Molecular clumps towards compact H II regions

SALDAÑO, HUGO P; RUBIO, M; CAPPA, C E; GÓMEZ, M

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2019 vol. 487 p. 2881 - 2899

0035-8711

To better understand how the H II regions can affect their surrounding molecular clouds we have studied the molecular distribution towards three compact H II regions associated with IRAS sources (08140−3559, 09014−4736, and 09026−4842) by means of the observations of 12CO, 13CO, and C18O molecules in the J = 3−2 transition with the APEX telescope. In two cases, we show evidence of possible disruption of the molecular clouds and increasing turbulence towards the diffuse Halpha emissions, which could be due to the ionizing front. We find 11 clumps towards the IRAS sources either nearby or surrounding the H II regions. Their parameters, such as the optical depths, column densities, masses, and [13CO/C18O] abundances, were calculated assuming LTE conditions. We discuss the behaviour of such parameters and we have found that the [13CO/C18O] abundances in the IRAS sources associated with a diffuse Halpha emission are higher than the abundances in regions where no Halpha emission is detected, indicating that such a parameter could be affected by the UV field coming from H ii region. We also discuss the rise of the average [H2/13CO] and [H2/C18O] abundances in the IRAS sources which show evidence of disruption of molecular clouds by the expansion of the H II regions. With these average abundances, we estimate the LTE total mass of each clump and compare them with the virial mass to discuss whether our clumps are gravitationally stable.