Dynamical properties and star formation history of a low-mass quenched galaxy at cosmic noon

We present the spectroscopic confirmation and in-depth analysis of =2.0834 with łog(M_⋆/M_⊙)=9.6, observed with medium-resolution JWST/NIRSpec spectroscopy. Its stellar mass places approximately ten times lower than the knee of the stellar mass function for quiescent galaxies at z ^ a low-mass quiescent galaxy at z_ ̊m spec The deep medium-resolution spectrum enables the measurement of its stellar velocity dispersion (σ_⋆ = 95_ -33 +38 -1 ), the smallest value recorded among spectroscopically confirmed quiescent galaxies at z /M_⊙)=9.75_ Coupled with a compact size (0.41 in the rest-frame optical), the stellar velocity dispersion yields a dynamical mass estimate of łog(M_ ̊m kpc ̊m dyn -0.38 ^ +0.29 , consistent with the stellar mass, confirming the true low-mass nature of this galaxy and placing a first constraint on its initial mass function. Joint spectro-photometric spectral energy distribution fitting reveals a star formation history in which half the stellar mass was in place Gyr before the observed epoch, with quenching occurring Gyr prior to z=2.08. These results confirm that is genuinely quenched, rather than in a temporary phase of suppressed star formation. is consistent with the mass fundamental plane at z which was previously constrained only by massive quiescent systems with M_⋆ ,M_⊙ at cosmic noon. Compared with more massive counterparts at the same epoch observed with similar NIRSpec grating spectroscopy, the time since quenching for 11 is among the shortest observed. The star formation history of is broadly consistent with predictions for quiescent galaxies of similar mass and redshift in the IllustrisTNG and SHARK models. The galaxy resides in a possible dense group-scale (sim50 kpc) environment containing one companion with tentative spectroscopic redshift and five low-mass companion candidates with similar redshifts, and it is embedded in a large known protocluster on megaparsec scales. A potential environmental influence on its evolution could explain the outside-in quenching suggested by the positive gradient of size with wavelength. This study demonstrates that deep JWST/NIRSpec spectroscopy enables low-mass quiescent galaxies at cosmic noon to be characterized with a level of detail long reserved for massive systems, offering valuable new insights into how quenching operates in these underexplored, low-mass systems.