Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We present a framework for characterizing the spatiotemporal power spectrum of the variability expected from the horizon-scale emission structure around supermassive black holes, and we apply this framework to a library of general relativistic magnetohydrodynamic (GRMHD) simulations and associated general relativistic ray-traced images relevant for Event Horizon Telescope (EHT) observations of Sgr A*. We find that the variability power spectrum is generically a red-noise process in both the temporal and spatial dimensions, with the peak in power occurring on the longest timescales and largest spatial scales. When both the time-averaged source structure and the spatially integrated light-curve variability are removed, the residual power spectrum exhibits a universal broken power-law behavior. On small spatial frequencies, the residual power spectrum rises as the square of the spatial frequency and is proportional to the variance in the centroid of emission. Beyond some peak in variability power, the residual power spectrum falls as that of the time-averaged source structure, which is similar across simulations; this behavior can be naturally explained if the variability arises from a multiplicative random field that has a steeper high-frequency power-law index than that of the time-averaged source structure. We briefly explore the ability of power spectral variability studies to constrain physical parameters relevant for the GRMHD simulations, which can be scaled to provide predictions for black holes in a range of systems in the optically thin regime. We present specific expectations for the behavior of the M87* and Sgr A* accretion flows as observed by the EHT.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The extraordinary physical resolution afforded by the Event Horizon Telescope has opened a window onto the astrophysical phenomena unfolding on horizon scales in two known black holes, M87<jats:italic>*</jats:italic> and Sgr A*. However, with this leap in resolution has come a new set of practical complications. Sgr A* exhibits intraday variability that violates the assumptions underlying Earth aperture synthesis, limiting traditional image reconstruction methods to short timescales and data sets with very sparse (<jats:italic>u</jats:italic>, <jats:italic>v</jats:italic>) coverage. We present a new set of tools to detect and mitigate this variability. We develop a data-driven, model-agnostic procedure to detect and characterize the spatial structure of intraday variability. This method is calibrated against a large set of mock data sets, producing an empirical estimator of the spatial power spectrum of the brightness fluctuations. We present a novel Bayesian noise modeling algorithm that simultaneously reconstructs an average image and statistical measure of the fluctuations about it using a parameterized form for the excess variance in the complex visibilities not otherwise explained by the statistical errors. These methods are validated using a variety of simulated data, including general relativistic magnetohydrodynamic simulations appropriate for Sgr A* and M87<jats:italic>*</jats:italic>. We find that the reconstructed source structure and variability are robust to changes in the underlying image model. We apply these methods to the 2017 EHT observations of M87<jats:italic>*</jats:italic>, finding evidence for variability across the EHT observing campaign. The variability mitigation strategies presented are widely applicable to very long baseline interferometry observations of variable sources generally, for which they provide a data-informed averaging procedure and natural characterization of inter-epoch image consistency.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The new Gaia data release (EDR3) with improved astrometry has opened a new era in studying our Milky Way in fine detail. We use Gaia EDR3 astrometry together with 2MASS and WISE photometry to study two of the most massive molecular clouds in the solar vicinity: Orion A and California. Despite having remarkable similarities in the plane of the sky in terms of shape, size, and extinction, California has an order of magnitude lower star formation efficiency. We use our state-of-the-art dust mapping technique to derive the detailed three-dimensional (3D) structure of the two clouds, taking into account both distance and extinction uncertainties, and a full 3D spatial correlation between neighboring points. We discover that, despite the apparent filamentary structure in the plane of the sky, California is a flat 120 pc-long sheet extending from 410 to 530 pc. We show that not only Orion A and California differ substantially in their 3D shapes, but also Orion A has considerably higher density substructures in 3D than California. This result presents a compelling reason why the two clouds have different star formation activities. We also demonstrate how the viewing angle of California can substantially change the cloud’s position in the Kennicutt–Schmidt relation. This underlines the importance of 3D information in interpreting star formation relations and challenges studies that rely solely on the column density thresholds to determine star formation activities in molecular clouds. Finally, we provide accurate distance estimates to multiple lines of sight toward various parts of the two clouds.