Header

UZH-Logo

Maintenance Infos

Pseudobulge formation as a dynamical rather than a secular process


Guedes, Javiera; Mayer, Lucio; Carollo, Marcella; Madau, Piero (2013). Pseudobulge formation as a dynamical rather than a secular process. Astrophysical Journal, 772(1):36.

Abstract

We investigate the formation and evolution of the pseudobulge in "Eris," a high-resolution N-body + smoothed particle hydrodynamic cosmological simulation that successfully reproduces a Milky-Way-like massive late-type spiral in an cold dark matter universe. At the present epoch, Eris has a virial mass M vir ~= 8 × 1011 M ⊙, a photometric stellar mass M * = 3.2 × 1010 M ⊙, a bulge-to-total ratio B/T = 0.26, and a weak nuclear bar. We find that the bulk of the pseudobulge forms quickly at high redshift via a combination of non-axisymmetric disk instabilities and tidal interactions or mergers, both occurring on dynamical timescales, not through slow secular processes at lower redshift. Its subsequent evolution is not strictly secular either, and is closely intertwined with the evolution of the stellar bar. In fact, the structure that we recognize as a pseudobulge today evolved from a stellar bar that formed at high redshift due to tidal interactions with satellites, was destroyed by minor mergers at z ~ 3, re-formed shortly after, and weakened again following a steady gas inflow at z <~ 1. The gradual dissolution of the bar ensued at z ~ 1 and continues until the present without increasing the stellar velocity dispersion in the inner regions. In this scenario, the pseudobulge is not a separate component from the inner disk in terms of formation path; rather, it is the first step in the inside-out formation of the baryonic disk, in agreement with the fact that pseudobulges of massive spiral galaxies typically have a dominant old stellar population. If our simulations do indeed reproduce the formation mechanisms of massive spirals, then the progenitors of late-type galaxies should have strong bars and small photometric pseudobulges at high redshift.

Abstract

We investigate the formation and evolution of the pseudobulge in "Eris," a high-resolution N-body + smoothed particle hydrodynamic cosmological simulation that successfully reproduces a Milky-Way-like massive late-type spiral in an cold dark matter universe. At the present epoch, Eris has a virial mass M vir ~= 8 × 1011 M ⊙, a photometric stellar mass M * = 3.2 × 1010 M ⊙, a bulge-to-total ratio B/T = 0.26, and a weak nuclear bar. We find that the bulk of the pseudobulge forms quickly at high redshift via a combination of non-axisymmetric disk instabilities and tidal interactions or mergers, both occurring on dynamical timescales, not through slow secular processes at lower redshift. Its subsequent evolution is not strictly secular either, and is closely intertwined with the evolution of the stellar bar. In fact, the structure that we recognize as a pseudobulge today evolved from a stellar bar that formed at high redshift due to tidal interactions with satellites, was destroyed by minor mergers at z ~ 3, re-formed shortly after, and weakened again following a steady gas inflow at z <~ 1. The gradual dissolution of the bar ensued at z ~ 1 and continues until the present without increasing the stellar velocity dispersion in the inner regions. In this scenario, the pseudobulge is not a separate component from the inner disk in terms of formation path; rather, it is the first step in the inside-out formation of the baryonic disk, in agreement with the fact that pseudobulges of massive spiral galaxies typically have a dominant old stellar population. If our simulations do indeed reproduce the formation mechanisms of massive spirals, then the progenitors of late-type galaxies should have strong bars and small photometric pseudobulges at high redshift.

Statistics

Citations

31 citations in Web of Science®
27 citations in Scopus®
Google Scholar™

Altmetrics

Downloads

23 downloads since deposited on 11 Feb 2014
5 downloads since 12 months
Detailed statistics

Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute for Computational Science
Dewey Decimal Classification:530 Physics
Language:English
Date:July 2013
Deposited On:11 Feb 2014 10:05
Last Modified:08 Dec 2017 03:11
Publisher:IOP Publishing
ISSN:0004-637X
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1088/0004-637X/772/1/36

Download

Download PDF  'Pseudobulge formation as a dynamical rather than a secular process'.
Preview
Content: Accepted Version
Filetype: PDF
Size: 2MB
View at publisher