TY - JOUR
T1 - Simulating neutron star mergers as r-process sources in ultrafaint dwarf galaxies
AU - Safarzadeh, Mohammadtaher
AU - Scannapieco, Evan
N1 - Funding Information:
We are thankful to the anonymous referee for their careful reading of our manuscript. We are thankful to Frank Timmes, Alexander Ji, Mark Richardson and Rick Sarmento for useful discussions. We used the YT package (Turk et al. 2011) and PYNBODY (Pontzen et al. 2013) for part of the analysis in this work. This work was supported by the National Science Foundation under grant AST14-07835 and by NASA under theory grant NNX15AK82G. We would also like to thank the Texas Advanced Computing Center (TACC) at The University of Texas at Austin and the Extreme Science and Engineering Discovery Environment (XSEDE) for providing HPC resources via grant TG-AST130021 and TG-AST160063 that have contributed to the results reported within this paper.
Publisher Copyright:
© 2017 The Authors.
PY - 2017
Y1 - 2017
N2 - To explain the high observed abundances of r-process elements in local ultrafaint dwarf (UFD) galaxies, we perform cosmological zoom simulations that include r-process production from neutron star mergers (NSMs). We model star formation stochastically and simulate two different haloes with total masses ≈108M⊙ at z = 6. We find that the final distribution of [Eu/H] versus [Fe/H] is relatively insensitive to the energy by which the r-process material is ejected into the interstellar medium, but strongly sensitive to the environment in which the NSM event occurs. In one halo, the NSM event takes place at the centre of the stellar distribution, leading to high levels of r-process enrichment such as seen in a local UFD, Reticulum II (Ret II). In a second halo, the NSM event takes place outside of the densest part of the galaxy, leading to a more extended r-process distribution. The subsequent star formation occurs in an interstellar medium with shallow levels of r-process enrichment that results in stars with low levels of [Eu/H] compared to Ret II stars even when the maximum possible r-process mass is assumed to be ejected. This suggests that the natal kicks of neutron stars may also play an important role in determining the r-process abundances in UFD galaxies, a topic that warrants further theoretical investigation.
AB - To explain the high observed abundances of r-process elements in local ultrafaint dwarf (UFD) galaxies, we perform cosmological zoom simulations that include r-process production from neutron star mergers (NSMs). We model star formation stochastically and simulate two different haloes with total masses ≈108M⊙ at z = 6. We find that the final distribution of [Eu/H] versus [Fe/H] is relatively insensitive to the energy by which the r-process material is ejected into the interstellar medium, but strongly sensitive to the environment in which the NSM event occurs. In one halo, the NSM event takes place at the centre of the stellar distribution, leading to high levels of r-process enrichment such as seen in a local UFD, Reticulum II (Ret II). In a second halo, the NSM event takes place outside of the densest part of the galaxy, leading to a more extended r-process distribution. The subsequent star formation occurs in an interstellar medium with shallow levels of r-process enrichment that results in stars with low levels of [Eu/H] compared to Ret II stars even when the maximum possible r-process mass is assumed to be ejected. This suggests that the natal kicks of neutron stars may also play an important role in determining the r-process abundances in UFD galaxies, a topic that warrants further theoretical investigation.
KW - Galaxies: dwarf.
KW - Stars: abundances
KW - Stars: neutron
UR - http://www.scopus.com/inward/record.url?scp=85045561034&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85045561034&partnerID=8YFLogxK
U2 - 10.1093/MNRAS/STX1706
DO - 10.1093/MNRAS/STX1706
M3 - Article
AN - SCOPUS:85045561034
SN - 0035-8711
VL - 471
SP - 2088
EP - 2096
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 2
ER -