Identify the appropriate stellar-light tracer for lens-galaxy kinematics

Determine which photometric band best traces the stellar population dominating the measured spectroscopic velocity-dispersion signal of the lens galaxies G1 and G2 in the SN 2025wny system, thereby reducing systematic uncertainties in the Jeans dynamical modelling.

Background

The paper supplements the strong-lensing analysis of SN 2025wny with stellar velocity-dispersion measurements for the two lens galaxies, G1 and G2. To predict these dispersions, the authors use a spherical Jeans model, assume isotropic stellar orbits, and adopt the F814W surface-brightness model as the stellar tracer within an aperture of twice the effective radius.

The authors emphasize that the spectroscopic dispersions are derived from absorption features spanning a broad wavelength range, whereas the adopted photometric tracer may not represent the same stellar population. Wavelength-dependent seeing and point-spread functions also affect the effective spectroscopic aperture. Resolving which photometric band and tracer population are appropriate would help control the dynamical systematics that propagate into the lens-mass and Hubble-constant inferences.

References

However, the observed dispersions are inferred from spectra using many absorption features spanning a broad wavelength range, making it unclear which photometric band best traces the stellar population dominating the measured kinematic signal.

— Follow-up of SN 2025wny V: Lens Modelling and Cosmography of a Strongly Lensed Superluminous Supernova at $z = 2.015$ using Space Data  (2608.28430 - Mörtsell et al., 28 Aug 2026) in Section 4.4, “Stellar velocity dispersions”