A multiwavelength study of the star forming region IRAS 18544+0112

Abstract

Aims. This work aims at investigating the molecular and infrared components in the massive young stellar object (MYSO) candidate IRAS 18544+0112. The purpose is to determine the nature and the origin of this infrared source. Methods. To analyze the molecular gas towards IRAS 18544+0112, we have carried out observations in a 9000 × 9000 region around l = 34. 69, b = –0. 65, using the Atacama Submillimeter Telescope Experiment (ASTE) in the 12CO J=3–2, 13CO J=3– 2, HCO+J=4–3 and CS J=7–6 lines with an angular resolution of 2200. The infrared emission in the area has been analyzed using 2MASS and Spitzer public data. Results. From the molecular analysis, we find self-absorbed 12CO J=3–2 profiles, which are typical in star forming regions, but we do not find any evidence of outflow activ- ity. Moreover, we do not detect either HCO+J=4–3 or CS J=7–6 in the region, which are species normally enhanced in molecular outflows and high density envelopes. The 12CO J=3–2 emission profile suggests the presence of expanding gas in the region. The Spitzer images reveal that the infrared source has a conspicuous extended emission bright at 8 μm with an evident shell-like morphology of 1.05 in size ( 1.4 pc at the proposed distance of 3 kpc) that encircles the 24 μm emission. The non-detection of ionized gas related to IRAS 18544+0112 together with the fact that it is still embedded in a molecular clump suggest that IRAS 18544+0112 has not reached the UCHII re- gion stage yet. Based on near infrared photometry we search for YSO candidates in the region and propos that 2MASS 18565878+0116233 is the infrared point source associ- ated with IRAS 18544+0112. Finally, we suggest that the expansion of a larger nearby HII region, G034.8−0.7, might be related to the formation of IRAS 18544+0112.