We carry out an optical morphological and infrared spectral study for two young planetary nebulae(PNs)Hen2-158 and Pe 1-1 to understand their complex shapes and dust properties.Hubble Space Telescope optical images re...We carry out an optical morphological and infrared spectral study for two young planetary nebulae(PNs)Hen2-158 and Pe 1-1 to understand their complex shapes and dust properties.Hubble Space Telescope optical images reveal that these nebulae have several bipolar-lobed structures and a faint arc with a clear boundary is located at the northwestern side of Pe 1-1.The presence of this arc-shaped structure suggests that the object interacts with its nearby interstellar medium.Spitzer IRS spectroscopic observations of these young nebulae clearly show prominent unidentified infrared emission features and a weak silicate band in Pe 1-1,indicating that Hen 2-158 is a carbonrich nebula and Pe 1-1 has a mixed chemistry dust environment.Furthermore,we construct two three-dimensional models for these PNs to realize their intrinsic structures.The simulated models of the nebulae suggest that multipolar nebulae may be more numerous than we thought.Our analyses of spectral energy distributions for Hen 2-158 and Pe 1-1 show that they have low luminosities and low stellar effective temperatures,suggesting that these nebulae are young PNs.A possible correlation between typical multipolar young PNs and nested nebulae is also discussed.展开更多
Since Sep.2018,LAMOST has started the medium-resolution(R~7500)spectral survey(MRS).We proposed the spectral survey of Galactic nebulae,including HⅡregions,HH objects,supernova remnants,planetary nebulae and the spec...Since Sep.2018,LAMOST has started the medium-resolution(R~7500)spectral survey(MRS).We proposed the spectral survey of Galactic nebulae,including HⅡregions,HH objects,supernova remnants,planetary nebulae and the special stars with MRS(LAMOST MRS-N).LAMOST MRS-N covers about 1700 square degrees of the northern Galactic plane within 40°<l<215°and-5°<b<5°.In this 5-year survey,we plan to observe about 500 thousand nebulae spectra.According to the commissioning observations,the nebulae spectra can provide precise radial velocity with uncertainty less than 1 km s^(-1).These high-precision spectral data are of great significance to our understanding of star formation and evolution.展开更多
The spectral observations and analysis for the W80 region are presented by using the data of Medium-Resolution Spectroscopic Survey of Nebulae(MRS-N) with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope(...The spectral observations and analysis for the W80 region are presented by using the data of Medium-Resolution Spectroscopic Survey of Nebulae(MRS-N) with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST).A total of 2982 high-quality nebular spectra have been obtained in the 20 square degree field of view which covers the W80 complex,and the largest sample of spectral data has been established for the first time.The relative intensities,radial velocities(RVs),and full widths at half maximum(FWHMs) are measured with the high spectral resolution of LAMOST MRS-N,for Ha λ6563?,[NⅡ] λλ6548 A,6584 A,and [SⅡ] λλ6716A,6731 A emission lines.In the field of view of the whole W80 region,the strongest line emissions are found to be consistent with the bright nebulae NGC 7000,IC 5070,and LBN 391,and weak line emissions also exist in the Middle Region,where no bright nebulae are detected by the wide-band optical observations.The large-scale spectral observations of the W80 region reveal the systematic spatial variations of RVs and FWHMs,and several unique structural features.A "curved feature" to the east of NGC 7000,and a "jet feature" to the west of LBN 391 are detected to be showing larger RVs.A "wider FWHM region" is identified in the eastern part of NGC 7000.The variations of[S Ⅱ]/Ha ratios display a gradient from southwest to northeast in the NGC 7000 region,and manifest a ring shape around the "W80 bubble" ionized by an O-type star in L935.Further spectral and multi-band observations are guaranteed to investigate in detail the structural features.展开更多
We obtained seven spectra of the Be star V423 Aur on 2017 Dec.5 using the LAMOST MediumResolution Spectrograph with exposures from 600 to 1200 seconds.These spectra show the irregular Ha emission line profile variatio...We obtained seven spectra of the Be star V423 Aur on 2017 Dec.5 using the LAMOST MediumResolution Spectrograph with exposures from 600 to 1200 seconds.These spectra show the irregular Ha emission line profile variations(LPVs).In the seven spectra,from the 4 th to 7 th,the left part of Ha profile even shows excess.However,no variation can be seen from the follow-up observation of photometry by 1.26-m telescope and High-Resolution spectra by 2.16-m telescope.According to the High-Resolution spectra,we conclude that it is a B7 V type star with E(B-V)=0.709±0.036 and its vsini is221.8 km s-1.The short-term Ha LPVs could be explained as a result of the transient ejection of matter from rotating disk or shell around V423 Aur.展开更多
