r -process enrichment of the lightest galaxies by fast merging - - PowerPoint PPT Presentation

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Oct 09, 2022 144 likes •413 views

r -process enrichment of the lightest galaxies by fast merging neutron star binaries Mohammad Safarzadeh with: Evan Scannapieco, Enrico Ramirez-Ruiz, Rick Sarmento, Jeff Andrews, Tassos Fragos, Philip Macias JINA, Sep 28th, 2018 Arizona

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r-process enrichment of the lightest galaxies by fast merging neutron star binaries

with: Evan Scannapieco, Enrico Ramirez-Ruiz, Rick Sarmento, Jeff Andrews, Tassos Fragos, Philip Macias

Arizona State University

JINA, Sep 28th, 2018

Mohammad Safarzadeh

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The observed statistics of r-process enrichment in the local universe points to the need for fast merging neutron star mergers!

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How to study the sources of r-process elements in the early universe?

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bserve old (metal poor) stars that are

r-process enhanced

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Where are r-process metal poor stars?

MW’s halo Ultra Faint Dwarf galaxies

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Ultra Faint Dwarf galaxies

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Bechtol et al. 2015

Reticulum II UFDs: Dead, dark matter dominated, least luminous, least chemically evolved systems

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Bechtol et al. 2015

Reticulum II UFDs: Dead, dark matter dominated, least luminous, least chemically evolved systems

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Reticulum II

Ji et al. (2016) 9 stars with high abundance of R-process elements such as Eu and Ba. Ret II is a local UFD.

Reticulum II r-process abundance

Ji et al. (2016)

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Zoom cosmological simulation of a MW type halo, tracking r-process enrichment

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Results from zoom cosmological simulation of an ultra faint galaxy

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Ret II stars Simulation stellar particles Comparing the results to Ret II

MTS & Scannapieco (2017)

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Comparing the results to Ret II

MTS & Scannapieco (2017)

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z=12.9 z=12.7

Off-center explosion

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z=12.9 z=12.7

z=12.7

Off-center explosion

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How can a NSM event enrich a galaxy?

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Results from a distance cut on the NS binaries.

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MTS, Ramirez-Ruiz et al. (2018)

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Fast merging channel of NS binaries

Highly eccentric

rbits

Case BB unstable mass transfer

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Case BB unstable mass transfer

Chruslinska+18

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Case BB unstable mass transfer

Chruslinska+18

No CE simulation successfully ejects the envelope!

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MTS, Ramirez-Ruiz et al. (to be submitted)

Tucana III progenitor stellar mass Ret II progenitor stellar mass

20% of UFDs are r-process enriched

Case BB eccentric orbit

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What is next?

Perform the same simulations on a suite of MW type halos to

btain a robust halo-to-halo scatter

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Naiman et al., 2018

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Performing cosmological zoom simulation of r- process enrichment on a MW type halo MTS, sarmento & Scannapieco., in prep

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Summary

A single NSM event in star formation history of a UFD is

compatible with Ret II observations.

r-process enrichment efficiency is highly dependent on the

location of NSM event, therefore natal kicks play a crucial role.

Fast merging channels are crucial to explain Ret II like systems.
Case BB unstable mass transfer
Highly eccentric orbits