arXiv subjects

Mariia Demianenko

Publications and source records attributed to Mariia Demianenko.

14 recordsLinked to original sources

arXiv2026

The Twentieth Data Release of the Sloan Digital Sky Survey: First All-Sky BOSS Spectra, eROSITA-SDSS-V Mapper Coordinated Observations, and a Preview of the Local Volume Mapper

This paper presents the twentieth data release (DR20) from the Sloan Digital Sky Survey, the third data release of its fifth generation (SDSS-V). SDSS-V is a panoptic spectroscopy survey that is mapping the stars, gas, and galaxies through three scientific programs: the Milky Way Mapper (MWM), the Local Volume Mapper (LVM), and the Black Hole Mapper (BHM). DR20 presents the first optical (BOSS) SDSS-V spectra from southern hemisphere for the MWM and BHM surveys; new optical MWM and BHM data from the northern hemisphere are also available, for a total over 3 million spectra of 1.5 million stars and half a million galaxies and quasars, with galactic and extragalactic x-ray targets coordinate with eROSITA DR2. DR20 includes integral field spectroscopy maps from LVM of six targets and 169 tiles, spanning Galactic HII regions, planetary nebulae, and nearby galaxies. Additionally, eighteen value added catalogs are also released with DR20, based on SDSS-V MWM and BHM data, and we present a new LVM visualization tool including an RGB HiPS map as a value added product.

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arXiv2025

Optical Emission-Line Properties of eROSITA-selected SDSS-V Galaxies

We present and discuss optical emission line properties obtained from the analysis of Sloan Digital Sky Survey (SDSS) spectra for an X-ray selected sample of 3684 galaxies (0.002 < z < 0.55), drawn from the eRASS1 catalog. We modeled SDSS-V DR19 spectra using the NBursts full spectrum fitting technique with E-MILES simple stellar populations (SSP) models and emission line templates to decompose broad and narrow emission line components for correlation with X-ray properties. We place the galaxies on the Baldwin-Phillips-Terlevich (BPT) diagram to diagnose their dominant excitation mechanism. We show that the consistent use of the narrow component fluxes shifts most galaxies systematically and significantly upward to the active galactic nuclei (AGN) region on the BPT diagram. On this basis, we confirm the dependence between a galaxys position on the BPT diagram and its (0.2-2.3 keV) X-ray/H$\alpha$ flux ratio. We also verified the correlation between X-ray luminosity and emission line luminosities of the narrow [O\iii]$\lambda 5007$ and broad H$\alpha$ component; as well as the relations between the Supermassive Black Hole (SMBH) mass, the X-ray luminosity, and the velocity dispersion of the stellar component ($\sigma_{*}$) on the base on the unique sample of optical spectroscopic follow-up of X-ray sources detected by eROSITA. These results highlight the importance of emission line decomposition in AGN classification and refine the connection between X-ray emission and optical emission line properties in galaxies.

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arXiv2025

Sloan Digital Sky Survey-V: Pioneering Panoptic Spectroscopy

The Sloan Digital Sky Survey-V (SDSS-V) is pioneering panoptic spectroscopy: it is the first all-sky, multi-epoch, optical-to-infrared spectroscopic survey. SDSS-V is mapping the sky with multi-object spectroscopy (MOS) at telescopes in both hemispheres (the 2.5-m Sloan Foundation Telescope at Apache Point Observatory and the 100-inch du Pont Telescope at Las Campanas Observatory), where 500 zonal robotic fiber positioners feed light from a wide-field focal plane to an optical (R$\sim 2000$, 500 fibers) and a near-infrared (R$\sim 22,000$, 300 fibers) spectrograph. In addition to these MOS capabilities, the survey is pioneering ultra wide-field ($\sim$ 4000~deg$^2$) integral field spectroscopy enabled by a new dedicated facility (LVM-I) at Las Campanas Observatory, where an integral field spectrograph (IFS) with 1801 lenslet-coupled fibers arranged in a 0.5 degree diameter hexagon feeds multiple R$\sim$4000 optical spectrographs that cover 3600-9800 angstroms. SDSS-V's hardware and multi-year survey strategy are designed to decode the chemo-dynamical history of the Milky Way Galaxy and tackle fundamental open issues in stellar physics in its Milky Way Mapper program, trace the growth physics of supermassive black holes in its Black Hole Mapper program, and understand the self-regulation mechanisms and the chemical enrichment of galactic ecosystems at the energy-injection scale in its Local Volume Mapper program. The survey is well-timed to multiply the scientific output from major all-sky space missions. The SDSS-V MOS programs began robotic operations in 2021; IFS observations began in 2023 with the completion of the LVM-I facility. SDSS-V builds upon decades of heritage of SDSS's pioneering advances in data analysis, collaboration spirit, infrastructure, and product deliverables in astronomy.

