Siwei Zou, Robert A. Simcoe, Patrick Petitjean, Celine Peroux, Jaclyn B. Champagne

| Summary:

[[{“value”:”Cold and cool gas (T $leq 10^4$ K) in the circumgalactic medium (CGM) and
its interaction with galaxies remain poorly understood. Simulations predict
that cold gas flows into galaxies through cosmic filaments, determining the
disk formation and galaxy evolution. The cold gas accretion modes in the CGM
and their dependence on dark matter halo mass and redshift remain puzzling.
Resolving the kiloparsec-scale kinematics and dynamics of cold gas interacting
with the disk, dust, and metals in different environments is particularly
lacking at z > 2. Here we report two disturbed cold gas structures traced by
ultra-strong MgII absorbers (rest-frame equivalent width Wr > 2 AA) exhibiting
high kinematic velocities (> 500 km/s) and their environments at z ~ 4.9 and z
~ 2.6. Observations were conducted with VLT/MUSE, JWST/NIRCam, and ALMA to
detect Lya and nebular emission lines, as well as dust continuum emission in
the vicinity of these two absorbing gas structures. We identify two Lya
emitters associated with a strong MgII absorber pair separated by ~1000 km/s at
z~ 4.87. The pair exhibits relative differences in metallicity, dust content,
and ionization states, suggesting internal metal and dust exchange within the
ultra-large cold gas structure. For the strong MgII absorber at z = 2.5652$, we
detect a dusty star-forming galaxy at a projected distance of $D = 38$ kpc.
This galaxy exhibits prominent HeI, [SIII], and Paschen$gamma$ lines, along
with significant dust continuum. It has a star formation rate of ~ 121 +/- 33
$M_{odot}$/yr and likely harbors a rotating disk. These findings tentatively
suggest that cold gas at high redshifts plays a critical role in driving disk
formation and actively participates in the transfer of metals and dust within
the overdense regions of the CGM.”}]] 

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