Most stars in today’s Universe reside within spheroids, which are bulges of spiral galaxies and elliptical galaxies^1,2. Their formation is still an unsolved problem^3,4,5. Infrared/submillimetre-bright galaxies at high redshifts⁶ have long been suspected to be related to spheroid formation^{7,8,9,10,11,12}. Proving this connection has been hampered so far by heavy dust obscuration when focusing on their stellar emission^13,14,15 or by methodologies and limited signal-to-noise ratios when looking at submillimetre wavelengths^16,17. Here we show that spheroids are directly generated by star formation within the cores of highly luminous starburst galaxies in the distant Universe. This follows from the ALMA submillimetre surface brightness profiles, which deviate substantially from those of exponential disks, and from the skewed-high axis-ratio distribution. Most of these galaxies are fully triaxial rather than flat disks: the ratio of the shortest to the longest of their three axes is half, on average, and increases with spatial compactness. These observations, supported by simulations, reveal a cosmologically relevant pathway for in situ spheroid formation through starbursts that is probably preferentially triggered by interactions (and mergers) acting on galaxies fed by non-coplanar gas accretion streams.

当今宇宙中的大多数恒星都位于球体中，球体是螺旋星系和椭圆星系的凸起^1,2。它们的形成仍然是一个未解决的问题^3,4,5。长期以来，人们一直怀疑高红移⁶ 的红外/亚毫米亮星系与椭球体的形成有关^{7,8,9,10,11,12}。到目前为止，证明这种联系受到关注其恒星发射时的严重尘埃遮挡^13,14,15 或观察亚毫米波长时的方法和有限的信噪比^16,17 的阻碍。在这里，我们展示了椭球体是由遥远宇宙中高亮度星暴星系核心内的恒星形成直接产生的。这来自 ALMA 亚毫米表面亮度分布，它与指数盘的亮度分布有很大偏差，并且来自偏斜的高轴比分布。这些星系中的大多数是完全三轴的，而不是平坦的盘：它们的三个轴中最短的星系与最长星系的比值平均是一半，并且随着空间紧凑度的增加而增加。这些观测结果得到了模拟的支持，揭示了通过星暴形成的宇宙学相关途径，该途径可能优先由作用在非共面气体吸积流供给的星系上的相互作用（和合并）触发。