2021 Fiscal Year Annual Research Report
Galactic Outflow Production of Multiphase Gas in the Circumgalactic Medium
| Project/Area Number |
19K03911
|
|---|
| Research Institution | Shinshu University |
|---|
Principal Investigator |
藤田 あき美 信州大学, 学術研究院工学系, 講師 (50729506)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
三澤 透 信州大学, 学術研究院総合人間科学系, 教授 (60513447)
|
|---|
| Project Period (FY) |
2019-04-01 – 2022-03-31
|
| Keywords | circumgalactic medium / galactic outflows / galactic evolution / numerical simulations |
|---|
| Outline of Annual Research Achievements |
Observations at intermediate redshifts reveal the presence of numerous, compact, weak MgII absorbers with near to super-solar metallicities, often surrounded by extended regions that produce CIV and/or OVI absorption, in the circumgalactic medium at large impact parameters from luminous galaxies. Their origin and nature remains unclear. We tested our hypothesis that undetected, satellite dwarf galaxies are responsible for producing some of these weak MgII absorbers, using gas dynamical simulations of galactic outflows from a dwarf galaxy with a halo mass of 5 10^9 Msun, as might be falling into a larger L* halo at z=2. We find that thin, filamentary, weak MgII absorbers (<100 pc) are produced in two stages: 1) when shocked core collapse supernova enriched gas descending in a galactic fountain gets shock compressed by upward flows driven by subsequent SNIIs and cools (phase 1), and later, 2) during an outflow driven by Type Ia supernovae that shocks and sweeps up pervasive SNII- enriched gas, which then cools (phase 2). The MgII absorbers in our simulations are continuously generated by shocks and cooling with ~0.1-0.2 Zsun, but low column density <10^12 cm^-2. They are also surrounded by larger (0.5-1 kpc) CIV absorbers that seem to survive longer. Larger- scale (>1kpc) CIV and OVI clouds are also produced in both expanding and shocked SNII-enriched gas. Observable ion distributions from our models appear well-converged at our standard resolution (12.8pc). Our simulation highlights the possibility of dwarf galactic outflows producing highly enriched multiphase gas.
|
