Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We report the Fermi LAT <jats:italic>γ</jats:italic>-ray detection of the 2021 outburst of the symbiotic recurrent nova RS Ophiuchi. In this system, unlike classical novae from cataclysmic binaries, the ejecta from the white dwarf form shocks when interacting with the dense circumstellar wind environment of the red giant companion. We find the LAT spectra from 50 MeV to ∼20–23 GeV, the highest-energy photons detected in some subintervals, are consistent with <jats:italic>π</jats:italic> <jats:sup>0</jats:sup>-decay emission from shocks in the ejecta as proposed by Tatischeff &amp; Hernanz for its previous 2006 outburst. The LAT light curve displayed a fast rise to its peak &gt;0.1 GeV flux of ≃6 × 10<jats:sup>−6</jats:sup> ph cm<jats:sup>−2</jats:sup> s<jats:sup>−1</jats:sup> beginning on day 0.745 after its optically constrained eruption epoch of 2021 August 8.50. The peak lasted for ∼1 day and exhibited a power-law decline up to the final LAT detection on day 45. We analyze the data on shorter timescales at early times and found evidence of an approximate doubling of emission over ∼200 minutes at day 2.2, possibly indicating a localized shock-acceleration event. Comparing the data collected by the American Association of Variable Star Observers, we measured a constant ratio of ∼ 2.8 × 10<jats:sup>−3</jats:sup> between the <jats:italic>γ</jats:italic>-ray and optical luminosities except for a ∼5×smaller ratio within the first day of the eruption likely indicating attenuation of <jats:italic>γ</jats:italic> rays by ejecta material and lower high-energy proton fluxes at the earliest stages of the shock development. The hard X-ray emission due to bremsstrahlung from shock-heated gas traced by the Swift-XRT 2–10 keV light curve peaked at day ∼6, later than at GeV and optical energies. Using X-ray derived temperatures to constrain the velocity profile, we find the hadronic model reproduces the observed &gt;0.1 GeV light curve.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Solar flares create adverse space weather impacting space- and Earth-based technologies. However, the difficulty of forecasting flares, and by extension severe space weather, is accentuated by the lack of any unique flare trigger or a single physical pathway. Studies indicate that multiple physical properties contribute to active region flare potential, compounding the challenge. Recent developments in machine learning (ML) have enabled analysis of higher-dimensional data leading to increasingly better flare forecasting techniques. However, consensus on high-performing flare predictors remains elusive. In the most comprehensive study to date, we conduct a comparative analysis of four popular ML techniques (<jats:italic>k</jats:italic> nearest neighbors, logistic regression, random forest classifier, and support vector machine) by training these on magnetic parameters obtained from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory for the entirety of solar cycle 24. We demonstrate that the logistic regression and support vector machine algorithms perform extremely well in forecasting active region flaring potential. The logistic regression algorithm returns the highest true skill score of 0.967 ± 0.018, possibly the highest classification performance achieved with any strictly parametric study. From a comparative assessment, we establish that magnetic properties like total current helicity, total vertical current density, total unsigned flux, <jats:italic>R</jats:italic>_VALUE, and total absolute twist are the top-performing flare indicators. We also introduce and analyze two new performance metrics, namely, severe and clear space weather indicators. Our analysis constrains the most successful ML algorithms and identifies physical parameters that contribute most to active region flare productivity.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this paper, we develop a 3D implicit single-fluid magnetohydrodynamic (MHD) model to simulate the steady-state solar corona with a wide range of Mach numbers and low plasma <jats:italic>β</jats:italic>. We employ a low-dissipation advection upstream splitting method (AUSM) to calculate the convective flux in the regions of low Mach numbers for a high resolution, and hybridize the AUSM with Harten-Lax-van Leer Riemann solver in the regions of high Mach numbers to improve the solver’s robustness. The inner boundary condition of no <jats:italic>backflow</jats:italic> is implemented by numerical flux. A reconstruction method based on the divergence-free radial basis function is adopted to enhance the divergence-free constraint of magnetic field. Also, an anisotropic thermal conduction term is