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

M. E. Ortega¹, S. Paron¹, S. Cichowolski¹, M. Rubio², G. Castelletti¹ and G. Dubner¹

¹ Instituto de Astronomía y Física del Espacio (IAFE), CC 67, Suc. 28, 1428 Buenos Aires, Argentina e-mail: mortega@iafe.uba.ar
² Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile

Received: 18 June 2009
Accepted: 6 November 2009

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 90 90 region around l = 3469, b = -065, 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 22. 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 activity. 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 ~15 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 region stage yet. Based on near infrared photometry we search for YSO candidates in the region and propose that 2MASS 18565878+0116233 is the infrared point source associated 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.