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ABSTRACT 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, while classical dwarfs ($$M_{\ast }\gt 10^{5}\, \mathrm{M}_{\odot }$$) continue forming stars to z < 0.5. The systems have bursty star formation histories, forming most of their stars in periods of elevated SF strongly clustered in both space and time. This allows our dwarf with M*/Mhalo > 10−4 to form a dark matter core $${\gt}200\rm \, pc$$, while lower mass UFDs exhibit cusps down to $${\lesssim}100\rm \, pc$$, as expected from energetic arguments. Our dwarfs with $$M_{\ast }\gt 10^{4}\, \mathrm{M}_{\odot }$$ have half-mass radii (R1/2) in agreement with Local Group (LG) dwarfs (dynamical mass versus R1/2 and stellar rotation also resemble observations). The lowest mass UFDs are below surface brightness limits of current surveys but are potentially visible in next-generation surveys (e.g. LSST). The stellar metallicities are lower than in LG dwarfs; this may reflect pre-enrichment of the LG by the massive hosts or Pop-III stars. Consistency with lower resolution studies implies that our simulations are numerically robust (for a given physical model).
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The orbit and stellar masses of the archetype colliding-wind binary WR 140
ABSTRACT We present updated orbital elements for the Wolf–Rayet (WR) binary WR 140 (HD 193793; WC7pd + O5.5fc). The new orbital elements were derived using previously published measurements along with 160 new radial velocity measurements across the 2016 periastron passage of WR 140. Additionally, four new measurements of the orbital astrometry were collected with the CHARA Array. With these measurements, we derive stellar masses of $$M_{\rm WR} = 10.31\pm 0.45 \, \mathrm{M}_\odot$$ and $$M_{\rm O} = 29.27\pm 1.14 \, \mathrm{M}_{\odot }$$. We also include a discussion of the evolutionary history of this system from the Binary Population and Spectral Synthesis model grid to show that this WR star likely formed primarily through mass-loss in the stellar winds, with only a moderate amount of mass lost or transferred through binary interactions.
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- PAR ID:
- 10253399
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 504
- Issue:
- 4
- ISSN:
- 0035-8711
- Page Range / eLocation ID:
- 5221 to 5230
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1093/mnras/stab1181
