两级阶梯：仅由红巨星分支尖端和几何锚定推断的 $H_0$
Two-rung ladder: $H_0$ from Tip of the Red Giant Branch and geometric anchors alone
- University of Oxford（牛津大学）
- University of Portsmouth（朴茨茅斯大学）
- CNRS & Sorbonne Université（法国国家科学研究中心与索邦大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究利用TRGB距离和几何锚定构建两级阶梯推断哈勃常数，发现场间散布限制精度，加权后得$H_0$约68-72 km/s/Mpc，尚不能仲裁哈勃张力。
AI中文摘要：
我们从约400个具有红巨星分支尖端（TRGB）距离的河外距离数据库宿主中推断哈勃常数 $H_0$，这些距离以大麦哲伦云和NGC 4258的几何锚定进行校准。我们对尖端星等和宿主红移进行前向建模，包括星等限制选择、天空曝光和密度相关的星系偏置，并依次以80个Manticore-Local局部密度和本动速度场实现中的每一个为条件。由于大多数宿主位于 $cz_{\rm CMB} \lesssim 1000$ km/s，此处本动速度很重要，因此推断受这些场的方差限制，而非TRGB校准。对于固定实现，红移似然和密度平滑各自使 $H_0$ 移动小于1 km/s/Mpc，速度单极子移动 $5.4 \pm 3.4$ km/s/Mpc，而 $H_0$ 的场间散布为5.2 km/s/Mpc。对各实现的后验进行等权加权得到 $H_0 = 68.4 \pm 5.9$ km/s/Mpc，而按贝叶斯证据加权则得到 $72.3 \pm 2.6$ km/s/Mpc。后者由单个特别高证据的实现决定，使其对重建后验的有限采样敏感。因此，该阶梯目前无法仲裁哈勃张力。将TRGB数据扩展到当前约1000 km/s之外，并改进对局部宇宙的重建，将把场间散布降至远低于我们此处发现的5.2 km/s/Mpc。
英文摘要：
We infer the Hubble constant $H_0$ from the ~400 Extragalactic Distance Database hosts with a tip of the red giant branch (TRGB) distance, calibrated on the geometric anchors of the Large Magellanic Cloud and NGC 4258. We forward-model the tip magnitudes and host redshifts including magnitude-limited selection, sky exposure, and density-dependent galaxy bias, conditioning on each of the 80 Manticore-Local realisations of the local density and peculiar-velocity fields in turn. As most hosts lie at $cz_{\rm CMB} \lesssim 1000$ km/s, where peculiar velocities are important, the inference is limited by the variance of these fields rather than by the TRGB calibration. For a fixed realisation, the redshift likelihood and density smoothing each move $H_0$ by less than 1 km/s/Mpc and a velocity monopole by $5.4 \pm 3.4$ km/s/Mpc, whereas the field-to-field scatter in $H_0$ is 5.2 km/s/Mpc. Weighting the posteriors from each realisation equally gives $H_0 = 68.4 \pm 5.9$ km/s/Mpc, while weighting each by its Bayesian evidence gives $72.3 \pm 2.6$ km/s/Mpc. The latter value is set by a single particularly high-evidence realisation, making it sensitive to the finite sampling of the reconstruction posterior. This ladder therefore cannot yet arbitrate the Hubble tension. Extending the TRGB data beyond the present ~1000 km/s, together with improved reconstructions of the local Universe, would reduce the field-to-field scatter well below the 5.2 km/s/Mpc we find here.
