radiation field… Heating •Photoelectric dust emission •Cosmic rays •Soft X-rays •Photoionization (C I, Si I, Fe I) •Collisional ionization of H, He Cooling •Radiative line emission (e.g., C II, O I, Lya) •e- recombination onto dust Phases = complex balance on vast range of scales
• Low-energy cosmic ray propagation • X-rays from soft gamma ray repeaters • Magnetic / hydrodynamic waves • MHD turbulence • Magnetic reconnection • Shocks from: SF, HII regions, cloud collisions, Galactic dynamics, spiral arms, etc… … requiring global understanding of many different energy sources! NASA/CXC/UCSC/ L. Lopez et al. WHAM/UW-Madison NASA/Goddard Conceptual Image Lab ESA/Planck Collaboration Nature; Gaensler et al. 2011 ESA/NASA/Hubble/ AURA/NSF Heiles & Troland 2003b Amount, temperature and ionization state depend on… ``The Warm Neutral Medium is the key to the Universe.”
the magnetic field are real, cold structures • Large-scale bubbles and “chimney” breakouts illustrate Galaxy dynamics • Structure of intermed.-velocity clouds reveal role of colliding flows in phase transitions Miville-Deschenes et al. 2018
with T~20-7000 K • Turbulence, supernovae populate “unstable” regime Audit & Hennebelle 2005 Weak turbulence Pressure CNM WNM Unstable Density Density Weak turbulence Strong turbulence Density SNe driven in density peaks SNe driven randomly Gatto et al. 2015
gas” = HI + CO ‣ Optically-thick HI? ‣ H2 untraced by CO? ‣ Variations in dust grain emissivitiy? • ``Dark gas”: what is it? Planck Collaboration et al. 2011 Grenier et al. 2005 Dust rays
gas” = HI + CO ‣ Optically-thick HI? ‣ H2 untraced by CO? ‣ Variations in dust grain emissivitiy? • ``Dark gas”: what is it? Planck Collaboration et al. 2011 Murray et al. 2018a Mostly not Grenier et al. 2005 Dust rays