利用从斯隆数字巡天（Sloan Digital Sky Survey，简称SDSS）第4次释放的光谱数据中选取的10^5个发射线星系样本，研究了[OII]λ3727／Hα流量比与星系尘埃消光、气体电离态和金属丰度的关系．发现尘埃消光改正对[OII]λ3727／Hα谱线...利用从斯隆数字巡天（Sloan Digital Sky Survey，简称SDSS）第4次释放的光谱数据中选取的10^5个发射线星系样本，研究了[OII]λ3727／Hα流量比与星系尘埃消光、气体电离态和金属丰度的关系．发现尘埃消光改正对[OII]λ3727／Hα谱线流量比影响显著，消光改正前、后的[OII]λ3727／Hα谱线流量比的中值分别为0．48和0．89；尘埃消光改正后，F（[OII]λ3727）-F（Hα）的弥散显著减小．贫金属星系的[OII]λ3727／Hα谱线流量比随星系气体的电离度增高而减小，而富金属星系不存在这种关系．另外，[OII]λ3727／Hα流量比与星系金属丰度相关．当12＋lg（O／H）〉8．5时，星系[OII]λ3727／Hα流量比随金属丰度增加而下降；12＋lg（O／H）〈8．5的星系，谱线流量比与金属丰度正相关．最后，利用气体电离度参数和星系的金属丰度，给出了计算不同类型星系[OII]λ3727／Hα流量比的公式．LAMOST望远镜将观测到大量红移z〉0．4的星系光谱，利用该公式可以给出星系的[OII]λ3727／Hα流量比，从而可以利用[OII]λ3727谱线流量计算z〉0．4星系的恒星形成率．展开更多
通过利用CANDELS-EGS(Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey-Extended Groth Strip)场中HST WFC3(Hubble Space Telescope Wide Field Camera 3)F160W高分辨率的观测图像,研究了9个光谱红极亮红外星系的形...通过利用CANDELS-EGS(Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey-Extended Groth Strip)场中HST WFC3(Hubble Space Telescope Wide Field Camera 3)F160W高分辨率的观测图像,研究了9个光谱红极亮红外星系的形态结构特征.发现这些星系的形态表现出多样性(从椭圆到多个亮核或弥散的结构),如:双核,气体桥,双不对称体,不规则或椭圆结构.为了定量地研究这些极亮红外星系的形态,测量了它们在静止光学波段的形态参数(基尼系数G和矩指数M20).与近邻极亮红外星系相比,高红移极亮红外星系的G偏小而M20偏大,表明这些星系的星族分布聚集度小且不对称性大.基于对样本中极亮红外星系2维面亮度轮廓的拟合,得到这些星系的有效半径分布在2.4 kpc到5.8 kpc之间,其平均值是(3.9±1.1)kpc.相比较于近邻相似质量的恒星形成星系来说,高红移极亮红外星系的平均大小要小1到2倍.在类似红移和红外光度条件下,得出的这些结果也与其它文献中给出的结论相一致.展开更多
基于CANDELS(Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey)5个深场巡天的多波段测光数据和HST WFC3(Hubble Space Telescope Wide Field Camera 3)近红外(F125W和F160W)高分辨率观测图像,利用质量限(恒星质量M_*&g...基于CANDELS(Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey)5个深场巡天的多波段测光数据和HST WFC3(Hubble Space Telescope Wide Field Camera 3)近红外(F125W和F160W)高分辨率观测图像,利用质量限(恒星质量M_*>10^(10)M_⊙)选取了8002个红移分布在1<z<3范围内的星系样本,并对这些大质量星系的形态和结构性质进行了定量分析研究.通过星系形态的神经网络分类方法(Conv Nets),将样本中的星系划分为4类:椭球星系(SPHeroids,SPH)、早型盘星系(Early-Type Disks,ETD)、晚型盘星系(Late-Type Disks,LTD)和不规则星系(IRRegulars,IRR).结果发现星系的形态和结构随红移发生演化,在高红移宇宙星系主要表现出不规则形态,但到低红移处椭球和盘主导的哈勃星系形态序列已经形成.在相同红移区间内,不同类型星系的物理尺寸(r_e)中值从大到小的排序是IRR、LTD、ETD和SPH,而对应的Sersic指数(n)中值大小排序却相反.另外,不同类型星系的re与红移之间存在明显的演化关系,但这样的现象在平均轴比(b/a)和Sersic指数与红移的关系中并没有被发现.展开更多
In this work, predictions of the spectral energy distribution from populations of single and binary stars are incorporated into a galactic chemical and color evolution model to explore the significance of the effects ...In this work, predictions of the spectral energy distribution from populations of single and binary stars are incorporated into a galactic chemical and color evolution model to explore the significance of the effects of the binary interactions on the color evolution of M33. We