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M dwarfs are the dominating type of stars in the solar neighbourhood. They serve as excellent tracers for the study of the distribution and properties of the nearby interstellar dust. In this work, we aim to obtain high accuracy reddening values of M dwarf stars from the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) Data Release 8 (DR8). Combining the LAMOST spectra with the high-quality optical photometry from the Gaia Early Data Release 3 (EDR3), we have estimated the reddening values E (G BP − G RP) of 641 426 M dwarfs with the machine learning algorithm random forest regression. The typical reddening uncertainty is only 0.03 mag in E (G BP − G RP). We have obtained the reddening coefficient |$R_{(G_{\rm BP}-G_{\rm RP})}$|⁠ , which is a function of the stellar intrinsic colour (G BP − G RP)0 and reddening value E (B − V). The values of E (B − V) are also provided for the individual stars in our catalogue. Our resultant high accuracy reddening values of M dwarfs, combined with the Gaia parallaxes, will be very powerful to map the fine structures of the dust in the solar neighbourhood. [ABSTRACT FROM AUTHOR]

We present a large catalogue of molecular clouds with accurate distance estimates in the Southern sky. Based on the three-dimensional dust extinction map and the best-fitting extinction and distance information of over 17 million stars presented in Guo et al. (2021, ApJ, 906, 47), we have identified 250 dust/molecular clouds in the Southern sky using a hierarchical structure identification algorithm. Amongst these are 71 clouds located at high Galactic latitudes (b < −10°). We have estimated the distances to the clouds by fitting the extinction versus distance profiles of the lines of sight overlapping with the clouds, using a simple Gaussian dust distribution model. The typical uncertainties of the distances are less than 7 per cent. We also provide the physical properties of the individual clouds, including the linear radius, mass and surface mass density. [ABSTRACT FROM AUTHOR]

We present high-resolution maps of the dust reddening in the Magellanic Clouds (MCs). The maps cover the Large and Small Magellanic Cloud (LMC and SMC) area and have a spatial angular resolution between ∼26 arcsec and 55 arcmin. Based on the data from the optical and near-infrared (IR) photometric surveys, including the Gaia Survey, the SkyMapper Southern Survey (SMSS), the Survey of the Magellanic Stellar History (SMASH), the Two Micron All Sky Survey (2MASS), and the near-IR YJK S VISTA survey of the Magellanic Clouds system (VMC), we have obtained multiband photometric stellar samples containing over 6 million stars in the LMC and SMC area. Based on the measurements of the proper motions and parallaxes of the individual stars from Gaia Early Data Release 3 (Gaia EDR3), we have built clean samples that contain stars from the LMC, SMC, and Milky Way (MW), respectively. We apply the spectral energy distribution (SED) fitting to the individual sample stars to estimate their reddening values. As a result, we have derived the best-fitting reddening values of ∼1.9 million stars in the LMC, 1.5 million stars in the SMC, and 0.6 million stars in the MW, which are used to construct dust reddening maps in the MCs. Our maps are consistent with those from the literature. The resultant high-resolution dust maps in the MCs are not only important tools for reddening correction of sources in the MCs, but also fundamental for the studies of the distribution and properties of dust in the two galaxies. [ABSTRACT FROM AUTHOR]

We present a large, homogeneous catalogue of molecular clouds within 4 kpc from the Sun at low Galactic latitudes (| b | < 10°) with unprecedented accurate distance determinations. Based on the 3D dust reddening map and estimates of colour excesses and distances of over 32 million stars presented in Chen et al., we have identified 567 dust/molecular clouds with a hierarchical structure identification method and obtained their distance estimates by a dust model fitting algorithm. The typical distance uncertainty is less than 5 per cent. As far as we know, this is the first large catalogue of molecular clouds in the Galactic plane with distances derived in a direct manner. The clouds are seen to lie along the Sagittarius, Local and Perseus Arms. In addition to the known structures, we propose the existence of a possible spur , with a pitch angle of about 34°, connecting the Local and the Sagittarius Arms in the fourth quadrant. We have also derived the physical properties of those molecular clouds. The distribution of cloud properties in different parameter spaces agrees grossly with the previous results. Our cloud sample is an ideal starting point to study the concentration of dust and gas in the solar vicinity and their star formation activities. [ABSTRACT FROM AUTHOR]

