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Title: A MASS-DEPENDENT YIELD ORIGIN OF NEUTRON-CAPTURE ELEMENT ABUNDANCE DISTRIBUTIONS IN ULTRA-FAINT DWARFS

One way to constrain the nature of the high-redshift progenitors of the Milky Way (MW) is to look at the low-metallicity stellar populations of the different Galactic components today. For example, high-resolution spectroscopy of very metal poor (VMP) stars demonstrates remarkable agreement between the distribution of [Ti/Fe] in the stellar populations of the MW halo and ultra-faint dwarf (UFD) galaxies. In contrast, for the neutron-capture (nc) abundance ratio distributions [(Sr, Ba)/Fe], the peak of the small UFD sample (6 stars) exhibits a significant under-abundance relative to the VMP stars in the larger MW halo sample ({approx}300 stars). We present a simple scenario that can simultaneously explain these similarities and differences by assuming: (1) that the MW VMP stars were predominately enriched by a prior generation of stars which possessed a higher total mass than the prior generation of stars that enriched the UFD VMP stars; and (2) a much stronger mass-dependent yield (MDY) for nc-elements than for the (known) MDY for Ti. Simple statistical tests demonstrate that conditions (1) and (2) are consistent with the observed abundance distributions, albeit without strong constraints on model parameters. A comparison of the broad constraints for these nc-MDY with those derived in the literaturemore » seems to rule out Ba production from low-mass supernovae (SNe) and affirms models that primarily generate yields from high-mass SNe. Our scenario can be confirmed by a relatively modest (factor of {approx}3-4) increase in the number of high-resolution spectra of VMP stars in UFDs.« less
Authors:
;  [1] ;  [2] ;  [3] ;  [4]
  1. Department of Astronomy, Columbia University, New York City, NY 10027 (United States)
  2. Space Telescope Science Institute, Baltimore, MD 21218 (United States)
  3. Department of Statistics, Columbia University, New York City, NY 10027 (United States)
  4. The Observatories of the Carnegie Institution of Washington, Pasadena, CA 91101 (United States)
Publication Date:
OSTI Identifier:
22133899
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 774; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; DISTRIBUTION; DWARF STARS; ELEMENT ABUNDANCE; LIMITING VALUES; MASS; METALS; MILKY WAY; NEUTRON REACTIONS; NUCLEOSYNTHESIS; ORIGIN; RED SHIFT; RESOLUTION; SPECTROSCOPY; SUPERNOVAE