arXiv subjects

Anastasia Kasparova

Publications and source records attributed to Anastasia Kasparova.

12 recordsLinked to original sources

arXiv2023

New Generation Stellar Spectral Libraries in the Optical and Near-Infrared I: The Recalibrated UVES-POP Library for Stellar Population Synthesis

We present re-processed flux calibrated spectra of 406 stars from the UVES-POP stellar library in the wavelength range 320-1025 nm, which can be used for stellar population synthesis. The spectra are provided in the two versions having spectral resolving power R=20,000 and R=80,000. Raw spectra from the ESO data archive were re-reduced using the latest version of the UVES data reduction pipeline with some additional algorithms that we developed. The most significant improvements in comparison with the original UVES-POP release are: (i) an updated Echelle order merging, which eliminates "ripples" present in the published spectra, (ii) a full telluric correction, (iii) merging of non-overlapping UVES spectral setups taking into account the global continuum shape, (iv) a spectrophotometric correction and absolute flux calibration, and (v) estimates of the interstellar extinction. For 364 stars from our sample, we computed atmospheric parameters $T_\mathrm{eff}$, surface gravity log $g$, metallicity [Fe/H], and $α$-element enhancement [$α$/Fe] by using a full spectrum fitting technique based on a grid of synthetic stellar atmospheres and a novel minimization algorithm. We also provide projected rotational velocity $v\sin i$ and radial velocity $v_{rad}$ estimates. The overall absolute flux uncertainty in the re-processed dataset is better than 2% with sub-% accuracy for about half of the stars. A comparison of the recalibrated UVES-POP spectra with other spectral libraries shows a very good agreement in flux; at the same time, $Gaia$ DR3 BP/RP spectra are often discrepant with our data, which we attribute to spectrophotometric calibration issues in $Gaia$ DR3.

astro-ph.IM↗

arXiv2021

Fast interactive web-based data visualizer of panoramic spectroscopic surveys

Panoramic IFU spectroscopy is a core tool of modern observational astronomy and is especially important for galaxy physics. Many massive IFU surveys, such as SDSS MaNGA (10k targets), SAMI (3k targets), Califa (600 objects), Atlas3D (260 objects) have recently been released and made publicly available to the broad astronomical community. The complexity and massiveness of the derived data products from spectral cubes makes visualization of the entire dataset challenging, but nevertheless very important and crucial for scientific output. Based on our past experience with visualization of spectral and imaging data built in the frame of the VOxAstro Initiative projects, we are now developing online web service for interactive visualizing spectroscopic IFU datasets (ifu.voxastro.org). Our service will provide a convenient access and visualization tool for spectral cubes from publicly available surveys (MaNGA, SAMI, Califa, Atlas3D) and results of their modeling, as well as maps of parameters derived from cubes, implementing the connected views concept. Here we describe the core components and functionality of the service, including REST API implementation on top of the Django+Postgres backend as well as a fast and responsive user interface built using the modern Vue.js-based framework Quasar.

astro-ph.IM↗

arXiv2021

Observational insights on the formation scenarios of giant low surface brightness galaxies

Giant low surface brightness galaxies (gLSBGs) with the disk radii of up to 130 kpc represent a challenge for currently accepted theories of galaxy formation and evolution, because it is difficult to build-up such large dynamically cold systems via mergers preserving extended disks. We summarize the in-depth study of the sample of 7 gLSBGs based on the results of the performed spectral long-slit observations at the Russian 6-m BTA telescope of SAO RAS, surface photometry and HI data available in literature. Our study revealed that most gLSBGs do not deviate from the Tully-Fisher relation. We discovered compact elliptical (cE) satellites in 2 out of these 7 galaxies. Provided the low statistical frequencies of gLSBGs and cEs, the chance alignment is improbable, so it can indicate that gLSBGs and cE are evolutionary connected and gives evidence in favor of the major merger formation scenario. Other formation paths of gLSBGs are also discussed.

astro-ph.GA↗

arXiv2021

RCSEDv2: analytic approximations of k-corrections for galaxies out to redshift $z=1$

