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High resolution deep imaging of a bright radio quiet QSO at z～3

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Research in Astronomy and Astrophysics 2015年第5期15卷 673-686页

作者： Yi-Ping Wang Wei He Toru Yamada Ichi Tanaka Masanori Iye Tuo Ji Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Tohoku University Aramaki Aoba Sendai 980-8578 Japan Subaru telescope National Astronomical Obs. of Japan 650 North A’ohoku Place Hilo Hawaii 96720 USA National Astronomical Obs. of Japan 2-21-1 Osawa Mitaka Tokyo 181-8588 Japan Polar Research Institute of China

We have obtained deep J and Ks-band images centered on a bright radio quiet QSO UM 402 （Zem = 2.856） using the IRCS camera and adaptive optics systems that are part of the Subaru Telescope, as well as retrieved WFC3/F140W archive images of this object. A faint galaxy （ink = 23.32 ±0.05 in the Vega magnitude system） that lies ～2.4″north of the QSO sightline has been clearly resolved in all three deep high resolution datasets, and appears as an irregular galaxy with two close components in the Ks-band images （separation ～ 0.31″）. Given the small impact parameter （b = 19.6 kpc, at Zlls = 2.531）, as well as the red color of （J - Ks）vega ～1.6, it might be a candidate galaxy giving rise to the Lyman Limit system absorption at Zabs = 2.531 seen in the QSO spectrum. After carefully subtracting the point spread function from the QSO images, the host galaxy of this bright radio quiet QSO at z ～ 3 was marginally revealed. We placed a lower limit on the host component of mk～ 23.3 according to our analyses.

关键词： galaxies active -- galaxies high redshift -- quasars general -- instru- mentation adaptive optics

Quasar SDSS J142507.32+323137.4: dual AGNs?

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Research in Astronomy and Astrophysics 2011年第4期11卷 411-418页

作者： Zhi-Xin Peng Yan-Mei Chen Qiu-Sheng Gu Chen Hu Department of Astronomy Nanjing University Nanjing 210093 China Key Laboratory of Modem Astronomy and Astrophysics （Nanjing University） Ministry of Education Nanjing 210093 China Key Laboratory for Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China

We analyze the optical spectrum of type 1 QSO SDSS J1425＋3231. This object is interesting since its narrow emission lines, such as [O Ⅲ]λλ4959, 5007, are double-peaked, and the line structure can be modeled well by three Gaussian components： two components for the two peaks （we refer to the peaks at low/high redshift as ＂the blue/red component＂） and another one for the line wing which has the same line center as that of the blue component, but is- 3 times broader. The separation between the blue and red components is -500km s-1 with the blue component being -2 times broader than the red one. The Hβ emission can be separated into four components： two for the double-peaked narrow line and two for the broad line which comes from the broad line regions. The black hole mass estimated from the broad Hβ emission line using the typical reverberation mapping relation is 0.85 × 108 M⊙, which is consistent with that derived from parameters of [O Ⅲ]λ 5007 of the blue component. We suggest that this QSO might be a dual AGN system; the broad Hβ emission line is mainly contributed by the primary black hole （traced by the blue component） while the broad Hβ component of the secondary black hole （traced by the red component） is hard to be separated out considering a resolution of - 2 000 for SDSS spectra or it may be totally obscured by the dusty torus.

关键词： galaxie active -- galaxies individual (SDSS J142507.32+323137.4)-- quasars emission lines

A modified stratified model for the 3C 273 jet

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Chinese Journal of Astronomy and Astrophysics 2009年第5期9卷 520-528页

作者： Wen-Po Liu Zhi-Qiang Shen Key Laboratory for Research in galaxies and Cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030 China Graduate School of Chinese Academy of Sciences Beijing 100049 China

We present a modified stratified jet model to interpret the observed spectral energy distributions of knots in the 3C 273 jet. Based on the hypothesis of the single index of the particle energy spectrum at injection and identical emission processes among all the knots, the observed difference of spectral shape among different 3C 273 knots can be understood as a manifestation of the deviation of the equivalent Doppler factor of stratified emission regions in an individual knot from a characteristic one. The summed spectral energy distributions of all ten knots in the 3C 273 jet can be well fitted by two components; a low-energy component （radio to optical） dominated by synchrotron radiation and a high- energy component （UV, X-ray and γ-ray） dominated by inverse Compton scattering of the cosmic microwave background. This gives a consistent spectral index of α = 0.88 （Sv ∝ v^-α） and a characteristic Doppler factor of 7.4. Assuming the average of the summed spectrum as the characteristic spectrum of each knot in the 3C 273 jet, we further get a distribution of Doppler factors. We discuss the possible implications of these results for the physical properties in the 3C 273 jet. Future GeV observations with GLAST could separate the 7-ray emission of 3C 273 from the large scale jet and the small scale jet （i.e. the core） through measuring the GeV spectrum.

