THE BOLOCAM GALACTIC PLANE SURVEY: λ = 1.1 AND 0.35 mm DUST CONTINUUM EMISSION IN THE GALACTIC CENTER REGION

摘要

The Bolocam Galactic Plane Survey (BGPS) data for a 6?deg2 region of the Galactic plane containing the Galactic center are analyzed and compared to infrared and radio continuum data. The BGPS 1.1?mm emission consists of clumps interconnected by a network of fainter filaments surrounding cavities, a few of which are filled with diffuse near-IR emission indicating the presence of warm dust or with radio continuum characteristic of H II regions or supernova remnants. New 350 μm images of the environments of the two brightest regions, Sgr A and B, are presented. Sgr B2 is the brightest millimeter-emitting clump in the Central Molecular Zone (CMZ) and may be forming the closest analog to a super star cluster in the Galaxy. The CMZ contains the highest concentration of millimeter- and submillimeter-emitting dense clumps in the Galaxy. Most 1.1?mm features at positive longitudes are seen in silhouette against the 3.6-24 μm background observed by the Spitzer Space Telescope. However, only a few clumps at negative longitudes are seen in absorption, confirming the hypothesis that positive longitude clumps in the CMZ tend to be on the near side of the Galactic center, consistent with the suspected orientation of the central bar in our Galaxy. Some 1.1?mm cloud surfaces are seen in emission at 8 μm, presumably due to polycyclic aromatic hydrocarbons. A ~02 (~30?pc) diameter cavity and infrared bubble between l≈ 00 and 02 surround the Arches and Quintuplet clusters and Sgr A. The bubble contains several clumpy dust filaments that point toward Sgr A*; its potential role in their formation is explored. Bania's Clump 2, a feature near l = 3°-35 which exhibits extremely broad molecular emission lines (ΔV 150?km?s–1), contains dozens of 1.1?mm clumps. These clumps are deficient in near- and mid-infrared emission in the Spitzer images when compared to both the inner Galactic plane and the CMZ. Thus, Bania's Clump 2 is either inefficient in forming stars or is in a pre-stellar phase of clump evolution. The Bolocat catalog of 1.1?mm clumps contains 1428 entries in the Galactic center between l = 3585 and l = 45 of which about 80% are likely to be within about 500?pc of the center. The mass spectrum above about 80 M ☉ can be described by a power-law ΔN/ΔM = N 0 M –2.14(+0.1,–0.4). The power-law index is somewhat sensitive to systematic grain temperature variations, may be highly biased by source confusion, and is very sensitive to the spatial filtering inherent in the data acquisition and reduction.