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Lobe-dominatedγ-Ray Emission of Compact Symmetric Objects

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Research in Astronomy and Astrophysics 2024年第2期24卷 196-205页

作者： Ying-Ying Gan Hai-Ming Zhang Xing Yang Ying Gu Jin Zhang School of Physics Beijing Institute of TechnologyBeijing 100081China School of Astronomy and Space Science Nanjing UniversityNanjing 210023China Guangxi Key Laboratory for Relativistic Astrophysics School of Physical Science and TechnologyGuangxi UniversityNanning 530004China

Theγ-ray emitting compact symmetric objects(CSOs)PKS 1718-649,NGC 3894,and TXS 0128+554 are lobedominated in the radio emission.In order to investigate theirγ-ray radiation properties,we analyze the~14yr Fermi/LAT observation data of the three CSOs.They all show the low luminosity(1041-1043 erg s-1)and no significant variability in theγ-ray band.Theirγ-ray average spectra can be well fitted by a power-law function.These properties ofγ-rays are clearly different from theγ-ray emitting CSOs CTD 135 and PKS 1413+135,for which theγ-rays are produced by a restarted aligned jet.In the L_(γ)-Γ_(γ)plane,the three CSOs are also located at the region occupied by radio galaxies(RGs)while CTD 135 and PKS 1413+135 display a similar feature to blazars.Together with a similar radio emission property toγ-ray emitting RGs Cen A and Fornax A,we speculate that theγ-rays of the three CSOs stem from their extended mini-lobes.The broadband spectral energy distributions of the three CSOs can be well explained by the two-zone leptonic model,where theirγ-rays are produced by the inverse Compton process of the relativistic electrons in extended regions.By extrapolating the observed Fermi/LAT spectra to the very high energy band,we find that TXS 0128+554 among the three CSOs may be detected by the Cherenkov Telescope Array in the future.

关键词： galaxies active-galaxies jets-radio continuum galaxies-gamma-rays galaxies

Central black hole mass determination for blazars

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Chinese Physics B 2008年第4期17卷 1526-1533页

作者：袁聿海樊军辉黄勇 Center for Experiment Guangzhou University Center for Astrophysics Guangzhou University

In this paper, we use a method to dctermine some basic parameters for the γ-ray loud blazars. The parameters include the central black mass （M）, the boosting factor （δ）, the propagation angle （Ф）, the distance along the axis to the site of the γ-ray production （d）. A sample including 32 γ-ray loud blazars with available variability time scales has been used to discuss the above properties. In this method, the γ-ray energy, the emission size and the property of the accretion disc determine the absorption effect. If we take the intrinsic γ-ray luminosity to be λ times the Eddington luminosity, i.e. Lγ^in =λLEdd, then we have the following results： the mass of the black hole is in the range of （0.59 - 67.99） ×10^7M⊙ （λ = 1.0） or （0.90 - 104.13） × 10^7M⊙ （λ = 0.1）; the boosting factor （5） in the range of 0.16 - 2.09（λ = 1.0） or 0.24 - 2.86 （λ = 0.1）; the angle （Ф） in the range of 9.53°- 73.85° （λ =1.0） or 7.36° - 68.89° （λ = 0.1）; and the distance （d/Rg） in the range of 22.39 - 609.36 （λ = 1.0） or 17.54 - 541.88 （λ = 0.1）.

关键词： galaxies active-galaxies BL Lacertae objects general-galaxies

Study of Central Intensity Ratio of Seyfert galaxies in Nearby Universe

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Research in Astronomy and Astrophysics 2023年第4期23卷 85-93页

作者： K.T.Vinod C.Baheeja S.Aswathy C.D.Ravikumar Department of Physics University of CalicutMalappuram-673635India Department of Physics Providence Women's CollegeCalicut-673009India

We use the recently discovered simple photometric parameter Central Intensity Ratio(CIR)determined for a sample of 57 nearby(z<0.02)Seyfert galaxies to explore the central features of galaxies and their possible conne... 详细信息

We use the recently discovered simple photometric parameter Central Intensity Ratio(CIR)determined for a sample of 57 nearby(zgalaxies to explore the central features of galaxies and their possible connection with galaxy evolution.The sample of galaxies shows strong anti-correlation between CIR and mass of their central supermassive black holes(SMBHs).The SMBH masses of ellipticals are systematically higher for a given CIR value than those for lenticulars and spirals in the sample.However,the correlation between CIR and central velocity dispersion is weak.CIR appears less influenced by the excess flux produced by the central engine in these galaxies,when compared to spectroscopic parameters like velocity dispersion and OⅣflux,and proves to be a fast and reliable tool for estimating central SMBH mass.

关键词： Galaxy evolution-galaxies active-galaxies photometry-(galaxies:)quasars supermassive black holes-galaxies Seyfert

Chandra archival study of (U)LIRGs with a double nucleus:binary AGNs?

