A fast starburst wind consumes most of the energy from supernovae.
basic_science · Level V
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- Record sourced from PubMed, PMID 41882131.
- Also identified by DOI 10.1038/s41586-026-10231-1.
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Abstract
Starburst galaxies often host multiphase, galaxy-scale winds thought to enrich the circumgalactic medium and limit further star formation by disrupting interstellar gas clouds<sup>1-3</sup>. These winds are primarily powered by supernovae<sup>4-6</sup>, but it remains unclear how supernova energy forms an organized flow. Here we use the Resolve spectrometer on the X-ray Imaging and Spectroscopy Mission to show that the hot (T = 2 × 10<sup>7</sup> K) gas in the nucleus of the starburst galaxy M82 is moving quickly, with a line-of-sight velocity dispersion <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>σ</mi> <mo>=</mo> <mn>59</mn> <msubsup><mn>5</mn> <mrow><mo>-</mo> <mn>128</mn></mrow> <mrow><mo>+</mo> <mn>464</mn></mrow> </msubsup> <mspace></mspace> <mi>km</mi> <mspace></mspace> <msup><mi>s</mi> <mrow><mo>-</mo> <mn>1</mn></mrow> </msup> </math> . This is consistent with a hot, nuclear wind generated by thermal pressure. We show that a free-wind model reproduces the measured temperature but underpredicts the velocity. The inferred mass and energy outflow rates from the nucleus, about 7 M<sub>⊙</sub> yr<sup>-1</sup> and 4 × 10<sup>42</sup> erg s<sup>-1</sup>, require that most supernova energy is thermalized. These outflow rates provide enough energy to power the ≳30 M<sub>⊙</sub> yr<sup>-1</sup> cool outflow and still transport up to 3 M<sub>⊙</sub> yr<sup>-1</sup> to the intergalactic medium, suggesting that thermal gas pressure is sufficient to power the multiphase wind without additional support from cosmic rays<sup>7</sup>. We also show that the nuclear gas is hotter and faster than the plasma seen on larger scales ( <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>k</mi> <mi>T</mi> <mspace></mspace> <mo>=</mo> <mspace></mspace> <msubsup><mn>0.72</mn> <mrow><mo>-</mo> <mn>0</mn> <mo>.</mo> <mn>08</mn></mrow> <mrow><mo>+</mo> <mn>0.10</mn></mrow> </msubsup> <mspace></mspace> <mi>keV</mi></math> , <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>σ</mi> <mo>=</mo> <mn>17</mn> <msubsup><mn>5</mn> <mrow><mo>-</mo> <mn>73</mn></mrow> <mrow><mo>+</mo> <mn>86</mn></mrow> </msubsup> <mspace></mspace> <mi>km</mi> <mspace></mspace> <msup><mi>s</mi> <mrow><mo>-</mo> <mn>1</mn></mrow> </msup> </math> ), suggesting a distinct origin for the latter.