Yongheng Zhao

• Ph.D
• Professor at Chinese Academy of Sciences

Recent studies have increasingly identified extended main sequence turn-off (eMSTO) phenomena in Galactic open clusters, yet the number of such clusters with sufficient spectroscopic information for member stars remains limited. Unlike most studies that rely on fitting isochrones based on CMD morphology to account for varying rotational velocities,...

Emission Line Galaxies (ELGs) are crucial for cosmological studies, particularly in understanding the large-scale structure of the Universe and the role of dark energy. ELGs form an essential component of the target catalogue for the Dark Energy Spectroscopic Instrument (DESI), a major astronomical survey. However, the accurate selection of ELGs fo...

We present spatially resolved spectroscopic observations of 10 isolated Galactic H II regions using data from the LAMOST Medium-Resolution Spectroscopic Survey of Nebulae (LAMOST MRS-N). The high spatial resolution of the data allows us to investigate the 1D radial profiles of emission-line fluxes (H α , [S II ], and [N II ]), flux ratios ([N II ]/...

Ancient stellar observations are a valuable cultural heritage, profoundly influencing both cultural domains and modern astronomical research. The Shi's Star Catalog (石氏星经), the oldest extant star catalog in China, faces controversy regarding its observational epoch. Determining this epoch via precession assumes accurate ancient coordinates and corr...

Ancient China recorded a wealth of astronomical observations, notably distinguished by the inclusion of empirical measurements of stellar observations. However, determining the precise observational epochs for these datasets poses a formidable challenge. This study employs the Generalized Hough Transform methodology to analyze two distinct sets of...

Ancient stellar observations are a valuable cultural heritage, profoundly influencing both cultural domains and modern astronomical research. The \textit{Shi's Star Catalog}, the oldest extant star catalog in China, faces controversy regarding its observational epoch. Determining this epoch via precession assumes accurate ancient coordinates and co...

We present spatially-resolved spectroscopic observations of 10 isolated Galactic HII regions using data from the LAMOST Medium-Resolution Spectroscopic Survey of Nebulae (LAMOST MRS-N). The high spatial resolution of the data allows us to investigate the 1D radial profiles of emission line fluxes (Ha, [S II] and [N II]), flux ratios ([N II]/Ha, [S...

Using radial velocity to estimate binary fraction and predict orbital parameter distribution laws is an important method in the studies of binary stars. However, the high dimensionality of the orbital parameters of the binary system pose challenges to this work, particularly in terms of sample size and the accuracy of the calculated results. We hav...

Using data from the Large Area Multi-Object fiber Spectroscopic Telescope Medium-Resolution Spectroscopic Survey of Nebulae, we create a sample of 17,821 diffuse ionized gas spectra in the anticenter region of the Milky Way by excluding fibers in the directions of H ii regions and supernova remnants. We then analyze the radial and vertical distribu...

Multi-object fiber spectroscopic survey is pivotal to astronomical research. Most spectroscopic telescopes are equipped with thousands of robotic fiber positioners designed to observe multiple celestial objects simultaneously. Despite this advancement, the risk of potential collisions between adjacent positioners, due to overlapping work zones, pos...

The large-scale measurement of galaxy redshifts holds significant importance for cosmological research, as well as for understanding the formation and evolution of galaxies. This study utilizes a known sample obtained by cross-correlating the Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys DR10 galaxy catalog with various galaxy...

We have established and released a new stellar index library of the Ca ii triplet, which serves as an indicator for characterizing the chromospheric activity of stars. The library is based on data from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Low-Resolution Spectroscopic Survey (LRS) Data Release 9. To better reflect t...

The full disk, full of gas and dust, determines the upper limit of planet masses, and its lifetime is critical for planet formation, especially for giant planets. In this work, we studied the evolutionary timescales of the full disks of T Tauri stars (TTSs) and their relations to accretion. Combined with Gaia EDR3, Two Micron All Sky Survey, and Wi...

Sky subtraction is a crucial step in the data reduction process for LAMOST, including dark, bright, and gray nights. During the pilot survey, on bright nights, atmospheric scattering of moonlight can introduce gradients in the sky background. In observations during bright moonlit nights, the sky component is significant, and sometimes, variations i...

