With the exceptional sensitivity of the Five-hundred-meter Aperture Spherical radio Telescope,we conducted observations of the neutral hydrogen(HⅠ)in the circumgalactic medium of Andromeda’s(M31)satellite galaxies,s...With the exceptional sensitivity of the Five-hundred-meter Aperture Spherical radio Telescope,we conducted observations of the neutral hydrogen(HⅠ)in the circumgalactic medium of Andromeda’s(M31)satellite galaxies,specifically AndromedaⅡ,NGC 205,and NGC 185.Initially,three drift scans were executed for these satellites,with a detection limit of 4×10^(18)cm^(-2)(approximately 1.88×10^(3)M_Θof HⅠmass),followed by a more in-depth scan of a specific region.We discovered a C-shaped HⅠarc structure sharing a position and line-of-sight velocity similar to a stellar ring structure around AndromedaⅡ,hinting at a potential connection with AndromedaⅡ.In the context of NGC 205,we identified two mass concentrations in the northeast direction,which could be indicative of tidal streams resulting from the interaction between this galaxy and M31.These new lumps discovered could be very helpful in solving the missing interstellar medium problem for NGC 205.Observations regarding NGC 185are consistent with previous studies,and we did not detect any additional HⅠmaterial around this galaxy.These observational results enhance our understanding of the evolution of these satellite galaxies and provide insight into their historical interactions with the galaxy M31.展开更多
We present an analysis of the winding sense（S and Z-shapes） of 1 621 field galaxies that have radial velocity between 3 000 km s-1 and 5 000 km s-1.The preferred alignments of S-and Z-shaped galaxies are studied usi...We present an analysis of the winding sense（S and Z-shapes） of 1 621 field galaxies that have radial velocity between 3 000 km s-1 and 5 000 km s-1.The preferred alignments of S-and Z-shaped galaxies are studied using chi-square,autocorrelation and Fourier series tests.We classify all the galaxies into 32 subsamples and notice a good agreement between the position angle（PA） distribution of the S-and Zshaped galaxies.The homogeneous distribution of the S-and Z-shaped galaxies is more noticeable for the late-type spirals（Sc,Scd,Sd and Sm） than for the early-types（Sa,Sab,Sb and Sbc） .A significant dominance of S-mode galaxies is apparent in the barred spirals.A random alignment is evident in the PA-distribution of Z-and S-mode spirals.In addition,a homogeneous distribution of the S-and Z-shaped galaxies is found to be invariant under global expansion.The PA-distribution of the total S-mode galaxies is found to be random,whereas a preferred alignment is clear for all the Zmode galaxies.It is found that the galactic planes of Z-mode galaxies tend to lie in the equatorial plane.展开更多
The abundance of neutral hydrogen（HI）in satellite galaxies in the local group is important for studying the formation history of our local group.In this work,we generated mock HI satellite galaxies in the Local Grou...The abundance of neutral hydrogen（HI）in satellite galaxies in the local group is important for studying the formation history of our local group.In this work,we generated mock HI satellite galaxies in the Local Group using the high mass-resolution hydrodynamic APOSTLE simulation.The simulated HI mass function agrees with the ALFALFA survey very well above 10~6M_⊙,although there is a discrepancy below this scale because of the observed flux limit.After carefully checking various systematic elements in the observations,including fitting of line width,sky coverage,integration time and frequency drift due to uncertainty in a galaxy’s distance,we predicted the abundance of HI in galaxies in a future survey that will be conducted by FAST.FAST has a larger aperture and higher sensitivity than the Arecibo telescope.We found that the HI mass function could be estimated well around 10~5M_⊙ if the integration time is 40 minutes.Our results indicate that there are 61 HI satellites in the Local Group and 36 in the FAST field above 10~5M_⊙.This estimation is one order of magnitude better than the current data,and will put a strong constraint on the formation history of the Local Group.Also more high resolution simulated samples are needed to achieve this target.展开更多
The lack of Birkhoff theorem in finite-range gravitation reveals nonzero acceleration of the test body inside the massive spherical shell, as well as breakdown of screening inside the charged conductor gives rise to a...The lack of Birkhoff theorem in finite-range gravitation reveals nonzero acceleration of the test body inside the massive spherical shell, as well as breakdown of screening inside the charged conductor gives rise to acceleration of the test charge. An application of this effect to the motion of galaxies in Local Group allows to constraint quintessence parameter in some massive gravitational theories.展开更多
A spectral analysis of the vertical positions and velocities of 374 open star clusters(OSCs)was carried out.We took these OSCs from the Hunt and Reffert catalog;they have an average age of about 10 million years,and a...A spectral analysis of the vertical positions and velocities of 374 open star clusters(OSCs)was carried out.We took these OSCs from the Hunt and Reffert catalog;they have an average age of about 10 million years,and are located on the galactic plane XY in a narrow zone inclined by 25°to the galactic axis Y.The following estimates of the parameters of the Radcliffe wave were obtained:(a)the maximum value in periodic perturbations of vertical coordinates Z_(max)=92±10pc with the wavelength of these perturbations λ_(z)=4.82±0.09 kpc;(b)the maximum value of the velocity of vertical disturbances Wmax=4.36±0.12km s^(-1) with disturbance wavelengthλ_(W)=1.78±0.02 kpc.Note that the results of the vertical velocity analysis are first-class in accuracy and completely new.展开更多
