- Particulars
- Printed on 08 January 2024
Vol. 680
4. Extragalactic astronomy
An virtually darkish galaxy with the mass of the Small Magellanic Cloud
Some low floor brightness galaxies are so weak that they elude detection within the Sloan Digital Sky Survey. These “virtually darkish galaxies” have a pink floor brightness on the middle of greater than 26 magazine/arcsec2, equivalent to a stellar floor density of lower than just a few photo voltaic lots per computer^2. This small quantity of stars implies that no stellar suggestions has modified its darkish matter halo distribution. These objects thus provide an fascinating chance to constrain the microphysical properties of darkish matter. The authors report on the serendipitous discovery with deep imaging of Nube, an virtually darkish galaxy positioned at a distance of 107 Mpc. From observations with the 100m Inexperienced Financial institution Telescope, they derive a darkish halo mass of two.6 10^{10} Msun. Extremely-deep multi-band observations with the ten.4m Gran Telescopio Canarias favor an age of ∼ 10 Gyr and a metallicity of [Fe/H]∼ −1.1. With a stellar mass of ∼ 4×10^8 Msun and a half-mass radius of Re = 6.9 kpc, Nube is essentially the most large and prolonged object of its sort found up to now. The galaxy is ten occasions fainter and has an efficient radius 3 times bigger than typical ultra-diffuse galaxies with related stellar lots. Present cosmological simulations inside the chilly darkish matter situation, together with baryonic suggestions, don’t reproduce the structural properties of Nube. They’re, nevertheless, suitable with a fuzzy darkish matter situation through which the darkish matter particles are ultra-light axions with a mass of 0.8 10^{-23} eV, in settlement with different astrophysical constraints.
