检索结果-南通市图书馆

The radio structure of BL Lac object S5 2007+777

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2010年第S1期53卷 187-190页

作者： WU ZhongZu1,3,gu minfeng2 & chen YongJun2 1 College of Science,guizhou University,guiyang 550025,china 2 key laboratory for research in galaxies and cosmology,shanghai astronomical observatory,chinese academy of sciences,shanghai 200030,china 3 NAOC-GZU Sponsored Center for Astronomy,guizhou University,guiyang 550025,china guizhou Univ Coll Sci Guiyang 550025 Peoples R China chinese Acad Sci Shanghai Astron Observ Key Lab Res Galaxies & Cosmol Shanghai 200030 Peoples R China guizhou Univ NAOC GZU Sponsored Ctr Astron Guiyang 550025 Peoples R China

BL Lac object S5 2007+777 has been classified as a HYMOR(Hybrid Morphology radio source) for its hybrid FR I and FR II radio *** is one of four BL Lac objects with a kpc scale extended X-ray *** this paper,we searched the unpublished European VLBI Network(EVN) archived high resolution data for this source,and present the high resolution radio *** EVN images all show a core-jet structure in 1.6,5 and 8 *** combination with the VLA data in the literature,we found position angle differences(△PA) of about 10°-20° between pc and kpc scale jet *** brightness temperature estimated from multi-band EVN images are around 1011.2-1011.8 K,from which the Doppler factor ranges from 3.2 to *** found significant flux variations of the radio core in 1.6 and 5 GHz,from which we derived the variability in brightness temperature Tvar to be 1013.6 K and 1014.0 K,corresponding to the Doppler factors of 9.3 and 12.4,respectively.

关键词： active galactic nuclei VLBI BL Lac objects

Establishing HI mass vs. stellar mass and halo mass scaling relations using an abundance matching method

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2024年第11期67卷 149-163页

作者： Yi Lu Xiaohu Yang chengze Liu Haojie Xu Antonios Katsianis Hong guo Xiaoju Xu Yizhou gu key laboratory for research in galaxies and cosmology Shanghai Astronomical ObservatoryChinese Academy of SciencesShanghai 200030China Tsung-Dao Lee Institute and Shanghai Key Laboratory for Particle Physics and CosmologyShanghai Jiao Tong UniversityShanghai 200240China Department of Astronomy School of Physics and AstronomyShanghai Jiao Tong UniversityShanghai 200240China School of Physics and Astronomy Sun Yat-sen UniversityZhuhai CampusZhuhai 519082China

We combined data from the Sloan Digital Sky Survey(SDSS) and the Arecibo Legacy Fast ALFA Survey(ALFALFA) to establish the HI mass vs. stellar mass and halo mass scaling relations using an abundance matching method that is free of the Malmquist bias. To enable abundance matching, a cross-match between the SDSS DR7 galaxy group sample and the ALFALFA HI sources provides a catalog of 16520 HI-galaxy pairs within 14270 galaxy groups(halos). By applying the observational completeness reductions for both optical and HI observations, we used the remaining 8180 ALFALFA matched sources to construct the model constraints. Taking into account the dependence of HI mass on both the galaxy and group properties, we establish two sets of scaling relations: one with a combination of stellar mass,(g-r) color and halo mass, and the other with stellar mass,specific star-formation rate(sSFR), and halo mass. We demonstrate that our models can reproduce the HI mass component as both stellar mass and halo mass. Additional tests showed that the conditional HI mass distributions as a function of the cosmic web type and the satellite fractions were well recovered.

关键词： galaxy groups neutral hydrogen halos statistical

Preparation for CSST:Star-galaxy Classification using a Rotationally Invariant Supervised Machine Learning Method

在线全文

学校读者我要写书评

暂无评论

research in Astronomy and Astrophysics 2024年第9期24卷 136-146页

作者： Shiliang Zhang guanwen Fang Jie Song Ran Li Yizhou gu Zesen Lin Chichun Zhou Yao Dai Xu Kong Institute of Astronomy and Astrophysics Anqing Normal UniversityAnqing 246133China Deep Space Exploration laboratory/Department of Astronomy University of Science and Technology of ChinaHefei 230026China School of Astronomy and Space Science University of Science and Technology of ChinaHefei 230026China National astronomical Observatories Chinese Academy of SciencesBeijing 100101China Tsung-Dao Lee Institute and key laboratory for Particle Physics Astrophysics and CosmologyMinistry of EducationShanghai Jiao Tong UniversityShanghai 200240China Department of Physics The Chinese University of Hong KongShatinN.T.Hong KongS.A.R.China School of Engineering Dali UniversityDali 671003China

