Kavli Affiliate: Hsiaowen Chen
|Summary:In dwarf galaxy models, outflows expel metal-enriched interstellar medium (ISM) into the circumgalactic medium (CGM) to reproduce their observed low metallicities, but measurements of dwarf CGM properties are scarce. We present a study of the CGM of an isolated dwarf at $z=0.5723$ with a stellar mass of $approx5times10^7rm,M_odot$ and star-formation rate ($approx0.05,rm M_odot,yr^-1$) and ISM metallicity ($rm [O/H]approx-0.9$) consistent with the star-forming main sequence and mass-metallicity relation. A background quasar sightline with archival UV spectra probes the dwarf’s CGM at a projected distance of 28 kpc, corresponding to approximately half of the estimated virial radius. The dwarf’s CGM is detected in ionH1, intermediate metal ions of ionC3, ionO3, ionO4, and textcolorblackionS5, and kinematically broader, highly-ionized ionO6, but is undetected in ionN4 and ionNe8. Photoionization modeling of the intermediate ions indicates a modest volume-filling factor ($sim 6%$ along the sightline or $sim 2%$ globally), and a mass of $sim2times10^8 rm,M_odot$, $sim4times$ higher than the dwarf’s stellar mass, but $sim10times$ less than the highly ionized CGM. The ionO6 kinematics are comparable to the dwarf’s estimated virial velocity, suggesting it is likely associated with cool, photoionized, and volume-filling CGM, with bulk motion or turbulence dominating over thermal pressure. The metallicity inferred for the intermediate ions is $rm [O/H]=-0.6$, but with low relative abundances of $rm [C/O]=-0.6$ and textcolorblack$rm [N/O]<-1.0$. The [N/O] is below levels expected of the dwarf’s ISM, but consistent with core-collapse supernova ejecta, suggesting that supernova-enriched gas escaped the dwarf without mixing significantly with ISM enriched in nitrogen from evolved, low-mass stars.| Search Query: arXiv Query: search_query=au:”Chen Hsiao-wen”&id_list=&start=0&max_results=10Read More