分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： A rare population of massive disk galaxies have been found to invade the red sequence dominated by early-type galaxies. These red/quenched massive disk galaxies have recently gained great interest into their formation and origins. The usually proposed quenching mechanisms, such as bar quenching and environment quenching, seem not suitable for those bulge-less quenched disks in low-density environment. In this paper, we use the IllustrisTNG-300 simulation to investigate the formation of massive quenched central disk galaxies. It is found that these galaxies contain less gas and harbor giant supermassive black holes(SMBHs) (above $ 10^{8}M_{\odot}$) than their star forming counterparts. By tracing their formation history, we found that quenched disk galaxies formed early and preserved disk morphology for cosmological time scales. They have experienced less than one major merger on average and it is mainly mini-mergers (mass ratio $<$1/10) that contribute to the growth of their SMBHs. In the Illustris-TNG simulation the black hole feedback mode switches from thermal to kinetic feedback when the black hole mass is more massive than $\sim 10^{8}M_{\odot}$, which is more efficient to eject gas outside of the galaxy and to suppress further cooling of hot gaseous halo. We conclude that kinetic AGN feedback in massive red/quenched disk galaxy is the dominant quenching mechanism.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Yuxi
Lu
Ivan Minchev
Tobias Buck
Sergey Khoperskov
Matthias Steinmetz
Noam Libeskind
Gabriele Cescutti
Ken C. Freeman
摘要： Stars move away from their birth places over time via a process known as radial migration, which blurs chemo-kinematic relations used for reconstructing the Milky Way formation history. One of the ultimate goals of Galactic Archaeology, therefore, is to find stars' birth aggregates in the disk via chemical tagging. Here we show that stellar birth radii can be derived directly from the data with minimum prior assumptions on the Galactic enrichment history. We recover the time evolution of the stellar birth metallicity gradient, $d$[Fe/H]($R$, $\tau$)/$dR$, through its inverse relation to the metallicity range as a function of age today, allowing us to place any star with age and metallicity measurements back to its birthplace, $R_b$. Applying our method to a high-precision large data set of Milky Way disk subgiant stars, we find a steepening of the birth metallicity gradient from 11 to 8 Gyr ago, which coincides with the time of the last major merger, Gaia-Sausage-Enceladus (GSE). This transition appears to play a major role in shaping both the age-metallicity relation and the bimodality in the [$\alpha$/Fe]-[Fe/H] plane. By dissecting the disk into mono-$R_b$ populations, clumps in the low-[$\alpha$/Fe] sequence appear, which are not seen in the total sample and coincide in time with known star-formation bursts. We estimated that the Sun was born at $4.5 \pm 0.4$ kpc from the Galactic center. Our $R_b$ estimates provide the missing piece needed to recover the Milky Way formation history, while the by-product,[Fe/H]$(R$, $\tau)$, can be used as the thus-far missing prior for chemical evolution modeling.
点击量
待评议
点击量
下载量
评论
