BLUEPRINT: Blue-dominant Lyman-α emission as evidence of gas inflow in ultra-low-mass galaxies at z = 3
Abstract
We report the detection of a clumpy, blue-dominated Lyα 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 Lyα profiles, spectral signatures that are rarely observed. Radiative transfer simulations of the Lyα profile using a clumpy multiphase model suggest a radial inflow of gas clumps with a velocity of 100 km/s. Embedded in this Lyα structure, we find that the associated main galaxy dominates the stellar mass budget, while the two compact ultra-low-mass systems ((M/M) = 6.3-6.9) 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 compelling observational evidence that how gas accretion, most likely from the cosmic web, can induce starburst in ultra-low-mass galaxies.
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