English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The center of our disk galaxy, the Milky Way, is dominated by aboxy/peanut-shaped bulge. Numerous studies of the bulge based on stellarphotometry have concluded that the bulge stars are exclusively old. Theperceived lack of young stars in the bulge strongly constrains its likelyformation scenarios, providing evidence that the bulge is a unique populationthat formed early and separately from the disk. However, recent studies ofindividual bulge stars using the microlensing technique have reported that theyspan a range of ages, emphasizing that the bulge may not be a monolithicstructure. In this letter we demonstrate that the presence of young stars thatare located predominantly near the plane is expected for a bulge that hasformed from the disk via dynamical instabilities. Using an N-body+SPHsimulation of a disk galaxy forming out of gas cooling inside a dark matterhalo and forming stars, we find a qualitative agreement between our model andthe observations of young metal-rich stars in the bulge. We are also able topartially resolve the apparent contradiction in the literature between resultsthat argue for a purely old bulge population and those which show a populationcomprised of a range in ages; the key is where to look.

Young stars in an old bulge: a natural outcome of internal evolution in the Milky Way