The mid-infrared properties of three star-forming sites in NGC 6334

Citation
Ke. Kraemer et al., The mid-infrared properties of three star-forming sites in NGC 6334, ASTROPHYS J, 516(2), 1999, pp. 817-833
Citations number
63
Categorie Soggetti
Space Sciences
Journal title
ASTROPHYSICAL JOURNAL
ISSN journal
0004637X → ACNP
Volume
516
Issue
2
Year of publication
1999
Part
1
Pages
817 - 833
Database
ISI
SICI code
0004-637X(19990510)516:2<817:TMPOTS>2.0.ZU;2-S
Abstract
To investigate their dust properties, we have imaged three sites of massive star formation in the giant H II region/star-forming cloud NGC 6334 with t he MIRAC2 instrument. We obtained high-resolution (1 ") continuum images at 12.5 and 20.6 mu m toward each region, which were compared with observatio ns of the radio and near-infrared (near-IR) continuum emission. Both compac t sources and extended emission were found at all three star-forming sites. The detected sources span a wide range of evolutionary states in this high ly complex star-forming cloud. The infrared sources near NGC 6334 I were re solved into at least four subsources. One such source is substantially cold er, denser, and more optically thick than the other mid-IR sources in the r egion and may be at the earliest stages of stellar formation. Another may b e a torus or disk of dust and gas surrounding an embedded B star. NGC 6334 I was also imaged at additional wavelengths (8.8, 9.8, and 11.7 mu m) to se arch for silicate absorption. Only at the H II region is there a deep silic ate absorption feature from foreground dust. Toward the NGC 6334 IV, warm d ust is associated with both the inner portions of the massive molecular tor us or disk and with the bipolar continuum lobes. A compact mid-IR source, a ssociated with the near-IR and radio source [HHS87] IRS 20, is cooler and m ore optically thick than the dust emission associated with the H II region. Toward NGC 6334 V, four embedded sources were found, including one previou sly unidentified object. This newly identified compact object, associated w ith a dust temperature peak and a radio source, is probably in a more advan ced stage of star formation than the other compact mid-IR sources in NCC 63 34.