A wind-blown bubble in the Central Molecular Zone cloud G0.253+0.016

G0.253+0.016, commonly referred to as 'the Brick' and located within the Central Molecular Zone, is one of the densest (approximate to 10(3-4) cm(-3)) molecular clouds in the Galaxy to lack signatures of widespread star formation. We set out to constrain the origins of an arc-shaped molecular line emission feature located within the cloud. We determine that the arc, centred on {l(0), b(0)} = {0 degrees.248, 0 degrees.018}, has a radius of 1.3 pc and kinematics indicative of the presence of a shell expanding at 5. 2(-1.9)(+2.7) km s(-1). Extended radio continuum emission fills the arc cavity and recombination line emission peaks at a similar velocity to the arc, implying that the molecular gas and ionized gas are physically related. The inferred Lyman continuum photon rate is N-LyC = 10(46.0)-10(47.9) photons s(-1), consistent with a star of spectral type B1-O8.5, corresponding to a mass of approximate to 12-20 M-circle dot. We explore two scenarios for the origin of the arc: (i) a partial shell swept up by the wind of an interloper high-mass star and (ii) a partial shell swept up by stellar feedback resulting from in situ star formation. We favour the latter scenario, finding reasonable (factor of a few) agreement between its morphology, dynamics, and energetics and those predicted for an expanding bubble driven by the wind from a high-mass star. The immediate implication is that G0.253+0.016 may not be as quiescent as is commonly accepted. We speculate that the cloud may have produced a <= 10(3) M-circle dot star cluster greater than or similar to 0.4 Myr ago, and demonstrate that the high-extinction and stellar crowding observed towards G0.253+0.016 may help to obscure such a star cluster from detection.

Automated summary

In this study, a arc-shaped molecular line emission feature located within the G0.253+0.016 cloud in the Central Molecular Zone was investigated. The arc was found to have kinematics and radiative properties that are consistent with predictions for an expanding bubble driven by the wind from a high-mass star. This discovery suggests that G0.253+0.016 may not be as quiescent as previously thought and may harbor a star cluster formed approximately 0.4 million years ago.