considered; the positivity-preserving reconstruction method is used to prevent the presence of negative thermal pressure and plasma density, and the implicit lower-upper symmetric Gauss Seidel method is implemented for a better convergence rate. After establishing the implicit solar wind MHD model, we employ it to simulate steady-state solar coronal structures in Carrington rotations 2177 and 2212. The simulations demonstrate that the MHD model’s computational efficiency is desirable, and the modeled results are basically in agreement with the solar coronal observations and the mapped in situ measurements from the OMNI archive. Consequently, this implicit MHD model is promising to simulate a complex plasma environment with high-intensity magnetic field and wide-ranging Mach numbers.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a new methodology—the Keplerian Optical Dynamics Analysis (KODA)—for quantifying the dynamics of erupting magnetic structures in the solar corona. The technique involves adaptive spatiotemporal tracking of propagating intensity gradients and their characterization in terms of time-evolving Keplerian areas swept out by the position vectors of moving plasma blobs. Whereas gravity induces purely ballistic motions consistent with Kepler’s second law, noncentral forces such as the Lorentz force introduce nonzero torques resulting in more complex motions. KODA algorithms enable direct evaluation of the line-of-sight component of the net torque density from the image-plane projection of the areal acceleration. The method is applied to the prominence eruption of 2011 June 7, observed by the Solar Dynamics Observatory’s Atmospheric Imaging Assembly. Results obtained include quantitative estimates of the magnetic forces, field intensities, and blob masses and energies across a vast region impacted by the postreconnection redistribution of the prominence material. The magnetic pressure and energy are strongly dominant during the early, rising phase of the eruption, while the dynamic pressure and kinetic energy become significant contributors during the subsequent falling phases. Measured intensive properties of the prominence blobs are consistent with those of typical active-region prominences; measured extensive properties are compared with those of the whole pre-eruption prominence and the post-eruption coronal mass ejection of 2011 June 7, all derived by other investigators and techniques. We show that KODA provides valuable information on spatially and temporally dependent characteristics of coronal eruptions that is not readily available via alternative means, thereby shedding new light on the environment and evolution of these solar events.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Warped disk galaxies are classified into two morphologies: S and U types. Conventional theories routinely attribute both types to galactic tidal interaction and/or gas accretion, but reproducing U types in simulations is extremely challenging. Here we investigate whether both types are governed by the same mechanisms using the most extensive sample of ∼8000 nearby (0.02 &lt; <jats:italic>z</jats:italic> &lt; 0.06) massive (<jats:italic>M</jats:italic> <jats:sub>*</jats:sub>/<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> &gt; 10<jats:sup>9</jats:sup>) edge-on disks from the Sloan Digital Sky Survey. We find that U types show on average bluer optical colors and a higher specific star formation rate (sSFR) than S types, with more strongly warped U types having a higher sSFR. We also find that while the S-type warp properties correlate with the tidal force by the nearest neighbor regardless of the environment, there is no such correlation for U types in groups/clusters, suggesting a nontidal environmental could be at play for U types, such as ram pressure stripping (RPS). Indeed, U types are more common in groups/clusters than in fields and they have stellar mass, gas fraction, sSFR enhancement, and phase-space distribution closely analogous to RPS-induced jellyfish galaxies in clusters. We furthermore show that the stellar disks of most RPS galaxies in the IllustrisTNG simulation are warped in a U shape and bent in the opposite direction of stripped gas tails, satisfying theoretical expectations for stellar warps embedded in jellyfishes. We therefore suggest that despite the majority of U types that live in fields being still less explained, RPS can be an alternative origin for those in groups/clusters.