Double white dwarf systems are of great astrophysical importance in the field of gravitational wave and Type Ia supernova. While the binary fraction of CO core white dwarf is about a few percents, the extremely low mass white dwarfs are all thought to be within binary systems. In this work, we report the orbital solution of a double degenerate syst...

Time-domain astronomy is progressing rapidly with the ongoing and upcoming large-scale photometric sky surveys led by the Vera C. Rubin Observatory project (LSST). Billions of variable sources call for better automatic classification algorithms for light curves. Among them, periodic variable stars are frequently studied. Different categories of per...

The advent of time-domain sky surveys has generated a vast amount of light variation data, enabling astronomers to investigate variable stars with large-scale samples. However, this also poses new opportunities and challenges for the time-domain research. In this paper, we focus on the classification of variable stars from the Catalina Surveys Data...

As astronomical data sets become too large for traditional analysis approaches, more machine-learning algorithms are employed in astronomy. A wealth of light variation data have been accumulated, which provide rich samples for astronomers to study variable stars. Facing the challenge of big data, this article takes the classification of variable an...

Green Pea galaxies are compact galaxies with high star formation rates. However, limited samples of Green Pea galaxies have HI 21 cm measurements. Whether the HI gas fraction (fHi ≡ MHI/M⋆) of Green Pea galaxies follows the existing scaling relations be- tween the fHi and NUV-r colour or linear combinations of colour and other physical quanti- ties...

The clarity of nights is the major factor that should be carefully considered for optical/infrared astronomical observatories in site-testing campaigns. Cloud coverage is directly related to the amount of time available for scientific observations at observatories. In this article, we report on the results of detailed night-time cloud statistics an...

The extremely-low-mass white dwarfs (ELM WDs) and pre-ELM WDs are helium-core white dwarfs with mass <∼ 0.3 M ⊙ . Evolution simulations show that a lower mass limit for ELM WDs exists at ≈0.14 M ⊙ and no ELM WD is proposed by observation to be less massive than that. Here we report the discovery of a binary system, LAMOST J224040.77-020732.8 (J2240...

High-precision stellar masses and radii measured directly from binaries can effectively calibrate stellar models. However, such a database containing full spectral types and a large range of metallicity is still not fully established. A continuous effort of data collection and analysis is requested to complete the database. In this work, we provide...

We report the discovery of one possible neutron star binary ( P orb = 0.8666 days) by using LAMOST low-resolution spectroscopic data. The visible companion is a late A-type dwarf ( T eff = 7900 ± 200 K; log g = 4.3 ± 0.2; M = 1.7 ± 0.1 M ⊙ ; R = 1.7 ± 0.2 R ⊙ ) at a distance of 1.11 ± 0.03 kpc. No double-lined feature can be seen from the Gran Tele...

The accurate estimation of photometric redshifts plays a crucial role in accomplishing science objectives of the large survey projects. The template-fitting and machine learning are the two main types of methods applied currently. Based on the training set obtained by cross-correlating the DESI Legacy Imaging Surveys DR9 galaxy catalogue and SDSS D...

High-precision stellar mass and radius measured directly from binaries can effectively calibrate the stellar models. However, such a database containing full spectral types and large range of metallicity is still not fully established. A continuous effort of data collecting and analysis are requested to complete the database. In this work, we provi...

The accurate estimation of photometric redshifts plays a crucial role in accomplishing science objectives of the large survey projects. Template-fitting and machine learning are the two main types of methods applied currently. Based on the training set obtained by cross-correlating the DESI Legacy Imaging Surveys DR9 galaxy catalogue and the SDSS D...

We report the discovery of one possible neutron star binary ($P_{\rm orb} =$ 0.8666 day) by using the LAMOST low-resolution spectroscopic data. The visible companion is a late A-type dwarf ($T_{\rm eff} = 7900 \pm 200$ K; log$g$ $=$ 4.3$\pm$0.2; $M =$ 1.7$\pm$0.1 M$_{\odot}$; $R\ =\ 1.7\pm0.2$ R$_{\odot}$), at a distance of 1.11$\pm0.03$ kpc. No do...

The Extremely Low Mass White Dwarfs (ELM WDs) and pre-ELM WDs are helium core white dwarfs with mass $<\sim 0.3M_{\odot}$. They are formed in close binaries and have lost over half of their initial masses via Common Envelope (CE) ejection or stable Roche Lobe Over Flow (RLOF). Both evolution simulations and observations show that a lower mass limit...