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Research in Astronomy and Astrophysics 2010年第4期10卷 309-328页

作者： Jing-Bo Wang Yu Gao Purple Mountain Observatory Chinese Academy of SciencesNanjing 210008China Graduate University of Chinese Academy of Sciences Beijing 100049China

We present our initial results from a study of 14 （U）LIRGs with a doublenucleus （z 〈0.15） and an AGN signature in the Chandra archive.The goals of our study are to search for more possible cases of binary AGNs and to investigate the X-ray properties and energy sources of these energetic objects,a major effort devoted specifically to searching for binary AGNs from （U）LIRGs.Our studies suggest that Mrk 266 might be a new candidate in hosting binary AGNs supported by X-ray observations.Our analysis shows that most （U）LIRGs are essentially weak X-ray sources and are not dominated by AGNs,due to both the lack of Fe K line detections and weak emission in the hard X-ray band.We find evidence for thermal emission with temperature kT ～ 0.7keV in seven nuclear regions,and this component is possibly associated with the nuclear or circumnuclear starburst.The soft and hard X-ray to far-infrared ratios also suggest that most （U）LIRGs are not energetically dominated by AGNs.Therefore,this study only provides one additional candidate of binary AGNs.We cannot rule out the existence of low luminosity AGNs and thus binary AGNs in all of them,particularly,those highly obscured and spatially unresolved systems.Nine of 14 （U）LIRGs,including three previously known binary AGNs and a new candidate Mrk 266,clearly have obvious X-ray counterparts to their double optical/near-IR nuclei.whereas only two out of 14 have one obvious X-ray counterpart detected.Additionally,Arp 220 and Mrk 273 are not spatially resolved owing to their small nuclear separations （～ 1″）,and no

关键词： galaxies active-galaxies nuclei-infrared galaxies-X-ray galaxies-galaxies individuals(Mrk 266 NGC 7592,IRAS 14348-1447,IRAS 08572+3915,Ⅱ Zw 035)

Evidence of the Link between Broad Emission Line Regions and Accretion Disks in active Galactic Nuclei

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Chinese Journal of Astronomy and Astrophysics 2007年第1期7卷 63-70页

作者： Yun Xu Xin-Wu Cao Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030 Graduate School of Chinese Academy of Sciences Beijing 100049

There is observational evidence that broad-line regions （BLRs） exist in most active galactic nuclei （AGNs）, but their origin is still unclear. One scenario is that the BLRs originate from winds accelerated from the hot coronae of the disks, and the winds are suppressed when the black hole is accreting at low rates. This model predicts a relation between rh （m ~ /~f//~fEdd） and the FWHM of broad emission lines. We estimate the central black hole masses for a sample of bright AGNs by using their broad Hβ line-widths and optical luminosities. The dimensionless accretion rates rh = M/MEdd are derived from the optical continuum luminosities by using two different models： using an empirical relation between the bolometric luminosity Lbol and the optical luminosity （rh = Lbol/LEdd, a fixed radiative efficiency is adopted）; and calculating the optical spectra of accretion disks as a function of rh. We find a slgmficant correlation between the denved of and the observed line width of Hβ, FWHMα m^-0.aT, which almost overlaps the disk-corona model calculations, if the viscosity a α≈ 0.1 - 0.2 is adopted. Our results provide strong evidence for the physical link between the BLRs and accretion disks in AGNs.

关键词： accretion, accretion disks-galaxies active-galaxies theory-radiation mechanisms emission lines-black hole physics

Variability of Soft X-ray Spectral Shape in Blazars Observed by ROSAT

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Chinese Journal of Astronomy and Astrophysics 2002年第2期2卷 117-126页

作者： Lin-Peng Cheng Yong-Heng Zhao Jian-Yan Wei National Astronomical Observatories Chinese Academy of SciencesBeijing 100012

In previous paper we have shown that the soft X-ray spectra of two types of Seyfert 1 galaxies behave statistically differently with increasing intensity. In order to see how the spectrum of blazars changes, we made plots of Hardness Ratio 1 versus Count Rates (HR1-Cts) for 18 blazars observed by ROSAT/PSPC. According to our criteria, ten showed a positive HR1-Cts correlation, two a negative correlation, and the remaining six, no clear correlation. Thus, most blazars of our sample show a hardening spectrum during overall flux increase, though some vary randomly. By investigating the photon index of these objects and different radiation theories, we argue that relative dominance between the synchrotron and inverse Compton emission in the soft X-ray band can well account for the differing spectral behaviours and that the different spectral variations might represent a sequence of synchrotron peaked frequency.