The Large sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST) medium-resolution spectral survey of Galactic Nebulae(MRS-N) has conducted for more than three years since 2018 September and observed more than190...The Large sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST) medium-resolution spectral survey of Galactic Nebulae(MRS-N) has conducted for more than three years since 2018 September and observed more than190 thousand nebular spectra and 20 thousand stellar spectra.However,there is not yet a data processing pipeline for nebular spectra.To significantly improve the accuracy of nebulae classification and their physical parameters,we developed the MRS-N Pipeline.This article presented in detail each data processing step of the MRS-N Pipeline,such as removing cosmic rays,merging single exposure,fitting sky light emission lines,wavelength recalibration,subtracting skylight,measuring nebular parameters,creating catalogs and packing spectra.Finally,a description of the data products,including nebular spectra files and parameter catalogs,is provided.展开更多
Olivine and pyroxene are important mineral end-members for studying the surface material compositions of mafic bodies.The profiles of visible and near-infrared spectra of olivine-orthopyroxene mixtures systematically ...Olivine and pyroxene are important mineral end-members for studying the surface material compositions of mafic bodies.The profiles of visible and near-infrared spectra of olivine-orthopyroxene mixtures systematically vary with their composition ratios.In our experiments,we combine the RELAB spectral database with new spectral data obtained from some assembled olivine-orthopyroxene mixtures.We found that the commonly-used band area ratio(BAR,Cloutis et al.)does not work well on our newly obtained spectral data.To investigate this issue,an empirical procedure based on fitted results by a modified Gaussian model is proposed to analyze the spectral curves.Following the new empirical procedure,the endmember abundances can be estimated with a 15%accuracy with some prior mineral absorption features.In addition,the mixture samples configured in our experiments are also irradiated by pulsed lasers to simulate and investigate the space weathering effects.Spectral deconvolution results confirm that low-content olivine on celestial bodies is difficult to measure and estimate.Therefore,the olivine abundance of space weathered materials may be underestimated from remote sensing data.This study may be utilized to quantify the spectral relationship of olivine-orthopyroxene mixtures and further reveal their correlation between the spectra of ordinary chondrites and silicate asteroids.展开更多
Accurate radial velocity determinations of optical emission lines(i.e.,[NⅡ]λλ6548,6584,Hαand[SⅡ]λλ6717,6731)are very important for investigating the kinematic and dynamic properties of nebulae.The second stage ...Accurate radial velocity determinations of optical emission lines(i.e.,[NⅡ]λλ6548,6584,Hαand[SⅡ]λλ6717,6731)are very important for investigating the kinematic and dynamic properties of nebulae.The second stage survey program of Large sky Area Multi-Object fiber Spectroscopic Telescope(LAMOST)has started a sub-survey of nebulae(MRS-N)which will spectroscopically observe the optical emission lines of a large sample of nebulae near the Galactic plane.Until now,15 MRS-N plates have been observed from September 2017 to June 2019.Based on fitting the sky emission lines in the red band spectra of MRS-N,we investigate the precision of wavelength calibration and find there are systematic deviations of radial velocities(RVs)from~0.2 to 4 km s^(-1) for different plates.Especially for the plates obtained in March 2018,the systematic deviations of RVs can be as large as~4 km s^(-1),which then go down to~0.2-0.5 kms^(-1) at the end of 2018 and January 2019.An RV calibration function is proposed for these MRS-N plates,which can simultaneously and successfully calibrate the systematic deviations and improve the precision of RVs.展开更多
