论文标题
碳星作为标准蜡烛：I。
Carbon stars as standard candles: I. The luminosity function of carbon stars in the Magellanic Clouds
论文作者
论文摘要
我们本文中的目标是得出碳星亮度功能，该功能最终将用于确定星系的距离为$ 50 $ - $ 60 $ MPC，因此产生了哈勃常数的值。凉爽的N型碳星比富含氧气的恒星具有红色的近红外色。使用两个Micron All Sky Sumperion近红外光度法和Gaia Data Release 2，我们确定了麦哲伦云（MC）和银河系（MW）中的碳星。 MC中的碳星在近红外（$（J-k_s）_0 $，$ m_j $）颜色含量图中显示为独特的水平特征。我们构建颜色选择（$ 1.4 <（J-K_S）_0 <2 $），并得出颜色选择的碳星的光度功能。我们在J带中发现了中值的绝对大小和分散体，分别是大麦芽云和小的麦芽云，分别为（$ \ bar {m_j} = -6.284 \ pm 0.004 $，$σ= 0.352 0.365 \ pm 0.014 $）。 MC之间的差异可以通过小麦芽云的较低金属性来解释，但是在任何情况下，它都可以通过该技术来确定距离的星系类型。为了说明金属性效应，我们开发了一个综合幅度，称为C，对两个MC的误差加权平均C幅度相等。得益于下一代望远镜（JWST，ELT，TMT），可以在MC-Type星系中检测到碳星，距离$ 50 $ -60 $ 60 $ MPC。最终目标是最终尝试改善哈勃常数的测量，同时探索与其价值相关的当前紧张局势。
Our goal in this paper is to derive a carbon-star luminosity function that will eventually be used to determine distances to galaxies at $50$-$60$ Mpc and hence yield a value of the Hubble constant. Cool N-type carbon stars exhibit redder near-infrared colours than oxygen-rich stars. Using Two Micron All Sky Survey near-infrared photometry and the Gaia Data Release 2, we identify carbon stars in the Magellanic Clouds (MC) and the Milky Way (MW). Carbon stars in the MC appear as a distinct horizontal feature in the near-infrared ($(J-K_s)_0$, $M_J$) colour-magnitude diagram. We build a colour selection ($1.4 < (J-K_s)_0 < 2$) and derive the luminosity function of the colour-selected carbon stars. We find the median absolute magnitude and the dispersion, in the J band, for the Large Magellanic Cloud and the Small Magellanic Cloud to be, respectively, ($\bar{M_J} = -6.284 \pm 0.004$, $σ= 0.352 \pm 0.005$) and ($\bar{M_J} = -6.160 \pm 0.015$, $σ= 0.365 \pm 0.014$). The difference between the MC may be explained by the lower metallicity of the Small Magellanic Cloud, but in any case it provides limits on the type of galaxy whose distance can be determined with this technique. To account for metallicity effects, we developed a composite magnitude, named C, for which the error-weighted mean C magnitude of both the MC are equal. Thanks to the next generation of telescopes (JWST, ELT, TMT), carbon stars could be detected in MC-type galaxies at distances out to $50$-$60$ Mpc. The final goal is to eventually try and improve the measurement of the Hubble constant while exploring the current tensions related to its value.
