Doug Finkbeiner - the Fermi Bubbles
- Discovered bubbles
- many explanations... e- e+, protons, agn, sf
- "evidence for" but not "discovery of" a jet
9:30-9:50 am Mateusz Ruszkowski (USA): The Fermi Bubbles: Gamma-ray, Microwave, and Polarization Signatures of Leptonic AGN Jets (15 + 5 minutes)
- Using simulation to fit to the fermi bubble
- "double jet" much better fit than single
9:50-10:10 am Brian Lacki (USA): Sturm und Drang: The Turbulent, Magnetic Tempest in the Galactic Center (15 + 5 minutes)
- Pressure balance
- equipartition in MW
- 100x in CMZ
- 1000x in M82, 1e6x in Arp 220 + yet still equipartition
- turbulence dissipates in a flow-crossing time + turbulent plasma drives b-field toward equipart
- Q Steve: What is your outer scale? Most of molecular gas at radii of 100pc...
- A: radii go outward... thickness of disk in 3D turbulence sets your upper scale.
11:15-11:40 am Timothy Linden (USA): Dark Matter in the Galactic Center (20 + 5 minutes)
- Dark matter cross-section
- significant only as a nonthermal energy source
- dark matter is the source of electrons in the nonthermal filaments (Linden 2011)
- Q Gillessen: Does NFW fit Fermi?
- A: Yes, but requires adiabatic contraction and almost doesn't fit
- Q: Baganoff: What is the dark matter energy injection?
- A: 10^36 erg/s over 1 degree in 1-10 GeV electrons
- Q: Wardle: predict sharp spectral cutoff below 100 GHz.
- A: MHD makes filament, dark matter feeds electrons into it. Need to find sharp turnover
- Q Farhad: Only a few nonthermal filaments have X-ray counterparts. Maybe a result of interaction.
- A: Filaments will be hardest where they are dimmest
11:40-12:00 pm Chris Gordon (UK): Dark Matter and Pulsar Model Constraints from Galactic Center Fermi-LAT Gamma Ray Observations (15 + 5 minutes)
12:20-12:40 pm Miwa Goto (Germany): The cosmic-ray ionization rate in the Central parsec of the Galaxy - how we could deal with 10^4 discrepancy? (15 + 5 minutes)
- CR rate 1.6e-15 near Sgr A*
- disk CR rate: ~1x10-17
- Uncertainties in extrapolated CR spectrum
- Chemistry may be way off
2:00-2:20 pm Andrew Lehmann (Australia): The Galactic Centre molecular cloud G0.13-0.13: a laboratory for understanding cosmic-ray electron acceleration and
- Clouds fluoresce in 6.4 keV Fe K-alpha line
- electrons from either SN or arc
- electron losses very fast at low energies + only high energies can penetrate the cloud + Arc electrons higher energy, penetrate further
- Q: how do electrons escape? field line diffusion? wandering?
- A: Unknown
- Q: B-field?
- A: Turbulent, so diffusion holds
2:20-2:40 pm Chuck Hailey (USA): First Results from the NuSTAR "Mini-Survey" of the Galactic Center Region (15 + 5 minutes)
- cannonball: not detected, swamped
- x-ray filament
- "GeV results for the PWN in the CMZ"
- Sgr A-E a magnetic flux tube? + Where do you get 50 TeV electrons?
- HESS TeV source: everything >40 keV is from a pwn + INTEGRAL source was an artifact
3:30-3:55 pm Shep Doeleman (USA): Science with the Event Horizon Telescope (20 + 5 minutes)
- pierce the scattering screen
- intrinsic size larger than scattering
3:55-4:15 pm Geoff Bower (USA): The Galactic Center Pulsar, SGR 1745-29 (15 + 5 minutes)
- Limit of 20% on pointlike contribution to Sgr A* emission
Diffuse X-rays in the CMZ / NIR comparison
- "GCDX"
- 7x10^7 K gas.
- gas can freely escape
- extinction-corrected stellar number density map
- awesome extinction-polarization maps + Hatano et al2013
Discussion
Farhad: Morphology in inner 1.5" "Missing Pulsar" problem. Dispersion Measure problem: hard to see pulsars
5:00-5:25 pm Mitch Begelman (USA): Symposium Summary (25 minutes)
- "Maybe the solar system is in the Galactic center..."
- Galactic "Center": dynamical
- CMZ: Characterized by physical conditions - amount of molecular gas and extreme conditions
- CMZ vs starbursts: 10-100x lower pressure, 10^-4 gamma rays
- CMZ disagrees with "sacred" KS law (or Krumholz-McKee law)
- Supsersonic turbulence accepted in the CMZ... not in Mitch's circles
- intermittent SF: turbulent, cloud-cloud collisions
- turbulent clouds are transient
- starbursts = global conditions, local: cloud collisions
- pressure gradient in the CMZ -> wind
- could wind-strength be the trigger? + put threshold at 10x tidal limit + wind luminosity required = L_w = 10 (c_s^2 sigma^3 / G) T_100 sigma_150^3 erg/s + bimodal: feedback drives further SF
- CND - CMZ connection...
- Central nuclear cluster: formed from binaries? + tidal limit on SF + tidal compression -> tiny jeans mass
- G2 + Mitch thinks it contains a star + high eccentricity means hard to form close-in + plausible star with 50km/s 10^-7 msun/yr