Talk presented by Gary Ferland at the 17th International Conference on Atomic Processes in Plasmas, Queen's Univesrity Belfast, 19-22 July 2011.

1. NGC 1275

2. Perseus-Pisces Supercluster, 75 Mpc, mass ~8×1015 Msun

3. Perseus Cluster, 75 Mpc, 500 galaxies, M~2×1015 Msun

4. NGC 1275

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

7. CO lines: Mmolecule ~ 1011 Msun
CO 1-0
Salome et al 2006, A&A, 454, 4376

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

11. 10
1
ν fν [erg cm-2 s-1] 0.1
0.01
10−3
100 1000
100
10
ν fν [erg cm-2 s-1]
1
0.1
0.01
10−3
10−4
1 10 100 1000
Wavelength (μm)

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

17. And ionization/recombination processes
 Starlight
– Valence shell photoionization
– Radiative/dielectronic recombination
 Heat deposition
– Collisional ionization
– Radiative/dielectronic recombination
 Ionizing particles
– primary impact ionization
– secondary impact ionization, excitation,
heating
– charge exchange recombination

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

19. These three processes produce
very different ionization ratios

20. Photons vs particles

21. Photons vs particles
Photoionization – RR&DR electron recombination rates ~10-13 cm3 s-1,
photoionization cross sections few megabarns

22. Photons vs particles
Ionizing particles – O, N ionization strongly coupled to H by resonant
charge exchange

23. Thermal vs ionizing particles

24. Thermal vs ionizing particles
Recombination by Electron impact
CX, RR, DR ionization with
Boltzmann factors

25. The curious ionization ratios
are produced by ionizing
particles entering molecular gas

26. Observed / predicted spectrum
10
H I, [N I],
predicted / observed
He I, [O I], H2 H2, [Ne II]
[N II], [S II]
1
0.1
1 10
wavelength (microns)
Ferland+ 2009MNRAS.392.1475F

27. Predicted spectrum

28. Optical/UV spectrum

29. Radio

30. X-ray

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