587 research outputs found
Probing 3D Density and Velocity Fields of ISM in Centers of Galaxies with Future X-Ray Observations
Observations of bright and variable "reflected" X-ray emission from molecular
clouds located within inner hundred parsec of our Galaxy have demonstrated that
the central supermassive black hole, Sgr A*, experienced short and powerful
flares in the past few hundred years. These flares offer a truly unique
opportunity to determine 3D location of the illuminated clouds (with ~10 pc
accuracy) and to reveal their internal structure (down to 0.1 pc scales). Short
duration of the flare(s), combined with X-rays high penetration power and
insensitivity of the reflection signal to thermo- and chemo-dynamical state of
the gas, ensures that the provided diagnostics of the density and velocity
fields is unbiased and almost free of the projection and opacity effects. Sharp
and sensitive snapshots of molecular gas accessible with aid of future X-ray
observatories featuring large collecting area and high angular (arcsec-level)
and spectral (eV-level) resolution cryogenic bolometers will present invaluable
information on properties of the supersonic turbulence inside the illuminated
clouds, map their shear velocity field and allow cross-matching between X-ray
data and velocity-resolved emission of various molecular species provided by
ALMA and other ground-based facilities. This will highlight large and
small-scale dynamics of the dense gas and help uncovering specifics of the ISM
lifecycle and high-mass star formation under very extreme conditions of
galactic centers. While the former is of particular importance for the SMBH
feeding and triggering AGN feedback, the latter might be an excellent test case
for star formation taking place in high-redshift galaxies.Comment: White paper submitted to the Astro2020 Decadal Surve
Self-force of a point charge in the space-time of a symmetric wormhole
We consider the self-energy and the self-force for an electrically charged
particle at rest in the wormhole space-time. We develop general approach and
apply it to two specific profiles of the wormhole throat with singular and with
smooth curvature. The self-force for these two profiles is found in manifest
form; it is an attractive force. We also find an expression for the self-force
in the case of arbitrary symmetric throat profile. Far from the throat the
self-force is always attractive.Comment: 18 pages, 3 figures Comments: corrected pdf, enlarged pape
Rare case of type II glycogen storage disease
The article presents information about a rare case of Pompe disease. It is a glycogen storage disease. During the third screening of a pregnant woman, the ultrasonography of the fetus’s heart revealed the myocardial hypertrophy of the left ventricle perceived as posthypoxic. After delivery, the newborn underwent the ultrasound examination and molecular genetic studies. Firstly, the hepatomegaly and cardiomegaly were diagnosed. Then an infantile form of Pompe disease was found. The patient got enzyme replacement therapy without positive result. The death occurred at the age of 2 years and 5 months as a result of cardiovascular disease failure. Macroscopically, the sizes of the internal organs were increased. The microscopic examination demonstrated glycogen deposition in the myocardium, skeletal muscles, mucous membranes of the organs of the gastrointestinal tract, liver, kidney, spleen and adrenal gland
Tempestuous life beyond R500: X-ray view on the Coma cluster with SRG/eROSITA. II. Shock & Relic
This is the second paper in a series of studies of the Coma cluster using the
SRG/eROSITA X-ray data obtained during the calibration and performance
verification phase of the mission. Here, we focus on the region adjacent to the
radio source 1253+275 (radio relic, RR, hereafter). We show that the X-ray
surface brightness exhibits its steepest gradient at (), which is almost co-spatial to the outer edge
of the RR. As in the case of several other relics, the Mach number of the shock
derived from the X-ray surface brightness profile () appears to
be lower than needed to explain the slope of the integrated radio spectrum in
the diffusive shock acceleration (DSA) model () if the magnetic
field is uniform and the radiative losses are fast. However, the shock geometry
is plausibly much more complicated than a spherical wedge centered on the
cluster, given the non-trivial correlation between radio, X-ray, and SZ images.
