Does the inverse distance ladder rule out late-time solutions to the Hubble tension? A model-independent test using DES-Dovekie supernovae and DESI DR2 BAO

Abstract

It has been argued that the inverse distance ladder disfavours late-time solutions to the Hubble tension. We test this with a cosmographic expansion where $H$ is a fourth-order polynomial in $1 - a$. We combine the uncalibrated DES-Dovekie SNIa with DESI~DR2 BAO, assuming a standard sound horizon $r_{\rm d} = 147.05 \pm 0.30$~Mpc. Using only DES SNIa yields $H_0 = 76.25 \pm 2.87$ km/s/Mpc, which is $3.1σ$ above the CMB-calibrated $Λ$CDM prediction but consistent with SH0ES ($1.0σ$). Adding the legacy SNIa decreases $H_0$ to $67.98 \pm 0.69$ km/s/Mpc, $4.7σ$ below SH0ES. The $8.27$ km/s/Mpc drop in $H_0$ upon including the legacy SNIa cannot be attributed to expected sample variance: under a fiducial $Λ\text{CDM}$ model, only $1.24\%$ of $10^4$ mock realisations exhibit such a large $H_0$ shift due to the changed redshift sampling. This points to a systematic tension between DES and legacy SNIa datasets. We next add local $H_0$ anchors (the bright siren, SNII, TRGB + SBF) and test a parametrisation where the $Λ$CDM $H(z)$ is enhanced by $ΔH(z) = A \exp (-z/z_1)$. We recover $H_0 = 70.00^{+4.78}_{-0.98}$ km/s/Mpc and $z_1 < 0.086$ at $1σ$ confidence using DES SNIa, but $H_0 = 67.66 \pm 1.01$ km/s/Mpc and $z_1$ is unconstrained using DES + legacy. Late-time solutions are thus viable with the homogeneous DES catalogue, but not with the legacy SNIa as published. Allowing them to be arbitrarily recalibrated relative to the main DES sample yields an inferred offset of $ΔM_\rm{legacy} = 0.0646 \pm 0.0391$~mag, raising the predicted $H_0$ to $71.03 \pm 1.99$ km/s/Mpc. Ongoing SNIa surveys like DEBASS will provide a homogeneous sample of SNIa down to redshifts accessible via the distance ladder, assessing the validity of the current legacy samples and hence the feasibility of late-time solutions to the Hubble tension.