Diffuse interstellar bands (DIBs) have always been a mysterious existence in as- astronomical research. In this work, we provide more DIB samples to uncover a little bit of this mystery. With the LAMOST medium-resolution survey (MRS) spectra, we detected three DIBs λ6379, λ6614, and λ6660, obviously superimposed on the spectra of 11,003 stars. Thes...

This work is to retrieve emission-line spectra from the “Unknown” dataset in LAMOST DR7 V1.2, most of which are low signal-to-noise ratios (S/N) spectra. In the work, we perform emission line search and redshift calculations on the Unknown dataset to get possible emission line galaxy spectra. Taking the galaxy spectra released by LAMOST as template...

The double revolving fiber positioning technology is one of the key technologies for the success of The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). The accuracy of fiber positioning will directly affect the observation efficiency of LAMOST. To achieve higher fiber positioning accuracy, the original open-loop controlled fiber...

The large sky area multi-object fiber spectroscopic telescope (LAMOST), also known as the Guoshoujing Telescope, is a major national scientific facility for astronomical research located in Xinglong, China. Beginning with a pilot survey in 2011, LAMOST has been surveying the night sky for more than ten years. The LAMOST survey covers various object...

We introduce a method of subtracting geocoronal H α emissions from the spectra of LAMOST medium-resolution spectral survey of Galactic nebulae (LAMOST-MRS-N). The flux ratios of the H α sky line to the adjacent OH λ 6554 single line do not show a pattern or gradient distribution in a plate. More interestingly, the ratio is well correlated to solar...

Binary stars play an important role in the evolution of stellar populations . The intrinsic binary fraction ( f bin ) of O and B-type (OB) stars in LAMOST DR5 was investigated in this work. We employed a cross-correlation approach to estimate relative radial velocities for each of the stellar spectra. The algorithm described by Sana et al. (2013) w...

Correlating BASS DR3 catalogue with ALLWISE database, the data from optical and infrared information are obtained. The quasars from SDSS are taken as training and test samples while those from LAMOST are considered as external test sample. We propose two schemes to construct the redshift estimation models with XGBoost, CatBoost and Random forest. O...

The double revolving fiber positioning unit (FPU) is one of the key technologies of The Large Sky Area Multi-Object Fiber Spectroscope Telescope (LAMOST). The positioning accuracy of the computer controlled FPU depends on robot accuracy as well as the initial parameters of FPU. These initial parameters may deteriorate with time when FPU is running...

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) started a median-resolution spectroscopic (MRS, R ∼7500) survey since October 2018. The main scientific goals of MRS, including binary stars, pulsators and other variable stars, were launched with a time-domain spectroscopic survey. However, the systematic errors, including the...

LAMOST Data Release 5, covering ∼17 000 deg ² from –10° to 80° in declination, contains 9 million co-added low-resolution spectra of celestial objects, each spectrum combined from repeat exposure of two to tens of times during Oct 2011 to Jun 2017. In this paper, we present the spectra of individual exposures for all the objects in LAMOST Data Rele...

Correlating BASS DR3 catalogue with ALLWISE database, the data from optical and infrared information are obtained. The quasars from SDSS are taken as training and test samples while those from LAMOST are considered as external test sample. We propose two schemes to construct the redshift estimation models with XGBoost, CatBoost and Random forest. O...

Binary stars plays important role in the evolution of stellar populations . The intrinsic binary fraction ($f_{bin}$) of O and B-type (OB) stars in LAMOST DR5 was investigated in this work. We employed a cross-correlation approach to estimate relative radial velocities for each of the stellar spectra. The algorithm described by \cite{2013A&A...550A...

We introduce a method of subtracting geocoronal Halpha emissions from the spectra of LAMOST medium-resolution spectral survey of Galactic nebulae (LAMOST-MRS-N). The flux ratios of the Halpha sky line to the adjacent OH lambda6554 single line do not show a pattern or gradient distribution in a plate. More interestingly, the ratio is well correlated...

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) started median-resolution spectroscopic (MRS, R$\sim$7500) survey since October 2018. The main scientific goals of MRS, including binary stars, pulsators, and other variable stars are launched with a time-domain spectroscopic survey. However, the systematic errors, including the...

