Outflows from Super Star Clusters in the Central Starburst of NGC253

Abstract

Young massive clusters play an important role in the evolution of their host galaxies, and feedback from the high-mass stars in these clusters can have profound effects on the surrounding interstellar medium. The nuclear starburst in the nearby galaxy NGC 253 at a distance of 3.5 Mpc is a key laboratory in which to study star formation in an extreme environment. Previous high resolution (1.9 pc) dust continuum observations from ALMA discovered 14 compact, massive super star clusters (SSCs) still in formation. We present here ALMA data at 350 GHz with 28 milliarcsecond (0.5 pc) resolution. We detect blueshifted absorption and redshifted emission (P-Cygni profiles) towards three of these SSCs in multiple lines, including CS 7−6 and H 13 CN 4−3, which represents direct evidence for previously unobserved outflows. The mass contained in these outflows is a significant fraction of the cluster gas masses, which suggests we are witnessing a short but important phase. Further evidence of this is the finding of a molecular shell around the only SSC visible at near-IR wavelengths. We model the P-Cygni line profiles to constrain the outflow geometry, finding that the outflows must be nearly spherical. Through a comparison of the outflow properties with predictions from simulations, we find that none of the available mechanisms completely explains the observations, although dust-reprocessed radiation pressure and O star stellar winds are the most likely candidates. The observed outflows will have a very substantial effect on the clusters' evolution and star formation efficiency.

Embedded Young Massive Star Clusters in the Antennae Merger

“…We plot our measurements of the YMCs in the sizemass relation along with literature data from other galaxies (Fig 5). According to Leroy et al (2018) and Levy et al (2020), very young YMCs are generally very compact with radii of 1 ∼ 2 pc. However, from the fit to the size-mass relation in the LEGUS sample (Brown & Gnedin 2021), we would expect a radius of ∼ 5 pc for a YMC with stellar mass of 10 6 M .…”

“…However, we note that the feedback region in the size-mass diagram is one projection of a complex process. In Levy et al (2020), they find outflows in YMCs which they do not expect to be experiencing feedback given their location in the size-mass diagram.…”

Efficiently Cooled Stellar Wind Bubbles in Turbulent Clouds I. Fractal Theory and Application to Star-Forming Clouds

“…When the input wind power is very low (e.g M * 10 3 M ) we show in Paper II that α p ∼ 1.5 − 4. This range could apply in moderate density GMCs, where the efficiencies of star cluster formation are only Levy et al 2020). For this range, the momentum enhancement above the direct wind input is modest, α p ∼ 1.2 − 2 (see Paper II).…”

“…Very recently, new empirical evidence of feedback in extreme environments was obtained by Levy et al (2020), who observed the environment of nascent super star clusters in NGC 253 with 0.5 pc resolution ALMA observations in multiple molecular lines. From analysis of P-Cygni profiles, indicative of cluster-scale outflows, Levy et al (2020) obtained estimates of the mass and momentum carried by outflows around three of the SSCs in NGC 253 and applied our theory of stellar wind feedback to test whether this could explain the observations. They found that given modest momentum enhancement factors, α p ∼ 1 − 4, winds could plausibly be the dominant feedback mechanism.…”

“…The importance of these mechanisms has been debated in the recent literature, with several observational studies attempting to assess the relative contributions. This includes observations of evolved clusters in the Large Magellanic Cloud (LMC) by Pellegrini et al (2011); Lopez et al (2011Lopez et al ( , 2014; McLeod et al (2019), in the Milky Way (Rosen et al 2014), in nearby 'normal' galaxies (McLeod et al 2020;Chevance et al 2020b), and in nearby galaxies with more extreme star-forming environments (Levy et al 2020). The recent works of Olivier et al (2020) and Barnes et al (2020) have sought to make the same evaluation but at very early times (in deeply embedded clusters) in the Milky Way.…”