Analysis of the CO/CO abundance ratio in young stellar objects and HII regions

AREAL, M.B.; PARON, S.; CELIS PEÑA, M.; ORTEGA, M. E

Malargue, Mendoza

Congreso; 60 Reunión Anual de la Asociación Argentina de Astronomía; 2017

Determining isotopes abundance ratios is important to study the physicsand chemistry of the interstellar medium. It is known that the CO/COabundance ratio, indirectly determined from elemental abundance ratios,depends on the distance to the Galactic center. In this context it isimportant to determine whether this ratio may also depend on the type ofsource and its environment. A sample of 198 sources composed of youngstellar objects, H ii and diffuse Hii regions from the the Red MSXSource Survey were analysed. To obtain the CO/CO abundance ratio foreach source it was used CO data extracted from the CO High-ResolutionSurvey (COHRS), and CO and CO data from the CO/CO (J=3-2)Heterodyne Inner Milky Way Plane Survey (CHIMPS). Some additional datafrom the James Clerk Maxwell Telescope were also used. We found thatthe average abundance ratio between CO and CO for young stellar objectsis smaller than for HII and diffuse HII regions. A linear relationbetween the abundance ratios and the line flux ratios was also found.