Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>The increasing number of super-Earths close to their host stars have revealed a scarcity of close-in small planets with 1.5–2.0 <jats:italic>R</jats:italic> <jats:sub>⊕</jats:sub> in the radius distribution of Kepler planets. The atmospheric escape of super-Earths by photoevaporation can explain the origin of the observed “radius gap.” Many theoretical studies have considered the in situ mass loss of a close-in planet. Planets that undergo atmospheric escape, however, move outward due to the change in the orbital angular momentum of their star–planet systems. In this study, we calculate the orbital evolution of an evaporating super-Earth with a H<jats:sub>2</jats:sub>/He atmosphere around FGKM-type stars under stellar X-ray and extreme-UV irradiation (XUV). The rate of increase in the orbital radius of an evaporating planet is approximately proportional to that of the atmospheric mass loss during a high stellar XUV phase. We show that super-Earths with a rocky core of ≲10 <jats:italic>M</jats:italic> <jats:sub>⊕</jats:sub> and a H<jats:sub>2</jats:sub>/He atmosphere at ≲0.03–0.1 au (≲0.01–0.03 au) around G-type stars (M-type stars) are prone to outward migration driven by photoevaporation. Although the changes in the orbits of the planets would be small, they would rearrange the orbital configurations of compact, multiplanet systems, such as the TRAPPIST-1 system. We also find that the radius gap and the so-called “Neptune desert” in the observed population of close-in planets around FGK-type stars still appear in our simulations. On the other hand, the observed planet population around M-type stars can be reproduced only by a high stellar XUV luminosity model.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Due to the lack of a global magnetic field, the charge exchange process between the solar wind protons and Martian hydrogen corona is of critical importance to Mars’ atmosphere. The energetic neutral atoms and pickup H<jats:sup>+</jats:sup> produced during this process can further excite proton aurorae and proton cyclotron waves (PCWs) in the near-Mars space, for which the observational evidence however remains very limited. Here we report a particular event to show that the PCWs and proton aurorae were simultaneously recorded by the Mars Atmosphere and Volatile EvolutioN spacecraft during 10 consecutive orbits. As the byproducts of the charge exchange process, these two phenomena are found to be highly correlated in both space and time, with the correlation coefficient &gt;0.7 between the auroral emissions and PCW amplitudes. Moreover, the wave and ultraviolet measurements show clearly that both the PCWs and proton aurora events tend to occur more frequently and intensively within the stream interaction region, as being strongly modulated by the solar wind activity. Our results indicate that the solar wind can directly transport energy and particles into the near-Mars environment, leading to the simultaneous enhancements of plasma wave activity and proton precipitation, which therefore helps comprehend the significant role of the solar wind activity and charge exchange process in driving the energy budget to the Martian upper atmosphere.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present results from <jats:sc>GigaEris</jats:sc>, a cosmological, <jats:italic>N</jats:italic>-body hydrodynamical “zoom-in” simulation of the formation of a Milky Way-sized galaxy halo with unprecedented resolution, encompassing of order a billion particles within the refined region. The simulation employs a modern implementation of smoothed-particle hydrodynamics, including metal-line cooling and metal and thermal diffusion. We focus on the early assembly of the galaxy, down to redshift <jats:italic>z</jats:italic> = 4.4. The simulated galaxy has properties consistent with extrapolations of the main sequence of star-forming galaxies to higher redshifts and levels off to a star formation rate of ∼60 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup> at <jats:italic>z</jats:italic> = 4.4. A compact, thin rotating stellar disk with properties analogous to those of low-redshift systems arises already at <jats:italic>z</jats:italic> ∼ 8. The galaxy rapidly develops a multi-component structure, and the disk, at least at these early stages, does not grow “upside-down” as often reported in the literature. Rather, at any given time, newly born stars contribute to sustain a thin disk. The kinematics reflect the early, ubiquitous presence of a thin disk, as a stellar disk component with <jats:italic>v</jats:italic> <jats:sub> <jats:italic>ϕ</jats:italic> </jats:sub>/<jats:italic>σ</jats:italic> <jats:sub> <jats:italic>R</jats:italic> </jats:sub> larger than unity is already present at <jats:italic>z</jats:italic> ∼ 9–10. Our results suggest that high-resolution spectro-photometric observations of very high-redshift galaxies should find thin rotating disks, consistent with the recent discovery of cold rotating gas disks by ALMA. Finally, we present synthetic images for the James Webb Space Telescope NIRCam camera, showing how the early disk would be easily detectable already at those early times.