2009/06/30 by Michele Cappellari, S. di Serego Alighieri, A. Cimatti +11 · 1 citation
Engineering · Physics and Astronomy · #Astronomy and Astrophysical Research #Galaxies: Formation, Evolution, Phenomena #Space Technology and Applications #astro-ph.CO #astro-ph.GA
paper · pdf · doi:10.1088/0004-637x/704/1/l34
published as Astrophys.J.704:L34-L39,2009 · 6 pages, 4 figures, LaTeX with emulateapj. Accepted for publication in ApJ Letters
arxiv created 2009/09/04 · openalex publication_date 2009/09/24 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/01
We measured stellar velocity dispersions σ and derived dynamical masses of nine massive ( M ≈ 10 11 M ☉ ) early-type galaxies (ETGs) from the Galaxy Mass Assembly ultra-deep Spectroscopic Survey (GMASS) sample at redshift 1.4 ≲ z ≲ 2.0. The σ are based on individual spectra for two galaxies at z ≈ 1.4 and on a stacked spectrum for seven galaxies with 1.6 < z < 2.0, with 202 hr of exposure at the ESO Very Large Telescope. We constructed detailed axisymmetric dynamical models for the objects, based on the Jeans equations, taking the observed surface brightness (from deep HST /ACS observations), point-spread function, and slit effects into account. Our dynamical masses M Jeans agree within ≲30% with virial estimates M vir = 5 × R e σ 2 / G , although the latter tend to be smaller. Our M Jeans also agrees within a factor ≲2 with the M pop previously derived using stellar population models and 11 bands photometry. This confirms that the galaxies are intrinsically massive. The inferred mass-to-light ratios ( M / L ) U in the very age-sensitive rest-frame U band are consistent with passive evolution in the past ∼1 Gyr (formation redshift z f ∼ 3). A "bottom-light" stellar initial mass function appears to be required to ensure close agreement between M Jeans and M pop at z ∼ 2, as it does at z ∼ 0. The GMASS ETGs are on average more dense than their local counterpart. However, a few percent of local ETGs of similar dynamical masses also have comparable σ and mass surface density Σ 50 inside R e .