The Mass Scale of High-redshift Galaxies: Virial Mass Estimates Calibrated with Stellar Dynamical Models from LEGA-C
Arjen van der Wel, Josha van Houdt, Rachel Bezanson, Marijn Franx, Francesco D’Eugenio, Caroline M. S. Straatman, Eric F. Bell, Adam Muzzin, David Sobral, Michael V. Maseda, Anna de Graaff, B. Holden
Abstract
Abstract Dynamical models for 673 galaxies at z = 0.6–1.0 with spatially resolved (long-slit) stellar kinematic data from LEGA-C are used to calibrate virial mass estimates defined as <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>vir</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mi>K</mml:mi> <mml:mi>σ</mml:mi> <mml:msubsup> <mml:mrow> <mml:mo accent="true">′</mml:mo> </mml:mrow> <mml:mrow> <mml:mo>⋆</mml:mo> <mml:mo>,</mml:mo> <mml:mi>int</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msubsup> <mml:mi>R</mml:mi> </mml:math> , with K a scaling factor, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>σ</mml:mi> <mml:msub> <mml:mrow> <mml:mo accent="true">′</mml:mo> </mml:mrow> <mml:mrow> <mml:mo>⋆</mml:mo> <mml:mo>,</mml:mo> <mml:mi>int</mml:mi> </mml:mrow> </mml:msub> </mml:math> the spatially integrated stellar velocity second moment from the LEGA-C survey, and R the effective radius measured from a Sérsic profile fit to Hubble Space Telescope imaging. The sample is representative for M ⋆ > 3 × 10 10 M ⊙ and includes all types of galaxies, irrespective of morphology and color. We demonstrate that using R = R sma (the semimajor axis length of the ellipse that encloses 50% of the light) in combination with an inclination correction on <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>σ</mml:mi> <mml:msub> <mml:mrow> <mml:mo accent="true">′</mml:mo> </mml:mrow> <mml:mrow> <mml:mo>⋆</mml:mo> <mml:mo>,</mml:mo> <mml:mi>int</mml:mi> </mml:mrow> </mml:msub> </mml:math> produces an unbiased M vir . We confirm the importance of projection effects on <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>σ</mml:mi> <mml:msub> <mml:mrow> <mml:mo accent="true">′</mml:mo> </mml:mrow> <mml:mrow> <mml:mo>⋆</mml:mo> <mml:mo>,</mml:mo> <mml:mi>int</mml:mi> </mml:mrow> </mml:msub> </mml:math> by showing the existence of a similar residual trend between virial mass estimates and inclination for the nearby early-type galaxies in the ATLAS 3D survey. Also, as previously shown, when using a Sérsic profile-based R estimate, a Sérsic index-dependent correction to account for nonhomology in the radial profiles is required. With respect to analogous dynamical models for low-redshift galaxies from the ATLAS 3D survey we find a systematic offset of 0.1 dex in the calibrated virial constant for LEGA-C, which may be due to physical differences between the galaxy samples or an unknown systematic error. Either way, with our work we establish a common mass scale for galaxies across 8 Gyr of cosmic time with a systematic uncertainty of at most 0.1 dex.