Most existing star-galaxy classifiers depend on the reduced information from catalogs,necessitating careful data processing and feature *** this study,we employ a supervised machine learning method(GoogLeNet)to automatically classify stars and galaxies in the COSMOS *** traditional machine learning methods,we introduce several preprocessing techniques,including noise reduction and the unwrapping of denoised images in polar coordinates,applied to our carefully selected samples of stars and *** dividing the selected samples into training and validation sets in an 8:2 ratio,we evaluate the performance of the GoogLeNet model in distinguishing between stars and *** results indicate that the GoogLeNet model is highly effective,achieving accuracies of 99.6% and 99.9% for stars and galaxies,***,by comparing the results with and without preprocessing,we find that preprocessing can significantly improve classification accuracy(by approximately 2.0% to 6.0%)when the images are *** preparation for the future launch of the china Space Station Telescope(CSST),we also evaluate the performance of the GoogLeNet model on the CSST simulation *** results demonstrate a high level of accuracy(approximately 99.8%),indicating that this model can be effectively utilized for future observations with the CSST.

关键词： methods:data analysis techniques:image processing stars:imaging

Primordial black hole mass functions as a probe of cosmic origin

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2024年第5期67卷 164-171页

作者： Yi-Fu Cai chengfeng Tang Geyu Mo Sheng-Feng Yan Chao chen Xiao-Han Ma Bo Wang Wentao Luo Damien A.Easson Antonino Marcianò Deep Space Exploration laboratory/School of Physical sciences University of Science and Technology of ChinaHefei 230026China CAS key laboratory for researches in galaxies and cosmology/Department of Astronomy School of Astronomy and Space ScienceUniversity of Science and Technology of ChinaHefei 230026China Istituto Nazionale di Fisica Nucleare(INFN) Sezione di MilanoMilano 20146Italy DiSAT Universitàdegli Studi dell'InsubriaComo 22100Italy Jockey Club Institute for Advanced Study The Hong Kong University of Science and TechnologyHong KongChina Department of Physics Arizona State UniversityTempe 85287-1504USA Department of Physics&Center for Field Theory and Particle Physics Fudan UniversityShanghai 200433China Laboratori Nazionali di Frascati INFN Via Enrico Fermi 541 Frascati(Roma)00044Italy INFN sezione Roma Tor Vergata Rome I-00133Italy School of Physics University of Electronic Science and Technology of ChinaChengdu11731China

We discuss a novel window to probe the origin of our universe via the mass functions of primordial black holes(PBHs).The mass functions of PBHs are simply estimated using the conventional Press-Schechter formalism for two paradigms of cosmic origin,including inflationaryΛCDM and bounce *** standard inflationaryΛCDM model cannot generate an appreciable number of massive PBHs;however,non-trivial inflation models with blue-tilted power spectra at small scales and matter bounce cosmology provide formation mechanisms for heavy PBHs,which in turn,may seed the observed supermassive black holes(SMBHs).By fitting the SMBH mass functions at high redshift(z~6)derived from Sloan Digital Sky Survey(SDSS)and Canada-France High-z Quasar Survey(CFHQS)quasars,for two paradigms of cosmic origin,we derive constraints on the PBH density fraction fPBHat z~6 and the characteristic mass M_(★),with the prior assumption that all SMBHs stem from *** demonstrate that this newly proposed procedure,relying on astronomical measurements that utilize deep-field surveys of SMBHs at high redshift,can be used to constrain models of cosmic ***,although not the main focus of this paper,we evolve the mass function from z~6 to z~0 through an assumption of 3×10^(8)-year Eddington’s accretion,and give a rough estimation of fPBHat z~0.

