0 Assigned ID: 313 ----- Attempting Submission 1 (Thu Mar 05 21:55:58 GMT 2020) ----- HST Phase I Proposal 313 successfully submitted. Receipt: # 313-1 ----- Attempting Submission 2 (Thu Mar 05 22:34:32 GMT 2020) ----- The circumgalactic medium (CGM) and intergalactic medium (IGM) are key ingredients for the evolution of our Galaxy, providing mass reservoirs of generally metal-poor gas for continued star formation in the disk. Recent progress in understanding these processes has been stimulated by UV absorption-line studies, mostly with HST/COS, that identified chemical signatures of extended galactic halo gas. Observations and simulations suggest that density perturbations from passing satellite galaxies or Galactic outflows can trigger condensations, which cool, condense, and eventually accrete onto the Galactic plane as material for star formation. These processes are not unique to the Milky Way; they are observed in other galaxies as well. We will pursue two related theoretical objectives both analytically and numerically: (1) Explore the structure of a potential "galactopause" at which gas outflows driven by galactic star formation stall against the pressure of the CGM and IGM. Accumulation of gas at these interfaces would naturally define a sphere of influence through chemical enrichment of the IGM; (2) Explore numerically the different formation scenarios of precipitation (wakes of satellites, turbulent compressions, stagnating outflows) and estimate the rate of precipitation, including observational diagnostics. Although the evolution of gas clouds falling onto the Galactic disk has been studied before, our program differs by emphasizing initial conditions of and triggers to the formation of precipitation, key processes for cloud survival. Our studies should therefore close a gap in understanding galactic matter cycles. Fabian Heitsch (PI) - Associate Professor of Physics & Astronomy, University of North Carolina at Chapel Hill. BS 1993 (Math, Computer Science; Muenster, Germany), MS 1998 (Physics; Bonn, Germany), PhD 2001 (Astrophysics; Heidelberg, Germany). Research interests are in computational studies of galactic matter cycles (molecular cloud and star formation, gas accretion mechanisms), in plasma astrophysics (non-ideal magnetohydrodynamics, reconnection in partially ionized gases), in method development (gas-kinetic fluid solvers), and in developing "observational" diagnostics from simulation data (polarization maps, emisison/absorption lines). Heitsch has been working with fluid codes since 1998 (ZEUS, Proteus, Athena, Athena++). Michael Shull (Co-PI) - Professor of Astrophysics, University of Colorado. BS 1972 (Physics, Caltech), PhD 1976 (Physics, Princeton). Research interests are in theoretical astrophysics and UV/X-ray space astronomy. Shull was a member of the COS-GTO team that designed and built the Cosmic Origins Spectrograph and a member of the FUSE science team. Recent studies include COS surveys of missing baryons, O VI and other metals, the He II epoch of reionization, Galactic halo gas and high-velocity clouds, high-redshift galaxies, and quasars (composite ionizing continuum and broad emission lines). Theoretical interests include interstellar radiative shocks, supernovae, ionizing photons from massive stars, reionization epochs of H and He, and cosmological simulations of IGM and galaxy formation. Intergalactic Medium and the Circumgalactic Medium Galaxies 0 Regular false false false true false SUPPORTED