arXiv subjects

Dmitry Makarov

Publications and source records attributed to Dmitry Makarov.

At least 37 records · Page 2Linked to original sources

arXiv2021

The local environment of flat galaxies

The existence of flat or bulgeless galaxies poses a challenge to the hierarchical structure formation scenario advocated by modern cosmology. We determine the geometrical environment of a sample of $315$ flat galaxies from the Revised Flat Galaxy Catalog (RFGC) using `local dimension' $D$, which, on a given length scale, quantifies the dimension of the cosmic structure in which a galaxy is embedded. For galaxies residing in filaments, nodes and sheets, $D \sim 1$, $D \sim 1.5$ and $D \sim 2$ respectively; $D \sim 3$ represents field galaxies. We also determine the local dimensions of a sample of 15,622 non-flat galaxies identified in the Galaxy Zoo project from the Sloan Digital Sky Survey (SDSS). We find that the median values of $D$ for the flat and the non-flat galaxies are $2.2$ and $1.8$ respectively, implying that flat galaxies are located in a relatively sparser environment compared to non-flat galaxies; a Kolmogorov-Smirnov (KS) test indicates that their geometrical environments are different at $>99$\% confidence level. Further, using a group finding algorithm, we study the local environment of a subset of $779$ flat galaxies with major-to-minor axes ratio $a/b >10$ identified as superthin galaxies. We find that the median clusterization index $k_{\rm{min}}$ for superthin flat galaxies $\sim$ $2.3$ while $\sim$ $1.7$ for other flat galaxies, confirming that the superthins reside in an under-dense environment compared to other flat galaxies at $> 98 \%$ confidence level. Our results may therefore have important implications for the formation and evolution models of flat galaxies in the universe.

astro-ph.GA↗

arXiv2021

Tracing satellite planes in the Sculptor group: I. Discovery of three faint dwarf galaxies around NGC 253

In the last years, a new generation of large-scale imaging surveys have probed wide field regions around some nearby galaxies at unprecedented low surface brightness regime (~28.0-29.0 mag arcsec^-2). This offers a chance of discovering very faint dwarf satellites by means of visual inspection of these public deep images. We report the first results of a systematic survey of faint dwarf spheroidal galaxies in the vicinity of the bright late-type spiral NGC 253 galaxy by means of a visual inspection of the images taken by the Dark Energy Survey. Three new dwarf galaxies have been discovered in the vicinity of the brightest member of the Sculptor filament, the late-type spiral NGC 253. Assuming they are companions of NGC 253, their total absolute V-magnitudes fall in the -7 to -9 mag range, which is typical for dwarf satellites in the local Universe. The central surface brightness tend to be extremely low for all the discovered dwarfs and fall roughly in the range of 25-26 mag arcsec^-2 in g-band. Using known data on distances and velocities of galaxies, we estimate the total virial mass of the NGC 253 group to be 8 x 10^11 Mo, which gives the virial radius R_200 = 186 kpc and the turn-around radius of 706 kpc. We also discuss the possible existence of a spatially flattened and velocity-correlated satellite system around NGC 253. This large-scale structure is orientated almost edge-on to line of sight. The possible plane of satellites is only 31 kpc thick with the minor-to-major axis ratio of 0.14. Four out of five galaxies with measured velocities follow a common velocity trend similar to those observed in the planes of satellites around the Andromeda and Centaurus A galaxies. However, the small number of galaxies with known velocities prevents to reach a definitive conclusion about the formation scenario of the structure and its possible relation to the surrounding cosmic web.

astro-ph.GA↗

arXiv2019

Combining Safe Interval Path Planning and Constrained Path Following Control: Preliminary Results

We study the navigation problem for a robot moving amidst static and dynamic obstacles and rely on a hierarchical approach to solve it. First, the reference trajectory is planned by the safe interval path planning algorithm that is capable of handling any-angle translations and rotations. Second, the path following problem is treated as the constrained control problem and the original flatness-based approach is proposed to generate control. We suggest a few enhancements for the path planning algorithm aimed at finding trajectories that are more likely to be followed by a robot without collisions. Results of the conducted experimental evaluation show that the number of successfully solved navigation instances significantly increases when using the suggested techniques.

cs.RO↗

arXiv2018

Mirach's Goblin: Discovery of a dwarf spheroidal galaxy behind the Andromeda galaxy

