How large can galaxies be? Ultra-deep imaging of IC 1101, the most extended known galaxy

Le résumé fourni par la source

The maximum physical extent that galaxies can reach is poorly understood. In this regard, IC 1101, one of the most extended and massive galaxies known, provides a valuable opportunity to constrain the upper limit of galaxy sizes at the present epoch. Previous deep imaging of the system confirmed its enormous extension, but did not indicate whether it has an edge. We explore this issue using the deepest images ever taken of this galaxy; ultra-deep and bands imaging from the INT/WFC, reaching μ ∼ 30 mag arcsec g r -2 $ (3σ in an area equivalent to 10 ^2). We model and subtract the scattered light from both stars and the galaxy itself using an extended point spread function characterisation and a hybrid wavelet-based deconvolution. Using a combination of surface brightness, colour, and stellar mass density profiles oriented at different position angles, we find that the main body of IC 1101 extends to R_ 10 arcsec edge ≈ 260 kpc along the semi-major axis (assuming the redshift of Abell 2029, z = 0.077), enclosing sim3.4 M_⊙ in stars. This $R_ 10^ 12 edge is among the largest edge radii measured for any galaxy to date, placing IC 1101 at the extreme upper end of the mass–size relation. In addition, we report a large number of asymmetrical, very low-surface-brightness features around the galaxy that are spatially consistent with the large-scale disturbances observed in the intracluster medium through X-ray studies of the Abell 2029 cluster, in which IC 1101 is embedded. With a confirmed diameter of around 520 kpc, IC 1101 stands as the largest galaxy known to date; yet, its outskirts show clear signatures of ongoing mass assembly, indicating that its spatial extent is still growing.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.