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The Beijing-Arizona Sky Survey (BASS) is a wide and deep imaging survey to cover a 5400 deg$^2$ area in the Northern Galactic Cap with the 2.3m Bok telescope using two filters ($g$ and $r$ bands). The Mosaic $z$-band Legacy Survey (MzLS) covers the same area in $z$ band with the 4m Mayall telescope. These two surveys will be used for spectroscopic targeting of the Dark Energy Spectroscopic Instrument (DESI). The BASS survey observations were completed in 2019 March. This paper describes the third data release (DR3) of BASS, which contains the photometric data from all BASS and MzLS observations between 2015 January and 2019 March. The median astrometric precision relative to {\it Gaia} positions is about 17 mas and the median photometric offset relative to the PanSTARRS1 photometry is within 5 mmag. The median $5\sigma$ AB magnitude depths for point sources are 24.2, 23.6, and 23.0 mag for $g$, $r$, and $z$ bands, respectively. The photometric depth within the survey area is highly homogeneous, with the difference between the 20\% and 80\% depth less than 0.3 mag. The DR3 data, including raw data, calibrated single-epoch images, single-epoch photometric catalogs, stacked images, and co-added photometric catalogs, are publicly accessible at \url{http://batc.bao.ac.cn/BASS/doku.php?id=datarelease:home}., Comment: published in ApJS

In this paper, we present extensive optical and ultraviolet (UV) observations of the type Ia supernova (SN Ia) 2013gs discovered during the Tsinghua-NAOC Transient Survey. The photometric observations in the optical show that the light curves of SN 2013gs is similar to that of normal SNe Ia, with an absolute peak magnitude of $M_{B}$ = $-$19.25 $\pm$ 0.15 mag and a post-maximum decline rate $\Delta$m$_{15}$(B) = 1.00 $ \pm $ 0.05 mag. \emph{Gehrels Swift} UVOT observations indicate that SN 2013gs shows unusually strong UV emission (especially in the $uvw1$ band) at around the maximum light (M$_{uvw1}$ $\sim$ $-$18.9 mag). The SN is characterized by relatively weak Fe~{\sc ii} {\sc iii} absorptions at $\sim$ 5000{\AA} in the early spectra and a larger expansion velocity ($v_{Si}$ $\sim$ 13,000 km s$^{-1}$ around the maximum light) than the normal-velocity SNe Ia. We discuss the relation between the $uvw1-v$ color and some observables, including Si~{\sc ii} velocity, line strength of Si~{\sc ii} $\lambda$6355, Fe~{\sc ii}/{\sc iii} lines and $\Delta m_{15}$(B). Compared to other fast-expanding SNe Ia, SN 2013gs exhibits Si and Fe absorption lines with similar strength and bluer $uvw1-v$ color. We briefly discussed the origin of the observed UV dispersion of SNe Ia., Comment: 31 pages, 10 figures, accepted to publish in ApJ

The Beijing-Arizona Sky Survey (BASS) is a wide-field two-band photometric survey of the Northern Galactic Cap using the 90Prime imager on the 2.3 m Bok telescope at Kitt Peak. It is a four-year collaboration between the National Astronomical Observatory of China and Steward Observatory, the University of Arizona, serving as one of the three imaging surveys to provide photometric input catalogs for target selection of the Dark Energy Spectroscopic Instrument (DESI) project. BASS will take up to 240 dark/grey nights to cover an area of about 5400 deg$^2$ in the $g$ and $r$ bands. The 5$\sigma$ limiting AB magnitudes for point sources in the two bands, corrected for the Galactic extinction, are 24.0 and 23.4 mag, respectively. BASS, together with other DESI imaging surveys, will provide unique science opportunities that cover a wide range of topics in both Galactic and extragalactic astronomy., Comment: 10 pages, submitted to PASP

The Beijing-Arizona Sky Survey (BASS) is a new wide-field legacy imaging survey in the northern Galactic cap using the 2.3m Bok telescope. The survey will cover about 5400 deg$^2$ in the $g$ and $r$ bands, and the expected 5$\sigma$ depths (corrected for the Galactic extinction) in the two bands are 24.0 and 23.4 mag, respectively. BASS started observations in January 2015, and has completed about 41% of the whole area as of July 2016. The first data release contains both calibrated images and photometric catalogs obtained in 2015 and 2016. The depths of single-epoch images in the two bands are 23.4 and 22.9 mag, and the full depths of three epochs are about 24.1 and 23.5 mag, respectively., Comment: 16 pages, published by AJ

We study the integral Galactic extinction and reddening based on the galaxy catalog of the South Galactic Cap U-band Sky Survey (SCUSS), where $u$ band galaxy number counts and $u-r$ color distribution are used to derive the Galactic extinction and reddening respectively. We compare these independent statistical measurements with the reddening map of \citet{Schlegel1998}(SFD) and find that both the extinction and reddening from the number counts and color distribution are in good agreement with the SFD results at low extinction regions ($E(B-V)^{SFD}<0.12$ mag). However, for high extinction regions ($E(B-V)^{SFD}>0.12$ mag), the SFD map overestimates the Galactic reddening systematically, which can be approximated by a linear relation $\Delta E(B-V)= 0.43[E(B-V)^{SFD}-0.12$]. By combing the results of galaxy number counts and color distribution together, we find that the shape of the Galactic extinction curve is in good agreement with the standard $R_V=3.1$ extinction law of \cite{ODonnell1994}.

We selected 82 u-band variable objects based on the u-band photometry data from SCUSS and SDSS, in the field of LAMOST Complete Spectroscopic Survey of Pointing Area at Southern Galactic Cap. The magnitude variation of the targets is restricted to larger than 0.2 mag and limiting magnitude down to 19.0 mag in u-band. According to the spectra from LAMOST, there are 11 quasars with red-shift between 0.4 and 1.8, 60 variable stars and 11 unidentified targets. The variable stars include one active M-dwarf with a series of Balmer emission lines, seven Horizontal Branch stars containing six RR Lyrae stars matching with SIMBAD, and one giant, one AGB star and two RR Lyrae candidates by different colour selections. All these variable stars mainly locate near the main sequence in the g-r verse u-g diagram. The quasars are well distinguished from stars by both u-g colour and variation in u-band., Comment: 8 figures, 2 tables, accepted for publication in APSS

