Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Delta-gravity (DG) is a gravitational model based on an extension of general relativity given by a new symmetry called <jats:inline-formula> <jats:tex-math> <?CDATA $\tilde{\delta }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabddc3ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>. In this model, new matter fields are added to the original matter fields, motivated by the additional symmetry. We call them <jats:inline-formula> <jats:tex-math> <?CDATA $\tilde{\delta }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabddc3ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> matter fields. This model predicts an accelerating universe without the need to introduce a cosmological constant. In this work, we study the scalar cosmic microwave background (CMB) temperature (TT) power spectrum predicted by DG using an analytical hydrodynamic approach. To fit the Planck satellite’s data with the DG model, we used a Markov Chain Monte Carlo analysis. We also include a study about the compatibility between Type Ia supernovae (SNe Ia) and CMB observations in the DG context. Finally, we obtain the scalar CMB TT power spectrum and the fitted parameters needed to explain both SN Ia data and CMB measurements. The results are in reasonable agreement with both observations considering the analytical approximation. We also discuss whether the Hubble constant and the accelerating universe are in concordance with the observational evidence in the DG context.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This paper studies the energy dissipation of nonthermal electrons in the chromospheric flare ribbons during the peak time of a Geostationary Operational Environmental Satellite X-class flare (SOL2011-09-06) using desaturated Solar Dynamics Observatory/Atmospheric Imaging Assembly extreme-ultraviolet (EUV) narrow-band images. The temperature distribution in emission measure, called the differential emission measure (DEM), derived from the EUV fluxes from the flare ribbons shows an increase in the emission measure up to a temperature around 9 × 10<jats:sup>6</jats:sup> K, followed by a steep decline at higher temperatures. In contrast, the flare loop reaches temperatures up to 27 × 10<jats:sup>6</jats:sup> K. This result is in agreement with previously reported single-temperature measurements using soft X-ray filter images, as well as DEM distributions reported for smaller flares obtained from EUV line observations. The main difference between small and large flares appears to be an increased emission measure in the flare ribbons, while the ribbon peak temperature is similar for all flares. This is different from the flare loop temperatures, where the hottest temperatures occur in the largest flares. However, the physically relevant quantity for energy dissipation, the energy content of the heated plasma as a function of temperature, does not need to peak at the same temperature as the DEM. The poorly constrained source thickness in radial extent of the flare ribbons has a significant impact on the shape of the differential thermal energy distribution. In particular, if the highest temperatures occur over a wide radial extent as “evaporating” plasma starts expending, the largest amount of energy could potentially be hidden above the peak temperature of the DEM.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present detailed observations of photoionization conditions and galaxy kinematics in 11 <jats:italic>z</jats:italic> = 1.39–2.59 radio-loud quasar host galaxies. Data were taken with the OSIRIS integral field spectrograph and the adaptive optics system at the W. M. Keck Observatory that targeted nebular emission lines (H<jats:italic>β</jats:italic>, [O <jats:sc>iii</jats:sc>], H<jats:italic>α</jats:italic>, [N <jats:sc>ii</jats:sc>]) redshifted into the near-infrared (1–2.4 <jats:italic>μ</jats:italic>m). We detect extended ionized emission on scales ranging from 1 to 30 kpc photoionized by stars, shocks, and active galactic nuclei (AGN). Spatially resolved emission-line ratios indicate that our systems reside off the star formation and AGN-mixing sequence on the Baldwin, Phillips, &amp; Terlevich diagram at low redshift. The dominant cause of the difference between line ratios of low-redshift galaxies and our sample is due to lower gas-phase metallicities, which are 2–5× less compared to galaxies with AGN in the nearby universe. Using gas velocity dispersion as a proxy to stellar velocity dispersion and dynamical mass measurement through inclined disk modeling, we find that the quasar host galaxies are undermassive relative to their central supermassive black hole mass, with all systems residing off the local scaling (<jats:italic>M</jats:italic> <jats:sub>•</jats:sub>–<jats:italic>σ</jats:italic>, <jats:italic>M</jats:italic> <jats:sub>•</jats:sub>–<jats:italic>M</jats:italic> <jats:sub>*</jats:sub>) relationship. These quasar host galaxies require substantial growth, up to an order of magnitude in stellar mass, to grow into present-day massive elliptical galaxies. Combining these results with part I of our sample paper, we find evidence for winds capable of causing feedback before the AGN host galaxies land on the local scaling relation between black hole and galaxy stellar mass, and before the enrichment of the interstellar medium to a level observed in local galaxies with AGN.