Context. A small fraction of early-type galaxies (ETGs) show prolate rotation, i.e. they rotate around their long photometric axis. In simulations, certain configurations of galaxy mergers are known to produce this type of rotation.
Aims. We investigate the association of prolate rotation and signs of (past) galaxy interactions among the observed galaxies.
Ultra-diffuse galaxies (UDGs) are very low-surface brightness galaxies with large effective radii. Spectroscopic measurements of a few UDGs have revealed a low dark matter content, based on the internal motion of stars or globular clusters (GCs). This is in contrast to the large number of GCs found for these systems, from which it would be expected to correspond to a large dark matter halo mass. Here we present Hubble Space Telescope Advanced Camera Survey observations for the UDG MATLAS-2019 in the NGC5846 group of galaxies.Continue reading “Dwarf galaxies in the MATLAS survey: Hubble Space Telescope observations of the globular cluster system in the ultra-diffuse galaxy MATLAS-2019”
Deep imaging, that is imaging capable of capturing very low surface brightness extended objects, is a quickly growing field of extragalactic astronomy. Not only can new types of faint objects be discovered, but deep images of bright galaxies are very valuable, too, since they reveal faint signs of past galaxy collisions, the tidal features. Such “archeological” record can be exploited for investigating how galaxies formed. In the MATLAS survey, we obtained extremely deep images of 177 nearby massive elliptical and lenticular galaxies using the 3.5m Canada-France-Hawaii Telescope.Continue reading “The MATLAS survey of faint outskirts of bright galaxies”
Accounting for the morphology is an essential constraint for the theory of galaxy formation. The low-surface brightness regions of galaxies host multiple morphological features that any realistic model should consider; however they are still not fully explored because of observational difficulties. Here we present the results of our visual inspections of very deep images of a complete large volume-limited sample of 177 nearby massive early-type galaxies (ETGs) from the MATLAS survey.Continue reading “Census and classification of low-surface-brightness structures in nearby early-type galaxies from the MATLAS survey”
Stellar shells around galaxies could provide precious insights into their assembly history. However, their formation mechanism remains poorly empirically constrained, regarding in particular the type of galaxy collisions at their origin. We present MUSE at VLT data of the most prominent outer shell of NGC 474, to constrain its formation history. The stellar shell spectrum is clearly detected, with a signal-to-noise ratio of ∼65 pix-1. We used a full spectral fitting method to determine the line-of-sight velocity and the age and metallicity of the shell and associated point-like sources within the MUSE field of view.Continue reading “Revealing the formation mechanism of the shell galaxy NGC474 with MUSE”
The MATLAS deep imaging survey has uncovered a plethora of dwarf galaxies in the low density environment it has mapped. A fraction of them are unusually extended and have a low-surface brightness. Among these so-called ultra-diffuse galaxies, a few seem to host an excess of globular clusters. With the integral-field unit spectrograph MUSE we have observed one of these galaxies – MATLAS J15052031+0148447 (MATLAS-2019) – located towards the nearby group NGC 5846 and measured its systemic velocity, age, and metallicity, and that of its globular clusters candidates.Continue reading “A spectroscopic study of MATLAS-2019 with MUSE: an ultra-diffuse galaxy with an excess of old globular clusters”