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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/gray nights to cover an area of about 5400 deg2 in the g and r bands. The 5 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.

M31 globular cluster B379 is the first extragalactic cluster whose age was determined by main-sequence photometry. In the main-sequence photometric method, the age of a cluster is obtained by fitting its color-magnitude diagram (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. constrained the age of B379 by comparing its CMD with isochrones of the 2006 VandenBerg models. Using SSP models of Bruzual & Charlot and its multiphotometry, ZMa et al. independently determined the age of B379, which is in good agreement with the determination of Brown et al. The models of Bruzual & Charlot are calculated based on the Padova evolutionary tracks. It is necessary to check whether the age of B379 as determined based on the Padova evolutionary tracks is in agreement with the determination of Brown et al.. In this article, we redetermine the age of B379 using isochrones of the Padova stellar evolutionary models. In addition, the metal abundance, the distance modulus, and the reddening value for B379 are reported. The results obtained are consistent with the previous determinations, which include the age obtained by Brown et al. This article thus confirms the consistency of the age scale of B379 between the Padova isochrones and the 2006 VandenBerg isochrones; i.e., the comparison between the results of Brown et al. and Ma et al. is meaningful. The results reported in this article of values found for B379 are: metallicity[M/H] = log(Z/Z ⊙) = -0.325 [ M / H ] = log ( Z / Z ⊙ ) = - 0.325 , ageτ = 11.0 ± 1.5 Gyr τ = 11.0 ± 1.5     Gyr , reddening E(B - V) = 0.08 E ( B - V ) = 0.08 , and distance modulus(m - M)0 = 24.44 ± 0.10 ( m - M ) 0 = 24.44 ± 0.10 .

In 2008 January the twenty-fourth Chinese expedition team successfully deployed the Chinese Small Telescope ARray (CSTAR) to Dome A, the highest point on the Antarctic plateau. CSTAR consists of four 14.5 cm optical telescopes, each with a different filter ( g g , r r , i i , and open) and has a4.5° × 4.5° 4.5 ° × 4.5 ° field of view (FOV). It operates robotically as part of the Plateau Observatory, PLATO, with each telescope taking an image every∼30 s ∼ 30   s throughout the year whenever it is dark. During 2008, CSTAR 1 performed almost flawlessly, acquiring more than 0.3 million i i -band images for a total integration time of 1728 hr during 158 days of observations. For each image taken under good sky conditions, more than 10,000 sources down to∼16th ∼ 16 th magnitude 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 (decl. = -90° decl . = - 90 ° ), 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.

We present the correlations between the spectroscopic metallicities and 93 different intrinsic colors of M31 globular clusters, including 78 Beijing-Arizona-Taiwan-Connecticut (BATC) Multicolor Sky Survey colors and 15 SDSS and near-infrared ugrizK u g r i z K colors. The BATC colors were derived from the archival images of 13 filters (from c c to p p ) taken by the Beijing-Arizona-Taiwan-Connecticut Multicolor Sky Survey with a60/90 cm 60 / 90     cm f/3 Schmidt telescope. The spectroscopic metallicities adopted in our work were from literature. We fitted the correlations of 78 different BATC colors and the metallicities for 123 old confirmed globular clusters, and the result implies that correlation coefficients ( r r ) of 23 colors r > 0.7 r > 0.7 . For the colors(f - k)0 ( f - k ) 0 ,(f - o)0 ( f - o ) 0 , and(h - k)0 ( h - k ) 0 , the correlation coefficients are r > 0.8 r > 0.8 . Meanwhile, we also note that the correlation coefficients approach zero for(g - h)0 ( g - h ) 0 ,(k - m)0 ( k - m ) 0 ,(k - n)0 ( k - n ) 0 , and(m - n)0 ( m - n ) 0 , which are likely to be independent of metallicity. Similarity, we fitted the correlations of metallicity and ugrizK u g r i z K colors for 127 old confirmed GCs. The result indicates that all these colors are metal-sensitive ( r > 0.7 r > 0.7 ), and(u - K)0 ( u - K ) 0 is the most metal-sensitive color. Our work provides a simple way to estimate the metallicity from colors.

