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arXiv · 2303.06132

The extended Planetary Nebula Spectrograph (ePN.S) early-type galaxy survey: The specific angular momentum of ETGs

C. Pulsoni·O. Gerhard·S. M. Fall·M. Arnaboldi·A. I. Ennis·J. Hartke·L. Coccato·N. R. Napolitano
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Abstract

Mass and angular momentum are key parameters of galaxies. Their co-evolution establishes an empirical relation between the specific stellar angular momentum j* and the stellar mass M* that depends on morphology. In this work, we measure j* in a sample of 32 early type galaxies (ETGs) from the ePN.S survey, using full 2D kinematic information out to a mean 6Re. We present lambda and j* profiles. We derive the distribution of these galaxies on the total j*-M* plane and determine the ratio between the stellar j* and the specific angular momentum of the host dark matter halo. The radially extended, 2D kinematic data show that the stellar halos of ETGs do not contain large stellar mass fractions of high j*. The j*-profiles of fast-rotator ETGs are largely converged within the range of the data. For slow rotators, j* is still rising and is estimated to increase beyond 6Re by up to 40%. More than 60% of their halo angular momentum is in misaligned rotation. We find that the ePN.S ETG sample displays the well-known correlation between j*, M*, and morphology: elliptical galaxies have systematically lower j* than similar mass S0 galaxies. However, fast and slow rotators lie on the same relation within errors with the slow rotators falling at the high M* end. A power-law fit to the j*-M* relation gives a slope of 0.55+-0.17 for the S0s and 0.76+-0.23 for the ellipticals, with normalisation about 4 and 9 times lower than spirals, respectively. The estimated retained fraction of angular momentum at 10^10-10^10.5 Msun is 25% for S0s and >10% for ellipticals, and decreases by 1.5 orders of magnitude at M*~10^12 Msun. Our results show that ETGs have substantially lower j* than spiral galaxies with similar M*. Their j* must be lost during their evolution, and/or retained in the hot gas component and the satellite galaxies that have not yet merged with the central galaxy. [abridged]

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C. Pulsoni, O. Gerhard, S. M. Fall, M. Arnaboldi, A. I. Ennis, J. Hartke, L. Coccato, N. R. Napolitano. 2023-03-10. The extended Planetary Nebula Spectrograph (ePN.S) early-type galaxy survey: The specific angular momentum of ETGs. https://doi.org/10.1051/0004-6361/202346234

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