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arXiv2025

The Nineteenth Data Release of the Sloan Digital Sky Survey

Mapping the local and distant Universe is key to our understanding of it. For decades, the Sloan Digital Sky Survey (SDSS) has made a concerted effort to map millions of celestial objects to constrain the physical processes that govern our Universe. The most recent and fifth generation of SDSS (SDSS-V) is organized into three scientific ``mappers". Milky Way Mapper (MWM) that aims to chart the various components of the Milky Way and constrain its formation and assembly, Black Hole Mapper (BHM), which focuses on understanding supermassive black holes in distant galaxies across the Universe, and Local Volume Mapper (LVM), which uses integral field spectroscopy to map the ionized interstellar medium in the local group. This paper describes and outlines the scope and content for the nineteenth data release (DR19) of SDSS and the most substantial to date in SDSS-V. DR19 is the first to contain data from all three mappers. Additionally, we also describe nine value added catalogs (VACs) that enhance the science that can be conducted with the SDSS-V data. Finally, we discuss how to access SDSS DR19 and provide illustrative examples and tutorials.

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arXiv2025

Broad line region echo from highly accreting intermediate-mass black hole candidate SDSS J144850.08+160803.1. The first probe of intra-night variability and reverberation mapping

Elusive intermediate-mass black holes (IMBHs) can be used as ``time-squeezing'' machines, enabling studies of AGN geometry via reverberation mapping on much shorter timescales than their supermassive siblings. Constraints on the BLR radius for IMBH candidates across a broad range of Eddington ratios help probe the unexplored faint end of the radius-luminosity ($R-L$) relation in AGNs. This opens up the opportunity to build a more robust $M_{BH}$ estimator. The present study is aimed at: (a) confirming a highly accreting IMBH candidate and (b) demonstrating the feasibility of the first photometric BLR RM campaign for IMBHs with high Eddington rates. SDSS J144850.08+160803.1 was identified as an IMBH candidate from a broad H$\alpha$-selected spectroscopic sample from SDSS. We carried out XMM-Newton X-ray observations to confirm its AGN status, along with narrowband H$\alpha$ and broadband SDSS g' monitoring over five months (March-July 2024) using a 60-cm telescope at the Caucasus Mountain Observatory. These time series allowed us both to probe the short-timescale variability and extract the time lag between the BLR and AD continuum. XMM-Newton detected J1448+16 as a bright X-ray point source with a photon index of $\Gamma = 2.32^{+0.15}_{-0.13}$ and X-ray luminosity of $L_{2-10\,\rm{keV}}=(3.3^{+0.5}_{-0.4})\times10^{41}$ erg s$^{-1}$, confirming its AGN activity. From the SDSS optical spectrum and X-ray properties, we estimated a BH mass of $\sim(0.9-2.4)~\times10^{5}M_{\odot}$ and Eddington rate of $\sim37-112\%$. We report high-amplitude $\sim55\%$ intra-night ($\sim1.7$~h) H$\alpha$ variability for this IMBH and extract a tentative BLR RM radius estimate of $\sim1-8~\mathrm{days}$. This work is a proof of concept for further high-Eddington-rate IMBH variability studies and BLR RM campaigns, which will be essential for an efficient calibration of the $R-L$ relation at the faint end.

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arXiv2024

What is the Role of Large Language Models in the Evolution of Astronomy Research?

ChatGPT and other state-of-the-art large language models (LLMs) are rapidly transforming multiple fields, offering powerful tools for a wide range of applications. These models, commonly trained on vast datasets, exhibit human-like text generation capabilities, making them useful for research tasks such as ideation, literature review, coding, drafting, and outreach. We conducted a study involving 13 astronomers at different career stages and research fields to explore LLM applications across diverse tasks over several months and to evaluate their performance in research-related activities. This work was accompanied by an anonymous survey assessing participants' experiences and attitudes towards LLMs. We provide a detailed analysis of the tasks attempted and the survey answers, along with specific output examples. Our findings highlight both the potential and limitations of LLMs in supporting research while also addressing general and research-specific ethical considerations. We conclude with a series of recommendations, emphasizing the need for researchers to complement LLMs with critical thinking and domain expertise, ensuring these tools serve as aids rather than substitutes for rigorous scientific inquiry.

