The build-up of pseudo-bulges in a hierarchical universe
Abstract
We study the cosmological build-up of pseudo-bulges using the L-Galaxies semi-analytical model for galaxy formation with a new approach for following separately the assembly of classical bulges and pseudo-bulges. Classical bulges are assumed to be the result of violent processes (i.e. mergers and starbursts), while the formation of pseudo-bulges is connected to the secular growth of discs. We apply the model to both the Millennium and the Millennium II simulations, in order to study our results across a wide range of stellar masses (107-10^{11.5} M_{⊙}). We find that z = 0 pseudo-bulges mainly reside in galaxies of M_stellar {∼ } 10^{10}-10^{10.5} M_{⊙} (M_halo {∼ } 10^{11.5}-10^{12} M_{⊙}) and we recover structural properties of these objects (e.g. sizes and bulge-to-total ratios) that are in good agreement with observational results. Tracing their formation history, we find that pseudo-bulges assembled in galaxies with a very quiet merger history, as opposed to the host galaxies of classical bulges. Regarding the bulge structure, we find that {∼ } 30{{ per cent}} of the galaxies with a predominant pseudo-bulge feature a composite structure, hosting both a pseudo- and a classical bulge component. The classical component typically constitutes {∼ } 10{{ per cent}} of the total bulge galaxy mass. When looking at the properties of the host galaxies, we find that z = 0 pseudo-bulges are hosted by main-sequence galaxies, characterized by a stellar population which is generally younger compared to the one of the hosts of classical bulges.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- September 2019
- DOI:
- 10.1093/mnras/stz1694
- arXiv:
- arXiv:1901.10490
- Bibcode:
- 2019MNRAS.488..609I
- Keywords:
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- methods: numerical;
- galaxies: evolution;
- galaxies: formation;
- galaxies: nuclei;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Submitted to MNRAS