first constructed a model without binary interactions, and the model is able to reproduce most of the available observational constraints on the distribution of stellar parameters. We then run simulations with the same set of model parameters but with binary interactions considered. By comparing the results for the populations with and without binary interactions, we find that the inclusion of binary interactions makes the surface brightness greater (~0.1 mag arcsec 2) in FUV-band but smaller (~0.7 mag arcsec 2) in K-band, while it results in the FUV K color bluer (~0.8 mag). To reproduce the observations, a model that considers the binary interactions should make more gas fall onto the disk in the early time of the galaxy evolution, or increase the total stellar mass, or both.展开更多
Contact binary systems,including massive,middle-mass and low-mass systems,have been observed.It is necessary to construct the evolutionary model for contact binary systems with all different masses.The model introduce...Contact binary systems,including massive,middle-mass and low-mass systems,have been observed.It is necessary to construct the evolutionary model for contact binary systems with all different masses.The model introduced by Huang,Song and Bi indicates some special and unique understandings of the physical processes occurring in the contact binaries.It is necessary to test whether this model can be applied to the early-type contact binaries.The best way to test a theoretical model is to know whether this model can explain the observational phenomena of such binaries.For this aim,a comparison is performed for the relations of mass-luminosity,mass-radius,and the distribution in the HR diagram obtained from the model introduced by Huang et al.and those from the astronomical observations.A good result is obtained by the comparison.This means the model can be used in calculating the evolution of early-type contact binaries,and can explain the observational phenomena of such binaries.展开更多
We perform numerical simulations to investigate tidal evolution of two single-planet systems, that is, WASP-50 and GJ 1214 and a two-planet system CoRoT-7. The results of orbital evolution show that tidal decay and ci...We perform numerical simulations to investigate tidal evolution of two single-planet systems, that is, WASP-50 and GJ 1214 and a two-planet system CoRoT-7. The results of orbital evolution show that tidal decay and circularization may play a significant role in shaping their final orbits, which is related to the initial orbital data in the simulations. For GJ 1214 