关键词： origin cosmic massive

The pc-scale radio structure of MIR-observed radio galaxies

在线全文

学校读者我要写书评

暂无评论

research in Astronomy and Astrophysics 2018年第9期18卷 31-46页

作者： Ye Yuan Min-Feng gu Yong-Jun chen shanghai astronomical observatory Chinese Academy of SciencesShanghai 200030China key laboratory for research in galaxies and cosmology Shanghai Astronomical ObservatoryChinese Academy of SciencesShanghai 200030China University of chinese academy of sciences Beijing 100049China key laboratory of Radio Astronomy Chinese Academy of SciencesNanjing 210008China

We investigated the relationship between the accretion process and jet properties by utilizing very long baseline array （VLBA） and mid-infrared （MIR） data for a sample of 45 3CRR radio galaxies selected with a flux density at 178MHz 〉 16.4Jy, 5 GHz very large array （VLA） core flux density ≥7 mJy and MIR observations. The pc-scale radio structure at 5 GHz is presented by using our VLBA observations for 21 sources acquired in February, 2016, the analysis of archival data for 16 objects and directly obtaining measurements for eight radio galaxies available from literatures. The accretion mode is constrained from the Eddington ratio with a dividing value of 0.01, which is estimated from the MIR-based bolometric luminosity and the black hole masses. While most Fanaroff-Riley type II radio galaxies （FRIIs） have higher Eddington ratio than Fanaroff-Riley type I radio galaxies （FRIs）, we found that there is indeed no single correspondence between the FR morphology and accretion mode with eight FRIIs at low accretion rate and two FRIs at high accretion rate. There is a significant correlation between the VLBA core luminosity at 5 GHz and the Eddington ratio. Various morphologies are identi- fied in our sample, including core only, single-sided core-jet and two-sided core-jet structures. We found that the higher accretion rate may be more likely related with the core-jet structure, thus generating a more extended jet. These results imply that the higher accretion rates are likely able to produce more powerful jets. There is a strong correlation between the MIR luminosity at 15 ktm and VLBA 5 GHz core luminosity, in favor of the tight relation between the accretion disk and jets. In our sample, the core brightness temperature ranges from 109 to 101338 K with a median value of 10^11.09K, indicating that systematically the beaming effect may not be significant. The exceptional cases, FRIs at high accretion rates and FRIIs at low accretion rates, are exclusively at the high and l

关键词： galaxies active - galaxies structure - galaxies general --radio continuum galaxies

The broad wing of the [O Ⅲ] λ5007 emission line in active galactic nuclei

在线全文

学校读者我要写书评

暂无评论

research in Astronomy and Astrophysics 2014年第8期14卷 913-922页

作者： Zhi-Xin Peng Yan-Mei chen Qiu-Sheng gu Kai Zhang School of Astronomy and Space Science Nanjing University key laboratory of Modern Astronomy and Astrophysics (Nanjing University) Ministry of Education key laboratory for research in galaxies and cosmology Shanghai Astronomical ObservatoryChinese Academy of Sciences

We use a sample of type 2 active galactic nuclei （AGNs） from SDSS DR7 in which the [O Ⅲ] ）λ5007 emission line can be modeled by two Gaussian components, a broad wing plus a narrow core, to investigate the origin of the broad wing and the connection between the velocity shift of the broad wing and the physical parameters of AGNs, as well as their host galaxies. We find that the flux of the wing components is statistically roughly equal to that of the core components. However, the velocity shift of the wing component has only weak, if any, correlations with the physical properties of AGNs and the host galaxies, such as bolometric luminosity, the Eddington ratio, the mass of supermassive black holes, D4000, H3A or stellar mass. Comparing the velocity shift from our type 2 AGN sample to that from the type 1 sample in Zhang et al., we suggest that the [O Ⅲ]] broad wing originates from outflow.

关键词： galaxies: active -- galaxies: Seyfert -- quasars: emission lines

在线全文

学校读者我要写书评

暂无评论

The FAST Core Array

astronomical Techniques and Instruments 2024年第2期1卷 84-94页

作者： Peng Jiang Rurong chen Hengqian Gan Jinghai Sun Boqin Zhu Hui Li Weiwei Zhu Jingwen Wu Xuelei chen Haiyan Zhang Tao An National astronomical Observatories Chinese Academy of SciencesBeijing 100101China guizhou Radio astronomical observatory Guizhou UniversityGuiyang 550000China shanghai astronomical observatory Chinese Academy of SciencesShanghai 200030China

