共查询到20条相似文献，搜索用时 15 毫秒
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Wei-Hao Bian Quan-Ling Cui Li-Hua Chao Department of Physics Institute of Theoretical Physics Nanjing Normal University Nanjing Key Laboratory for Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2006,6(3):281-286
We used multi-component profiles to model the Hβ and [OⅢ]λλ4959,5007 lines of SDSS J143030.22-001115.1, a narrow-line Seyfert 1 galaxy (NLS1) in a sample of 150 NLS1 candidates selected from the Sloan Digital Sky Survey (SDSS), Early Data Release (EDR). After subtracting the Hβ contribution from narrow line regions (NLRs), we found that its full width half maximum (FWHM) of broad Hβ line is nearly 2900km s~(-1) , significantly larger than the customarily adopted criterion of 2000 km s~(-1) . With its weak Fe Ⅱ multiples, we believe that SDSS J143030.22-001115.1 should not be classified as a genuine NLS1. When we calculate the virial black hole masses of NLS1s, we should use the Hβ linewidth after subtracting the NLR component. 相似文献
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Wei-Hao Bian Yong-Heng Zhao National Astronomical Observatories Chinese Academy of Sciences Beijing Department of Physics Nanjing Normal University Nanjing 《中国天文和天体物理学报》2003,3(2):119-124
We present estimated ratios of the central black hole mass to the bulge mass (Mbh/Mbulge) for 15 Narrow Line Seyfert 1 galaxies (NLS1s). It is found that NLS1s apparently have lower mass ratios: the average mass ratio is about 1 × 10-4 with a spread of 2, which is one order of magnitude lower than for Broad Line AGNs and quiescent galaxies. This lower value, as compared to that established essentially for all other types of galaxies, can be accounted for by an underestimation of the black hole masses and an overestimation of the bulge masses in the NLS1s. 相似文献
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A. K. Turner A. C. Fabian S. Vaughan J. C. Lee 《Monthly notices of the Royal Astronomical Society》2003,346(3):833-840
We present the analysis and first results from the Reflection Grating Spectrometer (RGS) during the 320-ks XMM–Newton observation of the Seyfert 1 galaxy MCG–6-30-15. The spectrum is marked by a sharp drop in flux at 0.7 keV which has been interpreted by Branduardi-Raymont et al. using RGS spectra from an earlier and shorter observation as the blue wing of a strong relativistic O viii emission line and by Lee et al. using a Chandra spectrum as due to a dusty warm absorber. We find that the drop is well explained by the Fe i L2,3 absorption edges and obtain reasonable fits over the 0.32–1.7 keV band using a multizone, dusty warm absorber model constructed using the photoionization code cloudy . Some residuals remain which could be due to emission from a relativistic disc, but at a much weaker level than from any simple model relying on relativistic emission lines alone. A model based on such emission lines can be made to fit if sufficient (warm) absorption is added, although the line strengths exceed those expected. In order to distinguish further whether the spectral shape is dominated by absorption or emission, we examined the difference spectrum between the highest and lowest flux states of the source. The EPIC pn data indicate that this is a power law in the 3–10 keV band which, if extrapolated to lower energies, reveals the absorption function acting on the intrinsic spectrum, provided that any emission lines do not scale exactly with the continuum. We find that this function matches our dusty warm absorber model well if the power law steepens below 2 keV. The soft X-ray spectrum is therefore dominated by absorption structures, with the equivalent width of any individual emission lines in the residuals being below approximately 30 eV. 相似文献
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R. Morales A. C. Fabian C. S. Reynolds 《Monthly notices of the Royal Astronomical Society》2000,315(1):149-154
The variable warm absorber seen with ASCA in the X-ray spectrum of MCG–6-30-15 shows complex time behaviour in which the optical depth of O viii anticorrelates with the flux whereas that of O vii is unchanging. The explanation in terms of a two-zone absorber has since been challenged by BeppoSAX observations. These present a more complicated behaviour for the O viii edge. We demonstrate here that the presence of a third, intermediate, zone can explain all the observations. In practice, warm absorbers are likely to be extended, multi-zone regions of which only part causes directly observable absorption edges at any given time. 相似文献
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J. Larsson A. C. Fabian G. Miniutti R. R. Ross 《Monthly notices of the Royal Astronomical Society》2007,376(1):348-352
