NGC6822演化研究：通过演化恒星族探究恒星形成历史
A Study on the Evolution of NGC6822. I. Investigating the Star Formation History through Evolved Stellar Populations
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中文总结 AI 辅助
本研究利用329颗长周期变星数据，通过演化恒星族方法重建了NGC6822的恒星形成历史，发现棒状区域有三次恒星形成峰值，外部区域有一次，并支持其曾穿过银河系维里半径的假设。
中文摘要 AI 辅助
NGC6822是本星系群中一个孤立的矮不规则星系，距离约490千秒差距。本文采用一种基于演化渐近巨星分支（AGB）星（即长周期变星，LPV）的方法，推导了NGC6822的恒星形成历史（SFH）。我们利用JHK$_s$波段的329颗LPV星的数据集，估算了随时间变化的恒星形成率（SFR），并重建了该星系的恒星形成历史。除了在0.0001 < Z < 0.012的恒定金属丰度范围内获得SFH外，我们还采用了三种不同的年龄-金属丰度关系（AMRs），以考虑星系在其一生中化学含量的变化。SFH在两个区域进行了研究。棒状区域包含一个中心区域，面积为189平方角分，而外部区域则包围棒状区域之外的区域，延伸至3千秒差距的径向距离。在棒状区域，我们识别出三个恒星形成峰值，分别出现在t ~ 4.7 Gyr（log t = 9.67）、t ~ 1.6 Gyr（log t = 9.21）和t ~ 48 Myr（log t = 7.63），其中t为回看时间。在外部区域，我们发现了一次恒星形成事件，发生在t ~ 4.6 Gyr。约4-5 Gyr前观测到的显著峰值进一步支持了先前研究提出的假设，表明NGC6822在过去曾穿过银河系的维里半径。
英文摘要
NGC6822 is an isolated dwarf irregular galaxy in the Local Group at a distance of $\sim$ 490 kpc . In this paper, we derived the star formation history (SFH) of NGC6822 employing a method based on evolved asymptotic giant branch (AGB) stars, known as long-period variable (LPV) stars. We utilized a dataset of 329 LPVs in JHK$_s$ bands to estimate the star formation rate (SFR) over time and reconstructed the SFH of the galaxy. In addition to obtaining the SFH assuming constant metallicity values within the range of 0.0001 $<$ Z $<$ 0.012, we also adopted three distinct age-metallicity relations (AMRs) to account for variations in the chemical content of the galaxy throughout its lifetime. The SFH has been investigated in two regions. The bar region encloses a central area of 189 arcmin$^{2}$, and the outer region encircles a field beyond the bar region, extending to the radial distance of 3 kpc. In the bar region, we identified three episodes of star formation peaking at $t \sim$ 4.7 Gyr (log $t = 9.67$), $t \sim$ 1.6 Gyr (log $t = 9.21$), and $t \sim$ 48 Myr (log $t = 7.63$), where $t$ is the look-back time. In the outer region, we found one episode of star formation occurring at $t \sim$ 4.6 Gyr. The significant peak observed $\sim$ 4-5 Gyr ago further supports the hypothesis suggested by the previous research, indicating that NGC6822 passed through the virial radius of the Milky Way in the past.
发表机构
- School of Astronomy, Institute for Research in Fundamental Sciences (IPM)（基础科学研究所天文学院）
- Astrophysics Group, Lennard-Jones Laboratories, Keele University（基尔大学天体物理组伦纳德-琼斯实验室）
- Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences（孔科利天文台匈牙利研究与教育网络天文学与地球科学研究中心）
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