Young Stellar Objects in the Large Magellanic Cloud: N63 and N180 HiiRegions

Abstract

We used Spitzer infrared observations to find the young stars of two H II regions in the Large Magellanic Cloud, N63 and N180. The young stellar object (YSO) candidates were identified in each nebula by means of color-color, color-magnitude diagrams, and the shapes of their spectral energy distributions (SEDs). The most luminous YSOs are found near the ionization fronts within strong 8 μm emission clumps. Most YSOs, less luminous, are seen in projection inside the H II regions. HST images show several Class I stars that have emerged along the borders of the H II regions; other YSOs are embedded in cometary clouds. The most luminous YSO of N63 is connected to a string of pointlike sources. Its SED can be modeled by a central source of stellar mass -->M between 7 and 11 -->M☉, with a circumstellar disk of outer radius -->Rd of ~55 AU, and an envelope of moderate accretion rate, $d{M}env$ --> of ~ -->2 × 10−5 -->M☉ yr−1. N180 is experiencing a phase of star formation more intense than N63, attested by the properties of its most luminous YSO: -->M of 25 -->M☉, -->Rd of ~200 AU, and $d{M}env$ --> of ~ -->1.5 × 10−3 -->M☉ yr−1. The modes of triggered star formation in N63 and N180 appear similar to those seen in Galactic H II regions.