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Studies of Molecular MegaMasers

Studies on OH and H2O ground state transitions and some upper states reveal high-gain components without diffuse counterparts, extended regions, and diagnostic limitations. These masers can trace SF regions, cold/warm molecular gas, and background amplification.

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Studies of Molecular MegaMasers

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  1. Studies of Molecular MegaMasers • OH = groundstate transitions & some upper states • Nucleus emission powered by nuclear starburst, or by hybrid with AGN • EVN will lose 50% or more of SD flux • High-gain components seen – no diffuse component • Extended 100 pc or more regions • Tracing SF regions w FIR pumped molecular regions • Background amplification • Mixture of massive stars, supernovae, shocked regions, outflows, and cold and warm molecular gas • Limited diagnostics • OH-MM with 100pc region with ten beams across • EVN z = 0.033, EVN+Sh/Ur z = 0.1, EVN+VLBA z = 1.7

  2. Studies of Molecular MegaMasers • H2O = 22 GHz transition & higher • Nucleus emission powered by AGN • EVN will keep most of of SD flux • Compact high-gain regions including few pc disks • Tracing AGN accretion process pumped by X-rays • Tracing collisional pumping in impact regions of jets or shocked molecular regions or SF regions • Excitation state of molecular emission not clear yet • Amplification of background continuum plays role • Limited diagnostics • OH-MM with 100pc region with ten beams across • EVN z = 0.015, EVN+Sh/Ur z = 0.05, EVN+VLBA z = 0.06

  3. Other Molecules • H2CO = 4.8 GHz transition • Weak lines found in three sources (few mJy with SD) • Arp220 = mapped with VLA-A & weakly with MERLIN • Pumping relation with NIR – limited diagnostics • Methanol = 6.67 GHz and 12.2 GHz • Great potential for tracing YSO and SF region • No (yet) MM detections & no (yet) Galactic-like emission • CH = 3.3 GHz • Not detected yet • CO(1-0) = below 25 GHz • Redshifts 3.6 and higher • NH3 = 23 GHz • Galactic masers or also amplification

  4. Future studies • Increase BW does not benefit Line Observations • More larger telescopes improves UV-coverage & imaging & sensitivity 1. Blind surveys = NO 2a. Simultaneous 4 OH lines and HI to disentangle redshifts & multi-epoch for pumping at 1-2 pc scale 2b. Trace the ULIRG population with L(24μm) > 1012 Lsol peaking at z ~2 and tracing galaxy merger rate 3. Zeeman & polarimetry: H2O B-field close to AGN and OH tracing nuclear magnetic field 4. Continue study of higher z H2O sources with few compact disk sources (complement SD of torus) 5. Other molecular lines

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