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A dearth of close-in planets orbiting rapid rotators was reported almost a decade ago. According to this view, only slowly spinning stars with rotation periods longer than 5–10 days would host planets with orbital periods shorter than 2 or 3 days. This Letter brings an enlarged and more detailed analysis that led us to the question: Is there really a dearth in that distribution or is it a dearth of data? For this new analysis, we combined different samples of Kepler and TESS stars with confirmed planets or planet candidates with measured stellar rotation periods, using Gaia data to perform an in-depth selection of 1013 planet-hosting main-sequence stars. With the newer, enlarged, and more refined data, the reported dearth of close-in planets orbiting rapid rotators tends to disappear, thus suggesting that it may reflect a scarcity of data in the prior analysis. A two-sample statistical test strongly supports our results, showing that the distribution of close-in planets orbiting rapid rotators is almost indistinguishable from that for close-in planets orbiting slow rotators.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report the first-time recovery of a fresh meteorite fall using a drone and a machine-learning algorithm. The fireball was observed on 2021 April 1 over Western Australia by the Desert Fireball Network, for which a fall area was calculated for the predicted surviving mass. A search team arrived on-site and surveyed 5.1 km<jats:sup>2</jats:sup> area over a 4 day period. A convolutional neural network, trained on previously recovered meteorites with fusion crusts, processed the images on our field computer after each flight. Meteorite candidates identified by the algorithm were sorted by team members using two user interfaces to eliminate false positives. Surviving candidates were revisited with a smaller drone, and imaged in higher resolution, before being eliminated or finally being visited in person. The 70 g meteorite was recovered within 50 m of the calculated fall line, demonstrating the effectiveness of this methodology, which will facilitate the efficient collection of many more observed meteorite falls.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Mid-infrared spectroscopy is one of the few ways to observe the composition of the terrestrial planet-forming zone, the inner few astronomical units, of protoplanetary disks. The species currently detected in the disk atmosphere, for example, CO, CO<jats:sub>2</jats:sub>, H<jats:sub>2</jats:sub>O, and C<jats:sub>2</jats:sub>H<jats:sub>2</jats:sub>, are theoretically enough to constrain the C/O ratio on the disk surface. However, thermochemical models have difficulties in reproducing the full array of detected species in the mid-infrared simultaneously. In an effort to get closer to the observed spectra, we have included water UV-shielding as well as more efficient chemical heating into the thermochemical code Dust and Lines. We find that both are required to match the observed emission spectrum. Efficient chemical heating, in addition to traditional heating from UV photons, is necessary to elevate the temperature of the water-emitting layer to match the observed excitation temperature of water. We find that water UV-shielding stops UV photons from reaching deep into the disk, cooling down the lower layers with a higher column. These two effects create a hot emitting layer of water with a column of 1–10 × 10<jats:sup>18</jats:sup> cm<jats:sup>−2</jats:sup>. This is only 1%–10% of the water column above the dust <jats:italic>τ</jats:italic> = 1 surface at mid-infrared wavelengths in the models and represents &lt;1% of the total water column.