Kavli Affiliate: Roberto Maiolino
| First 5 Authors: Callum Witten, Nicolas Laporte, Sergio Martin-Alvarez, Debora Sijacki, Yuxuan Yuan
| Summary:
During the epoch of reionisation the first galaxies were enshrouded in
pristine neutral gas, with one of the brightest emission lines in star-forming
galaxies, Lyman-$alpha$ (Ly$alpha$), expected to remain undetected until the
Universe became ionised. Providing an explanation for the surprising detection
of Ly$alpha$ in these early galaxies is a major challenge for extra-galactic
studies. Recent JWST observations have reignited the debate on whether
residence in an overdensity of galaxies is a it sufficient and necessary
condition for Ly$alpha$ to escape. Here, we take unique advantage of both
high-resolution and high-sensitivity images from the JWST instrument NIRCam to
reveal that all galaxies in a sample of z>7 Ly$alpha$ emitters have close
companions. We exploit novel on-the-fly radiative transfer
magnetohydrodynamical simulations with cosmic ray feedback to show that
galaxies with frequent mergers have very bursty star formation which drives
episodes of high intrinsic Ly$alpha$ emission and facilitates the escape of
Ly$alpha$ photons along channels cleared of neutral gas. We conclude that the
rapid build up of stellar mass through mergers presents a compelling solution
to the long-standing puzzle of the detection of Ly$alpha$ emission deep into
the epoch of reionisation.
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