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The origin of the high gas temperatures in Galactic Center molecular clouds Katharina Immer ESO, Germany 09.04.2016 From Stars to Massive Stars Collaborators: J. Kauffmann (MPIfR) T. Pillai (MPIfR) A. Ginsburg (ESO) K. M. Menten (MPIfR) Motivation High gas temperatures (> 50 K) in many CMZ clouds (Ao et al. 2012, Ginsburg et al. 2016) High column densities, volume densities constrained to > 104 cm-3 Densities and temperatures comparable to those in the active regions of starburst galaxies (Mangum et al. 2013a, b) ATLASGAL, 870 μm Schuller et al. 2009 Goals Detailed gas temperature maps of seven molecular clouds in the CMZ, using the H2CO thermometer and other temperature tracers (CH3CN, CH3CCH, CH3OH) ● What is the origin of the warm gas? ● Is para-H2CO a trustworthy temperature probe? ● What is the density of the warm gas? Observations On-the-fly maps of seven clouds in the CMZ with the APEX telescope A) Observed frequency ranges: 216.9–220.9, 278.5–282.5, 290.5–294.5 GHz Covering: H2CO(3–2) and (4–3) Ka-ladders Smoothed velocity resolution: 1 km/s Smoothed beam size: ~33'' B) Observed frequency ranges: 163–167, 169.85–173.85, 175–179, 181.85–185.85, 189.9–193.9, 201.9–205.9 GHz Covering: CH3CCH(10–9) and (12-11) ladders, CH3CN(9–8) and (11–10) ladders Smoothed velocity resolution: 1.1 km/s Smoothed beam size: ~39'' Targets ATLASGAL, 870 μm Schuller et al. 2009 Dust temperatures: ~20 K Total masses: ~105 Mʘ Integrated Intensity Ratios Temperature Temperature Density Integrated Intensity Ratio Maps R321 R422 R404 20 km/s cloud -15–36 km/s G0.411+0.050 10–30 km/s Temperature Maps 218 GHz 291 GHz 20 km/s cloud -15–36 km/s G0.411+0.050 10–30 km/s Temperature vs Density Temperature vs Density Density of warm gas constrained to 104 – 106 cm-3 Temperature vs Linewidth Red: Temperatures at 218 GHz Blue: Temperatures at 291 GHz Positive correlation between temperature and linewidth → Turbulence plays an important role in the heating of the gas CH3CN/CH3CCH Temperatures G0.253+0.016 36 –42 km/s CH3CN CH3CCH TH2CO = 132 ± 3 K CH3CN/CH3CCH Temperatures CH3CN SGRC -55 – -49 km/s CH3CCH TH2CO = 63 ± 2 K Conclusion Detailed gas temperature maps of seven clouds in the CMZ with high gas temperatures ● ● ● What is the origin of the warm gas? Temperature vs linewidth correlation for H2CO line, gas seems to be pre-dominantly heated by turbulence. Is p-H2CO a trustworthy temperature probe? CH3CN and CH3CCH rotational temperature diagrams are consistent but they give different temperatures than H2CO (preliminary results!). What is the density of the warm gas? We constrain the density of the warm gas to 104 – 106 cm-3. H2CO Thermometry H2CO = slightly asymmetric rotor molecule => rotational levels split into two energy levels: JK+1K-1 Mangum & Wootten 1993: Integrated intensity ratio of two different Ka-levels of the same ΔJ=1 transition → kinetic gas temperature Integrated intensity ratio of different ΔJ=1 transitions within the same Kaladder → gas density Different Ka-ladders located close in frequency p-H2CO thermometry successfully applied to CMZ gas (Ao et al. 2012, Ginsburg et al. 2016) Velocity components in 20 km/s cloud Velocity components in G0.253+0.016 Temperature Maps – Vel. Components 0–6 km/s -3–3 km/s 8–14 km/s 16–22 km/s 27–33 km/s 36–42 km/s 75–81 km/s Temperature uncertainty maps 20 km/s cloud -15–36 km/s 0–6 km/s 8–14 km/s 27–33 km/s G0.253+0.016 G0.253+0.016 -6–54 km/s -3–3 km/s 16–22 km/s 36–42 km/s 75–81 km/s