To compare photometric properties of galaxies at different redshifts, we need to correct fluxes for the change of effective rest-frame wavelengths of filter bandpasses, called $k$-corrections. At redshifts $z>0.3$, the wavelength shift becomes so large that typical broadband photometric bands shift into the neighboring rest frame band. At $z=0.6-0.8$ the shift reaches two or even three bands. Therefore, we need perform $k$-corrections from one observed bandpass to another. Here we expand the methodology proposed by Chilingarian et al. (2010) and fit cross-band $k$-corrections by smooth low-order polynomial functions of one observed color and a redshift - this approach but without cross-band is implemented as standard functions in {\sc topcat}, which can be used for galaxies at $z<0.5$. We also computed analytic approximations for WISE bands, which were not available in the past. We now have a complete set of $k$-corrections coefficients, which allow us to process photometric measurements for galaxies out to redshift $z=1$. We calculated standard and cross-band $k$-corrections for about 4 million galaxies in second Reference Catalog of Spectral Energy Distributions (RCSEDv2) of galaxies and we showed that, in cases of widely used UV, optical and near-infrared filters, our analytic approximations work very well and can be used for extragalactic data from future wide-field surveys.

astro-ph.IM↗

arXiv2021

RCSEDv2: Processing and analysis of 4+ million galaxy spectra

RCSEDv2 (https://rcsed2.voxastro.org/), the second Reference Catalog of Spectral Energy Distributions of galaxies, provides the largest homogeneously analyzed collection of optical galaxy spectra originating from several ground-based surveys collected between 1994 and 2019. The database contains astrophysical parameters obtained using the same data analysis approach from a sample of over 4 million optical spectra of galaxies and quasars: kinematics of stellar populations and ionized gas, chemical composition and age of stellar populations, gas phase metallicity. The dataset is available via Virtual Observatory access interfaces (IVOA TAP and SSAP) and through the web-site. Here we describe the RCSEDv2 spectroscopic dataset and the data processing and analysis.

astro-ph.IM↗

arXiv2021

RCSEDv2: the largest database of galaxy properties from a homogeneously processed multi-wavelength dataset

The Reference Catalog of Spectral Energy Distributions of 800,000 galaxies (RCSED) includes the results of uniform re-processing of 800,000 SDSS DR7 galaxies at redshifts $0.007<z<0.6$ complemented with ultraviolet-to-infrared photometric data from GALEX, SDSS, and UKIDSS. The key difference between RCSED and existing databases of galaxy properties (NED, HyperLeda, part of SIMBAD) is that rather than providing a compilation of literature data, we perform homogeneous data analysis of spectral and photometric data using our own tools and publish derived physical properties of galaxies along with re-calibrated spectra and photometry and their best-fitting models. Here we present the 2nd release of our catalog, RCSEDv2 where we substantially expanded the spectral dataset to 4 million objects by including spectral data analysis for 10 large spectroscopic surveys (SDSS, SDSS/eBOSS, LAMOST, Hectospec, CfA redshift surveys, 2dFGRS, 6dFGS, DEEP2/3, WiggleZ). The photometric part has also been expanded by including DESI Legacy Survey, DES, UHS, ESO Public Surveys, and WISE in addition to GALEX, SDSS, and UKIDSS used in the original RCSED. This makes RCSEDv2 the largest database of galaxy properties and homogeneously processed spectral and photometric data up-to-date and creates a foundation for the analysis of future large-scale spectral surveys DESI and 4MOST.

astro-ph.IM↗

arXiv2021

RCSEDv2: Open-source web tools for visualization of imaging and spectral data

We present a set of open-source web tools for visualization of spectral and imaging data, which we use in the second Reference Catalogue of Spectral Energy Distributions of galaxies RCSEDv2 (https://rcsed2.voxastro.org/). Using modern web frameworks Quasar and Vue.js we developed interactive viewers to visualize spectra and SEDs of galaxies and the diagrams presenting emission line ratios determined from the analysis of their spectra (BPT diagrams). The viewers are built in Javascript which puts a minimum load on the server side while providing full interactivity for the user. The use of modern web frameworks provides full customization making the viewers easily embeddable into web-sites of astronomical archives and databases. It also provides compatibility with popular third-party web-tools such as Aladin Lite.

astro-ph.IM↗

arXiv2021

RCSEDv2: homogenization of multi-wavelength photometric data

RCSEDv2 (https://rcsed2.voxastro.org/), the second Reference Catalog of Spectral Energy Distributions of galaxies includes the largest homogeneously processed photometric dataset for 4 million galaxies assembled from several wide-field surveys. Here we describe the methodology of the photometric data homogenization. We first correct all photometric measurements for the foreground Galactic extinction, then convert them into the photometric system we adopted as a standard (GALEX + SDSS + UKIDSS + WISE). We computed aperture corrections into several pre-defined apertures by using published galaxy sizes / light profiles and image quality for each of the surveys. We accounted for k-corrections using our own analytic approximations. Such a homogeneous photometric catalog allows us to build fully calibrated SEDs for the galaxies in our sample (defined by the availability of their spectra) and enables direct scientific analysis of this unique extragalactic dataset.

