2019/01/31 by Shany Danieli, Pieter van Dokkum, Charlie Conroy +2 · 148 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics #Dark matter #Dark matter halo #Galaxies: Formation, Evolution, Phenomena #Galaxy #Globular cluster #Halo #Milky Way #Physics #RADIUS #Star formation #Stars #Stellar kinematics #Stellar mass #Stellar, planetary, and galactic studies #Velocity dispersion #astro-ph.GA
paper · pdf · doi:10.3847/2041-8213/ab0e8c
published in The Astrophysical Journal Letters 874(2), L12 (IOP Publishing) · ApJ Letters, in press
openalex created_date 2019/01/25 · arxiv created 2019/03/11 · openalex publication_date 2019/03/27 · arxiv updated 2019/04/03 · openalex updated_date 2026/08/06
Abstract The velocity dispersion of the ultra diffuse galaxy NGC1052-DF2 was found to be km s −1 , much lower than expected from the stellar mass–halo mass relation and nearly identical to the expected value from the stellar mass alone. This result was based on the radial velocities of 10 luminous globular clusters that were assumed to be associated with the galaxy. A more precise measurement is possible from high-resolution spectroscopy of the diffuse stellar light. Here we present an integrated spectrum of the diffuse light of NGC1052-DF2 obtained with the Keck Cosmic Web Imager (KCWI), with an instrumental resolution of σ instr ≈ 12 km s −1 . The systemic velocity of the galaxy is v sys = 1805 ± 1.1 km s −1 , in very good agreement with the average velocity of the globular clusters ( km s −1 ). There is no evidence for rotation within the KCWI field of view. We find a stellar velocity dispersion of km s −1 , consistent with the dispersion that was derived from the globular clusters. The implied dynamical mass within the half-light radius r 1/2 = 2.7 kpc is M dyn = (1.3 ± 0.8) × 10 8 M ⊙ , similar to the stellar mass within that radius ( M stars = (1.0 ± 0.2) × 10 8 M ⊙ ). With this confirmation of the low velocity dispersion of NGC1052-DF2, the most urgent question is whether this “missing dark matter problem” is unique to this galaxy or applies more widely.