I will outline some of the puzzles related to the connection between the first stars and the first galaxies in the light of new theoretical and observational (ALMA, JWST) findings.
We present new evolutionary models of primordial very massive stars, with initial masses ranging from 100 Msun to 1000 Msun, that extend from the main sequence until the onset of dynamical instability caused by the creation of electron-positron pairs during core C, Ne, or O burning, depending on the star's mass and metallicity.
Mass loss accounts for radiation-driven winds as well as...
Population III (Pop III) stars are almost metal-free stars, born from the primordial gas in the Universe. They have eluded any attempt of observation so far. Therefore, we must rely on predictions from the most advanced and detailed stellar evolutionary models to study them. The almost total absence of metals impacts their initial mass function distribution (predicted to be top-heavy), their...
Results from numerical simulations of primordial structure formation will be presented and their implications for early pristine population III stars and the transition to the following metal-enriched popII/I regimes will be discussed. A number of observables will be used to test different population III stellar models (in terms of mass and metal yields) and to rule out non performing ones, as...
Constraining the properties of the first generation of stars is one of the key motivations of the James Webb Space Telescope. I will discuss strategies for identifying genuine Pop III stellar populations, potential contaminants, and learnings from nearly one full year of JWST data.
In recent years observations of blank fields enabled us to detect galaxies as far as z~11. However, very little is known about those galaxies, and they are mostly the most luminous representatives. Observations with James Webb Space Telescope will revolutionize this field. In particular, grism spectrograph NIRISS provides observing modes for slitless spectroscopy, which will be unique in...
Individual stars are typically not detectable beyond the local Universe, but gravitational lensing by foreground galaxy clusters can in rare cases raise the brightness of extremely distant stars to detectable levels. More than a dozen lensed stars at z~1-3 have already been detected this way using HST and JWST, along with a smaller number of candidates at z~5-6 (including the current record...
An efficient search for elusive PopIII sources/ stellar complexes at high redshift is a trade-off between different aspects related to (1) the available instrumentation (technical) and (2) the physical conditions which maximize their occurrence (physics). The necessity of reaching quite faint luminosity while keeping an elevated spatial contrast (both spectroscopy and photometry) seems the...
I will give a brief summary on the origin of elements using Galactic chemical evolution with Pop II and Pop I stars. Then I will discuss the Pop III nucleosynthesis using extremely metal-poor stars in the Milky Way. Namely, I will present our new analysis with machine learning to find “the first stars were not alone”. Finally, I will discuss the first chemical enrichment in the Universe,...
GRB are produced by massive stars. Several studies considered the possibility of PoPIII stars as GRB progenitors and predicted the GRB properties. Furthermore GRB afterglows are bright at any redshift and can be used as background sources to study the absorbing gas in their host galaxies and along GRB lines of sight up to the highest redshift, looking for signatures of pristine gas or gas...
I will present the study of the abundances of the chemical elements present in the gas associated with cosmological structures at redshift ~6. The goal is to look for the nucleosynthetic traces of the Pop III stars and, more generally, to understand which generation of stars contributed to the enrichment of metals in the gas of galaxies at that time.
To determine these abundances, we studied...
The properties of the first (Pop. III) stars remain a mystery. The chemistry of relic environments, enriched only by the supernovae of these first stars, offer an exciting avenue to study this population. Stellar relics are often found in the local Universe while gaseous relics probe the chemistry of low density structures at earlier epochs (z>2). I will discuss the complementary nature of...
Quasar absorption line systems are an excellent probe of chemical evolution across time. In absorption line systems associated with the interstellar and circumgalactic medium of galaxies, the column densities of gas are sufficiently high that detailed and accurate chemical abundance patterns can be obtained and compared to complimentary stellar abundance analyses. These detailed chemical...
The first stars were born from chemically pristine gas. They were likely massive and thus they rapidly exploded as supernovae, enriching the surrounding gas with heavy elements.
The nature of first stars can be studied locally, investigating the chemical properties of ancient metal-poor stars in the Milky Way halo and in Local Group dwarf galaxies. Indeed, here we observe low-mass, long-lived...
I will review results on the effects of population III stars on the chemical abundances of the population II stars. Some of the unsolved problems related to this topics will be discussed.
During Big Bang Nucleosynthesis, hydrogen, helium, and small traces of lithium and beryllium were produced. A few million years after BBN, the first stars were formed out of this primordial material. Important questions about star formation, galactic evolution, and the yields of the first supernovae can be answered from the study of these first stars and their descendants. The most chemically...
The Sculptor dwarf spheroidal galaxy is old and metal-poor, making it ideal to study the earliest chemical enrichment in the Local Group. We followed up the most metal-poor star known in this (or any external) galaxy, AS0039, with high-resolution ESO VLT/UVES spectra. Our new analysis confirmed its low metallicity, [Fe/H]=-3.90, and that it is extremely C-poor, with [C/Fe]=-0.33. This adds to...
