arXiv subjects

A. Marchuk

Publications and source records attributed to A. Marchuk.

4 recordsLinked to original sources

arXiv2026

Globular Clusters in the Time of the JWST. I. Survey Design and First Results on Multiple Populations and Beyond

Globular clusters (GCs) host multiple stellar populations with distinct chemical compositions, but their properties among very low-mass stars remain poorly constrained. The James Webb Space Telescope (JWST) enables precise infrared studies that are highly sensitive to abundance variations in cool stars. We initiate a homogeneous survey of Galactic GCs, based primarily on deep JWST GO-8960 observations and complemented by archival JWST and Hubble Space Telescope data, to characterize multiple populations across a wide range of cluster properties. In this first paper, we present the survey and initial NIRCam results. We analyze eleven GCs, deriving high-precision photometry and astrometry to measure proper motions. Multiple populations are detected among low-mass stars in all clusters, with diverse behaviors. We find discrete main sequences in NGC 288, NGC 6723, and NGC 2808, and more continuous distributions in NGC 104 and the Type II clusters NGC 1851 and NGC 6656. The bulge clusters NGC 6528, NGC 6553, and NGC 6440 show patterns consistent with varying helium and oxygen abundances that do not scale simply with cluster mass. In Terzan 5 and Liller 1, we identify populations spanning different ages and helium variations within the old population of Terzan 5. We also detect an M-dwarf gap in NGC 104 around 0.35 solar masses, consistent with the Jao Gap of field stars and open clusters. This work establishes the foundation for a homogeneous JWST survey of Galactic GCs and provides a valuable dataset for studies of cluster evolution, Galactic stellar populations, and background extragalactic sources.

astro-ph.GA↗

arXiv2025

A Comprehensive Analysis on the Nature of the Spiral Arms in NGC 3686, NGC 4321, and NGC 2403

In theoretical investigations, various mechanisms have been put forward to explain the emergence of spiral patterns in galaxies. One of the few ways to find out the nature of spirals in a particular galaxy is to consider the so-called corotation radius, or corotation resonance. A distinctly defined corotation resonance is likely to indicate the existence of a spiral density wave, while the chaotic distribution of their positions may suggest a dynamic nature to the spiral structure. In this study, we analyzed measurements of the corotation radius obtained using several methods for three galaxies (NGC 3686, NGC 4321, and NGC 2403) that exhibit different morphologies of spiral structures. We also performed independent measurements to estimate the location of the resonance, which allowed us to determine whether each galaxy has a clear corotation radius position. This examination, along with other tests such as stellar age gradient, interlocking resonances, and the radial distribution of metallicity, enables us to understand the mechanism that may be responsible for the formation of spiral arms in the studied galaxies.

astro-ph.GA↗

arXiv2022

The Edge-on Galaxies in the Pan-STARRS survey (EGIPS)

We present a catalogue of 16551 edge-on galaxies created using the public DR2 data of the Pan-STARRS survey. The catalogue covers the three quarters of the sky above Dec.=-30 degrees. The galaxies were selected using a convolutional neural network, trained on a sample of edge-on galaxies identified earlier in the SDSS survey. This approach allows us to dramatically improve the quality of the candidate selection and perform a thorough visual inspection in a reasonable amount of time. The catalogue provides homogeneous information on astrometry, SExtractor photometry, and non-parametric morphological statistics of the galaxies. The photometry is reliably for objects in the 13.8-17.4 r-band magnitude range. According to the HyperLeda database, redshifts are known for about 63 percent of the galaxies in the catalogue. Our sample is well separated into the red sequence and blue cloud galaxy populations. The edge-on galaxies of the red sequence are systematically Delta(g-i)~0.1 mag redder than galaxies oriented at an arbitrary angle to the observer. We found a variation of the galaxy thickness with the galaxy colour. The red sequence galaxies are thicker than the galaxies of the blue cloud. In the blue cloud, on average, thinner galaxies turn out to be bluer. In the future, based on this catalogue it is intended to explore the three-dimensional structure of galaxies of different morphologies, as well as to study the scaling relations for discs and bulges.

astro-ph.GA↗

arXiv2013

A coupling pair of dwarfs in Lynx

We report on discovery of unique binary system of dIr galaxies which looks like a low surface brightness tidal stream in the halo of another dwarf galaxy. Both the galaxies are detected in the HI line with the Giant Metrewave Radio Telescope (GMRT). The pair components have absolute blue magnitudes -16.0 and -13.2, heliocentric radial velocities 1799 and 1842 km/s, and hydrogen masses-to-luminosity ratios 0.4 and 1.6 in solar units, respectively. The binary system is characterized by a high orbital mass-to-luminosity ratio of 49 in solar units and a short crossing time of 0.22 Gyr.

astro-ph.CO↗