Artículo de revista
Dust-gas scaling relations and oh abundance in the galactic ISM
Astrophysical Journal, 81(1), 20 Julio 2018, art 49.
Bronfman Aguiló, Leonardo
Finger Camus, Ricardo
Observations of interstellar dust are often used as a proxy for total gas column density N-H. By comparing Planck thermal dust data (Release 1.2) and new dust reddening maps from Pan-STARRS 1 and 2MASS, with accurate (opacity-corrected) H I column densities and newly published OH data from the Arecibo Millennium survey and 21-SPONGE, we confirm linear correlations between dust optical depth tau(353), reddening E(B - V), and the total proton column density N-H in the range (1-30) x 10(20) cm(-2), along sightlines with no molecular gas detections in emission. We derive an N-H/E(B - V) ratio of (9.4 +/- 1.6) x 10(21) cm(-2) mag(-1) for purely atomic sightlines at |b| > 5 degrees, which is 60% higher than the canonical value of Bohlin et al. We report a similar to 40% increase in opacity sigma(353) = tau(353)/N-H, when moving from the low column density (N-H < 5 x 10(20) cm(-2)) to the moderate column density (N-H > 5 x 10(20) cm(-2)) regime, and suggest that this rise is due to the evolution of dust grains in the atomic interstellar medium. Failure to account for H I opacity can cause an additional apparent rise in sigma(353) of the order of a further similar to 20%. We estimate molecular hydrogen column densities N-H2 from our derived linear relations, and hence derive the OH/H-2. abundance ratio of X-OH similar to 1 x 10(-7) for all molecular sightlines. Our results show no evidence of systematic trends in OH abundance with N-H2 in the range N-H2 similar to (0.1-10) x 10(21) cm(-2). This suggests that OH may be used as a reliable proxy for H-2. in this range, which includes sightlines with both CO-dark and CO-bright gas.