The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST, also called the Guo Shou Jing Telescope) is a special reflecting Schmidt telescope. LAMOST's special design allows both a large aperture (effective aperture of 3.6 m-4.9 m) and a wide field of view (FOV) (5 • ). It has an innovative active reflecting Schmidt configuration which continuously changes the mirror's surface that adjusts during the observation process and combines thin deformable mirror active optics with segmented active optics. Its primary mirror (6.67 m×6.05 m) and active Schmidt mirror (5.74 m×4.40 m) are both segmented, and composed of 37 and 24 hexagonal sub-mirrors respectively. By using a parallel controllable fiber positioning technique, the focal surface of 1.75 m in diameter can accommodate 4000 optical fibers. Also, LAMOST has 16 spectrographs with 32 CCD cameras. LAMOST will be the telescope with the highest rate of spectral acquisition. As a national large scientific project, the LAMOST project was formally proposed in 1996, and approved by the Chinese government in 1997. The construction started in 2001, was completed in 2008 and passed the official acceptance in June 2009. The LAMOST pilot survey was started in October 2011 and the spectroscopic survey will launch in September 2012. Up to now, LAMOST has released more than 480 000 spectra of objects. LAMOST will make an important contribution to the study of the large-scale structure of the Universe, structure and evolution of the Galaxy, and cross-identification of multiwaveband properties in celestial objects.

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

This paper describes the data release of the LAMOST pilot survey, which includes data reduction, calibration, spectral analysis, data products and data access. The accuracy of the released data and the information about the FITS headers of spectra are also introduced. The released data set includes 319 000 spectra and a catalog of these objects.

All stellar mass black holes have hitherto been identified by X-rays emitted by gas that is accreting onto the black hole from a companion star. These systems are all binaries with black holes below 30 M ⊙ 1-4. Theory predicts, however, that X-ray emitting systems form a minority of the total population of star-black hole binaries 5, 6. When the black hole is not accreting gas, it can be found through radial velocity measurements of the motion of the companion star. Here we report radial velocity measurements of a Galactic star, LB-1, which is a B-type star, taken over two years. We find that the motion of the B-star and an accompanying Hα emission line require the presence of a dark companion with a mass of

We use a large sample of galaxy groups selected from the SDSS data release 4 with an adaptive halo-based group finder to probe how the clustering strength of groups depends on their masses and colors. In particular, we determine the relative biases of groups of different masses, as well as that of groups with the same mass but with different colors (either that of the central galaxy, or the total color of all group members). In agreement with previous studies, we find that more massive groups are more strongly clustered, and the inferred mass dependence of the halo bias is in good agreement with predictions for the ΛCDM concordance cosmology. Regarding the color dependence, we find that groups with red centrals are more strongly clustered than groups of the same mass but with blue centrals. Similar results are obtained when the color of a group is defined to be the total color of its member galaxies. The color dependence is more prominent in less massive groups and becomes insignificant in groups with masses > ∼ 10 14 h −1 M ⊙ . These results are consistent with those obtained by Yang et al. from an analysis of the 2dFGRS, but inconsistent with those obtained by Berlind et al. , who also used an SDSS group catalogue. We construct a mock galaxy redshift survey from the large Millennium N -body simulation that is populated with galaxies according to the semi-analytical model of Croton et al. Applying our group finder to this mock survey, and analyzing the mock data in exactly the same way as the true data, we are able to accurately recover the intrinsic mass and color dependencies of the halo bias in the model. Interestingly, the semi-analytical model reveals the same color dependence of the halo bias as we find in our group catalogue. In halos with M ∼ 10 12 h −1 M ⊙ , though, the strength of the color dependence is much stronger in the model than in the data. We discuss these results in light of the assembly bias of dark matter halos and the star formation histories of galaxies. Subject headings: dark matter -large-scale structure of the universe -galaxies: halos

We report redshift measurements of 5 X-ray emitting blue stellar objects (BSO's) located less than 12 arc min from the X-ray Seyfert galaxy, NGC 3516.We find these quasars to be distributed along the minor axis of the galaxy and to show a very good correlation between their redshift and their angular distance from NGC 3516. Moreover the redshifts of these 5 quasars are: 0.33, 0.69, 0.93, 1.40 and 2.10 which are very near the peaks of the redshift periodicity distribution (i.e. z = 0.3, 0.6, 0.96, 1.41 and 1.96). All these observed properties strikingly confirm, around this single example of a Seyfert, the composite picture derived from previous physical associations of quasars with low redshift, active galaxies.Subject headings: quasars: general -Seyfert galaxies Recently H.-D. Radecke (1997) has presented evidence that there is a significant (minimum of 7.4 sigma) excess of bright X-ray sources around a nearly complete sample of Seyfert galaxies. Arp (1997) had inspected each individual X-ray map of 24 Seyfert galaxies with an apparent magnitude between 8.04 ≤ B 0,i T ≤ 12.90 mag. and found that on Schmidt Survey plates most of these excess X-ray sources are identified with blue stellar objects (BSO). These X-ray emitting BSO's generally show pairing and alignment configurations cross the central Seyfert galaxies.We have started a program to obtain the optical spectra of these X-ray emitting BSO's. Herewith we present our result in the field NGC3516. NGC3516 is a strong X-ray Seyfert galaxy, with apparent magnitude V=12.40 and redshift z=0.009. In Radecke's Seyfert sample, NGC3516 belongs to the faintest and most distant category. X-ray sources

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We study the power spectrum estimator based on the discrete wavelet transform (DWT) for threedimensional samples. The DWT estimator for higher than one-dimensional samples provides two types of spectra with respect to diagonal and o †-diagonal modes, respectively. The two types of modes have di †erent spatial invariance, and therefore the diagonal and o †-diagonal DWT power spectra are very Ñexible for dealing with conÐguration-related problems in power spectrum detection. With simulation samples and the mock catalogs of the Las Campanas Redshift Survey (LCRS), we show that (1) the slicelike geometry of the LCRS does not a †ect the o †-diagonal power spectrum with a "" slicelike ÏÏ mode ; (2) the Poisson sampling with the LCRS selection function does not cause more than 1 p error in the DWT power spectrum ; and (3) the powers of the mass or galaxy random velocity Ñuctuations, which cause the redshift distortion, are approximately scale-independent. These results ensure that the uncertainties of the power spectrum measurement are under control. The scatter of the DWT power spectra of the six strips of the LCRS survey is found to be rather small, less than 1 p of the cosmic variance of the mock sample in the wavenumber range 0.1 \ k \ 2 h Mpc~1. To Ðt the detected LCRS diagonal DWT power spectrum with CDM models, we Ðnd that the best-Ðtting redshift distortion parameter b is about the same as that obtained from the Fourier power spectrum. The velocity dispersions for SCDM and p v "CDM models are also consistent with other detections with the LCRS. A systematic di †erence p v between the best-Ðtting parameters of diagonal and o †-diagonal power spectra have been signiÐcantly measured. This indicates that the o †-diagonal power spectra are capable of providing information about the power spectrum of the galaxy velocity Ðeld.