Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We report on a spectroscopic program to search for dual quasars using Subaru Hyper Suprime-Cam (HSC) images of SDSS quasars, which represent an important stage during galaxy mergers. Using Subaru/FOCAS and Gemini-N/GMOS, we identify three new physically associated quasar pairs having projected separations less than 20 kpc, out of 26 observed candidates. These include the discovery of the highest-redshift (<jats:italic>z</jats:italic> = 3.1) quasar pair with a separation &lt;10 kpc. Based on the sample acquired to date, the success rate of identifying physically associated dual quasars is 19% when excluding stars based on their HSC colors. Using the full sample of six spectroscopically confirmed dual quasars, including three previously published, we find that the black holes in these systems have black hole masses (<jats:italic>M</jats:italic> <jats:sub>BH</jats:sub> ∼ 10<jats:sup>8−9</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>), bolometric luminosities (log <jats:italic>L</jats:italic> <jats:sub>bol</jats:sub> ∼ 44.5–47.5 erg s<jats:sup>–1</jats:sup>) and Eddington ratios (0.01–0.3) similar to single SDSS quasars. We measure the stellar mass of their host galaxies based on 2D image decomposition of the five-band (<jats:italic>grizy</jats:italic>) optical emission and assess the mass relation between supermassive black holes (SMBHs) and their hosts. Dual SMBHs appear to have elevated masses relative to their host galaxies. Thus, mergers may not necessarily align such systems onto the local mass relation, as suggested by the Horizon-AGN simulation. This study suggests that dual luminous quasars are triggered by mergers prior to the final coalescence of the two SMBHs, resulting in early mass growth of the black holes relative to their host galaxies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The radio source 1146+596 is hosted by the elliptical/S0 galaxy NGC 3894, with a low-luminosity active nucleus. The radio structure is compact, suggesting a very young age for the jets in the system. Recently, the source has been confirmed as a high-energy (HE; &gt;0.1 GeV) <jats:italic>γ</jats:italic>-ray emitter in the most recent accumulation of Fermi Large Area Telescope data. Here we report on the analysis of the archival Chandra X-ray Observatory data for the central part of the galaxy, consisting of a single 40 ks long exposure. We have found that the core spectrum is best fitted by a combination of an ionized thermal plasma with a temperature of ≃0.8 keV, and a moderately absorbed power-law component (photon index Γ = 1.4 ± 0.4, hydrogen column density <jats:italic>N</jats:italic> <jats:sub>H</jats:sub>/10<jats:sup>22</jats:sup> cm<jats:sup>−2</jats:sup> = 2.4 ± 0.7). We have also detected the iron K<jats:italic>α</jats:italic> line at 6.5 ± 0.1 keV, with a large equivalent width of <jats:inline-formula> <jats:tex-math> <?CDATA ${1.0}_{-0.5}^{+0.9}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>1.0</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.5</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.9</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac1ff5ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> keV. Based on the simulations of Chandra's point-spread function, we have concluded that while the soft thermal component is extended on the scale of the galaxy host, the hard X-ray emission within the narrow photon energy range 6.0–7.0 keV originates within the unresolved core (effectively the central kiloparsec radius). The line is therefore indicative of the X-ray reflection from a cold neutral gas in the central regions of NGC 3894. We discuss the implications of our findings in the context of the X-ray Baldwin effect. NGC 3894 is the first young radio galaxy detected in HE <jats:italic>γ</jats:italic>-rays with the iron K<jats:italic>α</jats:italic> line.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We select eight nearby active galactic nuclei (AGNs) which, based on previous work, appear to be Compton-thin in the line of sight. We model with <jats:sc>mytorus</jats:sc> their broadband X-ray spectra from 20 individual observations with Suzaku, accounting self-consistently for Fe K<jats:italic>α</jats:italic> line emission, as well as direct and scattered continuum from matter with finite column density and solar Fe abundance. Our model configuration allows us to measure the global, out of the line of sight, equivalent hydrogen column density separately from that in the line of sight. For 5 out of 20 observations (in 3 AGNs) we find that the global column density is in fact ≳1.5 × 10<jats:sup>24</jats:sup> cm<jats:sup>−2</jats:sup>, consistent with the distant scattering matter being Compton-thick. For a fourth AGN, two out of five observations are also consistent with being Compton-thick, although with large errors. Some of these AGNs have been reported to host relativistically broadened Fe K<jats:italic>α</jats:italic> emission. Based on our modeling, the Fe K<jats:italic>α</jats:italic> emission line is not resolved in all but two Suzaku observations, and the data can be fitted well with models that only include a narrow Fe K<jats:italic>α</jats:italic> emission line.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Supersonically induced gas objects (SIGOs), are structures with little to no dark-matter component predicted to exist in regions of the universe with large relative velocities between baryons and dark matter at the time of recombination. They have been suggested to be the progenitors of present-day globular clusters. Using simulations, SIGOs have been studied on small scales (around 2 Mpc) where these relative velocities are coherent. However, it is challenging to study SIGOs using simulations on large scales due to the varying relative velocities at scales larger than a few Mpc. Here, we study SIGO abundances semi-analytically: using perturbation theory, we predict the number density of SIGOs analytically, and compare these results to small-box numerical simulations. We use the agreement between the numerical and analytic calculations to extrapolate the large-scale variation of SIGO abundances over different stream velocities. As a result, we predict similar large-scale variations of objects with high gas densities before reionization that could possibly be observed by JWST. If indeed SIGOs are progenitors of globular clusters, then we expect a similar variation of globular cluster abundances over large scales. Significantly, we find that the expected number density of SIGOs is consistent with observed globular cluster number densities. As a proof-of-concept, and because globular clusters were proposed to be natural formation sites for gravitational wave sources from binary black-hole mergers, we show that SIGOs should imprint an anisotropy on the gravitational wave signal on the sky, consistent with their distribution.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Dynamical studies of dense structures within molecular clouds often conclude that the most massive clumps contain too little kinetic energy for virial equilibrium, unless they are magnetized to an unexpected degree. This raises questions about how such a state might arise, and how it might persist long enough to represent the population of massive clumps. In an effort to reexamine the origins of this conclusion, we use ammonia line data from the Green Bank Ammonia Survey and Planck-calibrated dust emission data from Herschel to estimate the masses and kinetic and gravitational energies for dense clumps in the Gould Belt clouds. We show that several types of systematic error can enhance the appearance of low kinetic-to-gravitational energy ratios: insufficient removal of foreground and background material; ignoring the kinetic energy associated with velocity differences across a resolved cloud; and overcorrecting for stratification when evaluating the gravitational energy. Using an analysis designed to avoid these errors, we find that the most massive Gould Belt clumps harbor virial motions, rather than subvirial ones. As a by-product, we present a catalog of masses, energies, and virial energy ratios for 85 Gould Belt clumps.</jats:p>