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Jets (fast collimated outflows) are claimed to be the main shaping agent of the most asymmetric planetary nebulae (PNs), as they impinge on the circumstellar material at late stages of the asymptotic giant branch phase. The first jet detected in a PN was that of NGC 2392, yet there is no available image because of its low surface brightness contrast with the bright nebular emission. Here we take advantage of the tomographic capabilities of Gran Telescopio de Canarias Multi-Espectrógrafo en GTC de Alta Resolución para Astronomía high-dispersion integral field spectroscopic observations of the jet in NGC 2392 to gain unprecedented details of its morphology and kinematics. The jet of NGC 2392 is found to emanate from the central star, break through the walls of the inner shell of this iconic PN and extend outside the nebula’s outermost regions with an S-shaped morphology suggestive of precession. At odds with the fossil jets found in mature PNs, the jet in NGC 2392 is currently being collimated and launched. The high nebular excitation of NGC 2392, which implies an He<jats:sup>++</jats:sup>/He ionization fraction too high to be attributed to the known effective temperature of the star, has been proposed in the past to hint at the presence of a hot white dwarf companion. In conjunction with the hard X-ray emission from the central star, the present-day jet collimation would support the presence of such a double-degenerate system where one component undergoes accretion from a remnant circumbinary disk of the common envelope phase.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The study of low surface brightness light in large, deep imaging surveys is still uncharted territory as automated data reduction pipelines over-subtract or eliminate this light. Using archival data of the A85 cluster of galaxies taken with the Hyper Suprime-Cam on the Subaru Telescope, we show that using careful data processing can unveil the diffuse light within the cluster, the intracluster light. We reach surface brightness limits of <jats:inline-formula> <jats:tex-math> <?CDATA ${\mu }_{g}^{\mathrm{limit}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabddb6ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>(3<jats:italic>σ</jats:italic>, 10″ × 10″) = 30.9 and <jats:inline-formula> <jats:tex-math> <?CDATA ${\mu }_{i}^{\mathrm{limit}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabddb6ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>(3<jats:italic>σ</jats:italic>, 10″ × 10″) = 29.7 mag arcsec<jats:sup>−2</jats:sup>. We measured the radial surface brightness profiles of the brightest cluster galaxy out to the intracluster light (radius ∼215 kpc) for the <jats:italic>g</jats:italic> and <jats:italic>i</jats:italic> bands. We found that both the surface brightness and the color profiles become shallower beyond ∼75 kpc suggesting that a distinct component, the intracluster light, starts to dominate at that radius. The color of the profile at ∼100 kpc suggests that the buildup of the intracluster light of A85 occurs by the stripping of massive (∼10<jats:sup>10</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) satellites. The measured fraction of this light ranges from 8%–30% in <jats:italic>g</jats:italic>, depending on the definition of intracluster light chosen.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Magnetohydrodynamic (MHD) turbulence plays an important role for the fast energy release and wave structures related to coronal mass ejections (CMEs). The CME plasma has been observed to be strongly heated during solar eruptions, but the heating mechanism is not understood. In this paper, we focus on the hot, dense region at the bottom of the CME and the generation of coronal wave trains therein using a high-resolution 2.5D MHD simulation. Our results show that the interaction between the tearing current sheet and the turbulence, including the termination shocks (TSs) at the bottom of the CME, can make a significant contribution to heating the CME, and the heating rate in this region is found to be greater than the kinetic energy transfer rate. Also, the turbulence can be somewhat amplified by the TSs. The compression ratio of the TS under the CME can exceed 4 due to thermal conduction, but such a strong TS is hardly detectable in all Solar Dynamics Observatory/Atmospheric Imaging Assembly bands. And turbulence is an indispensable source for the periodic generation of coronal wave trains around the CME.