We present a study of the spectral variability of the Seyfert I galaxy MCG–6-30-15 based on the two long XMM–Newton observations from 2000 and 2001. The X–ray spectrum and variability properties of the 2001 data have previously been well described with a two-component model consisting of a variable power-law and a much less variable reflection component, containing a broad relativistic iron line from the accretion disc around a rapidly rotating Kerr black hole. The lack of variability of the reflection component has been interpreted as an effect of strong gravitational light bending very close to the central black hole. Using an improved reflection model, we fit the two-component model to time-resolved spectra of both observations. Assuming that the photon index of the power law is constant, we reconfirm the old result and show that this does not depend on the time-scale of the analysis. 相似文献
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K. Iwasawa A. C. Fabian A. J. Young H. Inoue C. Matsumoto 《Monthly notices of the Royal Astronomical Society》1999,306(1):L19-L24
We report results on the broad iron emission line of the Seyfert galaxy MCG–6-30-15, obtained from the second long ASCA observation in 1997. The time-averaged profile of the broad line is very similar to that seen with ASCA in 1994, so confirming the detailed model fit then obtained. A bright flare is seen in the light curve, during which the continuum was soft. At that time the emission line peaks around 5 keV and most of its emission is shifted below 6 keV with no component detected at 6.4 keV ( This can be interpreted as the result of an extraordinarily large gravitational redshift owing to a dominant flare occurring very close to the black hole at a radius of ≲5 . 相似文献
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D. C. Shih K. Iwasawa A. C. Fabian 《Monthly notices of the Royal Astronomical Society》2002,333(3):687-696
We report on an analysis in the 3–10 keV X-ray band of the long 1999 ASCA observation of MCG–6-30-15. The time-averaged broad iron K line is well described by disc emission near a Schwarzschild black hole, confirming the results of earlier analyses on the ASCA 1994 and 1997 data. The time-resolved iron-line profile is remarkably stable over a factor of 3 change in source flux, and the line and continuum fluxes are uncorrelated. Detailed fits to the variable iron-line profile suggest that the active region (parametrized by the best-fitting inner and outer radii of the accretion disc) responsible for iron-line emission actually narrows with increasing flux to a region around 4–5 r g . In contrast with the iron line, the power-law continuum exhibits significant variability during the 1999 observation. Time-resolved spectral analysis reveals a new feature in the well-known photon index (Γ) versus flux correlation: Γ appears to approach a limiting value of Γ∼2.1 at high flux. Two models are proposed to explain both the new feature in the Γ versus flux correlation and the uncorrelated iron-line flux: a phenomenological two power-law model, and the recently proposed 'thundercloud' model of Merloni & Fabian . Both models are capable of reproducing the data well, but because they are poorly constrained by the observed Γ versus flux relation, they cannot at present be tested meaningfully by the data. The various implications and the physical interpretation of these models are discussed. 相似文献
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We report the result of simultaneous multi-wavelength observations of the TeV blazar Mrk 421 during February - March 2003. We observed Mrk 421 using the Pachmarhi Array of Cerenkov Telescopes (PACT) of Tata Institute of Fundamental Research at Pachmarhi, India. Other simultaneous data were taken from the literature and public data archives. We have analyzed the high quality X-ray (2-20keV) observations from the NASA Rossi X-Ray Timing Explorer (RXTE). We obtained a possible correlated variability between X-ray and J band (1.25 μ) near infrared (NIR) wavelength. This is the first case of X-ray and NIR correlated variability in Mrk 421 or any high energy peaked (HBL) blazar. The correlated variability reported here indicates a similar origin for the NIR and X-ray emissions. The emission is not affected much by the environment of the surrounding medium of the central engine of Mrk 421. The observations are consistent with the shock-in-jet model for the emissions. 相似文献
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J. C. Lee A. C. Fabian C. S. Reynolds K. Iwasawa & W. N. Brandt 《Monthly notices of the Royal Astronomical Society》1998,300(2):583-588
We report on a 50-ks observation of the bright Seyfert 1 galaxy MCG–6-30-15 with the Rossi X-ray Timing Explorer . The data clearly show the broad fluorescent iron line (equivalent width ∼ 250 eV) and the Compton reflection continuum at higher energies. A comparison of the iron line and the reflection continuum has enabled us to constrain the reflective fraction and the elemental abundances in the accretion disc. Temporal studies provide evidence that spectral variability is a result of changes in both the amount of reflection seen and the properties of the primary X-ray source itself. 相似文献
