arXiv subjects

Natalia Lyskova

Publications and source records attributed to Natalia Lyskova.

7 recordsLinked to original sources

arXiv2025

X-ray flux -- mass relation for $z\gtrsim 0.7$ galaxy clusters

We use a subsample of co-detections of the ACT and MaDCoWS cluster catalogs to verify the predicted relation between the observed X-ray flux $F_X$ in the 0.5-2~keV band and the cluster mass $M_{\rm 500c}$ for halos at $z>0.6-0.7$. We modify this relation by introducing a correction coefficient $η$, which is supposed to encapsulate factors associated with a particular method of flux estimation, the sample selection function, the definition of the cluster mass, etc. We show that the X-ray flux, being the most basic X-ray observable, serves as a convenient and low-cost mass indicator for distant galaxy clusters with photometric or even missing redshifts (by setting $z=1$) as long as it is known that $z\gtrsim 0.6-0.7$. The correction coefficient $η$ is $\approx 0.8$ if $M^{\rm UPP}_{\rm 500c}$ from the ACT-DR5 catalog are used as cluster masses and $η\approx 1.1$ if weak-lensing-calibrated masses $M^{\rm Cal}_{\rm 500c}$ are used instead.

astro-ph.CO↗

arXiv2020

Strongly lensed SN Refsdal: refining time delays based on the supernova explosion models

We explore the properties of supernova (SN) "Refsdal" - the first discovered gravitationally lensed SN with multiple images. A large magnification provided by the galactic-scale lens, augmented by the cluster lens, gave us a unique opportunity to perform a detailed modelling of a distant SN at z=1.5. We present results of radiation hydrodynamics modelling of SN Refsdal. According to our calculations, the SN Refsdal progenitor is likely to be a more massive and energetic version of SN 1987A, i.e. a blue supergiant star with the following parameters: the progenitor radius $R_0 = (50 \pm 1) R_{\odot}$, the total mass $M_{tot}= (25\pm 2) M_{\odot}$, the radioactive $^{56}$Ni mass $M_{^{56}\mathrm{Ni}} = (0.26 \pm 0.05) \,M_{\odot}$, and the total energy release $E_{burst}=(4.7 \pm 0.8)\times10^{51}$ erg. Reconstruction of SN light curves allowed us to obtain time delays and magnifications for the images S2-S4 relative to S1 with higher accuracy than previous template-based estimates of Rodney \& et al. (2016). The measured time delays are $Δt_{S2-S1} = 9.5^{+2.6}_{-2.7} $ days, $Δt_{S3-S1} = 4.2^{+2.3}_{-2.3} $ days, and $Δt_{S4-S1} = 30^{+7.8}_{-8.2} $ days. The obtained magnification ratios are $μ_{S2/S1}= 1.14 \pm 0.02$, $μ_{S3/S1} = 1.01 \pm 0.02 $, and $μ_{S4/S1} = 0.35\pm 0.02$. We estimate the Hubble constant $H_0 = 68.6^{+13.6}_{-9.7}$ km s$^{-1}$ Mpc$^{-1}$ via re-scaling the time delays predicted by different lens models to match the values obtained in this work. With more photometric data on the fifth image SX, we will be able to further refine the time delay and magnification estimates for SX and obtain competitive constraints on $H_0$.

astro-ph.HE↗

arXiv2020

Influence of the Galactic gravitational field on the positional accuracy of extragalactic sources. II Observational appearances and detectability

We consider a possibility of detecting the jitter effect of apparent celestial positions of distant sources due to local fluctuations of the Galaxy gravitational field. It is proposed to observe two samples of extragalactic sources (target and control) in different sky directions using the high-precision radio interferometry. It is shown that on a scale of ~2 years, it is possible to detect a systematic increase in the standard deviation of measured arc lengths of pairs of target sources compared to the control ones at the $3σ$-level if the accuracy of differential astrometric observations is around 10 $μ$as. For the current state-of-the-art accuracy of 30 $μ$as achieved at the KVN or VERA interferometers, which have shorter baselines in comparison with VLBI, the target and control samples will differ only at the 2$σ$-level on the scale of 10 years. To achieve the $3σ$-level on this time interval, it is necessary to improve the accuracy up to ~20 $μ$as. Other possible effects that can also affect the arc length measurements between two sources are discussed, and an observational strategy to minimize them is suggested.

astro-ph.GA↗

arXiv2019

Progressive steepening of the SNR RX J1713.7-3946 X-ray spectrum from XMM-Newton to INTEGRAL

