As a major component of the LAMOST Galactic surveys, the LAMOST Spectroscopic Survey of the Galactic Anticentre (LSS-GAC) aims to survey a significant volume of the Galactic thin/thick discs and halo ...for a contiguous sky area of over 3400 deg2 centred on the Galactic anticentre (|b| ≤ 30°, 150 ≤ l ≤ 210°), and obtain λλ3700–9000 low-resolution (R ∼ 1800) spectra for a statistically complete sample of ∼3 M stars of all colours down to a limiting magnitude of r ∼ 17.8 mag (to 18.5 mag for limited fields). Together with Gaia, the LSS-GAC will yield a unique data set to advance our understanding of the structure and assemblage history of the Galaxy, in particular its disc(s). In addition to the main survey, the LSS-GAC will also target hundreds of thousands objects in the vicinity fields of M 31 and M 33 and survey a significant fraction (over a million) of randomly selected very bright stars (r ≤ 14 mag) in the Northern hemisphere. During the Pilot and the first year Regular Surveys of LAMOST, a total of 1042 586 750 867 spectra of a signal-to-noise ratio S/N(7450 Å) ≥ 10 S/N(4650 Å) ≥ 10 have been collected. In this paper, we present a detailed description of the target selection algorithm, survey design, observations and the first data release of value-added catalogues (including radial velocities, effective temperatures, surface gravities, metallicities, values of interstellar extinction, distances, proper motions and orbital parameters) of the LSS-GAC.
Abstract
We present the second release of value-added catalogues of the LAMOST Spectroscopic Survey of the Galactic Anticentre (LSS-GAC DR2). The catalogues present values of radial velocity Vr, ...atmospheric parameters – effective temperature Teff, surface gravity log g, metallicity Fe/H, α-element to iron (metal) abundance ratio α/Fe (α/M), elemental abundances C/H and N/H and absolute magnitudes MV and $M_{K_{\rm s}}$ deduced from 1.8 million spectra of 1.4 million unique stars targeted by the LSS-GAC since 2011 September until 2014 June. The catalogues also give values of interstellar reddening, distance and orbital parameters determined with a variety of techniques, as well as proper motions and multiband photometry from the far-UV to the mid-IR collected from the literature and various surveys. Accuracies of radial velocities reach 5 km s−1 for the late-type stars, and those of distance estimates range between 10 and 30 per cent, depending on the spectral signal-to-noise ratios. Precisions of Fe/H, C/H and N/H estimates reach 0.1 dex, and those of α/Fe and α/M reach 0.05 dex. The large number of stars, the contiguous sky coverage, the simple yet non-trivial target selection function and the robust estimates of stellar radial velocities and atmospheric parameters, distances and elemental abundances make the catalogues a valuable data set to study the structure and evolution of the Galaxy, especially the solar-neighbourhood and the outer disc.
Accurate determination of stellar atmospheric parameters and elemental abundances is crucial for Galactic archaeology via large-scale spectroscopic surveys. In this paper, we estimate stellar ...atmospheric parameters -- effective temperature T sub( eff), surface gravity log g and metallicity Fe/H, absolute magnitudes M sub( V) and M sub( Ks), ...-element to metal (and iron) abundance ratio .../M (and .../Fe), as well as carbon and nitrogen abundances C/H and N/H from the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) spectra with a multivariate regression method based on kernel-based principal component analysis, using stars in common with other surveys (Hipparcos, Kepler, Apache Point Observatory Galactic Evolution Experiment) as training data sets. Both internal and external examinations indicate that given a spectral signal-to-noise ratio (SNR) better than 50, our method is capable of delivering stellar parameters with a precision of ~100 K for T sub( eff), ~0.1 dex for log g, 0.3-0.4 mag for M sub( V) and M sub( Ks), 0.1 dex for Fe/H, C/H and N/H, and better than 0.05 dex for .../M (.../Fe). The results are satisfactory even for a spectral SNR of 20. The work presents first determinations of C/H and N/H abundances from a vast data set of LAMOST, and, to our knowledge, the first reported implementation of absolute magnitude estimation directly based on a vast data set of observed spectra. The derived stellar parameters for millions of stars from the LAMOST surveys will be publicly available in the form of value-added catalogues. (ProQuest: ... denotes formulae/symbols omitted.)
We report the first experimental demonstration of quantum entanglement among ten spatially separated single photons. A near-optimal entangled photon-pair source was developed with simultaneously a ...source brightness of ∼12 MHz/W, a collection efficiency of ∼70%, and an indistinguishability of ∼91% between independent photons, which was used for a step-by-step engineering of multiphoton entanglement. Under a pump power of 0.57 W, the ten-photon count rate was increased by about 2 orders of magnitude compared to previous experiments, while maintaining a state fidelity sufficiently high for proving the genuine ten-particle entanglement. Our work created a state-of-the-art platform for multiphoton experiments, and enabled technologies for challenging optical quantum information tasks, such as the realization of Shor's error correction code and high-efficiency scattershot boson sampling.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
Plastic deformation of metallic glasses (MGs) has long been considered to be confined to nanoscale shear bands, but recently an affected zone around the shear band was found. Yet, due to technical ...limitations, the shear-band affected zone (SBAZ), which is critical for understanding shear banding and design of ductile MGs, has yet to be precisely identified. Here, by using magnetic domains as a probe with sufficiently high sensitivity and spatial resolution, we unveil the structure of SBAZs in detail. We demonstrate that shear banding is accompanied by a micrometer-scale SBAZ with a gradient in the strain field, and multiple shear bands interact through the superimposition of SBAZs. There also exists an ultra-long-range gradual elastic stress field extending hundreds of micrometers away from the shear band. Our findings provide a comprehensive picture on shear banding and are important for elucidating the micro-mechanisms of plastic deformation in glasses.
