%0 Generic %1 pineda2017characterizing %A Pineda, Jorge L. %A Langer, William D. %A Goldsmith, Paul F. %A Horiuchi, Shinji %A Kuiper, Thomas B. H. %A Muller, Erik %A Hughes, Annie %A Ott, Juergen %A Velusamy, Thangasamy %A Wong, Tony %D 2017 %K atomic diffuse gas lmc molecular smc %T Characterizing the transition from diffuse atomic to dense molecular clouds in the Magellanic clouds with CII, CI, and CO %U http://arxiv.org/abs/1704.00739 %X We present and analyze deep Herschel/HIFI observations of the CII 158um, CI 609um, and CI 370um lines towards 54 lines-of-sight (LOS) in the Large and Small Magellanic clouds. These observations are used to determine the physical conditions of the line--emitting gas, which we use to study the transition from atomic to molecular gas and from C^+ to C^0 to CO in their low metallicity environments. We trace gas with molecular fractions in the range 0.1<f(H2)<1, between those in the diffuse H2 gas detected by UV absorption (f(H2)<0.2) and well shielded regions in which hydrogen is essentially completely molecular. The C^0 and CO column densities are only measurable in regions with molecular fractions f(H2)>0.45 in both the LMC and SMC. Ionized carbon is the dominant gas-phase form of this element that is associated with molecular gas, with C^0 and CO representing a small fraction, implying that most (89% in the LMC and 77% in the SMC) of the molecular gas in our sample is CO-dark H2. The mean X_CO conversion factors in our LMC and SMC sample are larger than the value typically found in the Milky Way. When applying a correction based on the filling factor of the CO emission, we find that the values of X_CO in the LMC and SMC are closer to that in the Milky Way. The observed CII intensity in our sample represents about 1% of the total far-infrared intensity from the LOSs observed in both Magellanic Clouds.

@misc{pineda2017characterizing, abstract = {We present and analyze deep Herschel/HIFI observations of the [CII] 158um, [CI] 609um, and [CI] 370um lines towards 54 lines-of-sight (LOS) in the Large and Small Magellanic clouds. These observations are used to determine the physical conditions of the line--emitting gas, which we use to study the transition from atomic to molecular gas and from C^+ to C^0 to CO in their low metallicity environments. We trace gas with molecular fractions in the range 0.1<f(H2)<1, between those in the diffuse H2 gas detected by UV absorption (f(H2)<0.2) and well shielded regions in which hydrogen is essentially completely molecular. The C^0 and CO column densities are only measurable in regions with molecular fractions f(H2)>0.45 in both the LMC and SMC. Ionized carbon is the dominant gas-phase form of this element that is associated with molecular gas, with C^0 and CO representing a small fraction, implying that most (89% in the LMC and 77% in the SMC) of the molecular gas in our sample is CO-dark H2. The mean X_CO conversion factors in our LMC and SMC sample are larger than the value typically found in the Milky Way. When applying a correction based on the filling factor of the CO emission, we find that the values of X_CO in the LMC and SMC are closer to that in the Milky Way. The observed [CII] intensity in our sample represents about 1% of the total far-infrared intensity from the LOSs observed in both Magellanic Clouds.}, added-at = {2017-04-05T09:57:16.000+0200}, author = {Pineda, Jorge L. and Langer, William D. and Goldsmith, Paul F. and Horiuchi, Shinji and Kuiper, Thomas B. H. and Muller, Erik and Hughes, Annie and Ott, Juergen and Velusamy, Thangasamy and Wong, Tony}, biburl = {https://www.bibsonomy.org/bibtex/2842384460ff874774a135522f2475cd7/miki}, description = {[1704.00739] Characterizing the transition from diffuse atomic to dense molecular clouds in the Magellanic clouds with [CII], [CI], and CO}, interhash = {11ab2ca521babb06dbe65af5dd955adf}, intrahash = {842384460ff874774a135522f2475cd7}, keywords = {atomic diffuse gas lmc molecular smc}, note = {cite arxiv:1704.00739Comment: 32 pages, 21 figures, Accepted to ApJ}, timestamp = {2017-04-05T09:57:16.000+0200}, title = {Characterizing the transition from diffuse atomic to dense molecular clouds in the Magellanic clouds with [CII], [CI], and CO}, url = {http://arxiv.org/abs/1704.00739}, year = 2017 }