We present three-dimensional (3D) dust mapping of 12 supernova remnants (SNRs) in the Galactic anticentre (Galactic longitude l between 150○ and 210○) based on a recent 3D interstellar extinction map. The dust distribution of the regions, which cover the full extents in the radio continuum for the individual SNRs, is discussed. Four SNRs show significant spatial coincidences between molecular clouds (MCs) revealed from the 3D extinction mapping and the corresponding radio features. The results confirm the interactions between these SNRs and their surrounding MCs. Based on these correlations, we provide new distance estimates of the four SNRs, G189.1+3.0 (IC443, |$d=1729^{+116}_{-94} \rm \, pc$|⁠), G190.9–2.2 (⁠|$d=1036^{+17}_{-81} \rm \, pc$|⁠), G205.5+0.5 (⁠|$d=941^{+96}_{-94}$| or |$1257^{+92}_{-101} \rm \, pc$|⁠), and G213.0–0.6 (⁠|$d=1146^{+79}_{-80} \rm \, pc$|⁠). In addition, we find indirect evidences of potential interactions between SNRs and MCs for three other SNRs. New distance constraints are also given for these three SNRs. [ABSTRACT FROM AUTHOR]

We present new three-dimensional (3D) interstellar dust reddening maps of the Galactic plane in three colours, E (G − K S), E (G BP − G RP), and E (H − K S). The maps have a spatial angular resolution of 6 arcmin and covers over 7000 deg2 of the Galactic plane for Galactic longitude 0° < l < 360° and latitude | b | < 10°. The maps are constructed from robust parallax estimates from the Gaia Data Release 2 (Gaia DR2) combined with the high-quality optical photometry from the Gaia DR2 and the infrared photometry from the Two Micron All Sky Survey and Wide-Field Infrared Survey Explorer survey. We estimate the colour excesses, E (G − K S), E (G BP − G RP), and E (H − K S), of over 56 million stars with the machine-learning algorithm Random Forest regression, using a training data set constructed from the large-scale spectroscopic surveys, Large Sky Area Multi-Object Fibre Spectroscopic Telescope, Sloan Extension for Galactic Understanding and Exploration, and Apache Point Observatory Galactic Evolution Experiment. The results reveal the large-scale dust distribution in the Galactic disc, showing a number of features consistent with the earlier studies. The Galactic dust disc is clearly warped and show complex structures possibly spatially associated with the Sagittarius, Local, and Perseus arms. We also provide the empirical extinction coefficients for the Gaia photometry that can be used to convert the colour excesses presented here to the line-of-sight extinction values in the Gaia photometric bands. [ABSTRACT FROM AUTHOR]

We present a detailed analysis of the selection function of the LAMOST Spectroscopic Survey of the Galactic Anti-centre (LSS-GAC). LSS-GAC was designed to obtain low-resolution optical spectra for a sample of more than 3 million stars in the Galactic anti-centre. The second release of value-added catalogues of the LSS-GAC (LSS-GAC DR2) contains stellar parameters, including radial velocity, atmospheric parameters, elemental abundances, and absolute magnitudes deduced from 1.8 million spectra of 1.4 million unique stars targeted by the LSS-GAC between 2011 and 2014. For many studies using this data base, such as those investigating the chemodynamical structure of the Milky Way, a detailed understanding of the selection function of the survey is indispensable. In this paper, we describe how the selection function of the LSS-GAC can be evaluated to sufficient detail and provide selection function corrections for all spectroscopic measurements with reliable parameters released in LSS-GAC DR2. The results, to be released as new entries in the LSS-GAC value-added catalogues, can be used to correct the selection effects of the catalogue for scientific studies of various purposes. [ABSTRACT FROM AUTHOR]