We report a multi-wavelength study of two evolved planetary nebulae(PNs)M 2–55 and Abell 2.Deep optical narrow-band images([O III],Hα,and[N II])of M 2–55 reveal two pairs of bipolar lobes and a new faint arc-like s...We report a multi-wavelength study of two evolved planetary nebulae(PNs)M 2–55 and Abell 2.Deep optical narrow-band images([O III],Hα,and[N II])of M 2–55 reveal two pairs of bipolar lobes and a new faint arc-like structure.This arc-shaped filament around M 2–55 appears as a well-defined boundary from southwest to southeast,strongly suggesting that this nebula is in interaction with its surrounding interstellar medium.From the imaging data of Wide-field Infrared Survey Explorer(WISE)all-sky survey,we discovered extensive mid-infrared halos around these PNs,which are approximately twice the size of their main nebulae seen in the visible.We also present a mid-resolution optical spectrum of M 2–55,which shows that it is a high-excitation evolved PN with a low electron density of 250 cm^-3.Furthermore,we investigate the properties of these nebulae from their spectral energy distributions(SEDs)by means of archival data.展开更多
We introduce a method of subtracting geocoronal Hαemissions from the spectra of LAMOST medium-resolution spectral survey of Galactic nebulae(LAMOST-MRS-N).The flux ratios of the Hαsky line to the adjacent OHλ6554 s...We introduce a method of subtracting geocoronal Hαemissions from the spectra of LAMOST medium-resolution spectral survey of Galactic nebulae(LAMOST-MRS-N).The flux ratios of the Hαsky line to the adjacent OHλ6554 single line do not show a pattern or gradient distribution in a plate.More interestingly,the ratio is well correlated to solar altitude,which is the angle of the Sun relative to the Earth’s horizon.It is found that the ratio decreases from 0.8 to 0.2 with the decreasing solar altitude from–17 to–73 degree.Based on this relation,which is described by a linear function,we can construct the Hαsky component and subtract it from the science spectrum.This method has been applied to the LAMOST-MRSN data,and the contamination level of the Hαsky to nebula is reduced from 40%to less than 10%.The new generated spectra will significantly improve the accuracy of the classifications and the measurements of physical parameters of Galactic nebulae.展开更多
In deriving the physical properties of asteroids from their photometric data, the scattering law plays an important role, although the shape variations of asteroids result in the main variations in lightcurves. By fol...In deriving the physical properties of asteroids from their photometric data, the scattering law plays an important role, although the shape variations of asteroids result in the main variations in lightcurves. By following the physical behaviors of light reflections, Hapke et al. deduced complex functions to represent the scattering process, however, it is very hard to accurately simulate the surface scattering law in reality. For simplicity, other numerical scattering models are presented for efficiently calculating the physical properties of asteroids, such as the Lommel-Seeliger (LS) model. In this article, these two models are compared numerically. It is found that in some numerical applications the LS model in simple form with four parameters can be exploited to replace the Hapke model in complex form with five parameters. Furthermore, the generated synthetic lightcurves by the Cellinoid shape model also show that the LS model can perform as well as the Hapke model in the inversion process. Finally, by applying the Principal Component Analysis (PCA) technique to the parameters of the LS model, we present an efficient method to classify C and S type asteroids, instead of the conventional method using the parameters of the Hapke model.展开更多
基金C.-H.H.thanks supports from the Hong Kong Research Grants Council for GRF research support under the grants 17326116 and 17300417。
文摘We carry out an optical morphological and infrared spectral study for two young planetary nebulae(PNs)Hen2-158 and Pe 1-1 to understand their complex shapes and dust properties.Hubble Space Telescope optical images reveal that these nebulae have several bipolar-lobed structures and a faint arc with a clear boundary is located at the northwestern side of Pe 1-1.The presence of this arc-shaped structure suggests that the object interacts with its nearby interstellar medium.Spitzer IRS spectroscopic observations of these young nebulae clearly show prominent unidentified infrared emission features and a weak silicate band in Pe 1-1,indicating that Hen 2-158 is a carbonrich nebula and Pe 1-1 has a mixed chemistry dust environment.Furthermore,we construct two three-dimensional models for these PNs to realize their intrinsic structures.The simulated models of the nebulae suggest that multipolar nebulae may be more numerous than we thought.Our analyses of spectral energy distributions for Hen 2-158 and Pe 1-1 show that they have low luminosities and low stellar effective temperatures,suggesting that these nebulae are young PNs.A possible correlation between typical multipolar young PNs and nested nebulae is also discussed.
