2013/07/31 by L. Peralta de Arriba, M. Balcells, J. Falcón-Barroso +3 · 1 citation
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Galaxies: Formation, Evolution, Phenomena #Galaxy #Physics #Stellar, planetary, and galactic studies #astro-ph.CO #astro-ph.GA
paper · pdf · doi:10.1093/mnras/stu317
published as Monthly Notices of the Royal Astronomical Society 440 (2014), 1634-1648 · 15 pages, 15 figures, 2 tables. Updated to match the published version in MNRAS
openalex publication_date 2014/03/25 · arxiv created 2015/01/25 · arxiv updated 2015/02/02 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
For many massive compact galaxies, their dynamical masses (Mdyn ∝ σ2re) are lower than their stellar masses (M⋆). We analyse the unphysical mass discrepancy M⋆/Mdyn > 1 on a stellar-mass-selected sample of early-type galaxies (M⋆ ≳ 1011 M⊙) at redshifts z ∼ 0.2 to z ∼ 1.1. We build stacked spectra for bins of redshift, size and stellar mass, obtain velocity dispersions, and infer dynamical masses using the virial relation |Mdyn≡ K σ e2 re/ G| with K = 5.0; this assumes homology between our galaxies and nearby massive ellipticals. Our sample is completed using literature data, including individual objects up to z ∼ 2.5 and a large local reference sample from the Sloan Digital Sky Survey (SDSS). We find that, at all redshifts, the discrepancy between M⋆ and Mdyn grows as galaxies depart from the present-day relation between stellar mass and size: the more compact a galaxy, the larger its M⋆/Mdyn. Current uncertainties in stellar masses cannot account for values of M⋆/Mdyn above 1. Our results suggest that the homology hypothesis contained in the Mdyn formula above breaks down for compact galaxies. We provide an approximation to the virial coefficient K ∼ 6.0[re/(3.185 kpc)]−0.81[M⋆/(1011 M⊙)]0.45, which solves the mass discrepancy problem. A rough approximation to the dynamical mass is given by Mdyn ∼ [σe/(200 km s−1)]3.6[re/(3 kpc)]0.352.1 × 1011 M⊙.