论文标题
Hubble太空望远镜观测到附近LMC类似物的两个微弱的矮人卫星
Hubble Space Telescope Observations of Two Faint Dwarf Satellites of Nearby LMC Analogs from MADCASH
论文作者
论文摘要
我们提出了一个深度哈勃太空望远镜（HST）成像研究，对局部体积大麦芽云（LMC）类似物的光环中的两个矮星系进行了研究。这些矮人被发现是我们的Subaru+Hyper Soprime-Cam Madcash调查的一部分：Madcash-1，它是NGC 2403（D〜3.2 MPC）的卫星（D〜3.2 MPC）和Madcash-2，而Madcash-2是NGC 4214附近的以前未知的矮人Galaxy（D〜3.0 MPC）。我们的HST数据到达每个矮人红色巨型分支（TRGB）的尖端下方> 3.5 mag，使我们能够得出其结构参数并评估其恒星种群。我们测量trgb距离（$ d = 3.41^{+0.24} _ { - 0.23} $ mpc用于madcash-1，$ d = 3.00^{+0.13} _ { - 0.15} $ MPC用于MADCASH-2），并确认与他们的主人星系的关联。 Madcash-1是一个主要古老的金属贫困恒星系统（年龄〜13.5 Gyr，[m/h]〜-2.0），类似于许多本地组矮人。 MADCASH-2的CMD的建模表明，它主要包含古老的金属贫困星（年龄〜13.5 Gyr，[m/h]〜-2.0），但其恒星质量的约10％是1.1---1.5 Gyr的形成，并且形成了约1％的人，形成了400---500--500 Myr。鉴于其最近的恒星形成，我们使用绿色银行望远镜搜索Madcash-2以寻找中性氢，但找不到发射，并且估计$ <4.8 \ 4.8 \ times10^4 m _ {\ odot} $的HI质量上限。这些是本地组以外LMC质量的宿主星系中众所周知的最淡淡的矮卫星（$ m_ {v，\ text {madcash-1}} = - 7.81 \ pm0.18 $，$ m_ {v，\ \ fext {v，\ text {madcash-2}}} = - 9.15 \ pm0.15 \ pm0.12 $），其中一项是他们的录制的仪式，并在其中一个录制仪式。一旦完成了微弱矮卫星的Madcash调查，我们的人口普查将使我们能够测试CDM对层次结构形成的预测，并发现低质量宿主会影响其卫星的演变的物理机制。
We present a deep Hubble Space Telescope (HST) imaging study of two dwarf galaxies in the halos of Local Volume Large Magellanic Cloud (LMC) analogs. These dwarfs were discovered as part of our Subaru+Hyper Suprime-Cam MADCASH survey: MADCASH-1, which is a satellite of NGC 2403 (D~3.2 Mpc), and MADCASH-2, a previously unknown dwarf galaxy near NGC 4214 (D~3.0 Mpc). Our HST data reach >3.5 mag below the tip of the red giant branch (TRGB) of each dwarf, allowing us to derive their structural parameters and assess their stellar populations. We measure TRGB distances ($D=3.41^{+0.24}_{-0.23}$ Mpc for MADCASH-1, and $D=3.00^{+0.13}_{-0.15}$ Mpc for MADCASH-2), and confirm their associations with their host galaxies. MADCASH-1 is a predominantly old, metal-poor stellar system (age ~13.5 Gyr, [M/H] ~ -2.0), similar to many Local Group dwarfs. Modelling of MADCASH-2's CMD suggests that it contains mostly ancient, metal-poor stars (age ~13.5 Gyr, [M/H] ~ -2.0), but that ~10% of its stellar mass was formed 1.1--1.5 Gyr ago, and ~1% was formed 400--500 Myr ago. Given its recent star formation, we search MADCASH-2 for neutral hydrogen using the Green Bank Telescope, but find no emission and estimate an upper limit on the HI mass of $<4.8\times10^4 M_{\odot}$. These are the faintest dwarf satellites known around host galaxies of LMC mass outside the Local Group ($M_{V,\text{MADCASH-1}}=-7.81\pm0.18$, $M_{V,\text{MADCASH-2}}=-9.15\pm0.12$), and one of them shows signs of recent environmental quenching by its host. Once the MADCASH survey for faint dwarf satellites is complete, our census will enable us to test CDM predictions for hierarchical structure formation, and discover the physical mechanisms by which low-mass hosts influence the evolution of their satellites.