The observatory control system (OCS), a part of automated control of Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST), runs on the CentOS6 platform and implements the communication between modules based on Common Object Request Broker Architecture (CORBA). However, CORBA is complicated and has limited development support; moreover...

The Beijing-Arizona Sky Survey (BASS) Data Release 3 (DR3) catalogue was released in 2019, which contains the data from all BASS and the Mosaic z-band Legacy Survey (MzLS) observations during 2015 January and 2019 March, about 200 million sources. We cross-match BASS DR3 with spectral databases from the Sloan Digital Sky Survey (SDSS) and the Large...

To study the quality of stellar spectra of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) and the correctness of the corresponding stellar parameters derived by the LASP (LAMOST Stellar Parameter Pipeline), the outlier analysis method is applied to the archived AFGK stars in the fifth data release (DR5) of LAMOST. The outlie...

We derive a catalog of early-type emission-line stars including 30,048 spectra of 25,886 stars from LAMOST DR7, in which 3,922 have Simbad records. The sample is obtained using K-Nearest Neighbor and Random Forest methods and visually inspected. The spectra are classified into 3 morphological types (10 subtypes) based on H$\alpha$ emission line pro...

LAMOST Data Release 5, covering $\sim$17,000 $deg^2$ from $-10^{\circ}$ to $80^{\circ}$ in declination, contains 9 millions co-added low resolution spectra of celestial objects, each spectrum combined from repeat exposure of two to tens of times during Oct 2011 to Jun 2017. In this paper, We present the spectra of individual exposures for all the o...

The Beijing-Arizona Sky Survey (BASS) Data Release 3 (DR3) catalogue was released in 2019, which contains the data from all BASS and the Mosaic z-band Legacy Survey (MzLS) observations during 2015 January and 2019 March, about 200 million sources. We cross-match BASS DR3 with spectral databases from the Sloan Digital Sky Survey (SDSS) and the Large...

To study the quality of stellar spectra of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) and the correctness of the corresponding stellar parameters derived by the LASP (LAMOST Stellar Parameter Pipeline), the outlier analysis method is applied to the archived AFGK stars in the fifth data release (DR5 ) of LAMOST. The outli...

The ESA’s X-ray Multi-mirror Mission (XMM–Newton) created a new high-quality version of the XMM–Newton serendipitous source catalogue, 4XMM-DR9, which provides a wealth of information for observed sources. The 4XMM-DR9 catalogue is correlated with the Sloan Digital Sky Survey (SDSS) DR12 photometric data base and the AllWISE data base; we then get...

The ESA's X-ray Multi-Mirror Mission (XMM-Newton) created a new, high quality version of the XMM-Newton serendipitous source catalogue, 4XMM-DR9, which provides a wealth of information for observed sources. The 4XMM-DR9 catalogue is correlated with the Sloan Digital Sky Survey (SDSS) DR12 photometric database and the ALLWISE database, then we get t...

{The observatory control system (OCS), a part of automated control of Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST), runs on the CentOS6 platform and implements the communication between modules based on Common Object Request Broker Architecture (CORBA). However, CORBA is complicated and has limited development support; moreove...

We combine K -nearest neighbors (KNN) with a genetic algorithm (GA) for photometric redshift estimation of quasars, short for GeneticKNN, which is a weighted KNN approach supported by a GA. This approach has two improvements compared to KNN: one is the feature weighted by GA; the other is that the predicted redshift is not the redshift average of K...

Two Li-rich candidates, TYC 1338–1410–1 and TYC 2825–596–1, were observed by the new high-resolution echelle spectrograph, LAMOST/HRS. Based on their high-resolution and high-signal-to-noise ratio (SNR) spectra, we derived stellar parameters and abundances of 14 important elements for the two candidates. The stellar parameters and lithium abundance...

In this paper, we report 591 high-velocity star candidates (HiVelSCs) selected from over 10 million spectra of Data Release 7 (DR7) of the Large Sky Area Multi-object Fiber Spectroscopic Telescope and the second Gaia data release, with three-dimensional velocities in the Galactic rest frame larger than 445 km s ⁻¹ . We show that at least 43 HiVelSC...

