Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Variability is a typical observation feature of Fermi blazars, which sometimes shows quasi-periodic oscillation (QPO). In this work, we obtain 5 day binned light curves (with a time coverage of ∼12.9 yr) for S5 1044+71, based on Fermi-LAT data; apply five different methods—Date-compensated Discrete Fourier Transform, Jurkevich, Lomb–Scargle Periodogram, a Fortran 90 program, and the Weighted Wavelet Z-transform—to the <jats:italic>γ</jats:italic>-ray light curve; and find a possible QPO of 3.06 ± 0.43 yr at the significance level of ∼3.6<jats:italic>σ</jats:italic>. A binary black hole model, including an accretion model and a dual-jet model, is used to explain this quasi-periodic variability. We also estimate the Doppler factors and the apparent velocity for the two jet components. We speculate that this <jats:italic>γ</jats:italic>-ray quasi-periodic modulation suggests the presence of a binary supermassive black hole in S5 1044+71.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Understanding the mechanism(s) of solar wind acceleration is important in astrophysics and geophysics. A promising model of solar wind acceleration is known as the wave/turbulence-driven (WTD) model, in which Alfvén waves feed energy to the solar wind. In this study, we tested the WTD model with global measurements of wind speed from interplanetary scintillation (IPS) observations. For Carrington rotations in minimal and maximal activity phases, we selected field lines calculated by the potential-field source-surface method in high and midlatitudes and compared the simulated and observed wind velocities. The simulation was performed in a self-consistent manner by solving the magnetohydrodynamic equations from the photosphere to the solar wind. In high-latitude regions, the simulated solar wind velocity agrees better with the IPS observation than with the classical Wang–Sheeley empirical estimation, both in maximal and minimal activity phases. In midlatitude regions, the agreement worsens, possibly because of the inaccuracy of the WTD model and/or the magnetic-field extrapolation. Our results indicate that the high-latitude solar wind is likely to be driven by waves and turbulence and that the physics-based prediction of the solar wind velocity is highly feasible with an improved magnetic-field extrapolation.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a rest-frame UV–optical (<jats:italic>λ</jats:italic> = 2500–6400 Å) stacked spectrum representative of massive quiescent galaxies at 1.0 &lt; <jats:italic>z</jats:italic> &lt; 1.3 with log(<jats:italic>M</jats:italic> <jats:sub>*</jats:sub>/<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) &gt; 10.8. The stack is constructed using VANDELS survey data, combined with new KMOS observations. We apply two independent full-spectral-fitting approaches, measuring a total metallicity [Z/H] = −0.13 ± 0.08 with <jats:sc>Bagpipes</jats:sc> and [Z/H] = 0.04 ± 0.14 with <jats:sc>Alf</jats:sc>, a fall of ∼0.2–0.3 dex compared with the local universe. We also measure an iron abundance [Fe/H] = −0.18 ± 0.08, a fall of ∼0.15 dex compared with the local universe. We measure the alpha enhancement via the magnesium abundance, obtaining [Mg/Fe] = 0.23 ± 0.12, consistent with galaxies of similar mass in the local universe, indicating no evolution in the average alpha enhancement of log(<jats:italic>M</jats:italic> <jats:sub>*</jats:sub>/<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) ∼ 11 quiescent galaxies over the last ∼8 Gyr. This suggests the very high alpha enhancements recently reported for several bright <jats:italic>z</jats:italic> ∼ 1–2 quiescent galaxies are due to their extreme masses, log(<jats:italic>M</jats:italic> <jats:sub>*</jats:sub>/<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) ≳ 11.5, in accordance with the well-known downsizing trend, rather than being typical of the <jats:italic>z</jats:italic> ≳ 1 population. The metallicity evolution we observe with redshift (falling [Z/H], [Fe/H], constant [Mg/Fe]) is consistent with recent studies. We recover a mean stellar age of <jats:inline-formula> <jats:tex-math> <?CDATA ${2.5}_{-0.4}^{+0.6}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>2.5</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.6</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac5b62ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> Gyr, corresponding to a formation redshift <jats:inline-formula> <jats:tex-math> <?CDATA ${z}_{\mathrm{form}}={2.4}_{-0.3}^{+0.6}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>z</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>form</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>2.4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.3</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.6</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac5b62ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>. Recent studies have obtained varying average formation redshifts for <jats:italic>z</jats:italic> ≳ 1 massive quiescent galaxies, and, as these studies report consistent metallicities, we identify models with different star formation histories as the most likely cause. Larger spectroscopic samples from upcoming ground-based instruments will provide precise constraints on ages and metallicities at <jats:italic>z</jats:italic> ≳ 1. Combining these with precise stellar mass functions for <jats:italic>z</jats:italic> &gt; 2 quiescent galaxies from the James Webb Space Telescope will provide an independent test of formation redshifts derived from spectral fitting.