Systematic Errors in the Estimation of Black Hole Masses by Reverberation Mapping

The mass of the central black hole in many active galactic nuclei has been estimated on the basis of the assumption that the dynamics of the broad emission line gas are dominated by the gravity of the black hole. The most commonly-employed method is to estimate a characteristic size-scale $r_*$ from reverberation mapping experiments and combine it with a characteristic velocity $v_*$ taken from the line profiles; the inferred mass is then estimated by $r_* v_*^2/G$. We critically discuss the evidence supporting the assumption of gravitational dynamics and find that the arguments are still inconclusive. We then explore the range of possible systematic error if the assumption of gravitational dynamics is granted. Inclination relative to a flattened system may cause a systematic underestimate of the central mass by a factor $\sim (h/r)^2$, where $h/r$ is the aspect ratio of the flattening. The coupled effects of a broad radial emissivity distribution, an unknown angular radiation pattern of line emission, and sub-optimal sampling in the reverberation experiment can cause additional systematic errors as large as a factor of 3 or more in either direction.Comment: 19 pages, 4 figures, AASLaTeX, accepted by Ap

The End of the Lines for OX 169: No Binary Broad-Line Region

We show that unusual Balmer emission line profiles of the quasar OX 169, frequently described as either self-absorbed or double peaked, are actually neither. The effect is an illusion resulting from two coincidences. First, the forbidden lines are quite strong and broad. Consequently, the [N II]6583 line and the associated narrow-line component of H-alpha present the appearance of twin H-alpha peaks. Second, the redshift of 0.2110 brings H-beta into coincidence with Na I D at zero redshift, and ISM absorption in Na I D divides the H-beta emission line. In spectra obtained over the past decade, we see no substantial change in the character of the line profiles, and no indication of intrinsic double-peaked structure. The H-gamma, Mg II, and Ly-alpha emission lines are single peaked, and all of the emission-line redshifts are consistent once they are correctly attributed to their permitted and forbidden-line identifications. A systematic shift of up to 700 km/s between broad and narrow lines is seen, but such differences are common, and could be due to gravitational and transverse redshift in a low-inclination disk. Stockton & Farnham (1991) had called attention to an apparent tidal tail in the host galaxy of OX 169, and speculated that a recent merger had supplied the nucleus with a coalescing pair of black holes which was now revealing its existence in the form of two physically distinct broad-line regions. Although there is no longer any evidence for two broad emission-line regions in OX 169, binary black holes should form frequently in galaxy mergers, and it is still worthwhile to monitor the radial velocities of emission lines which could supply evidence of their existence in certain objects.Comment: 19 pages, 5 figures, accepted for publication in Ap.

Molecular footprint of drug-selective pressure in a human immunodeficiency virus transmission chain

Known human immunodeficiency virus (HIV) transmission histories are invaluable models for investigating the evolutionary and transmission dynamics of the virus and to assess the accuracy of phylogenetic reconstructions. Here we have characterized an HIV-1 transmission chain consisting of nine infected patients, almost all of whom were treated with antiviral drugs at later stages of infection. Partial pol and env gp41 regions of the HIV genome were directly sequenced from plasma viral RNA for at least one sample from each patient. Phylogenetic analyses in pol using likelihood methods inferred an evolutionary history not fully compatible with the known transmission history. This could be attributed to parallel evolution of drug resistance mutations resulting in the incorrect clustering of multidrug-resistant virus. On the other hand, a fully compatible phylogenetic tree was reconstructed from the env sequences. We were able to identify and quantify the molecular footprint of drug-selective pressure in pol using maximum likelihood inference under different codon substitution models. An increased fixation rate of mutations in the HIV population of the multidrug-resistant patient was demonstrated using molecular clock modeling. We show that molecular evolutionary analyses, guided by a known transmission history, can reveal the presence of confounding factors like natural selection and caution should be taken when accurate descriptions of HIV evolution are required.status: publishe

Transition into a low temperature superconducting phase of unconventional pinning in Sr_2RuO_4

We have found a sharp transition in the vortex creep rates at a temperature T^\ast=0.05 T_c in a single crystal of Sr_2RuO_4 (T_{c}=1.03 K) by means of magnetic relaxation measurements. For T<T^\ast, the initial creep rates drop to undetectable low levels. One explanation for this transition into a phase with such extremely low vortex creep is that the low-temperature phase of Sr_2RuO_4 breaks time reversal symmetry. In that case, degenerate domain walls separating discreetly degenerate states of a superconductor can act as very strong pinning centers.Comment: 3 pages, 2 figure

