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We estimate black hole masses (M$_{\rm BH}$) for 14 gravitationally lensed quasars using the Balmer lines along with estimates based on MgII and CIV emission lines for four and two of them, respectively. We compare with results obtained for other lensed quasars. We use spectroscopic data from the Large Binocular Telescope (LBT), Magellan and the Very Large Telescope (VLT) to measure the FWHM of the broad emission lines. Combined with the bolometric luminosity measured from the spectra energy distribution, we estimate M$_{\rm BH}$ including uncertainties from microlensing and variability. We obtain MBH using the single-epoch method from the H$\alpha$ and/or H$\beta$ broad emission lines for 14 lensed quasars, including the first estimates for QJ0158-4325, HE0512-3329 and WFI2026-4536. The masses are typical of non-lensed quasars of similar luminosity, and the implied Eddington ratios are typical. We have increased the sample of lenses with estimates of MBH by 60%., Comment: 16 pages. Submitted to A&A

Virial black hole mass ($M_{BH}$) determination directly involves knowing the broad line region (BLR) clouds velocity distribution, their distance from the central supermassive black hole ($R_{BLR}$) and the virial factor ($f$). Understanding whether biases arise in $M_{BH}$ estimation with increasing obscuration is possible only by studying a large (N$>$100) statistical sample of obscuration unbiased (hard) X-ray selected active galactic nuclei (AGN) in the rest-frame near-infrared (0.8-2.5$\mu$m) since it penetrates deeper into the BLR than the optical. We present a detailed analysis of 65 local BAT-selected Seyfert galaxies observed with Magellan/FIRE. Adding these to the near-infrared BAT AGN spectroscopic survey (BASS) database, we study a total of 314 unique near-infrared spectra. While the FWHMs of H$\alpha$ and near-infrared broad lines (He\textsc{i}, Pa$\beta$, Pa$\alpha$) remain unbiased to either BLR extinction or X-ray obscuration, the H$\alpha$ broad line luminosity is suppressed when $N_H\gtrsim10^{21}$ cm$^{-2}$, systematically underestimating $M_{BH}$ by $0.23-0.46$ dex. Near-infrared line luminosities should be preferred to H$\alpha$ until $N_H<10^{22}$ cm$^{-2}$, while at higher obscuration a less biased $R_{BLR}$ proxy should be adopted. We estimate $f$ for Seyfert 1 and 2 using two obscuration-unbiased $M_{BH}$ measurements, i.e. the stellar velocity dispersion and a BH mass prescription based on near-infrared and X-ray, and find that the virial factors do not depend on redshift or obscuration, but for some broad lines show a mild anti-correlation with $M_{BH}$. Our results show the critical impact obscuration can have on BLR characterization and the importance of the near-infrared and X-rays for a less biased view of the BLR., Comment: 28 pages (excluding appendices), 14 figures, pre-proof version accepted for publication on ApJ (to appear on the BASS DR2 ApJ Special Issue)

The quadruple lensed system WGD2038-4008 was recently discovered with the help of new techniques and observations. Even though black hole mass has been estimated for lensed quasars, it has been calculated mostly for one broad emission line of one image, but the images could be affected by microlensing, affecting the results. We present black hole mass (MBH) estimations for images A and B using the three most prominent broad emission lines (H$\alpha$, H$\beta$ and MgII) obtained in one single-epoch spectra. This is the first time the mass is estimated in a lensed quasar in two images, allowing us to disentangle the effects of microlensing. We used the X-shooter instrument mounted in VLT, to observe this system taking advantage of its wide spectral range. Using the flux ratio between the continuum and the core of the emission lines we analyzed if microlensing was present in the continuum source. We obtained MBH using the single-epoch method with the H$\alpha$ and H$\beta$ emission lines from the monochromatic luminosity and the velocity width. The luminosity at 3000 \r{A} was obtained using the Spectral Energy Distribution (SED) of image A while the luminosity at 5100 \r{A} was estimated directly from the spectra. The average MBH between the images obtained was $\rm log_{10}$(M$_{BH}/M_{\odot}$) = 8.27 $\pm$ 1.05, 8.25 $\pm$ 0.32 and 8.59 $\pm$ 0.35 for MgII, H$\beta$ and H$\alpha$ respectively. We find Eddington ratios similar to those measured in the literature for unlensed low-luminosity quasars. Microlensing of -0.16 $\pm$ 0.06 mag. in the continuum was found but the induced error in the MBH is minor compared to the one associated to the macromodel magnification. We also obtained the accretion disk size using the MBH for the three emission lines, obtaining an average value of $\rm log_{10}(r_{s}/cm)$ = 15.3 +/- 0.63, which is in agreement with theoretical estimates.