In this work, we present the first detailed analysis of the supernova remnant RX J1713.7-3946 in the hard X-ray energy range with the IBIS coded-mask telescope on board the INTEGRAL observatory. The shell-type morphology of the entire remnant is mapped in hard X-rays for the first time and significantly detected up to 50 keV. The IBIS sky image of RX J1713.7-3946, accumulated over 14 years of operations, demonstrates two extended hard X-ray sources. These sources are spatially consistent with northwest and southwest rims of RX J1713.7-3946 and are also clearly visible at energies below 10 keV with XMM-Newton. This points to a single emission mechanism operating in soft and hard X-rays. The INTEGRAL 17-120 keV spectrum of RX J1713.7-3946 is characterized by a power-law continuum with the photon index of $Γ\approx3$, that is significantly softer than $Γ\approx2$ determined by XMM-Newton in the 1-10 keV energy range, suggesting a progressive steepening of the spectrum with the energy.

astro-ph.HE↗

arXiv2019

Runaway Merger Shocks in Galaxy Cluster Outskirts and Radio Relics

Moderately strong shocks arise naturally when two subclusters merge. For instance, when a smaller subcluster falls into the gravitational potential of a more massive cluster, a bow shock is formed and moves together with the subcluster. After pericenter passage, however, the subcluster is decelerated by the gravity of the main cluster, while the shock continues moving away from the cluster center. These shocks are considered as promising candidates for powering radio relics found in many clusters. The aim of this paper is to explore the fate of such shocks when they travel to the cluster outskirts, far from the place where the shocks were initiated. In a uniform medium, such a "runaway" shock should weaken with distance. However, as shocks move to large radii in galaxy clusters, the shock is moving down a steep density gradient that helps the shock to maintain its strength over a large distance. Observations and numerical simulations show that, beyond $R_{500}$, gas density profiles are as steep as, or steeper than, $\sim r^{-3}$, suggesting that there exists a "Habitable zone" for moderately strong shocks in cluster outskirts where the shock strength can be maintained or even amplified. A characteristic feature of runaway shocks is that the strong compression, relative to the initial state, is confined to a narrow region just behind the shock. Therefore, if such a shock runs over a region with a pre-existing population of relativistic particles, then the boost in radio emissivity, due to pure adiabatic compression, will also be confined to a narrow radial shell.

astro-ph.GA↗

arXiv2019

A New Class of X-Ray Tails of Early-Type Galaxies and Subclusters in Galaxy Clusters - Slingshot Tails vs Ram Pressure Stripped Tails

We show that there is a new class of gas tails - slingshot tails - which form as a subhalo (i.e. a subcluster or early-type cluster galaxy) moves away from the cluster center towards the apocenter of its orbit. These tails can point perpendicular or even opposite to the subhalo direction of motion, not tracing the recent orbital path. Thus, the observed tail direction can be misleading, and we caution against naive conclusions regarding the subhalo's direction of motion based on the tail direction. A head-tail morphology of a galaxy's or subcluster's gaseous atmosphere is usually attributed to ram pressure stripping and the widely applied conclusion is that gas stripped tail traces the most recent orbit. However, during the slingshot tail stage, the subhalo is not being ram pressure stripped (RPS) and the tail is shaped by tidal forces more than just the ram pressure. Thus, applying a classic RPS scenario to a slingshot tail leads not only to an incorrect conclusion regarding the direction of motion, but also to incorrect conclusions in regard to the subhalo velocity, expected locations of shear flows, instabilities and mixing. We describe the genesis and morphology of slingshot tails using data from binary cluster merger simulations, discuss their observable features and how to distinguish them from classic RPS tails. We identify three examples from the literature that are not RPS tails but slingshot tails and discuss other potential candidates.

astro-ph.GA↗

arXiv2018

Mass density slope of elliptical galaxies from strong lensing and resolved stellar kinematics

We discuss constraints on the mass density distribution (parameterized as $ρ\propto r^{-γ}$) in early-type galaxies provided by strong lensing and stellar kinematics data. The constraints come from mass measurements at two `pinch' radii. One `pinch' radius $r_1=2.2 R_{Einst}$ is defined such that the Einstein (i.e. aperture) mass can be converted to the spherical mass almost independently of the mass-model. Another `pinch' radius $r_2=R_{opt}$ is chosen so that the dynamical mass, derived from the line-of-sight velocity dispersion, is least sensitive to the anisotropy of stellar orbits. We verified the performance of this approach on a sample of simulated elliptical galaxies and on a sample of 15 SLACS lens galaxies at $0.01 \leq z \leq 0.35$, which have already been analysed in Barnabe et al. (2011) by the self-consistent joint lensing and kinematic code. For massive simulated galaxies the density slope $γ$ is recovered with an accuracy of $\sim 13\%$, unless $r_1$ and $r_2$ happen to be close to each other. For SLACS galaxies, we found good overall agreement with the results of Barnabe et al. (2011) with a sample-averaged slope $γ=2.1\pm0.05$. While the two-pinch-radii approach has larger statistical uncertainties, it is much simpler and uses only few arithmetic operations with directly observable quantities.

astro-ph.GA↗