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Does the Amati Relation depend on the Luminosity of the GRB's Host Galaxy?
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作者 Jing Wang Jing-Song Deng Yu-Lei Qiu 《Chinese Journal of Astronomy and Astrophysics》 CSCD 2008年第3期255-261,共7页
In order to test the systematics of the Amati relation, 24 long-duration GRBs with available Eγ,iso and Ep are separated into two subgroups according to the B-band luminosity of their host galaxies. The Amati relatio... In order to test the systematics of the Amati relation, 24 long-duration GRBs with available Eγ,iso and Ep are separated into two subgroups according to the B-band luminosity of their host galaxies. The Amati relations in the two subgroups are found to be in agreement with each other within the uncertainties. Taking into account of the well established luminosity - metallicity relation of galaxies, no strong evolution of the Amati relation with the GRB's environmental metaUicity is implied in this study. 展开更多
关键词 GAMMA-RAYS bursts -- gamma-rays observations -- galaxies evolution
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Radio observations of the first three-months of Fermi AGN at 4.8 GHz
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作者 Nicola Marchili Thomas P.Krichbaum +1 位作者 Lars Fuhrmann Anton Zensus 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2012年第2期147-157,共11页
Using the Urumqi 25 m radio telescope, sources from the first three months of the Fermi-large area telescope detected active galactic nuclei (AGN) catalog with a declination of 〉 0° were observed in 2009 at 4.... Using the Urumqi 25 m radio telescope, sources from the first three months of the Fermi-large area telescope detected active galactic nuclei (AGN) catalog with a declination of 〉 0° were observed in 2009 at 4.8 GHz. The radio flux density ap- peared to correlate with the γ-ray intensity. Intra-day variability (IDV) observations were performed in March, April and May 2009 for 42 selected γ-ray bright blazars, and ~60% of them showed evidence of flux variability at 4.8 GHz during the IDV observations. The IDV detection rate was higher than that in previous flat-spectrum AGN samples. IDV appeared more often in the very long baseline interferometry-core dominant blazars, and the non-IDV blazars showed relatively "steeper" spectral in- dices than the IDV blazars. Pronounced inter-month variability was also found in two BL Lac objects: J0112+2244 and J0238+1636. 展开更多
关键词 galaxies: active - quasars: general - radio continuum: galaxies -gamma-rays: observations
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Spectroscopic and photometric observations of unidentified ultraviolet variable objects in the GUVV-2 Catalog
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作者 You Li Jing Wang +1 位作者 Jian-Yan Wei Xiang-Tao He 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2011年第7期833-842,共10页
An NUV-optical diagram composed from sources from the second Galaxy Evolution Explorer(GALEX) Ultraviolet Variability(GUVV-2) Catalog provides us with a method to tentatively classify the unknown GUVV-2 sources by... An NUV-optical diagram composed from sources from the second Galaxy Evolution Explorer(GALEX) Ultraviolet Variability(GUVV-2) Catalog provides us with a method to tentatively classify the unknown GUVV-2 sources by their NUV-optical magnitudes.For the purpose of testing the correctness and generality of the method,we carry out a program on the spectroscopic observations of the unidentified GUVV-2 sources.The spectroscopic identification of these 37 sources are 19 type-A to-F stars,10 type-G to-K stars and 7 M dwarf stars together with an AGN.We also present the light curves in the R-band for two RR Lyrae star candidates selected from the NUV-optical diagram,both of which undergo cyclic variations.Combining their light curves and colors,we classify them as RR Lyrae stars.To confirm the re-sults,we show a color-color diagram for the 37 newly identified spectroscopic objects compared with previously identified ones,which are consistent with our previous re-sults,indicating that the ultraviolet variable sources can initially be classified by their NUV/optical color-color diagram. 展开更多
关键词 stars:variables:general—galaxies:active—methods:observational—ultraviolet emission
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Testing X-ray measurements of galaxy cluster gas mass fraction using the cosmic distance-duality relation