system, different cases of initial eccentricity are also considered as only an upper limit of its eccentricity （0.27） is shown, and the outcome suggests a possible maximum initial eccentricity （0.4） in the adopted dynamical model. Moreover, additional runs with alternative values of dissipation factor Q＇I are carried out to explore tidal evolution for GJ 1214b, and these results further indicate that the real Q＇1 of GJ 1214b may be much larger than its typical value, which may reasonably suggest that GJ 1214b bears a present-day larger eccentricity, undergoing tidal circularization at a slow rate. For the CoRoT-7 system, tidal forces make two planets migrating towards their host star as well as producing tidal circularization, and in this process tidal effects and mutual gravitational interactions are coupled with each other. Various scenarios of the initial eccentricity of the outer planet have also been done to investigate final planetary configuration. Tidal decay arising from stellar tides may still work for each system as the eccentricity decreases to zero, and this is in association with the remaining lifetime of each planet used to predict its future.展开更多
文摘利用从斯隆数字巡天（Sloan Digital Sky Survey，简称SDSS）第4次释放的光谱数据中选取的10^5个发射线星系样本，研究了[OII]λ3727／Hα流量比与星系尘埃消光、气体电离态和金属丰度的关系．发现尘埃消光改正对[OII]λ3727／Hα谱线流量比影响显著，消光改正前、后的[OII]λ3727／Hα谱线流量比的中值分别为0．48和0．89；尘埃消光改正后，F（[OII]λ3727）-F（Hα）的弥散显著减小．贫金属星系的[OII]λ3727／Hα谱线流量比随星系气体的电离度增高而减小，而富金属星系不存在这种关系．另外，[OII]λ3727／Hα流量比与星系金属丰度相关．当12＋lg（O／H）〉8．5时，星系[OII]λ3727／Hα流量比随金属丰度增加而下降；12＋lg（O／H）〈8．5的星系，谱线流量比与金属丰度正相关．最后，利用气体电离度参数和星系的金属丰度，给出了计算不同类型星系[OII]λ3727／Hα流量比的公式．LAMOST望远镜将观测到大量红移z〉0．4的星系光谱，利用该公式可以给出星系的[OII]λ3727／Hα流量比，从而可以利用[OII]λ3727谱线流量计算z〉0．4星系的恒星形成率．
文摘星系的光谱包含其内部恒星的年龄和金属丰度等信息,从观测光谱数据中测量这些信息对于深入了解星系的形成和演化至关重要.LAMOST(Large Sky Area Multi-Object Fiber Spectroscopic Telescope)巡天发布了大量的星系光谱,这些高维光谱与它们的物理参数之间存在着高度的非线性关系.而深度学习适合于处理多维、海量的非线性数据,因此基于深度学习技术构建了一个8个卷积层+4个池化层+1个全连接层的卷积神经网络,对LAMOST Data Release 7(DR7)星系的年龄和金属丰度进行自动估计.实验结果表明,使用卷积神经网络通过星系光谱预测的星族参数与传统方法基本一致,误差在0.18dex以内,并且随着光谱信噪比的增大,预测误差越来越小.实验还对比了卷积神经网络与随机森林回归模型、深度神经网络的参数测量结果,结果表明卷积神经网络的结果优于其他两种回归模型.
文摘通过利用CANDELS-EGS(Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey-Extended Groth Strip)场中HST WFC3(Hubble Space Telescope Wide Field Camera 3)F160W高分辨率的观测图像,研究了9个光谱红极亮红外星系的形态结构特征.发现这些星系的形态表现出多样性(从椭圆到多个亮核或弥散的结构),如:双核,气体桥,双不对称体,不规则或椭圆结构.为了定量地研究这些极亮红外星系的形态,测量了它们在静止光学波段的形态参数(基尼系数G和矩指数M20).与近邻极亮红外星系相比,高红移极亮红外星系的G偏小而M20偏大,表明这些星系的星族分布聚集度小且不对称性大.基于对样本中极亮红外星系2维面亮度轮廓的拟合,得到这些星系的有效半径分布在2.4 kpc到5.8 kpc之间,其平均值是(3.9±1.1)kpc.相比较于近邻相似质量的恒星形成星系来说,高红移极亮红外星系的平均大小要小1到2倍.在类似红移和红外光度条件下,得出的这些结果也与其它文献中给出的结论相一致.
