相关论文: Pristine Massive Star Formation Caught at the Brea…
Star formation from metal-free gas, the hallmark of the first generation of Population III stars, was long assumed to occur only in the very early Universe. We report the discovery of MPG-CR3 (Metal-Pristine Galaxy COSMOS Redshift 3;…
The early Universe presented a star formation environment that was almost devoid of heavy elements. The lowest metallicity stars thus provide a unique window into the earliest Galactic stages, but are exceedingly rare and difficult to find.…
We study the detectability of primordial metal-free stars. Cosmological enrichment is a local process that takes place over an extended redshift range. While the duration of this transition depends on several unknown factors, in all cases…
The first metals in the universe are expected to form in population III stars - primordial stars consisting entirely of hydrogen and helium. However, these stars have so far remained elusive. Simulations indicate that galaxies consisting…
The chemical composition of the most metal-deficient stars reflects the composition of the gas from which they formed. These old stars provide crucial clues to the star formation history and the synthesis of chemical elements in the early…
Local massive early-type galaxies are believed to have completed most of their star formation $\sim10$Gyr ago and evolved without having substantial star formation since. If so, their progenitors should have roughly solar stellar…
Four recent observational results have challenged our understanding of high--redshift galaxies, as they require the presence of far more ultraviolet photons than should be emitted by normal stellar populations. First, there is significant…
In the early Universe finding massive galaxies that have stopped forming stars present an observational challenge as their rest-frame ultraviolet emission is negligible and they can only be reliably identified by extremely deep…
The orbits of the least chemically enriched stars open a window on the formation of our Galaxy when it was still in its infancy. The common picture is that these low-metallicity stars are distributed as an isotropic, pressure-supported…
The cosmic microwave background and the cosmic expansion can be interpreted as evidence that the Universe underwent an extremely hot and dense phase about 14 Gyr ago. The nucleosynthesis computations tell us that the Universe emerged from…
We construct star formation histories at redshifts z > 5 for two physically distinct populations of primordial, metal-free stars, motivated by theoretical and observational arguments that have hinted towards the existence of an intermediate…
In typical astrophysical environments, the abundance of heavy elements ranges from 0.001 to 2 times the solar concentration. Lower abundances have been seen in select stars in the Milky Way's halo and in two quasar absorption systems at…
We present spectra of the most massive quiescent galaxy yet discovered at $z>3$, spectroscopically confirmed via the detection of Balmer absorption features in the $H-$ and $K-$bands of Keck/MOSFIRE. The spectra confirm a galaxy with no…
Population III stars, the hypothetical first generation metal-free stars, have yet to be discovered. Even after three years of successful JWST operations, studies have shown that most galaxies identified to date at $z > 5$ exhibit a…
The first galaxies contain stars born out of gas with little or no metals. The lack of metals is expected to inhibit efficient gas cooling and star formation but this effect has yet to be observed in galaxies with oxygen abundance relative…
The James Webb Space Telescope (JWST) has discovered a surprising population of bright galaxies in the very early universe (<500 Myrs after the Big Bang) that is hard to explain with conventional galaxy formation models and whose physical…
Finding and characterising the first galaxies that illuminated the early Universe at cosmic dawn is pivotal to understand the physical conditions and the processes that led to the formation of the first stars. In the first few months of…
In the current cosmological model, only the three lightest elements were created in the first few minutes after the Big Bang; all other elements were produced later in stars. To date, however, heavy elements have been observed in all…
The chemical composition of galaxies has been measured out to z~4. However, nearly all studies beyond z~0.7 are based on strong-line emission from HII regions within star-forming galaxies. Measuring the chemical composition of distant…
JWST is beginning to uncover a population of extremely metal-poor galaxies (EMPGs, $Z < 1\%~\mathrm{Z}_\odot$) at $z > 3$, mostly through serendipitous NIRSpec discoveries and blind slitless spectroscopy. To accelerate our understanding of…