Young stellar objects in the large magellanic cloud: N63 and N180 H II regions

We used Spitzer infrared observations to find the young stars of two H n 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 R_d of ∼55 AU, and an envelope of moderate accretion rate, Ṁ_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_⊙, R_d of ∼200 AU, and 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.