Speaker: Tamal Mukherjee (Macquarie University)

Title: Mysteries in the Peaks: What double-peaked Lyα emission reveals about galaxy-CGM interactions

Abstract: Understanding how galaxies acquire and redistribute baryons remains one of the key open questions in galaxy evolution. Due to its resonant nature, Lyman-α (Lyα) emission is highly sensitive to the distribution and kinematics of neutral gas, making it a powerful tracer of the gaseous environments surrounding galaxies. In this talk, I will present recent results from VLT/MUSE observations of Lyα emitters at z~3–6, focusing on what the diverse Lyα spectral profiles can tell us about gas flows on circumgalactic scales. In particular, the properties of double-peaked Lyα emission, including peak separation, trough flux, peak asymmetry, reveal systematic variations in neutral hydrogen column density and gas kinematics with halo radius. Several systems also appear to be promising candidates for ionising photon escape, linking Lyα spectral properties to feedback and radiation leakage.
A small fraction of Lyα emitters show blue-peak dominant profiles, a rare spectral feature commonly interpreted as a signature of gas inflow. Deep JWST imaging and spectroscopy reveal that many of these blue-dominant systems are associated with compact, ultra-low-mass galaxies embedded within extended Lyα-emitting structures. Their young stellar populations and elevated ionisation conditions suggest recent star formation likely triggered by the accretion of fresh, low-metallicity gas. Together, these results highlight how Lyα spectral complexity can provide a direct observational window into the interaction between galaxies and the CGM in the early Universe.

• Date:
  June 23, 2026, 11 a.m. – noon
  
  
• Location:

  AIP; Kirch building, Conference room

  
  
• Contact:
  John Pharo
  jpharo@aip.de