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Origins of carbon-enhanced metal-poor stars.

Sharma, Mahavir and Theuns, Tom and Frenk, Carlos S. and Cooke, Ryan J. (2018) 'Origins of carbon-enhanced metal-poor stars.', Monthly notices of the Royal Astronomical Society., 473 (1). pp. 984-995.

Abstract

We investigate the nature of carbon-enhanced metal-poor (CEMP) stars in Milky Way (MW) analogues selected from the EAGLE cosmological hydrodynamical simulation. The stellar evolution model in EAGLE includes the physics of enrichment by asymptotic giant branch (AGB) stars, winds from massive stars, and Type Ia and Type II supernovae (SNe). In the simulation, star formation in young MW progenitors is bursty due to efficient stellar feedback, which enables poor metal mixing leading to the formation of CEMP stars with extreme abundance patterns. Two classes of CEMP stars emerge: those mostly enriched by low-metallicity Type II SNe with low Fe yields that drive galactic outflows, and those mostly enriched by AGB stars when a gas-poor galaxy accretes pristine gas. The first class resembles CEMP-no stars with high [C/Fe] and low [C/O], the second class resembles CEMP-s stars overabundant in s-process elements and high values of [C/O]. These two enrichment channels explain several trends seen in data: (i) the increase in the scatter and median of [C/O] at low and decreasing [O/H], (ii) the trend of stars with very low [Fe/H] or [C/H] to be of type CEMP-no and (iii) the reduction in the scatter of [α/Fe] with atomic number in metal-poor stars. In this interpretation, CEMP-no stars were enriched by the stars that enabled galaxies to reionize the Universe.

Item Type:Article
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.1093/mnras/stx2392
Publisher statement:This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:12 September 2017
Date deposited:25 January 2018
Date of first online publication:16 September 2017
Date first made open access:25 January 2018

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