基金supported by the National Natural Science Foundation of China(Grant Nos.12073051,12090040,12090041,11733006,11403061,11903048,U1631131,11973060,12090044,12073039,11633009,U1531118,11403037,11225316,11173030,11303038,Y613991N01,U1531245,11833006)the Key Laboratory of Optical Astronomy,National Astronomical Observatories,Chinese Academy of Sciences+4 种基金the Key Research Program of Frontier Sciences,CAS(Grant No.QYZDY-SSW-SLH007)the supports from the Science and Technology Development Fund,Macao SAR(file No.0007/2019/A)Faculty Research Grants of the Macao University of Science and Technology(No.FRG19-004-SSI)a National Major Scientific Project built by the Chinese Academy of SciencesFunding for the project has been provided by the National Development and Reform Commission。
文摘Since Sep.2018,LAMOST has started the medium-resolution(R~7500)spectral survey(MRS).We proposed the spectral survey of Galactic nebulae,including HⅡregions,HH objects,supernova remnants,planetary nebulae and the special stars with MRS(LAMOST MRS-N).LAMOST MRS-N covers about 1700 square degrees of the northern Galactic plane within 40°<l<215°and-5°<b<5°.In this 5-year survey,we plan to observe about 500 thousand nebulae spectra.According to the commissioning observations,the nebulae spectra can provide precise radial velocity with uncertainty less than 1 km s^(-1).These high-precision spectral data are of great significance to our understanding of star formation and evolution.
基金supported by the National Natural Science Foundation of China (Grant Nos. 12073051, 11973004, 12090040, 12090041, 11733006, 11403061, 11903048, U1631131, 11973060, 12090044, 12073039, 11633009, and U1531118)the Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences+2 种基金the Key Research Program of Frontier Sciences, CAS (Grant No. QYZDY-SSW- SLH007)supports from the Science and Technology Development Fund, Macao SAR (file No. 0007/ 2019/A)Faculty Research Grants of the Macao University of Science and Technology (No. FRG- 19-004-SSI)。
文摘The spectral observations and analysis for the W80 region are presented by using the data of Medium-Resolution Spectroscopic Survey of Nebulae(MRS-N) with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST).A total of 2982 high-quality nebular spectra have been obtained in the 20 square degree field of view which covers the W80 complex,and the largest sample of spectral data has been established for the first time.The relative intensities,radial velocities(RVs),and full widths at half maximum(FWHMs) are measured with the high spectral resolution of LAMOST MRS-N,for Ha λ6563?,[NⅡ] λλ6548 A,6584 A,and [SⅡ] λλ6716A,6731 A emission lines.In the field of view of the whole W80 region,the strongest line emissions are found to be consistent with the bright nebulae NGC 7000,IC 5070,and LBN 391,and weak line emissions also exist in the Middle Region,where no bright nebulae are detected by the wide-band optical observations.The large-scale spectral observations of the W80 region reveal the systematic spatial variations of RVs and FWHMs,and several unique structural features.A "curved feature" to the east of NGC 7000,and a "jet feature" to the west of LBN 391 are detected to be showing larger RVs.A "wider FWHM region" is identified in the eastern part of NGC 7000.The variations of[S Ⅱ]/Ha ratios display a gradient from southwest to northeast in the NGC 7000 region,and manifest a ring shape around the "W80 bubble" ionized by an O-type star in L935.Further spectral and multi-band observations are guaranteed to investigate in detail the structural features.