In this research, the tax evasion percentage, as order parameter, of a system of individuals or agents inscribed in a $N = L \times L$ 2D square grid is computed. The influence of local environment over each agent is quantified both through competitive exchange integrals (ferromagnetic and antiferromagnetic bonds) and dangling bonds randomly distributed, which allows to identify the system with disordered ternary alloys of the type $\mathrm{A_\textit{p}B_\textit{x}C_\textit{q}}$ with a certain stoichiometry $(p,x,q)$ particular of each society. Our proposal is based on the so-called spin glass phase present in magnetic systems characterized by disorder, dilution and competitive interactions where magnetic frustration can take place, resembling the way as an individual or agent in a society is able to face a decision. In this sense, agents are identified as Ising spins, which can take two possible values ($\sigma = \pm 1$), in correspondence with a two-state system where agents can be tax compliant or not. Such an identification between social and physical variables, as well as parameters like an external applied magnetic field or temperature, are topic of discussion in this investigation. Thermalization of the observables is carried out by means of the heat bath algorithm. Other social variables, such as the audit period, and its effects over the percentage of evasion, are used to analyze the behavior of tax evasion in Colombia, however the model can be applied to any country.

Assuming a gravitational origin for the Fe III$\lambda\lambda$2039-2113 redshift and using microlensing based estimates of the size of the region emitting this feature, we obtain individual measurements of the virial factor, $f$, in 10 quasars. The average values for the Balmer lines, $\langle f_{H\beta}\rangle={\bf 0.43\pm 0.20}$ and $\langle f_{H\alpha}\rangle={\bf 0.50\pm 0.24}$, are in good agreement with the results of previous studies for objects with lines of comparable widths. In the case of Mg II, consistent results, $f_{Mg II} \sim {\bf 0.44}$, can be also obtained accepting a reasonable scaling for the size of the emitting region. The modeling of the cumulative histograms of individual measurements, $CDF(f)$, indicates a {relatively} high value for the ratio between isotropic and cylindrical motions, $a\sim {\bf 0.4}-0.7$. On the contrary, we find very large values of the virial factor associated to the Fe III$\lambda\lambda$2039-2113 blend, $f_{FeIII}=14.3\pm2.4$, which can be explained if this feature arises from a flattened nearly face-on structure, similar to the accretion disk., Comment: Accepted in ApJ

We study the generation of spin-squeezing in arrays of long-lived dipoles subject to collective emission, coherent drive, elastic interactions, and spontaneous emission. Counter-intuitively, it is found that the introduction of spontaneous emission leads to an enhancement of the achievable spin-squeezing, relative to that which emerges in the steady-state of the purely collective dynamics for the same model parameters. This behavior is connected to the dynamical self-tuning of the system through a dissipative phase transition that is present in the collective system alone. Our findings will be applicable to next-generation quantum sensors harnessing correlated quantum matter, including cavity-QED and trapped ion systems., Comment: 5+4 pages, 3+2 figures

We test the recently proposed (Mediavilla et al. 2018) black hole mass scaling relationship based on the redshift {with respect to the quasar's rest frame} of the Fe III$\lambda\lambda$2039-2113 line blend. To this end, we fit this feature in the spectra of a well suited sample of quasars, observed with X-shooter at the Very Large Telescope (VLT), whose masses have been independently estimated using the virial theorem. For the quasars of this sample we consistently confirm the redshift of the Fe III$\lambda\lambda$2039-2113 blend and find that it correlates with the squared widths of H$\beta$, H$\alpha$ and Mg II, which are commonly used as a measure of $M_{BH}/R$ to determine masses from the virial theorem. The average differences between virial and Fe III$\lambda\lambda$2039-2113 redshift based masses are 0.18$\pm 0.21$ dex, 0.18$\pm 0.22$ dex and 0.14$\pm 0.21$ dex, when the full widths at half maximum (FWHM) of the H$\beta$, H$\alpha$ and MgII lines are, respectively, used. The difference is reduced to 0.10$\pm 0.16$ dex when the standard deviation, $\sigma$, of {the} MgII line is used, instead. We also study the high S/N composite quasar spectra of the Baryon Oscillation Spectroscopic Survey (BOSS), finding that the Fe III$\lambda\lambda$2039-2113 redshifts and Mg II squared widths, $FWHM_{MgII}^2$, match very well the correlation found for the individual quasar spectra observed with X-shooter. This correlation is expected if the redshift is gravitational.

