16103411
Partially obscured quasars in the Sloan Digital Sky Survey Early Data Release
We have compiled a sample of 21 low redshift (z . 0.3), luminous active galactic nuclei (AGN) with large Balmer decrements (Hα/Hβ > 7) using the galaxy and QSO catalogs of the Sloan Digital Sky Survey Early Data Release. Using this sample we attempt to determine the fraction of quasars with large internal absorption. We find that these AGN have Strong [O III] λ5007 and broad Hα emission, and that starlight dominates the spectra in the blue band, suggesting that these objects are heavily reddened. Their narrow emission line ratios are similar to those of Seyfert 2 galaxies, yet the average [O III] λ5007 emission is ∼10 times more luminous. Applying the empirical relation between the optical continuum and the Balmer line luminosity for blue quasars, we find that the intrinsic luminosities of these 21 objects are in the range for quasars. We propose that they are obscured, intermediate type quasars analogous to type 1.8 and 1.9 Seyfert galaxies. The ratio of these optically selected, intermediate type quasars to type 1 quasars are found to be around 1, similar to that for local Seyfert galaxies. Preliminary study indicates that most of these quasars are hosted in early type galaxies. Subject headings: galaxies: active — quasars: general — galaxies: nuclei
119115722
CHANDRA HIGH-ENERGY GRATING OBSERVATIONS OF THE Fe Kα LINE CORE IN TYPE II SEYFERT GALAXIES: A COMPARISON WITH TYPE I NUCLEI
We present a study of the core of the Fe K{alpha} emission line at {approx}6.4 keV in a sample of type II Seyfert galaxies observed by the Chandra high-energy grating. The sample consists of 29 observations of 10 unique sources. We present measurements of the Fe K{alpha} line parameters with the highest spectral resolution currently available. In particular, we derive the most robust intrinsic line widths for some of the sources in the sample to date. We obtained a weighted mean full width at half-maximum (FWHM) of 2000 {+-} 160 km s{sup -1} for 8 out of 10 sources (the remaining sources had insufficient signal to noise). From a comparison with the optical emission-line widths obtained from spectropolarimetric observations, we found that the location of Fe K{alpha} line-emitting material is a factor of {approx}0.7-11 times the size of the optical broad-line region. Furthermore, compared to 13 type I active galactic nuclei (AGNs) for which the best Fe K{alpha} line FWHM constraints were obtained, we found no difference in the FWHM distribution or the mean FWHM, and this conclusion is independent of the central black hole mass. This result suggests that the bulk of the Fe K{alpha} line emission may originatemore » from a universal region at the same radius with respect to the gravitational radius, {approx}3 x 10{sup 4} r{sub g} on average. By examining the correlation between the Fe K{alpha} luminosity and the [O IV] line luminosity, we found a marginal difference in the Fe K{alpha} line flux between type I and type II AGNs, but the spread in the ratio of L{sub Fe} to L{sub [OIV]} is about two orders of magnitude. Our results confirm the theoretical expectation that the Fe K{alpha} emission-line luminosity cannot trivially be used as a proxy of the intrinsic AGN luminosity, unless a detailed comparison of the data with proper models is applied.« less
14125159
On the fraction of X-ray obscured quasars
Various studies have claimed that the fraction of obscured AGN drops with luminosity, but contrary results are also reported. We present our recent studies on the fraction of X-ray obscured quasars in Chandra Deep Fields and in the local universe showing that most quasars in CDFs (at redshift of 1 ~ 4) are obscured and a consistent pattern in the local universe.
18198918
Two extreme double-peaked line emitters in the sloan digital sky survey
Double-peaked Balmer lines have been observed in about 150 active galactic nuclei and were interpreted preferentially as emission from relativistic accretion disks. We report the discovery of extreme double-peaked lines in SDSS J0942+0900 and SDSS J1417+6141. The FWHM of the Hα line, 40,600 km s-1, in the first object is almost twice as large as the broadest previously known. By comparing the line profile with accretion disk models, we find that most of the line flux is emitted from a narrow annulus around 100rg in SDSS J0942+0900, and from a disk with radii between 100rg and 400rg in SDSS J1417+6141. This is the first time that an accretion disk at radii below 100rg has been directly probed through optical emission lines. A certain asymmetry in the disk is required for both objects. Another, much weaker, broad Hα component (Wλ ~ 20 A and FWHM ~ 4000 km s-1) is also detected in both objects. Both objects show weak radio emission and strong high-ionization narrow lines.
15551027
WHAT CONTROLS THE Fe II STRENGTH IN ACTIVE GALACTIC NUCLEI
We used a large, homogeneous sample of 4178 z <= 0.8 Seyfert 1 galaxies and QSOs selected from the Sloan Digital Sky Survey to investigate the strength of Fe II emission and its correlation with other emission lines and physical parameters of active galactic nuclei. We find that the strongest correlations of almost all the emission-line intensity ratios and equivalent widths (EWs) are with the Eddington ratio (L/L-Edd), rather than with the continuum luminosity at 5100 angstrom (L-5100) or black hole mass (M-BH); the only exception is the EW of ultraviolet Fe II emission, which does not correlate at all with broad-line width, L-5100, M-BH, or L/L-Edd. By contrast, the intensity ratios of both the ultraviolet and optical Fe II emission to MgII lambda 2800 correlate quite strongly with L/L-Edd. Interestingly, among all the emission lines in the near-UV and optical studied in this paper (including MgII lambda 2800, H beta, and [O III]lambda 5007), the EW of narrow optical Fe II emission has the strongest correlation with L/L-Edd. We hypothesize that the variation of the emission-line strength in active galaxies is regulated by L/L-Edd because it governs the global distribution of the hydrogen column density of the clouds gravitationally bound in the line-emitting region, as well as its overall gas supply. The systematic dependence on L/L-Edd must be corrected when using the Fe II/MgII intensity ratio as a measure of the Fe/Mg abundance ratio to study the history of chemical evolution in QSO environments.
11113279
Dynamical electroweak breaking and latticized extra dimensions
Using gauge invariant effective Lagrangians in 1+3 dimensions describing the Standard Model in 1+4 dimensions, we explore dynamical electroweak symmetry breaking. The Top Quark Seesaw model arises naturally, as well as the full CKM structure. We include a discussion of effects of warping, and indicate how other dynamical schemes may also be realized.
119100218
Confirming the 115.5-day periodicity in the X-ray light curve of ULX NGC 5408 X-1
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 Z-transform 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 > 3.8 sigma). 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-circle dot for the central black hole, implying there is an intermediate-mass black hole in NGC 5408 X-1.
119231582
Measurement of the D ± production asymmetry in 7 TeV pp collisions
Heavy quark production in 7 TeV centre-of-mass energy pp collisions at the LHC is not necessarily flavour symmetric. The production asymmetry, A(P), between D-s(+) and D-s(-) mesons is studied using the phi pi(+/-) decay mode in a data sample of 1.0 fb(-1) collected with the LHCb detector. The difference between pi(+) and pi(-) detection efficiencies is determined using the ratios of fully reconstructed to partially reconstructed D*(+/-) decays. The overall production asymmetry in the D-s(+/-) rapidity region 2.0 to 4.5 with transverse momentum larger than 2 GeV is measured to be A(P) = (-0.33 +/- 0.22 +/- 0.10)%. This result can constrain models of heavy flavour production. (C) 2012 CERN. Published by Elsevier By. All rights reserved.