This paper is the third in a 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 the entire 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 the way the clusters in M31 do, 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. The quick histogram shows that most of the metal‐rich clusters are distributed at projected radii of 4–8 kpc. Note also that the metal‐rich clusters are distributed within the inner 20 kpc, and the metal‐poor ones, out to radii of ∼40 kpc. Like our Galaxy and M31, the metallicity distribution of globular clusters in M81 along a 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 the type of radial distribution of metallicity presented in this paper. There is no 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.

This paper includes two parts. The first presents the spectral energy distributions (SEDs) of 49 globular cluster (GC) X‐ray sources in 13 BATC (Beijing‐Arizona‐Taiwan‐Connecticut) intermediate‐band filters from 3800 to 10000 Å, and identifies 8 previously unidentified X‐ray sources in M31. Using X‐ray data fromEinsteinobservations from 1979 to 1980,ROSATHigh Resolution Imager observations in 1990,ChandraHigh Resolution Channel 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 X‐ray sources in the BATC M31 field. By analyzing SEDs and FWHMs, we determine that 4 of the 8 X‐ray sources may be GC candidates. The second part presents some statistical relationships between 62 GC X‐ray sources, of which 58 are already known and 4 are identified in this paper. The distribution of M31's GC X‐ray sources’Vmagnitudes is bimodal, with peaks at \\documentclass{aastex} \\usepackage{amsbsy} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{bm} \\usepackage{mathrsfs} \\usepackage{pifont} \\usepackage{stmaryrd} \\usepackage{textcomp} \\usepackage{portland,xspace} \\usepackage{amsmath,amsxtra} \\usepackage[OT2,OT1]{fontenc} \\newcommand\\cyr{ \\renewcommand\\rmdefault{wncyr} \\renewcommand\\sfdefault{wncyss} \\renewcommand\\encodingdefault{OT2} \\normalfont \\selectfont} \\DeclareTextFontCommand{\\textcyr}{\\cyr} \\pagestyle{empty} \\DeclareMathSizes{10}{9}{7}{6} \\begin{document} \\landscape $m_{v}=15.65$ \\end{document} and 17.89, which is different from the distribution of GC candidates. The distribution of \\documentclass{aastex} \\usepackage{amsbsy} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{bm} \\usepackage{mathrsfs} \\usepackage{pifont} \\usepackage{stmaryrd} \\usepackage{textcomp} \\usepackage{portland,xspace} \\usepackage{amsmath,amsxtra} \\usepackage[OT2,OT1]{fontenc} \\newcommand\\cyr{ \\renewcommand\\rmdefault{wncyr} \\renewcommand\\sfdefault{wncyss} \\renewcommand\\encodingdefault{OT2} \\normalfont \\selectfont} \\DeclareTextFontCommand{\\textcyr}{\\cyr} \\pagestyle{empty} \\DeclareMathSizes{10}{9}{7}{6} \\begin{document} \\landscape $B-V$ \\end{document} color shows that the GC X‐ray sources seem to be associated preferentially with the redder GCs, in agreement with previous results. Kolmogorov‐Smirnov test shows that the maximum value of the absolute difference of \\documentclass{aastex} \\usepackage{amsbsy} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{bm} \\usepackage{mathrsfs} \\usepackage{pifont} \\usepackage{stmaryrd} \\usepackage{textcomp} \\usepackage{portland,xspace} \\usepackage{amsmath,amsxtra} \\usepackage[OT2,OT1]{fontenc} \\newcommand\\cyr{ \\renewcommand\\rmdefault{wncyr} \\renewcommand\\sfdefault{wncyss} \\renewcommand\\encodingdefault{OT2} \\normalfont \\selectfont} \\DeclareTextFontCommand{\\textcyr}{\\cyr} \\pagestyle{empty} \\DeclareMathSizes{10}{9}{7}{6} \\begin{document} \\landscape $B-V$ \\end{document} distributions of GC X‐ray sources and GCs is \\documentclass{aastex} \\usepackage{amsbsy} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{bm} \\usepackage{mathrsfs} \\usepackage{pifont} \\usepackage{stmaryrd} \\usepackage{textcomp} \\usepackage{portland,xspace} \\usepackage{amsmath,amsxtra} \\usepackage[OT2,OT1]{fontenc} \\newcommand\\cyr{ \\renewcommand\\rmdefault{wncyr} \\renewcommand\\sfdefault{wncyss} \\renewcommand\\encodingdefault{OT2} \\normalfont \\selectfont} \\DeclareTextFontCommand{\\textcyr}{\\cyr} \\pagestyle{empty} \\DeclareMathSizes{10}{9}{7}{6} \\begin{document} \\landscape $D_{\\mathrm{max}\\,}=0.181$ \\end{document} , and the probability \\documentclass{aastex} \\usepackage{amsbsy} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{bm} \\usepackage{mathrsfs} \\usepackage{pifont} \\usepackage{stmaryrd} \\usepackage{textcomp} \\usepackage{portland,xspace} \\usepackage{amsmath,amsxtra} \\usepackage[OT2,OT1]{fontenc} \\newcommand\\cyr{ \\renewcommand\\rmdefault{wncyr} \\renewcommand\\sfdefault{wncyss} \\renewcommand\\encodingdefault{OT2} \\normalfont \\selectfont} \\DeclareTextFontCommand{\\textcyr}{\\cyr} \\pagestyle{empty} \\DeclareMathSizes{10}{9}{7}{6} \\begin{document} \\landscape $P=0.068$ \\end{document} , which means we can reject the hypothesis that the two distributions are the same at the 90.0% confidence level. Finally, we study the correlation between X‐ray luminosity (0.3–10 keV) and optical luminosity (in theVband) of the GC X‐ray sources in M31, and find that there exits a weak relationship with the linear correlation coefficient \\documentclass{aastex} \\usepackage{amsbsy} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{bm} \\usepackage{mathrsfs} \\usepackage{pifont} \\usepackage{stmaryrd} \\usepackage{textcomp} \\usepackage{portland,xspace} \\usepackage{amsmath,amsxtra} \\usepackage[OT2,OT1]{fontenc} \\newcommand\\cyr{ \\renewcommand\\rmdefault{wncyr} \\renewcommand\\sfdefault{wncyss} \\renewcommand\\encodingdefault{OT2} \\normalfont \\selectfont} \\DeclareTextFontCommand{\\textcyr}{\\cyr} \\pagestyle{empty} \\DeclareMathSizes{10}{9}{7}{6} \\begin{document} \\landscape $r=0.36$ \\end{document} at a confidence level of 98.0%.

