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Inferring the Morphology of Stellar Distribution in TNG50: Twisted and Twisted-stretched Shapes

Emami, Razieh and Hernquist, Lars and Alcock, Charles and Genel, Shy and Bose, Sownak and Weinberger, Rainer and Vogelsberger, Mark and Shen, Xuejian and Speagle, Joshua S. and Marinacci, Federico and Forbes, John C. and Torrey, Paul (2021) Inferring the Morphology of Stellar Distribution in TNG50: Twisted and Twisted-stretched Shapes. Astrophysical Journal, 918 (1). Art. No. 7. ISSN 0004-637X. doi:10.3847/1538-4357/ac088b.

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We investigate the morphology of the stellar distribution (SD) in a sample of Milky Way–like galaxies in the TNG50 simulation. Using a local in shell iterative method as the main approach, we explicitly show evidence of twisting (in about 52% of halos) and stretching (in 48% of them) in real space. This is matched with the reorientation observed in the eigenvectors of the inertia tensor and gives us a clear picture of having a reoriented SD. We make a comparison between the shape profile of the dark matter (DM) halo and SD and quite remarkably see that their radial profiles are fairly close, especially at small galactocentric radii, where the stellar disk is located. This implies that the DM halo is somewhat aligned with stars in response to the baryonic potential. The level of alignment mostly decreases away from the center. We study the impact of substructures in the orbital circularity parameter. It is demonstrated that in some cases, faraway substructures are counterrotating compared with the central stars and may flip the sign of total angular momentum and thus the orbital circularity parameter. Truncating them above 150 kpc, however, retains the disky structure of the galaxy as per initial selection. Including the impact of substructures in the shape of stars, we explicitly show that their contribution is subdominant. Overlaying our theoretical results on the observational constraints from previous literature, we establish fair agreement.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper ItemIllustrisTNG simulations
Emami, Razieh0000-0002-2791-5011
Hernquist, Lars0000-0001-6950-1629
Genel, Shy0000-0002-3185-1540
Bose, Sownak0000-0002-0974-5266
Weinberger, Rainer0000-0001-6260-9709
Vogelsberger, Mark0000-0001-8593-7692
Shen, Xuejian0000-0002-6196-823X
Speagle, Joshua S.0000-0003-2573-9832
Marinacci, Federico0000-0003-3816-7028
Forbes, John C.0000-0002-1975-4449
Torrey, Paul0000-0002-5653-0786
Alternate Title:Stellar Halo Morphology from TNG50: Twisted and Twisted-Stretched Halos
Additional Information:© 2021. The American Astronomical Society. Received 2021 January 20; revised 2021 May 26; accepted 2021 June 4; published 2021 August 27. We warmly acknowledge the very insightful conversations with Sirio Belli, Charlie Conroy, Daniel Eisenstein, Rohan Naidu, Dylan Nelson, Sandro Tacchella, and Annalisa Pillepich. We also acknowledge the referee for the constructive comments that improved the quality and presentation of this manuscript. R.E. is thankful for support by the Institute for Theory and Computation (ITC) at the Center for Astrophysics (CFA). We are also thankful for the supercomputer facilities at Harvard University, where most of the simulation work was done. M.V. acknowledges support through an MIT RSC award, a Kavli Research Investment Fund, NASA ATP grant NNX17AG29G, and NSF grants AST-1814053, AST-1814259, and AST-1909831. S.B. is supported by Harvard University through the ITC Fellowship. F.M. acknowledges support through the Program "Rita Levi Montalcini" of the Italian MIUR. The TNG50 simulation was realized with computer time granted by the Gauss Centre for Supercomputing (GCS) under the GCS Large-Scale Projects GCS-DWAR on the GCS share of the supercomputer Hazel Hen at HLRS. Software: h5py (de Buyl et al. 2016), matplotlib (Hunter 2007), numpy (Van der Walt et al. 2011), pandas (McKinney et al. 2010), seaborn (Waskom et al. 2020), scipy (Oliphant 2007). Data Availability. The data that are directly related to this publication and its figures are available on reasonable request from the corresponding author. The IllustrisTNG simulations themselves are publicly available at (Nelson et al. 2019). The TNG50 simulation will be made public in the future as well.
Funding AgencyGrant Number
Harvard UniversityUNSPECIFIED
Massachusetts Institute of Technology (MIT)UNSPECIFIED
Kavli FoundationUNSPECIFIED
Ministero dell'Istruzione, dell'Università e della Ricerca (MIUR)UNSPECIFIED
Subject Keywords:Galaxy classification systems; Milky Way stellar halo; Hydrodynamical simulations
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Galaxy classification systems (582); Milky Way stellar halo (1060); Hydrodynamical simulations (767)
Record Number:CaltechAUTHORS:20210914-225402650
Persistent URL:
Official Citation:Razieh Emami et al 2021 ApJ 918 7
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:110895
Deposited By: George Porter
Deposited On:16 Sep 2021 21:32
Last Modified:16 Sep 2021 21:32

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