Dissecting the 3D chemo-dynamical structures of NGC 1381: a galaxy hosting an ancient slow bar with an accreted bulge and thick disc

Autor(en)

Yunpeng Jin, Ling Zhu, Shude Mao, Marie Martig, Francesca Pinna, Glenn van de Ven, Yuchen Ding

Abstrakt

We applied the barred population-orbit superposition method developed in \citet{Jin2025a,Jin2025b} to construct 3D chemo-dynamical models for the barred S0 galaxy NGC~1381 in the Fornax cluster. Based on the stellar orbits in the models, we decomposed NGC~1381 into six components: (1) a dynamically warm nuclear disc with $f_{\rm nucl}\sim5\%$; (2) a rigidly rotating, BP/X-shaped bar with $f_{\rm bar}\sim30\%$; (3) a dynamically hot, spheroidal bulge with $f_{\rm bulge}\sim17\%$; (4) a dynamically cold thin disc with $f_{\rm thin}\sim28\%$; (5) a vertically extended thick disc with $f_{\rm thick}\sim16\%$; and (6) a dynamically hot, spatially diffuse stellar halo with $f_{\rm halo}\sim5\%$. The nuclear disc, bar, and thin disc are metal-rich ($[Z/\rm H]\gtrsim0$), $α$-poor ($\rm[Mg/Fe]\lesssim0.2$), and old ($\sim13\rm\,Gyr$), corresponding to in situ formation in the early Universe. The bulge, thick disc, and stellar halo are metal-poor ($[Z/\rm H]\lesssim0$), $α$-rich ($\rm[Mg/Fe]\gtrsim0.2$), and younger than or comparable in age to the in situ components, suggesting their relations with ex situ formation contributed by minor mergers. The flat metallicity and [Mg/Fe] gradients in the thick disc and stellar halo indicate they are dominated by a similar population of ex situ stars. In contrast, the bulge exhibits a negative metallicity gradient ($\nabla[Z/\rm H]_{bulge}

Organisation(en)

Institut für Astrophysik

Journal

Astronomy & Astrophysics

ISSN

0004-6361

Publikationsdatum

07-2026

Peer-reviewed

Ja

ÖFOS 2012

103003 Astronomie, 103004 Astrophysik

Schlagwörter

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/d0a4e3e4-7aeb-4547-9c75-b15270878087