基金supported by the National Key R&D Program of China(2017YFA0402704)the National Natural Science Foundation of China(Grant Nos.11733006,11403061,11903048,U1631131,11973060,U1531118,11403037,11225316,11173030,11303038,Y613991N01 and U1531245)+3 种基金the Key Laboratory of Optical Astronomy,National Astronomical Observatories,Chinese Academy of Sciences,Key Research Program of Frontier Sciences,CAS(Grant No.QYZDY-SSWSLH007)supports from the Science and Technology Development Fund,Macao SAR(file Nos.119/2017/A3,061/2017/A2 and 0007/2019/A)Faculty Research Grants of the Macao University of Science and Technology(No.FRG-19-004-SSI)Guo Shou Jing Telescope(the Large Sky Area MultiObject Fiber Spectroscopic Telescope LAMOST)is a National Major Scientific Project built by the Chinese Academy of Sciences.Funding for the project has been provided by the National Development and Reform Commissionpartially supported by the Open Project Program of the Key Laboratory of Optical Astronomy,National Astronomical Observatories,Chinese Academy of Sciences.
文摘We obtained seven spectra of the Be star V423 Aur on 2017 Dec.5 using the LAMOST MediumResolution Spectrograph with exposures from 600 to 1200 seconds.These spectra show the irregular Ha emission line profile variations(LPVs).In the seven spectra,from the 4 th to 7 th,the left part of Ha profile even shows excess.However,no variation can be seen from the follow-up observation of photometry by 1.26-m telescope and High-Resolution spectra by 2.16-m telescope.According to the High-Resolution spectra,we conclude that it is a B7 V type star with E(B-V)=0.709±0.036 and its vsini is221.8 km s-1.The short-term Ha LPVs could be explained as a result of the transient ejection of matter from rotating disk or shell around V423 Aur.
基金supported by the National Natural Science Foundation of China (Grant Nos. 12073051, 12090041, 12090040, 11733006, 11403061, 11903048, U1631131, 11973060, 12090044, 12073039, 11633009 and U1531118)the Key Laboratory of Optical Astronomy+4 种基金National Astronomical ObservatoriesChinese Academy of Sciencesthe Key Research Program of Frontier Sciences, CAS (Grant No. QYZDY-SSW- SLH007)supports from the Science and Technology Development Fund, Macao SAR (file No. 0007/ 2019/A)Faculty Research Grants of the Macao University of Science and Technology (No. FRG- 19-004-SSI)。
文摘The Large sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST) medium-resolution spectral survey of Galactic Nebulae(MRS-N) has conducted for more than three years since 2018 September and observed more than190 thousand nebular spectra and 20 thousand stellar spectra.However,there is not yet a data processing pipeline for nebular spectra.To significantly improve the accuracy of nebulae classification and their physical parameters,we developed the MRS-N Pipeline.This article presented in detail each data processing step of the MRS-N Pipeline,such as removing cosmic rays,merging single exposure,fitting sky light emission lines,wavelength recalibration,subtracting skylight,measuring nebular parameters,creating catalogs and packing spectra.Finally,a description of the data products,including nebular spectra files and parameter catalogs,is provided.
