论文标题
从球状簇palomar2提起灰尘面纱2
Lifting the dust veil from the Globular Cluster Palomar2
论文作者
论文摘要
这项工作采用高质量的{\ em Hubble太空望远镜}（{\ em Hst}）高级相机进行调查（ACS）F606W和F814W光度法，以纠正影响差异的差分，影响了不良的球形 - 绘制的全球胶状图（CMD）的差异，并纠正。通过假设在palomar \ \ 2的视野中提取的CMD之间的形态差异基本上与沿$δe（B-V）$ QMD的形态学差异相对应，从而考虑了差异。所有部分CMD的平均红色差异为$ \叠加{Δe（b-v）} = 0.24 \ pm0.08 $，最高达到$ΔE（B-V）= 0.52 $。校正后的CMD显示出明确且相对狭窄的进化序列，尤其是对于进化的恒星，即分别为红色巨型，水平和渐近巨型分支（RGB，HB和AGB）。校正后的CMD的上部主序列的平均宽度和RGB曲线对应于原始的56 \％。在此CMD上测量的参数表明，palomar \，2是$ \ of13.25 $ \，gyr ol，具有质量$ $ m \ sim1.4 \ sim1.4 \ times10^5 \，m_ \ odot $存储在星空中以全局金属性$ z/zo \ oft0.03 $为特征，对应于$ -1.9 \ leq [fe/h] \ leq-1.6 $（$ 0.0 \ leq [α/fe [α/fe] \ leq+0.4 $），与其他外部halo gcs相当一致。其他参数是绝对幅度$ m_v \ of-7.8 $，以及分别分别分别为core和halfight radii $ r_c \ oft2.6 $ \，PC和$ r_ {hl} \ oft4.7 $ \，PC。
This work employs high-quality {\em Hubble Space Telescope} ({\em HST}) Advanced Camera for Surveys (ACS) F606W and F814W photometry to correct for the differential reddening affecting the colour-magnitude diagram (CMD) of the poorly-studied globular cluster (GC) Palomar\,2. Differential reddening is taken into account by assuming that morphological differences among CMDs extracted across the field of view of Palomar\,2 correspond essentially to shifts (quantified in terms of $δE(B-V)$) along the reddening vector due to a non-uniform dust distribution. The average reddening difference over all partial CMDs is $\overline{δE(B-V)}=0.24\pm0.08$, with the highest reaching $δE(B-V) =0.52$. The corrected CMD displays well-defined and relatively narrow evolutionary sequences, especially for the evolved stars, i.e. the red-giant, horizontal and asymptotic giant branches (RGB, HB and AGB, respectively). The average width of the upper main sequence and RGB profiles of the corrected CMD corresponds to 56\% of the original one. Parameters measured on this CMD show that Palomar\,2 is $\approx13.25$\,Gyr old, has the mass $M\sim1.4\times10^5\,m_\odot$ stored in stars, is affected by the foreground $E(B-V)\approx0.93$, is located at $d_\odot\approx26$\,Kpc from the Sun, and is characterized by the global metallicity $Z/Zo\approx0.03$, which corresponds to the range $-1.9\leq [Fe/H] \leq-1.6$ (for $0.0\leq[α/Fe]\leq+0.4$), quite consistent with other outer halo GCs. Additional parameters are the absolute magnitude $M_V\approx-7.8$, and the core and half-light radii $r_C\approx2.6$\,pc and $R_{HL}\approx4.7$\,pc, respectively.
