Determine the origin of the low-ionization absorption system

Determine whether the low-ionization absorption system at approximately -3407 km s relative to the quasar systemic redshift originates in foreground gas or in gas associated with the quasar, including dense or shielded material in an outflow.

Background

The JWST/NIRSpec spectrum reveals strong absorption in Mg II, Fe II, Si II, O I, and C II at a velocity offset of approximately -3407 km s. Unlike the high-ionization systems, whose multiple ionic species and blueshifts support an association with a quasar outflow, the physical association of this low-ionization system cannot be established from the current data. The authors identify both intervening foreground gas and quasar-associated dense or shielded outflowing gas as viable possibilities.

References

The origin of this low-ionization system remains uncertain. The absorption could arise in foreground gas or in gas associated with the quasar, including dense or shielded material in an outflow.

— A dust-reddened quasar in a [C II]-luminous host at z=6.55  (2610.13758 - Yang et al., 9 Oct 2026) in Section 3.2, “Absorption systems”