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Title: A Comprehensive Investigation of Metals in the Circumgalactic Medium of Nearby Dwarf Galaxies

Dwarf galaxies are found to have lost most of their metals via feedback processes; however, there still lacks consistent assessment on the retention rate of metals in their circumgalactic medium (CGM). Here we investigate the metal content in the CGM of 45 isolated dwarf galaxies withM*= 106.5–9.5M(M200m= 1010.0–11.5M) using the Hubble Space Telescope/Cosmic Origins Spectrograph. While Hi(Lyα) is ubiquitously detected (89%) within the CGM, we find low detection rates (≈5%–22%) in Cii, Civ, Siii, Siiii, and Siiv, largely consistent with literature values. Assuming these ions form in the cool (T≈ 104K) CGM with photoionization equilibrium, the observed Hiand metal column density profiles can be best explained by an empirical model with low gas density and high volume filling factor. For a typical galaxy withM200m= 1010.9M(median of the sample), our model predicts a cool gas mass ofMCGM,cool∼ 108.4M, corresponding to ∼2% of the galaxy’s baryonic budget. Assuming a metallicity of 0.3 Z, we estimate that the dwarf galaxy’s cool CGM likely harbors ∼10% of the metals ever produced, with the rest either in more ionized states in the CGM or transported to the intergalactic medium. We further examine the EAGLE simulation and show that Hiand low ions may arise from a dense cool medium, while Civarises from a diffuse warmer medium. Our work provides the community with a uniform data set on dwarf galaxies’ CGM that combines our recent observations, additional archival data and literature compilation, which can be used to test various theoretical models of dwarf galaxies.

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Author(s) / Creator(s):
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DOI PREFIX: 10.3847
Date Published:
Journal Name:
The Astrophysical Journal
Medium: X Size: Article No. 55
["Article No. 55"]
Sponsoring Org:
National Science Foundation
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