The SCUSS is a deep $u$-band imaging survey in the south Galactic cap using the 2.3m Bok telescope. The survey observations were completed in the end of 2013, covering an area of about 5000 square degrees. We release the data in the region with an area of about 4000 deg$^2$ that is mostly covered by the Sloan digital sky survey. The data products contain calibrated single-epoch images, stacked images, photometric catalogs, and a catalog of star proper motions derived by Peng et al, 2015. The median seeing and magnitude limit ($5\sigma$) are about 2".0 and 23.2 mag, respectively. There are about 8 million objects having measurements of absolute proper motions. All the data and related documentations can be accessed through the SCUSS data release website of \url{http://batc.bao.ac.cn/Uband/data.html}., Comment: 13 pages, 7 figures, accepted by AJ

Based on SDSS g, r and SCUSS (South Galactic Cap of u-band Sky Survey) $u$ photometry, we develop a photometric calibration for estimating the stellar metallicity from $u-g$ and $g-r$ colors by using the SDSS spectra of 32,542 F- and G-type main sequence stars, which cover almost $3700$ deg$^{2}$ in the south Galactic cap. The rms scatter of the photometric metallicity residuals relative to spectrum-based metallicity is $0.14$ dex when $g-r<0.4$, and $0.16$ dex when $g-r>0.4$. Due to the deeper and more accurate magnitude of SCUSS $u$ band, the estimate can be used up to the faint magnitude of $g=21$. This application range of photometric metallicity calibration is wide enough so that it can be used to study metallicity distribution of distant stars. In this study, we select the Sagittarius (Sgr) stream and its neighboring field halo stars in south Galactic cap to study their metallicity distribution. We find that the Sgr stream at the cylindrical Galactocentric coordinate of $R\sim 19$ kpc, $\left| z\right| \sim 14$ kpc exhibits a relative rich metallicity distribution, and the neighboring field halo stars in our studied fields can be modeled by two-Gaussian model, with peaks respectively at [Fe/H]$=-1.9$ and [Fe/H]$=-1.5$., Comment: 8 pages, 7 figures, Accepted for publication in MNRAS

Absolute proper motions for $\sim$ 7.7 million objects were derived based on data from the South Galactic Cap u-band Sky Survey (SCUSS) and astrometric data derived from uncompressed Digitized Sky Surveys that the Space Telescope Science Institute (STScI) created from the Palomar and UK Schmidt survey plates. We put a great deal of effort into correcting the position-, magnitude-, and color-dependent systematic errors in the derived absolute proper motions. The spectroscopically confirmed quasars were used to test the internal systematic and random error of the proper motions. The systematic errors of the overall proper motions in the SCUSS catalog are estimated as -0.08 and -0.06 mas/yr for {\mu}{\alpha} cos {\delta} and {\mu}{\delta}, respectively. The random errors of the proper motions in the SCUSS catalog are estimated independently as 4.2 and 4.4 mas/yr for {\mu}{\alpha} cos {\delta} and {\mu}{\delta}. There are no obvious position-, magnitude-, and color-dependent systematic errors of the SCUSS proper motions. The random error of the proper motions goes up with the magnitude from about 3 mas/yr at u < 18.0 mag to about 7 mas/yr at u = 22.0 mag. The proper motions of stars in SCUSS catalog are compared with those in the SDSS catalog, and they are highly consistent., Comment: 8 pages, 10 figures ,PASP accepted

The South Galactic Cap $u$-band Sky Survey (SCUSS) provides a deep $u$-band imaging of about 5000 deg$^2$ in south Galactic cap. It is about 1.5 mag deeper than the SDSS $u$-band. In this paper we evaluate the capability of quasar selection using both SCUSS and SDSS data, based on considerations of the deep SCUSS $u$-band imaging and two-epoch $u$-band variability. We find that the combination of the SCUSS $u$-band and the SDSS $griz$ band allows us to select more faint quasars and more quasars at redshift around 2.2 than the selection only with the SDSS $ugriz$ data. Quasars have significant $u$-band variabilities. The fraction of quasars with large two-epoch variability is much higher than that of stars. The selection by variability can select both low-redshift quasars with ultraviolet excess and mid-redshift ($2 < z <3.5$) quasars where quasar selection by optical colors is inefficient. The above two selections are complementary and make full use of the SCUSS u-band advantages., Comment: 10 pages, 8 figures, accepted by PASP

The Tsinghua University-National Astronomical Observatories of China (NAOC) Transient Survey (TNTS) is an automatic survey for a systematic exploration of optical transients (OTs), conducted with a 60/90 cm Schmidt telescope at Xinglong station of NAOC. This survey repeatedly covers ~ 1000 square degrees of the north sky with a cadence of 3-4 days. With an exposure of 60 s, the survey reaches a limited unfiltered magnitude of about 19.5 mag. This enables us to discover supernovae at their relatively young stages. In this paper, we describe the overall performance of our survey during the first year and present some preliminary results., Comment: 11 pages, 7 figures, accepted for publication in Research in Astron. Astrophys

We present the [OII] luminosity function measured in the redshift range 0.1

Based on SDSS and South Galactic Cap of u-band Sky Survey (SCUSS) early data, we use star counts method to estimate the Galactic structure parameters in an intermediate latitude with 10,180 main-sequence (MS) stars in absolute magnitude interval of $4 \leq M_r \leq 13$. We divide the absolute magnitude into five intervals:$4 \leq M_r < 5$, $5 \leq M_r < 6$, $6 \leq M_r < 8$, $8 \leq M_r < 10$, $10 \leq M_r \leq 13$, and estimate the Galactic structure parameters in each absolute magnitude interval to explore their possible variation with the absolute magnitude. Our study shows the parameters depend on absolute magnitude. For the thin disk, the intrinsic faint MS stars have large local space density and they tend to stay close to the Galactic plane. A plausible explanation is that faint MS stars with long lifetime experience long gravitational interaction time result in a short scaleheight. However, for the thick disk, the parameters show a complex trend with absolute magnitude, which may imply the complicated original of the thick disk. For the halo, the intrinsic faint MS stars have large local density and small axial ratio, which indicate a flattened inner halo and a more spherical outer halo., Comment: 10 pages, 5 figures, Accepted for publication in MNRAS

Multi-band photometric images from ultraviolet and optical to infrared are collected to derive spatially resolved properties of a nearby Scd type galaxy M 101. With evolutionary stellar population synthesis models, two-dimensional distributions and radial profiles of age, metallicity, dust attenuation, and star formation timescale in the form of the Sandage star formation history are obtained. When fitting with the models, we use the IRX-$A_\mathrm{FUV}$ relation, found to depend on a second parameter of birth rate b (ratio of present and past-averaged star formation rate), to constrain the dust attenuation. There are obvious parameter gradients in the disk of M101, which supports the theory of an "inside-out disk" growth scenario. Two distinct disc regions with different gradients of age and color are discovered, similar to another late-type galaxy NGC 628. The metallicity gradient of the stellar content is flatter than that of H {\sc ii} regions. The stellar disk is optically thicker inside than outside and the global dust attenuation of this galaxy is lower, compared with galaxies of similar and earlier morphological type. We highlight that a variational star formation timescale describes the real star formation history of a galaxy. The timescale increases steadily from the center to the outskirt. We also confirm that the bulge in this galaxy is a disk-like pseudobulge, whose evolution is likely to be induced by some secular processes of the small bar with relatively young age, rich metal, and much dust., Comment: 37 pages, 13 figures. Accepted to ApJ