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present <jats:monospace>GIGA-Lens</jats:monospace>: a gradient-informed, GPU-accelerated Bayesian framework for modeling strong gravitational lensing systems, implemented in TensorFlow and JAX. The three components, optimization using multistart gradient descent, posterior covariance estimation with variational inference, and sampling via Hamiltonian Monte Carlo, all take advantage of gradient information through automatic differentiation and massive parallelization on graphics processing units (GPUs). We test our pipeline on a large set of simulated systems and demonstrate in detail its high level of performance. The average time to model a single system on four Nvidia A100 GPUs is 105 s. The robustness, speed, and scalability offered by this framework make it possible to model the large number of strong lenses found in current surveys and present a very promising prospect for the modeling of <jats:inline-formula> <jats:tex-math> <?CDATA ${ \mathcal O }({10}^{5})$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="italic"></mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>5</mml:mn> </mml:mrow> </mml:msup> <mml:mo stretchy="false">)</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac6de4ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> lensing systems expected to be discovered in the era of the Vera C. Rubin Observatory, Euclid, and the Nancy Grace Roman Space Telescope.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We use panoramic optical spectroscopy obtained with the Very Large Telescope/MUSE to investigate the nature of five candidate extremely isolated low-mass star-forming regions (Blue Candidates; hereafter, BCs) toward the Virgo cluster of galaxies. Four of the five (BC1, BC3, BC4, and BC5) are found to host several H <jats:sc>ii </jats:sc>regions and to have radial velocities fully compatible with being part of the Virgo cluster. All the confirmed candidates have mean metallicity significantly in excess of that expected from their stellar mass, indicating that they originated from gas stripped from larger galaxies. In summary, these four candidates share the properties of the prototype system SECCO 1, suggesting the possible emergence of a new class of stellar systems, intimately linked to the complex duty cycle of gas within clusters of galaxies. A thorough discussion of the nature and evolution of these objects is presented in a companion paper, where the results obtained here from the MUSE data are complemented with Hubble Space Telescope (optical) and Very Large Array (H<jats:sc>i</jats:sc>) observations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We discuss five blue stellar systems in the direction of the Virgo cluster, analogous to the enigmatic object SECCO 1 (AGC 226067). These objects were identified based on their optical and UV morphology and followed up with H <jats:sc>i</jats:sc> observations with the Very Large Array (and Green Bank Telescope), Multi Unit Spectroscopic Explorer (on the Very Large Telescope) optical spectroscopy, and Hubble Space Telescope imaging. These new data indicate that one system is a distant group of galaxies. The remaining four are extremely low mass (<jats:italic>M</jats:italic> <jats:sub>*</jats:sub> ∼ 10<jats:sup>5</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>), are dominated by young blue stars, have highly irregular and clumpy morphologies, are only a few kiloparsecs across, yet host an abundance of metal-rich, <jats:inline-formula> <jats:tex-math> <?CDATA $12+\mathrm{log}({\rm{O}}/{\rm{H}})\gt 8.2$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>12</mml:mn> <mml:mo>+</mml:mo> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mi mathvariant="normal">O</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> <mml:mo stretchy="false">)</mml:mo> <mml:mo>&gt;</mml:mo> <mml:mn>8.2</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac7c6cieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, H <jats:sc>ii</jats:sc> regions. These high metallicities indicate that these stellar systems formed from gas stripped from much more massive galaxies. Despite the young age of their stellar populations, only one system is detected in H <jats:sc>i</jats:sc>, while the remaining three have minimal (if any) gas reservoirs. Furthermore, two systems are surprisingly isolated and have no plausible parent galaxy within ∼30′ (∼140 kpc). Although tidal stripping cannot be conclusively excluded as the formation mechanism of these objects, ram pressure stripping more naturally explains their properties, in particular their isolation, owing to the higher velocities, relative to the parent system, that can be achieved. Therefore, we posit that most of these systems formed from ram-pressure-stripped gas removed from new infalling cluster members and survived in the intracluster medium long enough to become separated from their parent galaxies by hundreds of kiloparsecs and that they thus represent a new type of stellar system.