Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We present ALMA observations of 101 protoplanetary disks within the star-forming region Lynds 1641 in the Orion Molecular Cloud A. Our observations include 1.33 mm continuum emission and spectral windows covering the <jats:italic>J</jats:italic> = 2–1 transition of <jats:sup>12</jats:sup>CO, <jats:sup>13</jats:sup>CO, and C<jats:sup>18</jats:sup>O. We detect 89 protoplanetary disks in the dust continuum at the 4<jats:italic>σ</jats:italic> level (∼88% detection rate) and 31 in <jats:sup>12</jats:sup>CO, 13 in <jats:sup>13</jats:sup>CO, and 4 in C<jats:sup>18</jats:sup>O. Our sample contains 23 transitional disks, 20 of which are detected in the continuum. We target infrared-bright Class II objects, which biases our sample toward massive disks. We determine dust masses or upper limits for all sources in our sample and compare our sample to protostars in this region. We find a decrease in dust mass with evolutionary state. We also compare this sample to other regions surveyed in the (sub)millimeter and find that Lynds 1641 has a relatively massive dust disk population compared to regions of similar and older ages, with a median dust mass of <jats:inline-formula> <jats:tex-math> <?CDATA ${11.1}_{-4.6}^{+32.9}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabf432ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> <jats:italic>M</jats:italic> <jats:sub>⊕</jats:sub> and 27% with dust masses equal to or greater than the minimum solar nebula dust mass value of ∼30 <jats:italic>M</jats:italic> <jats:sub>⊕</jats:sub>. We analyze the disk mass–accretion rate relationship in this sample and find that the viscous disk lifetimes are similar to the age of the region, though with a large spread. One object, [MGM2012] 512, shows a large-scale (&gt;5000 au) structure in both the dust continuum and the three gas lines. We discuss potential origins for this emission, including an accretion streamer with large dust grains.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Two new schemes for identifying field lines involved in eruptions, the <jats:italic>r</jats:italic>-scheme and <jats:italic>q</jats:italic>-scheme, are proposed to analyze the eruptive and confined nature of solar flares, as extensions to the original <jats:italic>r</jats:italic> <jats:sub> <jats:italic>m</jats:italic> </jats:sub> scheme proposed in Lin et al. Motivated by three solar flares originating from NOAA Active Region 12192 that are misclassified by <jats:italic>r</jats:italic> <jats:sub> <jats:italic>m</jats:italic> </jats:sub>, we introduce refinements to the <jats:italic>r</jats:italic>-scheme employing the “magnetic twist flux” to approximate the force balance acting on a magnetic flux rope (MFR); in the <jats:italic>q</jats:italic>-scheme, the reconnected field is represented by those field lines that anchor in the flare ribbons. Based on data obtained by the Solar Dynamics Observatory/Helioseismic and Magnetic Imager, the coronal magnetic field for 51 flares larger than M5.0 class, from 29 distinct active regions, is constructed using a nonlinear force-free field extrapolation model. Statistical analysis based on linear discriminant function analysis is then performed, revealing that despite both schemes providing moderately successful classifications for the 51 flares, the coronal mass ejection-eruptivity classification for the three target events can only be improved with the <jats:italic>q</jats:italic>-scheme. We find that the highly twisted field lines and the flare-ribbon field lines have equal average force-free constant <jats:italic>α</jats:italic>, but all of the flare-ribbon-related field lines are shorter than 150 Mm in length. The findings lead us to conclude that it is challenging to distinguish the MFR from the ambient magnetic field using any quantity based on common magnetic nonpotentiality measures.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Studying the resolved stellar populations of the different structural components that build massive galaxies directly unveils their assembly history. We aim at characterizing the stellar population properties of a representative sample of bulges and pure spheroids in massive galaxies (<jats:italic>M</jats:italic> <jats:sub>⋆</jats:sub> &gt; 10<jats:sup>10</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) in the GOODS-N field. We take advantage of the spectral and spatial information provided by SHARDS and Hubble Space Telescope data to perform the multi-image spectrophotometric decoupling of the galaxy light. We derive the