4 research outputs found
Neutron Star Mergers Are the Dominant Source of the r-process in the Early Evolution of Dwarf Galaxies
There are many candidate sites of the r-process: core-collapse supernovae
(including rare magnetorotational core-collapse supernovae), neutron star
mergers, and neutron star/black hole mergers. The chemical enrichment of
galaxies---specifically dwarf galaxies---helps distinguish between these
sources based on the continual build-up of r-process elements. This technique
can distinguish between the r-process candidate sites by the clearest
observational difference---how quickly these events occur after the stars are
created. The existence of several nearby dwarf galaxies allows us to measure
robust chemical abundances for galaxies with different star formation
histories. Dwarf galaxies are especially useful because simple chemical
evolution models can be used to determine the sources of r-process material. We
have measured the r-process element barium with Keck/DEIMOS medium-resolution
spectroscopy. We present the largest sample of barium abundances (almost 250
stars) in dwarf galaxies ever assembled. We measure [Ba/Fe] as a function of
[Fe/H] in this sample and compare with existing [alpha/Fe] measurements. We
have found that a large contribution of barium needs to occur at more delayed
timescales than core-collapse supernovae in order to explain our observed
abundances, namely the significantly more positive trend of the r-process
component of [Ba/Fe] vs. [Fe/H] seen for [Fe/H] <~ -1.6 when compared to the
[Mg/Fe] vs. [Fe/H] trend. We conclude that neutron star mergers are the most
likely source of r-process enrichment in dwarf galaxies at early times.Comment: Accepted to ApJ on 2018 October 2
Neutron Star Mergers are the Dominant Source of the r-process in the Early Evolution of Dwarf Galaxies
There are many candidate sites of the r-process: core-collapse supernovae (CCSNe; including rare magnetorotational core-collapse supernovae), neutron star mergers (NSMs), and neutron star/black hole mergers. The chemical enrichment of galaxies—specifically dwarf galaxies—helps distinguish between these sources based on the continual build-up of r-process elements. This technique can distinguish between the r-process candidate sites by the clearest observational difference—how quickly these events occur after the stars are created. The existence of several nearby dwarf galaxies allows us to measure robust chemical abundances for galaxies with different star formation histories. Dwarf galaxies are especially useful because simple chemical evolution models can be used to determine the sources of r-process material. We have measured the r-process element barium with Keck/DEIMOS medium-resolution spectroscopy. We present the largest sample of barium abundances (almost 250 stars) in dwarf galaxies ever assembled. We measure [Ba/Fe] as a function of [Fe/H] in this sample and compare with existing [α/Fe] measurements. We have found that a large contribution of barium needs to occur at more delayed timescales than CCSNe in order to explain our observed abundances, namely the significantly more positive trend of the r-process component of [Ba/Fe] versus [Fe/H] seen for [Fe/H] ≾ -1.6 when compared to the [Mg/Fe] versus [Fe/H] trend. We conclude that NSMs are the most likely source of r-process enrichment in dwarf galaxies at early times
Neutron Star Mergers are the Dominant Source of the r -process in the Early Evolution of Dwarf Galaxies
International audienceThere are many candidate sites of the r-process: core-collapse supernovae (CCSNe; including rare magnetorotational core-collapse supernovae), neutron star mergers (NSMs), and neutron star/black hole mergers. The chemical enrichment of galaxies—specifically dwarf galaxies—helps distinguish between these sources based on the continual build-up of r-process elements. This technique can distinguish between the r-process candidate sites by the clearest observational difference—how quickly these events occur after the stars are created. The existence of several nearby dwarf galaxies allows us to measure robust chemical abundances for galaxies with different star formation histories. Dwarf galaxies are especially useful because simple chemical evolution models can be used to determine the sources of r-process material. We have measured the r-process element barium with Keck/DEIMOS medium-resolution spectroscopy. We present the largest sample of barium abundances (almost 250 stars) in dwarf galaxies ever assembled. We measure [Ba/Fe] as a function of [Fe/H] in this sample and compare with existing [α/Fe] measurements. We have found that a large contribution of barium needs to occur at more delayed timescales than CCSNe in order to explain our observed abundances, namely the significantly more positive trend of the r-process component of [Ba/Fe] versus [Fe/H] seen for [{Fe}/{{H}}]≲ -1.6 when compared to the [Mg/Fe] versus [Fe/H] trend. We conclude that NSMs are the most likely source of r-process enrichment in dwarf galaxies at early times