Óscar Jiménez-Arranz - Large and Small Magellanic Cloud images using Gaia DR3 data

Large and Small Magellanic Cloud images using Gaia DR3 data

This collection of images shows different views of the Large and Small Magellanic Cloud (LMC and SMC, respectively) using Gaia's astrometric and photometric information from the mission’s Data Release 3 (DR3). These views are not a photographs since has been compiled by mapping the total amount of radiation detected by Gaia in each pixel, combined with measurements of the radiation taken through different filters on the spacecraft to generate color information. We used the same approach as for the already well-known Gaia sky map and other LMC and SMC images that made use of Gaia data.

To establish a foundational point of reference, we start by presenting the Gaia DR3 base samples for LMC and SMC, acknowledging that these initial representations still incorporate Milky Way (MW) foreground contamination:

Figure 1. Representation of the LMC (left) and SMC (right) using astrometric and photometric information from the Gaia Data Release 3. These views are not a photographs since has been compiled by mapping the total amount of radiation detected by Gaia in each pixel, combined with measurements of the radiation taken through different filters on the spacecraft to generate color information. Note that these images have been processed using the 'base samples', which still have MW foreground contamination (see, for example, the two MW's globular clusters Tuc 47 and NGC362 in the field-of-view of the SMC). Both images are not in scale.

Figure 2. Representation of the Magellanic Clouds using astrometric and photometric information from the Gaia Data Release 3. These views are not a photographs since has been compiled by mapping the total amount of radiation detected by Gaia in each pixel, combined with measurements of the radiation taken through different filters on the spacecraft to generate color information. Note that these images have been processed using the 'base samples', which still have MW foreground contamination (see, for example, the two MW globular clusters Tuc 47 and NGC362 in the field-of-view of the SMC). Scale is maintained in the image.

Obtaining LMC and SMC clean samples for the Gaia Data Release 3 has taken up a portion of my work so that we can remove the MW contaminants. However, the choice about the purity-completeness trade-off of the samples will determine their characteristics and may, therefore, have an impact on the results. Thus, we defined three samples with different levels of completeness and purity: the complete, the optimal and the truncated-optimal (more information here). Here we visually compare the different samples:

Figure 3. The LMC (top) and SMC (bottom) as viewed by the Gaia satellite using astrometric and photometric information from the mission’s Data Release 3. Each column show a different samplea. First column: Base sample (with MW contamination). Second column: Complete NN classification. Third column: Optimal NN classification. Fourth column: Truncated-optimal NN classification. Scale is maintained in the image.

If we focus on the NN Complete samples we can see plenty of details in both galaxies. Notice how the two MW globular clusters Tuc 47 and NGC362 in the field-of-view of the SMC present in Fig. 1 right panel have disappeared.

Figure 4. Same as in Fig. 1, but for the NN complete sample where the MW foreground contamination has been removed.

Figure 5. Same as in Fig. 2, but for the NN complete samples where the MW foreground contamination has been removed.

We see an overdensity of stars in the left part of the SMC moving toward the LMC. That is the Magellanic Bridge, a stellar (and gaseous) structure in the region between the two MCs created in their most recent near encounter, which took place between 150 and 200 Myr ago at a distance of less than 10 kpc. The majority of stars that conform the Bridge are young and scarce. Thus, we can select and highlight the Young1 and Young2 populations of the MCs reported in Gaia Collaboration, X. Luri et al. 2021b, to observe the Bridge in greater detail:

Figure 6. Same as in Fig. 5, but highlighting the Young1 and Young2 populations of the MCs reported in Gaia Collaboration, X. Luri et al. 2021b in the area where the Magellanic Bridge lies (red polygon).

Finally, zooming in on the inner region of the LMC, specifically the bar structure, reveals a remarkable level of detail and complexity. The Gaia data unveils a plethora of substructures within this galactic feature, such as clusters of stars, dust lanes, or other features that contribute to the overall morphology of the galaxy:

Figure 7. Same as Fig. 4 left panel with a zoom in the inner region of the galaxy, namely, the galactic bar.

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