Detalles de publicación
PP 026037
Revisiting the Milky Way stellar long bar and the 3 kpc arm
(1) IAC; (2) ULL; (3) Institute of Astronomy and Physics, Inner Mongolia University, Hohhot, China; (4) NAOC-CAS, Beijing, China; (5) Local Universe and Time-Domain Astronomy Laboratory, China West Normal University, Nanchong, China; (6) Luoxiahong Institute of Astronomy, China West Normal University, Nanchong, China; (7) Dep. of Astronomy, China West Normal University, Nanchong, China
CONTEXT. One of the most difficult and unexplored regions of the Milky Way is the highly extincted in-plane central region within the Galactic coordinates 10 deg.≲|ℓ|≲30 deg., |b|≲3 deg., where we have the long-bar and 3 kpc arm with intermediate-age stellar population, whose morphological properties are still unclear.
AIMS. We aim to advance our knowledge of the morphology of these two components.
METHODS. We examined star counts of bright M giants in WISE-4.6μm and its distribution of distances derived from spectroscopic parallaxes with APOGEE-DR17. We also examined the distribution of distances of young OGLE-O-rich Mira variable stars, and reviewed the literature on red clump distance determination within that area.
RESULTS. We corroborate the asymmetry between positive and negative longitudes in in-plane regions, thus confirming the necessity to include a long bar. We obtain an average angle between the major axis of the long bar and the line Sun-Galactic centre of α=27.4±1.5 deg., aligned with the triaxial bulge and a semi-major-axis length ≈4 kpc. The tips of the long bar are in contact with the elliptical 3 kpc arm, with the major axis again aligned with the bulge and the long bar's major axes, whose tangential lines of sight correspond to ℓ=−22 deg. and ℓ=+27 deg. In the range of 50 degrees in the sky between these two longitudes, the stellar near 3 kpc arm is clearly detected at heliocentric distances around 5 kpc, and the stellar far 3 kpc arm is tentatively detected at heliocentric distances of 9-12 kpc.
AIMS. We aim to advance our knowledge of the morphology of these two components.
METHODS. We examined star counts of bright M giants in WISE-4.6μm and its distribution of distances derived from spectroscopic parallaxes with APOGEE-DR17. We also examined the distribution of distances of young OGLE-O-rich Mira variable stars, and reviewed the literature on red clump distance determination within that area.
RESULTS. We corroborate the asymmetry between positive and negative longitudes in in-plane regions, thus confirming the necessity to include a long bar. We obtain an average angle between the major axis of the long bar and the line Sun-Galactic centre of α=27.4±1.5 deg., aligned with the triaxial bulge and a semi-major-axis length ≈4 kpc. The tips of the long bar are in contact with the elliptical 3 kpc arm, with the major axis again aligned with the bulge and the long bar's major axes, whose tangential lines of sight correspond to ℓ=−22 deg. and ℓ=+27 deg. In the range of 50 degrees in the sky between these two longitudes, the stellar near 3 kpc arm is clearly detected at heliocentric distances around 5 kpc, and the stellar far 3 kpc arm is tentatively detected at heliocentric distances of 9-12 kpc.