6,314 research outputs found
Time-dependent Circulation Flows: Iron Enrichment in Cooling Flows with Heated Return Flows
We describe a new type of dynamical model for hot gas in galaxy groups and
clusters in which gas moves simultaneously in both radial directions.
Circulation flows are consistent with (1) the failure to observe cooling gas in
X-ray spectra, (2) multiphase gas observed near the centers of these flows and
(3) the accumulation of iron in the hot gas from Type Ia supernovae in the
central galaxy. Dense inflowing gas cools, producing a positive central
temperature gradient, as in normal cooling flows. Bubbles of hot, buoyant gas
flow outward. Circulation flows eventually cool catastrophically if the outward
flowing gas transports mass but no heat; to maintain the circulation both mass
and energy must be supplied to the inflowing gas over a large volume, extending
to the cooling radius. The rapid radial recirculation of gas produces a flat
central core in the gas iron abundance, similar to many observations. We
believe the circulation flows described here are the first gasdynamic,
long-term evolutionary models that are in good agreement with all essential
features observed in the hot gas: little or no gas cools as required by XMM
spectra, the gas temperature increases outward near the center, and the gaseous
iron abundance is about solar near the center and decreases outward.Comment: 17 pages (emulateapj5) with 6 figures; accepted by The Astrophysical
Journa
Gamma ray constraints on the Galactic supernova rate
We perform Monte Carlo simulations of the expected gamma ray signatures of Galactic supernovae of all types to estimate the significance of the lack of a gamma ray signal due to supernovae occurring during the last millenium. Using recent estimates of the nuclear yields, we determine mean Galactic supernova rates consistent with the historic supernova record and the gamma ray limits. Another objective of these calculations of Galactic supernova histories is their application to surveys of diffuse Galactic gamma ray line emission
Gamma ray constraints on the galactic supernova rate
Monte Carlo simulations of the expected gamma-ray signatures of galactic supernovae of all types are performed in order to estimate the significance of the lack of a gamma-ray signal due to supernovae occurring during the last millenium. Using recent estimates of nuclear yields, we determine galactic supernova rates consistent with the historic supernova record and the gamma-ray limits. Another objective of these calculations of galactic supernova histories is their application to surveys of diffuse galactic gamma-ray line emission
Constraints on the Primordial Magnetic Field from
A primordial magnetic field (PMF) can affect the evolution of density field
fluctuations in the early universe.In this paper we constrain the PMF amplitude
and power spectral index by comparing calculated
density field fluctuations with observational data, i.e. the number density
fluctuation of galaxies.We show that the observational constraints on
cosmological density fluctuations, as parameterized by , lead to
strong constraints on the amplitude and spectral index of the PMF.Comment: 11 pages, 1 figure, accepted for publication as Phys. Rev.
R-Process Nucleosynthesis in Core-Collapse Supernova Explosion
We study the r-process nucleosynthesis in neutrino-driven winds of
gravitational core collapse SNeII. Appropriate physical conditions are found
for successful r-process nucleosynthesis, which meet with several features of
heavy elements discovered recently in metal-deficient halo stars. We find also
several difficulties which are not explained in the present wind models. We
discuss quests for new insights in nuclear physics, astrophysics, and
astronomy.Comment: 14 pages, 6 figures, Nuclear Physics A, in pres
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