5. [O II] H I + [N II]
HI [S II]
[O I]
HI
HI He I
[N I]
(Å)
H I, He I recombination, low ionization lines, [N I]
Inverted ionization ratios
Unlike any starlight-ionized nebulae Hatch+ in
preparation
6. Strong H2 lines in IR
H2
H2
Johnstone et al 2007, MNRAS, 382, 1246
8. Astronomical context
Atomic, molecular
gas
~70 pc wide,
6 kpc long
B~100 mG for
magnetic support
~70 km/s turbulence
Surrounded by
~5 keV gas with
nT~3×106 cm-3 K
Fabian+ 2008 Nature
9. Spectrum of a non-equilibrium gas
Detailed microphysics
Energetic radiation &
particles interact with gas
Ejected electrons heats,
excite & ionize gas
Ionization drives
chemistry
Full spectrum predicted
– Detailed chemistry, grain
physics
10. Cloudy
Follows the detailed microphysics, with
minimum compromise
All stages of ionization of the lightest 30
elements, 100+ molecules
2.7 K ≤ T ≤ 1010 K
10-10 ≤ n ≤ 1020 cm-3
Continuously maintained
Fully open source, at www.nublado.org
Ryan Porter, Peter van Hoof, Robin Williams
15. The big questions
What powers emission from the filaments?
How is the strange optical spectrum produced?
– Inverted ionization ratios, strong [N I] emission
– Strong molecular emission, including H2, CO, and
HCN
– Unlike anything seen in H II regions or planetary
nebulae
Filaments trace feedback between massive black
hole in central galaxy and the intracluster
medium. How and why?
16. Three possible energy sources
Starlight
– Photoionization as in HII regions or planetary
nebulae
Heat deposition
– dissipative MHD waves
– shocks
Ionizing particles entering molecular gas
– Intracluster medium (5 keV)
– radio lobes (MeV)
– or produced in situ
18. Ionizing particles
entering …
Ionized gas
– Heat
Atomic/molecular gas
– Shower of
suprathermal
electrons
– Secondary excitation
and ionization
– less heating
– Rich ion-molecule
chemistry
Energetic
photons
have same effects
AIRES, U Chicago
31. Conclusions
Filaments powered by penetration of surrounding
hot gas (Fabian+ 2011)
Suprathermal ionization followed by charge
transfer recombination accounts for odd spectrum
Grains must be present to sustain the rich chemistry
– Galactic origin rather than condensation from hot gas?
Composition within factor of two of ISM
Large mass deduced from CO confirmed
Large reservoirs of undetectable gas likely
Ferland et al, 2008MNRAS.386L..72F, 2009MNRAS.392.1475F