Simulating neutron star mergers as r-process sources in ultrafaint dwarf galaxies

Safarzadeh, Mohammadtaher; Scannapieco, Evan

doi:10.1093/mnras/stx1706

Cited by 58 publications

(60 citation statements)

References 71 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Depending on the coalescence timescales of NS-NS mergers and on the velocity of those kicks, it is possible for NS-NS binaries to merge outside galaxies (e.g., Bloom et al 1999;Fryer et al 1999;Belczynski et al 2006;Zemp et al 2009;Kelley et al 2010;Behroozi et al 2014;Safarzadeh & Côté 2017). The simulations of Safarzadeh & Scannapieco (2017) showed that the spatial location of NS-NS mergers can play an important role on the amount of r-process material recycled into stars.…”

Section: Impact Of Natal Kicksmentioning

confidence: 99%

Neutron Star Mergers Might Not Be the Only Source of r-process Elements in the Milky Way

Côté

Eichler

Arcones

et al. 2019

ApJ

226

192

View full text Add to dashboard Cite

Probing the origin of r-process elements in the universe represents a multi-disciplinary challenge. We review the observational evidence that probe the properties of r-process sites, and address them using galactic chemical evolution simulations, binary population synthesis models, and nucleosynthesis calculations. Our motivation is to define which astrophysical sites have significantly contributed to the total mass of r-process elements present in our Galaxy. We found discrepancies with the neutron star (NS-NS) merger scenario. Assuming they are the only site, the decreasing trend of [Eu/Fe] at [Fe/H] > −1 in the disk of the Milky Way cannot be reproduced while accounting for the delaytime distribution (DTD) of coalescence times (∝ t −1 ) derived from short gamma-ray bursts and population synthesis models. Steeper DTD functions (∝ t −1.5 ) or power laws combined with a strong burst of mergers before the onset of Type Ia supernovae can reproduce the [Eu/Fe] trend, but this scenario is inconsistent with the similar fraction of short gamma-ray bursts and Type Ia supernovae occurring in early-type galaxies, and reduces the probability of detecting GW170817 in an early-type galaxy. One solution is to assume an extra production site of Eu that would be active in the early universe, but would fade away with increasing metallicity. If this is correct, this extra site could be responsible for roughly 50 % of the Eu production in the early universe, before the onset of Type Ia supernovae. Rare classes of supernovae could be this additional r-process source, but hydrodynamic simulations still need to ensure the conditions for a robust r-process pattern.

show abstract

Section: Impact Of Natal Kicksmentioning

confidence: 99%

Neutron Star Mergers Might Not Be the Only Source of r-process Elements in the Milky Way

Côté

Eichler

Arcones

et al. 2019

ApJ

226

192

View full text Add to dashboard Cite

show abstract

“…In particular, Côté et al (2018) compares high-resolution hydrodynamics simulations directly with one-zone models, finding the importance of non-uniform mixing in driving abundance spreads in these galaxies, and characterize multiple hydrodynamics effects that are challenging to parameterize in current one-zone models. Additional works have conducted more direct investigations into what drives the enrichment process for individual sources using both hydrodynamics simulations (Pan et al 2013;Ritter et al 2015;Safarzadeh & Scannapieco 2017;Hirai et al 2015;Hirai & Saitoh 2017;Emerick et al 2018;Haynes & Kobayashi 2019) and semianalytic models (e.g. Krumholz & Ting 2018).…”

Section: Introductionmentioning

confidence: 99%

“…Interestingly,Safarzadeh & Scannapieco (2017) finds that the resulting abundance patterns in a UFD candidate at high redshift are generally insensitive to the energy of the injection event. However, they focus on enrichment events from a smaller range of injection energies: 10 50 -10 51 erg.…”

mentioning

confidence: 99%

Simulating Metal Mixing of Both Common and Rare Enrichment Sources in a Low-mass Dwarf Galaxy

