Observations indicate that young massive star clusters in spiral and dwarf galaxies follow a relation between luminosity of the brightest young cluster and the star-formation rate (SFR) of the host galaxy, in the sense that higher SFRs lead to the formation of brighter clusters. Assuming that the empirical relation between maximum cluster luminosity and SFR reflects an underlying similar relati...

Assuming that there exists a species of heavy sterile neutrinos (mν > 1 keV) and their decays can serve as a heating source of the hot gas in galaxy clusters, we study how the observational constraints on cooling flow limit the mass of these sterile neutrinos. We predict a relation among the luminosity, total mass and the redshift of a cluster, and we compare this relation with data from 12 clu...

Abstract. The recent finding that the IGIMF (integrated galaxial initial stellar mass function) composed of all newly formed stars in all young star clusters has, in dependence of the SFR, a steeper slope in the high mass regime than the underlying canonical IMF of each star cluster offers new insights into the galactic star formation process: The classical linear relation between the SFR and t...

The size-luminosity relation of early-type Brightest Cluster Galaxies (BCGs), Re ∝ L , is steeper than that for the bulk of the early-type galaxy population, for which Re ∝ L . This is true if quantities derived from either deVaucouleur or Sersic fits to the surface brightness profiles are used. Contamination from an intra-cluster light component centered on the BCG, with similar parameters to ...

Using results of Chandra observations of old stellar systems in eleven nearby galaxies of various morphological types and census of LMXBs in the Milky Way we study population of low mass X-ray binaries and their relation to the mass of the host galaxy. We show that azimuthally averaged spatial distribution of the number of LMXBs and, in the majority of cases, of their collective luminosity clos...

Observations of type Ia supernovæ at high redshifts have become an important tool for studying the geometry of the universe. The relation between the duration of the peak phase of a type Ia supernova’s lightcurve and its luminosity (broader is brighter) forms the cornerstone of this measurement, yet it is a purely empirical relation. In this paper we show that the relation is a natural conseque...