The recently released 105-month {\it Swift}-Burst Alert Telescope (BAT) all-sky hard X-ray survey catalog presents an opportunity to study astrophysical objects detected in the deepest look at the entire hard X-ray (14$-$195 keV) sky. Here we report the results of a multifrequency study of 146 blazars from this catalog, quadrupling the number compared to past studies, by utilizing recent data from the {\it Fermi}-Large Area Telescope (LAT), Swift-BAT, and archival measurements. In our $\gamma$-ray analysis of $\sim$10 years of the LAT data, 101 are found as $\gamma$-ray emitters, whereas, 45 remains LAT undetected. We model the broadband spectral energy distributions with a synchrotron-inverse Compton radiative model. On average, BAT detected sources host massive black holes ($M_{\rm bh}\sim10^9$ M$_{\odot}$) and luminous accretion disks ($L_{\rm d}\sim10^{46}$ erg s$^{-1}$). At high-redshifts ($z>2$), BAT blazars host more powerful jets with luminous accretion disks compared to those detected only with the {\it Fermi}-LAT. We find good agreement in the black hole masses derived from the single-epoch optical spectroscopic measurements and standard accretion disk modeling approaches. Other physical properties of BAT blazars are similar to those known for {\it Fermi}-LAT detected objects., Comment: 16 pages, 7 figures, 6 tables, to appear in the Astrophysical Journal. Full data tables and SED plots are included in the arXiv uploaded files

We investigate the effects of the competition between exchange ($J$) and dipolar ($D$) interactions on the magnetization reversal mechanisms of ferromagnetic nanotubes. Using first atomistic Monte Carlo (MC) simulations for a model with Heisenberg spins on a cylindrical surface, we compute hysteresis loops for a wide range of the $\gamma=D/J$ parameter, characterizing the reversal behavior in terms of the cylindrical magnetization components and the vorticity parameter along the tube length. For $\gamma$'s close to the value for which helical (H) states are stable at zero applied field, we show that the hysteresis loops can occur in four different classes that are combinations of two reversal modes with well-differentiated coercivities with probabilities that depend on the tube length and radius. This variety in the reversal modes is found to be linked to the metastability of the $H$ states during the reversal that induce different paths followed along the energy landscape as the field is changed. We further demonstrate that reversal by either of the two modes can be induced by tailoring the nanotube initial state so that vortices with equal or contrary chirality are formed at the ends, thus achieving low or high coercive fields at will without changing $\gamma$. Finally, the results of additional micromagnetic simulations performed on tubes with similar aspect ratio show that dual switching modes and its tailoring can also be observed in tubes with more microscopic dimensions., Comment: 10 pages, 12 figures. Supplementary information may be downloaded at: http://www.ffn.ub.es/oscar/Articles/

We present our statistical analysis of the connection between active galactic nuclei (AGN) variability and physical properties of the central supermassive black hole (SMBH). We constructed optical light curves using data from the QUEST-La Silla AGN variability survey. To model the variability, we used the structure function, among the excess variance and the amplitude from Damp Random Walk (DRW) modeling. For the measurement of SMBH physical properties, we used public spectra from the Sloan Digital Sky Survey (SDSS). Our analysis is based on an original sample of 2345 sources detected in both SDSS and QUEST-La Silla. For 1473 of these sources we could perform a proper measurement of the spectral and variability properties, and 1348 of these sources were classified as variable ($91.5\%$). We found that the amplitude of the variability ($A$) depends solely on the rest frame emission wavelength and the Eddington ratio, where $A$ anti-correlates with both $\lambda_{rest}$ and $L/L_{\text{Edd}}$. This suggests that AGN variability does not evolve over cosmic time, and its amplitude is inversely related to the accretion rate. We found that the logarithmic gradient of the variability ($\gamma$) does not correlate significantly with any SMBH physical parameter, since there is no statistically significant linear regression model with an absolute value of the slope higher than 0.1. Finally, we found that the general distribution of $\gamma$ measured for our sample differs from the distribution of $\gamma$ obtained for light curves simulated from a DRW process. For 20.6\% of the variable sources in our sample, a DRW model is not appropriate to describe the variability, since $\gamma$ differs considerably from the expected value of 0.5., Comment: 26 pages, 17 figures, 9 tables. Minor formatting changes. Accepted for publication in ApJ

We have investigated the equilibrium states of ferromagnetic single wall nanotubes by means of atomistic Monte Carlo simulations of a zig-zag lattice of Heisenberg spins on the surface of a cylinder. The main focus of our study is to determine how the competition between short-range exchange (J) and long-range dipolar (D) interactions influences the low temperature magnetic order of the nanotubes as well as the thermal-driven transitions involved. Apart from the uniform and vortex states occurring for dominant J or D, we find that helical states become stable for a range of intermediate values of g = D=J that depends on the radius and length of the nanotube. Introducing a vorticity order parameter to better characterize helical and vortex states, we find the pseudo-critical temperatures for the transitions between these states and we establish the magnetic phase diagrams of their stability regions as a function of the nanotube aspect ratio. Comparison of the energy of the states obtained by simulation with those of simpler theoretical structures that interpolate continuously between them, reveals a high degree of metastability of the helical structures that might be relevant for their reversal modes., Comment: 21 pages, 14 figures, SI avaliable from authors. Accepted in Scientific Reports 2018