Propofol 1% versus propofol 2% in children undergoing minor ENT surgery

Background. The induction characteristics of propofol 1% and 2% were compared in children undergoing ENT surgery, in a prospective, randomized, double‐blind study. Methods. One hundred and eight children received propofol 1% (n=55) or 2% (n=53) for induction and maintenance of anaesthesia. For induction, propofol 4mgkg-1 was injected at a constant rate (1200mlh-1), supplemented with alfentanil. Intubating conditions without the use of a neuromuscular blocking agent were scored. Results. Pain on injection occurred in 9% and 21% of patients after propofol 1% and 2%, respectively (P=0.09). Loss of consciousness was more rapid with propofol 2% compared with propofol 1% (47s vs 54s; P=0.02). Spontaneous movements during induction occurred in 22% and 34% (P=0.18), and intubating conditions were satisfactory in 87% and 96% (P=0.19) of children receiving propofol 1% or 2%, respectively. There were no differences between the two groups in respect of haemodynamic changes or adverse events. Conclusions. For the end‐points tested, propofol 1% and propofol 2% are similar for induction of anaesthesia in children undergoing minor ENT surgery. Br J Anaesth 2003: 90: 375-

The Extended Water Footprint and illegal groundwater use in the Upper Guadiana Basin (Spain)

Tablas de Daimiel National Park is located in the Upper Guadiana Basin and represents one of the largest and most important wetlands in Europe. The long term ecological integrity of this wetland is inherently associated with the maintenance of a shallow groundwater table, namely the Western Mancha aquifer (WMA) or Aquifer 23. The intensive use of groundwater, mainly for irrigation, has led over the last decades to deep socio‐economic changes. Such intensive use has also lowered the water table of Aquifer 23, drastically reducing the flooded area of the wetland and threatening its ecological integrity. A number of plans and measures have been developed and implemented since the declaration of overexploitation of Aquifer 23 in the year 1987. The most recent one is the Special Plan for the Upper Guadiana (SPUG), approved in 2008. This Plan is the main measure to comply with achieving the objective of good quantitative and qualitative status required under the Water Framework Directive (2000). This paper offers a new type of integrated analysis which allows assessing under a common lens the physical, economic and social dimensions of groundwater use in the area. The first objective is to calculate the groundwater footprint of agricultural production in the Upper Guadiana basin and its evolution during 2000‐2008. For this purpose, we have applied the Extended Water Footprint (EWF) methodology ‐a novel approach based on the classical Water Footprint (WF) approach‐ that includes an assessment of the water productivity from an economic and social perspective. Compared to the classical WF, the EWF allows for a more complete overview of the sector, providing new insights for policy decisions (e.g. to define options and possibilities on water re‐allocation in order to achieve both better ecosystem conservation and social equity). The second objective is to use the EWF to compare the existing authorized and non‐authorized or illegal use of water. This allows us to discuss current initiatives by public authorities in relation to the existing frame of water right

Influence of s,p-d and s-p exchange couplings on exciton splitting in (Zn,Mn)O

This work presents results of near-band gap magnetooptical studies on (Zn,Mn)O epitaxial layers. We observe excitonic transitions in reflectivity and photoluminescence, that shift towards higher energies when the Mn concentration increases and split nonlinearly under the magnetic field. Excitonic shifts are determined by the s,p-d exchange coupling to magnetic ions, by the electron-hole s-p exchange, and the spin-orbit interactions. A quantitative description of the magnetoreflectivity findings indicates that the free excitons A and B are associated with the Gamma_7 and Gamma_9 valence bands, respectively, the order reversed as compared to wurtzite GaN. Furthermore, our results show that the magnitude of the giant exciton splittings, specific to dilute magnetic semiconductors, is unusual: the magnetoreflectivity data is described by an effective exchange energy N_0(beta-alpha)=+0.2+/-0.1 eV, what points to small and positive N_0 beta. It is shown that both the increase of the gap with x and the small positive value of the exchange energy N_0 beta corroborate recent theory describing the exchange splitting of the valence band in a non-perturbative way, suitable for the case of a strong p-d hybridization.Comment: 8 pages, 8 figure

Long-Term Profile Variability of Double Peaked Emission Lines in Active Galactic Nuclei

We present up to two decades of spectroscopic monitoring of the double-peaked broad Halpha emission lines of seven broad-line radio galaxies. These extremely broad, double-peaked lines are successfully modeled by emission from gas in the outer accretion disk, and their profiles vary on timescales of months to years. This variability is a valuable probe for understanding the structure and dynamics of the accretion disk. We characterize the long-term broad-line profile variability in detail, and compare the evolution of the line profiles with predictions from a few simple physical models for dynamical processes in the accretion disk. We find no evidence for persistent, periodic variability that would be indicative of a precessing elliptical disk, or a circular disk with a long-lived, single-armed spiral or warp. We do find transient, periodic variability on the orbital timescale, possibly resulting from shocks induced by tidal perturbations, and variability in the wings of the profile which suggests changes in the emissivity of the inner accretion flow. Dramatic but localized profile changes are observed during flares and high-states of broad-line flux. In 3C 332, these changes can be explained by a slow, smooth, secular change in disk illumination. In Arp 102B and 3C 390.3, however, a simple disk model cannot explain the asymmetric profile changes, suggesting a need for more sophisticated models. We also observe sharp, transient features that appear in the blue peak of the objects, which require a well-organized velocity field.Comment: 76 pages, 52 figures, 14 tables, Accepted for publication in ApJS, figures in Appendix are low resolutio