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Making precise measurements of pulsar dispersion measures (DMs) and applying suitable corrections for them is among the major challenges in high-precision timing programs such as pulsar timing arrays (PTAs). While the advent of wideband pulsar instrumentation can enable more precise DM measurements and thence improved timing precision, it also necessitates doing careful assessments of frequency-dependent (chromatic) DMs that were theorized by Cordes et al (2016). Here we report the detection of such an effect in broadband observations of the millisecond pulsar PSR J2241−5236, a high-priority target for current and future PTAs. The observations were made contemporaneously using the wideband receivers and capabilities now available at the Murchison Widefield Array, the upgraded Giant Metrewave Radio Telescope, and the Parkes telescopes, thus providing an unprecedentedly large frequency coverage from 80 MHz to 4 GHz. Our analysis shows the measurable changes in DM that scale with the observing frequency (<jats:italic>ν</jats:italic>) as <jats:italic>δ</jats:italic>DM ∝ <jats:italic>ν</jats:italic> <jats:sup>2.5±0.1</jats:sup>. We discuss the potential implications of such a frequency dependence in the measured DMs and the likely impact on the timing noise budget and comment on the usefulness of low-frequency observations in advancing PTA efforts.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Complex organic molecules (COMs) can be produced efficiently in ice mixtures that simulate the ice mantle on cosmic dust grains, according to prior experimental studies. However, the mechanism that brings the reactive species together in the ice has been debated. Thermal diffusion, which is widely regarded as the main mechanism to bring reactants together, is inefficient at a typical dense cloud temperature of 10 K. A recent experimental study found that the transition of a thin CO ice film from the amorphous to crystalline phase happens at about 10 K. When a small fraction of CO<jats:sub>2</jats:sub> was mixed with CO, the CO<jats:sub>2</jats:sub> molecules can separate and form clusters during CO phase transition. It was further proposed that the separation of minor species in the CO ice during phase transition may be an important mechanism to form interstellar COMs without the need for thermal diffusion. In this study, we try to verify this new mechanism through laboratory experiments. An ice mixture of CH<jats:sub>3</jats:sub>OH and CO, which is an analog of the outer layer of the ice mantle on cosmic dust grains, was exposed to UV irradiation to produce radicals such as HCO and CH<jats:sub>2</jats:sub>OH, whose concentration was monitored during the subsequent warm-up of the ice. We find clear evidence that during the CO phase transition, most of the radicals recombine to form other molecular species, therefore supporting the recently proposed mechanism of COM formation via CO phase transition.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a phenomenological and numerical study of strong Alfvénic turbulence in a magnetically dominated collisionless relativistic plasma with a strong background magnetic field. In contrast with the nonrelativistic case, the energy in such turbulence is contained in magnetic and electric fluctuations. We argue that such turbulence is analogous to turbulence in a strongly magnetized nonrelativistic plasma in the regime of broken quasi-neutrality. Our 2D particle-in-cell numerical simulations of turbulence in a relativistic pair plasma find that the spectrum of the total energy has the scaling <jats:italic>k</jats:italic> <jats:sup>−3/2</jats:sup>, while the difference between the magnetic and electric energies, the so-called residual energy, has the scaling <jats:italic>k</jats:italic> <jats:sup>−2.4</jats:sup>. The electric and magnetic fluctuations at scale <jats:italic>ℓ</jats:italic> exhibit dynamic alignment with the alignment angle scaling close to <jats:inline-formula> <jats:tex-math> <?CDATA $\cos {\phi }_{{\ell }}\propto {{\ell }}^{1/4}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>cos</mml:mi> <mml:msub> <mml:mrow> <mml:mi>ϕ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="italic">ℓ</mml:mi> </mml:mrow> </mml:msub> <mml:mo>∝</mml:mo> <mml:msup> <mml:mrow> <mml:mi mathvariant="italic">ℓ</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>1</mml:mn> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mn>4</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac6cdeieqn1.gif" xlink:type="simple" /> </jats:inline-formula>. At scales smaller than the (relativistic) plasma inertial scale, the energy spectrum of relativistic inertial Alfvén turbulence steepens to <jats:italic>k</jats:italic> <jats:sup>−3.5</jats:sup>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The correlation between the mass of supermassive black holes (SMBHs; <jats:inline-formula> <jats:tex-math> <?CDATA ${{ \mathcal M }}_{\mathrm{BH}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="italic"></mml:mi> </mml:mrow> <mml:mrow> <mml:mi>BH</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac6de8ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>) and their host galaxies (<jats:inline-formula> <jats:tex-math> <?CDATA ${{ \mathcal M }}_{\star }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="italic"></mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⋆</mml:mo> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac6de8ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>) in the reionization epoch provides valuable constraints on their early growth. High-redshift quasars typically have an <jats:inline-formula> <jats:tex-math> <?CDATA ${{ \mathcal M }}_{\mathrm{BH}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="italic"></mml:mi> </mml:mrow> <mml:mrow> <mml:mi>BH</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac6de8ieqn3.gif" xlink:type="simple" /> </jats:inline-formula>/<jats:inline-formula> <jats:tex-math> <?CDATA ${{ \mathcal M }}_{\star }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="italic"></mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⋆</mml:mo> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac6de8ieqn4.gif" xlink:type="simple" /> </jats:inline-formula> ratio significantly elevated in comparison to the local value. However, the degree to which this apparent offset is driven by observational biases is unclear for the most distant quasars. To address this issue, we model the sample selection and measurement biases for a compilation of 20 quasars at <jats:italic>z</jats:italic> ∼ 6 with host properties based on ALMA observations. We find that the observed distribution of quasars in the <jats:inline-formula> <jats:tex-math> <?CDATA ${{ \mathcal M }}_{\mathrm{BH}}\mbox{--}{{ \mathcal M }}_{\star }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="italic"></mml:mi> </mml:mrow> <mml:mrow> <mml:mi>BH</mml:mi> </mml:mrow> </mml:msub> <mml:mo>–</mml:mo> <mml:msub> <mml:mrow> <mml:mi mathvariant="italic"></mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⋆</mml:mo> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac6de8ieqn5.gif" xlink:type="simple" /> </jats:inline-formula> plane can be reproduced by assuming that the underlying SMBH population at <jats:italic>z</jats:italic> ∼ 6 follows the relationship in the local universe. However, a positive or even a negative evolution in <jats:inline-formula> <jats:tex-math> <?CDATA ${{ \mathcal M }}_{\mathrm{BH}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="italic"></mml:mi> </mml:mrow> <mml:mrow> <mml:mi>BH</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac6de8ieqn6.gif" xlink:type="simple" /> </jats:inline-formula>/<jats:inline-formula> <jats:tex-math> <?CDATA ${{ \mathcal M }}_{\star }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="italic"></mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⋆</mml:mo> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac6de8ieqn7.gif" xlink:type="simple" /> </jats:inline-formula> can also explain the data, depending on whether the intrinsic scatter evolves and on the strength of various systematic uncertainties. To break these degeneracies, an improvement in the accuracy of mass measurements and an expansion of the current sample to lower <jats:inline-formula> <jats:tex-math> <?CDATA ${{ \mathcal M }}_{\mathrm{BH}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="italic"></mml:mi> </mml:mrow> <mml:mrow> <mml:mi>BH</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac6de8ieqn8.gif" xlink:type="simple" /> </jats:inline-formula> limits are needed. Furthermore, assuming a radiative efficiency of 0.1 and quasar duty cycles estimated from the active SMBH fraction, significant outliers in <jats:inline-formula> <jats:tex-math> <?CDATA ${{ \mathcal M }}_{\mathrm{BH}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="italic"></mml:mi> </mml:mrow> <mml:mrow> <mml:mi>BH</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac6de8ieqn9.gif" xlink:type="simple" /> </jats:inline-formula>/<jats:inline-formula> <jats:tex-math> <?CDATA ${{ \mathcal M }}_{\star }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="italic"></mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⋆</mml:mo> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac6de8ieqn10.gif" xlink:type="simple" /> </jats:inline-formula> tend to move toward the local relation given their instantaneous BH growth rate and star formation rate. This may provide evidence for a self-regulated SMBH–galaxy coevolution scenario that is in place at <jats:italic>z</jats:italic> ∼ 6, with active galactic nucleus feedback being a possible driver.</jats:p>