We present the results of our optical monitoring of the BL Lac object S5 0716+714 on seven nights in 2006 December. The monitoring was carried out simultaneously at three optical wavelengths with a novel photometric system. The object did not show large-amplitude internight variations during this period. Intranight variations were observed on four nights and probably on one more. Strong bluer-when-brighter chromatism was detected on both intranight and internight timescales. The intranight variation amplitude decreases in the wavelength sequence of B', R', and V'. Cross correlation analyses revealed that the variability at the $B'$ and $V'$ bands lead that at the $R'$ band by about 30 minutes on one night., Comment: 31 pages, 12 figures, accepted by the Astronomical Journal

The colour behaviour of blazars is a subject of much debate. One argument is that the BL Lac objects show bluer-when-brighter chromatism while the flat-spectrum radio quasars (FSRQs) display redder-when-brighter trend. Base on a 3.5-year three-colour monitoring programme, we studied the optical variability and colour behaviour of one FSRQ, 3C 345. There is at least one outburst in this period. The overall variation amplitude is 2.640 mags in the $i$ band. Intra-night variability was observed on two nights. The bluer-when-brighter and redder-when-brighter chromatisms were simultaneously observed in this object when using different pairs of passbands to compute the colours. The bluer-when-brighter chromatism is a shared property with the BL Lacs, while the redder-when-brighter trend is likely due to two less variable emission features, the Mg\,{\sc ii} line and the blue bump, at short wavelengths. With numerical simulations, we show that some other strong but less variable emission lines in the spectrum of FSRQs may also significantly alter their colour behaviour. Then the colour behaviour of an FSRQ is linked not only to the emission process in the relativistic jet, but also to the redshift, the passbands used for computing the colour and the strengths of the less variable emission features relative to the strength of the non-thermal continuum., Comment: 9 pages, 9 figures, Accepted by MNRAS

An optical photometric observation in 15 bands was carried out for nearby galaxy cluster Abell 1775 by the Beijing-Arizona-Taiwan-Connecticut (BATC) multi-color system. Over 5000 sources' spectral energy distributions (SEDs) were obtained. Since this cluster has also been observed by the Sloan Digital Sky Survey (SDSS), the BATC SEDs were combined with the SDSS five-band photometric data. Using the combined SEDs, 146 faint galaxies were selected as new member galaxies by the photometric redshift technique. Based on the positions, redshifts and 20-band SEDs of member galaxies, dynamical substructures and luminosity functions (LFs) of A1775 were investigated. The previous reported bimodal structure of A1775 has been confirmed: a poor subcluster with lower redshift, A1775A, is located ~14' southeast to the main concentration A1775B. After taking into account the new supplemented member galaxies, a new subcluster A1775C was found along the aligned direction of A1775A and A1775B. The different LF faint ends of the two subclusters indicate that A1775B is a more dynamically evolved system, while A1775A is still dynamically young. By the STARLIGHT spectral synthesis code, the star- formation histories of the member galaxies were studied. The dependence of the mean stellar ages upon the Hubble type was confirmed, and the environmental effect on star-formation activities for galaxies in A1775B has been explored., Comment: 25pages,18figures; PASJ: Publ. Astron. Soc. Japan 2011 Vol.63 No.3

Panchromatic spectral energy distribution (SED) from the ultraviolet (UV), optical to infrared (IR) photometry of NGC 628, combined with the evolutionary stellar population synthesis, is used to derive the spatially resolved age, metallicity and reddening maps. These parameter distributions show that the bulge of this galaxy is a disk-like pseudobulge, which has the S{\'e}rsic index close to the exponential law, rich gas, and a young circumnuclear ring structure. We also discover the disk has two distinct regions with different radial age and metallicity gradients. The inner region is older and has a much steeper age gradient than the outer region of the disk. Both these two regions and the central young structure can be seen in the radial profile of the optical color. Based on the age and reddening distributions, we consider that the pseudobulge and disk are likely to have grown via the secular evolution, which is the redistribution of mass and energy through the angular momentum transport caused by the non-axisymmetric potential of the spirals. However, possible gas accretion events could affect the outer region of the disk, due to abundant H{\sc i} gas accumulating in the outer disk., Comment: 9 figures, accepted for publication in AJ

M31 globular cluster B379 is the first extragalactic cluster, the age of which was determined by main-sequence photometry. In this method, the age of a cluster is obtained by fitting its CMD with stellar evolutionary models. However, different stellar evolutionary models use different parameters of stellar evolution, such as range of stellar masses, different opacities and equations of state, and different recipes, and so on. So, it is interesting to check whether different stellar evolutionary models can give consistent results for the same cluster. Brown et al. (2004a) constrained the age of B379 by comparing its CMD with isochrones of the 2006 VandenBerg models. Using SSP models of BC03 and its multi-photometry, Ma et al. (2007) independently determined the age of B379, which is in good agreement with the determination of Brown et al. (2004a). The BC03 models are calculated based on the Padova evolutionary tracks. It is necessary to check whether the age of B379 which, being determined based on the Padova evolutionary tracks, is in agreement with the determination of Brown et al. (2004a). So, in this paper, we re-determine its age using isochrones of the Padova stellar evolutionary models. In addition, the metal abundance, the distance modulus, and the reddening value for B379 are also determined in this paper. The results obtained in this paper are consistent with the previous determinations, which including the age obtained by Brown et al. (2004a). So, this paper confirms the consistence of the age scale of B379 between the Padova isochrones and the 2006 VandenBerg isochrones, i.e. the results' comparison between Brown et al. (2004a) and Ma et al. (2007) is meaningful. The results obtained in this paper are: the metallicity [M/H]=-0.325, the age $\tau=11.0\pm1.5$ Gyr, the reddening value E(B-V)=0.08, and the distance modulus $(m-M)_{0}=24.44\pm0.10$., Comment: Accepted for Publication in PASP, 7 pages, 1 figure and 1 table