Emerick

Bryan

Low

2020

ApJ

View full text Add to dashboard Cite

One-zone models constructed to match observed stellar abundance patterns have been used extensively to constrain the sites of nucleosynthesis with sophisticated libraries of stellar evolution and stellar yields. The metal mixing included in these models is usually highly simplified, although it is likely to be a significant driver of abundance evolution. In this work we use high-resolution hydrodynamics simulations to investigate how metals from individual enrichment events with varying source energies E ej mix throughout the multi-phase interstellar medium (ISM) of a low-mass (M gas = 2 × 10 6 M ), low-metallicity, isolated dwarf galaxy. These events correspond to the characteristic energies of both common and exotic astrophysical sites of nucleosynthesis, including: asymptotic giant branch winds (E ej ∼10 46 erg), neutron star-neutron star mergers (E ej ∼10 49 erg), supernovae (E ej ∼10 51 erg), and hypernovae (E ej ∼10 52 erg). We find the mixing timescales for individual enrichment sources in our dwarf galaxy to be long (100 Myr-1 Gyr), with a clear trend of increasing homogeneity for the more energetic events. Given these timescales, we conclude that the spatial distribution and frequency of events are important drivers of homogeneity on large scales; rare, low E ej events should be characterized by particularly broad abundance distributions. The source energy E ej also correlates with the fraction of metals ejected in galactic winds, ranging anywhere from 60% at the lowest energy to 95% for hypernovae. We conclude by examining how the radial position, local ISM density, and global star formation rate influence these results.

show abstract

“…These would come from performing high resolution zoom cosmological simulations on UFD host halos while modeling the candidate DNSs as r -process sources with their characteristic natal kicks and merging times. While we have shown in Safarzadeh & Scannapieco (2017) that a single NSM event can explain Reticulum II like systems, these sets of simulations are vital to perform, since otherwise the impact of natal kicks remains unclear. The ejected r -process material might not get effectively recycled into the new generation of the stars (Macias & Ramirez-Ruiz 2018).…”

Section: Tucana III Progenitor Stellar Massmentioning

confidence: 99%

“…Separately, through cosmological zoom simulations of UFDs, Safarzadeh & Scannapieco (2017) demonstrated that a single NSM event can account for the observed r -process enrichment in Reticulum II, with modest assumptions regarding the europium yield in the dynamical ejecta of the NSM. However, the authors had to make the NSM event take place in less than about 10 Myr after the onset of star formation in the UFDs so that the subsequent generation of stars can inherit the r -process ejected into the interstellar medium (ISM) before the total stellar mass of the system reaches M ≈ 10 4 M .…”

Section: Introductionmentioning

confidence: 99%

r-process Enrichment of the Ultra-faint Dwarf Galaxies by Fast-merging Double-neutron Stars

Safarzadeh

Ramírez-Ruiz

Andrews

et al. 2019

ApJ

Self Cite

View full text Add to dashboard Cite

The recent aLIGO/aVirgo discovery of gravitational waves from the neutron star merger (NSM) GW170817 and the follow up kilonova observations have shown that NSMs produce copious amount of r -process material. However, it is difficult to reconcile the large natal kicks and long average merging times of Double Neutron Stars (DNSs), with the levels of r -process enrichment seen in ultrafaint dwarf (UFD) galaxies such as Reticulum II and Tucana III. Assuming that such dwarf systems have lost a significant fraction of their stellar mass through tidal stripping, we conclude that contrary to most current models, it is the DNSs with rather large natal kicks but very short merging timescales that can enrich UFD-type galaxies. These binaries are either on highly eccentric orbits or form with very short separations due to an additional mass-transfer between the first-born neutron star and a naked helium star, progenitor of the second-born neutron star. These DNSs are born with a frequency that agrees with the statistics of the r -process UFDs, and merge well within the virial radius of their host halos, therefore contributing significantly to their r -process enrichment. arXiv:1810.04176v2 [astro-ph.HE]

show abstract

Simulating neutron star mergers as r-process sources in ultrafaint dwarf galaxies

Cited by 58 publications

References 71 publications

Neutron Star Mergers Might Not Be the Only Source of r-process Elements in the Milky Way

Neutron Star Mergers Might Not Be the Only Source of r-process Elements in the Milky Way

Simulating Metal Mixing of Both Common and Rare Enrichment Sources in a Low-mass Dwarf Galaxy

r-process Enrichment of the Ultra-faint Dwarf Galaxies by Fast-merging Double-neutron Stars

Contact Info

Product

Resources

About