Mapping Accreted Stars in Early-Type Galaxies Across the Mass-Size Plane

Davison, Thomas, Norris, Mark orcid iconORCID: 0000-0002-7001-805X, Leaman, Ryan, Kuntschner, Harald, Boecker, Alina and van de Ven, Glenn (2021) Mapping Accreted Stars in Early-Type Galaxies Across the Mass-Size Plane. Monthly Notices of the Royal Astronomical Society, 507 (2). pp. 3089-3112. ISSN 0035-8711

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Abstract Galaxy mergers are instrumental in dictating the final mass, structure, stellar populations, and kinematics of galaxies. Cosmological galaxy simulations indicate that the most massive galaxies at z=0 are dominated by high fractions of ‘ex-situ’ stars, which formed first in distinct independent galaxies, and then subsequently merged into the host galaxy. Using spatially resolved MUSE spectroscopy we quantify and map the ex-situ stars in thirteen massive Early Type galaxies. We use full spectral fitting together with semi-analytic galaxy evolution models to isolate the signatures in the galaxies’ light which are indicative of ex-situ populations. Using the large MUSE field of view we find that all galaxies display an increase in ex-situ fraction with radius, with massive and more extended galaxies showing a more rapid increase in radial ex-situ fraction, (reaching values between ∼30% to 100% at 2 effective radii) compared to less massive and more compact sources (reaching between ∼5% to 40% ex-situ fraction within the same radius). These results are in line with predictions from theory and simulations which suggest ex-situ fractions should increase significantly with radius at fixed mass for the most massive galaxies.

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