We present the correlations between the spectroscopic metallicities and ninety-three different intrinsic colors of M31 globular clusters, including seventy-eight BATC colors and fifteen SDSS and near infrared ugrizK colors. The BATC colors were derived from the archival images of thirteen filters (from c to p), which were taken by Beijing-Arizona-Taiwan-Connecticut (BATC) Multicolor Sky Survey with a 60/90 cm f/3 Schmidt telescope. The spectroscopic metallicities adopted in our work were from literature. We fitted the correlations of seventy-eight different BATC colors and the metallicities for 123 old confirmed globular clusters, and the result implies that correlation coefficients of twenty-three colors r>0.7. Especially, for the colors $(f-k)_0$, $(f-o)_0$, and $(h-k)_0$, the correlation coefficients are r>0.8. Meanwhile, we also note that the correlation coefficients (r) approach zero for $(g-h)_0$, $(k-m)_0$, $(k-n)_0$, and $(m-n)_0$, which are likely to be independent of metallicity. Similarity, we fitted the correlations of metallicity and ugrizK colors for 127 old confirmed GCs. The result indicates that all these colors are metal-sensitive (r>0.7), of which $(u-K)_0$ is the most metal-sensitive color. Our work provides an easy way to simply estimate the metallicity from colors., Comment: 25 pages, 11 figures, 2 tables, accepted for publication in PASP.

In 2008 January the 24th Chinese expedition team successfully deployed the Chinese Small Telescope ARray (CSTAR) to DomeA, the highest point on the Antarctic plateau. CSTAR consists of four 14.5cm optical telescopes, each with a different filter (g, r, i and open) and has a 4.5degree x 4.5degree field of view (FOV). It operates robotically as part of the Plateau Observatory, PLATO, with each telescope taking an image every 30 seconds throughout the year whenever it is dark. During 2008, CSTAR #1 performed almost flawlessly, acquiring more than 0.3 million i-band images for a total integration time of 1728 hours during 158 days of observations. For each image taken under good sky conditions, more than 10,000 sources down to 16 mag could be detected. We performed aperture photometry on all the sources in the field to create the catalog described herein. Since CSTAR has a fixed pointing centered on the South Celestial Pole (Dec =-90 degree), all the sources within the FOV of CSTAR were monitored continuously for several months. The photometric catalog can be used for studying any variability in these sources, and for the discovery of transient sources such as supernovae, gamma-ray bursts and minor planets., Comment: 1 latex file and 9 figures The paper is accepted by PASP

The Chinese Small Telescope ARray (hereinafter CSTAR) is the first Chinese astronomical instrument on the Antarctic ice cap. The low temperature and low pressure testing of the data acquisition system was carried out in a laboratory refrigerator and on the 4500m Pamirs high plateau, respectively. The results from the final four nights of test observations demonstrated that CSTAR was ready for operation at Dome A, Antarctica. In this paper we present a description of CSTAR and the performance derived from the test observations., Comment: Accepted Research in Astronomy and Astrophysics (RAA) 1 Latex file and 20 figures

The i-band observing conditions at Dome A on the Antarctic plateau have been investigated using data acquired during 2008 with the Chinese Small Telescope ARray. The sky brightness, variations in atmospheric transparency, cloud cover, and the presence of aurorae are obtained from these images. The median sky brightness of moonless clear nights is 20.5 mag arcsec^{-2} in the SDSS $i$ band at the South Celestial Pole (which includes a contribution of about 0.06 mag from diffuse Galactic light). The median over all Moon phases in the Antarctic winter is about 19.8 mag arcsec^{-2}. There were no thick clouds in 2008. We model contributions of the Sun and the Moon to the sky background to obtain the relationship between the sky brightness and transparency. Aurorae are identified by comparing the observed sky brightness to the sky brightness expected from this model. About 2% of the images are affected by relatively strong aurorae., Comment: There are 1 Latex file and 14 figures accepted by AJ

The source J 1128+5925 was found recently to show strong intraday variability at radio wavelengths and its radio variability may come from interstellar scintillation. In optical, the object was quiet in our 2007 monitoring session. Here we report the results of our new optical monitoring of this source in 2008. In addition to confirm our 2007 results, that the object did not display any clear variation on timescales from hour--day to month, we provide evidence that the object does not vary on timescale of one year, and it is probably intrinsically quiet in optical domain. Its very different behaviors in optical and radio regimes can be naturally explained if its strong radio variability comes from interstellar scintillation., Comment: 10 pages, 5 figures, accepted by AJ

Very recently, J 1128+5925 was found to show strong intraday variability at radio wavelengths and may be a new source with annual modulation of the timescale of its radio variability. Therefore, its radio variability can be best explained via interstellar scintillation. Here we present the properties of its optical variability for the first time after a monitoring program in 2007 May. Our observations indicate that in this period J 1128+5925 only showed trivial optical variability on internight timescale, and did not show any clear intranight variability. This behavior is quite different from its strong radio intraday variability. Either this object was in a quiescent state in optical in this period, or it is intrinsically not so active in optical as it is in radio regimes., Comment: 9 pages, 3 figures

This paper is the third in the series of papers on M81 globular clusters. In this paper, we present spatial and metal abundance properties of 95 M81 globular clusters, which comprise nearly half of all the M81 globular cluster system. These globular clusters are divided into two M81 metallicity groups by a KMM test. Our results show that, the metal-rich clusters did not demonstrate a centrally concentrated spatial distribution as ones in M31, and metal-poor clusters tend to be less spatially concentrated. In other words, the distribution of the metal-rich clusters in M81 is not very similar to that of M31. Most of the metal-rich clusters distribute at projected radii of 4-8 kpc. It is also noted that the metal-rich clusters distribute within the inner 20 kpc, and the metal-poor ones do out to radii of ~40 kpc. Like our Galaxy and M31, the metallicity distribution of globular clusters in M81 along galactocentric radius suggests that some dissipation occurred during the formation of the globular cluster system, i.e. smooth, pressure-supported collapse models of galaxies are unlikely to produce such radial distribution of metallicity presented in this paper. There is not evident correlation between globular cluster luminosity and metallicity in M81 globular clusters. The overwhelming conclusion of this paper seems to be that a more complete and thorough cluster search is needed in M81., Comment: Accepted for Publication in PASP, 7 pages, 5 figures, fig 1 in jpg