We present a three-dimensional (3D) extinction analysis in the region towards the supernova remnant (SNR) S147 (G180.0-1.7) using multiband photometric data from the Xuyi Schmidt Telescope Photometric Survey of the Galactic Anticentre (XSTPS-GAC), 2MASS and WISE. We isolate a previously unrecognized dust structure likely to be associated with SNR S147. The structure, which we term as 'S147 dust cloud', is estimated to have a distance d = 1.22 ± 0.21 kpc, consistent with the conjecture that S147 is associated with pulsar PSR J0538 + 2817. The cloud includes several dense clumps of relatively high extinction that locate on the radio shell of S147 and coincide spatially with the CO and gamma-ray emission features. We conclude that the usage of CO measurements to trace the SNR associated MCs is unavoidably limited by the detection threshold, dust depletion and the difficulty of distance estimates in the outer Galaxy. 3D dust extinction mapping may provide a better way to identify and study SNR-MC interactions. [ABSTRACT FROM AUTHOR]

We investigate the correlation between extinction and HI and CO emission at intermediate and high Galactic latitudes (|b| > 10°) within the footprint of the Xuyi Schmidt Telescope Photometric Survey of the Galactic anticentre (XSTPS-GAC) on small and large scales. In Paper I, we present a three-dimensional (3D) dust extinction map within the footprint of XSTPS-GAC, covering a sky area of over 6000 deg² at a spatial angular resolution of 6 arcmin. In the current work, the map is combined with data from gas tracers, including HI data from the Galactic Arecibo L-band Feed Array HI survey and CO data from the Planck mission, to constrain the values of dust-to-gas ratio DGR = AV/N(H) and CO-to-H2 conversion factor XCO = N(H2)/WCO for the entire GAC footprint excluding the Galactic plane, as well as for selected star-forming regions (such as the Orion, Taurus and Perseus clouds) and a region of diffuse gas in the northern Galactic hemisphere. For the whole GAC footprint, we find DGR = (4.15 ± 0.01) × 10-22 mag cm² and XCO = (1.72 ± 0.03) × 1020 cm-2 (K km s-1)-1. We have also investigated the distribution of 'CO-dark' gas (DG) within the footprint of GAC and found a linear correlation between the DG column density and the V-band extinction: N (DG) ≃ 2.2 × 1021(AV - AcV) cm-2. The mass fraction of DG is found to be fDG ~ 0.55 towards the Galactic anticentre, which is respectively about 23 and 124 per cent of the atomic and CO-traced molecular gas in the same region. This result is consistent with the theoretical work of Papadopoulos et al. but much larger than that expected in the H2 cloud models by Wolfire et al. [ABSTRACT FROM AUTHOR]

We present a three-dimensional extinction map in the r band. The map has a spatial angular resolution, depending on latitude, between 3 and 9 arcmin and covers the entire Xuyi Schmidt Telescope Photometric Survey of the Galactic Anticentre (XSTPS-GAC) survey area of over 6000 deg2 for Galactic longitude 140 < l < 240 deg and latitude −60 < b < 40 deg. By cross-matching the photometric catalogue of the XSTPS-GAC with those of 2MASS and WISE, we have built a multiband photometric stellar sample of about 30 million stars and applied spectral energy distribution (SED) fitting to the sample. By combining photometric data from the optical to the near-infrared, we are able to break the degeneracy between the intrinsic stellar colours and the amounts of extinction by dust grains for stars with high photometric accuracy, and trace the extinction as a function of distance for low Galactic latitude and thus highly extincted regions. This has allowed us to derive the best-fitting extinction and distance information of more than 13 million stars, which are used to construct the three-dimensional extinction map. We have also applied a Rayleigh–Jeans colour excess (RJCE) method to the data using the 2MASS and WISE colour (H − W2). The resulting RJCE extinction map is consistent with the integrated two-dimensional map deduced using the best-fitting SED algorithm. However for individual stars, the amounts of extinction yielded by the RJCE method suffer from larger errors than those given by the best-fitting SED algorithm. [ABSTRACT FROM PUBLISHER]

