Insights into the Galactic Bulge Chemodynamical Properties from Gaia Data Release 3
Abstract We explore the chemodynamical properties of the Galaxy in the azimuthal velocity V ϕ and metallicity [Fe/H] space using red giant stars from Gaia Data Release 3. The row-normalized V ϕ –[Fe/H] maps form a coherent sequence from the bulge to the outer disk, clearly revealing the thin/thick d...
Saved in:
Published in | The Astrophysical journal Vol. 967; no. 1; pp. 5 - 19 |
---|---|
Main Authors | , , , , , , |
Format | Journal Article |
Language | English |
Published |
Philadelphia
The American Astronomical Society
01.05.2024
IOP Publishing |
Subjects | |
Online Access | Get full text |
Cover
Loading…
Summary: | Abstract
We explore the chemodynamical properties of the Galaxy in the azimuthal velocity
V
ϕ
and metallicity [Fe/H] space using red giant stars from Gaia Data Release 3. The row-normalized
V
ϕ
–[Fe/H] maps form a coherent sequence from the bulge to the outer disk, clearly revealing the thin/thick disk and the Splash. The metal-rich stars display bar-like kinematics, while the metal-poor stars show dispersion-dominated kinematics. The intermediate-metallicity population (−1 < [Fe/H]< − 0.4) can be separated into two populations, one that is bar-like, i.e., dynamically cold (
σ
V
R
∼
80
km s
−1
) and fast-rotating (
V
ϕ
≳ 100 km s
−1
), and the Splash, which is dynamically hot (
σ
V
R
∼
110
km s
−1
) and slow-rotating (
V
ϕ
≲ 100 km s
−1
). We compare the observations in the bulge region with an Auriga simulation where the last major merger event occurred ∼10 Gyr ago: only stars born around the time of the merger reveal a Splash-like feature in the
V
ϕ
–[Fe/H] space, suggesting that the Splash is likely merger-induced, predominantly made up of heated disk stars and the starburst associated with the last major merger. Since the Splash formed from the proto-disk, its lower metallicity limit coincides with that of the thick disk. The bar formed later from the dynamically hot disk with [Fe/H] > − 1 dex, with the Splash not participating in the bar formation and growth. Moreover, with a set of isolated evolving
N
-body disk simulations, we confirm that a nonrotating classical bulge can be spun up by the bar and develop cylindrical rotation, consistent with the observations for the metal-poor stars. |
---|---|
Bibliography: | AAS52575 Interstellar Matter and the Local Universe |
ISSN: | 0004-637X 1538-4357 |
DOI: | 10.3847/1538-4357/ad38ba |