The role of faint population III supernovae in forming CEMP stars in ultra-faint dwarf galaxies
ABSTRACT Carbon enhanced metal poor (CEMP)-no stars, a subset of CEMP stars ($\rm [C/Fe]\ge 0.7$ and $\rm [Fe/H]\lesssim -1$) have been discovered in ultra-faint dwarf (UFD) galaxies, with $M_{\rm vir}\approx 10^8{\, \mathrm{ M}_\odot }$ and $M_{\ast }\approx 10^3-10^4{\, \mathrm{ M}_\odot }$ at z = 0, as well as in the halo of the Milky Way (MW). These CEMP-no stars are local fossils that may reflect the properties of the first (Pop III) and second (Pop II) generation of stars. However, cosmological simulations have struggled to reproduce the observed level of carbon enhancement of the known CEMP-no stars. Here, we present new cosmological hydrodynamic zoom-in simulations of isolated UFDs that achieve a gas mass resolution of $m_{\rm gas}\approx 60{\, \mathrm{ M}_\odot }$. We include enrichment from Pop III faint supernovae (SNe), with ESN = 0.6 × 1051 erg, to understand the origin of CEMP-no stars. We confirm that Pop III and Pop II stars are mainly responsible for the formation of CEMP and C-normal stars, respectively. New to this study, we find that a majority of CEMP-no stars in the observed UFDs and the MW halo can be explained by Pop III SNe with normal explosion energy (ESN = 1.2 × 1051 erg) and Pop II enrichment, but faint SNe might also be needed more »
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Publication Date:
NSF-PAR ID:
10296853
Journal Name:
Monthly Notices of the Royal Astronomical Society
Volume:
502
Issue:
1
Page Range or eLocation-ID:
1 to 14
ISSN:
0035-8711
We study a suite of extremely high-resolution cosmological Feedback in Realistic Environments simulations of dwarf galaxies ($M_{\rm halo} \lesssim 10^{10}\rm \, M_{\odot }$), run to z = 0 with $30\, \mathrm{M}_{\odot }$ resolution, sufficient (for the first time) to resolve the internal structure of individual supernovae remnants within the cooling radius. Every halo with $M_{\rm halo} \gtrsim 10^{8.6}\, \mathrm{M}_{\odot }$ is populated by a resolved stellar galaxy, suggesting very low-mass dwarfs may be ubiquitous in the field. Our ultra-faint dwarfs (UFDs; $M_{\ast }\lt 10^{5}\, \mathrm{M}_{\odot }$) have their star formation (SF) truncated early (z ≳ 2), likely by reionization, whilemore »
2. ABSTRACT Carbon-enhanced metal-poor (CEMP) stars are the living fossils holding records of chemical enrichment from early generations of stars. In this work, we perform a set of numerical simulations of the enrichment from a supernova (SN) of a first generation of metal-free (Pop III) star and the gravitational collapse of the enriched cloud, considering all relevant cooling/heating processes and chemical reactions as well as the growth of dust grains. We adopt faint SN models for the first time with progenitor masses MPopIII = 13–$80 \ {\rm M_{\bigodot }}$, which yield C-enhanced abundance patterns ([C/Fe] = 4.57–4.75) through mixing and fallback of innermostmore »
3. ABSTRACT We present and study a large suite of high-resolution cosmological zoom-in simulations, using the FIRE-2 treatment of mechanical and radiative feedback from massive stars, together with explicit treatment of magnetic fields, anisotropic conduction and viscosity (accounting for saturation and limitation by plasma instabilities at high β), and cosmic rays (CRs) injected in supernovae shocks (including anisotropic diffusion, streaming, adiabatic, hadronic and Coulomb losses). We survey systems from ultrafaint dwarf ($M_{\ast }\sim 10^{4}\, \mathrm{M}_{\odot }$, $M_{\rm halo}\sim 10^{9}\, \mathrm{M}_{\odot }$) through Milky Way/Local Group (MW/LG) masses, systematically vary uncertain CR parameters (e.g. the diffusion coefficient κ and streaming velocity), andmore »