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作者 Xin Wang Xiao-Lei Meng +1 位作者 Yong-Feng Huang Tong-Jie Zhang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2013年第9期1013-1024,共12页
We propose a consistency test for some recent X-ray gas mass fraction (fgas) measurements in galaxy clusters, using the cosmic distance-duality relation, Ttneory = DL(1 + Z)-2/DA, with luminosity distance (DL) ... We propose a consistency test for some recent X-ray gas mass fraction (fgas) measurements in galaxy clusters, using the cosmic distance-duality relation, Ttneory = DL(1 + Z)-2/DA, with luminosity distance (DL) data from the Union2 compilation of type Ia supernovae. We set Z/theory = 1, instead of assigning any red- shift parameterizations to it, and constrain the cosmological information preferred by fga8 data along with supernova observations. We adopt a new binning method in the reduction of the Union2 data, in order to minimize the statistical errors. Four data sets of X-ray gas mass fraction, which are reported by Allen et al. (two samples), LaRoque et al. and Ettori et al., are analyzed in detail in the context of two theoretical models of fgas. The results from the analysis of Alien et al.'s samples demonstrate the feasibility of our method. It is found that the preferred cosmology by LaRoque et al.'s sample is consistent with its reference cosmology within the 1σ confidence level. However, for Ettori et al.'s fgas sample, the inconsistency can reach more than a 3σ confidence level and this dataset shows special preference to an ΩA = 0 cosmology. 展开更多
关键词 X-rays: galaxies: clusters -- cosmology: distance scale -- galaxies: clus-ters: general -- cosmology: observations -- supernovae: general
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Statistical Cluster-QSO Weak Lensing in the Sloan Digital Sky Survey
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作者 Zhong-Lue Wen Yan-Bin Yang +2 位作者 Xu Zhou Qi-Rong Yuan Jun Ma 《Chinese Journal of Astronomy and Astrophysics》 CSCD 2006年第5期521-529,共9页
We investigate the cross-correlation between galaxy clusters and QSOs using Sloan Digital Sky Survey (SDSS) DR4 - 5000 deg^2 data. With photometric redshifts of galaxies, we select galaxy clusters based on the local... We investigate the cross-correlation between galaxy clusters and QSOs using Sloan Digital Sky Survey (SDSS) DR4 - 5000 deg^2 data. With photometric redshifts of galaxies, we select galaxy clusters based on the local projected densities of LRGs brighter than Mr′ = -22. The QSOs are from the main sample of SDSS QSO spectroscopic survey to i′ = 19. A significant positive correlation is found between the clusters and QSOs. Under the assumption that the signal is caused by gravitational lensing, we fit the signal with singular isothermal sphere (SIS) model and NFW profile halo model. The velocity dispersion σv = 766 km s^-1 is derived for the best-fit of SIS model. Best-fit for the NFW model requires the dark matter halo mass within 1.5 h^-1 Mpc to be 4.6 × 10^14 h^-1 M⊙. The mass parameter Ωcl of the cluster sample is deduced as 0.077 with the SIS model and 0.083 with the NFW model. Our results of Ωcl are smaller than those given by Croom & Shanks and by Myers et al. 展开更多
关键词 COSMOLOGY observations - galaxies clusters general - quasars general - gravitational lensing
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Properties of BL Lac Objects with Redshift ≤ 0.2 被引量:1
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作者 Ben-ZhongDai Guang-ZhongXie 《Chinese Journal of Astronomy and Astrophysics》 CSCD 北大核心 2002年第1期8-16,共9页
We present a large sample which includes 82 BL Lac objects with red- shifts below 0.2 from recent literature. We find strong correlations in both flux and luminosity between the radio (5 GHz) and optical bands (5500 A... We present a large sample which includes 82 BL Lac objects with red- shifts below 0.2 from recent literature. We find strong correlations in both flux and luminosity between the radio (5 GHz) and optical bands (5500 A). The correlations in other bands are very weak. Five TeV BL Lacs and two suspect sources are found to have similar properties as high- frequency- peaked BL Lacs (HBLs). Our results suggest that both the radio and optical emissions are from the same radiation mech- anism in the SSC model. The TeV BL Lac candidates should be HBLs or HBL-like objects with small redshifts. 展开更多
关键词 galaxies: active - BL Lacertae objects: general -gamma-ray: observations - radiation mechanisms: non-thermal
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Are Type Ia Supernovae Reliable Distance Indicators?
