553 research outputs found
Stellar kinematics of X-ray bright massive elliptical galaxies
We discuss a simple and fast method for estimating masses of early-type
galaxies from optical data and compare the results with X-ray derived masses.
The optical method relies only on the most basic observables such as the
surface brightness and the line-of-sight velocity dispersion
profiles and provides an anisotropy-independent estimate of the
galaxy circular speed . The mass-anisotropy degeneracy is effectively
overcome by evaluating at a characteristic radius defined
from {\it local} properties of observed profiles. The sweet radius is expected to lie close to , where , and not
far from the effective radius . We apply the method to a sample of
five X-ray bright elliptical galaxies observed with the 6-m telescope BTA-6 in
Russia. We then compare the optical -estimate with the X-ray derived
value, and discuss possible constraints on the non-thermal pressure in the hot
gas and configuration of stellar orbits. We find that the average ratio of the
optical -estimate to the X-ray one is equal to with
scatter, i.e. there is no evidence for the large non-thermal pressure
contribution in the gas at . From analysis of the Lick
indices H, Mgb, Fe5270 and Fe5335, we calculate the mass of the stellar
component within the sweet radius. We conclude that a typical dark matter
fraction inside in the sample galaxies is for the
Salpeter IMF and for the Kroupa IMF.Comment: accepted for publication in MNRA
A Uniform Contribution of Core-Collapse and Type Ia Supernovae to the Chemical Enrichment Pattern in the Outskirts of the Virgo Cluster
We present the first measurements of the abundances of -elements (Mg,
Si, and S) extending out to beyond the virial radius of a cluster of galaxies.
Our results, based on Suzaku Key Project observations of the Virgo Cluster,
show that the chemical composition of the intra-cluster medium is consistent
with being constant on large scales, with a flat distribution of the Si/Fe,
S/Fe, and Mg/Fe ratios as a function of radius and azimuth out to 1.4 Mpc (1.3
). Chemical enrichment of the intergalactic medium due solely to core
collapse supernovae (SNcc) is excluded with very high significance; instead,
the measured metal abundance ratios are generally consistent with the Solar
value. The uniform metal abundance ratios observed today are likely the result
of an early phase of enrichment and mixing, with both SNcc and type Ia
supernovae (SNIa) contributing to the metal budget during the period of peak
star formation activity at redshifts of 2-3. We estimate the ratio between the
number of SNIa and the total number of supernovae enriching the intergalactic
medium to be between 12-37%, broadly consistent with the metal abundance
patterns in our own Galaxy or with the SNIa contribution estimated for the
cluster cores.Comment: accepted for publication in ApJ
Crystal structure, thermal and electrotransport properties of NdBa1–xSrxFeCo0.5Cu0.5O5+δ (0.02 ≤ x ≤ 0.20) solid solutions
Using solid-state reactions method, the solid solutions of layered oxygen-deficient perovskites NdBa1–xSrxFeCo0.5Cu0.5O5+δ (0.02 ≤ x ≤ 0.20) were prepared; their crystal structure, thermal stability, thermal expansion, electrical conductivity and thermopower were studied. It was found that NdBa1–xSrxFeCo0.5Cu0.5O5+δ phases crystallize in tetragonal syngony (space group P4/mmm) and are p-type semiconductors, whose conductivity character at high temperatures changed to the metallic one due to evolution from the samples of so-called weakly-bonded oxygen. Partial substitution of barium by strontium in NdBaFeCo0.5Cu0.5O5+δ leads to the small decreasing of unit cell parameters, thermal stability and thermopower of NdBa1–xSrxFeCo0.5Cu0.5O5+δ solid solutions, increasing of their electrical conductivity values and slightly affects their linear thermal expansion coefficient and activation energy of electrical transport values
Gas perturbations in cool cores of galaxy clusters: effective equation of state, velocity power spectra and turbulent heating
We present the statistical analysis of X-ray surface brightness and gas density fluctuations in cool cores of ten, nearby and bright galaxy clusters that have deep Chandra observations and show observational indications of radio-mechanical AGN feedback. Within the central parts of cool cores the total variance of fluctuations is dominated by isobaric and/or isothermal fluctuations on spatial scales ~ 10-60 kpc, which are likely associated with slow gas motions and bubbles of relativistic plasma. Adiabatic fluctuations associated with weak shocks constitute less than 10 per cent of the total variance in all clusters. The typical amplitude of density fluctuations is small, ~ 10 per cent or less on scales of ~ 10-15 kpc. Subdominant contribution of adiabatic fluctuations and small amplitude of density fluctuations support a model of gentle AGN feedback as opposed to periodically explosive scenarios which are implemented in some numerical simulations. Measured one-component velocities of gas motions are typically below 100-150 km/s on scales < 50 kpc, and can be up to ~ 300 km/s on ~ 100 kpc scales. The non-thermal energy is < 12 per cent of the thermal energy. Regardless of the source that drives these motions the dissipation of the energy in such motions provides heat that is sufficient to balance radiative cooling on average, albeit the uncertainties are large. Presented results here support previous conclusions based on the analysis of the Virgo and Perseus Clusters, and agree with the Hitomi measurements. With next generation observatories like Athena and Lynx, these techniques will be yet more powerful
Methyl 4-methyl-2-oxo-1,2,5,6-tetrahydro-4H-pyrrolo[3,2,1-ij]quinoline-6-carboxylate
In the title molecule, C14H15NO3, the six-membered heterocyclic ring exhibits an envelope conformation. In the crystal, C—H⋯π interactions link the molecules into centrosymmetric dimers, and weak intermolecular C—H⋯O hydrogen bonds link these dimers into columns propagated along [100]
Estimating turbulent velocities in the elliptical galaxies NGC 5044 and NGC 5813
The interstellar and intra-cluster medium in giant elliptical galaxies and
clusters of galaxies is often assumed to be in hydrostatic equilibrium.
