Morphological decomposition of TNG50 galaxies: methodology and catalogue

• Published in: Monthly notices of the Royal Astronomical Society 2022-07, Vol.515 (1), p.1524-1543
• Main Authors: Zana, Tommaso, Lupi, Alessandro, Bonetti, Matteo, Dotti, Massimo, Rosas-Guevara, Yetli, Izquierdo-Villalba, David, Bonoli, Silvia, Hernquist, Lars, Nelson, Dylan
• Format: Article
• Language: English
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stac1708

We present mordor (MORphological DecOmposeR), a new algorithm for structural decomposition of simulated galaxies based on stellar kinematics. The code measures the properties of up to five structural components (a thin/cold and a thick/warm disc, a classical and a secular bulge, and a spherical stellar halo), and determines the properties of a stellar bar (if present). A comparison with other algorithms presented in the literature yields overall good agreement, with mordor displaying a higher flexibility in correctly decomposing systems and identifying bars in crowded environments (e.g. with ongoing fly-bys, often observable in cosmological simulations). We use mordor to analyse galaxies in the TNG50 simulation and find the following: (i) the thick disc component undergoes the strongest evolution in the binding energy-circularity plane, as expected when disc galaxies decrease their turbulent-rotational support with cosmic time; (ii) smaller galaxies (with stellar mass, $10^{9} \lesssim M_{*}/~\rm M_{\odot }\le 5 \times 10^{9}$) undergo a major growth in their disc components after z ∼ 1, whereas (iii) the most massive galaxies ($5 \times 10^{10} \lt M_{*}/~\rm M_{\odot }\le 5\times 10^{11}$) evolve towards more spheroidal dominated objects down to z = 0 due to frequent gravitational interactions with satellites; (iv) the fraction of barred galaxies grows rapidly at high redshift and stabilizes below z ∼ 2, except for the most massive galaxies that show a decrease in the bar occupation fraction at low redshift; (v) galaxies with $M_{*} \sim 10^{11}~~\rm M_{\odot }$ exhibit the highest relative occurrence of bars at z = 0, in agreement with observational studies. We publicly release mordor and the morphological catalogue of TNG50 galaxies.