We derive the radiative transfer equation for arbitrary stationary relativistic flows in stationary space–times, i.e. for steady-state transfer problems. We show how the standard characteristics method of solution developed by Mihalas and used throughout the radiative transfer community can be adapted to multidimensional applications with isotropic sources. Because the characteristics always coincide with geodesics and can always be specified by constants, direct integration of the characteristics derived from the transfer equation as commonly done in 1D applications is not required. The characteristics are known for a specified metric from the geodesics. We give details in both flat and static spherically symmetric space–times. This work has direct application in 3D simulations of supernovae, gamma-ray bursts, and active galactic nuclei, as well as in modelling neutron star atmospheres. [ABSTRACT FROM AUTHOR]

We estimate the solar peculiar velocities and Oort constants using a sample of 5627 A-type stars with |$d\lt 0.6\, \rm kpc$| and |$|z|\lt 0.1\, \rm kpc$|⁠ , selected from the LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic Telescope) surveys. The radial and tangential velocities of these A-type stars are fitted by using a non-axisymmetric model. The best-fitting result yields the solar peculiar velocities |$(U_\odot ,V_\odot ,W_\odot)=(11.69\pm 0.68, 10.16\pm 0.51, 7.67\pm 0.10)\, \rm km\, s^{-1}$| and Oort constants |$A=16.31\pm 0.89\, \rm km\, s^{-1}\, kpc^{-1}$|⁠ , |$B=-11.99\pm 0.79\, \rm km\, s^{-1}\, kpc^{-1}$|⁠ , |$C=-3.10\pm 0.48\, \rm km\, s^{-1}\, kpc^{-1}$|⁠ , and |$K=-1.25\pm 1.04\, \rm km\, s^{-1}\, kpc^{-1}$|⁠. |$|K+C|\gt 4\, \rm km\, s^{-1}\, kpc^{-1}$| means that there is a radial velocity gradient in the extended local disc, implying that the local disc is in a non-asymmetric potential. Using the derived Oort constants, we derive the local angular velocity |$\Omega \, {\approx }\, A-B=28.30\pm 1.19\, \rm km\, s^{-1}\, kpc^{-1}$|⁠. By using A-type star sample of different volumes, we further try to evaluate the impacts of the ridge pattern in the R – V ϕ plane on constraining the solar motions and Oort constants. As the volume becomes larger towards the anticentre direction, the values of A and B become larger (implying a steeper slope of the local rotation curve) and the value of V ⊙ becomes smaller probably caused by the ridge structure and its signal increasing with distance. [ABSTRACT FROM AUTHOR]

We perform analysis of the 3D kinematics of Milky Way disc stars in mono-age populations. We focus on stars between Galactocentric distances of R  = 6 and 14  kpc, selected from the combined LAMOST Data Release 4 (DR4) red clump giant stars and Gaia DR2 proper motion catalogue. We confirm the 3D asymmetrical motions of recent works and provide time tagging of the Galactic outer disc asymmetrical motions near the anticentre direction out to Galactocentric distances of 14 kpc. Radial Galactocentric motions reach values up to 10 km s−1, depending on the age of the population, and present a north–south asymmetry in the region corresponding to density and velocity substructures that were sensitive to the perturbations in the early 6  Gyr. After that time, the disc stars in this asymmetrical structure have become kinematically hotter, and are thus not sensitive to perturbations, and we find the structure is a relatively younger population. With quantitative analysis, we find stars both above and below the plane at R ≳ 9 kpc that exhibit bending mode motions of which the sensitive duration is around 8  Gyr. We speculate that the in-plane asymmetries might not be mainly caused by a fast rotating bar, intrinsically elliptical outer disc, secular expansion of the disc, or streams. Spiral arm dynamics, out-of-equilibrium models, minor mergers or others are important contributors. Vertical motions might be dominated by bending and breathing modes induced by complicated inner or external perturbers. It is likely that many of these mechanisms are coupled together. [ABSTRACT FROM AUTHOR]

