Spitzer Observations of the HII Region NGC 2467: An Analysis of Triggered Star Formation

Abstract

We present new Spitzer Space Telescope observations of the region NGC 2467, and use these observations to determine how the environment of an HII region affects the process of star formation. Our observations comprise IRAC (3.6, 4.5, 5.8, and 8.0 um) and MIPS (24 um) maps of the region, covering approximately 400 square arcminutes. The images show a region of ionized gas pushing out into the surrounding molecular cloud, powered by an O6V star and two clusters of massive stars in the region. We have identified as candidate Young Stellar Objects (YSOs) 45 sources in NGC 2467 with infrared excesses in at least two mid-infrared colors. We have constructed color-color diagrams of these sources and have quantified their spatial distribution within the region. We find that the YSOs are not randomly distributed in NGC 2467; rather, over 75% of the sources are distributed at the edge of the HII region, along ionization fronts driven by the nearby massive stars. The high fraction of YSOs in NGC 2467 that are found in proximity to gas that has been compressed by ionization fronts supports the hypothesis that a significant fraction of the star formation in NGC 2467 is triggered by the massive stars and the expansion of the HII region. At the current rate of star formation, we estimate at least 25-50% of the total population of YSOs formed by this process.