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NGC 1275
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Perseus-Pisces Supercluster, 75 Mpc, mass ~8×1015 Msun
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Perseus Cluster, 75 Mpc, 500 galaxies, M~2×1015 Msun
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NGC 1275
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H I, He I recombination, low ionization lines, [N I]
Inverted ionization ratios
Unlike any starlight-ionized nebulae Hatch+ in
preparation
(Å)
[O II]
H I [N I]
H I
H I [O I] [S II]
H I + [N II]
He I
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Strong H2 lines in IR
Johnstone et al 2007, MNRAS, 382, 1246
H2 H2
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CO lines: Mmolecule ~ 1011 Msun
Salome et al 2006, A&A, 454, 4376
CO 1-0
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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
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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
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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
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ν f
ν [
erg
cm
-2 s
-1]
10−3
0.01
0.1
1
10
100 1000
ν f
ν [e
rg c
m-2 s
-1]
10−4
10−3
0.01
0.1
1
10
100
Wavelength (μm)
1 10 100 1000
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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?
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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
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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
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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
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These three processes produce very different ionization ratios
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Photons vs particles
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Photons vs particles
Photoionization – RR&DR electron recombination rates ~10-13 cm3 s-1,
photoionization cross sections few megabarns
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Photons vs particles
Ionizing particles – O, N ionization strongly coupled to H by resonant
charge exchange
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Thermal vs ionizing particles
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Thermal vs ionizing particles
Recombination by
CX, RR, DR Electron impact
ionization with
Boltzmann factors
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The curious ionization ratios are produced by ionizing
particles entering molecular gas
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Observed / predicted spectrum
wavelength (microns)
1 10
pre
dic
ted / o
bse
rve
d
0.1
1
10
H I, [N I],
He I, [O I],
[N II], [S II] H2 H2, [Ne II]
Ferland+ 2009MNRAS.392.1475F
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Predicted spectrum
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Optical/UV spectrum
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Radio
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X-ray
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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