We at first introduce a novel photometric system, which consists of a Schmidt telescope, an objective prism, a CCD camera, and, especially, a multi-peak interference filter. The multi-peak interference filter enables light in multi passbands to pass through it simultaneously. The light in different passbands is differentially refracted by the objective prism and is focused on the CCD separately, so we have multi "images" for each object on the CCD frames. This system enables us to monitor blazars exactly simultaneously in multi wavebands on a single telescope, and to accurately trace the color change during the variation. We used this novel system to monitor the BL Lacertae object S5 0716+714 during 2006 January and February and achieved a very high temporal resolution. The object was very bright and very active during this period. Two strong flares were observed, with variation amplitudes of about 0.8 and 0.6 mags in the $V'$ band, respectively. Strong bluer-when-brighter correlations were found for both internight and intranight variations. No apparent time lag was observed between the $V'$- and $R'$-band variations, and the observed bluer-when-brighter chromatism may be mainly attributed to the larger variation amplitude at shorter wavelength. In addition to the bluer-when-brighter trend, the object also showed a bluer color when it was more active. The observed variability and its color behaviors are consistent with the shock-in-jet model., Comment: 30 pages, 22 figures, accepted by AJ

Using galaxy sample observed by the BATC large-field multi-color sky survey and galaxy data of SDSS in the overlapped fields, we study the dependence of the restframe $r$-band galaxy luminosity function on redshift and on large-scale environment. The large-scale environment is defined by isodensity contour with density contrast \delta\rho/\rho. The data set is a composite sample of 69,671 galaxies with redshifts 0.03 < z < 0.5 and r < 21.5 mag. The redshifts are composed by three parts: 1) spectroscopic redshifts in SDSS for local and most luminous galaxies; 2) 20-color photometric redshifts derived from BATC and SDSS; 3) 5-color photometric redshifts in SDSS. We find that the faint-end slope \alpha steepens slightly from -1.21 at z ~ 0.06 to -1.35 at z ~ 0.4, which is the natural consequence of the hierarchical formation of galaxies. The luminosity function also differs with different environments. The value of \alpha changes from -1.21 at underdense regions to -1.37 at overdense regions and the corresponding M* brightens from -22.26 to -22.64. This suggests that the fraction of faint galaxies is larger in high density regions than in low density regions., Comment: 7 pages, 9 figures, accepted by ApJ

We present the results of our optical monitoring of the BL Lacertae object OJ 287 during the first half of 2005. The source did not show large-amplitude variations during this period and was in a relatively quiescent state. A possible period of 40 days was derived from its light curves in three BATC wavebands. A bluer-when-brighter chromatism was discovered, which is different from the extremely stable color during the outburst in 1994--96. The different color behaviors imply different variation mechanisms in the two states. We then re-visited the optical data on OJ 287 from the OJ-94 project and found as well a probable period of 40 days in its optical variability during the late-1994 outburst. The results suggest that two components contribute to the variability of OJ 287 during its outburst state. The first component is the normal {\sl blazar} variation. This component has an amplitude similar to that of the quiescent state and also may share a similar periodicity. The second component can be taken as a `low-frequency modulation' to the first component. It may be induced by the interaction of the assumed binary black holes in the center of this object. The 40-day period may be related to the helical structure of the magnetic field at the base of the jet, or to the orbital motion close to the central primary black hole., Comment: 31 pages, 8 figures, accepted by AJ

We present photometric data of the type II-P supernova (SN) 2004dj in NGC 2403. The multicolor light curves cover the SN from $\sim$ 60 to 200 days after explosion, and are measured with a set of intermediate-band filters that have the advantage of tracing the strength variations of some spectral features. The light curves show a flat evolution in the middle of the plateau phase, then decline exponentially at the late times, with a rate of 0.10$\pm$0.03 mag (10 days)$^{-1}$ in most of the filters. In the nebular phase, the spectral energy distribution (SED) of SN 2004dj shows a steady increase in the flux near 6600 \AA and 8500 \AA, which may correspond to the emission lines of H$\alpha$ and Ca II near-IR triplet, respectively. The photometric behavior suggests that SN 2004dj is a normal SN II-P. Compared with the light curves of another typical SN II-P 1999em, we estimate the explosion date to be June 10$\pm$21 UT, 2004 (JD 2453167$\pm$21) for SN 2004dj. We also estimate the ejected nickel mass during the explosion to be $M(^{56}\rm{Ni})$ = 0.023 $\pm$ 0.005 $M_{\odot}$ from two different methods, which is typical for a SN II-P. We derive the explosion energy $E \approx 0.75^{+0.56}_{-0.38}\times10^{51}$ erg, the ejecta mass $M \approx 10.0^{+7.4}_{-5.2}$ $M_{\odot}$, and the initial radius $R \approx 282^{+253}_{-122}$ $R_{\odot}$ for the presupernova star of SN 2004dj, which are consistent with other typical SNe II-P., Comment: 15 pages, 9 figures, accepted for publication in AJ

This paper presents accurate spectral energy distributions (SEDs) of 16 M31 globular clusters (GCs) confirmed by spectroscopy and/or high spatial-resolution imaging, as well as 30 M31 globular cluster candidates detected by Mochejska et al. Most of these candidates have m_V > 18, deeper than previous searches, and these candidates have not yet been confirmed to be globular clusters. The SEDs of these clusters and candidates are obtained as part of the BATC Multicolor Survey of the Sky, in which the spectrophotometrically-calibrated CCD images of M31 in 13 intermediate-band filters from 4000 to 10000 A were observed. These filters are specifically designed to exclude most of the bright and variable night-sky emission lines including the OH forest. In comparison to the SEDs of true GCs, we find that some of the candidate objects are not GCs in M31. SED fits show that theoretical simple stellar population (SSP) models can fit the true GCs very well. We estimate the ages of these GCs by comparing with SSP models. We find that, the M31 clusters range in age from a few ten Myr to a few Gyr old, as well as old GCs, confirming the conclusion that has been found by Barmby et a, Williams & Hodge, Beasley et al., Burstein et al. and Puzia et al. in their investigations of the SEDs of M31 globular clusters., Comment: Accepted for Publication in A&Ap, 13 pages, 6 figures

037-B327 is of interest because it is both the most luminous and the most highly reddened cluster known in M31. Deep observations with the Advanced Camera for Surveys on the Hubble Space Telescope provide photometric data in the F606W band, and also show that this cluster is crossed by a dust lane. We determined the structural parameters of 037-B327 by fitting the observed surface brightness distribution to a King model with r_c=0.72" (=2.69 pc), and r_t=5.87" (=21.93 pc), and a concentration index c=log(r_t/r_c)=0.91. The surface brightness profile appears to be essentially flat within 0.25" of the center and shows no signs of core collapse. Although the dust lane affects the photometry, the King model fits the surface brightness profile well except for the regions badly affected by the dust lane. We also calculate the half-light radius r_h=1.11" (=4.15 pc). Combined with previous photometry, we find that this object falls in the same region of the M_V versus log R_h diagram as do Omega Centauri, M54 and NGC 2419 in the Milky Way and the massive cluster G1 in M31. All four of these objects have been claimed to be the stripped cores of former dwarf galaxies. This suggests that 037-B327 may also be the stripped core of a former dwarf companion to M31., Comment: Accepted for Publication in ApJ Letter, 4 pages, 4 figures

