Susanne Aalto: Physical Conditions and Chemistry of Molecular Gas in Galactic Centers

Physical conditions & chemistry

Astrochemistry as a diagnostic...
  • 50+ molecules detected exgalactically
  • CO n>10^2, HCN n>10^4
  • temperature NH3, H2CO
  • Only works if molecules excited by collisions
  • 12CO/13CO increases towards GC because more diffuse gas [my q: integrated?]
"Raisin Roll" view:
  • Mol massin dense clumps, HI diffuse throughout
  • HCO+, H3O+, HNC, HC3N, CN, SiO, H2O
General Trends
  • HNC 1-0 anticorrelated with HCN+ 1-0
  • C2H ubiquitous
"Hot Cores"
  • Arp 220
  • Drive outflows
  • "Boring" NGC 1377 (optically) + has very deep SiO absorption + molecular outflow M~10^7 Msun + 860um optically thick core
  • NGC 4418 "Ugly Duckling" galaxy + optically thick "atmosphere" dust core surrounded by molecular disk + N~10^25 cm^-2 + inner temp ~200-300K + molecular "disk" ~50K
  • unclear how common optically thick cores are + can be studied with vibrationally excited molecules
  • NGC 4418 + Global spectrum dominated by vibrationally excited HC3N
  • Mrk231 + HCN outflow, 1000 km/s + vibrationally excited HCN in core
  • vibrationally excited lines trace warped disk
  • Arp 220W: amplified IR-pumped HNC
ALMA NGC 4418 "spectral scan"
  • dominated by vibrational lines
SMA spectral scanning in Arp 220
  • problematic: wide lines
  • vibrational lines are the new standard
Less obscured galaxies
  • NGC 253, IC 342, Maffei 2, NGC 1068...
  • same chemistry can trace outflows or star formation
  • HNC, HCN, HCO+ correlated with 3mm continuum: trace SF
  • HNCO, CH3OH, SiO anti-correlated with SF: probably trace outflows
  • N2H+ - "warm gas" and "warm dust". Not the same in our galaxy & others
NGC 1068
  • PdBI Spirals around center
  • ALMA bar + spirals + central cirumnuclear disk
  • complicated chemistry towards true center
  • noncircular motions
More results:
  • ALMA + ATCA towards Cen A
  • NGC 1097
  • HC3N in Mrk 231
  • HCN in wind... extreme hcn abundance

Questions:

  • Inner NGC 1068 ring - what resolution can you get with ALMA? Can you see kinematics?
  • A: Yes, can see kinematics. 0.1", can do ~10x better eventually. 400 km/s
  • Draw attention to MOPRA MALT-90: good comparison survey for galaxies
  • Thanks

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