age, distance, color excess. Results. For the present paper, we carried out a detailed analysis of 88 overdensity peaks detected in a field of 16 × 16 degrees near the Galactic anticenter. From this analysis, 15 overdensities were confirmed to be new open clusters and the physical and structural parameters were determined for 12 of them; 10 of them were previously suspected to be open clusters by Kronberger (2006) and Froebrich (2007). The properties were also determined for 13 yet-unstudied known open clusters, thus almost tripling the sample of open clusters with studied parameters in the anticenter. The parameters determined with this method showed a good agreement with published data for a set of well-known clusters.

Automated search for star clusters in large multiband surveys: II. Discovery and investigation of open clusters in the Galactic plane

Automated search for star clusters in J, H, Ks data from 2MASS catalog has been performed using the method developed by Koposov et al. (2008). We have found and verified 153 new clusters in the interval of the galactic latitude −24° < b < 24°. Color excesses E(B − V), distance moduli and ages were determined for 130 new and 14 yet-unstudied known clusters. In this paper, we publish a catalog of coordinates, diameters, and main parameters of all the clusters under study. A special web-site available at http://ocl.sai.msu.ru has been developed to facilitate dissemination and scientific usage of the results.

Red giants in open clusters X. NGC 1817

Radial-velocity and BV CCD observations of 29 red-giant candidates in the central part of the intermediate-age open cluster NGC 1817 have confirmed the membership of 21 stars. In addition, we have used radial velocities and new UBVR photoelectric photometry toinvestigate the membership of 59 new candidates located inan outer corona surrounding NGC 1817, identified from the POSS plates. We have confirmed 18 new members out to a distance of 27 � from the centre, thus doubling the previous cluster radius. Ten definite spectroscopic-binary members have been discovered, corresponding to a binary frequency of 25.6% and four orbits have been determined so far. Three additional stars have been identified as possible spectroscopic- binary members. We derive a cluster mean velocity of +65.33 ± 0.09 (0.52 s.e.) kms −1 based on 29 members with no detected velocity variations plus the 3 binary members with orbital solutions. The radial distribution of the 39 red-giant members shows a strong concentration of spectroscopic binaries in the inner part of the cluster, similar to that observed in M 67, although NGC 1817 is much younger.

Classical Cepheids and the spiral structure of the milky way

We use data on space distribution of the currently most complete sample of Cepheids with reliable distances (565 stars), located within ~5 kpc from the Sun, to study the spiral pattern of the Milky Way galaxy. We estimate the pitch angle as 9°−10°; the most accurate estimate, i = 9.5° ± 0.1°, was obtained assuming the existence of a global four-armed spiral pattern; the solar phase angle in the spiral pattern is χ⊙ = −121° ± 3°. Comparing positions of the spiral arms delineated by classical Cepheids and galactic masers, with the age difference of these objects in mind, we estimate the rotation angular speed of the spiral pattern to be ΩP = 25.2 ± 0.5 km s−1kpc−1.

Photometric study of open clusters Berkeley 96, Berkeley 97, King 12, NGC 7261, NGC 7296 and NGC 7788

We present BV RcIc CCD photometry in the fields of six Galactic open clusters toward the Perseus spiral arm. These data, complemented with J, H, and KS magnitudes from 2MASS, have been used to determine the ages, distances, and colour excesses E(B V ) for these clusters: 40 Myr, 3180 +440 380 pc, 0.54±0.03 mag (Berkeley 96); 250 Myr, 2410 +220 200 pc, 0.77±0.06 mag (Berkeley 97); 70 Myr, 2490 +180 170 pc, 0.51±0.05 mag (King 12); 160 Myr, 2830 +160 150 pc, 0.88 ± 0.09 mag (NGC 7261); 280 Myr, 2450 +190 170 pc, 0.24 ± 0.03 mag (NGC 7296); and 160 Myr, 2750 +220 210 pc, 0.49 ± 0.02 mag (NGC 7788). We found gaps in the mass function of clusters Be 97, King 12, and NGC 7788 in the mass intervals of [1.3–1.5], [1.4–1.6], and [1.5–1.7] solar masses, respectively.

Photometry of the poorly studied galactic open star clusters King 13, King 18, King 19, King 20, NGC 136, and NGC 7245

We present the results of our BV RcIc CCD photometry for six Galactic open star clusters toward the Perseus spiral armperformed at the Special Astrophysical Observatory of the Russian Academy of Sciences. Based on these data and using JHKs photometry from the 2MASS catalog, we have determined the ages, distances, and color excesses for the clusters: 710 Myr, 2960−340+400 pc, 0·m56 ± 0·m04 (King 13); 130 Myr, 3010−280+300 pc, 0·m69 ± 0·m04 (King 18); 560 Myr, 2630−270+310 pc, 0·m69 ± 0·m08 (King 19); 160 Myr, 1750−70+80 pc, 0·m77 ± 0·m05 (King 20); 250 Myr, 5220−320+350 pc, 0·m70 ± 0·m09 (NGC 136); 320 Myr, 3390−200+210 pc, 0·m43 ± 0·m03 (NGC 7245).