In this paper, we give the spectral energy distributions of 42 M81 globular clusters in 13 intermediate-band filters from 4000 to 10000 A, using the CCD images of M81 observed as part of the BATC multicolor survey of the Sky. The BATC multicolor filter system is specifically designed to exclude most of the bright and variable night-sky emission lines including the OH forest. Hence, it can present accurate SEDs of the observed objects. These spectral energy distributions are low-resolution spectra, and can reflect the stellar populations of the globular clusters. This paper confirms the conclusions of Schroder et al. that, M81 contains clusters as young as a few Gyrs, which also were observed in both M31 and M33, Comment: Accepted for Publication in PASP, 10 pages, 3 figures

This paper includes two parts. The first is to present the spectral energy distributions (SEDs) of 49 globular cluster (GC) X-ray sources in the BATC 13 intermediate-band filters from 3800 to 10000 A, and identify 8 unidentified X-ray sources in M31. Using the X-ray data of Einstein observation from 1979 to 1980, ROSAT HRI observation in 1990, Chandra HRC and ACIS-I observations from 1999 to 2001, and the BATC optical survey from 1995 to 1999, we find 49 GC X-ray sources and 8 new unidentified X-ray sources in the BATC M31 field. By analyzing SEDs and FWHMs, 4 of the 8 X-ray sources may be GC candidates. The second is to present some statistical relationships about 62 GC X-ray sources, of which 58 are already known, and 4 are identified in this paper. The distribution of M31 GC X-ray sources' V mags is bimodal, with peaks at m_v = 15.65 and m_v = 17.89, which is different from the distribution of GC candidates. The distribution of B-V color shows that,the GC X-ray sources seem to be associated preferentially with the redder GCs, in agreement with the previous results. Kolmogorov-Smirnov test shows that the maximum value of the absolute difference of B-V distributions of GC X-ray sources and GCs is D_{max}=0.181, and the probability P=0.068 which means we can reject the hypothesis that the two distributions are the same at the 90.0% confidence level. In the end, we study the correlation between X-ray luminosity (0.3-10 keV) and the optical luminosity (in V band) of the GC X-ray sources in M31, and find that there exits a weak relationship with the linear correlation coefficient r = 0.36 at the confidence level of 98.0%., Comment: Accepted for publication in the November 2005 issue of the PASP. 19 pages, 8 figures including 2 jpg figures

In this paper we present catalogs of photometric and spectroscopic data for M81 globular clusters (GCs). The catalogs include B- and V- photometric and reddening data of 95 GCs, and spectroscopic metallicities of 40 GCs in M81. Using these data, we make some statistical correlations. The results show that the distributions of intrinsic B and V colors and metallicities are bimodal, with metallicity peaks at [Fe/H]=-1.45 and -0.53, respectively as has been demonstrated for our Milky Way and M31. The relation between spectroscopic metallicity and intrinsic B and V color also exists as it does for the Milky Way and M31., Comment: Accepted for Publication in PASP, 9 pages, 6 figures

Optical monitoring of S5 0716+714 was performed with a 60/90 Schmidt telescope in 2003 November and December and 2004 January for studying the variability of the object on short timescales. Due to the high brightness of the source we could carry out quasi-simultaneous measurements in three bands with a temporal resolution of about 20 minutes by using one single telescope. Intraday and intranight variations were observed with an overall change of ~0.9 mag during the whole campaign. Two outbursts were recorded on JD 2453005 and JD 2453009. Minimum timescales of a few hours were derived from the light curves of individual nights but were different from night to night. A bluer-when-brighter chromatism was present when the object was in fast flare, but was absent when it was in a relatively quiescent state. Our results are basically consistent with the shock-in-jet model and demonstrate that the geometrical effects can sometimes play an important role in the variability of blazars., Comment: 39 pages, 6 figures, to be published in AJ

In this paper, the late-time optical photometry of supernova (SN) 1993J in M81 from Feburary 1995 to Janurary 2003 is presented. The observations were performed in a set of intermediate-band filters that have the advantage of tracing the strength variations of some spectral features. SN 1993J was found to fade very slowly at late times, declining only by $0.05\pm0.02$ mag 100 d$^{-1}$ in most of the filters from 2 to nearly 10 yrs after discovery. Our data suggest that the circumstellar interaction provides most of the energy to power the late-time optical emission of SN 1993J. This is manifested by several flux peaks seen in the rough spectral energy distributions constructed from the multicolor light curves. The flux peaks near 6600 \AA, 5800 \AA{} and 4900 \AA{} may correspond to the emission lines of H$\alpha$, Na I D + He I $\lambda$5876 and [O III] $\lambda\lambda$4959, 5007, respectively. The evolution of these emission lines suggest a power-law SN density model as proposed by \citet{cf94}., Comment: 24 pages, 7 figures, accepted for publication in AJ

We present optical candidates for 75 X-ray sources in a $\sim 1$ deg$^2$ overlapping region with the medium deep ROSAT survey. These candidates are selected using the multi-color CCD imaging observations made for the T329 field of the Beijing-Arizona-Taipei-Connecticut (BATC) Sky Survey. These X-ray sources are relatively faint (CR $<< 0.2 s^{-1}$) and thus mostly are not included in the RBS catalog, they also remain as X-ray sources without optical candidates in a previous identification program carried out by the Hamburg Quasar Survey. Within their position-error circles, almost all the X-ray sources are observed to have one or more spatially associated optical candidates within them down to the magnitude $m_V \sim 23.1$. We have classified 149 of 156 detected optical candidates with 73 of the 75 X-ray sources with a SED-based Object Classification Approach (SOCA). These optical candidates include: 31 QSOs, 39 stars, 37 starburst galaxies, 42 galaxies, and 7 "just" visible objects. We have also cross-correlated the positions of these optical objects with NED, the FIRST radio source catalog and the 2MASS catalog. Separately, we have also SED-classified the remaining 6011 objects in our field of view. Optical objects are found at the $6.5\sigma$ level above what one would expect from a random distribution, only QSOs are over-represented in these error circles at greater than 4$\sigma$ frequency. We estimate redshifts for all extragalactic objects, and find a good correspondence of our predicted redshift with the measured redshift (a mean error of 0.04 in $\Delta z$. There appears to be a supercluster at z $\sim$ 0.3-0.35 in this direction, including many of the galaxies in the X-ray error circles are found in this redshift range., Comment: 45 pages, 21 figures, AJ in press, Version with full resolution figures available from http://www.lamost.org/~zht/xray.zip