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We introduce a new quantitative approach for assessing the quality of coronal magnetic field models. The method compares the location of the magnetic neutral line at a specified height in the magnetic field model with the locations of localized density peaks in the coronal electron density, as measured using coronal rotational tomography. This approach is flexible to the presence of pseudostreamers in the coronal magnetic field, as well as folds in the streamer belt. We present an example application during mid-2010 when the white-light streamer-belt structure is complex and the emergence of a large active region on the far side of the Sun presents a challenge for modeling the coronal magnetic structure.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Galaxies can be characterized by many internal properties such as stellar mass, gas metallicity, and star formation rate. We quantify the amount of cosmological and astrophysical information that the internal properties of individual galaxies and their host dark matter halos contain. We train neural networks using hundreds of thousands of galaxies from 2000 state-of-the-art hydrodynamic simulations with different cosmologies and astrophysical models of the CAMELS project to perform likelihood-free inference on the value of the cosmological and astrophysical parameters. We find that knowing the internal properties of a single galaxy allows our models to infer the value of Ω<jats:sub>m</jats:sub>, at fixed Ω<jats:sub>b</jats:sub>, with a ∼10% precision, while no constraint can be placed on <jats:italic>σ</jats:italic> <jats:sub>8</jats:sub>. Our results hold for any type of galaxy, central or satellite, massive or dwarf, at all considered redshifts, <jats:italic>z</jats:italic> ≤ 3, and they incorporate uncertainties in astrophysics as modeled in CAMELS. However, our models are not robust to changes in subgrid physics due to the large intrinsic differences the two considered models imprint on galaxy properties. We find that the stellar mass, stellar metallicity, and maximum circular velocity are among the most important galaxy properties to determine the value of Ω<jats:sub>m</jats:sub>. We believe that our results can be explained by considering that changes in the value of Ω<jats:sub>m</jats:sub>, or potentially Ω<jats:sub>b</jats:sub>/Ω<jats:sub>m</jats:sub>, affect the dark matter content of galaxies, which leaves a signature in galaxy properties distinct from the one induced by galactic processes. Our results suggest that the low-dimensional manifold hosting galaxy properties provides a tight direct link between cosmology and astrophysics.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The view on velocity structures in molecular clouds and their relationship with magnetic fields (<jats:italic>B</jats:italic> field) has evolved during the past decade from almost no correlation to highly parallel. Our numerical simulations suggest a more nuanced picture: Depending on whether the self-gravity is dynamically dominant, the velocity field can be governed by either contraction (at high densities) or turbulence (at low densities), and their anisotropies will tend to be either perpendicular or parallel, respectively, to the <jats:italic>B</jats:italic> fields. High-density regions are always embedded in the low-density fore/background, so the velocity behaviors from lines of sight (LOSs) with high column densities will be a mixture of orthogonal anisotropies, which can be hard to interpret and necessitates zooming in onto certain LOS scales to better characterize localized behaviors. We tested and confirmed the above prediction with CO observations of the Taurus molecular cloud.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Stars are likely embedded in the gas disks of active galactic nuclei (AGN). Theoretical models predict that in the inner regions of the disk, these stars accrete rapidly, with fresh gas replenishing hydrogen in their cores faster than it is burned into helium, effectively stalling their evolution at hydrogen burning. We produce order-of-magnitude estimates of the number of such stars in a fiducial AGN disk. We find numbers of order 10<jats:sup>2–4</jats:sup>, confined to the inner <jats:italic>r</jats:italic> <jats:sub>cap</jats:sub> ∼ 3000<jats:italic>r</jats:italic> <jats:sub> <jats:italic>s</jats:italic> </jats:sub> ∼ 0.03 pc. These stars can profoundly alter the chemistry of AGN disks, enriching them in helium and depleting them in hydrogen, both by order-unity amounts. We further consider mergers between these stars and other disk objects, suggesting that star–star mergers result in rapid mass loss from the remnant to restore an equilibrium mass, while star–compact object mergers may result in exotic outcomes and even host binary black hole mergers within themselves. Finally, we examine how these stars react as the disk dissipates toward the end of its life, and find that they may return mass to the disk fast enough to extend its lifetime by a factor of several and/or may drive powerful outflows from the disk. Post-AGN, these stars rapidly lose mass and form a population of stellar mass black holes around 10<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. Due to the complex and uncertain interactions between embedded stars and the disk, their plausible ubiquity, and their order-unity impact on disk structure and evolution, they must be included in realistic disk models.