It is of broad interest for galaxy formation theory to carry out a full inventory of the numbers and properties of dwarf galaxies in the Local Volume, both satellites and isolated ones. Ultra-deep imaging in wide areas of the sky with small amateur telescopes can help to complete the census of these hitherto unknown low surface brightness galaxies, which cannot be detected by the current resolved stellar population and HI surveys. We report the discovery of Donatiello I, a dwarf spheroidal galaxy located one degree from the star Mirach (Beta And) in a deep image taken with an amateur telescope. The color--magnitude diagram obtained from follow-up observations obtained with the Gran Telescopio Canarias (La Palma, Spain) reveals that this system is beyond the Local Group and is mainly composed of old stars. The absence of young stars and HI emission in the ALFALFA survey are typical of quenched dwarf galaxies. Our photometry suggests a distance modulus for this galaxy of (m-M)=27.6 +/- 0.2 (3.3 Mpc), although this distance cannot yet be established securely owing to the crowding effects in our color--magnitude diagram. At this distance, Donatiello I's absolute magnitude (M_v =-8.3), surface brightness (mu_v=26.5 mag arcsec^-2) and stellar content are similar to the "classical" Milky Way companions Draco or Ursa Minor. The projected position and distance of Donatiello I are consistent with being a dwarf satellite of the closest S0-type galaxy NGC 404 ("Mirach's Ghost"). Alternatively, it could be one of the most isolated quenched dwarf galaxies reported so far behind the Andromeda galaxy.

astro-ph.GA↗

arXiv2018

Mass modelling of a superthin galaxy, FGC1540

We present high resolution H{\sc i} 21cm Giant Meterwave Radio Telescope (GMRT) observations of the superthin galaxy FGC1540 with a spatial resolution of 10$''$ $\times$ 8$''$ and a spectral resolution of 1.73 kms$^{-1}$ and an rms noise of 0.9 mJy per beam. We obtain its rotation curve as well as deprojected radial H{\sc i} surface density profile by fitting a 3-dimensional tilted ring model directly to the H{\sc i} data cubes by using the publicly-available software, Fully Automated Tirrific (FAT). We also present the rotation curve of FGC1540 derived from its optical spectroscopy study using the 6-m BTA telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. We use the rotation curve, the H{\sc i} surface density profile together with Spitzer 3.6 $μ$m and the SDSS $i$--band data to construct the mass models for FGC1540. We find that both the Pseudo-isothermal (PIS), as well as Navarro-Frenk-White (NFW) dark matter (DM) halos, fit the observed rotation curve equally well. The PIS model indicates a compact dark matter halo ($R_{\rm C}/R_{\rm D}$ < 2), with the best-fitting core radius ($R_{\rm C}$) approximately half the exponential stellar disc scale length ($R_{\rm D}$), which is in agreement with the mass models of superthin galaxies studied earlier in the literature. Since the vertical thickness of the galactic stellar disc is determined by a balance between the net gravitational field and the velocity dispersion in the vertical direction, the compact dark matter halo may be primarily responsible in regulating the superthin vertical structure of the stellar disc in FGC1540 as was found in case of the superthin galaxy UGC7321.

astro-ph.GA↗

arXiv2017

Coupled harmonic oscillators and their quantum entanglement

A system of two coupled quantum harmonic oscillators with the Hamiltonian ${\hat H}=\frac{1}{2}\left(\frac{1}{m_1}{\hat p}^{2}_1 + \frac{1}{m_2}{\hat p}^{2}_2+A x^2_1+B x^2_2+ C x_1 x_2\right)$ can be found in many applications of quantum and nonlinear physics, molecular chemistry, and biophysics. The stationary wave function of such a system is known, but its use for the analysis of quantum entanglement is complicated because of the complexity of computing the Schmidt modes. Moreover, there is no exact analytical solution to the nonstationary Schrodinger equation ${\hat H}Ψ=i\hbar\frac{\partial Ψ}{\partial t}$ and Schmidt modes for such a dynamic system. In this paper we find a solution to the nonstationary Schrodinger equation; we also find in an analytical form a solution to the Schmidt mode for both stationary and dynamic problems. On the basis of the Schmidt modes, the quantum entanglement of the system under consideration is analyzed. It is shown that for certain parameters of the system, quantum entanglement can be very large.

