A 5deg x 5deg deep H i survey of the M81 group

Abstract

A 25 deg 2 region, including the M81 complex (M81, M82, NGC 3077), NGC 2976 and IC2574, was mapped during ∼ 3000 hours with the DRAO synthesis telescope. With a physical resolution of ∼ 1 kpc, these observations allow us to probe a large region down to column density levels of ∼ 1 × 10 18 cm −2 over 16 km s −1 , mapping the extent of the Hi arm connecting the system and NGC 2976, and resolving the Hi clouds adjacent to the arm. The observations also reveal a few clouds located between the system and IC 2574, probably tidally stripped from a past interaction between the two systems. Given the regular velocity distribution in the Hi envelope of the system, we attempt and derive an idealised large-scale rotation curve of the system. We observe a flat trend for the rotation velocity of the overall system from 20 kpc out to 80 kpc, well beyond the outskirts of the M81 disk, although with asymmetries like a wiggle at the vicinity of M82. This supports the assumption that intergalactic gas and galaxies in the system participate to a large-scale ordered rotation motion which is dominated by M81. Also, our Hi analysis of the group further supports the hypothesis that the galaxies forming the system moved closer from afar, in agreement with numerical simulations.

Star formation in the nearby dwarf galaxy DDO 53: interplay between gas accretion and stellar feedback

“…All these galaxies are gas rich and reveal extended complexes of star formation with prominent feedback-driven superbubbles, and in most of them the long duration of star formation activity led to the creation of so called supergiant shells (SGS), having sizes up to 2 kpc, the interaction of which could be a driver of star formation propagation (Egorov et al 2017;Vasiliev et al 2020). H i observations revealed a presence of gaseous tidal tails or surrounding high velocity clouds around some of the mentioned galaxies thus indicating their interaction with the IGM in the M81 group (Ashley et al 2017;Sorgho et al 2019Sorgho et al , 2020.…”

The relationship between gas and galaxies at z<1 using the Q0107 quasar triplet

“…Galaxies follow a large-scale filamentary structure throughout the Universe, known as the cosmic web (Bond et al 1996), formed by the gravitational accretion of gas towards the potential wells of dark matter around initial overdensities, as has been modelled in darkmatter-only simulations for decades (e.g. Klypin & Shandarin 1983;Springel et al 2005). Once stars and galaxies form, this accretion from the intergalactic medium (IGM) towards galaxies becomes affected by complex baryonic physics, including stellar and AGN feedback (e.g.…”

“…Mathewson et al 1974;Nidever et al 2008) and the M81/M82 group (e.g. Croxall et al 2009;Sorgho et al 2019), as well as H𝛼 and occasionally [O ] emission in dense environments (e.g Fumagalli et al 2014;Johnson et al 2018;Fossati et al 2019a).…”

Ionized gas in the NGC 3077 galaxy

“…1). HI line observations show that the galaxy is located near a giant tidal structure, which connects it to M 81 and M 82 (Yun et al, 1994;Sorgho et al, 2019), and the entire system is sometimes called the "M 81 triplet" (de Blok et al, 2018). On the southern side of the galaxy a chain of clusters of blue stars and compact H II regions can be seen-it is the "Garland" tidal galaxy (Karachentsev et al, 1985;Makarova et al, 2002), which is located in a region of high H I density.…”