基金supported by the Foundation of the State Key Laboratory of Lunar and Planetary Sciences, Macao University of Science and Technology, Macao, Chinafunded by The Science and Technology Development Fund, Macao SAR (No. 0073/2019/A2)+2 种基金the support from The Science and Technology Development Fund, Macao SAR (No. 0007/2019/A)supported by Beijing Municipal Science and Technology Commission (No. Z181100002918003)supported by the National Natural Science Foundation of China (NSFC, Nos. 11773023, 11941001, 12073024 and U1631124)
文摘Olivine and pyroxene are important mineral end-members for studying the surface material compositions of mafic bodies.The profiles of visible and near-infrared spectra of olivine-orthopyroxene mixtures systematically vary with their composition ratios.In our experiments,we combine the RELAB spectral database with new spectral data obtained from some assembled olivine-orthopyroxene mixtures.We found that the commonly-used band area ratio(BAR,Cloutis et al.)does not work well on our newly obtained spectral data.To investigate this issue,an empirical procedure based on fitted results by a modified Gaussian model is proposed to analyze the spectral curves.Following the new empirical procedure,the endmember abundances can be estimated with a 15%accuracy with some prior mineral absorption features.In addition,the mixture samples configured in our experiments are also irradiated by pulsed lasers to simulate and investigate the space weathering effects.Spectral deconvolution results confirm that low-content olivine on celestial bodies is difficult to measure and estimate.Therefore,the olivine abundance of space weathered materials may be underestimated from remote sensing data.This study may be utilized to quantify the spectral relationship of olivine-orthopyroxene mixtures and further reveal their correlation between the spectra of ordinary chondrites and silicate asteroids.
基金supported by the National Key R&D Program of China(Grant No.2017YFA0402704)the National Natural Science Foundation of China(Grant Nos.11903048,12090041,12090040,11833006,12073051,11733006,11403061,U1531118,11973060,U1631131 and 11873057)+4 种基金the NAOC Nebula Talents Program and the Key Research Program of Frontier Sciences,CAS(Grant No.QYZDYSSW-SLH007)supports from The Science and Technology Development Fund,Macao SAR(file No.061/2017/A2 and 0007/2019/A)Faculty Research Grants of the Macao University of Science and Technology(program No.FRG-19-004-SSI)Guoshoujing Telescope(the Large Sky Area MultiObject Fiber Spectroscopic Telescope,LAMOST)is a National Major Scientific Project built by the Chinese Academy of SciencesFunding for the project has been provided by the National Development and Reform Commission。
文摘Accurate radial velocity determinations of optical emission lines(i.e.,[NⅡ]λλ6548,6584,Hαand[SⅡ]λλ6717,6731)are very important for investigating the kinematic and dynamic properties of nebulae.The second stage survey program of Large sky Area Multi-Object fiber Spectroscopic Telescope(LAMOST)has started a sub-survey of nebulae(MRS-N)which will spectroscopically observe the optical emission lines of a large sample of nebulae near the Galactic plane.Until now,15 MRS-N plates have been observed from September 2017 to June 2019.Based on fitting the sky emission lines in the red band spectra of MRS-N,we investigate the precision of wavelength calibration and find there are systematic deviations of radial velocities(RVs)from~0.2 to 4 km s^(-1) for different plates.Especially for the plates obtained in March 2018,the systematic deviations of RVs can be as large as~4 km s^(-1),which then go down to~0.2-0.5 kms^(-1) at the end of 2018 and January 2019.An RV calibration function is proposed for these MRS-N plates,which can simultaneously and successfully calibrate the systematic deviations and improve the precision of RVs.
