2018/07/12 by Maosheng Xiang, Jianrong Shi, Xiaowei Liu +8 · 1 citation
Physics and Astronomy · #astro-ph.GA
paper · pdf · doi:10.3847/1538-4365/aad237
37 pages, 26 figures, 8 tables; Accepted for publication in ApJ supplement
arxiv created 2018/07/12 · arxiv updated 2018/08/15
We present a detailed determination and analysis of 3D stellar mass distribution of the Galactic disk for mono-age populations using a sample of 0.93 million main-sequence turn-off and subgiant stars from the LAMOST Galactic Surveys. Our results show (1) all stellar populations younger than 10 Gyr exhibit strong disk flaring, which is accompanied with a dumpy vertical density profile that is best described by a sechn function with index depending on both radius and age; (2) Asymmetries and wave-like oscillations are presented in both the radial and vertical direction, with strength varying with stellar populations; (3) As a contribution by the Local spiral arm, the mid-plane stellar mass density at solar radius but 400--800 pc (3--6^∘) away from the Sun in the azimuthal direction has a value of 0.0594±0.0008 M_\odot/pc3, which is 0.0164 M_\odot/pc3 higher than previous estimates at the solar neighborhood. The result causes doubts on the current estimate of local dark matter density; (4) The radial distribution of surface mass density yields a disk scale length evolving from ∼4 kpc for the young to ∼2 kpc for the old populations. The overall population exhibits a disk scale length of 2.48±0.05 kpc, and a total stellar mass of 3.6(±0.1)×1010 M_\odot assuming R\odot=8.0 kpc, and the value becomes 4.1(±0.1)×1010 M_\odot if R\odot=8.3 kpc; (5) The disk has a peak star formation rate (\rm SFR) changing from 6--8 Gyr at the inner to 4--6 Gyr ago at the outer part, indicating an inside-out assemblage history. The 0--1 Gyr population yields a recent disk total \rm SFR of 1.96±0.12 M_\odot/yr.