astro-ph.IM↗

arXiv2021

Multi-segment and Echelle stellar spectra processing issues and how to solve them

High-quality stellar spectra are in great demand now - they are the most important ingredient in the stellar population synthesis to study galaxies and star clusters. Here we describe the procedures to increase the quality of flux calibration of stellar spectra. We use examples of NIR intermediate-resolution Echelle spectra collected with the Folded InfraRed Echellete (R~6500, Magellan Baade) and high-resolution UV-optical spectra observed with UVES (R~80000, ESO VLT). By using these procedures, we achieved the quality of the global spectrophotometric calibration as good as 1-2%, which fulfills the requirements for the quality of stellar spectra intended to be used in the stellar population synthesis

astro-ph.IM↗

arXiv2021

Observational insights on the origin of giant low surface brightness galaxies

Giant low surface brightness galaxies (gLSBGs) with dynamically cold stellar discs reaching the radius of 130 kpc challenge currently considered galaxy formation mechanisms. We analyse new deep long-slit optical spectroscopic observations, archival optical images and published HI and optical spectroscopic data for a sample of seven gLSBGs, for which we performed mass modelling and estimated the parameters of dark matter haloes assuming the Burkert dark matter density profile. Our sample is not homogeneous by morphology, parameters of stellar populations and total mass, however, six of seven galaxies sit on the high-mass extension of the baryonic Tully-Fisher relation. In UGC 1382 we detected a global counterrotation of the stellar high surface brightness (HSB) disc with respect to the extended LSB disc. In UGC 1922 with signatures of a possible merger, the gas counterrotation is seen in the inner disc. Six galaxies host active galactic nuclei, three of which have the estimated black hole masses substantially below those expected for their (pseudo-)bulge properties suggesting poor merger histories. Overall, the morphology, internal dynamics, and low star formation efficiency in the outer discs indicate that the three formation scenarios shape gLSBGs: (i) a two-stage formation when an HSB galaxy is formed first and then grows an LSB disc by accreting gas from an external supply; (ii) an unusual shallow and extended dark matter halo; (iii) a major merger with fine-tuned orbital parameters and morphologies of the merging galaxies.

astro-ph.GA↗

arXiv2019

UGC 1378 -- a Milky Way-sized galaxy embedded in a giant low-surface brightness disc

The dominant physical processes responsible for the formation and longevity of giant gaseous and stellar discs in galaxies remain controversial. Although they are rare (less than 10 confirmed as of now), giant low-surface brightness (gLSB) discy galaxies provide interesting insights given their extreme nature. We describe observations of UGC 1378 including deep spectroscopy with the Russian 6m telescope and multi-band imaging with Binospec at the MMT. Galaxy UGC 1378 has both high surface brightness and an extended low surface brightness discs. Our stellar velocity dispersion data for the high-surface brightness, Milky Way-sized, disc appears inconsistent with a recent major merger, a widely discussed formation scenario for the very extended low surface brightness disc. We estimate the star formation rates (SFR) from archival Wide-Field Infrared Survey Explorer data. The SFR surface density in the LSB disc is low relative to its gas density, consistent with recent gas accretion. We argue that the unusually large size of UGC 1378's disc may be the product of a rich gas reservoir (e.g. a cosmic filament) and an isolated environment that has preserved the giant disc.

astro-ph.GA↗

arXiv2016

The insight into the dark side. I. The pitfalls of the dark halo parameters estimation

We examined the reliability of estimates of pseudoisothermal, Burkert and NFW dark halo parameters for the methods based on the mass-modelling of the rotation curves.To do it we constructed the $χ^2$ maps for the grid of the dark matter halo parameters for a sample of 14 disc galaxies with high quality rotation curves from THINGS. We considered two variants of models in which: a) the mass-to-light ratios of disc and bulge were taken as free parameters, b) the mass-to-light ratios were fixed in a narrow range according to the models of stellar populations. To reproduce the possible observational features of the real galaxies we made tests showing that the parameters of the three halo types change critically in the cases of a lack of kinematic data in the central or peripheral areas and for different spatial resolutions. We showed that due to the degeneracy between the central densities and the radial scales of the dark haloes there are considerable uncertainties of their concentrations estimates. Due to this reason it is also impossible to draw any firm conclusion about universality of the dark halo column density based on mass-modelling of even a high quality rotation curve. The problem is not solved by fixing the density of baryonic matter. In contrast, the estimates of dark halo mass within optical radius are much more reliable. We demonstrated that one can evaluate successfully the halo mass using the pure best-fitting method without any restrictions on the mass-to-light ratios.

astro-ph.GA↗