Cooling flows in galaxy clusters and isolated elliptical galaxies are a source of mass for fueling accretion onto a central supermassive black hole. We calculate the dynamics of accreting matter in the combined gravitational potential of a host galaxy and a central black hole assuming a steady state, spherically symmetric flow (i.e., no angular momentum). The global dynamics depends primarily o...

We investigate the form of the momentum distribution function for protons and electrons in an advection–dominated accretion flow (ADAF). We show that for all accretion rates, Coulomb collisions are too inefficient to thermalize the protons. The proton distribution function is therefore determined by the viscous heating mechanism, which is unknown. The electrons, however, can exchange energy qui...

The radio emission from supermassive black holes in nearby early-type galaxies can be used to test possible explanations for their low luminosities. We calculate the expected contribution from thermal synchrotron emission from hot accretion flows to the high radio frequency observations of NGC 2300, NGC 1399, NGC 4278 and NGC 4594. We find that, in all cases, and in accordance with our previous...

The radially averaged metallicity distribution of the ISM and the young stellar population of a sample of 20 disk galaxies is investigated by means of an analytical chemical evolution model which assumes constant ratios of galactic wind mass loss and accretion mass gain to star formation rate. Based on this model the observed metallicities and their gradients can be described surprisingly well ...

We study numerically the evolution of rotating cloud cores, from the collapse of a magnetically supercritical core to the formation of a protostar and the development of a protostellar disk during the main accretion phase. We find that the disk quickly becomes unstable to the development of a spiral structure similar to that observed recently in AB Aurigae. A continuous infall of matter from th...

We explore the growth of planetary embryos by planetesimal accretion up to and beyond point at which pebble becomes efficient so-called Hill-transition mass. Both transition mass characteristic planetesimals that formed streaming instability increase with increasing distance from star. developed a model for large (embryo) embedded in population smaller filament instability. The includes self-co...

Introduction: Early models of accretion of Mars [1] suggested long time scales and led to assumed cold post-accretion initial temperatures [2]. But later accretion models [3] gave much shorter time scales and led to the general acceptance of a hot Mars heated by the kinetic energy of impacting planetesimals. Evidence from isotopic studies also seems to require early melting; in particular, Hf-W...

nezami, is one of the greatest story-teller poets of persian literature whose poems are always followed and welcomed by other poets. zaari, a kurdish poet, is one of those who has translated nezami's  “leyli-va-majnun” poem into kurdish language.     in this paper, “leyli-va majnun” of both zaari and nezami have been comparatively studied and our research is conducted in three parts: elisi...

The accretion disc eclipse mapping method is an astrotomographic inversion technique that makes use of the information contained in eclipse light curves to probe the structure, the spectrum and the time evolution of accretion discs in cataclysmic variables. This paper presents examples of eclipse mapping results that have been key to improve our understanding of accretion physics.