Weak gravitational lensing is a powerful tool in modern cosmology.To accurately measure the weak lensing signal,one has to control the systematic bias on a small level.One of the most difficult problems is how to corr...Weak gravitational lensing is a powerful tool in modern cosmology.To accurately measure the weak lensing signal,one has to control the systematic bias on a small level.One of the most difficult problems is how to correct the smearing effect of the Point-Spread Function(PSF)on the shape of the galaxies.The chromaticity of PSF for a broad-band observation can lead to new subtle effects.Since the PSF is wavelength-dependent and the spectrum energy distributions between stars and galaxies are different,the effective PSF measured from the star images will be different from those that smear the galaxies.Such a bias is called color bias.We estimate it in the optical bands of the Chinese Space Station Survey Telescope from simulated PSFs,and show the dependence on the color and redshift of the galaxies.Moreover,due to the spatial variation of spectra over the galaxy image,another higher-order bias exists:color gradient bias.Our results show that both color bias and color gradient bias are generally below 0.1%in CSST.Only for small-size galaxies,one needs to be careful about the color gradient bias in the weak lensing analysis using CSST data.展开更多
Eu3+ions doped Zn(OH)F and ZnO micro-structures with specific morphologies were synthesized by a simple hydrothermal method only through altering the addition amount of NH4F and hexamethylenetetramine(HMT).The phase s...Eu3+ions doped Zn(OH)F and ZnO micro-structures with specific morphologies were synthesized by a simple hydrothermal method only through altering the addition amount of NH4F and hexamethylenetetramine(HMT).The phase structure,morphology and luminescence properties of the as-prepared samples were characterized by X-ray powder diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),photoluminescence(PL)spectra and lifetime.The results indicate that the obtained Zn(OH)F:Eu^3+samples possess net-like and dandelion-like morphologies,which have an identical orthorhombic phase structure.It is found that the addition amount of raw materials such as NH4F and HMT plays a critical role for the formation of Zn(OH)F:Eu^3+.If the addition amounts of NH4F or HMT are reduced by half,the hexagonal ZnO:Eu^3+sample with peanut-like morphology can be obtained.Under the excitation of UV light,both the as-prepared Zn(OH)F:Eu^3+and ZnO:Eu^3+samples exhibit the characteristic emission of the doped Eu^3+.展开更多
CePO_(4):Tb^(3+)nanorods were successfully obtained via a simple hydrothermal method and combined with carbon dots(CDs)to obtain CDs@CePO_(4):Tb^(3+)nanorods.Due to the combination of CDs,the emission intensity of CDs...CePO_(4):Tb^(3+)nanorods were successfully obtained via a simple hydrothermal method and combined with carbon dots(CDs)to obtain CDs@CePO_(4):Tb^(3+)nanorods.Due to the combination of CDs,the emission intensity of CDs@CePO_(4):Tb^(3+)nanorods increases about 92 times,compared with that of CePO_(4):Tb^(3+)nanorods.The combination of CDs and CePO_(4):Tb^(3+)nanorods was confirmed by Fourier transform infrared spectroscopy(FTIR),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS)and so on.The mechanism of luminescence enhancement may be attributed to some aspects:the formation of hexagonal phase results in the increase of crystal field symmetry,and the energy transfer among CDs,Ce^(3+)and Tb^(3+)ions,which causes the Tb^(3+)ions in CDs@CePO_(4):Tb^(3+)nano rods to obtain mo re excited energy and less non-radiative atte nuation co mpared to CePO_(4):Tb^(3+)nano rods.The luminescence enhancement strategy through combination of CDs would provide a simple and effective approach for other rare earth ions doped luminescent materials.展开更多
基金funded by the National Natural Science Foundation of China(NSFC)under Nos.11873006,11933002,11903082,and U1931210the science research grants from the China Manned Space Project with Nos.CMS-CSST-2021-A01,CMS-CSST-2021A12,and CMS-CSST-2021-A07。
文摘Weak gravitational lensing is a powerful tool in modern cosmology.To accurately measure the weak lensing signal,one has to control the systematic bias on a small level.One of the most difficult problems is how to correct the smearing effect of the Point-Spread Function(PSF)on the shape of the galaxies.The chromaticity of PSF for a broad-band observation can lead to new subtle effects.Since the PSF is wavelength-dependent and the spectrum energy distributions between stars and galaxies are different,the effective PSF measured from the star images will be different from those that smear the galaxies.Such a bias is called color bias.We estimate it in the optical bands of the Chinese Space Station Survey Telescope from simulated PSFs,and show the dependence on the color and redshift of the galaxies.Moreover,due to the spatial variation of spectra over the galaxy image,another higher-order bias exists:color gradient bias.Our results show that both color bias and color gradient bias are generally below 0.1%in CSST.Only for small-size galaxies,one needs to be careful about the color gradient bias in the weak lensing analysis using CSST data.
基金Project supported by the National Natural Science Foundation of China(51572303)
文摘Eu3+ions doped Zn(OH)F and ZnO micro-structures with specific morphologies were synthesized by a simple hydrothermal method only through altering the addition amount of NH4F and hexamethylenetetramine(HMT).The phase structure,morphology and luminescence properties of the as-prepared samples were characterized by X-ray powder diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),photoluminescence(PL)spectra and lifetime.The results indicate that the obtained Zn(OH)F:Eu^3+samples possess net-like and dandelion-like morphologies,which have an identical orthorhombic phase structure.It is found that the addition amount of raw materials such as NH4F and HMT plays a critical role for the formation of Zn(OH)F:Eu^3+.If the addition amounts of NH4F or HMT are reduced by half,the hexagonal ZnO:Eu^3+sample with peanut-like morphology can be obtained.Under the excitation of UV light,both the as-prepared Zn(OH)F:Eu^3+and ZnO:Eu^3+samples exhibit the characteristic emission of the doped Eu^3+.
基金Project supported by the National Natural Science Foundation of China(51572303,52002117)。
文摘CePO_(4):Tb^(3+)nanorods were successfully obtained via a simple hydrothermal method and combined with carbon dots(CDs)to obtain CDs@CePO_(4):Tb^(3+)nanorods.Due to the combination of CDs,the emission intensity of CDs@CePO_(4):Tb^(3+)nanorods increases about 92 times,compared with that of CePO_(4):Tb^(3+)nanorods.The combination of CDs and CePO_(4):Tb^(3+)nanorods was confirmed by Fourier transform infrared spectroscopy(FTIR),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS)and so on.The mechanism of luminescence enhancement may be attributed to some aspects:the formation of hexagonal phase results in the increase of crystal field symmetry,and the energy transfer among CDs,Ce^(3+)and Tb^(3+)ions,which causes the Tb^(3+)ions in CDs@CePO_(4):Tb^(3+)nano rods to obtain mo re excited energy and less non-radiative atte nuation co mpared to CePO_(4):Tb^(3+)nano rods.The luminescence enhancement strategy through combination of CDs would provide a simple and effective approach for other rare earth ions doped luminescent materials.