The Five-hundred-meter Aperture Spherical Radio Telescope(FAST)Core Array is a proposed extension of FAST,integrating 24 secondary 40-m antennas implanted within 5 km of the FAST *** original array design will combine the unprecedented sensitivity of FAST with a high angular resolution(4.3"at a frequency of 1.4 GHz),thereby exceeding the capabilities at similar frequencies of next-generation arrays such as the Square Kilometre Array Phase 1 or the next-generation Very Large *** article presents the technical specifications of the FAST Core Array,evaluates its potential relatively to existing radio telescope arrays,and describes its expected scientific *** proposed array will be equipped with technologically advanced backend devices,such as real-time signal processing systems.A phased array feed receiver will be mounted on FAST to improve the survey efficiency of the FAST Core Array,whose broad frequency coverage and large field of view(FOV)will be essential to study transient cosmic phenomena such as fast radio bursts and gravitational wave events,to conduct surveys and resolve structures in neutral hydrogen galaxies,to monitor or detect pulsars,and to investigate exoplanetary ***,the FAST Core Array can strengthen china's major role in the global radio astronomy community,owing to a wide range of potential scientific applications from cosmology to exoplanet science.

关键词： FAST Radio telescope Interferometry Synthesis array

SDSS spectroscopy for blazars in the Fermi LAT bright AGN sample

在线全文

学校读者我要写书评

暂无评论

research in Astronomy and Astrophysics 2009年第11期9卷 1192-1204页

作者： Zhao-Yu chen Min-Feng gu Zhong-Hui Fan Xin-Wu Cao key laboratory for research in galaxies and cosmology Shanghai Astronomical ObservatoryChinese Academy of Sciences Shanghai 200030 China Graduate University of chinese academy of sciences Beijing 100049 China Department of Physics Yunnan University Kunming 650091 China

We have collected all available spectra and photometric data from the SDSS catalog for bright AGNs complied from the first three months of the Fermi large area telescope all-sky survey. Based on the 106 high-confidence and 11 low-confidence associated bright AGN list, the photometry data are collected from SDSS DR7 for 28 sources （12 BL Lacs and 16 FSRQs）, two of which are low-confidence associated bright AGNs. Among these 28 SDSS photometric sources, SDSS spectra are available for 20 sources （6 BL Lacs and 14 FSRQs）. The black hole masses MBH and the broad line region （BLR） luminosity were obtained for 14 FSRQs by measuring the line-widths and strengths of broad emission lines from the SDSS spectra. The broad emission line measurements of five FSRQs are presented for the first time in this work. The optical continuum emission of these 14 FSRQs is found to be likely dominated by the non-thermal jet emission by comparing the relationship between the broad Mg II line and continuum luminosity to that of radio-quiet AGNs. The black hole mass of the 14 FSRQs ranges from 10^8.2 M⊙ to 10^9.9 M⊙, with most of the sources larger than 10^9 M⊙. The Eddington ratio Lbol/LEdd ranges from 10-1＇5 to - 1. This implies that an optically thin, geometrically thick accretion disk may exist in these FSRQs.

关键词： galaxies active -- galaxies nuclei -- gamma rays observations -- quasars emission lines -- BL Lacertae objects general

Relations between integrated and monochromatic luminosities of flat-spectrum radio quasars

在线全文

学校读者我要写书评

暂无评论

research in Astronomy and Astrophysics 2011年第4期11卷 401-410页

作者： Zhi-Fu chen Zhao-Yu chen Yi-Ping Qin Min-Feng gu Lian-Zhong LU cheng-Yue Su You-Bing Li Ye chen Center for Astrophysics Guangzhou University Guangzhou 510006 China epartment of Astronomy Peking University Beijing 100871 China key laboratory for research in galaxies and cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030 China Physics Department Guangxi University Nanning 530004 China Department of Physics Guangdong University of-Technology Guangzhou 530004 China guangzhou City Construction College Guangzhou 530004. China

We employ a sample of 362 flat-spectrum radio quasars （FSRQs） to calculate their integrated luminosities by integrating the spectral energy distribution （SED） constructed with multi-band （radio, IR, optical, UV and X-ray） data. We compare these luminosities with those estimated from monochromatic luminosities by multi- plying them by the conventional bolometric correction factors. Our analysis shows that the integrated luminosities calculated from the SED are much larger than the bolometric luminosities estimated from monochromatic luminosities. Their departing behavior tightly correlates with radio luminosities. The relations between integrated and monochromatic luminosities are explored, which are regarded as empirical rela- tions that might be more suitable to be applied to estimate integrated luminosities of FSRQs from their monochromatic luminosities.

关键词： methods statistical -- galaxies active -- galaxies jets