关键词： galaxies active -- galaxies individual (3C 273) -- galaxies jets -- radia- tion mechanisms non-thermal

Possible γ-ray emission of radio intermediate AGN Ⅲ Zw 2 and its implication on the evolution of jets in AGNs

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Research in Astronomy and Astrophysics 2010年第8期10卷 707-712页

作者： Liang Chen Jin-Ming Bai Jin Zhang Hong-Tao Liu National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650011 China Graduate University of Chinese Academy of Sciences Beijing 100049 China College of Physics and Electronic Engineering Guangxi Teachers Education University Nanning 530001 China

AGNs with hard γ-ray emission identified so far are radio-loud. Ⅲ Zw 2 is a radio intermediate AGN with a relativistic jet. We study its spectral energy distribution （SED） and find that the broad band emissions are dominated by the nonthermal emissions from the jet. We model its SED through a synchrotron ＋ inverse Compton （IC） model. The results show that the IC component of Ⅲ Zw 2 peaks at a few MeV, and the flux density drops rapidly at higher energy with photon index F 3.3 above 0.1 GeV. The predicted flux is slightly over the sensitivity of Fermi/LAT, but it was not included in the first Fermi/LAT AGN catalog. The reason for this may be： 1） that the IC peak is low and the spectrum is very steep above 0.1 GeV, 2） that Ⅲ Zw 2 is in the low state during the period of the Fermi/LAT operation. We also find that Ⅲ Zw 2 follows similar jet processes as those in γ-ray AGNs, e.g., the relation between jet power and radiation power, which is called the blazar sequence. We suggest that Ⅲ Zw 2 may be a young source at an earlier stage of jet activity.

关键词： galaxies active -- galaxies Seyfert- galaxies jets -- radiation mechanisms non-thermal

XMM-Newton observations of H_2O maser galaxy NGC 7479

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Research in Astronomy and Astrophysics 2010年第9期10卷 915-926页

作者： Jin Wang Jiang-Shui Zhang Jun-Hui Fan Center for Astrophysics Guangzhou University Guangzhou 510006 China

The XMM-Newton observations of H2O megamaser galaxy NGC 7479 are presented. Its smoothed X-ray image clearly shows spiral morphology, which matches well with its optical asymmetric spiral structure. One prominent source can be found at the tip of its northern spiral arm, which is much brighter than its nuclear X-ray source （about a 50% higher count rate）. For the nuclear source （a circular region with a radius of 20 ″）, the spectra show soft excess below 2 keV and a strong iron Kα emission line. The best fitting model includes a partially absorbed model for the hard continuum and one thermal plasma model for the soft scatter component. Both the high column density （NH - 6.88 × 10^23 cm^-2） and strong fluorescent iron line （with an equivalent width of - 1.5 keV） support the existence of one heavily obscured AGN. For the bright prominent source, its radial profile is consistent with that of a single point-like source. Its spectra are extracted from the circular region around its peak, with a radius of 20″ and 6″ respectively and both spectra show models for the ultra-luminous X-ray source no significant difference. Four alternative （ULXs） can reproduce the spectra well： an absorbed power law, thermal bremsstrahlung, multicolor blackbody disk plus another blackbody or power law. Further observations （e.g., the tremendous improvement in the spatial resolution of the Chandra X-ray observations） and studies are desirable for probing the nature of this prominent source. In addition, we also estimate the mass of its central engine to be 1.18 × 10^7 M⊙ and maser disk parameters： the disk radius of -0.7 pc and the dimensionless accretion rate （L2-10kev/LEdd） of 1.2 × 10^-4.

关键词： masers -- galaxies active -- galaxies nuclei --- galaxies individual (NGC 7479) -- X-rays galaxies

Strong optical and UV intermediate-width emission lines in the quasar SDSS J232444.80–094600.3:dust-free and intermediate-density gas at the skin of dusty torus?