While the complicated shock geometry alone might cause a negative bias in
, we speculate on a few other possibilities that may affect the
- relation, including the shock substructure that might be modified
by the presence of non-thermal filaments stretching across the shock and the
propagation of relativistic electrons along the non-thermal filaments with a
strong magnetic field. We also discuss the "history" of the radio galaxy
NGC4789, which is located ahead of the relic in the context of the Coma-NGC4839
merger scenario.Comment: Replaced with the accepted versio
X-ray surface brightness and gas density profiles of galaxy clusters up to 3*R500c with SRG/eROSITA
Using the data of the SRG/eROSITA all-sky survey, we stacked a sample of ~40
galaxy cluster images in the 0.3--2.3 keV band, covering the radial range up to
. The excess emission on top of the galactic and
extragalactic X-ray backgrounds and foregrounds is detected up to . At these distances, the surface brightness of the stacked image
drops below % of the background. The density profile reconstructed from
the X-ray surface brightness profile agrees well (within %) with the
mean gas profile found in numerical simulations, which predict the local gas
overdensity of 20--30 at and the gas fraction
close to the universal value of in the
standard CDM model. Taking at face value, this agreement suggests that
up to the X-ray signal is not strongly boosted by
the gas clumpiness, although a scenario with a moderately inhomogeneous gas
cannot be excluded. A comparison of the derived gas density profile with the
electron pressure profile based on the SZ measurements suggests that by the gas temperature drops by a factor of 4--5
below the characteristic temperature of a typical cluster in the sample within
, while the entropy keeps growing up to this distance. Better
constraints on the gas properties just beyond should be
possible with a sample larger than used for this pilot study.Comment: accepted by MNRA
Integrable boundary conditions for classical sine-Gordon theory
The possible boundary conditions consistent with the integrability of the
classical sine-Gordon equation are studied. A boundary value problem on the
half-line with local boundary condition at the origin is considered.
The most general form of this boundary condition is found such that the problem
be integrable. For the resulting system an infinite number of involutive
integrals of motion exist. These integrals are calculated and one is identified
as the Hamiltonian. The results found agree with some recent work of Ghoshal
and Zamolodchikov.Comment: 10 pages, DTP/94-3
Prospects of detecting soft X-ray emission from typical WHIM filaments around massive clusters and the Coma cluster soft excess
While hot ICM in galaxy clusters makes these objects powerful X-ray sources,
the cluster's outskirts and overdense gaseous filaments might give rise to much
fainter sub-keV emission. Cosmological simulations show a prominent "focusing"
effect of rich clusters on the space density of the Warm-Hot Intergalactic
Medium (WHIM) filaments up to a distance of (
turnaround radius, ) and beyond. Here, we use Magneticum simulations to
characterize their properties in terms of integrated emission measure for a
given temperature and overdensity cut and the level of contamination by the
more dense gas. We suggest that the annuli around
massive clusters might be the most promising sites for the search of the gas
with overdensity . We model spectral signatures of the WHIM in the
X-ray band and identify two distinct regimes for the gas at temperatures below
and above . Using this model, we estimate the sensitivity
of X-ray telescopes to the WHIM spectral signatures. We found that the WHIM
structures are within reach of future high spectral resolution missions,
provided that the low-density gas is not extremely metal-poor. We then consider
the Coma cluster observed by SRG/eROSITA during the CalPV phase as an example
of a nearby massive object. We found that beyond the central () circle, where calibration uncertainties preclude clean
separation of the extremely bright cluster emission from a possible softer
component, the conservative upper limits are about an order of magnitude larger
than the levels expected from simulations.Comment: Submitted to MNRA
Casimir effect in a wormhole spacetime
We consider the Casimir effect for quantized massive scalar field with
non-conformal coupling in a spacetime of wormhole whose throat is rounded
by a spherical shell. In the framework of zeta-regularization approach we
calculate a zero point energy of scalar field. We found that depending on
values of coupling , a mass of field , and/or the throat's radius
the Casimir force may be both attractive and repulsive, and even equals to
zero.Comment: 2 figures, 10 pages, added 2 reference
Improving the system of warranty service of trucks in foreign markets
The article is devoted to the practical methods development of improving one of the ways to ensure the health of trucks in the system warranty. Methodology is aimed at optimizing the processes of formation of warranty spare parts kits during the implementation of KAMAZ trucks in foreign markets. The example is given to demonstrate the importance of different factors in the formation of the warranty set for different regions. The algorithm was developed to assess the qualitative composition formed warranty package that will optimize the planning and organization of activity centers to improve operational reliability of commercial trucks. A basis for acceptance of the scientifically-proved decisions is the statistical data analysis of requests monitoring that allows organizing duly replacement of parts with expired service life, and also promotes customer servicing quality improvement and reliability of trucks by prevention of its failures
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