Classification of stellar spectra from voluminous spectra is a very important and challenging task. In order to better classify stellar spectra, inspired by the principle of deep convolutional neural network (CNN), we propose a supervised algorithm for stellar spectra classification based on 1D stellar spectra convolutional neural network (1D SSCNN). In 1D SSCNN, we modify the traditional 2D convolutional neural network into 1D network to adapt to the spectral classification. On the basis of using convolution algorithm, the spectral features are extracted and used for classification. We first use the stellar spectra data to train a 1D SSCNN to obtain a well-trained model, and then we apply the well-trained model to classify the unknown spectra. To evaluate the performance of the proposed algorithms, we apply 1D SSCNN to classify three spectral types: F-type spectra, G-type spectra, and K-type spectra and 10 subclasses of K-type spectra: A0-type, A5-type, F0-type, F5-type, G0-type, G5-type, K0-type, K5-type, M0-type, and M5-type spectra from Sloan Digital Sky Survey (SDSS). Our 1D SSCNN algorithm obtain higher classification accuracy compared with support vector machine (SVM), random forest (RF), and artificial neural network (ANN). [ABSTRACT FROM AUTHOR]

In this study, we expand the coverage and improve the homogeneity of the distribution of MILES template stars in the parameter space, as well as extend the wavelength coverage of the template spectra to the far red beyond the Ca  ii triplet. To achieve this, we have carried out a major observational campaign using two long-slit spectrographs: the OMR mounted on the National Astronomy Observatory of China (NAOC) 2.16-m telescope and the Yunnan Faint Object Spectrograph and Camera (YFOSC) mounted on the Yunnan Astronomical Observatory (YNAO) 2.4-m telescope. The original sample is based on the MILES library, supplemented by 918 stars selected from the PASTEL data base. In total, 822 OMR and 1324 YFOSC spectra have been collected and reduced, covering the wavelength ranges λλ3800–5180 and λλ5150–9000, respectively. The spectra have a mean resolution full width at half-maximum of ∼3.3 Å and are wavelength- and flux-calibrated to an accuracy of ∼20 km s−1 and ∼5 per cent, respectively. The spectra are further corrected for systematic errors in the wavelength calibration to an accuracy of ∼4 km s−1 by cross-correlating with the theoretical spectra. Almost all the spectra have an average signal-to-noise ratio better than 100 per pixel. Combined with the MILES spectra, there are now 1731, 1542, 1324 and 1273 stars with spectra covering λλ3800–5180, λλ3800–7500, λλ5150–9000 and λλ3800–9000, respectively. In this paper, we describe our template star selection, the observation and data reduction, and we present the reduced spectra collected hitherto. [ABSTRACT FROM AUTHOR]

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 MKs 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. [ABSTRACT FROM AUTHOR]

The rotation curve (RC) of the Milky Way out to ~100 kpc has been constructed using ~16 000 primary red clump giants (PRCGs) in the outer disc selected from the LAMOST Spectroscopic Survey of the Galactic Anti-centre (LSS-GAC) and the Sloan Digital Sky Survey (SDSS)-III/APOGEE survey, combined with ~5700 halo K giants (HKGs) selected from the SDSS/SEGUE survey. To derive the RC, the PRCG sample of the warm disc population and the HKG sample of halo stellar population are, respectively, analysed using a kinematical model allowing for the asymmetric drift corrections and re-analysed using the spherical Jeans equation along with measurements of the anisotropic parameter β currently available. The typical uncertainties of RC derived from the PRCG and HKG samples are, respectively, 5- 7 km s-1 and several tens km s-1.We determine a circular velocity at the solar position, Vc(R0) = 240 ± 6 km s-1 and an azimuthal peculiar speed of the Sun, V☉ = 12.1 ± 7.6 km s-1, both in good agreement with the previous determinations. The newly constructed RC has a generally flat value of 240 km s-1 within a Galactocentric distance r of 25 kpc and then decreases steadily to 150 km s-1 at r ~ 100 kpc. On top of this overall trend, the RC exhibits two prominent localized dips, one at r ~11 kpc and another at r ~ 19 kpc. From the newly constructed RC, combined with other constraints, we have built a parametrized mass model for the Galaxy, yielding a virial mass of the MilkyWay's dark matter halo of 0.90+0.07 -0.08 × 1012 M☉ and a local dark matter density, ρ☉,dm = 0.32+0.02 -0.02 GeV cm-3. [ABSTRACT FROM AUTHOR]

