Molecular tracers in the Galaxy and beyond

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Molecular tracers in the Galaxy (and beyond)
Willem Baan1 Edo Loenen1,2 1ASTRON, 2Kapteyn
Astronomical Institute
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Galactic Molecular Survey (in progress)?

• Objectives (1) to understand physical and
  chemical conditions of molecular gas by using
  multiple-molecule multiple-line analysis (2)
  integrate with physical/chemistry modeling (see
  Meijerink etal 05,06,07)(3) bootstrap gt
  Galactic properties gt nearby extragalactic
  gt distant galaxies
• First Onsala narrow-band sample (ongoing
  analysis)?
• 32 CS-selected HII regions along Galactic plane
• HCN, HNC, HCO, 13CO, C18O, HNCO, N2H, CN, CS
• First Mopra broad-band sample (being reduced)?
• 7 cores in CMZ, 28 in G333.3, 15 HII regions
• 4 broadband windows covering 84 - 116 GHz

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Preliminary results (Onsala Data)?

• data shows global trends in line ratios
• strong similarity with extra- galactic sources
• ratios can be explained using extensive
  physics/chemistry modeling
• diagnostics of excitation/heating conditions
• very low HNC/HCNratios (so far) unexplained
• Enhanced cosmic ray flux? Hot Core chemistry?

Extra-Galactic Galactic
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Preliminary results (Onsala Data)?

• HNC/HCN line ratio changes as function of
  distance to Galactic Center!
• Large scale change of physical environment along
  the Milky Way
• Cosmic Ray flux is possible cause
• many more molecules to analyze just the tip of
  the iceberg!

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ExtraGalactic Density Evolution (ongoing)?

• Large database (nearby active galaxies) (Baan
  etal 2008)?
• low density gas CO(1-0) CO(2-1)?
• high density gas HCN(1-0), HNC(1-0), HCO(1-0),
  CN(1-0), CN(2-1), CS(3-2)?
• Comparison with physics/chemistry modeling
  (Loenen etal 2008)?
• Large differentiation in line ratios
• HD vs LD tracers gt evolution
• depletion
• HD tracers gt chemistry effects
• Evidence for chemical evolution of
• galaxies during FIR/starburst
• Higher HCO/HCN at lower LFIR
• indicates evolution (Baan etal 2008)?
• (filled symbols are ULIRGs/OH MM)?

decreasing LFIR
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ExtraGalactic Chemistry

• physics/chemistry modeling results show distinct
  excitation regimes gt color tracks in
  diagnostic diagrams (Loenen et al 08, 09)?
• differentiation in HD line ratios due to density
  and nature of heating source
• HCO/HCN and HCO/HNC ratios sensitive to density
• HNC/HCN ratio sensitive to heating source
• gt1 X-rays (XDRs)?
• 0.5 1 UV (young PDRs)?
• lt 0.5 UV added mechanical heating (SNe, older
  PDRs)?

density
low
high
low
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Our wishes for a Mopra Milky Way Survey

• Broad-band 84-92 GHz to include
• 29SiO, 30SiO, HC18O, SiO, NH2D, H13CN, HCO,
  H13CO , HC17O, HN13C, HNCO, CH3OH, HCN, H15NC,
  HCN, HCO, HOC, HNC,
• combined with 108-116 GHz for CN lines, CO, 13CO,
  and C18O
• To include weaker lines gt longer integration
  times
• Survey on selected sources instead of OTF to
  investigate chemical changes between different
  regions?
• mapping of interesting region (Galactic Center?,
  strip along/through Galactic Plane?)?
• On-the-fly mapping not sufficient
• There must be sufficient line information to do
  new physics !!