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Research in Astronomy and Astrophysics 2016年第9期16卷 107-116页

作者： Zhen-Zhen Li Hong-Yan Zhou Lei Hao Shu-Fen Wang Tuo Ji Bo Liu Department of Astronomy University of Science and Technology of China Hefei 230026 China Polar Research Institute of China Shanghai 200136 China Key Laboratory for Research in galaxies and Cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030 China Key Laboratory for Research in galaxies and Cosmology University of Science and Technology of China Chinese Academy of Sciences Hefei 230026 China

Emission lines from the broad emission line region （BELR） and the narrow emission line region （NELR） of active galactic nuclei （AGNs） have been extensively studied. However, emission lines are rarely detected between these two regions. We present a detailed analysis of quasar SDSS J232444.80-094600.3 （SDSS J2324-0946）, which is remarkable for its strong intermediate-width emission lines （IELs） with FWHM ≈ 1800 km s^-1. The IEL component is present in different emission lines, including the permitted lines Lyαλ1216, CⅣ λ1549, semiforbidden line C Ⅲ] λ1909, and forbidden lines [OⅢ] ss4959, 5007. With the aid of photo-ionization models, we found that the IELs are produced by gas with a hydrogen density of nH - 10^6.2 -- 10^6.3 cm^-3, a distance from the central ionizing source of R - 35 - 50 pc, a covering factor of - 6%, and a dust-to-gas ratio of ≤ 4% that of the SMC. We suggest that the strong IELs of this quasar are produced by nearly dust-free and intermediate-density gas located at the skin of the dusty torus. Such strong IELs, which serve as a useful diagnostic, can provide an avenue to study the properties of gas between the BELR and the NELR.

关键词： galaxies active -- galaxies nuclei -- quasars emission lines -- individual (SDSSJ2324-0946)

BL Lacertae objects and the extragalactic γ-ray background

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Research in Astronomy and Astrophysics 2011年第8期11卷 879-887页

作者： Fan Li Xin-Wu Cao Key Laboratory for Research in galaxies and Cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030 China Graduate University of Chinese Academy of Sciences Beijing 100049 China

A tight correlation between γ-ray and radio emission is found for a sample of BL Lacertae （BL Lac） objects detected by the Fermi Gamma-ray Space Telescope （Fermi） and the Energetic Gamma-Ray Experiment Telescope （EGRET）. The γ-ray emission of BL Lac objects exhibits strong variability, and the detection rate of γ-ray BL Lac objects is low, which may be related to the γ-ray duty cycle of BL Lac objects. We estimate the γ-ray duty cycle, δγ ≌ 0.11, for BL Lac objects detected by EGRET and Fermi. Using the empirical relation of γ-ray emission with radio emission and the estimated γ-ray duty cycle δγ, we derive the γ-ray luminosity function （LF） of BL Lac objects from their radio LE Our derived γ-ray LF of BL Lac objects can almost reproduce that calculated with the recently released Fermi bright active galactic nuclei （AGN） sample. Comparison of the derived LF of the γ-ray BL Lac objects in this work with that derived by Abdo et al. （2009a） requires the γ-ray duty cycle of BL Lac objects to be almost luminosity-independent. We find that - 45% of the extragalactic diffuse γ-ray background （EGRB） is contributed by BL Lac objects. Combining the estimate of the quasar contribution to the EGRB in the previous work, we find that 77% of the EGRB is contributed by BL Lac objects and radio quasars.

关键词： galaxies active -- galaxies BL Lacertae objects general -- cosmology diffuse radiation -- gamma rays theory

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

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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

Gamma-ray luminosity function of gamma-ray bright AGNs

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Chinese Journal of Astronomy and Astrophysics 2009年第1期9卷 85-94页

作者： Debbijoy Bhattacharya P.Sreekumar R.Mukherjee Department of Physics Indian Institute of Science Space Astronomy & Instrumentation Division ISRO Satellite Centre Barnard College Columbia University

Detection of γ-ray emissions from a class of active galactic nuclei （viz blazars）, has been one of the important findings from the Compton Gamma-Ray Observatory （CGRO）. However, their γ-ray luminosity function has not been well determined. Few attempts have been made in earlier works, where BL Lacs and Flat Spectrum Radio Quasars （FSRQs） have been considered as a single source class. In this paper, we investigated the evolution and γ-ray luminosity function of FSRQs and BL Lacs separately. Our investigation indicates no evolution for BL Lacs, however FSRQs show significant evolution. Pure luminosity evolution is assumed for FSRQs and exponential and power law evolution models are examined. Due to the small number of sources, the low luminosity end index of the luminosity function for FSRQs is constrained with an upper limit. BL Lac luminosity function shows no signature of break. As a consistency check, the model source distributions derived from these luminosity functions show no significant departure from the observed source distributions.

关键词： galaxies active -- galaxies evolution -- galaxies luminosity function -- gamma-rays observations