相关论文: The slow death of most galaxies
Local galaxies are broadly divided into two main classes, star-forming (gas-rich) and quiescent (passive and gas-poor). The primary mechanism responsible for quenching star formation in galaxies and transforming them into quiescent and…
The globally-averaged star formation rate in the Universe has been steadily declining since at least z~1. This may be due either to very local processes operating within the average galaxy, or to external, environmental effects.…
Young galaxies are clumpy, gas-rich, and highly turbulent. Star formation appears to occur by gravitational instabilities in galactic disks. The high dispersion makes the clumps massive and the disks thick. The star formation rate should be…
Star formation in half of massive galaxies was quenched by the time the Universe was three billion years old. Very low amounts of molecular gas appear responsible for this, at least in some cases, though morphological gas stabilization,…
Understanding how and why star formation turns off in massive galaxies is a major challenge for studies of galaxy evolution. Many theoretical explanations have been proposed, but a definitive consensus is yet to be reached.
At redshift z = 2, when the Universe was just three billion years old, half of the most massive galaxies were extremely compact and had already exhausted their fuel for star formation(1-4). It is believed that they were formed in intense…
A number of years ago the estimates of astronomers and astrophysicists were that the earliest galaxies took about 2.5 to 3 billion years to form, that is, that they did not appear until 2.5 to 3 billion years after the Big Bang. Those…
Star formation history shows a gradual decline since the last 8-9 Gyr (z=1). The bulk of present-day stellar mass and metal content was formed at redshifts lower than 2-3, which is consistent with a hierarchical scenario of galaxy…
The quenching of star formation activity represents a critical phase for a non-negligible fraction of the observed galaxy population at all cosmic epochs, marking a transition from an epoch of intense mass growth to an extended period of…
Properties of normal galactic star formation, including the density dependence, threshold density, turbulent scaling relations, and clustering properties, are applied to the formation of galactic bulges. One important difference is that the…
Theories of how galaxies, the fundamental constituents of large-scale structure, form and evolve have undergone a dramatic paradigm shift in the last few decades. Earlier views were of rapid, early collapse and formation of basic…
The evolution of galaxies results from a combination of internal and external processes. The star formation is an internal process transforming cold and dense cores of molecular clouds to stars. It may be triggered internally by expanding…
Most present-day galaxies with stellar masses $\geq10^{11}$ solar masses show no ongoing star formation and are dense spheroids. Ten billion years ago, similarly massive galaxies were typically forming stars at rates of hundreds solar…
Most star complexes are in fact complexes of stars, clusters and gas clouds; term "star complexes" was introduced as general one disregarding the preferential content of a complex. Generally the high rate of star formation in a complex is…
Star clusters are formed in molecular clouds which are believed to be the birth places of most stars. From recent observational data, Lada & Lada(2003) estimated that only 4 to 7% of the proto-clusters have survived. Many factors could…
The formation of the first galaxies at redshifts z ~ 10-15 signaled the transition from the simple initial state of the universe to one of ever increasing complexity. We here review recent progress in understanding their assembly process…
To understand the evolution of galaxies, we need to know as accurately as possible how many galaxies were present in the Universe at different epochs. Galaxies in the young Universe have hitherto mainly been identified using their expected…
How stars are born from clouds of gas is a rich physics problem whose solution will inform our understanding of not just stars but also planets, galaxies, and the universe itself. Star formation is stupendously inefficient. Take the Milky…
Galaxy mergers trigger both star formation and accretion onto the central supermassive black hole. As a result of subsequent energetic feedback processes, it has long been proposed that star formation may be promptly extinguished in galaxy…
Most star complexes are in fact complexes of stars, clusters and gas clouds; term "star complexes" was introduced as general one disregarding the preferential content of a complex. Generally the high rate of star formation in a complex is…