We present a catalog of 908 objects observed with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope（LAMOST） in fields in the vicinity of M31 and M33, targeted as globular clusters（GCs） and candidates. ...We present a catalog of 908 objects observed with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope（LAMOST） in fields in the vicinity of M31 and M33, targeted as globular clusters（GCs） and candidates. The targets include known GCs and candidates selected from the literature, as well as new candidates selected from the Sloan Digital Sky Survey（SDSS）. Analysis shows that 356 of them are likely GCs with various confidence levels, while the remaining ones turn out to be background galaxies and quasars, stars and H II regions in M31 or foreground Galactic stars. The 356 likely GCs include 298 bona fide GCs and 26 candidates known in the literature. Three candidates, selected from the Revised Bologna Catalog of M31 GCs and candidates（RBC） and one possible cluster from Johnson et al., are confirmed to be bona fide clusters. We search for new GCs in the halo of the M31 among the new candidates selected from the SDSS photometry. Based on radial velocities yielded by LAMOST spectra and visual examination of the SDSS images, we find 28 objects, 5bona fide and 23 likely GCs. Among the five bona fide GCs, three have been recently discovered independently by others, and the remaining 25 are our new identifications,including two bona fide ones. The newly identified objects fall at projected distances ranging from 13 to 265 kpc from M31. Of the two newly discovered bona fide GCs,one is located near M33, probably a GC belonging to M33. The other bona fide GC falls on the Giant Stream with a projected distance of 78 kpc from M31. Of the 23 newly identified likely GCs, one has a projected distance of about 265 kpc from M31 and could be an intergalactic cluster.展开更多
We study the subhalo and satellite populations in haloes similar to the Milky Way(MW)-Andromeda paired configuration in the Millennium II and P-Millennium simulations.We find subhaloes are 5%–15%more abundant in pair...We study the subhalo and satellite populations in haloes similar to the Milky Way(MW)-Andromeda paired configuration in the Millennium II and P-Millennium simulations.We find subhaloes are 5%–15%more abundant in paired haloes than their isolated counterparts that have the same halo mass and large-scale environmental density.Paired haloes tend to reside in a more isotropic environment than isolated haloes,the shear tensor of their large-scale tidal field is possibly responsible for this difference.We also study the thickness of the spatial distribution of the top 11 most massive satellite galaxies obtained in the semi-analytic galaxy sample constructed from the Millennium II simulation.Moreover,satellites that have lost their host subhaloes due to the resolution limit of the simulation have been taken into account.As a result,we find that the difference in the distribution of the satellite thickness between isolated and paired haloes is indistinguishable,which suggests that the paired configuration is not responsible for the observed plane of satellites in the MW.The results in this study indicate the paired configuration could bring some nonnegligible effect on the subhalo abundance in the investigation of the MW's satellite problems.展开更多
This paper presents a novel spectroscopic method for searching for supernova candidates from massive galaxy spectra,which is expected to be applied to the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAM...This paper presents a novel spectroscopic method for searching for supernova candidates from massive galaxy spectra,which is expected to be applied to the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST).This method includes mainly five steps.The first step is spectral preprocessing,including removing spectral noise using wavelet transform,spectral de-redshift,etc.The second step is decomposition of galactic spectra;we can get the galaxy component and supernova component and calculate the Supernova Statistical Characterization Vector (SNSCV) of each galaxy spectrum.The third step is to decrease samples in all the galaxy spectral datasets according to SNSCV of each spectrum,and to use the LOF (Local Outlier Factor)-based outlier detection algorithm to obtain the preliminary selected spectral data.The fourth step is template matching by cross-correlation,according to the matched results we get the secondary selected spectral data.Finally,we choose the final supernova candidates manually through checking the spectral features characteristic of a supernova.By the spectroscopic method proposed in this paper,thirty-six supernova candidates have been detected in a dataset including 294843 galaxy spectra from the Sloan Digital Sky Survey Data Release 7.Nine of these objects are detected first and the other twenty-seven have been reported in other publications (fifteen of which are detected and reported first by us).The twenty-four new super-nova candidates include twenty Ia type supernova candidates,three Ic type supernova candidates and one II type supernova candidate.展开更多
