Lunch talk on Sep. 7, 2020
A Carbon-enhanced Lyman Limit System: Signature of the First Generation of Stars?
Speaker: Siwei Zou (KIAA-PKU)
Venue: Video conference
Time: 12:30 PM, Monday, Sep. 7, 2020
We present the study of a Lyman limit system (LLS) at zabs = 1.5441 towards quasar J134122.50+185213.9 observed with VLT X-shooter. This is a very peculiar system with strong neutral carbon (CI) absorption seen associated with a neutral hydrogen column density of log N(H I) (cm−2 ) = 18.10, too small to shield the gas from any external UV flux. The low ionization absorption lines exhibit a simple kinematic structure consistent with a single component. Using CLOUDY models to correct for ionization, we find that the ionization parameter of the gas is in the range –4.5 < log U < –4.2 and the gas density –1.5 < log n(H) (cm−3 ) < –1.2. The models suggest that carbon is overabundant relative to iron, [C/Fe] > +2.2 at [Fe/H] ∼ –1.6. Such a metal abundance pattern is reminiscent of carbon enhanced metal-poor stars detected in the Galaxy halo. Metal enrichment by the first generation of supernovae provide a plausible explanation for the inferred abundance pattern in this system.
Report PPT: SWIFAR_Siwei Zou.pdf