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Shao-Guang Luo Xue-Bing Wu Department of Astronomy Peking University Beijing Shenzhen Graduate School Peking University Shenzhen 《中国天文和天体物理学报》2005,5(5):448-456
By checking DSS optical images and NVSS radio images, 782 Markarian galaxies were identified to be NVSS radio sources. A comparison of the radio luminosity at 1.4 GHz and the far-infrared (FIR) luminosity for 468 "normal" galaxies shows a tight correlation. Most of the Seyfert galaxies and quasars follow the radio-FIR relation deduced from the "normal" galaxy sample, but with a somewhat larger scatter. A total 167 Markarian galaxies, comprising 100 "normal" galaxies, 66 Seyfert galaxies and one quasar, have either excess radio emission or much lower FIR spectral index α(25μm,60μm). These galaxies may be classified as "AGN-powered". For "normal" galaxies, the average q value (defined as the log ratio between FIR and radio luminosities) is 2.3. There seems a trend for q to slightly decrease with increasing radio luminosity. This may imply that the ongoing active star formation in galaxies with higher radio luminosities is more efficient in heating the cosmic-ray electrons. 相似文献
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We study the growth of black holes and stellar population in spheroids at high redshift using several (sub)mm-loud QSO samples. Applying the same criteria established in an earlier work, we find that, similar to IR QSOs at low redshift, the far-infrared emission of these (sub)mm-loud QSOs mainly originates from dust heated by starbursts. By combining low-z IR QSOs and high-z (sub)mm-loud QSOs, we find a trend that the star formation rate (M) increases with the accretion rate (Macc). We compare the values of M/Macc for submm emitting galaxies (SMGs), far-infrared ultraluminous/hyperluminous QSOs and typical QSOs, and construct a likely evolution scenario for these objects. The (sub)mm-loud QSO transition phase has both high Macc and M and hence is important for establishing the correlation between the masses of black holes and spheroids. 相似文献
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Xiao-Qing Wen Hong Wu Chen Cao Xiao-Yang Xia Department of Physics Tianjin Normal University Tianjin National Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2007,7(2):187-198
We made model fitting to the mid-to-far infrared spectral energy distributions (SEDs) for different categories of galaxies in the main extragalactic field of the Spitzer First Look Survey with the aid of spectroscopic information from the Sloan Digital Sky Survey. We find that the mid-to-far infrared SEDs of HII galaxies, mixture type galaxies and LINERs can be well fitted by the one-parameter (α) dust model of Dale et al. plus the 13 Gyr dust-free elliptical galaxy model. The statistics of α values indicates that all these galaxies tend to be quiescent, although the HII galaxies are relatively more active than the LINERs. The mid- infrared SEDs of absorption galaxies are well fitted simply by the 13 Gyr dust-free elliptical galaxy template, and the near-to-mid infrared SEDs of QSOs can be represented by AGN NGC 5506. 相似文献
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We compare the ionized gas velocity dispersion σgas with the stellar velocity dis-persion σ* in star-forming galaxies, composite galaxies, Low Ionization Nuclear Emission-line Regions (LINERs) and Seyfert 2s, compiled from a cross-identification of Sloan Digital Sky Survey Fourth Data Release (SDSS DR4) and Point Source Catalogue Redshift Survey (PSCz). We measure σgas from the FWHMs of emission lines (Hα, [NII]λλ6548, 6583 and [SII] λλ6716, 6731). A significant correlation between the gas and stellar velocity dispersion exists, despite substantial scatter. The mean value of the gas to stellar velocity dispersion ratio is close to unity. This suggests that gas velocity dispersion can substitute for the stellar veloc-ity dispersion as a tracer of the gravitational potential well for all the four types of galaxies,but the involved uncertainties are different from type to type. We also studied σgas/σ* as a function of the redshift and the axial ratio to test the effects of aperture and galaxy inclina-tion, and found that both effects are weak. Finally we checked the trend of σgas/σ* with the infrared luminosity and found no significant correlation. 相似文献
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Zhi-Jian Luo Cheng-Gang Shu 《中国天文和天体物理学报》2007,7(4):590-594
According to the new preheating mechanism of galaxy formation suggested by Mo et al., we construct a simple model of formation of disk galaxies within the current paradigm of galaxy formation. It incorporates preheating, gas cooling, bulge formation and star for-mation. The predicted stellar and HI mass functions of galaxies are discussed and compared with the observations. It is found that our model can roughly match both the observed galaxy luminosity function and the observed HI-mass function. 相似文献