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Investigating Star Formation Feedback through Gas Kinematics in Nearby Galaxies

Presentation #232.04D in the session “ Star Formation in Galaxies”.

Published onJan 11, 2021
Investigating Star Formation Feedback through Gas Kinematics in Nearby Galaxies

The cycle of star formation affects nearly every aspect of a galaxy. Many phases in the stellar life cycle impart energy and momentum into the surrounding environment. As feedback processes inject energy and momentum into the environment, they necessarily affect the kinematics of the surrounding media. Probing the multiphase gas kinematics through observations of spectral lines is a key method to measure the physics of feedback. My thesis investigates stellar feedback in two regimes: on kiloparsec scales in moderately star-forming galaxies and at sub-parsec scales in a starburst environment. In this talk, I will focus on the latter case. Young massive clusters play an important role in the evolution of their host galaxies. A significant fraction of stars in starbursts are believed to form in a massive cluster environment, and feedback from the high-mass stars in these clusters can have profound effects on the surrounding interstellar medium. Characterizing the immediate environment of these clusters is difficult because resolving these compact (r~1 pc) structures in external galaxies requires very high spatial and spectral resolution observations. The nuclear starburst in the nearby galaxy NGC253 is a key laboratory in which to study star formation in an extreme environment and, at a distance of 3.5 Mpc, is one of the nearest starburst galaxies. Previous high resolution (1.9 pc) dust continuum observations from ALMA discovered 14 compact, massive super star clusters (SSCs). Using ALMA data at 350 GHz with 28 milliarcsecond (0.5 pc) resolution, we present direct evidence for outflows three of these SSCs in the nuclear starburst of NGC253. We detect blue-shifted absorption and red-shifted emission (P-Cygni profiles) towards three of these SSCs in multiple lines, including CS(7-6) and H13CN(4-3). The mass contained in these outflows is a non-negligible fraction of the cluster gas masses. We model the P-Cygni line profiles to constrain the outflow opening angles and inclinations, finding that the outflows must be nearly spherical. Through a comparison of the outflow properties with predictions from simulations and semi-analytic models, these outflows are likely powered by a combination of dust-reprocessed radiation pressure and O star winds. We suggest that the three clusters with outflows are among the most evolved in the burst and that the outflows are a result of the gas clearing towards the end of the cluster formation stage. At the current mass outflow rate, these outflows will have a substantial effect on the clusters’ evolution and star formation efficiency.

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