Feedback from Massive Stars: SOFIA Observations of the Horsehead, W43, and the CMZ

Feedback from stars plays a fundamental role in regulating the rate of star formation and in shaping the interstellar medium. Although low mass stars are far more numerous, massive star feedback in the form of soft and ionizing UV, powerful stellar winds, and supernovae, dominate the energy and momentum injection budget of the Galaxy. In this talk I will review recent observations of three environments with progressively larger feedback impacts. The Horsehead Nebula located along the Western rim of the Orion B molecular cloud, was shaped by soft and ionizing UV from a few OB stars in the Orion OB Association. The "mini-starburst" in W43, one of the most luminous star forming complexes in the Galactic disk, may have been triggered by an older cluster with an ionizing luminosity more than 10 times larger than the Orion Nebula and ∼100 times that impacting the Horsehead region. SOFIA FORCAST provides the clearest view yet obtained of the half dozen clusters and massive stars forming in the heads of giant pillars facing the older cluster responsible for ionizing the W43 giant HII region. Much of the negative longitude portion of the Central Molecular Zone (CMZ) may have been blown out and converted into atomic and ionized gas by a nuclear starburst 5 to 30 Myrs ago. This region is inhabited by ∼103 compact 24 μm sources which may trace HII regions and post-main-sequence supergiants. upGREAT [CII] and [NII] observations may provide a test of this hypothesis.