检索结果-南通市图书馆

Clumpy metal concentrations in elliptical galaxies NGC 4374 and NGC 4636

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2010年第3期10卷 220-226页

作者： hai-guang xu Jun-Hua Gu Li-Yi Gu Zhong-Li Zhang Yu Wang Tao An Department of Physics Shanghai Jiao Tong University Shanghai 200240 China Max-Planck Institut fur Astrophysik D-85740 Garching Germany Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030 China

We present a high spatial resolution study of metal distributions in the nearby, gas-rich elliptical galaxies NGC 4374 and NGC 4636 with the Chandra ACIS archive data. We define the hardness ratio HRFeL as the ratio of the emission in 0.65- 1.4 keV to that in 0.3-0.6 keV and 1.4-3.5 keV （after the magnesium and silicon lines are excluded）, and HRcont as the ratio of the emission in 1.4-3.5keV to that in 0.3- 0.6 keV, so that the HRFeL and HRcont maps can be used to trace the iron abundance and gas temperature distributions, respectively. By applying the a Trous wavelet algorithm to the obtained emission hardness ratio maps, we reveal that the HRFeL distributions are highly irregular, exhibiting strong spatial variations on 0.1-1 Re scales, which do not follow the HRcont distributions. Since the effect of temperature variation is small, we conclude that most of the high-HRFeL regions are very likely to possess higher abundances than the ambient gas. We also find that these high-HRFeL substructures are not associated with either the LMXB or globular cluster populations, thus their origins should be related to AGN activity or mergers.

关键词： galaxies: elliptical and lenticular cD -- galaxies: individual (NGC 4374 NGC 4636) -- galaxies: ISM -- ISM: abundances -- X-rays: galaxies

Metal enrichment via ram pressure stripping in the IGM of the compact galaxy group RGH 80

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2010年第4期10卷 301-308页

作者： hai-Juan Cui hai-guang xu Jun-Hua Gu Jing-Ying Wang Li-Yi Gu Yu Wang Zhen-Zhen Qin Tao An Department of Physics Shanghai Jiao Tong UniversityShanghai 200240China Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 200030China

By creating and analyzing two dimensional gas temperature and abundance maps of the RGH 80 compact galaxy group with high-quality Chandra data,we detect a high-abundance （ 0.7 Z⊙） arc,where the metal abundance is significantly higher than the surrounding regions by 0.3Z⊙.This structure shows tight spatial correlations with the member galaxy PGC 046529,as well as with the arm-like feature identified on the X-ray image in the previous work of Randall et al.（2009）.Since no apparent signature of AGN activity is found to be associated with PGC 046529 in multi-band observations,and the gas temperature,metallicity,and mass of the high-abundance arc resemble those of the ISM of typical early-type galaxies,we conclude that this high-abundance structure is the remnant of the ISM of PGC 046529,which was stripped out of the galaxy by ram pressure stripping due to the motion of PGC 046529 in RGH *** novel case shows that ram pressure stripping can work as efficiently in the metal enrichment process in galaxy groups as it can in galaxy clusters.

关键词： galaxies:clusters:individual (RGH 80) - galaxy:abundance - intergalactic medium - X-rays:galaxies:clusters

X-Ray Properties of the Point Source Population in the Spiral Galaxy NGC 5055 (M63) with Chandra

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Astronomy and Astrophysics 2007年第3期7卷 335-344页

作者： Bing Luo Ji-Yao Chen Zhong-Li Zhang Yu Wang Jing-Ying Wang hai-guang xu Department of Physics Fudan University Shanghai 200433 Department of Physics Shanghai Jiao Tong University Shanghai 200240

Using Chandra ACIS S3 data we studied the X-ray properties of low-and highmass X-ray binary populations in the nearby spiral galaxy NGC 5055. A total of 43 X-ray point sources were detected within two effective radii, with 31 sources located on the disk and the rest 12 sources in the bulge. The resolved point sources dominate the X-ray emission of the galaxy, accounting for about 80% of the total counts in 0.3-10keV. From spectral fittings we calculated the 0.3-10.0keV luminosities of all the detected X-ray point sources and found that they span a wide range from a few times 10^37 erg s^-1 to over 10^39 erg s^-1. After compensating for incompleteness at the low luminosity end, we found that the corrected XLF of the bulge population is well fitted with a broken power-law with a break at 1.57-0.20^＋0.21 1038 erg s^-1, while the profile of the disk population＇s XLF agrees with a single powerlaw distribution of slope 0 9-0.06^＋0.07 The disk population is significantly richer at ≥ 2 × 10^38 erg s^- 1 than the bulge population, indicating that the disk may have undergone relatively recent, strong starbursts that significantly increased the HMXB population, although ongoing starbursts are also observed in the nuclear region. Similar XLF profiles of the bulge and disk populations were found in M81. However, in most other spiral galaxies different patterns of spatial variation of the XLF profiles from the bulge to the disk have been observed, indicating that the star formation and evolution history may be more complex than we have expected.