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We characterize the kinematic and chemical properties of 589 Galactic anticenter substructure stars (GASS) with K/M giants in integrals-of-motion space. These stars likely include members of previously identified substructures such as Monoceros, A13, and the Triangulum-Andromeda cloud. We show that these stars are in nearly circular orbits on both sides of the Galactic plane. We can see a velocity (<jats:italic>V</jats:italic> <jats:sub> <jats:italic>Z</jats:italic> </jats:sub>) gradient along <jats:italic>Y</jats:italic>-axis especially for the south GASS members. Our GASS members have similar energy and angular momentum distributions to thin-disk stars. Their location in [<jats:italic>α</jats:italic>/M] versus [M/H] space is more metal-poor than typical thin-disk stars, with [<jats:italic>α</jats:italic>/M] lower than that of the thick disk. We infer that our GASS members are part of the outer metal-poor disk stars and that the outer disk extends to 30 kpc. Considering the distance range and <jats:italic>α</jats:italic>-abundance features, GASS could be formed after the thick disk was formed due to the molecular cloud density decreasing in the outer disk where the star-formation rate might be less efficient compared to the inner disk.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Supernova remnant RX J1713.7-3946 has exhibited the largest surface brightness and a detailed spectral and shell-type morphology, and is one of the brightest TeV sources. The recent H.E.S.S. observation of RX J1713.7-3946 revealed a broken power-law GeV–TeV gamma-ray and a more extended gamma-ray spatial radial profile than in the X-ray band. Based on the diffusion shock acceleration model, we solve spherically symmetric hydrodynamic equations and particle transport equations, and investigate the multi-band non-thermal emission of RX J1713.7-3946 and radial profiles of its surface brightness for two selected zones in the leptonic scenario for gamma-ray emission. We found (1) the diffusion coefficient has a weak energy dependence, and the Kolmogorov type is favored; (2) the magnetic field strength can vary linearly or nonlinearly with radius for different surrounding environments because of possible turbulence in the shock downstream region, and compressional amplification is likely to exist at the shock front; (3) the non-thermal photons from radio to X-ray bands are dominated by synchrotron emission from relativistic electrons if the GeV–TeV gamma-rays are produced by inverse Compton scattering from these electrons interacting with the background photons; then the X-ray and gamma-ray radial profiles can be reproduced except for the more extended gamma-ray emission.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Although interstellar grains are known to be aspherical, their actual shapes remain poorly constrained. We assess whether three continuous distributions of ellipsoids (CDEs) from the literature are suitable for describing the shapes of interstellar grains. Randomly selected shapes from each distribution are shown as illustrations. The often-used Bohren–Huffman CDE includes a very large fraction of extreme shapes: fully 10% of random draws have axial ratio <jats:italic>a</jats:italic> <jats:sub>3</jats:sub>/<jats:italic>a</jats:italic> <jats:sub>1</jats:sub> &gt; 19.7, and 5% have <jats:italic>a</jats:italic> <jats:sub>3</jats:sub>/<jats:italic>a</jats:italic> <jats:sub>1</jats:sub> &gt; 33. The CDE2 distribution includes a much smaller fraction of extreme shapes, and appears to be the most realistic. For each of the three CDEs considered, we derive shape-averaged cross sections for extinction and polarization in the Rayleigh limit. Finally, we describe a method for “synthesizing” a dielectric function for an assumed shape or shape distribution if the actual absorption cross sections per grain volume in the Rayleigh limit are known from observations. This synthetic dielectric function predicts the wavelength dependence of polarization, which can then be compared to observations to constrain the grain shape.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Motivated by the observations and linear theory analysis of ionospheric irregularities at Mars, we performed numerical simulations of the nonlinear evolution of the electromagnetic gradient drift instability in the Martian ionospheric dynamo region. The seeding source of ionospheric irregularities is perturbation zonal neutral wind. We found that the perturbation electric fields induced by the gradient drift instability can convect lower density plasma into higher density plasma at higher altitudes. Then, the associated perturbation magnetic field and electric field can cause the velocity shear of the plasma, which induced the Kelvin–Helmholtz instability at higher altitude. The Kelvin–Helmholtz instabilities furthermore lead to smaller-scale irregularities in plasma density, magnetic field, and electric field in the Martial ionosphere. Key points: (1) Nonlinear simulation of small-scale ionospheric irregularities at Mars was present. (2) Ionospheric irregularities at Mars can be seeded by the perturbation neutral winds. (3) Model results are comparable to linear theory analysis and satellite observations.</jats:p>