Following the discovery of a black hole (BH) with a mass of 10^3-10^6 M(sun)
in a starburst galaxy M82, we study formation of such a BH via successive
merging of stellar-mass BHs within a star cluster. The merging has a runaway
characteristic. This is because massive BHs sink into the cluster core and have
a high number density, and because the merging probability is higher for more
massive BHs. We use the Smoluchowski equation to study analytically the
evolution of the BH mass distribution. Under favorable conditions, which are
expected for some star clusters in starburst galaxies, the timescale of the
runaway merging is at most of order 10^7 yr. This is short enough to account
for the presence of a BH heavier than 10^3 M(sun) in an ongoing starburst
region.Comment: 10 pages, no figures, to appear in The Astrophysical Journal
(Letters
Sampling of sea‐salt particles was carried out over the western Pacific Ocean. The collected particles were studied individually by X‐ray spectrometry. Sea‐salt particles with radii r ≥ 0.5 μm show a considerable range in their weight ratios of S/Na and Ca/Na, while Cl/Na ratios remain constant at the seawater value. Moreover, there is a tight correlation between S/Na and Ca/Na. This property is attributable to fractionary recrystallization within evaporating drops. Particles with r < 0.5 μm exhibit a similar trend. However, these particles tend to show smaller Cl/Na ratios and larger S/Na ratios than those with r ≥ 0.5 μm. Chemical reaction between sea salt and acidic material, where Cl− is replaced by (SO4)2− and (NO3)−, is the most plausible explanation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.