文摘基于CANDELS(Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey)5个深场巡天的多波段测光数据和HST WFC3(Hubble Space Telescope Wide Field Camera 3)近红外(F125W和F160W)高分辨率观测图像,利用质量限(恒星质量M_*>10^(10)M_⊙)选取了8002个红移分布在1<z<3范围内的星系样本,并对这些大质量星系的形态和结构性质进行了定量分析研究.通过星系形态的神经网络分类方法(Conv Nets),将样本中的星系划分为4类:椭球星系(SPHeroids,SPH)、早型盘星系(Early-Type Disks,ETD)、晚型盘星系(Late-Type Disks,LTD)和不规则星系(IRRegulars,IRR).结果发现星系的形态和结构随红移发生演化,在高红移宇宙星系主要表现出不规则形态,但到低红移处椭球和盘主导的哈勃星系形态序列已经形成.在相同红移区间内,不同类型星系的物理尺寸(r_e)中值从大到小的排序是IRR、LTD、ETD和SPH,而对应的Sersic指数(n)中值大小排序却相反.另外,不同类型星系的re与红移之间存在明显的演化关系,但这样的现象在平均轴比(b/a)和Sersic指数与红移的关系中并没有被发现.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11033008 and 10821061)the Chinese Academy of Sciences (Grant No. KJCX2-YW-T24)
文摘In this work, predictions of the spectral energy distribution from populations of single and binary stars are incorporated into a galactic chemical and color evolution model to explore the significance of the effects of the binary interactions on the color evolution of M33. We first constructed a model without binary interactions, and the model is able to reproduce most of the available observational constraints on the distribution of stellar parameters. We then run simulations with the same set of model parameters but with binary interactions considered. By comparing the results for the populations with and without binary interactions, we find that the inclusion of binary interactions makes the surface brightness greater (~0.1 mag arcsec 2) in FUV-band but smaller (~0.7 mag arcsec 2) in K-band, while it results in the FUV K color bluer (~0.8 mag). To reproduce the observations, a model that considers the binary interactions should make more gas fall onto the disk in the early time of the galaxy evolution, or increase the total stellar mass, or both.
基金supported by the National Natural Science Foundation of China (Grant No.10933002)
文摘Contact binary systems,including massive,middle-mass and low-mass systems,have been observed.It is necessary to construct the evolutionary model for contact binary systems with all different masses.The model introduced by Huang,Song and Bi indicates some special and unique understandings of the physical processes occurring in the contact binaries.It is necessary to test whether this model can be applied to the early-type contact binaries.The best way to test a theoretical model is to know whether this model can explain the observational phenomena of such binaries.For this aim,a comparison is performed for the relations of mass-luminosity,mass-radius,and the distribution in the HR diagram obtained from the model introduced by Huang et al.and those from the astronomical observations.A good result is obtained by the comparison.This means the model can be used in calculating the evolution of early-type contact binaries,and can explain the observational phenomena of such binaries.
基金supported by the National Natural Science Foundation of China (Grant No.10973044,10833001)the Natural Science Foundation of Jiangsu Province(Grant No.BK20093411)the Foundation of Minor Planets of the Purple Mountain Observatory
文摘We perform numerical simulations to investigate tidal evolution of two single-planet systems, that is, WASP-50 and GJ 1214 and a two-planet system CoRoT-7. The results of orbital evolution show that tidal decay and circularization may play a significant role in shaping their final orbits, which is related to the initial orbital data in the simulations. For GJ 1214 system, different cases of initial eccentricity are also considered as only an upper limit of its eccentricity （0.27） is shown, and the outcome suggests a possible maximum initial eccentricity （0.4） in the adopted dynamical model. Moreover, additional runs with alternative values of dissipation factor Q＇I are carried out to explore tidal evolution for GJ 1214b, and these results further indicate that the real Q＇1 of GJ 1214b may be much larger than its typical value, which may reasonably suggest that GJ 1214b bears a present-day larger eccentricity, undergoing tidal circularization at a slow rate. For the CoRoT-7 system, tidal forces make two planets migrating towards their host star as well as producing tidal circularization, and in this process tidal effects and mutual gravitational interactions are coupled with each other. Various scenarios of the initial eccentricity of the outer planet have also been done to investigate final planetary configuration. Tidal decay arising from stellar tides may still work for each system as the eccentricity decreases to zero, and this is in association with the remaining lifetime of each planet used to predict its future.