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arXiv2024

A closer look at the extended edge-on low-surface brightness galaxies

To understand the origin of extended disks of low-surface brightness (LSB) galaxies, we studied in detail 4 such systems with large disks seen edge-on. Two of them are edge-on giant LSB galaxies (gLSBGs) recently identified by our team. The edge-on orientation of these systems boosts their surface brightnesses that provided an opportunity to characterize stellar populations spectroscopically and yielded the first such measurements for edge-on gLSBGs. We collected deep images of one galaxy using the 1.4-m Milankovi\'c Telescope which we combined with the archival Subaru Hyper Suprime-Cam and DESI Legacy Surveys data available for the three other systems, and measured the structural parameters of the disks. We acquired deep long-slit spectra with the Russian 6-meter telescope and the 10-m Keck II telescope and estimated stellar population properties in the high- and low-surface brightness regions as well as the gas-phase metallicity distribution. The gas metallicity gradients are shallow to flat in the range between 0 and -0.03 dex per exponential disk scale length, which is consistent with the extrapolation of the gradient -- scale length relation for smaller disk galaxies. Our estimates of stellar velocity dispersion in the LSB disks as well as the relative thickness of the disks indicate the dynamical overheating. Our observations favor mergers as the essential stage in the formation scenario for massive LSB galaxies.

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arXiv2024

PSF quality metrics in the problem of revealing Intermediate-Mass Black Holes using MICADO@ELT

Nowadays, astronomers perform point spread function (PSF) fitting for most types of observational data. Interpolation of the PSF is often an intermediate step in such algorithms. In the case of the Multi-AO Imaging Camera for Deep Observations (MICADO) at the Extremely Large Telescope (ELT), PSF interpolation will play a crucial role in high-precision astrometry for stellar clusters and confirmation of the Intermediate-Mass Black Holes (IMBHs) presence. Significant PSF variations across the field of view invalidate the approach of deconvolution with a mean PSF or on-axis PSF. The ignoring of PSF variations can be especially unsatisfactory in the case of Single Conjugate Adaptive Optics (SCAO) observations, as these sophisticated and expensive systems are designed to achieve high resolution with ground-based telescopes by correcting for atmospheric turbulence in the direction of one reference star. In plenty of tasks, you face the question: How can I establish the quality of PSF fitting or interpolation? Our study aims to demonstrate the variety of PSF quality metrics, including the problem of revealing IMBHs in stellar clusters.

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arXiv2023

Understanding of the properties of neural network approaches for transient light curve approximations

Modern-day time-domain photometric surveys collect a lot of observations of various astronomical objects and the coming era of large-scale surveys will provide even more information on their properties. Spectroscopic follow-ups are especially crucial for transients such as supernovae and most of these objects have not been subject to such studies. }{Flux time series are actively used as an affordable alternative for photometric classification and characterization, for instance, peak identifications and luminosity decline estimations. However, the collected time series are multidimensional and irregularly sampled, while also containing outliers and without any well-defined systematic uncertainties. This paper presents a search for the best-performing methods to approximate the observed light curves over time and wavelength for the purpose of generating time series with regular time steps in each passband.}{We examined several light curve approximation methods based on neural networks such as multilayer perceptrons, Bayesian neural networks, and normalizing flows to approximate observations of a single light curve. Test datasets include simulated PLAsTiCC and real Zwicky Transient Facility Bright Transient Survey light curves of transients.}{The tests demonstrate that even just a few observations are enough to fit the networks and improve the quality of approximation, compared to state-of-the-art models. The methods described in this work have a low computational complexity and are significantly faster than Gaussian processes. Additionally, we analyzed the performance of the approximation techniques from the perspective of further peak identification and transients classification. The study results have been released in an open and user-friendly Fulu Python library available on GitHub for the scientific community.

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arXiv2022

Supernova Light Curves Approximation based on Neural Network Models

Photometric data-driven classification of supernovae becomes a challenge due to the appearance of real-time processing of big data in astronomy. Recent studies have demonstrated the superior quality of solutions based on various machine learning models. These models learn to classify supernova types using their light curves as inputs. Preprocessing these curves is a crucial step that significantly affects the final quality. In this talk, we study the application of multilayer perceptron (MLP), bayesian neural network (BNN), and normalizing flows (NF) to approximate observations for a single light curve. We use these approximations as inputs for supernovae classification models and demonstrate that the proposed methods outperform the state-of-the-art based on Gaussian processes applying to the Zwicky Transient Facility Bright Transient Survey light curves. MLP demonstrates similar quality as Gaussian processes and speed increase. Normalizing Flows exceeds Gaussian processes in terms of approximation quality as well.

