A recently released XMM-Newton note revealed a significant calibration issue between nuclear spectroscopic telescope array(NuSTAR)and XMM-Newton European Photon Imaging Camera(EPIC)and provided an empirical correction...A recently released XMM-Newton note revealed a significant calibration issue between nuclear spectroscopic telescope array(NuSTAR)and XMM-Newton European Photon Imaging Camera(EPIC)and provided an empirical correction to the EPIC effective area.To quantify the bias caused by the calibration issue in the joint analysis of XMM-NuSTAR spectra and verify the effectiveness of the correction,in this work,we perform joint-fitting of the NuSTAR and EPIC-pn spectra for a large sample of 104 observation pairs of 44 X-ray bright active galactic nuclei(AGN).The spectra were extracted after requiring perfect simultaneity between the XMM-Newton and NuSTAR exposures(merging good time intervals(GTIs)from two missions)to avoid bias due to the rapid spectral variability of the AGN.Before the correction,the EPIC-pn spectra are systematically harder than the corresponding NuSTAR spectra by■subsequently yielding significantly underestimated cutoff energy E_(cut)and the strength of reflection component R when performing joint-fitting.We confirm that the correction is highly effective and can commendably erase the discrepancy in best-fitΓ,E_(cut),and R.We thus urge the community to apply the correction when joint-fitting XMM-NuSTAR spectra,but note that the correction is limited to 3–12 keV and therefore not applicable when the soft X-ray band data are included.Besides,we show that as merging GTIs from two missions would cause severe loss of NuSTAR net exposure time,in many cases,joint-fitting yields no advantage compared with utilizing NuSTAR data alone.Finally,We present a technical note on filtering periods of high background flares for XMM-Newton EPIC-pn exposures in the small window(SW)mode.展开更多
基于COSMOS(Cosmic Evolution Survey)天区的多波段测光数据和HST(Hubble Space Telescope)近红外高分辨率观测图像,利用质量限(恒星质量M*≥1010.5M⊙)选取了362个红移分布在1≤z≤3的星系样本,并对这些大质量星系的形态特征进行了分...基于COSMOS(Cosmic Evolution Survey)天区的多波段测光数据和HST(Hubble Space Telescope)近红外高分辨率观测图像,利用质量限(恒星质量M*≥1010.5M⊙)选取了362个红移分布在1≤z≤3的星系样本,并对这些大质量星系的形态特征进行了分类研究.来自UVJ(U-V和V-J)双色图分类系统、目视分类系统、非模型化分类系统(基尼系数G和矩指数M20)和模型化分类系统(S′ersic index,n)的分类结果彼此相一致.相比较于恒星形成星系(SFGs),通过UVJ双色图定义的宁静星系(QGs)表现出致密的椭圆结构,而且G和n值偏大,但M20和星系有效半径(re)偏小.不同星系分类系统(双色图分类系统、非模型化分类系统和模型化分类系统)定义的SFGs和QGs样本,都明显存在星系的大小随红移的演化关系,这种演化趋势QGs比SFGs更剧烈,而且不依赖于星系分类方法的选择.展开更多
基于Sloan Digital Sky Survey(SDSS)数据,采用van den Bosch等发展的自适应方法从星系样本中挑选出中央星系及其卫星星系,然后研究卫星星系速度弥散与中央星系/卫星星系属性的关系.和之前的研究一致,卫星星系平均速度弥散随着中央星系...基于Sloan Digital Sky Survey(SDSS)数据,采用van den Bosch等发展的自适应方法从星系样本中挑选出中央星系及其卫星星系,然后研究卫星星系速度弥散与中央星系/卫星星系属性的关系.和之前的研究一致,卫星星系平均速度弥散随着中央星系质量增大而增大,并且红中央星系所在星系群的速度弥散比蓝中央星系要大.发现平均而言,在红中央星系周围,卫星星系的速度弥散和其质量之间没有明显关联.但是在蓝中央星系周围,质量大的卫星星系速度弥散偏大,而红卫星星系的速度弥散要比蓝卫星星系偏大.进一步的研究表明,在相同的暗晕中,卫星星系速度弥散和卫星星系质量并不相关.有意思的是,如果红中央星系周围同时有红和蓝卫星星系,那么红卫星星系的速度要小,对其中的物理机制进行了初步的探讨.此外还发现,若中央星系周围只有红或蓝(质量大或小)的卫星星系时,有红(或质量大)的卫星星系所在的暗晕的速度弥散要大于有蓝(或者质量小)的卫星星系的暗晕,这表明卫星星系属性对于暗晕质量测量是有影响的.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
基金supported by the National Natural Science Foundation of China(12033006,12192221,123B2042).
文摘A recently released XMM-Newton note revealed a significant calibration issue between nuclear spectroscopic telescope array(NuSTAR)and XMM-Newton European Photon Imaging Camera(EPIC)and provided an empirical correction to the EPIC effective area.To quantify the bias caused by the calibration issue in the joint analysis of XMM-NuSTAR spectra and verify the effectiveness of the correction,in this work,we perform joint-fitting of the NuSTAR and EPIC-pn spectra for a large sample of 104 observation pairs of 44 X-ray bright active galactic nuclei(AGN).The spectra were extracted after requiring perfect simultaneity between the XMM-Newton and NuSTAR exposures(merging good time intervals(GTIs)from two missions)to avoid bias due to the rapid spectral variability of the AGN.Before the correction,the EPIC-pn spectra are systematically harder than the corresponding NuSTAR spectra by■subsequently yielding significantly underestimated cutoff energy E_(cut)and the strength of reflection component R when performing joint-fitting.We confirm that the correction is highly effective and can commendably erase the discrepancy in best-fitΓ,E_(cut),and R.We thus urge the community to apply the correction when joint-fitting XMM-NuSTAR spectra,but note that the correction is limited to 3–12 keV and therefore not applicable when the soft X-ray band data are included.Besides,we show that as merging GTIs from two missions would cause severe loss of NuSTAR net exposure time,in many cases,joint-fitting yields no advantage compared with utilizing NuSTAR data alone.Finally,We present a technical note on filtering periods of high background flares for XMM-Newton EPIC-pn exposures in the small window(SW)mode.
文摘基于Sloan Digital Sky Survey(SDSS)数据,采用van den Bosch等发展的自适应方法从星系样本中挑选出中央星系及其卫星星系,然后研究卫星星系速度弥散与中央星系/卫星星系属性的关系.和之前的研究一致,卫星星系平均速度弥散随着中央星系质量增大而增大,并且红中央星系所在星系群的速度弥散比蓝中央星系要大.发现平均而言,在红中央星系周围,卫星星系的速度弥散和其质量之间没有明显关联.但是在蓝中央星系周围,质量大的卫星星系速度弥散偏大,而红卫星星系的速度弥散要比蓝卫星星系偏大.进一步的研究表明,在相同的暗晕中,卫星星系速度弥散和卫星星系质量并不相关.有意思的是,如果红中央星系周围同时有红和蓝卫星星系,那么红卫星星系的速度要小,对其中的物理机制进行了初步的探讨.此外还发现,若中央星系周围只有红或蓝(质量大或小)的卫星星系时,有红(或质量大)的卫星星系所在的暗晕的速度弥散要大于有蓝(或者质量小)的卫星星系的暗晕,这表明卫星星系属性对于暗晕质量测量是有影响的.
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.
