Abstract

Saccardi
Evidence of First Stars-enriched Gas in High-redshift Absorbers
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. In the Local Group, the chemical signatures of the first stars were identified among low-mass, long-lived, very metal-poor stars, characterized by a high abundance of carbon over iron. Conversely, a similar carbon excess was not found in dense neutral gas traced by QSO absorption systems at high redshift. In this talk I will present the detection of 3 very metal-poor, carbon-enhanced absorbers, at redshift z~3-4 through the analysis of QSOs absorption spectra. These absorbers reveal an overabundance with respect to Fe of all the analyzed chemical elements such as C, Mg, and Si. The distribution of the relative abundances with respect to [Fe/H] matches those of the local very metal-poor stars. Consequently, these absorbers, likely imprinted by the chemical yields of the first stars, suggest that the signature of the first stars survives in optically thick, relatively diffuse absorbers, not sufficiently dense to sustain star formation and hence, not dominated by the chemical products of normal stars. These results, which fully complements stellar archeology, represent a fresh start for the searches of first star pollution in high-z environments, that can provide unique insight on both the early phases of reionization and the metal enrichment history of the Universe.

Saccardi

Evidence of First Stars-enriched Gas in High-redshift Absorbers

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. In the Local Group, the chemical signatures of the first stars were identified among low-mass, long-lived, very metal-poor stars, characterized by a high abundance of carbon over iron. Conversely, a similar carbon excess was not found in dense neutral gas traced by QSO absorption systems at high redshift.
In this talk I will present the detection of 3 very metal-poor, carbon-enhanced absorbers, at redshift z~3-4 through the analysis of QSOs absorption spectra. These absorbers reveal an overabundance with respect to Fe of all the analyzed chemical elements such as C, Mg, and Si. The distribution of the relative abundances with respect to [Fe/H] matches those of the local very metal-poor stars. Consequently, these absorbers, likely imprinted by the chemical yields of the first stars, suggest that the signature of the first stars survives in optically thick, relatively diffuse absorbers, not sufficiently dense to sustain star formation and hence, not dominated by the chemical products of normal stars. These results, which fully complements stellar archeology, represent a fresh start for the searches of first star pollution in high-z environments, that can provide unique insight on both the early phases of reionization and the metal enrichment history of the Universe.

ESO — Reaching New Heights in Astronomy

Abstract