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Lighting the dark molecular gas using the MIR H 2 rotational lines Aditya Togi Advisor: JD Smith University of Toledo 19 th June 2014 1

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GalaxyISM Curry Spices 2

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H 2 important for star formation Bigiel et al., 2008, AJ, 136, 2846 3

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H 2 not observed due to cold ISM No dipole moment Need high temperature to excite H 2 4

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Need indirect tracer to detect H 2 - CO, dust, SFR, -rays CO, gal = 4.35 M (pc 2 K km/s) -1 5 Solomon et al; 1987, ApJ, 319, 730

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Dark Molecular Gas not traced by CO Wolfire et al; 2010, ApJ, 716, 1191 6

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MIR-H 2 rotational lines by - IRS Spitzer 7 5m 38m S(0) to S(7)

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H 2 rotational lines in MIR spectral region Smith et al; 2007, ApJ, 656, 770 8

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= 85= 50=2000 9 Power law distribution of H 2

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Discrete temperature fit T 1 = 156K T 2 = 408K Roussel et al., 2007, ApJ, 669, 959 Model fit using continuous power law distribution 50 to 2000K with power law index 5.15 10

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Molecular gas traced by H 2 rotational lines 11

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Model predicts H 2 gas in low metallicity system 12

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Expectation from JWST - MIRI H 2 MIR lines S(1)/S(2) and higher till z = 0.65/1.30 At z = 0.5 (3 Gpc) detecting S(1) needs 70min for S/N = 10 ALMA Good check JWST(MIRI) - Good help 14

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Model benefits and cost to astronomers Continuous temperature distribution of molecules Recover total H 2 gas MIRI instrument of JWST Solve for CO factor problem Cost Assumes LTE approximation Need 3 rotational lines of H 2 A new method to calculate H 2 gas mass - useful in low metallicity systems and at high redshifts 15 Benefits

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Thank You Questions, Discussions, Suggestions 16