Discovery of a large H I ring around the quiescent galaxy AGC 203001 (associated paper)

Balt et al., 2020: the HI ring around AGC 203001

Here we report the discovery with the Giant Metrewave Radio Telescope of an extremely large (̃115 kpc in diameter) H I ring, located around a massive quenched galaxy, AGC 203001, but off-centered, with respect to it. This ring does not have any bright extended optical counterpart unlike several other known ring galaxies. Our deep g, r, and i optical imaging of the H I ring, using the MegaCam instrument on the Canada-France-Hawaii Telescope, shows however several regions with faint optical emission at a surface brightness level of ̃28 mag/arcsec2.

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Une vision fine des cirrus galactiques

En combinant des observations multi-longueur d’ondes obtenues depuis l’espace avec les satellites Planck et WISE et au sol avec le CFHT, une équipe de chercheurs notamment du CNRS et du CEA est parvenu à sonder la structure de la matière interstellaire avec une finesse inégalée. L’étude a en particulier permis de déterminer les propriétés de la turbulence interstellaire sur une gamme d’échelles spatiales encore jamais atteinte: de 10 pc à  0.01 pc. L’innovation principale de ces travaux est l’utilisation d’un télescope optique (le CFHT) pour étudier la structure de la matière à très grande résolution spatiale, ce que ne permettent pas les observations classiques du milieu interstellaire effectuées dans l’infrarouge. Ces travaux sont publiés dans la revue Astronomy and Astrophysics.

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Elliptical galaxies much younger than previously thought? (CFHT press release)

A sample of elliptical galaxies from the MATLAS survey, all showing clear signs of a recent collision @ Duc/CEA/CFHT

The standard model for elliptical galaxies formation is challenged by a new result uncovered by an international team of astronomers from the Atlas3D collaboration. Team members from CNRS, CEA, CFHT, and the Observatoire de Lyon published in the scientific journal Monthly Notices of the Royal Astronomical Society the first results from their study on two elliptical galaxies exhibiting features characteristic of a fairly recent merging, suggesting they are five times younger than commonly thought.

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The mysterious Leo giant gas ring explained by a billion year old collision between two galaxies

The Leo ring: deep image in the optical domain with the distribution of the gas in HI in yellow-orange. © CFHT/Astron – P.A. Duc

An international team unveiled the origin of the giant gas ring in the Leo group of galaxies. With the Canada-France-Hawaii Telescope, the scientists were able to detect an optical signature of the ring corresponding to star forming regions. This observation rules out the primordial nature of the gas, which is of galactic origin. Thanks to numerical simulations made at CEA, a scenario for the formation of this ring has been proposed: a violent collision between two galaxies, slightly more than one billion years ago. The results will be published in the Astrophysical Journal Letters.

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