We re-estimate the peculiar velocity of the Sun with respect to the local standard of rest (LSR) using a sample of local stars within 600 pc of the Sun, selected from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST, also named the Guoshoujing Telescope) Spectroscopic Survey of the Galactic Anti-centre (LSS-GAC). The sample consists of 94 332 FGK main-sequence stars with well-determined radial velocities and atmospheric parameters. To derive the LSR, two independent analyses are applied to the data. First, we determine the solarmotion by comparing the observed velocity distribution to that generated with the analytic formulism of Schönrich & Binney that has been demonstrated to show excellent agreement with rigorous torus-based dynamics modelling by Binney & McMillan. Secondly, we propose that cold populations of thin disc stars, selected by applying an orbital eccentricity cut, can be directly used to determine the LSR without the need of asymmetric drift corrections. Both approaches yield consistent results of solarmotion in the direction of Galactic rotation, V⊙, that are much higher than the standard value adopted hitherto, derived from Strömgren's equation. The newly deduced values of V⊙ are 1-2 km s-1 smaller than the more recent estimates derived from the Geneva-Copenhagen Survey (GCS) sample of stars in the solar neighbourhood (within 100 pc).We attribute the small difference to the presence of several well-known moving groups in the GCS sample that, fortunately, hardly affect the LSS-GAC sample. The newly derived radial (U⊙) and vertical (W⊙) components of the solar motion agree well with the previous studies. In addition, for all components of the solar motion, the values yielded by stars of different spectral types in the LSS-GAC sample are consistent with each other, suggesting that the local disc is well relaxed and that the LSR reported in the current work is robust. Our final recommended LSR is, (U⊙, V⊙,W⊙)=(7.01 ± 0.20, 10.13 ± 0.12, 4.95 ± 0.09) km s-1. [ABSTRACT FROM AUTHOR]

We have developed and implemented an iterative algorithm of flux calibration for the LAMOST Spectroscopic Survey of the Galactic anticentre (LSS-GAC). For a given LSS-GAC plate, the spectra are first processed with a set of nominal spectral response curves (SRCs) and used to derive initial stellar atmospheric parameters (effective temperature Teff, surface gravity log g and metallicity [Fe/H]) as well as dust reddening E(B − V) of all targeted stars. For each of the 16 spectrographs, several F-type stars with good signal-to-noise ratios are selected as flux standard stars for further, iterative spectral flux calibration. Comparison of spectrophotometric colours, deduced from the flux-calibrated spectra, with the photometric measurements yield average differences of 0.02 ± 0.07 and −0.04 ± 0.09 mag for (g − r) and (g − i), respectively. The relatively large negative offset in (g − i) is because we have opted not to correct for the telluric bands, most notably the atmospheric A band in the wavelength range of the i band. Comparison of LSS-GAC multi-epoch observations of duplicate targets indicates that the algorithm has achieved an accuracy of about 10 per cent in relative flux calibration for the wavelength range 4000–9000 Å. The shapes of SRCs deduced for individual LAMOST spectrographs vary by up to 30 per cent for a given night, and larger for different nights, indicating that the derivation of SRCs for the individual plates is essential to achieve accurate flux calibration for the LAMOST spectra. [ABSTRACT FROM AUTHOR]

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 Vr and stellar atmospheric parameters (effective temperature Teff, 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. [ABSTRACT FROM PUBLISHER]

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 FROM PUBLISHER]