This paper presents a multicolor study of the nearby cluster of galaxies Abell 168 (z=0.045) with 13 intermediate-band filters in the Beijing-Arizona-Taiwan-Connecticut (BATC) filter system. After a cross-identification between the photometric data obtained from the BATC and the Sloan Digital Sky Survey (SDSS), a catalog containing 1553 galaxies down to r'<20.0 mag is achieved, which includes 121 spectroscopically confirmed member galaxies. The technique of photometric redshift has been applied to all these galaxies with combined 18-band (13 from BATC and 5 from SDSS) spectral energy distributions (SEDs), in order to perform a faint membership selection in Abell 168. As a result, 255 galaxies are newly selected as the member candidates. Based on the enlarged sample of cluster galaxies, the spatial distribution and dynamics of Abell 168 are investigated. In the light of the spatial distribution of the member galaxies and the 0.2-3.5 keV X-ray image by Einstein observatory, it seems that Abell 168 consists of two merging subclusters with a relative radial velocity of 264 +/- 142 km/s. With the help of ROSTAT software, a detailed investigation of the dynamics shows the intrinsic difference in the velocity distributions for these two subclusters. Under a linear two-body model, they are found to be a gravitationally bound system with 92% probability. The slight deviation of the local velocity distribution from the overall distribution in the central region may suggest a picture of head-on collision in the projection plane. By using a double Schechter function, the close examination of the luminosity functions reveals the different galaxy content of these two subclusters, which implies the merging process is possibly at the early stage., Comment: 26 pages, 10 figures, accepted by ApJ

We present our optical multicolor photometry for the nearby cluster of galaxies Abell 2255 with 13 intermediate filters in the BATC system. The spectral energy distributions (SEDs) in the optical band for more than 7000 sources are achieved down to V ~ 20 in a field of 58' x 58' centered on this rich cluster. Abell 2255 has been recently observed by the SDSS. A method of combining the SDSS photometric data in five broad bands and the BATC SEDs is then explored. The application of the technique of photometric redshift shows that the combined SEDs with higher resolution could lead to a more accurate estimate of photometric redshift. Based on 214 spectroscopically confirmed member galaxies, the bimodality and large dispersion in the velocity distribution indicate that Abell 2255 is an unrelaxed system. A tight color-magnitude correlation for 188 known early-type cluster galaxies is found. After an exclusion of 254 extragalactic sources with known redshifts, the combined SEDs for 2522 galaxies allow a further membership selection by the photometric redshift technique and color-magnitude correlation. As a result, 313 galaxies with their photometric redshifts between 0.068 and 0.090 are selected as new cluster members. The combined SEDs and estimated redshifts for previously known and newly-selected member galaxies are cataloged. On the basis of the enlarged sample of member galaxies, the spatial distribution, localized velocity structure, color-magnitude relation, and luminosity function of cluster galaxies are discussed. The reverse peculiar velocities are found for two satellite subclusters located on opposite sides of the central concentration, which supports an ongoing merger in Abell 2255., Comment: 37 pages, including 13 figures and 6 tables, Accepted by the ApJS

We report the first results of star counts carried out with the National Astronomical Observatories (NAOC) 60/90 cm Schmidt Telescope in 15 intermediate-band filters from 3000 to 10000 {\AA} in the BATC survey. We analyze a sample of over 1400 main sequence stars ($14\le$V$\le21$), which lie in the field with central coordinates R.A.=$09^h53^m13^s.30$ and DEC=47$^\circ49^{\prime}00^{\prime\prime}.0$ (J2000). The field of view is 0.95 deg$^{2}$, and the spatial scale was $1\arcsec.67$. In our model, the distribution of stars perpendicular to the plane of the Galaxy is given by two exponential disks (thin disk plus thick disk) and a de Vaucouleurs halo. Based on star counts, we derive the scale heights of the thin disk to be $320^{+14}_{-15}$ pc and of the thick disk to be $640^{+30}_{-32}$ pc, respectively, with a local density of $7.0\pm1%$ of the thin disk. We find that the observed counts support an axial ratio of $c/a\le0.6$ for a de Vaucouleurs $r^{1/4}$ law, implying a more flattened halo. We also derive the stellar luminosity function (SLF) for the thin disk, and it partly agrees with the Hipparcos luminosity function., Comment: 17pages,9 figures

This paper is the fourth in a series presenting spectrophotometry of 51 globular cluster candidates, that were detected by Mochejska et al. in the nearby galaxy M33 using the data collected by the DIRECT project. The frames of M33 in this study were taken as part of the BATC Multicolor Sky Survey. We obtained the spectral energy distributions of these candidates in 13 intermediate-band filters. By comparing the integrated photometric measurements with theoretical stellar population synthesis models of Bruzual & Charlot, we estimated their ages. The BC96 models provide the evolution in time of the spectrophotometric properties of simple stellar populations for a wide range of stellar metallicity. Our results show that half of the candidates are younger than 10^8 years, whose age degeneracy is not pronounced. We also find that globular clusters formed continuously in M33 from ~4*10^6 -- 10^{10} years. Our results are in agreement with Chandar et al., who estimated ages for 35 globular clusters candidates in common by comparing the photometric measurements to integrated colors from theoretical models by Bertelli et al. The Kolmogorov-Smirnov Test shows that the maximum value of the absolute difference of estimated ages between Chandar et al. and us is 0.48, and the significance level probability is 100.00 per cent., Comment: 20 pages, has been accepted for publication to Acta Astronomica in Poland

In this paper we present CCD multicolor photometry for 172 globular clusters (GCs), taken from the Bologna catalog (Battistini et al. 1987), in the nearby spiral galaxy M31. The observations were carried out by using the National Astronomical Observatories 60/90 cm Schmidt Telescope in 13 intermediate-band filters, which covered a range of wavelength from 3800 to 10000A. This provides a multicolor map of M31 in pixels of 1.7"*1.7". By aperture photometry, we obtain the spectral energy distributions (SEDs) for these GCs. Using the relationship between the BATC intermediate-band system used for the observations and the UBVRI broad-band system, the magnitudes in the B and V bands are derived. The computed V and B-V are in agreement with the values given by Battistini et al. (1987) and Barmby et al. (2000). Finally, by comparing the photometry of each GC with theoretical stellar population synthesis models, we estimate ages of the sample GCs for different metallicities. The results show that nearly all our sample GCs have ages more than 10^{9} years, and most of them are around 10^{10} years old. Also, we find that GCs fitted by the metal-poor model are generally older than ones fitted by the metal-rich model., Comment: 38 pages, 7 figures will appear in the February 2003 issue of AJ