Numerical simulations, however, show that about 5-30% of the pressure in a
cluster is provided by turbulence induced by, for example, the central AGN and
merger activity. We aim to put constraints on the turbulent velocities and
turbulent pressure in the ICM of the giant elliptical galaxies NGC 5044 and NGC
5813 using XMM-Newton RGS observations. The magnitude of the turbulence is
estimated using the Fe XVII lines at 15.01 A, 17.05 A, and 17.10 A in the RGS
spectra. At low turbulent velocities, the gas becomes optically thick in the
15.01 A line due to resonant scattering, while the 17 A lines remain optically
thin. By comparing the (I(17.05)+I(17.10))/I(15.01) line ratio from RGS with
simulated line ratios for different Mach numbers, the level of turbulence is
constrained. The measurement is limited by systematic uncertainties in the
atomic data, which are at the 20-30% level. We find that the line ratio in NGC
5813 is significantly higher than in NGC 5044. This difference can be explained
by a higher level of turbulence in NGC 5044. The high turbulent velocities and
the fraction of the turbulent pressure support of >40% in NGC 5044, assuming
isotropic turbulence, confirm that it is a highly disturbed system, probably
due to an off-axis merger. The turbulent pressure support in NGC 5813 is more
modest at 15-45%. The (I(17.05)+I(17.10))/I(15.01) line ratio in an optically
thin plasma, calculated using AtomDB v2.0.1, is 2 sigma above the ratio
measured in NGC 5044, which cannot be explained by resonant scattering. This
shows that the discrepancies between theoretical, laboratory, and astrophysical
data on Fe XVII lines need to be reduced to improve the accuracy of the
determination of turbulent velocities using resonant scattering.Comment: 11 pages, 5 figures, accepted for publication in A&
Multinuclear, heteronuclear, and heterovalent complexes in solutions
The results of investigations on the multinuclear 3d-metal compounds in solutions are generalized. The conditions for their formation, the stability, properties, composition, and interaction of the unpaired electrons of the metal centers are discussed. Interrelation between the magnetic properties, composition, and structure of the multinuclear complexes of paramagnetic ions is analyzed. © 1998 MAEe cyrillic signK Hayκa/Interperiodica Publishing
Macromolecular Al(III) complexes with poly(acrylamide) and products of its alkaline hydrolysis
The complexation of Al(III) with poly(acrylamide) and its derivatives containing carboxy groups is investigated by pH metry and viscosimetry using computer modeling. The formation of complexes of M:L = 1:1 composition and of different stability is found to be possible in a weakly acidic medium; in neutral and alkaline media, complexes of M:L = 2:2 composition may form with participation of the binuclear Al(III) hydroxo complexes. © 1996 MAEe Cyrillic signK Hayκa/Interperiodica Publishing
Gas Density Fluctuations in the Perseus Cluster: Clumping Factor and Velocity Power Spectrum
X-ray surface brightness fluctuations in the core of the Perseus Cluster are
analyzed, using deep observations with the Chandra observatory. The amplitude
of gas density fluctuations on different scales is measured in a set of radial
annuli. It varies from 8 to 12 per cent on scales of ~10-30 kpc within radii of
30-160 kpc from the cluster center and from 9 to 7 per cent on scales of ~20-30
kpc in an outer, 60-220 kpc annulus. Using a statistical linear relation
between the observed amplitude of density fluctuations and predicted velocity,
the characteristic velocity of gas motions on each scale is calculated. The
typical amplitudes of the velocity outside the central 30 kpc region are 90-140
km/s on ~20-30 kpc scales and 70-100 km/s on smaller scales ~7-10 kpc. The
velocity power spectrum is consistent with cascade of turbulence and its slope
is in a broad agreement with the slope for canonical Kolmogorov turbulence. The
gas clumping factor estimated from the power spectrum of the density
fluctuations is lower than 7-8 per cent for radii ~30-220 kpc from the center,
leading to a density bias of less than 3-4 per cent in the cluster core.
Uncertainties of the analysis are examined and discussed. Future measurements
of the gas velocities with the Astro-H, Athena and Smart-X observatories will
directly measure the gas density-velocity perturbation relation and further
reduce systematic uncertainties in these quantities.Comment: 16 pages, 15 figures, submitted to MNRAS, comments are welcom
The Role of a Mediator in the Participatory Practices in the Museum (Mediation and Facilitated Discussion)
In the era of the participation culture “viewer-inclusive” methods of communication in the museum have become in demand almost everywhere. The authors pose a question to the master of such a communication practices role. Analyzing participatory practices in terms of the achieved results, the authors appeal to the experience of art mediation (D. Malikova, E. Kochukhov, M. Lind, C. Morsh), the VTC method (A. Housen, P. Yenawine) and its version adapted for Russian students — facilitated discussion (N. V. Ievleva, M. V. Potapova). The master of participatory practices acts as a part of an art environment. The master determines the perception and description norms for an art object, even if the traditional position of the teacher and expert is deliberately reject ed. The development of creative thinking is the result of both methods. But if facilitated discussion primarily develops aesthetic literacy, then art mediation expands the museum communicative environment, attracting visitors from different demographic and psychographic groups and numerous communities
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