关键词： galaxies individual (NGC 5055)-X-ray binaries-stars luminosity function-stars formation

Confirming the 115.5-day periodicity in the X-ray light curve of ULX NGC 5408 X-1

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2012年第12期12卷 1597-1602页

作者： xu Han Tao An Jun-Yi Wang Ji-Ming Lin Ming-Jie Xie hai-guang xu Xiao-Yu Hong Sandor Frey Key Laboratory of Cognitive Radio & Information Processing Ministry of Education Guilin University of Electronic Technology Guilin 541004 China Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030 China School of Mathematics and Computational Science Xiangtan University Xiangtan 411105China Key Laboratory of Radio Astronomy Chinese Academy of Sciences Nanjing 210008 China Department of Physics Shanghai Jiao Tong University Shanghai 200240 China FOMI Satellite Geodetic Observatory EO. Box 585 H-1592 Budapest Hungary

The Swift/XRT light curve of the ultraluminous X-ray source NGC 5408 X-1 was re-analyzed with two new numerical approaches, the Weighted Wavelet Ztransform and CLEANest, and the results are different from previous studies. Both techniques detected a prominent periodicity with a time scale of 115.5 ± 1.5 days, in excellent agreement with the detection of the same periodicity first reported by Strohmayer . Monte Carlo simulations were employed to test the statisitical confidence of the 115.5-day periodicity, yielding a statistical significance of 〉 99.98% （or 〉 3.8σ）. The robust detection of the 115.5-day quasi-periodic oscillations, if they are due to the orbital motion of the binary, would infer a mass of a few thousand M⊙ for the central black hole, implying there is an intermediate-mass black hole in NGC 5408 X-1.

关键词： methods: statistical - galaxies: individual (NGC 5408) - stars: oscil- lations

Central gas entropy excess as direct evidence for AGN feedback in galaxy groups and clusters

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2010年第10期10卷 1013-1022页

作者： Yu Wang hai-guang xu Jun-Hua Gu Li-Yi Gu Jing-Ying Wang Zhong-Li Zhang Department of Physics Shanghai Jiao Tong University Shanghai 200240 China Max-Planck-Institute for Astrophysics Karl-Schwarzschild-Str. 1 Postfach 1317 D-85741 Garching Germany

By analyzing Chandra X-ray data of a sample of 21 galaxy groups and 19 galaxy clusters, we find that in 31 sample systems there exists a significant central （R ≤ 10 h^-171 kpc） gas entropy excess （AK0）, which corresponds to = 0.1 - 0.5 keV per gas particle, beyond the power-law model that best fits the radial entropy profile of the outer regions. We also find a distinct correlation between the central entropy excess △K0 and K-band luminosity LK of the central dominating galaxies （CDGs）, which is scaled as △K0 ∝ L K 1.6±04, where LK is tightly associated with the mass of the supermassive black hole hosted in the CDG. In fact, if an effective mass-to-energy conversionefficiency of 0.02 is assumed for the accretion process, the cumulative AGN feedback E AGN feedack=ηMBHc2 yields an extra heating of = 0.5 - 17.0keV per particle, which feedback is sufficient to explain the central entropy excess. In most cases, the AGN contribution can compensate the radiative loss of the X-ray gas within the cooling radius （= 0.002 - 2.2 keV per particle）, and apparently exceeds the energy required to cause the scaling relations to deviate from the self-similar predictions （=0.2 - 1.0 keV per particle）. In contrast to the AGN feedback, the extra heating provided by supernova explosions accounts for = 0.01 - 0.08 keV per particle in groups and is almost negligible in clusters. Therefore, the observed correlation between △K0 and Lx can be considered as direct evidence for AGN feedback in galaxy groups and clusters.

关键词： galaxies active- galaxies clusters general -- X-rays galaxies clus-ters -- (galaxies ) intergalactic medium

External calibrator in global signal experiment for detection of the epoch of reionization

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2021年第10期21卷 17-26页

作者： Yan Huang Xiang-Ping Wu Quan Guo Qian Zheng Bi-Ying Li Huan-Yuan Shan Ke-Jia Lee hai-guang xu National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 200030China Kavli Institute for Astronomy and Astrophysics Peking UniversityBeijing 100871China School of Physics and Astronomy Shanghai Jiao Tong University800 Dongchuan RoadShanghai 200240China

We present a conceptual design study of external calibrators in the 21 cm experiment towards detecting the globally averaged radiation of the epoch of reionization(EoR).Employment of external calibrator instead of internal calibrator commonly used in current EoR experiments allows removing instrumental effects such as beam pattern,receiver gain and instability of the system if the conventional three-position switch measurements are implemented in a short time ***,in the new design the antenna system is placed in an underground anechoic chamber with an open/closing ceiling to maximally reduce the environmental effect such as RFI and ground radiation/*** appears that three of the four external calibrators proposed in this paper,including two indoor artificial transmitters and one outdoor celestial radiation(the Galactic polarization),fail to meet our *** motion of the Galactic diffuse emission turns out to be the most probable source as an external calibrator,for which we have discussed the observational strategy and the algorithm of extracting the EoR signal.

