Olexandr Gugnin

Taras Shevchenko National University of Kyiv

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N. G. Pulatova

Main Astronomical Observatory

L. Zadorozhna

Taras Shevchenko National University of Kyiv

Anatolii Tugay

Taras Shevchenko National University of Kyiv

A. V. Tugay

Taras Shevchenko National University of Kyiv

E. Fedorova

Taras Shevchenko National University of Kyiv

Alexander Ganz

Jagiellonian University

O. Lukina

Rhys Seeburger

Max Planck Institute for Astronomy

O. Malyi

Buyan Wan

Hunan University of Science and Technology

Cooperative Institutions

Taras Shevchenko National University of Kyiv

National Academy of Sciences of Ukraine

Main Astronomical Observatory

Max Planck Institute for Astronomy

Jagiellonian University

Astronomy and Space

Special Astrophysical Observatory

Crimean Astrophysical Observatory

National Astronomical Research Institute of Thailand

Astronomical Observatory of Rome

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Advanced morphology of VIPERS galaxies

arXiv (Cornell University) (2021)

Olexandr Gugnin Anatolii Tugay N. G. Pulatova L. Zadorozhna

We calculated morphological parameters for 70821 galaxies from VIPERS (spectroscopic galaxy survey performed on VIMOS spectroscope at VLT). These parameters includes Gini, M20, Concentration, Asymmetry and Smoothness. Results correlate with the distribution of these parameters for other simulated and observed samples. We also studied dependence of these parameters with Sersic power index of radial distribution of surface brightness of galaxy image. Our aim was to find a clear separation of VIPERS galaxies on elliptical and spiral. This is necessary for testing the method of Sersic index (ns) calculation in statmorph program. To find such bimodality we use B-V color index from VIPERS database. To perform the error analysis of morphological parameters we simulated galaxy images with random background of different magnitude and estimated the errors as dispersion of the parameters. We also found asymptotic values of errors of morphological parameters by increasing the numbers of mock images. To analyse the possible variation of each morphological parameter during the convolution of close galactic images, we have simulated them to research. In the result of this investigation we have analysed the dependence of the every morphological parameter from CAS and Gini/M20 statistics from the distance between galactic centers. The differences between our results for VIPERS and Gini-M20 distribution for PanStarrs galaxies at z<0.5 could be explained it by cosmological evolution of galaxies. We found out that in modern Universe there are much more elliptical galaxies than at z>0.5 which corresponds to VIPERS sample. Also we concluded that galaxy mergers were more frequent in the early Universe.

Smoothness

Surface brightness fluctuation

Bimodality

Shape parameter

10.48550/arxiv.2110.11666

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Separating the spectral counterparts in NGC 1275/Perseus cluster in X-rays

arXiv (Cornell University) (2023)

E. Fedorova L. Zadorozhna Anatolii Tugay N. G. Pulatova Alexander Ganz

We develop the recipe to separate the spectral counterparts of the AGN NGC 1275 from the emission of the Perseus cluster surrounding it in the spectra observed by Suzaku/XIS cameras with no usage of the spectral fitting models. The Perseus cluster emission reaches higher energies than is typical for the most AGN-situated dense surroundings (i.e. up to 9-10 keV). That is why the separation between the AGN and cluster spectra is especially important in this case. To avoid the degeneracy due to the huge quantity of the spectral fitting parameters such as abundances of elements the cluster consists of, thermal and Compton emission of the nucleus itself, and the jet SSC/IC emission spectral parameters as well we prefer to avoid the spectral fitting usage to perform this task. Instead, we use the spatial resolution of the components and double background subtracting. For this purpose we choose the following regions to collect all the photons from them: (1) circular or square-shaped region around the source (AGN); (2) ring-shaped (or non-overlapped square) region surrounding the AGN (for cluster); (3) remote empty circular region for the background. Having collected the photons from those regions we subtract the background (i.e. photons from the third region) from the source and cluster spectra. Next, we subtract the re-normalized cluster counts from the AGN spectrum; using the relation between the emission line amplitudes in the AGN and cluster spectra as the renormalization coefficient. We have performed this procedure on the whole set of the Suzaku/XIS observational data for NGC 1275 to obtain the cleaned spectra and light curve of the AGN emission in this system.

Spectral resolution

10.48550/arxiv.2312.01174

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Separating the Spectral Counterparts in NGC 1275/Perseus Cluster in X-Rays

Astronomy (2024)

E. Fedorova L. Zadorozhna Anatolii Tugay N. G. Pulatova Alexander Ganz

We present a model-independent method for separating the spectral counterparts of the active galactic nucleus (AGN) NGC 1275 from the surrounding emission of the Perseus cluster, as observed by Suzaku/XIS cameras. The Perseus cluster emission extends to higher energies than typically observed in AGN environments, reaching up to 9–10 keV. This necessitates precise separation of AGN and cluster spectra. To circumvent the degeneracy arising from numerous spectral fitting parameters, including elemental abundances, thermal and Compton emissions from the nucleus, and spectral parameters of the jet synchrotron self-Compton/inverse Compton emissions, we avoid traditional spectral fitting methods. Instead, we leverage spatial resolution and employ a double background subtraction approach. We apply this procedure to the complete set of Suzaku/XIS observational data for NGC 1275, resulting in cleaned spectra and a light curve of the AGN emission in this system. To demonstrate the applicability of our method, we also utilize the available XMM-Newton/EPIC data.

10.3390/astronomy3040017

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X-ray galaxies selected from HyperLEDA database

Journal of Physical Studies (2022)

N. G. Pulatova A. V. Tugay L. Zadorozhna Rhys Seeburger O. Lukina

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Sample (material)

10.30970/jps.26.4901

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Spatial and temporal super-resolution methods for high-fidelity solar imaging

Astronomy and Astrophysics (2025)

Olexandr Gugnin Buyan Wan Charmaine S.M. Wong Shirley Ho

The Sun plays a significant role in space weather by emitting energy and electromagnetic radiation that influence the environment around the Earth. Missions such as SOHO, STEREO, and SDO captured solar observations at multiple wavelengths to monitor and predict solar events. However, the data transmission from these missions is often constrained, in particular, for those operating at greater distances from Earth. This limits the availability of continuous observations. We increase the spatial and temporal resolution of solar images to improve the quality and availability of solar data. By addressing telemetry constraints and providing more detailed solar image reconstructions, we seek to facilitate a more accurate analysis of solar dynamics and improve space weather prediction. We applied deep-learning techniques, specifically, a UNet-based architecture, to generate high-resolution solar images that enhance the intricate details of the solar structures. Additionally, we used a similar architecture to reconstruct solar image sequences with a reduced temporal resolution to predict missing frames and restore temporal continuity. Our deep-learning approach successfully enhances the resolution of solar images and reveals finer details of solar structures. The model also predicts missing frames in solar image sequences, which allows more continuous observation despite telemetry constraints. These advancements contribute to a better analysis of solar dynamics and set the stage for an improved space weather forecasting and future solar physics research.

Helioseismology

Temporal resolution

10.1051/0004-6361/202452638

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Advanced morphology of VIPERS galaxies

Journal of Physical Studies (2022)

Olexandr Gugnin A. V. Tugay N. G. Pulatova L. Zadorozhna

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Surface brightness fluctuation

Smoothness

Bimodality

10.30970/jps.26.2901

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