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Title: Are the Formation and Abundances of Metal-poor Stars the Result of Dust Dynamics?

Abstract

Large dust grains can fluctuate dramatically in their local density, relative to the gas, in neutral turbulent disks. Small, high-redshift galaxies (before reionization) represent ideal environments for this process. We show via simple arguments and simulations that order-of-magnitude fluctuations are expected in local abundances of large grains (>100 Å) under these conditions. This can have important consequences for star formation and stellar metal abundances in extremely metal-poor stars. Low-mass stars can form in dust-enhanced regions almost immediately after some dust forms even if the galaxy-average metallicity is too low for fragmentation to occur. We argue that the metal abundances of these “promoted” stars may contain interesting signatures as the CNO abundances (concentrated in large carbonaceous grains and ices) and Mg and Si (in large silicate grains) can be enhanced and/or fluctuate almost independently. Remarkably, the otherwise puzzling abundance patterns of some metal-poor stars can be well fit by standard IMF-averaged core-collapse SNe yields if we allow for fluctuating local dust-to-gas ratios. We also show that the observed log-normal distribution of enhancements in pure SNe yields, shows very large enhancements and variations up to factors of ≳100 as expected in the dust-promoted model, preferentially in the [C/Fe]-enhanced metal-poor stars. Together, thismore » suggests that (1) dust exists in second-generation star formation, (2) local dust-to-gas ratio fluctuations occur in protogalaxies and can be important for star formation, and (3) the light element abundances of these stars may be affected by the local chemistry of dust where they formed, rather than directly tracing nucleosynthesis from earlier populations.« less

Authors:
 [1];  [2]
  1. TAPIR, Mailcode 350-17, California Institute of Technology, Pasadena, CA 91125 (United States)
  2. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
Publication Date:
OSTI Identifier:
22663958
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 835; 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; DUSTS; ELEMENT ABUNDANCE; FLUCTUATIONS; FRAGMENTATION; GALAXIES; ICE; MASS; METALLICITY; METALS; NUCLEOSYNTHESIS; RED SHIFT; SILICATES; SIMULATION; STARS; TURBULENCE; VISIBLE RADIATION

Citation Formats

Hopkins, Philip F., and Conroy, Charlie, E-mail: phopkins@caltech.edu. Are the Formation and Abundances of Metal-poor Stars the Result of Dust Dynamics?. United States: N. p., 2017. Web. doi:10.3847/1538-4357/835/2/154.
Hopkins, Philip F., & Conroy, Charlie, E-mail: phopkins@caltech.edu. Are the Formation and Abundances of Metal-poor Stars the Result of Dust Dynamics?. United States. doi:10.3847/1538-4357/835/2/154.
Hopkins, Philip F., and Conroy, Charlie, E-mail: phopkins@caltech.edu. Wed . "Are the Formation and Abundances of Metal-poor Stars the Result of Dust Dynamics?". United States. doi:10.3847/1538-4357/835/2/154.
@article{osti_22663958,
title = {Are the Formation and Abundances of Metal-poor Stars the Result of Dust Dynamics?},
author = {Hopkins, Philip F. and Conroy, Charlie, E-mail: phopkins@caltech.edu},
abstractNote = {Large dust grains can fluctuate dramatically in their local density, relative to the gas, in neutral turbulent disks. Small, high-redshift galaxies (before reionization) represent ideal environments for this process. We show via simple arguments and simulations that order-of-magnitude fluctuations are expected in local abundances of large grains (>100 Å) under these conditions. This can have important consequences for star formation and stellar metal abundances in extremely metal-poor stars. Low-mass stars can form in dust-enhanced regions almost immediately after some dust forms even if the galaxy-average metallicity is too low for fragmentation to occur. We argue that the metal abundances of these “promoted” stars may contain interesting signatures as the CNO abundances (concentrated in large carbonaceous grains and ices) and Mg and Si (in large silicate grains) can be enhanced and/or fluctuate almost independently. Remarkably, the otherwise puzzling abundance patterns of some metal-poor stars can be well fit by standard IMF-averaged core-collapse SNe yields if we allow for fluctuating local dust-to-gas ratios. We also show that the observed log-normal distribution of enhancements in pure SNe yields, shows very large enhancements and variations up to factors of ≳100 as expected in the dust-promoted model, preferentially in the [C/Fe]-enhanced metal-poor stars. Together, this suggests that (1) dust exists in second-generation star formation, (2) local dust-to-gas ratio fluctuations occur in protogalaxies and can be important for star formation, and (3) the light element abundances of these stars may be affected by the local chemistry of dust where they formed, rather than directly tracing nucleosynthesis from earlier populations.},
doi = {10.3847/1538-4357/835/2/154},
journal = {Astrophysical Journal},
number = 2,
volume = 835,
place = {United States},
year = {Wed Feb 01 00:00:00 EST 2017},
month = {Wed Feb 01 00:00:00 EST 2017}
}
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