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Recent evidence suggests that high-redshift Ly<jats:italic>α</jats:italic> emitting galaxies (LAEs) with <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}L(\mathrm{Ly}\alpha )\gt 43.5\,\mathrm{erg}\ {{\rm{s}}}^{-1}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mi>L</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mi>Ly</mml:mi> <mml:mi>α</mml:mi> <mml:mo stretchy="false">)</mml:mo> <mml:mo>&gt;</mml:mo> <mml:mn>43.5</mml:mn> <mml:mspace width="0.50em" /> <mml:mi>erg</mml:mi> <mml:mspace width="0.33em" /> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">s</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac8051ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, referred to as ultraluminous LAEs (ULLAEs), may show less evolution than lower-luminosity LAEs in the redshift range <jats:italic>z</jats:italic> = 5.7–6.6. Here we explore the redshift evolution of the velocity widths of the Ly<jats:italic>α</jats:italic> emission lines in LAEs over this redshift interval. We use new wide-field, narrowband observations from Subaru/Hyper Suprime-Cam to provide a sample of 24 <jats:italic>z</jats:italic> = 6.6 and 12 <jats:italic>z</jats:italic> = 5.7 LAEs with <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}L(\mathrm{Ly}\alpha )\gt 43\,\mathrm{erg}\ {{\rm{s}}}^{-1}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mi>L</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mi>Ly</mml:mi> <mml:mi>α</mml:mi> <mml:mo stretchy="false">)</mml:mo> <mml:mo>&gt;</mml:mo> <mml:mn>43</mml:mn> <mml:mspace width="0.50em" /> <mml:mi>erg</mml:mi> <mml:mspace width="0.33em" /> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">s</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac8051ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>, all of which have follow-up spectroscopy from Keck/DEIMOS. Combining with archival lower-luminosity data, we find a significant narrowing of the Ly<jats:italic>α</jats:italic> lines in LAEs at <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}L(\mathrm{Ly}\alpha )\lt 43.25\,\mathrm{erg}\ {{\rm{s}}}^{-1}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mi>L</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mi>Ly</mml:mi> <mml:mi>α</mml:mi> <mml:mo stretchy="false">)</mml:mo> <mml:mo>&lt;</mml:mo> <mml:mn>43.25</mml:mn> <mml:mspace width="0.50em" /> <mml:mi>erg</mml:mi> <mml:mspace width="0.33em" /> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">s</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac8051ieqn3.gif" xlink:type="simple" /> </jats:inline-formula>—somewhat lower than the usual ULLAE definition—at <jats:italic>z</jats:italic> = 6.6 relative to those at <jats:italic>z</jats:italic> = 5.7, but we do not see this in higher-luminosity LAEs. As we move to higher redshifts, the increasing neutrality of the intergalactic medium should increase the scattering of the Ly<jats:italic>α</jats:italic> lines, making them narrower. The absence of this effect in the higher-luminosity LAEs suggests they may lie in more highly ionized regions, self-shielding from the scattering effects of the intergalactic medium.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>To understand the impact of radiation feedback during the formation of a globular cluster (GC), we simulate a head-on collision of two turbulent giant molecular clouds (GMCs). A series of idealized radiation-hydrodynamic simulations is performed, with and without stellar radiation or Type II supernovae. We find that a gravitationally bound, compact star cluster of mass <jats:italic>M</jats:italic> <jats:sub>GC</jats:sub> ∼ 10<jats:sup>5</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> forms within ≈3 Myr when two GMCs with mass <jats:italic>M</jats:italic> <jats:sub>GMC</jats:sub> = 3.6 × 10<jats:sup>5</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> collide. The GC candidate does not form during a single collapsing event but emerges due to the mergers of local dense gas clumps and gas accretion. The momentum transfer due to the absorption of the ionizing radiation is the dominant feedback process that suppresses the gas collapse, and photoionization becomes efficient once a sufficient number of stars form. The cluster mass is larger by a factor of ∼2 when the radiation feedback is neglected, and the difference is slightly more pronounced (16%) when extreme Ly<jats:italic>α</jats:italic> feedback is considered in the fiducial run. In the simulations with radiation feedback, supernovae explode after the star-forming clouds are dispersed, and their metal ejecta are not instantaneously recycled to form stars.</jats:p>