Analysis of the ¹³CO/C¹⁸O abundance ratio in young stellar objects and HII regions

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

Malargüe

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

Determining isotopes abundance ratios is important to study the physics and chemistry of the interstellar medium. It is known that the ¹³CO/C¹⁸O abundance ratio, indirectly determined from elemental abundance ratios, depends on the distance to the Galactic center. In this context it is important to determine whether this ratio may also depend on the type of source and its environment. A sample of 198 sources composed of young stellar objects, HII and diffuse HII regions from the the Red MSX Sourse Survey were analysed. To obtain the ¹³CO/C¹⁸O abundance ratio for each source it was used ¹²CO data extracted from the CO High-Resolution Survey (COHRS), and ¹³CO and C¹⁸O data from the ¹³CO/C¹⁸O (J=3?2) Heterodyne Inner Milky Way Plane Survey (CHIMPS). Some additional data from the James Clerk Maxwell Telescope were also used.We found that the average abundance ratio between ¹³CO and C¹⁸O for young stellar objects is smaller than for HII and diffuse HII regions. A linear relation between the abundance ratios and the line flux ratios was also found.