TY - JOUR
T1 - Introducing galactic structure finder
T2 - The multiple stellar kinematic structures of a simulated Milky Way mass galaxy
AU - Obreja, Aura
AU - Macciò, Andrea V.
AU - Moster, Benjamin
AU - Dutton, Aaron A.
AU - Buck, Tobias
AU - Stinson, Gregory S.
AU - Wang, Liang
N1 - Funding Information:
Interestingly, the three components supported by random motions in both face-on and edge-on perspective, namely the classical and pseudo bulges and the stellar halo, show purely exponential profiles. Though this is expected of structures like low mass spheroidal galaxies (Graham & Guzmán 2003; Koda et al. 2015; van Dokkum et al. 2015) or pseudo bulges (Fisher & Drory 2008; Gadotti 2009), it is not generally expected of classical bulges, which are thought to have S’ indices nS ≥ 2. However, other authors, for example Andredakis & Sanders (1994) or Andredakis, Peletier & Balcells (1995), have argued that bulges cover a continuous range in profiles from purely exponential to highly centrally concentrated ones.
Funding Information:
We would like to thank the anonymous referee for a constructive report, which helped improve the quality of this manuscript. We would also like to thank Glenn van de Ven, Fabrizio Arrigoni Battaia, Rosa Domínguez Tenreiro, and Chris Brook for useful conversations. All figures in thiswork have been made with matplotlib (Hunter 2007). The gsf code also uses the Python libraries numpy (Walt, Colbert & Varoquaux 2011) and scipy (Eric Jones et al. 2001<?aptara-node a1863#*?>). F2PY (Peterson 2009) has been used to compile the Fortran module for Python. This research was carried out on the High Performance Computing resources at New York University Abu Dhabi; on the THEO cluster of the Max-Planck-Institut für Astronomie and on the HYDRA clusters at the Rechenzentrum in Garching. We greatly appreciate the contributions of these computing allocations. AO and BM have been funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)-MO2979/1-1. TB acknowledges support from the Sonder for schungs bereich SFB 881 'The Milky Way System' (subproject A1) of the DFG.
PY - 2018/7/1
Y1 - 2018/7/1
N2 - We present the first results of applying Gaussian MixtureModels in the stellar kinematic space of normalized angular momentum and binding energy on NIHAO high-resolution galaxies to separate the stars into multiple components. We exemplify this method, using a simulated MilkyWay analogue, whose stellar component hosts thin and thick discs, classical and pseudo bulges, and a stellar halo. The properties of these stellar structures are in good agreement with observational expectations in terms of sizes, shapes, and rotational support. Interestingly, the two kinematic discs show surface mass density profiles more centrally concentrated than exponentials, while the bulges and the stellar halo are purely exponential. We trace back in time the Lagrangian mass of each component separately to study their formation history. Between z ~ 3 and the end of halo virialization, z ~ 1.3, all components lose a fraction of their angular momentum. The classical bulge loses the most (~95 per cent) and the thin disc the least (~60 per cent). Both bulges formed their stars in situ at high redshift, while the thin disc formed ~98 per cent in situ, but with a constant SFR ~ 1.5M⊙ yr-1 over the last ~11 Gyr. Accreted stars (6 per cent of total stellar mass) are mainly incorporated to the thick disc or the stellar halo, which formed ex situ 8 per cent and 45 per cent of their respective masses. Our analysis pipeline is freely available at https://github.com/aobr/gsf.
AB - We present the first results of applying Gaussian MixtureModels in the stellar kinematic space of normalized angular momentum and binding energy on NIHAO high-resolution galaxies to separate the stars into multiple components. We exemplify this method, using a simulated MilkyWay analogue, whose stellar component hosts thin and thick discs, classical and pseudo bulges, and a stellar halo. The properties of these stellar structures are in good agreement with observational expectations in terms of sizes, shapes, and rotational support. Interestingly, the two kinematic discs show surface mass density profiles more centrally concentrated than exponentials, while the bulges and the stellar halo are purely exponential. We trace back in time the Lagrangian mass of each component separately to study their formation history. Between z ~ 3 and the end of halo virialization, z ~ 1.3, all components lose a fraction of their angular momentum. The classical bulge loses the most (~95 per cent) and the thin disc the least (~60 per cent). Both bulges formed their stars in situ at high redshift, while the thin disc formed ~98 per cent in situ, but with a constant SFR ~ 1.5M⊙ yr-1 over the last ~11 Gyr. Accreted stars (6 per cent of total stellar mass) are mainly incorporated to the thick disc or the stellar halo, which formed ex situ 8 per cent and 45 per cent of their respective masses. Our analysis pipeline is freely available at https://github.com/aobr/gsf.
KW - Galaxies: fundamental parameters
KW - Galaxies: kinematics and dynamics
KW - Galaxies: stellar content -methods: numerical
KW - Galaxies: structure
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U2 - 10.1093/MNRAS/STY1022
DO - 10.1093/MNRAS/STY1022
M3 - Article
AN - SCOPUS:85051565454
VL - 477
SP - 4915
EP - 4930
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 4
ER -