Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We quantify the relative role of galaxy environment and bar presence on AGN triggering in face-on spiral galaxies using a volume-limited sample with 0.02 &lt; <jats:italic>z</jats:italic> &lt; 0.055, <jats:italic>M</jats:italic> <jats:sub> <jats:italic>r</jats:italic> </jats:sub> &lt; 19.5, and <jats:italic>σ</jats:italic> &gt; 70 <jats:inline-formula> <jats:tex-math> <?CDATA $\,\mathrm{km}\,{{\rm{s}}}^{-1}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlabb66fieqn1.gif" xlink:type="simple" /> </jats:inline-formula> selected from Sloan Digital Sky Survey (SDSS) Data Release 7. To separate their possible entangled effects, we divide the sample into bar and non-bar samples, and each sample is further divided into three environment cases of isolated galaxies, interacting galaxies with a pair, and cluster galaxies. The isolated case is used as a control sample. For these six cases, we measure AGN fractions at a fixed central star formation rate and central velocity dispersion, <jats:italic>σ</jats:italic>. We demonstrate that the internal process of the bar-induced gas inflow is more efficient in AGN triggering than the external mechanism of the galaxy interactions in groups and cluster outskirts. The significant effects of bar instability and galaxy environments are found in galaxies with a relatively less massive bulge. We conclude that from the perspective of AGN–galaxy coevolution, a massive black hole is one of the key drivers of spiral galaxy evolution. If it is not met, a bar instability helps the evolution, and in the absence of bars, galaxy interactions/mergers become important. In other words, in the presence of a massive central engine, the role of the two gas inflow mechanisms is reduced or almost disappears. We also find that bars in massive galaxies are very decisive in increasing AGN fractions when the host galaxies are inside clusters.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The origin of magnetic fields in the universe is an open problem. Seed magnetic fields possibly produced in early times may have survived up to the present day close to their original form, providing an untapped window to the primeval universe. The recent observations of high-energy neutrinos from the blazar TXS 0506+056 in association with an electromagnetic counterpart in a broad range of wavelengths can be used to probe intergalactic magnetic fields via the time delay between the neutrinos and gamma-rays as well as the time dependence of the gamma-ray fluxes. Using extensive three-dimensional Monte Carlo simulations, we constrain both the magnetic-field strength and, for the first time, its coherence length, considering six orders of magnitude for each.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Merging binary neutron stars are thought to be formed predominantly via isolated binary evolution. In this standard formation scenario, the first-born neutron star goes through a recycling process and might be rapidly spinning during the final inspiral, whereas the second-born star is expected to have effectively zero spin at merger. Based on this feature, we propose a new framework for the astrophysical characterization of binary neutron stars observed from their gravitational wave emission. We further propose a prior for the dimensionless spins of recycled neutron stars, given by a gamma distribution with a shape parameter of 2 and a scale parameter of 0.012, extrapolated from radio pulsar observations of Galactic binary neutron stars. Interpreting GW170817 and GW190425 in the context of the standard formation scenario and adopting the gamma-distribution prior, we find positive support (with a Bayes factor of 6, over the nonspinning hypothesis) for a spinning recycled neutron star in GW190425, whereas the spin of the recycled neutron star in GW170817 is small and consistent with our prior. We measure the masses of the recycled (slow) neutron stars in GW170817 and GW190425 to be <jats:inline-formula> <jats:tex-math> <?CDATA ${1.34}_{-0.09}^{+0.12}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlabb6eaieqn1.gif" xlink:type="simple" /> </jats:inline-formula> <jats:inline-formula> <jats:tex-math> <?CDATA $({1.38}_{-0.11}^{+0.11}){M}_{\odot }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlabb6eaieqn2.gif" xlink:type="simple" /> </jats:inline-formula> and <jats:inline-formula> <jats:tex-math> <?CDATA ${1.64}_{-0.11}^{+0.13}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlabb6eaieqn3.gif" xlink:type="simple" /> </jats:inline-formula> <jats:inline-formula> <jats:tex-math> <?CDATA $({1.66}_{-0.12}^{+0.12}){M}_{\odot }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlabb6eaieqn4.gif" xlink:type="simple" /> </jats:inline-formula>, with 68% credibility, respectively. We discuss implications for the astrophysical origins of these two events and outline future prospects of studying binary neutron stars using our framework.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We have observed PSR B1534+12 (J1537+1155), a pulsar with a neutron star companion, using the Five-hundred-meter Aperture Spherical radio Telescope. We found that this pulsar shows two distinct emission states: a weak state with a wide pulse profile and a burst state with a narrow pulse profile. The weak state is always present. We cannot, with our current data, determine whether the pulse energy of the weak state follows a normal or a log-normal distribution. The burst state energy distribution follows a power law. The amplitude of the single-pulse emission in the burst state varies significantly; the peak flux intensity of the brightest pulse is 334 times stronger than that of the average pulse. We also examined the timing precision achievable using only bright pulses, which showed no demonstrable improvement because of pulse jitter and therefore quantified the jitter noise level for this pulsar.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>On Earth near sunset, the Sun may cast “crepuscular rays” such that clouds near the horizon obscure the origin of light scattered in bright rays. In principle, active galactic nuclei (AGN) should be able to produce similar effects. Using new Hubble Space Telescope (HST) near-infrared and optical observations, we show that the active galaxy IC 5063 contains broad radial rays extending to ≳11 kpc from the nucleus. We argue that the bright rays may arise from dusty scattering of continuum emission from the active nucleus, while the dark rays are due to shadowing near the nucleus, possibly by a warped torus. We also consider alternative AGN-related and stellar origins for the extended light.</jats:p>