Globular Clusters: Absolute Proper Motions and Galactic Orbits

We cross-match objects from several different astronomical catalogs to determine the absolute proper motions of stars within the 30-arcmin radius fields of 115 Milky-Way globular clusters with the accuracy of 1–2 mas yr−1. The proper motions are based on positional data recovered from the USNO-B1, 2MASS, URAT1, ALLWISE, UCAC5, and Gaia DR1 surveys with up to ten positions spanning an epoch difference of up to about 65 years, and reduced to Gaia DR1 TGAS frame using UCAC5 as the reference catalog. Cluster members are photometrically identified by selecting horizontal- and red-giant branch stars on color–magnitude diagrams, and the mean absolute proper motions of the clusters with a typical formal error of about 0.4 mas yr−1 are computed by averaging the proper motions of selected members. The inferred absolute proper motions of clusters are combined with available radial-velocity data and heliocentric distance estimates to compute the cluster orbits in terms of the Galactic potential models based on Miyamoto and Nagai disk, Hernquist spheroid, and modified isothermal dark-matter halo (axisymmetric model without a bar) and the same model + rotating Ferre’s bar (non-axisymmetric). Five distant clusters have higher-than-escape velocities, most likely due to large errors of computed transversal velocities, whereas the computed orbits of all other clusters remain bound to the Galaxy. Unlike previously published results, we find the bar to affect substantially the orbits of most of the clusters, even those at large Galactocentric distances, bringing appreciable chaotization, especially in the portions of the orbits close to the Galactic center, and stretching out the orbits of some of the thick-disk clusters.

Investigation of open clusters based on IPHAS and APASS survey data

We adapt the classical Q-method based on a reddening-free parameter constructed from three passband magnitudes to thwe filter set of IPHAS survey and combine it with the maximum-likelihood-based cluster parameter estimator by Naylor and Jeffries (2006) to determine the extinction, heliocentric distances, and ages of young open clusters using Halpha and ri data. Themethod is also adapted for the case of signific ant variations of extinction across the cluster rfield. Our technique is validated by comparing the colour excesses, disdtances, and ages determined in this study with the most bona fide values reported for the 18 well-studied young open clusters in the past, and a fairly good agreement is found between our extinction and distance estimnates and earlier published results. although our age estimates are not very consistent with those published by other authors. We also show that individual extinction values can be determined rather accurately for stars with (r-i)0>0.1. Our results open up a prospect fpr determining a uniform set of parameters for northern clusters based on homogeneous photometric data, and for searching for new, hitherto undiscovered open clusters.

Search for and investigation of new stellar clusters using the data from huge stellar catalogues

We present new automatic methods of search for star clusters using the data available in new huge stellar catalogues. Using 2MASS catalogue we have discovered over ten new open clusters in the region of Galaxy anticenter and determined their physical parameters.G01 New evidence for a connection between massive black holes and ULX G02 Long-Term Evolution of Massive Black Hole Binaries G03 NBODY Meets Stellar Population Synthesis G04 N-body modelling of real globular star clusters G05 Fokker-Planck rotating models of globular clusters with black hole G06 Observational Manifestation of chaos in spiral galaxies: quantitative analysis and qualitative explanation G07 GRAPE Clusters: Beyond the Million-Body Problem G08 Orbital decay of star clusters and Massive Black Holes in cuspy galactic nuclei G09 An Edge-on Disk Galaxy Catalog G10 Complexes of open clusters in the Solar neighborhood G11 Search for and investigation of new stellar clusters using the data from huge stellar catalogues G12 Computing 2D images of 3D galactic disk models G13 Outer Pseudoring in the Galaxy G14 Where are tidal-dwarf galaxies? G15 Ultra compact dwarf galaxies in nearby clusters G16 Impact of an Accretion Disk on the Structure of a stellar cluster in active galactic nuclei G17 Order and Chaos in the edge-on profiles of disk galaxies G18 On the stability of OB-star configurations in the Orion Nebula cluster G19 Older stars captured in young star clusters by cloud collapse G20 General features of the population of open clusters within 1 kpc from the Sun G21 Unstable modes in thin stellar disks G22 From Newton to Einstein – Dynamics of N-body systems G23 On the relation between the maximum stellar mass and the star cluster mass