BLUEPRINT: Blue-dominant Lyman-alpha (Ly$\alpha$) emission as an evidence of gas inflow in ultra-low-mass galaxies at z = 3

TL;DR

This study presents direct observational evidence of gas inflow from the cosmic web in ultra-low-mass galaxies at z=3, linking gas accretion to starburst activity through blue-dominated Lyα emission and radiative transfer modeling.

Contribution

It is the first to detect and interpret blue-dominated Lyα emission as evidence of gas inflow in ultra-low-mass galaxies at high redshift, supported by detailed radiative transfer simulations.

Findings

Blue-dominated Lyα emission indicates gas inflow.

Ultra-low-mass galaxies experienced recent bursty star formation.

Gas accretion from cosmic web likely triggers starbursts.

Abstract

We report the detection of a clumpy, blue-dominated Ly$\alpha$ emission at z = 3.066 located in the heart of a cosmic web filament in the MUSE eXtremely Deep Field (MXDF), spatially associated with the formation of two compact star-forming regions revealed by deep JWST/NIRCam imaging. Gas accretion in these regions is indicated by the blue-dominated Ly$\alpha$ profiles, spectral signatures that are rarely observed. Radiative transfer simulation of the Ly$\alpha$ profile using a clumpy multiphase model suggests a radial inflow of gas clumps with a velocity of 100 km/s. Embedded in this Ly$\alpha$ structure, we find that the associated main galaxy dominates the stellar mass budget, while the two compact ultra-low-mass systems ($\log(M_\star/M_\odot) = 6.3\text{-}6.9$) have formed the bulk of their stellar mass in less than 7 Myr. These two components also have high specific star-formation rates, and elevated ionisation parameters, consistent with recent bursty star formation. This system provides direct observational evidence that how gas accretion, most likely from cosmic web, can induce starburst in ultra-low-mass galaxies.