The CALIFA view on stellar angular momentum across the Hubble sequence
We present the apparent stellar angular momentum over the optical extent of 300 galaxies across the Hubble sequence using integral-field spectroscopic (IFS) data from the CALIFA survey. Adopting the same λ parameter previously used to distinguish between slow and fast rotating early-type (elliptical and lenticular) galaxies, we show that spiral galaxies are almost all fast rotators, as expected. Given the extent of our data, we provide relations for λ measured in different apertures (e.g. fractions of the effective radius: 0.5 R, R, 2 R), including conversions to long-slit 1D apertures. Our sample displays a wide range of λ values, consistent with previous IFS studies. The fastest rotators are dominated by relatively massive and highly star-forming Sb galaxies, which preferentially reside in the main star-forming sequence. These galaxies reach λ values of ∼0.85, and they are the largest galaxies at a given mass, while also displaying some of the strongest stellar population gradients. Compared to the population of S0 galaxies, our findings suggest that fading may not be the dominant mechanism transforming spirals into lenticulars. Interestingly, we find that λ decreases for late-type Sc and Sd spiral galaxies, with values that occasionally set them in the slow-rotator regime. While for some of them this can be explained by their irregular morphologies and/or face-on configurations, others are edge-on systems with no signs of significant dust obscuration. The latter are typically at the low-mass end, but this does not explain their location in the classical (V/σ, ϵ) and (λ, ϵ) diagrams. Our initial investigations, based on dynamical models, suggest that these are dynamically hot disks, probably influenced by the observed important fraction of dark matter within R © ESO 2018. ; Funding and financial support acknowledgements: J. F.-B. from grant AYA2016-77237-C3-1-P from the Spanish Ministry of Economy and Competitiveness (MINECO); GvdV acknowledges funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme undergrant agreement no. 724857 (Consolidator Grant ArcheoDyn). B. G.-L. acknowledge support from the State Research Agency (AEI) of the Spanish Ministry of Science, Innovation and Universities (MCIU) and the European Regional Development Fund (FEDER) under grant with reference AYA2015-68217-P. SFS is grateful for the support of a CONA-CYT grant CB-285080 and FC-2016-01-1916, and funding from the PAPIIT-DGAPA-IA101217 (UNAM) project. L. Z. acknowledges support from Shanghai Astronomical Observatory, Chinese Academy of Sciences under grant no. Y895201009. L. G. was supported in part by the US National Science Foundation under Grant AST-1311862. RGD from AYA2016-77846-P, AYA2014-57490-P, AYA2010-15081, and Junta de Andalucí a FQ1580. IM from grants AYA2013-42227-P and AYA2016-76682-C3-1-P. RGB, RMGD, IM, and EP acknowledge financial support from the State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709).