Close white dwarf binaries consisting of a white dwarf and an A-, F-, G-, or K-type main-sequence star, henceforth close WD+AFGK binaries, are ideal systems to understand the nature of type Ia supernovae progenitors and to test binary evolution models. In this work we identify 775 WD+AFGK candidates from TGAS (The Tycho-Gaia Astrometric Solution) a...

In this paper, we report 591 high velocity star candidates (HiVelSCs) selected from over 10 million spectra of the data release seven (DR7) of the Large Sky Area Multi-object Fiber Spectroscopic Telescope and the second Gaia data release, with three-dimensional velocities in the Galactic rest-frame larger than 445 km/s. We show that at least 43 HiV...

Two Li-rich candidates, TYC 1338-1410-1 and TYC 2825-596-1, were observed with the new high-resolution echelle spectrograph, LAMOST/HRS. Based on the high-resolution and high-signal-to-noise ratio (SNR) spectra, we derived stellar parameters and abundances of 14 important elements for the two candidates. The stellar parameters and lithium abundance...

We report the discovery of a new transition type Wolf–Rayet (W-R) WN/C star in the Galaxy. According to its coordinates (R.A., decl.) J2000 = 18 h 51 m 39 .ˢ 7 , −05°34′51.″1, and the distance (7.11 − 1.22 + 1.56 kpc away from Earth) inferred from the second Gaia data release, it is found that W-R 121-16 is located in the Far 3 kpc Arm, and it is 3...

Close white dwarf binaries consisting of a white dwarf and an A, F, G or K type main sequence star, henceforth close WD+AFGK binaries, are ideal systems to understand the nature of type Ia supernovae progenitors and to test binary evolution models. In this work we identify 775 WD+AFGK candidates from TGAS (The Tycho-Gaia Astrometric Solution) and G...

We combine K-Nearest Neighbors (KNN) with genetic algorithm (GA) for photometric redshift estimation of quasars, short for GeneticKNN, which is a weighted KNN approach supported by GA. This approach has two improvements compared to KNN: one is the feature weighted by GA; another is that the predicted redshift is not the redshift average of K neighb...

Theoretical stellar spectra rely on model stellar atmospheres computed based on our understanding of the physical laws at play in the stellar interiors. These models, coupled with atomic and molecular line databases, are used to generate theoretical stellar spectral libraries (SSLs) comprising of stellar spectra over a regular grid of atmospheric p...

We report the discovery of a new transition type Wolf-Rayet (WR) WN/C star in the Galaxy. According to its coordinates (R.A., Dec)J2000 = 18h51m39.7s, -05d34m51.1s, and the distance (7.11 kpc away from Earth) inferred from the second Gaia, data release, it's found that WR 121-16 is located in the Far 3 kpc Arm, and it is 3.75 kpc away from the Gala...

Theoretical stellar spectra rely on model stellar atmospheres computed based on our understanding of the physical laws at play in the stellar interiors. These models, coupled with atomic and molecular line databases, are used to generate theoretical stellar spectral libraries (SSLs) comprising of stellar spectra over a regular grid of atmospheric p...

Site-testing is crucial for achieving the goal of scientific research and analysis of meteorological and optical observing conditions, one of the associated basic tasks. As one of three potential sites to host the 12-meter Large Optical/infrared Telescope (LOT), the Muztagh-ata site, which is located on the Pamir Plateau in Xinjiang, in west China,...

In this article, we present a detailed analysis of the statistical properties of seeing for the Muztagh-ata site which is a candidate site for hosting the future Chinese Large Optical/infrared Telescope (LOT) project. The measurements were obtained with differential image motion monitors (DIMMs) from April 2017 to November 2018 at different heights...

Based on previous site testing and satellite cloud data, Ali, Daocheng and Muztagh-ata have been selected as candidate sites for the Large Optical/Infrared Telescope (LOT) in China. We present the data collection, processing, management and quality analysis for our site testing based on using similar hardware. We analyze meteorological data, seeing...

A large ground-based optical/infrared telescope is being planned for a world-class astronomical site in China. The cloud-free night percentage is the primary meteorological consideration for evaluating candidate sites. The data from GMS and NOAA satellites and the MODIS instrument were utilized in this research, covering the period from 1996 to 201...

