The stellar orbit distribution in present-day galaxies inferred from the CALIFA survey

DOI: 
10.1038/s41550-017-0348-1
Publication date: 
01/03/2018
Main author: 
Zhu, Ling
IAA authors: 
García-Benito, Rubén
Authors: 
Zhu, Ling;van de Ven, Glenn;Bosch, Remco van den;Rix, Hans-Walter;Lyubenova, Mariya;Falcón-Barroso, Jesús;Martig, Marie;Mao, Shude;Xu, Dandan;Jin, Yunpeng;Obreja, Aura;Grand, Robert J. J.;Dutton, Aaron A.;Macciò, Andrea V.;Gómez, Facundo A.;Walcher, Jakob C.;García-Benito, Rubén;Zibetti, Stefano;Sánchez, Sebastian F.
Journal: 
Nature Astronomy
Refereed: 
Yes
Publication type: 
Article
Volume: 
2
Pages: 
233-238
Abstract: 
Galaxy formation entails the hierarchical assembly of mass, along with the condensation of baryons and the ensuing, self-regulating star formation<SUP>1,2</SUP>. The stars form a collisionless system whose orbit distribution retains dynamical memory that can constrain a galaxy's formation history<SUP>3</SUP>. The orbits dominated by ordered rotation, with near-maximum circularity λ<SUB>z</SUB> ≈ 1, are called kinematically cold, and the orbits dominated by random motion, with low circularity λ<SUB>z</SUB> ≈ 0, are kinematically hot. The fraction of stars on `cold' orbits, compared with the fraction on `hot' orbits, speaks directly to the quiescence or violence of the galaxies' formation histories<SUP>4,5</SUP>. Here we present such orbit distributions, derived from stellar kinematic maps through orbit-based modelling for a well-defined, large sample of 300 nearby galaxies. The sample, drawn from the CALIFA survey<SUP>6</SUP>, includes the main morphological galaxy types and spans a total stellar mass range from 10<SUP>8.7</SUP> to 10<SUP>11.9</SUP> solar masses. Our analysis derives the orbit-circularity distribution as a function of galaxy mass and its volume-averaged total distribution. We find that across most of the considered mass range and across morphological types, there are more stars on `warm' orbits defined as 0.25 ≤ λ<SUB>z</SUB> ≤ 0.8 than on either `cold' or `hot' orbits. This orbit-based `Hubble diagram' provides a benchmark for galaxy formation simulations in a cosmological context.
Database: 
ADS
SCOPUS
URL: 
https://ui.adsabs.harvard.edu/#abs/2018NatAs...2..233Z/abstract
ADS Bibcode: 
2018NatAs...2..233Z
Keywords: 
Astrophysics - Astrophysics of Galaxies