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A new nonthermal phenomenon caused by streaming cosmic rays (CRs) in the universe is proposed. The streaming CRs drive the return current of thermal electrons to compensate for the CR current. Then, electric fields are induced by the resistivity of the return current. It is shown that the resistive electric fields can accelerate secondary electrons generated by the streaming CRs. This is the self-discharge by streaming CRs. In this work, the self-discharge condition and the condition for runaway acceleration of secondary electrons are presented. The self-discharge creates high-energy secondary electrons, resulting in enhancements of ionization and nonthermal emission including the K<jats:italic>α</jats:italic> emission line of neutral iron. After the self-discharge, the return current of thermal electrons is replaced by the electric current of secondary electrons. Since some generation and amplification of magnetic fields are driven by the return current of thermal electrons, the self-discharge can significantly influence them.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Investigation of the properties of photospheric magnetic fields could shed light on the generation mechanism of small-scale magnetic fields in quiet regions. In this work, we studied the transversal magnetic fields by analyzing the linear polarization (LP) features with Sunrise IMaX data. We calculated the area coverage of LP features, and found that they are 16.1%, 8.6%, and 3% for signals above 3, 3.5, and 4.5 times of noise level, respectively. Those LP features extracted above 4.5 times of noise level are further analyzed. A proper value of 1.5 × 10<jats:sup>15</jats:sup> Mx for the net magnetic flux contained in LP features is selected to divide the LP features into two types (I and II). Among all detected snapshot LP features, 86% of them are in type I and the rest are in type II. The length scales of LP features in these two types follow Gauss and power-law distributions, separately. For the topology of magnetic fields in type I, the magnetic flux patches might be footpoints of flux loops that root inside transversal magnetic fields with one unipolar thick leg or one thick leg together with one thin leg in opposite polarity. For those in type II, about 50% of them contain bipolar magnetic flux patches, but the rest appear without magnetic flux patches.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We measured the nickel isotope composition of troilites from chondritic meteorites using the NanoSIMS to put constraints on the abundance of iron-60 in the early solar system. The troilites were selected from petrologic type 3 ordinary and carbonaceous chondrites. Based on petrographic observations and mineral chemistry, the troilites targeted for isotope analysis crystallized from melts, most likely in a nebular setting. Our isotope analyses did not reveal any significant correlation between nickel-60 enrichments and Fe/Ni ratios, either in the entire set of troilite grains or in individual troilites. The average inferred initial <jats:sup>60</jats:sup>Fe/<jats:sup>56</jats:sup>Fe ratio of the studied troilites (i.e., the <jats:sup>60</jats:sup>Fe/<jats:sup>56</jats:sup>Fe ratio calculated for the entire troilite population) is 1.05 (±1.48) ×10<jats:sup>−8</jats:sup>. This value is very similar to those estimated in the past for Semarkona chondrules, angrites, as well as diogenites and eucrites, based on the isotope analyses of bulk samples (10<jats:sup>−9</jats:sup>–10<jats:sup>−8</jats:sup>), but about two orders of magnitude smaller than the average initial <jats:sup>60</jats:sup>Fe/<jats:sup>56</jats:sup>Fe ratios inferred previously for Semarkona troilites and many chondrules from ordinary and carbonaceous chondrites (10<jats:sup>−7</jats:sup>–10<jats:sup>−6</jats:sup>) using in situ analysis techniques. Based on petrographic evidence, and the generally unequilibrated nature of our samples, as well as on the timing of chondrule formation and planetary evolution, the lack of discernible signs of in situ iron-60 decay in the studied troilites is probably unrelated to metamorphic re-equilibration, and it is also not the result of a late formation of the troilites. We suggest that the highest inferred initial <jats:sup>60</jats:sup>Fe/<jats:sup>56</jats:sup>Fe ratios reported in the literature are probably inaccurate.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present measurements of the Minkowski functionals extracted from the SDSS-III BOSS catalogs. After defining the Minkowski functionals, we describe how an unbiased reconstruction of these statistics can be obtained from a field with masked regions and survey boundaries, validating our methodology with Gaussian random fields and mock galaxy snapshot data. From the BOSS galaxy data, we generate a set of four density fields in three dimensions corresponding to the northern and southern skies of LOWZ and CMASS catalogs, smoothing over large scales (Gaussian smoothing scale of 35 Mpc) such that the field is perturbatively non-Gaussian. We extract the Minkowski functionals from each data set separately, and measure their shapes and amplitudes by fitting a Hermite polynomial