Comparing Dynamical and Photometric Mass Estimates of Low‐ and High‐Redshift Galaxies: Random and Systematic Uncertainties

We determine the importance of redshift-dependent systematic effects in thedetermination of stellar masses from broad band spectral energy distributions(SEDs), using high quality kinematic and photometric data of early-typegalaxies at z~1 and z~0. We find that photometric masses of z~1 galaxies can besystematically different, by up to a factor of 2, from photometric masses ofz~0 galaxies with the same dynamical mass. The magnitude of this bias dependson the choice of stellar population synthesis model and the rest-framewavelength range used in the fits. The best result, i.e., without significantbias, is obtained when rest-frame optical SEDs are fitted with models fromBruzual&Charlot (2003). When the SEDs are extended to the rest-frame near-IR, abias is introduced: photometric masses of the z~1 galaxies increase by a factorof 2 relative to the photometric masses of the z~0 galaxies. When we use theMaraston (2005) models, the photometric masses of the z~1 galaxies are lowrelative to the photometric masses of the z~0 galaxies by a factor of ~1.8.This offset occurs both for fits based on rest-frame optical SEDs, and fitsbased on rest-frame optical+near-IR SEDs. The results indicate that modeluncertainties produce uncertainties as high as a factor of 2.5 in massestimates from rest-frame near-IR photometry, independent of uncertainties dueto unknown star formation histories.Comment: Accepted for publication in ApJ (12 pages, 11 figures