[tel-00726959, v1] Caractériser le milieu interstellaire ... - HAL - INRIA

570 J. R. Goicoechea et al.: Low sulfur depletion in the Horsehead PDRtel-00726959, version 1 - 31 Aug 2012Fig. 3. Spectra along the direction of the exciting star at δy = 0 ′′ . 12 CO J = 1–0, C 18 O J = 2–1 and 12 CS J = 2–1 spectra cubes were smoothed bya15 ′′ -FWHM 1D-Gaussian along the y direction perpendicular to the illuminating star direction. Due to their small field of view (in particular inthe y direction), the 12 CO J = 2–1 data were just smoothed by a 5 ′′ -FWHM circular Gaussian.Fig. 4. IRAM-30 m CS J = 2–1, 3–2 and 5–4, and C 34 S J = 2–1 and 3–2 single-dish observations (histograms) at different positions of theHorsehead PDR single-dish C 18 O J = 2–1 emission centered at α 2000 = 05 h 40 m 58 s , δ 2000 = −02 ◦ 27 ′ 20 ′′ (from Hily-Blant et al. 2005).following temperature dependent collisional rate coefficients 2have been adopted:– for CS: we have used the latest CS + He collisional ratesfrom Lique et al. (2006), kindly provided by F. Lique2 Some of them retrieved from BASECOL, a data base for collisionalexcitation data at http://www.amdpo.obspm.fr/basecol. We consideredH 2 , He and H as the collisional partners in all CS, C 34 S, HCS +and C 18 O excitation models. See Appendix.prior to publication, scaled by the reduced mass factor(µ CS−H2 /µ CS−He ) 1/2 . Most of the models were repeated withthe older collisional rates of Turner et al. (1992).– for C 34 S: same as CS but using C 34 S spectroscopy to computecollisional excitation rates through detailed balance.– for C 18 O: CO + H 2 de-excitation rates from Flower (2001)but using C 18 O spectroscopy to compute collisional excitationrates through detailed balance.