The ALMA REBELS Survey: Discovery of a massive, highly star-forming and morphologically complex ULIRG at $z =7.31$

Understand

We present Atacama Large Millimeter/Submillimeter Array (ALMA) [CII] and $\sim158$ $\rm\mu m$ continuum observations of REBELS-25, a massive, morphologically complex ultra-luminous infrared galaxy (ULIRG; $L_{\rm IR}=1.5^{+0.8}_{-0.5}\times10^{12}$ L$_\odot$) at $z=7.31$, spectroscopically confirmed by the Reionization Era Bright Emission Line Survey (REBELS) ALMA Large Programme.

• REBELS-25 has a significant stellar mass of $M_{*}=8^{+4}_{-2}\times10^{9}$ M$_\odot$.
• From dust-continuum and ultraviolet observations, we determine a total obscured + unobscured star formation rate of SFR $=199^{+101}_{-63}$ M$_\odot$ yr$^{-1}$.
• This is about four times the SFR estimated from an extrapolated main-sequence.