The diverse physical origins of stars in the dynamically hot bulge: CALIFA vs. IllustrisTNG

Abstract

We compare the internal stellar structures of central galaxies in the TNG50 and TNG100 simulations and field galaxies in the CALIFA survey. The luminosity fractions of the dynamically cold, warm, and hot components in both TNG50 and TNG100 galaxies exhibit general consistency with those observed in CALIFA galaxies. For example, they all exhibit a minimum luminosity fraction of the dynamically hot component in galaxies with intermediate stellar masses, and the morphology of each orbital component in the TNG50 and TNG100 galaxies closely resembles that found in the CALIFA galaxies. We therefore use the simulations to quantify the physical origins of the different components, focusing on the dynamically hot component in TNG50. We identify three primary regimes and thus physical processes: (1) in low mass galaxies that have not experienced major mergers, stars are born with a wide range of circularity distributions and have remained relatively unchanged until the present day. Consequently, hot stars in such galaxies at redshift 0 are predominantly born hot. (2) In higher mass galaxies lacking major mergers, most stars are initially born cold but are subsequently heated through secular evolution. (3) In galaxies across the entire mass range, mergers, if they occurred, significantly increased the hot orbital fraction. As a result, the dynamically hot bulge within $R_e$ of present-day galaxies does not indicate their past merger histories; instead, the hot stars in the outer regions are mostly heated or accreted by mergers, thus indicating galaxy merger history. The massive galaxies are initially born with cold, rotationally supported structures, consistent with recent observations from the James Webb Space Telescope (JWST) regarding high-redshift galaxies.

18 pages, 15 figures

References in corpus (41)

• Overview of the SDSS-IV MaNGA Survey: Mapping Nearby Galaxies at Apache Point Observatory
• Simulating galaxy formation with black hole driven thermal and kinetic feedback
• Bulge Formation by the Coalescence of Giant Clumps in Primordial Disk Galaxies
• Triaxial orbit based galaxy models with an application to the (apparent) decoupled core galaxy NGC 4365
• The Size Evolution of Star-forming and Quenched Galaxies in the IllustrisTNG simulation
• Thin, thick and dark discs in LCDM
• CALIFA: a diameter-selected sample for an integral field spectroscopy galaxy survey
• Stellar kinematics across the Hubble sequence in the CALIFA survey: General properties and aperture corrections
• Chemodynamics of barred galaxies in cosmological simulations: On the Milky Way's quiescent merger history and in-situ bulge
• CEERS Key Paper III: The Diversity of Galaxy Structure and Morphology at z=3-9 with JWST
• Age velocity dispersion relations and heating histories in disc galaxies
• Orbital decomposition of CALIFA spiral galaxies
• Spatially Resolved Star Formation and Inside-out Quenching in the TNG50 Simulation and 3D-HST Observations
• First Look at z > 1 Bars in the Rest-Frame Near-Infrared with JWST Early CEERS Imaging
• Fast galaxy bars continue to challenge standard cosmology
• The bursty origin of the Milky Way thick disc
• A JWST investigation into the bar fraction at redshifts 1 < z < 3
• The relationship between fine galaxy stellar morphology and star formation activity in cosmological simulations: a deep learning view
• Wet Compaction to a Blue Nugget: a Critical Phase in Galaxy Evolution
• The stellar halos of ETGs in the IllustrisTNG simulations: the photometric and kinematic diversity of galaxies at large radii
• Barred Galaxies in the IllustrisTNG Simulation
• The merger and assembly histories of Milky Way- and M31-like galaxies with TNG50: disk survival through mergers
• Born this way: thin disc, thick disc, and isotropic spheroid formation in FIRE-2 Milky-Way-mass galaxy simulations
• The stellar halos of ETGs in the IllustrisTNG simulations: II. Accretion, merger history, and dark halo connection
• The SAMI Galaxy Survey: The internal orbital structure and mass distribution of passive galaxies from triaxial orbit-superposition Schwarzschild models
• Kinematic decomposition of IllustrisTNG disk galaxies: morphology and relation with morphological structures
• Identifying kinematic structures in simulated galaxies using unsupervised machine learning
• The Fornax3D project: Assembly histories of lenticular galaxies from a combined dynamical and population orbital analysis
• Mass of the dynamically hot inner stellar halo predicts the ancient accreted stellar mass
• Dissecting galactic bulges in space and time I: the importance of early formation scenarios vs. secular evolution
• Simulated Bars May Be Shorter But Are Not Slower Than Observed: TNG50 vs. MaNGA
• The Evolutionary Pathways of Disk-, Bulge-, and Halo-dominated Galaxies
• The Fornax3D project: discovery of ancient massive merger events in the Fornax cluster galaxies NGC 1380 and NGC 1427
• The evolution of barred galaxies in the EAGLE simulations
• On the robustness of triaxial Schwarzschild modelling: The effects of correcting the orbit mirroring
• Orbit-Superposition Dynamical Modeling of Barred Galaxies
• The Fornax3D project: Environmental effects on the assembly of dynamically cold disks in Fornax cluster galaxies
• A New Channel of Bulge Formation via The Destruction of Short Bars
• The Structural Evolution of Isolated Galaxies at Low Redshift in the IllustrisTNG Simulation
• IllustrisTNG Insights: Factors Affecting the Presence of Bars in Disk Galaxies
• Orthogonal vertical velocity dispersion distributions produced by bars

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• The effects of the orbital configurations of mergers on reshaping galaxy structures
• Distinguishing the formation paths of massive compact ETGs through their internal dynamical structures
• The spatially-resolved effect of mergers on the stellar mass assembly of MaNGA galaxies
• Orbit-based structural decomposition and stellar population recovery for edge-on barred galaxies