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>There is some observational evidence for the existence of multiple X line magnetic reconnection (MR) in various planetary magnetotails but the overall observationally based MR topology in two or three dimensions is still not available. This study reports the first 2D structures of MR with multiple X lines and magnetic islands observed by the Magnetospheric Multiscale (MMS) spacecraft in the Earth’s magnetotail based on the Grad–Shafranov (GS) reconstruction model with temperature anisotropy. The tearing mode geometry is revealed within the spatial domain of 3800 km × 800 km with multiple X lines and magnetic islands on the spatial scale of the sub-ion inertial length or a few times the electron gyroradius. The MR event is seen by all four MMS spacecraft but the magnetic islands are caught only by the MMS3 spacecraft, and exhibit large firehose-type temperature anisotropy. The GS reconstructed maps based on the MMS1, 2, and 4 show a single X line and partial ion-scale magnetic islands with a smaller degree of temperature anisotropy. The reconstruction results remain the same for various energy closures, and the firehose-type anisotropy is found to yield smaller magnetic islands than the isotropic cases, which is opposite to the previous findings for MR events with mirror-type temperature anisotropy.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We study emission line profiles of 21 nearby low-mass (<jats:italic>M</jats:italic> <jats:sub>*</jats:sub> = 10<jats:sup>4</jats:sup>–10<jats:sup>7</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) galaxies in deep medium-high resolution spectra taken with Magellan/MagE. These low-mass galaxies are actively star-forming systems with high specific star formation rates of ∼100–1000 Gyr<jats:sup>−1</jats:sup> that are well above the star formation main sequence and its extrapolation. We identify broad-line components of H<jats:italic>α</jats:italic> and [O <jats:sc>iii</jats:sc>]<jats:italic>λ</jats:italic>5007 emission in 14 out of the 21 galaxies that cannot be explained by the MagE instrumental profile or the natural broadening of line emission. We conduct double-Gaussian profile fitting to the emission of the 14 galaxies, and find that the broad-line components have line widths significantly larger than those of the narrow-line components, indicative of galactic outflows. The broad-line components have moderately large line widths of ∼100 km s<jats:sup>−1</jats:sup>. We estimate the maximum outflow velocities <jats:italic>v</jats:italic> <jats:sub>max</jats:sub> and obtain values of ≃60–200 km s<jats:sup>−1</jats:sup>, which are found to be comparable to or slightly larger than the escape velocities. Positive correlations of <jats:italic>v</jats:italic> <jats:sub>max</jats:sub> with star formation rates, stellar masses, and circular velocities extend down into this low-mass regime. Broad- to narrow-line flux ratios (BNRs) are generally found to be smaller than those of massive galaxies. The small <jats:italic>v</jats:italic> <jats:sub>max</jats:sub> and BNRs suggest that the mass-loading factors <jats:italic>η</jats:italic> can be as small as 0.1–1 or below, in contrast to the large <jats:italic>η</jats:italic> of energy-driven outflows predicted by numerical simulations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Accretion is one of the defining characteristics of classical T Tauri stars, fueled by the presence of a circumstellar disk comprised of dust and gas. Accretion produces a UV and optical excess, while re-radiated emission at the inner edge of the dust component of the disk produces a near-infrared (NIR) excess. The interplay between stars and their disks helps regulate protoplanetary disk evolution and dispersal, which is key to a full understanding of planet formation. To investigate the relations between NIR excess and optical excess in both single and binary stars, we used an archival sample of spectroscopically characterized members of the Taurus star-forming region (<jats:italic>τ</jats:italic> ∼ 1–2 Myr) with measured luminosities, spectral types, and optical veiling. We combined the archival sample with the Two Micron All Sky Survey and Wide-field Infrared Survey Explorer NIR photometry and high-resolution imaging surveys. We found that NIR and optical excesses are correlated in multiple NIR photometric bands, suggesting that they are closely related, likely because more massive disks have higher inner dust disk walls and are also associated with higher accretion rates. We also found that multiplicity has no impact on accretion or inner disk properties in a sample with a wide range of separations, but the sample was too small to specifically investigate close binaries, where the effects of multiplicity on disk properties should be most significant.</jats:p>