quant-ph↗

arXiv2017

Quantum entanglement of a harmonic oscillator in an electromagnetic field

At present, there are many methods of quantum entanglement of particles with an electromagnetic field. Most methods have a low probability of quantum entanglement and not an exact theoretical apparatus based on an approximate solution of the Schrodinger equation. There is a need for new methods for obtaining quantum-entangled particles and mathematically accurate studies of such methods. In this paper, a quantum harmonic oscillator (for example, an electron in a magnetic field) interacting with a quantized electromagnetic field is considered. Based on the exact solution of the Schrodinger equation for this system, it is shown that for certain parameters there can be a large quantum entanglement between the electron and the electromagnetic field. Quantum entanglement is analyzed on the basis of a mathematically exact expression for the Schmidt modes and the Von Neumann entropy.

quant-ph↗

arXiv2016

Abundance of Field Galaxies

We present new measurements of the abundance of galaxies with a given circular velocity in the Local Volume: a region centered on the Milky Way Galaxy and extending to distance 10Mpc. The sample of 750 mostly dwarf galaxies provides a unique opportunity to study the abundance and properties of galaxies down to absolute magnitudes MB= -10, and virial masses Mvir= 1e9Msun. We find that the standard LCDM model gives remarkably accurate estimates for the velocity function of galaxies with circular velocities V>60kms and corresponding virial masses Mvir> 3e10Msun, but it badly fails by over-predicting 5 times the abundance of large dwarfs with velocities V= 30-50kms. The Warm Dark Matter models cannot explain the data either, regardless of mass of the WDM particle. Just as in previous observational studies, we find a shallow asymptotic slope dN/dlog V = V**alpha, alpha =-1 of the velocity function, which is inconsistent with the standard LCDM model that predicts the slope alpha =-3. Though reminiscent to the known overabundance of satellites problem, the overabundance of field galaxies is a much more difficult problem. For the LCDM model to survive, in the 10Mpc radius of the Milky Way there should be 1000 dark galaxies with virial mass Mvir= 1e10Msun, extremely low surface brightness and no detectable HI gas. So far none of this type of galaxies have been discovered.

astro-ph.CO↗

arXiv2014

HyperLEDA. III. The catalogue of extragalactic distances

We present the compilation catalogue of redshift-independent distances included in the HyperLEDA database. It is actively maintained to be up-to-date, and the current version counts 6640 distance measurements for 2335 galaxies compiled from 430 published articles. Each individual series is recalibrated onto a common distance scale based on a carefully selected set of high-quality measurements. This information together with data on HI line-width, central velocity dispersion, magnitudes, diameters, and redshift is used to derive a homogeneous distance estimate and physical properties of galaxies, such as their absolute magnitudes and intrinsic size.

astro-ph.GA↗

arXiv2013

Cosmicflows-2: The Data

Cosmicflows-2 is a compilation of distances and peculiar velocities for over 8000 galaxies. Numerically the largest contributions come from the luminosity-linewidth correlation for spirals, the TFR, and the related Fundamental Plane relation for E/S0 systems, but over 1000 distances are contributed by methods that provide more accurate individual distances: Cepheid, Tip of the Red Giant Branch, Surface Brightness Fluctuation, SNIa, and several miscellaneous but accurate procedures. Our collaboration is making important contributions to two of these inputs: Tip of the Red Giant Branch and TFR. A large body of new distance material is presented. In addition, an effort is made to assure that all the contributions, our own and those from the literature, are on the same scale. Overall, the distances are found to be compatible with a Hubble Constant H_0 = 74.4 +-3.0 km/s/Mpc. The great interest going forward with this data set will be with velocity field studies. Cosmicflows-2 is characterized by a great density and high accuracy of distance measures locally, falling to sparse and coarse sampling extending to z=0.1.

astro-ph.CO↗

arXiv2012

A unique isolated dwarf spheroidal galaxy at D=1.9 Mpc

We present a photometric and spectroscopic study of the unique isolated nearby dSph galaxy KKR25. The galaxy was resolved into stars with HST/WFPC2 including old red giant branch and red clump. We have constructed a model of the resolved stellar populations and measured the star formation rate and metallicity as function of time. The main star formation activity period occurred about 12.6 to 13.7 Gyr ago. These stars are mostly metal-poor, with a mean metallicity [Fe/H]\sim -1 to -1.6 dex. About 60 per cent of the total stellar mass was formed during this event. There are indications of intermediate age star formation in KKR25 between 1 and 4 Gyr with no significant signs of metal enrichment for these stars. Long-slit spectroscopy was carried out using the Russian 6-m telescope of the integrated starlight and bright individual objects in the galaxy. We have discovered a planetary nebula (PN) in KKR25. This is the first known PN in a dwarf spheroidal galaxy outside the Local Group. We have measured its oxygen abundance 12+log(O/H)=7.60+-0.07 dex and a radial velocity Vh=-79 km/s. We have analysed the stellar density distribution in the galaxy body. The galaxy has an exponential surface brightness profile with a central light depression. We discuss the evolutionary status of KKR25, which belongs to a rare class of very isolated dwarf galaxies with spheroidal morphology.

