Naomi McClure Griffiths: HI Outflows from the Galactic Center (20 + 5 minutes)

Outflows - M82 example

Our Galaxy

  • 8.3um correlated with radio continuum
  • Fermi bubbles
  • Radio polarization - magnetized bubble
  • ATCA + Parkes HI survey
  • HI data publicly available: http://arxiv.org/abs/1201.2438, http://www.atnf.csiro.au/research/HI/sgps/queryForm.html + 86 high latitude clouds that are completely distinct from the rest + ± 200 km/s + negative velocities at the bottom + size ~15 pc, ~few hundred Msun + 4000K clouds + n~1cm^-3 + not in circular orbits
Lockman "very dumb simulation"
  • model as outflowing clouds
  • wind velocity, outflow angle
  • min/max velocity plots: look for clouds beyond the min/max vel + wind velocities 150-270 km/s can reproduce population
Cooper 2008, Melioli 2013
  • simulations predict entrainment of dense gas
  • cold wind is responsible
  • 2 Myr to get clouds to observed height
Wind dynamics
  • cold clumps entrained in hot outflow total mass ~4x10^4, but completeness loss -> 10^5 msun
  • energy total ~10^52 erg
  • easily supplied by present SFR
Future
  • can look further in both lat & long + determine lifetime + constrain opening angle

Questions

  • Q: Where does the mass come from? Is it hard to resupply? Where does it go?
  • Q: Do you see any warm gas (H-alpha)?
  • A: looked at WHAM, but resolution too poor. Not clear yet.
  • Q Mitch: 600 km/s. Injected explosively or must go through a sonic point
    with a grav. potential, which would imply that it's coming from a black hole
  • A: OK, great, someone else give me the theoretical explanation
  • Q Stocke: Warm component has been detected in absorption against AGN; velocities consistent.
    Gas goes up to 12 kpc on either side and does not escape. Hot wind requires Chandra, not yet successful.
  • Q: for Stocke - How much gas in hot wind?
  • A: Not detected
  • Q: Could this be inflow?
  • A: We don't see this around other parts of the galaxy except around superbubbles. No conspiracy accreting towards CMZ
  • Q Farhad: We've looked at RRLs in inner degree. Don't see any high-velocity ionized gas. Must be accelerated away from disk.
  • Q Namir Kassim: High energy emission from cosmic rays impacting these clouds?
  • A: Possibly, we'd like to look at that more

Comments