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The origin of the gas in between the Magellanic Clouds (MCs), known as the Magellanic Bridge, has always been the subject of controversy. To shed light into this, we present the results from the MAGellanic Inter-Cloud II (MAGIC II) project aimed at probing the stellar populations in 10 large fields located perpendicular to the main ridge-line of H i in the Inter-Cloud region. We secured these observations of the stellar populations in between the MCs using the WFI (Wide Field Imager) camera on the 2.2 m telescope in La Silla. Using colour-magnitude diagrams, we trace stellar populations across the Inter-Cloud region. In good agreement with MAGIC I, we find significant intermediate-age stars in the Inter-Cloud region as well as young stars of a similar age to the last pericentre passage in between the MCs (~200 Myr ago). We show here that the young, intermediate-age and old stars have distinct spatial distributions. The young stars correlate well with the H i gas suggesting that they were either recently stripped from the Small Magellanic Cloud (SMC) or formed in situ. The bulk of intermediate-age stars are located mainly in the Bridge region where the H i column density is higher, but they are more spread out than the young stars. They have very similar properties to stars located ~2 kpc from the SMC centre, suggesting that they were tidally stripped from this region. Finally, the old stars extend to some 8 kpc from the SMC supporting the idea that all galaxies have a large extended metal-poor stellar halo. [ABSTRACT FROM AUTHOR]

ABSTRACT We model the formation of Auriga's Wheel - a recently discovered collisional ring galaxy. Auriga's Wheel has a number of interesting features including a bridge of stars linking the neighbouring elliptical to the ring galaxy, and evidence for components of expansion and rotation within the ring. Using N-body/smoothed particle hydrodynamics modelling, we study collisions between an elliptical galaxy and a late-type disc galaxy. A near direct collision, with a mildly inclined disc, is found to reasonably reproduce the general system morphology ∼50 Myr following the collision. The collision must have a relatively low velocity (initially ∼150 km s−1) in order to form the observed bridge, and simultaneously match the galaxies separation. Our best-match model suggests the total disc galaxy is ∼5 times more massive than the elliptical. We find that the velocity of expansion of the ring is sensitive to the mass of the elliptical, while insensitive to the encounter velocity. We evolve our simulation beyond the current epoch to study the future destiny of the galaxy pair. In our model, the nucleus moves further away from the plane of the ring in the direction of the stellar bridge. The nucleus eventually merges with the elliptical galaxy ∼100 Myr after the present time. The ring continues to expand for ∼200 Myr before collapsing back. The low initial relative velocity of the two galaxies will eventually result in a complete merger. [ABSTRACT FROM AUTHOR]

As part of a radial velocity survey of low Galactic latitude structures that we undertook with the 2dF spectrograph on the Anglo-Australian Telescope, we present the radial velocities of more than 1500 red giant branch and red clump stars towards the centre of the Canis Major dwarf galaxy. With a mean velocity of at a heliocentric distance of 5.5 kpc and at 8.5 kpc, these stars present a peculiar distance – radial velocity relation that is unlike that expected from thin or thick disc stars. Moreover, they belong to a kinematically cold population with an intrinsic dispersion that may be as low as 11+3−1 km s−1. A comparison of the velocity distribution obtained in this work with previous studies shows the importance of using our new reduction pipeline and averaging the velocities obtained from different templates. The radial velocity distribution is used to select Canis Major stars in the UCAC2.0 proper motion catalogue and derive proper motions in Galactic coordinates of for the dwarf galaxy, which after correcting for the reflex solar motion along this line of sight gives , corresponding to a prograde orbit with a tangential velocity of ∼235 km s−1 at the average distance of ∼7.2 kpc. All these kinematic constraints can be reproduced in simulations of the accretion of a dwarf on to the Galactic disc. Such a process could also be responsible for the Monoceros Ring that has recently been shown to encompass the Galactic disc. However, without constraints on the kinematics of the tidal arms emerging from the Canis Major dwarf, it is not yet possible to definitively prove a link between the two structures. [ABSTRACT FROM AUTHOR]

In response to recent criticism by Momany et al., that the recently identified Canis Major (CMa) overdensity could be simply explained by the Galactic warp, we present proof of the existence of a stellar population in the direction of CMa that cannot be explained by known Galactic components. By analysing the radial distribution of counts of M-giant stars in this direction, we show that the Momany et al. warp model overestimates the number of stars in the Northern hemisphere, hence hiding the CMa feature in the South. The use of a better model of the warp has little influence on the morphology of the overdensity and clearly displays an excess of stars grouped at a distance of. To lend further support to the existence of a population that does not belong to the Galactic disc, we present radial velocities of M-giant stars in the centre of the CMa structure that were obtained with the 2dF spectrograph at the Anglo-Australian Telescope. The extra population shows a radial velocity of, which is significantly higher than the typical velocity of the disc at the distance of CMa. This population also has a low dispersion. The Canis Major overdensity is therefore highly unlikely to be due to the Galactic warp, adding weight to the hypothesis that we are observing a disrupting dwarf galaxy or its remnants. This leads to questions on what part of CMa was previously identified as the Warp and how possibly to disentangle the two structures. [ABSTRACT FROM AUTHOR]

We report the discovery of two ultra-faint satellites in the vicinity of the Large Magellanic Cloud (LMC) in data from the Magellanic Satellites Survey (MagLiteS). Situated 18 deg (~20 kpc) from the LMC and separated from each other by only 18 arcmin, Carina II and III form an intriguing pair. By simultaneously modelling the spatial and the colour-magnitude stellar distributions, we find that bothCarina II and Carina III are likely dwarf galaxies, although this is less clear for Carina III. There are in fact several obvious differences between the two satellites. While both are well described by an old and metal poor population, Carina II is located at ~36 kpc from the Sun, with MV ~-4.5 and rh ~ 90 pc, and it is further confirmed by the discovery of 3 RR Lyrae at the right distance. In contrast, Carina III is much more elongated, measured to be fainter (MV ~-2.4), significantly more compact (rh ~ 30 pc), and closer to the Sun, at ~28 kpc, placing it only 8 kpc away from Car II. Together with several other systems detected by the Dark Energy Camera, Carina II and III form a strongly anisotropic cloud of satellites in the vicinity of the Magellanic Clouds. [ABSTRACT FROM AUTHOR]

As part of our radial velocity survey of low Galactic latitude structures that surround the Galactic disc, we report the detection of the so-called Monoceros Ring in the foreground of the Carina dwarf galaxy at Galactic coordinates based on Very Large Telescope/Fibre Large Array Multi Element Spectrograph observations of the dwarf galaxy. At this location, 20° in longitude greater than previous detections, the Ring has a mean radial velocity of and a velocity dispersion of only . Based on Keck/Deep Imaging Multi-Object Spectrograph observations, we also determine that the Ring has a mean radial velocity of in the foreground of the Andromeda galaxy at , along with a velocity dispersion of . These two kinematic detections are both highly compatible with known characteristics of the structure and, along with previous detections, provide radial velocity values of the Ring over the range. This should place strong constraints on numerical models of the accretion of the dwarf galaxy that is believed to be the progenitor of the Ring. [ABSTRACT FROM AUTHOR]