基金support of the China National Key Program for Science and Technology Research and Development of China(2022YFA1602901)the National Natural Science Foundation of China(NSFC,Grant Nos.11988101 and 11873051)+3 种基金the CAS Project for Young Scientists in Basic Research grant(No.YSBR-062)the K.C.Wong Education Foundationthe science research grants from the China Manned Space Projectsupport from the Cultivation Project for FAST Scientific Payoff and Research Achievement of CAMS-CAS。
文摘With the exceptional sensitivity of the Five-hundred-meter Aperture Spherical radio Telescope,we conducted observations of the neutral hydrogen(HⅠ)in the circumgalactic medium of Andromeda’s(M31)satellite galaxies,specifically AndromedaⅡ,NGC 205,and NGC 185.Initially,three drift scans were executed for these satellites,with a detection limit of 4×10^(18)cm^(-2)(approximately 1.88×10^(3)M_Θof HⅠmass),followed by a more in-depth scan of a specific region.We discovered a C-shaped HⅠarc structure sharing a position and line-of-sight velocity similar to a stellar ring structure around AndromedaⅡ,hinting at a potential connection with AndromedaⅡ.In the context of NGC 205,we identified two mass concentrations in the northeast direction,which could be indicative of tidal streams resulting from the interaction between this galaxy and M31.These new lumps discovered could be very helpful in solving the missing interstellar medium problem for NGC 205.Observations regarding NGC 185are consistent with previous studies,and we did not detect any additional HⅠmaterial around this galaxy.These observational results enhance our understanding of the evolution of these satellite galaxies and provide insight into their historical interactions with the galaxy M31.
文摘We present an analysis of the winding sense（S and Z-shapes） of 1 621 field galaxies that have radial velocity between 3 000 km s-1 and 5 000 km s-1.The preferred alignments of S-and Z-shaped galaxies are studied using chi-square,autocorrelation and Fourier series tests.We classify all the galaxies into 32 subsamples and notice a good agreement between the position angle（PA） distribution of the S-and Zshaped galaxies.The homogeneous distribution of the S-and Z-shaped galaxies is more noticeable for the late-type spirals（Sc,Scd,Sd and Sm） than for the early-types（Sa,Sab,Sb and Sbc） .A significant dominance of S-mode galaxies is apparent in the barred spirals.A random alignment is evident in the PA-distribution of Z-and S-mode spirals.In addition,a homogeneous distribution of the S-and Z-shaped galaxies is found to be invariant under global expansion.The PA-distribution of the total S-mode galaxies is found to be random,whereas a preferred alignment is clear for all the Zmode galaxies.It is found that the galactic planes of Z-mode galaxies tend to lie in the equatorial plane.
基金support by China Program of International S&T Cooperation(2016YFE0100300)support by the National Natural Science Foundation of China(NSFC,Grant Nos.11633004,11390372,11303008 and 11773034)+1 种基金the 973 program grant 2015CB857005the NSFC(No.11373029)
文摘The abundance of neutral hydrogen（HI）in satellite galaxies in the local group is important for studying the formation history of our local group.In this work,we generated mock HI satellite galaxies in the Local Group using the high mass-resolution hydrodynamic APOSTLE simulation.The simulated HI mass function agrees with the ALFALFA survey very well above 10~6M_⊙,although there is a discrepancy below this scale because of the observed flux limit.After carefully checking various systematic elements in the observations,including fitting of line width,sky coverage,integration time and frequency drift due to uncertainty in a galaxy’s distance,we predicted the abundance of HI in galaxies in a future survey that will be conducted by FAST.FAST has a larger aperture and higher sensitivity than the Arecibo telescope.We found that the HI mass function could be estimated well around 10~5M_⊙ if the integration time is 40 minutes.Our results indicate that there are 61 HI satellites in the Local Group and 36 in the FAST field above 10~5M_⊙.This estimation is one order of magnitude better than the current data,and will put a strong constraint on the formation history of the Local Group.Also more high resolution simulated samples are needed to achieve this target.
文摘The lack of Birkhoff theorem in finite-range gravitation reveals nonzero acceleration of the test body inside the massive spherical shell, as well as breakdown of screening inside the charged conductor gives rise to acceleration of the test charge. An application of this effect to the motion of galaxies in Local Group allows to constraint quintessence parameter in some massive gravitational theories.
文摘A spectral analysis of the vertical positions and velocities of 374 open star clusters(OSCs)was carried out.We took these OSCs from the Hunt and Reffert catalog;they have an average age of about 10 million years,and are located on the galactic plane XY in a narrow zone inclined by 25°to the galactic axis Y.The following estimates of the parameters of the Radcliffe wave were obtained:(a)the maximum value in periodic perturbations of vertical coordinates Z_(max)=92±10pc with the wavelength of these perturbations λ_(z)=4.82±0.09 kpc;(b)the maximum value of the velocity of vertical disturbances Wmax=4.36±0.12km s^(-1) with disturbance wavelengthλ_(W)=1.78±0.02 kpc.Note that the results of the vertical velocity analysis are first-class in accuracy and completely new.