In large optical survey at high redshifts ($z>2$), the CIV broad emission line is the most practical alternative to estimate the mass ($M_{\text{BH}}$) of active super-massive black holes (SMBHs). However, mass determinations obtained with this line are known to be highly uncertain. In this work we use the Sloan Digital Sky Survey Data Release 7 and 12 quasar catalogues to statistically test three alternative methods put forward in the literature to improve CIV-based $M_{\text{BH}}$ estimations. These methods are constructed from correlations between the ratio of the CIV line-width to the low ionization line-widths (H$\alpha$, H$\beta$ and MgII) and several other properties of rest-frame UV emission lines. Our analysis suggests that these correction methods are of limited applicability, mostly because all of them depend on correlations that are driven by the linewidth of the CIV profile itself and not by an interconnection between the linewidth of the CIV line with the linewidth of the low ionization lines. Our results show that optical CIV-based mass estimates at high redshift cannot be a proper replacement for estimates based on IR spectroscopy of low ionization lines like H$\alpha$, H$\beta$ and MgII, Comment: 14 pages, 5 figures, 7 tables, Accepted for publication in MNRAS

Supermassive black holes reside in the nuclei of most galaxies. Accurately determining their mass is key to understand how the population evolves over time and how the black holes relate to their host galaxies. Beyond the local universe, the mass is commonly estimated assuming virialized motion of gas in the close vicinity to the active black holes, traced through broad emission lines. However, this procedure has uncertainties associated with the unknown distribution of the gas clouds. Here we show that the comparison of black hole masses derived from the properties of the central accretion disc with the virial mass estimate provides a correcting factor, for the virial mass estimations, that is inversely proportional to the observed width of the broad emission lines. Our results suggest that line-of-sight inclination of gas in a planar distribution can account for this effect. However, radiation pressure effects on the distribution of gas can also reproduce our findings. Regardless of the physical origin, our findings contribute to mitigate the uncertainties in current black hole mass estimations and, in turn, will help to further understand the evolution of distant supermassive black holes and their host galaxies., Comment: 17 pages, 10 figures and 2 tables. Published in Nature Astronomy. November 20 (2017)

In this paper, we address the issue of the stability of the thermal equilibrium of large quantum systems with respect to variations of the thermal contact between them. We study the Schr\"odinger time evolution of a free bosonic field in two coupled one-dimensional cavities after a sudden change of the contact between the cavities. Though the coupling we consider is thermodynamically small, modifying it has a considerable impact on the two-point correlation functions of the system. We find that they do not return to equilibrium but essentially oscillate with a period proportional to the length of the cavities. We compare this coupled cavities system with the perfect gas which is described by similar expressions but behaves very differently.

The largest eigenvalue of the adjacency matrix of the networks is a key quantity determining several important dynamical processes on complex networks. Based on this fact, we present a quantitative, objective characterization of the dynamical importance of network nodes and links in terms of their effect on the largest eigenvalue. We show how our characterization of the dynamical importance of nodes can be affected by degree-degree correlations and network community structure. We discuss how our characterization can be used to optimize techniques for controlling certain network dynamical processes and apply our results to real networks., Comment: 4 pages, 4 figures

Even before 9/11 there were claims that the nature of war had changed fundamentally. The 9/11 attacks created an urgent need to understand contemporary wars and their relationship to older conventional and terrorist wars, both of which exhibit remarkable regularities. The frequency-intensity distribution of fatalities in "old wars", 1816-1980, is a power-law with exponent 1.80. Global terrorist attacks, 1968-present, also follow a power-law with exponent 1.71 for G7 countries and 2.5 for non-G7 countries. Here we analyze two ongoing, high-profile wars on opposite sides of the globe - Colombia and Iraq. Our analysis uses our own unique dataset for killings and injuries in Colombia, plus publicly available data for civilians killed in Iraq. We show strong evidence for power-law behavior within each war. Despite substantial differences in contexts and data coverage, the power-law coefficients for both wars are tending toward 2.5, which is a value characteristic of non-G7 terrorism as opposed to old wars. We propose a plausible yet analytically-solvable model of modern insurgent warfare, which can explain these observations., Comment: For more information, please contact M.Spagat@rhul.ac.uk or n.johnson@physics.ox.ac.uk