Molecular gas and star formation towards the IR dust bubble S24 and its environs

CAPPA, C. E.; DURONEA, N. U.; FIRPO, V.; VASQUEZ, J.

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Lugar: Paris; Año: 2016 vol. 585 p. 30 - 47

0004-6361

Este trabajo fue consignado en intranet al año 2015 yaque la aceptacion del mismo fue en septiembre de 2015 y las correcciones de edición fueron enviadas a medidados de octubre del mismo año pero por retrasos en la editorial de A&A fue publicado en 2016.ABSTRACT:Aims. We present a multi-wavelength analysis of the infrared dust bubble S 24, and the extended IR sources G341.220-0.213 andG341.217-0.237 located in its environs, with the aim of investigating the characteristics of the molecular gas and the interstellar dustlinked to them, and analyzing the evolutionary state of the young stellar objects identified there and its relation to S 24 and the IRsources.Methods. Using the APEX telescope, we mapped the molecular emission in the CO(2-1), 13 CO(2-1), C18 O(2-1), and 13 CO(3-2) linesin a region of about 5′ × 5′ in size around the bubble. The cold dust distribution was analyzed using submillimeter continuum imagesfrom ATLASGAL and Herschel. Complementary IR and radio data at different wavelengths were used to complete the study of theinterstellar medium in the region.Results. The molecular gas distribution shows that gas linked to the S 24 bubble, G341.220-0.213, and G341.217-0.237 has velocitiesbetween ?48.0 km s−1 and ?40.0 km s−1 , compatible with a kinematical distance of 3.7 kpc generally adopted for the region. The gasdistribution reveals a shell-like molecular structure of ∼0.8 pc in radius bordering the S 24 bubble. A cold dust counterpart of the shellis detected in the LABOCA and Herschel-SPIRE images. The presence of weak extended emission at 24 μm from warm dust andradio continuum emission projected inside the bubble indicates the existence of exciting sources and that the bubble is a compact Hiiregion. Part of the molecular gas bordering the S 24 Hii region coincides with the extended infrared dust cloud SDC341.194-0.221.A molecular and cold dust clump is present at the interface between the S 24 Hii region and G341.217-0.237, shaping the easternborder of the IR bubble. As regards G341.220-0.213, the presence of an arc-like molecular structure encircling the northern andeastern sections of this IR source indicates that G341.220-0.213 is interacting with the molecular gas. The analysis of the availableIR point source catalogs reveals the existence of young stellar object (YSO) candidates linked to the IR extended sources, thusconfirming their nature as active star-forming regions. Gas and dust masses were estimated for the different features. Thetotal gas mass in the region and the H2 ambient density amount to 10300 M⊙ and 5900 cm−3 , indicating that G341.220-0.213,G341.217-0.237, and the S 24 Hii region are evolving in a high density medium. A triggering star formation scenario for theHii region is investigated.