Open AccessEarly enrichment of quasars by the first stars
Author(s) -
Venkatesan A.,
Schneider R.,
Ferrara A.
Publication year - 2004
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2004.07754.x
Subject(s) - physics , astrophysics , stars , metallicity , initial mass function , supernova , quasar , qsos , redshift , solar mass , halo , astronomy , star formation , nucleosynthesis , galaxy , galactic halo
Studies of the broad emission‐line regions (BLRs) in quasars have revealed solar or higher enrichment levels up to the highest redshifts. In combination with the presence of large amounts of dust in QSOs at z ∼ 6 , this implies that substantial amounts of star formation and nucleosynthesis took place at significantly earlier epochs. Here, we examine whether a top‐heavy stellar initial mass function (IMF) is indicated by current data, by modelling the contributions from different regions of the IMF, including Type Ia/II and pair instability supernovae, to the metal synthesis in BLRs. We find that, in order to reproduce the observations of roughly solar values of N/C and Fe/Mg in these objects, (i) stars with a present‐day IMF are sufficient, regardless of their metallicity, (ii) zero‐metallicity stars with a top‐heavy IMF severely underproduce N/C, and (iii) the contribution of Type Ia SNe is not strongly required by the data. Therefore, stars of mass ∼1–40 M ⊙ must have existed at z ∼ 10–20 , possibly coeval with any hypothesized stars of masses ≳ 100 M ⊙ at these epochs. This is in agreement with the nucleosynthetic abundance pattern detected in extremely metal‐poor stars in the galactic halo.