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

H. S. Liszt and J. Pety: Imaging diffuse clouds: bright and dark gas mapped in CO0.5 0.61.60.8 0.9 0.774˚30'10Bδ (J2000)74˚00'B0212+73573˚30' 1 0.9 0.8 0.71.40.6T r* (Kelvin)0 A*10tel-00726959, version 1 - 31 Aug 2012δ(J2000)δ(J2000)73˚00'74˚00'73˚50'73˚40'δ1.2B2h20mα (J2000)A0.42h10m02h20m 2h18m 2h16m 2h14mα(J2000)Right Ascension(J2000)7e -τ -1-10 0212+735H2 2 CO*7.8CO1OH*7.30HCO-1+H I-2-20 -10 0 10V LSR (KM S -1 )Fig. 10. The sky field around the position of B0212+735, as in Fig. 2. Contours in the CO emission map at lower left are color coded in blue foremission at −15 ≤ v ≤−9.5kms −1 and in green for emission at −2 ≤ v ≤ 1kms −1 . The gray scale background represents the integrated emissionof the strongest emission component seen toward the continuum source, at v = 1.5−5 kms −1 . 12 CO spectra at two locations labeled A and B areshown at upper right along with a strongly-scaled mean profile taken over the full map area.absorption there are two distinct kinematic components at −11and −8kms −1 that would usually be interpreted as unrelated because,aside from their separation in velocity, they have differentpatterns of chemical abundances (Fig. 12). However, Fig. 14shows that the CO emission line has an appreciable velocity gradientacross the position of the continuum source, spanning thetwo absorption lines, making it likely that the two absorptioncomponents are part of the same body 1 . Moreover, the CO mappingsuggests that the components at −17 and −10 km s −1 mayalso be part of the same structure (and separated by a velocitygradient), which was actually suggested by several coincidencesin our earlier high-resolution CO mapping (Pety et al.2008). The lines at −11 and −17 km s −1 are very bright (13 K)at high resolution and have considerable chemical complexity.There are also some seemingly correlated spatial intensity variations.The evidence for an association is entirely indirect but has1 Pety et al. (2008) show that the overlapping CO emission line is resolvedinto two kinematic components at 6 ′′ resolution toward the continuumsource.a clear precedent in the kinematics around B0528+134 (Sect. 4.1and Fig. 8) where a similar velocity separation occurs betweentwo emission components that are seen superposed in an unusualwave-like spatial configuration.8. The brightness of diffuse cloud CO8.1. W CO relative to E B−V and f H2The large-scale finding chart in Fig. 1 is a map of the total interveninggas column density, except where discrete sources ofinfrared emission (often H II regions) “leak” into the map (usefullyindicating when the background target may have been observedthrough disturbed foreground gas). Large-scale surveysof CO emission at 8 ′ resolution show a good correlation withreddening (Dame et al. 2001), contributing to the common interpretationof CO sky maps as displaying the global distributionof dense, fully-molecular gas.In diffuse gas appreciable scatter in the W CO − E B−V relationshipis expected because the reddening is a sum overA58, page 13 of 23