SDSS-IV MaNGA: The intrinsic shape of slow rotator early-type galaxies

Abstract

By inverting the distributions of galaxies' apparent ellipticities and misalignment angles (measured around the projected half-light radius $R_{\mathrm{e}}$) between their photometric and kinematic axes, we study the intrinsic shape distribution of 189 slow rotator early-type galaxies with stellar masses $2\times 10^{11}{M}_{\odot }<M_{\ast }<2\times 10^{12}{M}_{\odot }$, extracted from a sample of about 2200 galaxies with integral-field stellar kinematics from the DR14 of the SDSS-IV MaNGA IFU survey. Thanks to the large sample of slow rotators, Graham+18 showed that there is clear structure in the misalignment angle distribution, with two peaks at both $0^{\circ }$ and $90^{\circ }$ misalignment (characteristic of oblate and prolate rotation respectively). Here we invert the observed distribution from Graham+18. The large sample allows us to go beyond the known fact that slow rotators are weakly triaxial and to place useful constraints on their intrinsic triaxiality distribution (around $1R_{\mathrm{e}}$) for the first time. The shape inversion is generally non-unique. However, we find that, for a wide set of model assumptions, the observed distribution clearly requires a dominant triaxial-oblate population. For some of our models, the data suggest a hint for a minor triaxial-prolate population, but a dominant prolate population is ruled out.

arXiv commentAccepted for publication in ApJL, 10 pages, 4 figures, 1 table

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• The diverse nature and formation paths of slow rotator galaxies in the EAGLE simulations
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• TDCOSMO 2025: Cosmological constraints from strong lensing time delays
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• Shapes of Milky-Way-Mass Galaxies with Self-Interacting Dark Matter
• Prospects for Recovering Galaxy Intrinsic Shapes from Projected Quantities
• Merger histories of brightest group galaxies from MUSE stellar kinematics
• Mapping Accreted Stars in Early-Type Galaxies Across the Mass-Size Plane
• Dynamical masses of brightest cluster galaxies I: stellar velocity anisotropy and mass-to-light ratios
• Intrinsic shapes of Brightest Cluster Galaxies
• Early-Type Galaxies: Elliptical and S0 Galaxies, or Fast and Slow Rotators
• Radio AGN jet alignment: Radio and Optical Position Angle of Radio Galaxies
• On the kinematic nature of apparent discs at high redshifts: Local counterparts are not dominated by ordered rotation but by tangentially anisotropic random motion
• Reorientation Rates of Structural and Kinematic Axes in Simulated Massive Galaxies and the Origins of Prolate Rotation
• The Outskirt Stellar Mass of Low-Redshift Massive Galaxies is an Excellent Halo Mass Proxy in Illustris/IllustrisTNG Simulations
• Photometric and Kinematic Misalignments and Their Evolution Among Fast and Slow Rotators in the Illustris Simulation
• Galaxy 3D Shape Recovery using Mixture Density Network
• The intricate link between galaxy dynamics and intrinsic shape (or why so-called prolate rotation is a misnomer)