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arXiv2022

Optical Variability of "Light-weight" Supermassive Black Holes at a Few Percent Level from ZTF Forced-Photometry Light Curves

Large time-domain surveys provide a unique opportunity to detect and explore variability of millions of sources on timescales from days to years. Broadband photometric variability can be used as the key selection criteria for weak type-I active galactic nuclei (AGN), when other "direct" confirmation criteria like X-ray or radio emission are unavailable. However, to detect variability of rather weak AGN powered by intermediate-mass black holes, typical sensitivity provided by existing light curve databases is insufficient. Here we present an algorithm for post-processing of light curves for sources with stochastic variability, retrieved from the The Zwicky Transient Facility (ZTF) Forced Photometry service. Using our approach, we can filter out spurious data points related to data reduction artefacts and also eliminate long-term trends related to imperfect photometric calibration. We can now confidently detect the broad-band variability at the 1-3 $\%$ level which can potentially be used as a substitute for expensive X-ray follow-up observations.

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arXiv2022

Confirmation of intermediate-mass black holes candidates with X-ray observations

The origin of supermassive black holes (SMBH) in galaxy centers still remains uncertain. There are two possible ways of their formation - from massive ($10^5 - 10^6 M_{\odot}$) and low-mass ($100 M_{\odot}$) BH nuclei. The latter scenario should leave behind a large number of intermediate mass black holes (IMBH, $10^2 - 10^5 M_{\odot}$). The largest published sample of bona-fide IMBH-powered AGN contains 10 objects confirmed in X-ray. Here we present a new sample of 15 bona-fide IMBHs, obtained by confirming the optically selected IMBH candidates by the presence of radiation from the galactic nucleus in the X-ray range, which increases the number of confirmed IMBHs at the centers of galaxies by 2.5 times. In the same way, 99 black holes with masses of $2\cdot10^5 - 10^6 M_{\odot}$ were confirmed. The sources of X-ray data were publicly available catalogs, archives of data, and our own observations on XMM-Newton, Chandra and Swift. The Eddington coefficients for 30% of the objects from both samples turned out to be close to critical, from 0.5 to 1, which is an unusually high fraction. Also for the first time for light-weight SMBH the correlations between the luminosity in the [OIII] emission line or the broad component of the $Hα$ line and the luminosity in the X-ray range were plotted.

astro-ph.HE↗

arXiv2022

Optical spectroscopic observations of intermediate-mass black holes and their host galaxies: the $M_{BH}-σ_*$ relation

Intermediate-mass black holes (IMBHs; $M_{BH} <2*10^{5} M_{\odot}$) in galaxy centers are cruciel for painting a coherent picture of the formation and growth of supermassive black holes (SMBHs). Using Big Data analysis, we identified 305 IMBH candidates for IMBH and 1623 candidates of `light-weight' SMBHs ($2 * 10^{5} M_{odot} < M_{BH} <10^{6} M_{\odot}$). For 35 host galaxies from this combined sample with the X-ray-confirmed active galactic nuclei (AGN) we collected and analyzed optical spectroscopic observations. These data show that bulge stellar velocity dispersions ($σ_*$) lie in the range of 24$\dots$118~km/s and do not follow the correlation with $M_{BH}$ established by larger SMBHs indicating that in the $10^{5}-10^{6} M_{\odot}$ range the accretion is the prevailing BH growth channel.

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arXiv2021

Optical light curves of light-weight supermassive black holes produced by the Zwicky Transient Facility Forced Photometry Service

In this paper, we present an algorithm to correct optical light curves obtained using The Zwicky Transient Facility Forced Photometry Service and its application to the analysis of optical variability of 136 actvie galactic nuclei (AGN) powered by "light-weight" supermassive black holes (SMBH; $M_{BH}$<2*10^6 $\odot$) including 24 intermediate-mass black holes (IMBH; $M_{BH}$<2*10^5 $\odot$). We detected variability in nearly all sources and also analyzed its dependence on the X-ray luminosity for 101 objects. We also identified a previously unknown candidate tidal disruption event (TDE) in SDSS~J112637.74+513423.0.

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