Many breakthroughs in the laboratories often do not bridge the gap between research and commercialization. However, silicon photonics bucked the trend, with industry observers estimating the ...commercial market to close in on a billion dollars in 2020 <xref ref-type="bibr" rid="ref45">45 . Silicon photonics leverages the billions of dollars and decades of research poured into silicon semiconductor device processing to enable high yield, robust processing, and most of all, low cost. Silicon is also a good optical material, with transparency in the commercially important infrared wavelength bands, and is a suitable platform for large-scale photonic integrated circuits. Silicon photonics is therefore slated to address the world's ever-increasing needs for bandwidth. It is part of an emerging ecosystem which includes designers, foundries, and integrators. In this paper, we review most of the foundries that presently enable silicon photonics integrated circuits fabrication. Some of these are pilot lines of major research institutes, and others are fully commercial pure-play foundries. Since silicon photonics has been commercially active for some years, foundries have released process design kits (PDK) that contain a standard device library. These libraries represent optimized and well-tested photonic elements, whose performance reflects the stability and maturity of the integration platforms. We will document the early works in silicon photonics, as well as its commercial status. We will provide a comprehensive review of the development of silicon photonics and the foundry services which enable the productization, including various efforts to develop and release PDK devices. In this context, we will report the long-standing efforts and contributions that previously IME/A * STAR and now AMF has dedicated to accelerating this journey.
ABSTRACT A sample of the Large Sky Area Multi-Object Fibre Spectroscopic Telescope spectra of early-type M0-M3 dwarfs is compared with Kepler observations. It is found that M dwarfs with strong ...chromospheric emission in have large flare activity in general. The rotational periods derived from the Kepler measurements have close correlations with the sizes of the flares, the power-law distribution index, and the equivalent widths of the emission. A clear trend exists for higher magnetic activities being detected in faster-rotating M dwarfs (rotation periods < 20 days).
We introduce the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) stellar parameter pipeline at Peking University – lsp3, developed and implemented for the determinations of radial ...velocity V
r and stellar atmospheric parameters (effective temperature T
eff, surface gravity log g, metallicity Fe/H) for the LAMOST Spectroscopic Survey of the Galactic Anticentre (LSS-GAC). We describe the algorithms of lsp3 and examine the accuracy of parameters yielded by it. The precision and accuracy of parameters yielded are investigated by comparing results of multi-epoch observations and of candidate members of open and globular clusters, with photometric calibration, as well as with independent determinations available from a number of external data bases, including the PASTEL archive, the APOGEE, SDSS and RAVE surveys, as well as those released in the LAMOST DR1. The uncertainties of lsp3 parameters are characterized and quantified as a function of the spectral signal-to-noise ratio (SNR) and stellar atmospheric parameters. We conclude that the current implementation of lsp3 has achieved an accuracy of 5.0 km s−1, 150 K, 0.25 dex, 0.15 dex for the radial velocity, effective temperature, surface gravity and metallicity, respectively, for LSS-GAC spectra of FGK stars of SNRs per pixel higher than 10. The lsp3 has been applied to over a million LSS-GAC spectra collected hitherto. Stellar parameters yielded by the lsp3 will be released to the general public following the data policy of LAMOST, together with estimates of the interstellar extinction E(B − V) and stellar distances, deduced by combining spectroscopic and multiband photometric measurements using a variety of techniques.
Highlights • Detection of irisin immunoreactivity in skeletal muscle and cardiomyocyte. • Presence of irisin immunoreactivity in the Purkinje cells of the cerebellum. • Co-expression of irisin ...immunoreactivity and glutamate decarboxylase (GAD) immunoreactivity in the Purkinje cells of the cerebellum. • Hypothetical neurocircuitry connecting the cerebellum to the fat tissue that may regulate adipocyte metabolism.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We present an empirical stellar spectra library created using spectra from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) DR5. This library represents a uniform data set ...ranging from 3750 through 8500 K in effective temperature (Teff), from −2.5 through +1.0 dex in metallicity (Fe/H), and from 0 to 5.0 dex in gravity (log g). The spectra in the library have resolutions R ∼ 1800, with well-calibrated fluxes and rest-framed wavelengths. Using a large number of red stars observed by LAMOST, we generated denser K-type templates to fill in data missing from current empirical spectral libraries, particularly the late K type. For K giants, we calibrated the spectroscopic surface gravities against the asteroseismic surface gravities. To verify the reliability of the parameters labeled for this library, we performed an internal cross-validation using a χ2 minimization method to interpolate the parameters of each individual spectrum using the remaining spectra in the library. We obtained precisions of 41 K, 0.11 dex, and 0.05 dex for Teff, log g, and Fe/H, respectively, which means the templates are labeled with correct stellar parameters. Through external comparisons, we confirmed that measurements of the stellar parameters through this library can achieve accuracies of approximately 125 K in Teff, 0.1 dex in Fe/H and 0.20 dex in log g without systematic offset. This empirical library is useful for stellar parameter measurements because it has large parameter coverage and full wavelength coverage from 3800 to 8900 .
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