关键词： cosmology:observations dark ages reionization radio lines:general methods:observational

Group-scale asymmetric abundance structures in the NGC 533 group

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2012年第1期12卷 63-74页

作者： Jun-Hua Gu hai-guang xu Jing-Ying Wang Yu Wang Shao-Feng xu Zhen-Zhen Qin Li-Yi Gu Tao An Zhong-Li Zhang Min Lei Department of Physics Shanghai Jiao Tong University Shanghai 200240 China Shanghai Astronomical Observatory Shanghai 200030 China. Department of Physics School of Science The University of Tokyo 7-3-1 Hongo Bunkyo-kuTokyo 113-0033 Japan Max-Planck-Institute of Astrophysics Karl-Schwarzschild-Str. 1 Postfach 1317 85741Garching Munich Germany School of Mechanical Engineering Shanghai Jiao Tong University Shanghai 200240 China

By performing a two dimensional spectral analysis on the galaxy group NGC 533 with high-quality Chandra data, we find that the metal abundance distribution in this group is anisotropic. In the area around 2.5′ from the center, we find two concentrations of high abundance structures, in which the abundances are significantly higher than their surrounding regions at the 90% confidence level. We find that the total iron mass in these two regions agrees with the iron mass synthesized in the central dominant galaxy in n 19＋0.08 Gyr. The double-sided configuration of the high abun- 0.03 dance structure, together with the point-like radio emission in the center suggests that the abundance structures could have been transported from the center to their present positions by active galactic nucleus （AGN） activity. We further calculate the energy required for transport, and find that it could have been supplied during an AGN period. However, considering that this group is reported to have experienced a recent merger, the possibility that this merger is responsible for the abundance structures still cannot be excluded.

关键词： galaxies: clusters: individual (NGC 533) -- galaxy: abundances -- in-tergalactic medium -- X-rays: galaxies: clusters

The environment of C-and S-shaped radio galaxies

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2019年第9期19卷 55-62页

作者： Yu-Xing Liu hai-guang xu Dong-Chao Zheng Wei-Tian Li Zheng-Hao Zhu Zhi-Xian Ma Xiao-Li Lian School of Physics and Astronomy Shanghai Jiao Tong UniversityShanghai200240China Tsung-Dao Lee Institute/IFSA Collaborative Innovation Center Shanghai Jiao Tong UniversityShanghai200240China Department of Electronic Engineering Shanghai Jiao Tong UniversityShanghai200240China

We study the environment of radio galaxies with different morphological types using the Proctor sample, which was built from the Faint Images of the Radio Sky at Twenty-Centimeters(FIRST) survey archive. Among the 15 radio galaxy types classified by Proctor, 199 C-shaped(i.e., wide-or narrow-angle tail) and 203 S-shaped(i.e., S-or Z-shaped) sources are selected in this work, which are located in the redshift range of 0.02 < z < 1, because these two subsamples are relatively larger than the other subsamples in the Proctor sample. By cross-matching these radio galaxies with the optical sources drawn from the Sloan Digital Sky Survey(SDSS) database and counting the SDSS sources with an r-band absolute magnitude brighter than –19 located within a 0.5 Mpc distance around each source(i.e., the richness), we find that the fraction of C-shaped sources with a richness above 10 is larger than that of S-shaped sources. We have also correlated the radio galaxies in our sample with the brightest cluster galaxies(BCGs) defined in the NASA/IPAC Extragalactic Database(NED), and infer that the C-shaped sources are more likely to be BCGs than the S-shaped sources. These results support the idea that C-shaped radio galaxies often reside in a richer environment than radio galaxies with other morphological types.

关键词： galaxies:statistics galaxies:structure methods:data analysis

Biases in hydrostatic mass profiles introduced by hot gas substructures:Chandra study of four galaxy clusters

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2010年第10期10卷 1005-1012页

作者： Li-Yi Gu Yu Wang Jun-Hua Gu Jing-Ying Wang Zhen-Zhen Qin Meng-Yu Yao Jian-Long Yang hai-guang xu Department of Physics Shanghai Jiao Tong University Shanghai 200240 China

By analyzing the azimuthal variations of total gravitating mass profiles in the central 300 h^-1 71 kpc regions of four galaxy clusters with Chandra data, we find that the azimuthally-averaged mass profiles may have been systematically underestimated by 16^＋9 -8% at lσ significance in the 50-100 h^-1 71 kpc regions, probably due to the prevailing existence of 2-D hot gas substructures in 100-300h^-1 71 kpc. The mass biases become negligible（-7＋11 _9＋ %） at 〉 150 h^-1 71 kpc. We confirm the results that the gas temperature maps can be used to probe the departure from hydrostatic equilibrium and help quantify the systematic biases in X-ray mass measurements in the central regions of clusters.

关键词： cosmology dark matter -- galaxies clusters general -- galaxies inter-galactic medium -- X-rays galaxies clusters