astro-ph.CO↗

arXiv2012

Star formation history and environment of the dwarf galaxy UGCA 92

We present a quantitative star formation history of the nearby dwarf galaxy UGCA 92. This irregular dwarf is situated in the vicinity of the Local Group of galaxies in a zone of strong Galactic extinction (IC 342 group of galaxies). The galaxy was resolved into stars with HST/ACS including old red giant branch. We have constructed a model of the resolved stellar populations and measured the star formation rate and metallicity as function of time. The main star formation activity period occurred about 8 - 14 Gyr ago. These stars are mostly metal-poor, with a mean metallicity [Fe/H] ~ -1.5 -- -2.0 dex. About 84 per cent of the total stellar mass was formed during this event. There are also indications of recent star formation starting about 1.5 Gyr ago and continuing to the present. The star formation in this event shows moderate enhancement from ~ 200 Myr to 300 Myr ago. It is very likely that the ongoing star formation period has higher metallicity of about -0.6 -- -0.3 dex. UGCA 92 is often considered to be the companion to the starburst galaxy NGC 1569. Comparing our star formation history of UGCA 92 with that of NGC 1569 reveals no causal or temporal connection between recent star formation events in these two galaxies. We suggest that the starburst phenomenon in NGC 1569 is not related to the galaxy's closest dwarf neighbours and does not affect their star formation history.

astro-ph.CO↗

arXiv2011

The EFIGI catalogue of 4458 nearby galaxies with detailed morphology

Now that large databases of resolved galaxy images are provided by modern imaging surveys, advanced morphological studies can be envisioned, urging for well defined calibration samples. We present the EFIGI catalogue, a multiwavelength database specifically designed for a dense sampling of all Hubble types. The catalogue merges data from standard surveys and catalogues (Principal Galaxy Catalogue, Sloan Digital Sky Survey, Value-Added Galaxy Catalogue, HyperLeda, and the NASA Extragalactic Database) and provides detailed morphological information. Imaging data are obtained from the SDSS DR4 in the u, g, r, i, and z bands for a sample of 4458 PGC galaxies, whereas photometric and spectroscopic data are obtained from the SDSS DR5 catalogue. Point-Spread Function models are derived in all five bands. Composite colour images of all objects are visually examined by a group of astronomers, and galaxies are staged along the Hubble sequence and classified according to 16 morphological attributes describing their structure, texture, as well as environment and appearance on a five-level scale. The EFIGI Hubble sequence shows remarkable agreement with the RC3 Revised Hubble Sequence. The main characteristics and reliability of the catalogue are examined, including photometric completeness, type mix, systematic trends and correlations. The final EFIGI database is a large sub-sample of the local Universe, with a dense sampling of Sd, Sdm, Sm and Im types compared to magnitude-limited catalogues. We estimate the photometric catalogue to be more than ~ 80% complete for galaxies with 10<g<14. More than 99.5% of EFIGI galaxies have a known redshift in the HyperLeda and NED databases.

astro-ph.CO↗

arXiv2010

Galaxy groups and clouds in the Local (z~0.01) universe

We present an all-sky catalogue of 395 nearby galaxy groups revealed in the Local Supercluster and its surroundings. The groups and their associations are identified among 10914 galaxies at |b|>15deg with radial velocities VLG<3500 km/s. Our group finding algorithm requires the group members to be located inside their zero-velocity surface. Hereby, we assume that individual galaxy masses are proportional to their total K-band luminosities, M/L_K=6 Msun/Lsun. The sample of our groups, where each group has n>=4 members, is characterized by the following medians: mean projected radius =268 kpc, radial velocity dispersion sigma_V=74 km/s, K-band luminosity L_K=1.2x10^11 Lsun, virial and projected masses Mvir=2.4x10^12 and Mp=3.3x10^12 Msun, respectively. Accounting for measurement error reduces the median masses by 30 per cent. For 97 per cent of identified groups the crossing time does not exceed the cosmic time, 13.7 Gyr, having the median at 3.8 Gyr. We examine different properties of the groups, in particular, of the known nearby groups and clusters in Virgo and Fornax. About a quarter of our groups can be classified as fossil groups where the dominant galaxy is at least ten times brighter than the other group members. In total, our algorithm identifies 54 per cent of galaxies to be members of groups. Together with triple systems and pairs they gather 82 per cent of the K-band light in Local universe. We have obtained the local value of matter density to be Omega_m=0.08+-0.02 within a distance of ~40 Mpc assuming H0=73 km/s/Mpc. It is significantly smaller than the cosmic value, 0.28, in the standard lambdaCDM model. The discrepancy between the global and local quantities of Omega_m may be caused by the existence of Dark Matter component unrelated to the virial masses of galaxy systems.