基金supported by MoST grant(108-2112-M-008-001)support of the staff of the Lijiang 2.4m telescope+4 种基金Funding for the telescope has been provided by Chinese Academy of Sciences and the People’s Government of Yunnan ProvinceFinancial support for this work is supported by the grants from The Science and Technology Development Fund,Macao SAR(file no061/2017/A2and 0007/2019/A)the Faculty Research Grants of Macao University of Science and Technology(project codeFRG-19-004-SSI)supported by the National Natural Science Foundation of China(NSFC,Grant No.U1731122)NSFC(Grant No.11973099)for financial support
文摘We report a multi-wavelength study of two evolved planetary nebulae(PNs)M 2–55 and Abell 2.Deep optical narrow-band images([O III],Hα,and[N II])of M 2–55 reveal two pairs of bipolar lobes and a new faint arc-like structure.This arc-shaped filament around M 2–55 appears as a well-defined boundary from southwest to southeast,strongly suggesting that this nebula is in interaction with its surrounding interstellar medium.From the imaging data of Wide-field Infrared Survey Explorer(WISE)all-sky survey,we discovered extensive mid-infrared halos around these PNs,which are approximately twice the size of their main nebulae seen in the visible.We also present a mid-resolution optical spectrum of M 2–55,which shows that it is a high-excitation evolved PN with a low electron density of 250 cm^-3.Furthermore,we investigate the properties of these nebulae from their spectral energy distributions(SEDs)by means of archival data.
基金the National Natural Science Foundation of China(NSFC,Nos.12090041,12090044,12090040,12073051,11733006,11903048 and 11973060)the National Key R&D Program of China(Grant No.2017YFA0402704)+2 种基金support from the Science and Technology Development Fund,MacauSAR(No.0007/2019/A)supported by Key Research Program of Frontier Sciences,Chinese Academy of Sciences(No.QYZDY-SSW-SLH007)the Guangxi Natural Science Foundation(No.2019GXNSFFA245008)。
文摘We introduce a method of subtracting geocoronal Hαemissions from the spectra of LAMOST medium-resolution spectral survey of Galactic nebulae(LAMOST-MRS-N).The flux ratios of the Hαsky line to the adjacent OHλ6554 single line do not show a pattern or gradient distribution in a plate.More interestingly,the ratio is well correlated to solar altitude,which is the angle of the Sun relative to the Earth’s horizon.It is found that the ratio decreases from 0.8 to 0.2 with the decreasing solar altitude from–17 to–73 degree.Based on this relation,which is described by a linear function,we can construct the Hαsky component and subtract it from the science spectrum.This method has been applied to the LAMOST-MRSN data,and the contamination level of the Hαsky to nebula is reduced from 40%to less than 10%.The new generated spectra will significantly improve the accuracy of the classifications and the measurements of physical parameters of Galactic nebulae.
基金funded under grant Nos. 095/2013/A3 and 039/2013/A2 from the Science and Technology Development Fundsupported partly by the Key Laboratory of Planetary Sciences+2 种基金supported by the MSAR Science and Technology Fund (Project No. 017/2014/A1)support of the National Natural Science Foundation of China (Grant Nos. 11633009, 11273067 and 10503013)the Minor Planet Foundation of Purple Mountain Observatory
文摘In deriving the physical properties of asteroids from their photometric data, the scattering law plays an important role, although the shape variations of asteroids result in the main variations in lightcurves. By following the physical behaviors of light reflections, Hapke et al. deduced complex functions to represent the scattering process, however, it is very hard to accurately simulate the surface scattering law in reality. For simplicity, other numerical scattering models are presented for efficiently calculating the physical properties of asteroids, such as the Lommel-Seeliger (LS) model. In this article, these two models are compared numerically. It is found that in some numerical applications the LS model in simple form with four parameters can be exploited to replace the Hapke model in complex form with five parameters. Furthermore, the generated synthetic lightcurves by the Cellinoid shape model also show that the LS model can perform as well as the Hapke model in the inversion process. Finally, by applying the Principal Component Analysis (PCA) technique to the parameters of the LS model, we present an efficient method to classify C and S type asteroids, instead of the conventional method using the parameters of the Hapke model.