In this paper we present catalogs of photometric and spectroscopic data for globular clusters (GCs) in M81. The catalogs includeB‐ andV‐band photometric and reddening data of 95 GCs, in addition to spectroscopic metallicities of 40 GCs. Using these data, we make some statistical correlations. The results show that the distributions of intrinsicBandVcolors and metallicities are bimodal, with metallicity peaks at \\documentclass{aastex} \\usepackage{amsbsy} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{bm} \\usepackage{mathrsfs} \\usepackage{pifont} \\usepackage{stmaryrd} \\usepackage{textcomp} \\usepackage{portland,xspace} \\usepackage{amsmath,amsxtra} \\usepackage[OT2,OT1]{fontenc} \\newcommand\\cyr{ \\renewcommand\\rmdefault{wncyr} \\renewcommand\\sfdefault{wncyss} \\renewcommand\\encodingdefault{OT2} \\normalfont \\selectfont} \\DeclareTextFontCommand{\\textcyr}{\\cyr} \\pagestyle{empty} \\DeclareMathSizes{10}{9}{7}{6} \\begin{document} \\landscape $[ \\mathrm{Fe}\\,/ \\mathrm{H}\\,] \\approx -1.45$ \\end{document} and −0.53, respectively, as has been demonstrated for our Milky Way and M31. The relation between spectroscopic metallicity and intrinsicBandVcolor also exists as it does for the Milky Way and M31.

In this paper, we give the spectral energy distributions (SEDs) of 42 M81 globular clusters in 13 intermediate‐band filters from 4000 to 10000 Å using the CCD images of M81, observed as part of the Beijing‐Arizona‐Taiwan‐Connecticut (BATC) Multicolor Sky Survey. 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 SEDs 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 Gyr, which were also observed in both M31 and M33.

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/gray nights to cover an area of about 5400 deg² in the g and r bands. The 5σ 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.

The South Galactic Cap u-band Sky Survey (SCUSS) provides a deep u-band imaging of about 5000 deg2 in south Galactic cap. It is about 1.5 mag deeper than the SDSS u-band. In this article, 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 that uses only 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.