基金supported by the National Basic Research Program of China (973 Program, 2014CB845700)the China Postdoctoral Science Foundation (2014M560843)
文摘We present a catalog of 908 objects observed with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope（LAMOST） in fields in the vicinity of M31 and M33, targeted as globular clusters（GCs） and candidates. The targets include known GCs and candidates selected from the literature, as well as new candidates selected from the Sloan Digital Sky Survey（SDSS）. Analysis shows that 356 of them are likely GCs with various confidence levels, while the remaining ones turn out to be background galaxies and quasars, stars and H II regions in M31 or foreground Galactic stars. The 356 likely GCs include 298 bona fide GCs and 26 candidates known in the literature. Three candidates, selected from the Revised Bologna Catalog of M31 GCs and candidates（RBC） and one possible cluster from Johnson et al., are confirmed to be bona fide clusters. We search for new GCs in the halo of the M31 among the new candidates selected from the SDSS photometry. Based on radial velocities yielded by LAMOST spectra and visual examination of the SDSS images, we find 28 objects, 5bona fide and 23 likely GCs. Among the five bona fide GCs, three have been recently discovered independently by others, and the remaining 25 are our new identifications,including two bona fide ones. The newly identified objects fall at projected distances ranging from 13 to 265 kpc from M31. Of the two newly discovered bona fide GCs,one is located near M33, probably a GC belonging to M33. The other bona fide GC falls on the Giant Stream with a projected distance of 78 kpc from M31. Of the 23 newly identified likely GCs, one has a projected distance of about 265 kpc from M31 and could be an intergalactic cluster.
基金supported by the National Key R&D Program of China(Nos.2018YFE0202900 and 2022YFA1602901)by the NSFC Grant(Nos.11988101,11873051,12125302 and 12273053)+6 种基金support from the K.C.Wong Education Foundationthe support of CAS Project for Young Scientists in Basic Research,grant No.YSBR-062the science research grants from the China Manned Spaced Project with No.CMS-CSST-2021-B03the support of the National Natural Science Foundation of China(Nos.12047569 and 12147217)the Natural Science Foundation of Jilin Province,China(No.20180101228JC)funded by BIS National E-infrastructure capital grant ST/K00042X/1,STFC capital grant ST/H008519/1STFC Di RAC Operations grant ST/K003267/1 and Durham University。
文摘We study the subhalo and satellite populations in haloes similar to the Milky Way(MW)-Andromeda paired configuration in the Millennium II and P-Millennium simulations.We find subhaloes are 5%–15%more abundant in paired haloes than their isolated counterparts that have the same halo mass and large-scale environmental density.Paired haloes tend to reside in a more isotropic environment than isolated haloes,the shear tensor of their large-scale tidal field is possibly responsible for this difference.We also study the thickness of the spatial distribution of the top 11 most massive satellite galaxies obtained in the semi-analytic galaxy sample constructed from the Millennium II simulation.Moreover,satellites that have lost their host subhaloes due to the resolution limit of the simulation have been taken into account.As a result,we find that the difference in the distribution of the satellite thickness between isolated and paired haloes is indistinguishable,which suggests that the paired configuration is not responsible for the observed plane of satellites in the MW.The results in this study indicate the paired configuration could bring some nonnegligible effect on the subhalo abundance in the investigation of the MW's satellite problems.
基金supported by the National Natural Science Foundation of China (Grant Nos. 60773040,10973021)
文摘This paper presents a novel spectroscopic method for searching for supernova candidates from massive galaxy spectra,which is expected to be applied to the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST).This method includes mainly five steps.The first step is spectral preprocessing,including removing spectral noise using wavelet transform,spectral de-redshift,etc.The second step is decomposition of galactic spectra;we can get the galaxy component and supernova component and calculate the Supernova Statistical Characterization Vector (SNSCV) of each galaxy spectrum.The third step is to decrease samples in all the galaxy spectral datasets according to SNSCV of each spectrum,and to use the LOF (Local Outlier Factor)-based outlier detection algorithm to obtain the preliminary selected spectral data.The fourth step is template matching by cross-correlation,according to the matched results we get the secondary selected spectral data.Finally,we choose the final supernova candidates manually through checking the spectral features characteristic of a supernova.By the spectroscopic method proposed in this paper,thirty-six supernova candidates have been detected in a dataset including 294843 galaxy spectra from the Sloan Digital Sky Survey Data Release 7.Nine of these objects are detected first and the other twenty-seven have been reported in other publications (fifteen of which are detected and reported first by us).The twenty-four new super-nova candidates include twenty Ia type supernova candidates,three Ic type supernova candidates and one II type supernova candidate.