关键词： galaxies active-galaxies X-ray-blazar spectrum

A Multiwavelength Study of the Jets in FR-I Radio galaxies:I.Data and Analysis

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Research in Astronomy and Astrophysics 2006年第1期 25-34页

作者： Da-Min Meng Hong-Yan Zhou Center for Astrophysics,and Department of Astronomy and Applied Physics,University of Science and Technology of China,Hefei 230026 Center for Astrophysics and Department of Astronomy and Applied Physics University of Science and Technology of China Hefei 230026

We compile a sample of 11 Fanaroff-Riley type I Radio galaxies(FR-I RGs)with multi-wavelength observations to address the dynamic behavior of jets in these objects.Optical images acquired by the Hubble Space Telescope(HST)are carefully analyzed.The method and reduction procedure are described in detail. Unresolved optical cores emerge after having properly removed starlight from the host galaxies in eight of the FR-I RGs,of which five are new identifications.Broad band spectral properties of these newly identified compact cores are compared with that previously found in FR-I RGs,as well as the low-energy-peaked BL Lac objects. The similarity between them argues for the same non-thermal synchrotron origin. Well-resolved optical jets with knotty morphologies are found in three FR-I RGs in our sample,namely 3C 15,3C 66B and B20755+37.The optical counterparts to the inner radio/X-ray jets are identified and a clear one-to-one correspondence between the optical,radio and X-ray knots is found.The structure and information on the optical jets are discussed.Physical parameters such as the knots position,flux and size are also presented.Detailed comparison between the multi-wavelength data and radiative and dynamic models of jet will be made in a forthcoming paper.

关键词： galaxies active-galaxies jets

Decomposing the host galaxy from high-z QSOs using principal component analysis

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Research in Astronomy and Astrophysics 2019年第10期19卷 17-26页

作者： Wei He Yi-Ping Wang National Astronomical Observatories Chinese Academy of Sciences Beijing 100101 China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing 100049 China

High resolution deep imaging from space and adaptive optics techniques with large ground-based facilities have enabled studies examining faint host galaxies of high redshift quasi-stellar objects (QSOs). However, the related image processing techniques, especially for a precise point-spread function (PSF) reconstruction and characterization of the host galaxy light profiles, have yet to be optimized. We present here the scientific performance of a principal component analysis (PCA) based PSF subtraction of the central bright point source of high redshift QSO images, as well as further characterization of the host galaxy profile by directly fitting a Sèrsic model to the residual image using the Markov Chain Monte Carlo (MCMC) algorithm. With a set of reference PSF star images which represent interleaving exposures between the QSO imaging, we can create an orthogonal basis of eigen-images and restore the PSF of QSO images by projecting the QSO images onto the basis. In this way, we can quantify the modes in which the PSF varies with time by a basis function that characterizes the temporal variations of the reference star as well as the QSO images. To verify the algorithm, we performed a simulation and applied this method to one of the high-z QSO targets from Mechtley et al. We demonstrate that the PCA-based PSF subtraction and further modeling of the galaxy’s light profile using MCMC fitting would sufficiently remove the effects from central dominating point sources, and improve characterization ability for the host galaxies of high-z QSOs to the background noise level which is much better than previous two-component fitting procedures.

关键词： quasars general-galaxies active-galaxies high-redshift-methods data analysis

Mach’s Principle of Inertia Is Supported by Recent Astronomical Evidence

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International Journal of Astronomy and Astrophysics 2015年第3期5卷 166-172页

作者： Morley B. Bell National Research Council of Canada Ottawa Canada

Inertial mass is detected on Earth only when matter is accelerated or decelerated. Recently evidence has been reported for a low-level velocity oscillation with a period of 39 ± 1 Mpc (127 ± 3 Myr) superimposed on the Hubble flow. Like the Hubble flow, this oscillation is assumed to be an expansion and contraction of space itself. If space is oscillating as it expands and the Hubble flow contains a superimposed velocity ripple, matter on Earth will experience alternating accelerations and decelerations relative to the rest of the matter in the Universe. The acceleration curve can be obtained from the velocity oscillation curve simply by taking the magnitude of the derivative of the velocity curve and the acceleration curve is found here to have a period of 63.5 ± 1.5 Myr. Evidence has also been claimed recently for a ubiquitous ~62 ± 3 Myr periodic fluctuation superimposed on general trends in the fossil biodiversity on Earth. The periods of the acceleration curve oscillation and fossil biodiversity fluctuations are thus identical within the errors. A second, weaker fluctuation is also detected in both the Hubble flow and fossil biodiversity trends. They too have identical periods of ~140 Myr. From this excellent agreement, it is argued here that it is the oscillation in the Hubble flow, through an inertia-like phenomenon involving all the matter in the universe that has produced the fluctuations in the fossil biodiversity on Earth. This may represent the first instance where observational evidence supporting Mach’s Principle of Inertia has been found.

关键词： galaxies active-galaxies Distances and Redshifts