2008AJ....135.1697G

We present results from matching a Very Large Array Galactic plane catalog at 6 cm covering the first Galactic quadrant (350° ≤ l ≤ 42°,|b| ≤ 0.4°), the MSX6C Galactic plane catalog, and the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire v1.0 (GLIMPSE I) catalog. The much higher angular resolution and better sensitivity provided by GLIMPSE should improve the identification of embedded Galactic star-forming regions, and enable the study of the relationships between the central stellar sources, the ionized gas, and the surrounding dust. The GLIMPSE catalog is so crowded compared to our 6 cm catalog that it actually leads to confusion in identifying chance alignments, but this is resolved when separating GLIMPSE into red (M_3.6µm- M_8µm> 2.5) and blue (M_3.6µm- M_8µm<2.5) sub-catalogs. In spite of the improved properties of GLIMPSE, we find a very small number of GLIMPSE-6cm high-reliability matches in the overlapping area of the two samples (10°≤l≤42°, |b|≤0.4°)-132, only 55 of them have a Midcourse Space Experiment (MSX) counterpart. Even though the matching results are less successful than expected, there are still some general outcomes to them. First, we discover an obscuration effect around our candidates: the average local source density of blue sources, dominated by stars, is decreasing toward the radio positions; their average brightness increases, and their color reddens significantly, supporting the picture in which background sources disappear behind the opaque nebulae associated with the radio source. Second, the selected sources define near and mid-infrared color criteria, which are used to detect a total of 849 GLIMPSE sources in the entire GLIMPSE survey that have MSX matches and that show the same collective behavior. Only 15% of these sources are previously classified, mainly as H II regions, masers, young stellar objects, and molecular clouds.