Deep Wide-Field Spectrophotometry of the Open Cluster M67

Abstract

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 $\rm \eta = -2.0$.Comment: 74 pages, including 19 ps figures. Accepted for publication in AJ, Aug, 199

The Radial Velocity Experiment (Rave): Second Data Release

“…Stars with numbers between 0001 and 0295 were numbered by Fagerholm (1906). Stars with 64xx numbers are from Montgomery et al (1993) and star 7859 is from Fan et al (1996). …”

Relative flux calibration for the LAMOST Spectroscopic Survey of the Galactic anticentre

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Blue Stragglers in Clusters and Integrated Spectral Properties of Stellar Populations

“…This cluster were observed using a 15 intermediate-band filter photometric system covering the whole optical wavelength range between 3000-10000Å (BATC survey, [13]). Such an observation is ideally suited for our purpose.…”

“…Yu Xin & Licai Deng National Astronomical Observatories, Chinese Academy of Sciences e-mail: xinyu@bao.ac. cn,licai@bao.ac.cn 1 This is an example of building up the integrated spectral energy distribution (ISED) of a star cluster based on accurate spectrophotometry from the BATC survey [13]. Upper left panel: CMD of M67 with all highly probable members, the left box along the extension of the main sequence marks the region of BSSs.…”