astro-ph.CO↗

arXiv2010

Groups of dwarf galaxies in the Local supercluster

We present a project on study of groups composed of dwarf galaxies only. We selected such structures using HyperLEDA and NED databases with visual inspection on SDSS images and on digital copy of POSS. The groups are characterized by size of few tens of kpc and line-of-sight velocity dispersion about 18 km/s. Our groups similar to associations of nearby dwarfs from Tully et al. (2006). This specific population of multiple dwarf galaxies such as IZw18 may contain significant amount of dark matter. It is very likely that we see them at the stage just before merging of its components.

astro-ph.CO↗

arXiv2010

Star formation history of KDG 61 and KDG 64 from spectroscopy and colour-magnitude diagrams

A study of two dE/dSph members of the nearby M 81 group of galaxies, KDG 61 and UGC 5442 = KDG 64, has been made. Direct Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) images and integrated-light spectra of 6 m telescope of Special Astrophysical Observatory of Russian Academy of Sciences have been used for quantitative star formation history analysis. The spectroscopic and colour-magnitude diagrams analysis gives consistent results. These galaxies appear to be dominated by an old population (12-14 Gyr) of low metallicity ([Fe/H]~-1.5). Stars of ages about 1 to 4 Gyr have been detected in both galaxies. The later population shows marginal metal enrichment. We do not detect any significant radial gradients in age or metallicity in these galaxies. Our radial velocity measurement suggests that the HII knot on the line-of-sight of KDG 61 is not gravitationally attached to the galaxy.

astro-ph.CO↗

arXiv2007

Mining the Local Volume

After recent systematic optical, IR, and HI surveys, the total number of known galaxies within 10 Mpc has increased from 179 to 550. About half this Local Volume (LV) sample is now been imaged with HST, yielding the galaxy distances with an accuracy of about 8%. For the majority of the LV galaxies we currently have H-alpha fluxes that allow us to reconstruct the star formation history of our neighbourhood. For the late-type LV galaxies their HI masses and angular momentum follow the linear relation in the range of 4 orders, which is expected for rotating gaseous disks being near the gravitational instability threshold. The data obtained on the LV galaxies imply important cosmological parameters, in particular, the mean local matter density and HI mass density, as well as SFR density. Surprisingly, the local Hubble flow around the LV groups is very quiet, with 1D rms deviations of 25 km/s,which is a signature of the Universe vacuum-dominated on small scales. The cold infall pattern around nearby groups provides us with a new method to determine the total mass of the groups independent from virial mass estimates.

astro-ph↗

arXiv2007

Tip of the Red Giant Branch Distances. II. Zero-Point Calibration

The luminosity of the Tip of the Red Giant Branch (TRGB) provides an excellent measure of galaxy distances and is easily determined in the resolved images of nearby galaxies observed with Hubble Space Telescope. There is now a large amount of archival data relevant to the TRGB methodology and which offers comparisons with other distance estimators. Zero-point issues related to the TRGB distance scale are reviewed in this paper. Consideration is given to the metallicity dependence of the TRGB, the transformations between HST flight systems and Johnson-Cousins photometry, the absolute magnitude scale based on Horizontal Branch measurements, and the effects of reddening. The zero-point of the TRGB is established with a statistical accuracy of 1%, modulo the uncertainty in the magnitude of the Horizontal Branch, with a typical rms uncertainty of 3% in individual galaxy distances at high Galactic latitude. The zero-point is consistent with the Cepheids period-luminosity relation scale but invites reconsideration of the claimed metallicity dependence with that method. The maser distance to NGC 4258 is consistent with TRGB but presently has lower accuracy.

astro-ph↗