The Concordance of Weak Lensing and Escape-velocity Mass Estimates for Galaxy Clusters

Abstract In the Λ cold dark matter paradigm, the masses of the galaxy clusters inferred using background galaxies via weak-lensing shear should agree with the masses measured using the galaxy projected radius–velocity phase-space data via the escape velocity profile. However, prior work indicates that the correlation between caustic-inferred escape masses and weak lensing masses is statistically consistent with zero. Based on recent advancements in the measurement of the escape edge and its physical interpretation, we conduct a revised comparison between these two independent mass inference techniques for 46 galaxy clusters between 0.05 ≤ z ≤ 0.3 and over an order of magnitude in mass, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>14.4</mml:mn> <mml:mspace width="0.25em"/> <mml:mo>≤</mml:mo> <mml:mspace width="0.25em"/> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">log</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> </mml:msub> <mml:mi>M</mml:mi> <mml:mo>/</mml:mo> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> <mml:mspace width="0.25em"/> <mml:mo>≤</mml:mo> <mml:mspace width="0.25em"/> <mml:mn>15.4</mml:mn> </mml:math> . We find excellent agreement, with a correlation ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>0.67</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>9</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.049</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.046</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> ), and a mean relative difference between the two mass measurements consistent with zero (0.02 ± 0.02 dex). The observed scatter between these direct mass estimates is 0.17 dex and is consistent with the reported individual mass errors, suggesting that there is no need for an additional intrinsic component. We discuss the important practical consequences of these results, focusing on the systematic uncertainties inherent to each technique, and their implications for cosmology.