expansion. For the shape parameter of the Minkowski functional curves <jats:italic>a</jats:italic> <jats:sub>0</jats:sub>, that is related to the bispectrum of the field, we find that the LOWZ-South data presents a systematically lower value of <jats:italic>a</jats:italic> <jats:sub>0</jats:sub> = −0.080 ± 0.040 than its northern sky counterpart <jats:italic>a</jats:italic> <jats:sub>0</jats:sub> = 0.032 ± 0.024. Although the significance of this discrepancy is not very high, it potentially indicates some systematics in the data or that the matter density field exhibits anisotropy at low redshift. By assuming a standard isotropic flat ΛCDM cosmology, the amplitudes of the Minkowski functionals from the combination of northern and southern sky data give the constraints Ω<jats:sub>c</jats:sub> <jats:italic>h</jats:italic> <jats:sup>2</jats:sup> <jats:italic>n</jats:italic> <jats:sub>s</jats:sub> = 0.110 ± 0.006 and 0.111 ± 0.008 for CMASS and LOWZ, respectively, which is in agreement with the Planck ΛCDM best-fit Ω<jats:sub>c</jats:sub> <jats:italic>h</jats:italic> <jats:sup>2</jats:sup> <jats:italic>n</jats:italic> <jats:sub>s</jats:sub> = 0.116 ± 0.001.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present results of an optical spectroscopic survey using SALT and the Nordic Optical Telescope to build a Wide-field Infrared Survey Explorer mid-infrared color-based, dust-unbiased sample of powerful radio-bright (&gt;200 mJy at 1.4 GHz) active galactic nuclei (AGN) for the MeerKAT Absorption Line Survey (MALS). Our sample has 250 AGN (median <jats:italic>z</jats:italic> = 1.8) showing emission lines, 26 with no emission lines, and 27 without optical counterparts. Overall, our sample is fainter (Δ<jats:italic>i</jats:italic> = 0.6 mag) and redder (Δ(<jats:italic>g</jats:italic>−<jats:italic>i</jats:italic>) = 0.2 mag) than radio-selected quasars, and representative of fainter quasar population detected in optical surveys. About 20% of the sources are narrow-line AGN (NLAGN)–65% of these, at <jats:italic>z</jats:italic> &lt; 0.5 are galaxies without strong nuclear emission, and 10% at <jats:italic>z</jats:italic> &gt; 1.9, have emission line ratios similar to radio galaxies. The farthest NLAGN in our sample is M1513-2524 (<jats:italic>z</jats:italic> <jats:sub>em</jats:sub> = 3.132), and the largest radio source (size ∼330 kpc) is M0909-3133 (<jats:italic>z</jats:italic> <jats:sub>em</jats:sub> = 0.884). We discuss in detail 110 AGN at 1.9 &lt; <jats:italic>z</jats:italic> &lt; 3.5. Despite representing the radio loudest quasars (median <jats:italic>R</jats:italic> = 3685), their Eddington ratios are similar to the Sloan Digital Sky Survey quasars having lower <jats:italic>R</jats:italic>. We detect four C <jats:sc>iv</jats:sc> broad-absorption line (BAL) QSOs, all among AGN with least <jats:italic>R</jats:italic>, and highest black hole masses and Eddington ratios. The BAL detection rate (<jats:inline-formula> <jats:tex-math> <?CDATA ${4}_{-2}^{+3}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac4220ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>%) is consistent with that seen in extremely powerful (<jats:italic>L</jats:italic> <jats:sub>1.4GHz</jats:sub> &gt; 10<jats:sup>25</jats:sup> W Hz<jats:sup>−1</jats:sup>) quasars. Using optical light curves, radio polarization, and <jats:italic>γ</jats:italic>-ray detections, we identify seven high-probability BL Lacertae objects. We also summarize the full MALS footprint to search for H <jats:sc>i</jats:sc> 21 cm and OH 18 cm lines at <jats:italic>z</jats:italic> &lt; 2.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Modern cosmic microwave background (CMB) analysis pipelines regularly employ complex time-domain filters, beam models, masking, and other techniques during the production of sky maps and their corresponding angular power spectra. However, these processes can generate couplings between multipoles from the same spectrum and from different spectra, in addition to the typical power attenuation. Within the context of pseudo-<jats:italic>C</jats:italic> <jats:sub> <jats:italic>ℓ</jats:italic> </jats:sub> based, <jats:monospace>MASTER</jats:monospace>-style analyses, the net effect of the time-domain filtering is commonly approximated by a multiplicative transfer function, <jats:italic>F</jats:italic> <jats:sub> <jats:italic>ℓ</jats:italic> </jats:sub>, that can fail to capture mode mixing and is dependent on the spectrum of the signal. To address these shortcomings, we have developed a simulation-based spectral correction approach that constructs a two-dimensional transfer matrix, <jats:inline-formula> <jats:tex-math> <?CDATA ${J}_{{\ell }{\ell }^{\prime} }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>J</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="italic">ℓ</mml:mi> <mml:mi mathvariant="italic">ℓ</mml:mi> <mml:mo accent="false">′</mml:mo> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac562fieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, which contains information about mode mixing in addition to mode attenuation. We demonstrate the application of this approach on data from the first flight of the <jats:sc>Spider</jats:sc> balloon-borne CMB experiment.</jats:p>