The VMC survey – XXXIV. Morphology of stellar populations in the Magellanic Clouds

Abstract

The Magellanic Clouds are nearby dwarf irregular galaxies whose morphologies show different properties when traced by different stellar populations, making them an important laboratory for studying galaxy morphologies. We study the morphology of the Magellanic Clouds using data from the VISTA survey of the Magellanic Clouds system (VMC). We used about 10 and 2.5 million sources across an area of ∼ 105 deg 2 and ∼ 42 deg 2 towards the Large and Small Magellanic Cloud (LMC and SMC), respectively. We estimated median ages of stellar populations occupying different regions of the near-infrared (J − K s , K s ) colour-magnitude diagram. Morphological maps were produced and detailed features in the central regions were characterised for the first time with bins corresponding to a spatial resolution of 0.13 kpc (LMC) and 0.16 kpc (SMC). In the LMC, we find that main sequence stars show coherent structures that grow with age and trace the multiple spiral arms of the galaxy, star forming regions become dimmer as we progress in age, while supergiant stars are centrally concentrated. Intermediate-age stars, despite tracing a regular and symmetrical morphology, show central clumps and hints of spiral arms. In the SMC, young main sequence stars depict a broken bar. Intermediate-age populations show signatures of elongation towards the Magellanic Bridge that can be attributed to the LMC-SMC interaction ∼ 200 Myr ago. They also show irregular central features suggesting that the inner SMC has also been influenced by tidal interactions.

The VMC survey – XLIV: mapping metallicity trends in the large magellanic cloud using near-infrared passbands

“…2 shows how we select the shape and size of the trapezoid. The shape is similar to that of region 'K' adopted by El Youssoufi et al (2019) to select the RGB population from VMC (Ks, J − Ks) CMDs to estimate morphological maps. We start by creating a density diagram by combining CMDs of subregions from different locations within the LMC: central region -tiles LMC 7 4 and 7 5; outer regions in all four directions -tiles LMC 2 5, 5 2, 6 9 and 9 3.…”

“…The SMC exhibits dynamically distorted features in its stellar populations because of interactions with the LMC (e.g. Nidever et al 2013;Subramanian et al 2017;El Youssoufi et al 2019;Niederhofer et al 2021;Gaia Collaboration et al 2021). Several distinct (sub)structures have been discovered in the LMC's outskirts (e.g.…”

Magellanic Mayhem: Metallicities and Motions

“…Centrally, the SMC displays a less prominent bar as well as an eastern wing structure first observed by Shapley (1940), departing from the northern end of the bar toward the LMC. Recent mapping of the SMC by El Youssoufi et al (2019) has shown the morphology of the younger stellar populations to be highly irregular and largely limited to the SMC bar and eastern wing, tracing the perturbed gaseous reservoir of the SMC (Stanimirović et al 2004), with recent star formation expected to have occurred in these regions (see, e.g., Irwin et al 1990;El Youssoufi et al 2019). The older stellar populations, on the other hand, display a much more homogeneous spatial distribution (see, e.g., Zaritsky et al 2000;Haschke et al 2012;Jacyszyn-Dobrzeniecka et al 2017) and indeed are offset from the younger populations, as observed by Mackey et al (2018).…”

The VMC survey – XLI. Stellar proper motions within the Small Magellanic Cloud

“…Neutral hydrogen gas within the SMC's main body has a prominent triangularly shaped distribution with an eastern extension, the SMC Wing, located towards the Magellanic Bridge. Young stars ( 300 Myr old) mainly follow the H I gas structure, while the old stellar population ( 5 Gyr old) is distributed in a more regular spheroid (Rubele et al 2015(Rubele et al , 2018El Youssoufi et al 2019b). Additionally, pulsating variable stars (young Cepheids and old RR Lyrae stars) trace an elongated structure of the SMC that extends more than 20 kpc along the line of sight (Jacyszyn-Dobrzeniecka et al 2016Ripepi et al 2017).…”