In this paper, we present the methodology of photometric redshift determination with the BATC 15-color system by using hyperz program. Both simulated galaxies and real galaxies with known redshifts were used to estimate the accuracy of redshifts inferred from the multicolor photometry. From the test with simulated galaxies, the uncertainty in the inferred redshifts is about $0.02\sim0.03$ for a given range of photometric uncertainty of $0.05 \sim 0.10$. The results with the 27 real galaxies are in good agreement with the simulated ones. The advantage of using BATC intermediate-band system to derive redshift is clear through the comparison with the UBVRI broad-band system. The accuracy in redshift determination with BATC system is mainly affected by the selection of filters and the photometric uncertainties in the observation. When we take the limiting magnitudes of the 15 filters into account, we find that redshift can be determined with good accuracy for galaxies with redshifts less than 0.5, using only filters with central wavelengths shorter than 6000 A., Comment: 22 pages, accepted for publishing by PASP

In this paper, we present a set of photometric observations in 15 colors of stars in the Landolt covered by the system range from 300 nm to 1000 nm. Visual magnitudes of the stars being studied in the field are from 10th to 20th mag. The observational methodology and the data reduction procedures are described. The relationships between the BATC intermediate-band system and the Landolt UBVRI broad band system are obtained. A catalogue of the photometry has been produced which contains the SEDs of 3613 stars. The electronic form of this catalogue can be accessed at the CDS via anonymous ftp to cdsarc.u-strasbg.fr., Comment: 21 pages, accepted for publishing by A&A

This paper is the first in a series presenting CCD multicolor photometry for 145 HII regions, selected from 369 candidate regions from Boulesteix et al. (1974), in the nearby spiral galaxy M33. The observations, which covered the whole area of M33, were carried out by the Beijing Astronomical Observatory 60/90 cm Schmidt Telescope, in 13 intermediate-band filters, covering a range of wavelength from 3800 to 10000 A. This provides a series of maps which can be converted to a multicolor map of M33, in pixels of 1.7''*1.7''. Using aperture photometry we obtain the spectral energy distributions (SEDs) for these HII regions. We also give their identification charts. Using the relationship between the BATC intermediate-band system used for the observations and the UBVRI broad-band system, the magnitudes in the B and V bands are then derived. Histograms of the magnitudes in V and in B-V are plotted, and the color-magnitude diagram is also given. The distribution of magnitudes in the V band shows that the apparent magnitude of almost all the regions is brighter than 18, corresponding to an absolute magnitude of -6.62 for an assumed distance modulus of 24.62, which corresponds to a single main sequence O5 star, while the distribution of color shows that the sample is blue, with a mode close to -0.05 as would be expected from a range of typical young clusters., Comment: 34 pages, 19 figures including 16 of jpg form, will appear in the December 2002 issue of AJ

In this third paper of our series, we present CCD spectrophotometry of 78 star clusters that were detected by Chandar, Bianchi, & Ford in the nearby spiral galaxy M33. CCD images of M33 were obtained as a part of the BATC Color Survey of the sky in 13 intermediate-band filters from 3800 to 10000{\AA}. By aperture photometry, we obtain the spectral energy distributions of these 78 star clusters. As Chandar, Bianchi, & Ford did, we estimate the ages of our sample clusters by comparing the photometry of each object with theoretical stellar population synthesis models for different values of metallicity. We find that the sample clusters formed continuously in M33 from $\sim 3\times10^6$ -- $10^{10}$ years. This conclusion is consistent with Chandar, Bianchi, & Ford. The results also show that, there are two peaks in cluster formation, at $\sim 8\times10^6$ and $\sim 10^9$ years in these clusters., Comment: 29 pages, one figure is gif form, will appear in the June 2002 issue of AJ

In this paper we study the properties of ten halo globular clusters in the nearby spiral galaxy M33. CCD images of M33 were obtained as a part of the BATC Colour Survey of the sky in 13 intermediate-band filters from 3800 to 10000{\AA}. By aperture photometry, we obtain the spectral energy distributions (SEDs) of these globular clusters. We estimate the ages of our sample clusters by comparing the photometry of each object with theoretical stellar population synthesis models for different values of metallicity. Our results suggest that eight of the ten sample halo globular clusters have ``intermediate'' ages, i.e. between 1 and 8 Gyrs., Comment: 9 pages, 3 figures, has been accepted for publication in Astronomy and Astrophysics

An optical photometric observation with the BATC multicolor system is carried out for the central 56' x 56' region of the nearby cluster of galaxies, Abell 2634. We achieved the spectral energy distributions (SEDs) of 5572 sources detected down to $V \sim 20$ mag, including 178 previously known galaxies, with fourteen filters covering a wavelength range from 3600 \AA\ to 10000 \AA. After excluding the foreground and background galaxies, a sample of 124 known members is formed for an investigation of the SED properties. Based on the knowledge of SED properties of member galaxies, we performed the selection of faint galaxies belonging to Abell 2634. The color-color diagrams are powerful in the star/galaxy separation, and 359 faint galaxies are selected by their color features. The technique of photometric redshift and color-magnitude correlation for the early-type galaxies are applied for these faint galaxies, and a list of 74 faint member galaxies is achieved. Basis on the enlarged sample of member galaxies, the spatial distribution and color-magnitude relation of the galaxies in core region of Abell 2634 are discussed. We find a tendency that the color index dispersion of the early-type members is larger for the outer region, which might reflect some clues about the environmental effect on the evolution of galaxies in a cluster., Comment: 35 pages, 21 Postscript figures and tables, LaTeX, using aasms4.sty

In this paper we present CCD spectrophotometry of the star clusters that were detected by Chandar, Bianchi, & Ford in the nearby spiral galaxy M33, using the images obtained with the Beijing Astronomical Observatory 60/90 cm Schmidt Telescope in 13 intermediate-band filters from 3800 to 10000{\AA}. The observations cover the whole area of M33 with a total integration of 32.75 hours from September 23, 1995 to August 28, 2000. This provides a multi-color map of M33 in pixels of $1.7'' \times 1.7''$. By aperture photometry, we obtain the spetral energy distributions (SEDs) of these star clusters. Using theoretical stellar population synthesis models, we also obtain the distributions of age and metallicity of of these star clusters. These clusters formed continuously from $\sim 3\times10^6$ -- $10^{10}$ years, and have a large span of metallicity from ${\rm {Z}=0.0004}$ to ${\rm {Z}=0.05}$., Comment: 29 pages, 7 figures, will appear in the October 2001 issue of AJ