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作者 Lian-Zhong Lü Yi-Ping Qin Fu-Wen Zhang 《Chinese Journal of Astronomy and Astrophysics》 CSCD 2007年第5期649-656,共8页
Recent applications of type Ia supernovae (SNe Ia) in cosmology have successfully revealed the accelerating expansion of the universe. However, as distance indicators used in measuring the expansion history of the u... Recent applications of type Ia supernovae (SNe Ia) in cosmology have successfully revealed the accelerating expansion of the universe. However, as distance indicators used in measuring the expansion history of the universe and probing the nature of dark energy, these objects must pass more strict tests. We propose a K-S test to investigate if there exists any systematic bias when deriving the luminosity distances under the standard candle assumption. Two samples, one comprising 71 high-redshift SNe Ia and the other, 44 nearby ones, are used in our investigation. We find that it is likely there exists a bias in the adopted samples, which is probably caused by a systematic error, e.g. in the color parameter used in the luminosity calibration and a bias may be caused by the SN evolution or by varying properties of the dust surrounding the SNe Ia. 展开更多
关键词 COSMOLOGY observations -- distance scale -- galaxies distances and redshifts -- methods statistical -- supernovae general
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Low-ionization galaxies and evolution in a pilot survey up to z=1
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作者 Edmond Giraud Qiu-Sheng Gu +4 位作者 Jorge Melnick Hernan Quintana Fernando Selman Ignacio Toledo Paula Zelaya 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2011年第3期245-270,共26页
We present galactic spectroscopic data from a pencil beam of 10.75×7.5 centered on the X-ray cluster RXJ0054.0–2823 at z=0.29.We study the spectral evolution of galaxies from z=1 down to the cluster redshift in ... We present galactic spectroscopic data from a pencil beam of 10.75×7.5 centered on the X-ray cluster RXJ0054.0–2823 at z=0.29.We study the spectral evolution of galaxies from z=1 down to the cluster redshift in a magnitude-limited sample at R≤23,for which the statistical properties of the sample are well understood.We divide emission-line galaxies into star-forming galaxies,Low Ionization Nuclear Emission line Regions(LINERs) ,and Seyferts by using emission-line ratios of[OII],Hβ,and[OIII],and derive stellar fractions from population synthesis models. We focus our analysis on absorption and low-ionization galaxies.For absorption-line galaxies,we recover the well-known result that these galaxies have had no detectable evolution since z~0.6-0.7,but we also find that in the range z=0.65-1,at least 50% of the stars in bright absorption systems are younger than 2.5 Gyr.Faint absorption-line galaxies in the cluster at z=0.29 also had significant star formation during the previous 2-3 Gyr,but their brighter counterparts seem to be only composed of old stars.At z~0.8,our dynamically young cluster had a truncated red-sequence.This result seems to be consistent with a scenario where the final assembly of E/S0 took place at z1.In the volume-limited range 0.35≤z≤0.65,we find that 23% of the early-type galaxies have LINER-like spectra with Hβin absorption and have a significant component of A stars.The vast majority of LINERs in our sample have significant populations of young and intermediate-aged stars and are thus not related to AGNs,but to the population of‘retired galaxies’recently identified by Cid Fernandes et al.in the Sloan Digital Sky Survey(SDSS) .Early-type LINERs with various fractions of A stars and E+A galaxies appear to play an important role in the formation of the red sequence. 展开更多
关键词 cosmology:observations—galaxies:evolution—large scale structures —evolution—RX J0054.0–2823
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X-ray spectroscopy of clusters of galaxies
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作者 Naomi Ota 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2012年第8期973-994,共22页
Clusters of galaxies are the most massive objects in the Universe and precise knowledge of their mass structure is important to understand the history of structure formation and constrain still unknown types of dark c... Clusters of galaxies are the most massive objects in the Universe and precise knowledge of their mass structure is important to understand the history of structure formation and constrain still unknown types of dark contents of the Universe. X-ray spectroscopy of galaxy clusters provides rich information about the physical state of hot intracluster gas and the underlying potential structure. In this paper, starting from the basic description of clusters under equilibrium conditions, we review properties of clusters revealed primarily through X-ray observations considering their thermal and dynamical evolutions. The future prospects of cluster studies using upcoming X-ray missions are also mentioned. 展开更多
关键词 galaxies: clusters: general -- galaxies: intergalactic medium -- X-rays:galaxies: clusters -- cosmology: observations -- cosmology: dark matter
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