Astronomers map violent outflows from massive star birth, revealing formation secrets
Researchers detected jets of ionized and atomic gas streaming from a forming massive star, providing the first direct evidence of how these cosmic engines regulate galaxies. The findings could improve models of star formation and help predict how massive stars seed the universe with heavy elements—crucial for understanding galaxy evolution and long-term cosmic chemistry.
Originaltitel: The SOMA Atomic Outflow Survey. I. An Atomic O <scp>I</scp> and Highly Ionized O <scp>III</scp> Outflow from Massive Protostar G11.94-00.62
Abstract Massive stars regulate galaxy evolution and star formation through their physical and chemical feedback, but their formation remains poorly understood. Accretion-powered outflows provide important diagnostics of massive star formation. We present first results from the SOMA Atomic Outflow Survey, a far-infrared massive star formation survey using the FIFI-LS instrument on SOFIA. We report the detection of [O iii ] 3 P 2 → 3 P 1 emission at 52 μ m from the massive protostar G11.94-0.62, tracing highly ionized gas. We also detect [O i ] 3 P 2 → 3 P 1 and 3 P 1 → 3 P 0 at 63 and 145 μ m tracing atomic gas, as well as CO J = 14 → 13 at 186 μ m from highly excited molecular gas. The [O iii ] and [O i ] lines exhibit large line widths (∼200 and ∼40–80 km s −1 , respectively) and their morphologies are consistent with a wide-angle bipolar outflow. The properties of molecular tracers ( 12 CO, 13 CO, C 18 O, H 2 CO, and CH 3 OH) observed with the Atacama Large Millimeter/submillimeter Array support this interpretation. Ionized nebula and photodissociation region modeling imply an ionized outflow mass flux of ∼8 × 10 −5 M ⊙ yr −1 and an atomic outflow mass flux of ∼5 × 10 −6 M ⊙ yr −1 , while the molecular outflow traced by CO has an implied mass flux of ∼3 × 10 −4 M ⊙ yr −1 . The mass and momentum flux in the ionized outflow are consistent with the primary disk wind, while the molecular component is mainly swept-up, secondary outflow gas. We also observe G11.94-0.62 with the Large Binocular Telescope in the near-infrared, potentially tracing the base of wide-angle outflow cavities. Spectral energy distribution modeling implies a protostellar mass <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>m</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>*</mml:mo> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>22</mml:mn> <mml:mo>.</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>11</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>21</mml:mn> </mml:mrow> </mml:msubsup> <mml:mspace width="0.25em"/> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> </mml:math> , while the [O iii ] emission implies m * ≳ 30 M ⊙ and that the protostar is in the final stages of its accretion.