论文标题
艾萨克·牛顿望远镜监测矮星系的调查 - v。射手座矮人的恒星形成历史不规则的星系，衍生自长时间星星
The Isaac Newton Telescope monitoring survey of Local Group dwarf galaxies--V. The star formation history of Sagittarius dwarf irregular galaxy derived from long period variable stars
论文作者
论文摘要
我们对2016年6月至2017年10月的Sagittarius矮人不规则星系（Sagdig）进行了光学监测调查，使用La Palama的2.5-M Isaac Newton望远镜（INT）。我们的目标是识别长时间变量恒星（LPV），即渐近巨型分支星（AGB）和红色超级巨星（RSG），以获取孤立的，金属贫困的Sagdig的恒星形成历史（SFH）。出于我们的目的，我们使用了一种依赖于评估这些最具进化恒星的出生质量之间的关系的方法。我们在Sagdig的两个半灯半径内发现了$ 27 $ LPV候选人。 $ 10 $ LPV候选人与以前的研究共同，其中包括一项非常尘土飞扬的AGB（X-AGB）。通过采用金属性$ z = 0.0002 $的老年人群，$ z = 0.0004 $的年轻人，我们估计，恒星形成速率从$ 0.0005 \ pm0.0002 $ m $ m $ _ {\ odot} $ yr $ yr $^{ - yr $^{ - 1}} m $ _ {\ odot} $ yr $^{ - 1} $ kpc $^{ - 2} $（$ 0.06 $ gyr ogo）。像许多矮人的不规则星系一样，萨格迪格（Sagdig）在其一生中具有连续的恒星形成活动，尽管速度不同，并且自$ z \ simeq 1 $以来就会增强恒星形成。我们还评估了三种金属性选择的Sagdig半光线半径内的总恒星质量。对于金属性$ z = 0.0002 $和$ z = 0.0004 $，我们估计恒星质量m $ _*$ =（$ 5.4 \ pm 2.3 $）$ \ times $ $ $ $ 10^ 6 $和（$ 3.0 \ pm 1.3 $）$ $ $ $ $ $ 10^ 6 $ m $ m $ m $ _ {\ odot} $，分别为$。此外，我们使用红色巨型分支（TRGB）的尖端确定了一个距离模量$ $ $ $ $ $ $ $ 25.27 \ pM0.05 $ mag。
We conducted an optical monitoring survey of the Sagittarius dwarf irregular galaxy (SagDIG) during the period of June 2016 -- October 2017, using the 2.5-m Isaac Newton Telescope (INT) at La Palama. Our goal was to identify Long Period Variable stars (LPVs), namely asymptotic giant branch stars (AGBs) and red supergiant stars (RSGs), to obtain the Star Formation History (SFH) of isolated, metal-poor SagDIG. For our purpose, we used a method that relies on evaluating the relation between luminosity and the birth mass of these most evolved stars. We found $27$ LPV candidates within two half-light radii of SagDIG. $10$ LPV candidates were in common with previous studies, including one very dusty AGB (x-AGB). By adopting the metallicity $Z = 0.0002$ for older population and $Z=0.0004$ for younger ages, we estimated that the star formation rate changes from $0.0005\pm0.0002$ M$_{\odot}$yr$^{-1}$kpc$^{-2}$ ($13$ Gyr ago) to $0.0021 \pm 0.0010$ M$_{\odot}$yr$^{-1}$kpc$^{-2}$ ($0.06$ Gyr ago). Like many dwarf irregular galaxies, SagDIG has had continuous star formation activity across its lifetime, though with different rates, and experiences an enhancement of star formation since $z \simeq 1$. We also evaluated the total stellar mass within two half-light radii of SagDIG for three choices of metallicities. For metallicity $Z = 0.0002$ and $Z=0.0004$ we estimated the stellar mass M$_*$ = ($5.4 \pm 2.3$) $\times$ $10^ 6$ and ($3.0 \pm 1.3$) $\times$ $10^ 6$ M$_{\odot}$, respectively. Additionally, we determined a distance modulus $μ$ = $25.27\pm0.05$ mag, using the tip of the red giant branch (TRGB).
