Deep wide-field spectrophotometry of the open cluster M67
Deep wide-field spectrophotometry of the open cluster M67
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DOI：
10.1086/118039
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发表时间：
1996-04
期刊：
影响因子：
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通讯作者：
Xiaohui Fan;D. Burstein;J. S. Chen;Jin Zhu;Zhao-ji Jiang;Hong Wu;Haojing Yan;Zhongyuan Zheng-Zhongyuan-Zhe
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文献类型：
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作者：
Xiaohui Fan;D. Burstein;J. S. Chen;Jin Zhu;Zhao-ji Jiang;Hong Wu;Haojing Yan;Zhongyuan Zheng-Zhongyuan-Zhe
我们展示了以旧疏散星团 M67 为中心的 2 平方度视场的九色 CCD 中带分光光度测量，从 3890$\rm \AA$ 到近 1$\mu$。出于科学和校准原因，这些观测结果被作为 BATC（北京-亚利桑那-台北-康涅狄格）天空颜色调查的一部分。通过这些数据，我们表明 BATC 调查可以实现其目标，即获得 0.01 mag 的零点精度，并可低至 V = 21，随机误差为 0.3 mag。我们将颜色幅度图 (CMD) 与沃西的理论模型进行拟合。最终结果是 4.0 Gyr, [Fe/H] = $-0.10$ 模型与我们的数据完美契合，包括与主序 (MS) 关闭的良好契合。我们的数据与 M67 中 50% 的恒星是双星且双星质量比随机分布的玩具模型一致，尽管不能排除具有不同质量比分布的其他模型。 M67 中恒星的空间分布和质量函数 (MF) 显示出星团中恒星的动力学演化和蒸发的显着影响。蓝离散星和双星是星团内最浓缩的，其浓缩程度取决于质量。我们发现 M67 具有细长的形状，相对于银道面的角度为 $15^{\circ}$。在其潮汐半径内，观测到的 M67 MF 在 1.2 $\rm M_\odot$ 和 $\rm 0.8 M_\odot$ 之间具有萨尔彼得斜率 $\rm \eta = -1.93 \pm 0.66$。对于质量低于 0.8 $\rm M_\odot$ 的恒星，$\rm \eta \sim 0$。较低质量处的 MF 趋于平稳可能是该质量范围内较低质量恒星以每 $\sim 10^7$ 年蒸发一次的速度蒸发的结果。如果是这样，M67 的 IMF 的规范字段值为 $\rm \eta = -2.0$ 是合理的。
We present nine color CCD intermediate-band spectrophotometry of a two square degree field centered on the old open cluster M67, from 3890$\rm \AA$ to nearly 1$\mu$. These observations are taken as a part of the BATC (Beijing-Arizona-Taipei-Connecticut) Color Survey of the Sky, for both scientific and calibration reasons. With these data we show that the BATC survey can reach its goal of obtaining spectrophotometry to a zero point accuracy of 0.01 mag, and down to V = 21 with 0.3 mag random error. We fit the color-magnitude diagrams (CMDs) with Worthey's theoretical models. The net result is the excellent fit of the 4.0 Gyr, [Fe/H] = $-0.10$ model to our data, including a good fit to the main sequence (MS) turn-off. Our data are consistent with a toy model with 50\% of the stars in M67 being binaries and a random distribution of binary mass-ratios, although other models with different mass-ratio distributions cannot be ruled out. The spatial distribution and mass function (MF) of stars in M67 show marked effects of dynamical evolution and evaporation of stars from the cluster. Blue stragglers and binary stars are the most condensed within the cluster, with degree of condensation depending on mass.We find M67 to have an elongated shape, oriented at an angle of $15^{\circ}$ relative to the galactic plane. Within its tidal radius, the observed MF of M67 between 1.2 $\rm M_\odot$ and $\rm 0.8 M_\odot$ has a Salpeter slope $\rm \eta = -1.93 \pm 0.66$. For stars of mass below 0.8 $\rm M_\odot$, $\rm \eta \sim 0$. It is plausible that the leveling-off of the MF at lower masses is a result of evaporation of lower mass stars in this mass range at a rate of one every $\sim 10^7$ years. If so, it is plausible that the IMF of M67 has the canonical field value of $\rm \eta = -2.0$.