Related papers: Star formation sustained by gas accretion
The gas mass fraction (fg) of spiral galaxies is strongly correlated with the central surface brightness of their disks. There exist many dim galaxies with long gas consumption time scales and fg > 0.5. This resolves the gas consumption…
In the earliest phases of their evolution, stars gain mass through the acquisition of matter from their birth clouds. The widely accepted classical concept of early stellar evolution neglects the details of this accretion phase and assumes…
We have compiled a large sample of isolated central galaxies from the Sloan Digital Sky Survey, which do not have a neighbour of comparable brightness within a projected distance of 1 Mpc. We use the colours, luminosities and surface…
We develop a model for the outer gravitationally unstable regions of accretion disks around massive black holes, for primeval or solar abundances. First we study star formation and evolution in a purely gaseous marginally unstable disk, and…
We examine the origin of clustercentric gradients in the star formation rates and colors of rich cluster galaxies within the context of a simple model where clusters are built through the ongoing accretion of field galaxies. The model…
Determination of the star formation rate can be done using mid-IR photometry or Balmer line luminosity after a proper correction for extinction effects. Both methods show convergent results while those based on UV or on [OII]3727…
The rate of star formation varies between galaxy types and evolves with redshift. Most stars in the universe have formed in episodes of an exceptionally high star-forming activity, commonly called a starburst. We here summarize basic…
We investigate the physical processes which lead to the formation of massive stars. Using a numerical simulation of the formation of a stellar cluster from a turbulent molecular cloud, we evaluate the relevant contributions of fragmentation…
Quiescent galaxies (QGs) typically have little cold gas to form stars. The discovery of gas-rich QGs challenges our conventional understanding of the evolutionary paths of galaxies. We take advantage of a new catalog of nearby, massive…
The chemical composition of high-redshift galaxies is an important property that gives clues to their past history and future evolution. Measuring abundances in distant galaxies with current techniques is often a challenge, and the…
Galaxy disks are characterised by star formation histories that vary systematically along the Hubble sequence. We study global star formation, incorporating supernova feedback, gas accretion and enriched outflows in disks modelled by a…
Large-scale outflows driven by supermassive black holes are thought to play a fundamental role in suppressing star formation in massive galaxies. However, direct observational evidence for this hypothesis is still lacking, particularly in…
Star formation rate and accummulated stellar mass are two fundamental physical quantities that describe the evolutionary state of a forming galaxy. Two recent attempts to determine the relationship between these quantities, by interpreting…
In the first part of this article we show how observations of the chemical evolution of the Galaxy: G- and K-dwarf numbers as functions of metallicity, and abundances of the light elements, D, Li, Be and B, in both stars and the…
While there is no lack of evidence for the accretion of stellar systems onto nearby galaxies, direct evidence for the accretion of gas without stars is scarce. Here we consider an inventory of starless gas "clouds" in and around galaxies of…
Stars and planets are the fundamental objects of the Universe. Their formation processes, though related, may differ in important ways. Stars almost certainly form from gravitational collapse and probably have formed this way since the…
We present a set of coupled equations that relate the stellar, gaseous, chemical, and radiation constituents of the universe averaged over the whole galaxy population. Using as input the available data from quasar absorption-line surveys,…
The formation of supermassive stars is believed to be an essential intermediate step for the formation of the massive black hole seeds that become the supermassive black holes powering the quasars observed in the early Universe. Numerical…
We present here estimates of the average rates of accretion of neutral gas onto main-sequence galaxies and the conversion of atomic gas to molecular gas in these galaxies at two key epochs in galaxy evolution: (i) $z\approx1.3-1.0$, towards…
The build-up of galaxies is regulated by a complex interplay between gravitational collapse, galaxy merging and feedback related to AGN and star formation. The energy released by these processes has to dissipate for gas to cool, condense,…