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

Intrigued by the initial report of an extended lumiosity distribution perpendicular to the disk of the edge-on Sc galaxy NGC 5907, we have obtained very deep exposures of this galaxy with a Schmidt telescope, large-format CCD, and intermediate-band filters centered at 6660Å and 8020Å. These two filters, part of a 15-filter set, are custom-designed to avoid the brightest (and most variable) night sky lines. As a result, our images are able to go deeper, with lower sky noise than those taken with broad-band filters at similar effective wavelengths: e.g., 0.6 e − arcsec −2 sec −1 for our observations vs. 7.4 e − arcsec −2 sec −1 for the R-band measures of Morrison et al. In our assessment of both random and systematic errors, we show that the flux level where the errors of observation reach 1 mag arcsec −2 are 29.00 mag arcsec −2 in the 6660Å image (corresponding to 28.7 in R-band) and 27.4 mag arcsec −2 in the 8020Å image (essentially on the I-band system).As detailed in Shang et al., our observations show NGC 5907 has a luminous ring around it that most plausibly is due to the tidal disruption of a dwarf spheroidal galaxy by the much more massive spiral. Here we show that, fainter than 27th R mag arcsec −2 , the surface brightness around NGC 5907 is strongly asymmetric, being mostly brighter on NW (ring) side of the galaxy midplane. This asymmetry rules out a halo for the origin of the faint surface brightness we see.We find this asymmetry is likely an artifact owing to a combination of ring light and residual surface brightness at faint levels from stars that our star-masking procedure cannot completely eliminate. The possible existence of an optical face-on warp in NGC 5907, suggested by our VLA HI observations, is too confused with foreground star contamination to be independently studied. Good agreement with the surface photometry of NGC 5907 by Morrison et al. and other workers lead us to conclude that their data are similarly affected at faint levels by ring light and residual effects from their star masking procedures. Inspection of the images published by Morrison et al. and Sackett et al. confirm this to be the case. Thus, we conclude that NGC 5907 does not have a faint, extended halo.In this paper we present the details of our deep surface photometry of this galaxy, this time paying close attention to the issue of the faint luminosity distribution around this galaxy. Section 2 presents our observations, including details of the data reduction process, which are important for the reader to be able to critically assess the accuracy of our method. In Section 3 we study the faint luminosity distribution around NGC 5907 as it appears in our images, including how the ring, foreground stars, and a possible face-on warp can influence what we see. Our results are compared to those previously published in Section 4, in which we also reassess the likelihood of a halo existing around this galaxy. Section 5 summarizes the main results of this paper. OBSERVATIONS AND DATA REDUCTIONThe phases of data reduction that con...

In this paper, we present a multi-color photometric study of the nearby spiral galaxy M81, using images obtained with the Beijing Astronomical Observatory 60/90 cm Schmidt Telescope in 13 intermediate-band filters from 3800 to 10000Å. The observations cover the whole area of M81 with a total integration of 51 hours from February 1995 to February 1997. This provides a multi-color map of M81 in pixels of 1 ′′ .7 × 1 ′′ .7. Using theoretical stellar population synthesis models, we demonstrate that some BATC colors and color indices can be used to disentangle the age and metallicity effect. We compare in detail the observed properties of M81 with the predictions from population synthesis models and quantify the relative chemical abundance, age and reddening distributions for different components of M81. We find that the metallicity of M81 is about Z = 0.03 with no significant difference over the whole galaxy. In contrast, an age gradient is found between stellar populations of the central regions and of the bulge and disk regions of M81: the stellar population in its central regions is older than 8 Gyr while the disk stars are considerably younger, ∼ 2 Gyr. We also give the reddening distribution in M81. Some dust lanes are found in the galaxy bulge region and the reddening in the outer disk is higher than that in the central regions.

We present a deep, 42.79 hr image of the nearby, edge-on galaxy NGC 4565 in the Beijing-Arizona-Taipei-Connecticut (BATC) 6660Å band using the large-format CCD system on the 0.6m Schmidt telescope at the Xinglong Station of the National Astronomical Observatories of China (NAOC). Following the procedures previously developed by our team for the analysis of deep images of galaxies (Zheng et al.), we obtain a final image that is calibrated to an accuracy of 0.02 mag in zero point, and for which we can measure galaxy surface brightness to an accuracy of 0.25 mag at a surface brightness at 27.5 mag arcsec −2 at 6660Å, corresponding to a distance of 22 kpc from the center of the disk. The integrated magnitude of NGC 4565 in our filter is m 6660 = 8.99 (= R magnitude of 9.1) to a surface brightness of 28 mag arcsec −2 . We analyze the faint outer parts of this galaxy using a two-dimensional model comprised of three components: an exponential thin disk, an exponential thick disk, and a power-law halo. Combined with a need to provide a cut-off radius for the disk, a total of 12 parameters are included in our model.We determine the best values of our model parameters via 10,000 random initial values, 3,700 of which converge to final values. We then plot the χ 2 for each converged fit versus parameter value for each of the 12 parameters. The thin disk and thick disk parameters we determine here are consistent with those of previous studies of this galaxy. However, our very deep image permits a better determination of the power law fit to the halo, constraining this power law to be between r −3.2 and r −4.0 , with a best fit value of r −3.88 . We find the axis ratio of the halo to be 0.44 and its core radius to be 14.4 kpc (for an adopted distance of 14.5 Mpc). We also agree with others that the bulge of NGC 4565 is fit well by an exponential luminosity distribution with scale height similar to that found for the thin disk.

We describe in detail the extinction correction procedures used for the Beijing-Arizona-Taiwan-Connecticut Sky Survey (BATC Survey). The survey covers the spectral range 3200È9900 by Ó utilizing a set of 15 intermediate-band Ðlters. These Ðlters are speciÐcally designed to exclude most of the bright and variable night-sky emission lines. We also present extinction coefficients for the Ðlter passbands for typical photometric nights at the Xinglong Observing Station, Beijing Astronomical Observatory (where the observations of the survey are being carried out). Time-dependent, low-amplitude (D1%), nightly extinction variation has been observed. Such variation is demonstrably independent of Ðlter bandpass and air mass, with amplitudes ranging from D0.01 to D0.03 mag. The variation is plausibly caused by slowly varying (at D1%) atmospheric extinction, possibly related to changes in air pressure/temperature/humidity that occur during the night. An iterative Ðtting scheme has been developed to take this time-varying component into account. We conclude that the survey can achieve its stated observational goal, namely, an absolute photometric calibration that is tied to the system to an accuracy of 1% in all Ðlters. AB l ÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