Molecular tracers in the Galaxy (and beyond…) Willem Baan 1 & Edo Loenen 1,2 1 ASTRON, 2 Kapteyn Astronomical Institute

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 => Galactic properties => nearby extragalactic => distant galaxies First Onsala narrow-band sample (ongoing analysis) ‏ – 32 CS-selected H II regions along Galactic plane – HCN, HNC, HCO +, 13 CO, C 18 O, HNCO, N2H +, CN, CS First Mopra broad-band sample (being reduced) ‏ – 7 cores in CMZ, 28 in G333.3, 15 H II regions – 4 broadband windows covering GHz

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/HCN ratios (so far) unexplained Enhanced cosmic ray flux? Hot Core chemistry? Extra-Galactic Galactic

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!

ExtraGalactic: Density Evolution (ongoing) ‏ decreasing L FIR 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 => evolution & depletion – HD tracers => 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) ‏

ExtraGalactic: Chemistry density physics/chemistry modeling results show distinct excitation regimes => 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: >1: X-rays (XDRs) ‏ 0.5 – 1: UV (young PDRs) ‏ < 0.5: UV + added mechanical heating (SNe, older PDRs) ‏ low high

Our wishes for a Mopra Milky Way Survey Broad-band GHz to include: – 29 SiO, 30 SiO, HC 18 O +, SiO, NH 2 D, H 13 CN, HCO, H 13 CO +, HC 17 O +, HN 13 C, HNCO, CH 3 OH, HCN, H 15 NC, HCN, HCO +, HOC +, HNC, … combined with GHz for CN lines, CO, 13 CO, and C 18 O To include weaker lines => 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 !!