Related papers: Recurrent gas accretion by massive star clusters, …
Interstellar turbulence is driven over a wide range of scales by processes including spiral arm instabilities and supernovae, and it affects the rate and morphology of star formation, energy dissipation, and angular momentum transfer in…
The entropy distribution of the intracluster medium and the shape of its confining potential well completely determine the X-ray properties of a relaxed cluster of galaxies, motivating us to explore the origin of intracluster entropy and to…
In the present-day universe, it appears that most, and perhaps all, massive stars are born in star clusters. It also appears that all star clusters contain stars drawn from an approximately universal initial mass function, so that almost…
Galaxies are thought to be fed by the continuous accretion of intergalactic gas, but direct observational evidence has been elusive. The accreted gas is expected to orbit about the galaxy's halo, delivering not just fuel for star-formation…
Although the basic physics of star formation is classical, numerical simulations have yielded essential insights into how stars form. They show that star formation is a highly nonuniform runaway process characterized by the emergence of…
(Abridged) The building blocks of galaxies are star clusters. These form with low-star formation efficiencies and, consequently, loose a large part of their stars that expand outwards once the residual gas is expelled by the action of the…
High resolution X-ray spectroscopy of the hot gas in galaxy clusters has shown that the gas is not cooling to low temperatures at the predicted rates of hundreds to thousands of solar masses per year. X-ray images have revealed giant…
Star formation depends on the available gaseous "fuel" as well as galactic environment, with higher specific star formation rates where gas is predominantly molecular and where stellar (and dark matter) densities are higher. The partition…
We present a model for the radiative output of star clusters in the process of star formation suitable for use in hydrodynamical simulations of radiative feedback. Gas in a clump, defined as a region whose density exceeds 10^4 cm^-3, is…
Clusters of galaxies, the largest collapsed structures in the Universe, are located at the intersection of extended filaments of baryons and dark matter. Cosmological accretion onto clusters through large scale filaments adds material at…
The masses of clusters of galaxies estimated by gravitational lensing exceed in many cases the mass estimates based on hydrostatic equilibrium. This may suggest the existence of nonthermal pressure. We ask if radio galaxies can heat and…
We explore various instability models for the onset of star formation in irregular galaxies. Critical gas densities are calculated for gravitational instabilities with a thin, pure-gas disk, and with a thick disk composed of gas and a…
Within the birth environment of a massive globular cluster, the combination of a luminous young stellar population and a high column density induces a state in which the thermal optical depth and radiation pressure are both appreciable. In…
In a new simple model I reconcile two contradictory views on the factors that determine the rate at which molecular clouds form stars -- internal structure vs. external, environmental influences -- providing a unified picture for the…
Starburst galaxies are powered by massive stars. These stars dominate the heating and enrichment with heavy elements of the interstellar medium, gas out of which new stars form. Thus, high-mass stars, and in consequence starburst galaxies,…
Multiple stellar populations are observed in almost all globular-clusters, but the origin of this phenomenon is still debated. We investigate the role cool supergiants may have played. To do this, we combine two investigative methods:…
Galaxies above redshift 1 can be very clumpy, with irregular morphologies dominated by star complexes as large as 2 kpc and as massive as a few 10^8 or 10^9 Mo. Their co-moving densities and rapid evolution suggest that most present-day…
Mass segregation is seen in many star clusters, but whether massive stars form in the center of a cluster or migrate there dynamically is still debated. N-body simulations have shown that early dynamical mass segregation is possible when…
Observations of pulsars in globular clusters (GCs) give evidence that more >10-20% of neutron stars (NSs) ever formed in GCs were retained there. However, the velocity distribution of field pulsars peaks at 5-10 times the escape velocities…
It is argued that galaxies like ours sustain their star formation by transferring gas from an extensive corona to the star-forming disc. The transfer is effected by the galactic fountain -- cool clouds that are shot up from the plane to…