The Large Optical/infrared Telescope (LOT) is a ground-based 12 m diameter optical/infrared telescope which is proposed to be built in the western part of China in the next decade. Based on satellite remote sensing data, along with geographical, logistical and political considerations, three candidate sites were chosen for ground-based astronomical...

In the era of big data astronomy, next generation telescopes and large sky surveys produce data sets at the TB or even PB level. Due to their large data volumes, these astronomical data sets are extremely difficult to transfer and analyze using personal computers or small clusters. In order to offer better access to data, data centers now generally...

Since September 2018, LAMOST starts a new 5-year medium-resolution spectroscopic survey (MRS) using bright/gray nights. We present the scientific goals of LAMOST-MRS and propose a near optimistic strategy of the survey. A complete footprint is also provided. Not only the regular medium-resolution survey, but also a time-domain spectroscopic survey...

In the era of big data astronomy, next generation telescopes and large sky surveys produce data sets at the TB or even PB level. Due to their large data volumes, these astronomical data sets are extremely difficult to transfer and analyze using personal computers or small clusters. In order to offer better access to data, data centers now generally...

The fundamental stellar atmospheric parameters ( T eff and log g ) and 13 chemical abundances are derived for medium-resolution spectroscopy from Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Medium Resolution Survey (MRS) data sets with a deep-learning method. The neural networks we designed, named SPCANet, precisely map LAMOS...

With the increase of known RR Lyrae stars, it is reliable to create classifiers of RR Lyrae stars based on their photometric data or combined photometric and spectroscopic data. Nevertheless the total number of known RR Lyrae stars is still too small compared with the large survey databases. So classification of RR Lyrae stars and other sources bel...

Based on the SDSS and SDSS-WISE quasar datasets, we put forward two schemes to estimate the photometric redshifts of quasars. Our schemes are based on the idea that the samples are firstly classified into subsamples by a classifier and then a photometric redshift estimation of different subsamples is performed by a regressor. Random Forest is adopt...

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$_{\odot}$$^{1-4}$. Theory predicts, however, that X-ray emitting systems form a minority of the total population of star-black hole binaries$^{5,6...

All stellar-mass black holes have hitherto been identified by X-rays emitted from gas that is accreting onto the black hole from a companion star. These systems are all binaries with a black-hole mass that is less than 30 times that of the Sun1,2,3,4. Theory predicts, however, that X-ray-emitting systems form a minority of the total population of s...

We present the first release of the MaNGA Stellar Library (MaStar), which is a large, well-calibrated, high-quality empirical library covering the wavelength range 3622–10354 Å at a resolving power of R ∼ 1800. The spectra were obtained using the same instrument as used by the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) project, by...

The radial velocity (RV) is a basic physical quantity that can be determined through the Doppler shift of the spectrum of a star. The precision of the RV measurement depends on the resolution of the spectrum we used and the accuracy of wavelength calibration. In this work, radial velocities of the Large Sky Area Multi-Object Fibre Spectroscopic Tel...

The radial velocity (RV) is a basic physical quantity which can be determined through Doppler shift of the spectrum of a star. The precision of RV measurement depends on the resolution of the spectrum we used and the accuracy of wavelength calibration. In this work, radial velocities of LAMOST-II medium resolution (R ~ 7500) spectra are measured fo...

We present optical luminosity functions (LFs) of galaxies in the 0.1 g , 0.1 r , 0.1 i bands, calculated using data in ∼ 40 deg 2 sky area of the LAMOST Complete Spectroscopic Survey of Pointing Area (LaCoSSPAr) in the Southern Galactic Cap. Redshifts for galaxies brighter than r = 18.1 were obtained mainly with LAMOST. In each band, LFs derived us...

We present a sample of 86 111 star-forming galaxies (SFGs) selected from the catalogue of the MPA-JHU emission-line measurements for SDSS DR7 to investigate the evolution of mass–metallicity (MZ) relation. We find that: under the |$\rm log(L_{H \alpha })\gt 41.0$| threshold, the 0.04 < z ≤ 0.06 SFGs with 9.2 < log(M⋆/M|$\odot$|) < 9.5 have always h...

Based on the SDSS and SDSS-WISE quasar datasets, we put forward two schemes to estimate photometric redshifts of quasars. The schemes are based on the idea that the samples are firstly classified into subsamples by a classifier and then photometric redshift estimation of different subsamples is performed by a regressor, respectively. Random forest...