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

TL;DR

This study investigates the molecular and infrared characteristics of IRAS 18544+0112, revealing a shell-like morphology, expanding gas, and its likely formation triggered by a nearby HII region, without evidence of outflows or ionized gas.

Contribution

It provides a detailed multiwavelength analysis of IRAS 18544+0112, highlighting its morphology, molecular environment, and potential formation mechanism, which are novel insights for this object.

Findings

Infrared source has a shell-like structure at 8 um.

No evidence of outflows or ionized gas detected.

Expansion of nearby HII region may have triggered formation.

Abstract

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. To analyze the molecular gas towards IRAS 18544+0112, we have carried out observations in a 90" x 90" 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 22". The infrared emission in the area has been analyzed using 2MASS and Spitzer public data. 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 um with an evident shell-like morphology of ~ 1.5 arcmin in size (~ 1.4 pc at the proposed distance of 3 kpc) that encircles the 24 um 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 propos 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.