spectral energy distribution separately for bulges and disks in the redshift range 0.14 &lt; <jats:italic>z</jats:italic> ≤ 1 with spectral resolution <jats:italic>R</jats:italic> ∼ 50. Analyzing these spectral energy distributions, we find evidence of a bimodal distribution of bulge formation redshifts. We find that 33% of them present old mass-weighted ages, implying a median formation redshift <jats:inline-formula> <jats:tex-math> <?CDATA ${z}_{\mathrm{form}}={6.2}_{-1.7}^{+1.5}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabef72ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>. They are relics of the early universe embedded in disk galaxies. A second wave, dominant in number, accounts for bulges formed at median redshift <jats:inline-formula> <jats:tex-math> <?CDATA ${z}_{\mathrm{form}}={1.3}_{-0.6}^{+0.6}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabef72ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>. The oldest (first-wave) bulges are more compact than the youngest. Virtually all pure spheroids (i.e., those without any disk) are coetaneous with the second-wave bulges, presenting a median redshift of formation <jats:inline-formula> <jats:tex-math> <?CDATA ${z}_{\mathrm{form}}={1.1}_{-0.3}^{+0.3}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabef72ieqn3.gif" xlink:type="simple" /> </jats:inline-formula>. The two waves of bulge formation are distinguishable not only in terms of stellar ages but also in star formation mode. All first-wave bulges formed fast at <jats:italic>z</jats:italic> ∼ 6, with typical timescales around 200 Myr. A significant fraction of the second-wave bulges assembled more slowly, with star formation timescales as long as 1 Gyr. The results of this work suggest that the centers of massive disk-like galaxies actually harbor the oldest spheroids formed in the universe.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The seven planets orbiting TRAPPIST-1 in a compact near-resonant chain offer a unique case to study in planet formation theory. We demonstrate in this paper that the remarkable flatness of the system, exceeding that of any other known planetary system, is an important constraint on the mass of the gaseous disk in which it formed and attained its current configuration. We use three-dimensional hydrodynamic simulations of the gas and planets to study specific formation models. In particular, we report simulations motivated by the model proposed by Ormel et al.—in this model, the dispersal of the gas disk pushes the planets from an initial resonant chain into their present configuration. We find that a disk with the mass used in this model is consistent with the flatness of the TRAPPIST-1 system, but a more massive disk is not, with the transition occurring between 15 and 50 times the mass of the Ormel et al. disk. This upper limit on mass rules out certain models of the formation of the system, namely in situ formation and disk migration on long timescales.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>With the onset of solar maximum and the expected increased prevalence of interplanetary shock waves, Parker Solar Probe is likely to observe numerous shocks in the next few years. An outstanding question that has received surprisingly little attention has been how turbulence interacts with collisionless shock waves. Turbulence in the supersonic solar wind is described frequently as a superposition of a majority 2D and a minority slab component. We formulate a collisional perpendicular shock-turbulence transmission problem in a way that enables investigation of the interaction and transmission of quasi-perpendicular fluctuations such as magnetic flux ropes/islands and vortices as well as entropy and acoustic modes in the large plasma beta regime. We focus on the transmission of an upstream spectrum of these modes, finding that the downstream spectral amplitude is typically increased significantly (a factor of 10 or more), and that the upstream spectral index of the inertial range, and indeed the general spectral shape, is unchanged for the downstream magnetic variance, kinetic energy, and density variance. A comparison of the theoretically predicted downstream magnetic variance, kinetic energy, and density variance spectra with those observed at 1, 5, and 84 au by Wind, Ulysses, and Voyager 2 shows excellent agreement. The overall theoretically predicted characteristics of the transmission of turbulence across shocks observed in the solar wind appear to be largely consistent with recent observational studies by Pitňa et al. and Borovsky.</jats:p>