The intermediate-mass embedded cluster GM-24 revisited: New infrared and radio observations

TAPIA, M., RODRÍGUEZ, L. F., PERSI, P., ROTH M., GÓMEZ, M.

ASTRONOMICAL JOURNAL

IOP PUBLISHING LTD

Lugar: Londres; Año: 2009 p. 4127 - 4139

0004-6256

New and archived high-resolution infrared (IR; 1-20 μm) and radio-continuum images of the isolated embedded cluster and associated compact H II region, GM 24, are presented and measured photometrically. The nucleus of the complex is Irs 3, or IRAS 17136-3617, located at the densest part of the molecular cloud. This object is composed of at least three compact near-IR sources (A, B, and C) that are the most luminous and massive young stellar components and provide most of the ionizing energy to the cometary-shaped radio H II region. The 3.6 cm radio map shows a complex structure with an extended emission peak and two very compact components very close to Irs 3A. Large inhomogeneities in the dust density within the nebula cause considerably different morphologies in the observed emission of hydrogen recombination lines, namely Pa_beta, Brγ, and Br_alpha. No H2 line emission at 2.12 μm was detected. The embedded IR cluster is found to contain more than 100 members within a radius of around 40 arcsec, which corresponds to 0.39 pc. The total stellar mass is estimated to be greater or similar to 250 M sun. The extinction to the nearby edge of the cluster is determined to be AV = 13, though a number of sources, including Irs 3, are reddened by AV > 50. A fraction of near-IR sources, mainly in the periphery of the cluster, are main-sequence A-B-type stars, while a large fraction (~50%) of the detected members show significant IR excesses, including several Class I young stellar objects with luminosities ranging from a few solar luminosities near our sensitivity limit, to 1.5 × 105 L sun, the derived luminosity of Irs 3.