Abstract

Contributed Talk - Splinter Galaxies

Friday, 11 September 2026, 14:45   (MW-0250)

Vz-GAL: Revisiting the CO-H2 Conversion Factor Tension

Prachi Prajapati
University of Cologne

The CO-H2 conversion factor (αCO) remains one of the largest sources of uncertainty in determining molecular gas masses of high-redshift dusty star-forming galaxies (DSFGs). Scaling up the inferences from local ULIRGs to DSFGs, dynamical studies have often favored values lower than the canonical Galactic calibration; however, the origin of αCO tension in early DSFGs remains less understood. In this talk, I will present a revisit to the long-standing αCO discrepancy using the largest homogeneous sample of unlensed Vz-GAL DSFGs at z=1-4 with integrated CO(1-0) measurements and resolved ALMA 1 mm continuum observations. I will discuss two independent approaches for estimating molecular gas masses: the dust SED-based method and TUNER LVG modeling. The resulting gas masses will be compared with dynamical constraints derived from both the isotropic virial mass estimator and a mixed dynamical mass estimator that assumes DSFGs as rotating, pressure-supported thick disks. Finally, I will discuss whether the inferred molecular gas masses are consistent with the available dynamical upper limits across the sample, highlighting the archetype DSFG GN20 (z=4.055) as a case study.