Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Short-period, low-mass water-rich planets are subject to strong irradiation from their host star, resulting in hydrospheres in a supercritical state. In this context, we explore the role of irradiation on small terrestrial planets that are moderately wet in the low-mass regime (0.2–1 <jats:italic>M</jats:italic> <jats:sub>⊕</jats:sub>). We investigate their bulk properties for water content in the 0.01–5% range by making use of an internal structure model that is coupled to an atmosphere model. This coupling allows us to take into account both the compression of the interior due to the weight of the hydrosphere and the possibility of atmospheric instability in the low-mass regime. We show that, even for low masses and low water content, these planets display inflated atmospheres. For extremely low planetary masses and high irradiation temperatures, we find that steam atmospheres become gravitationally unstable when the ratio <jats:italic>η</jats:italic> of their scale height to planetary radius exceeds a critical value of ∼0.1. This result is supported by observational data, as all currently detected exoplanets exhibit values of <jats:italic>η</jats:italic> smaller than 0.013. Depending on their water content, our results show that highly irradiated, low-mass planets up to 0.9 <jats:italic>M</jats:italic> <jats:sub>⊕</jats:sub> with significative hydrospheres are not in a stable form and should lose their volatile envelope.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Galactic supernova remnants (SNRs) and their environments provide the nearest laboratories to study SN feedback. We performed molecular observations toward SNR W49B, the most luminous Galactic SNR in the X-ray band, aiming to explore signs of multiple feedback channels of SNRs on nearby molecular clouds (MCs). We found very broad HCO<jats:sup>+</jats:sup> lines with widths of <jats:italic>dv</jats:italic> ∼ 48–75 km s<jats:sup>−1</jats:sup> in the SNR southwest, providing strong evidence that W49B is perturbing MCs at a systemic velocity of <jats:italic>V</jats:italic> <jats:sub> <jats:sc>LSR</jats:sc> </jats:sub> = 61–65 km s<jats:sup>−1</jats:sup>, and placing the W49B at a distance of 7.9 ± 0.6 kpc. We observed unusually high-intensity ratios of HCO<jats:sup>+</jats:sup> <jats:italic>J</jats:italic>=1–0/CO <jats:italic>J</jats:italic>=1–0 not only at shocked regions (1.1 ± 0.4 and 0.70 ± 0.16) but also in quiescent clouds over 1 pc away from the SNR’s eastern boundary (≥0.2). By comparing with the magnetohydrodynamics shock models, we interpret that the high ratio in the broad-line regions can result from a cosmic-ray (CR) induced chemistry in shocked MCs, where the CR ionization rate is enhanced to around 10–10<jats:sup>2</jats:sup> times of the Galactic level. The high HCO<jats:sup>+</jats:sup>/CO ratio outside the SNR is probably caused by the radiation precursor, while the luminous X-ray emission of W49B can explain a few properties in this region. The above results provide observational evidence that SNRs can strongly influence the molecular chemistry in and outside the shock boundary via their shocks, CRs, and radiation. We propose that the HCO<jats:sup>+</jats:sup>/CO ratio is a potentially useful tool to probe an SNR’s multichannel influence on MCs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a method for creating simulated galaxy catalogs with realistic galaxy luminosities, broadband colors, and projected clustering over large cosmic volumes. The technique, denoted <jats:sc>Addgals</jats:sc> (Adding Density Dependent GAlaxies to Lightcone Simulations), uses an empirical approach to place galaxies within lightcone outputs of cosmological simulations. It can be applied to significantly lower-resolution simulations than those required for commonly used methods such as halo occupation distributions, subhalo abundance matching, and semi-analytic models, while still accurately reproducing projected galaxy clustering statistics down to scales of <jats:italic>r</jats:italic> ∼ 100 <jats:italic>h</jats:italic> <jats:sup>−1</jats:sup>kpc . We show that <jats:sc>Addgals</jats:sc> catalogs reproduce several statistical properties of the galaxy distribution as measured by the Sloan Digital Sky Survey (SDSS) main galaxy sample, including galaxy number densities, observed magnitude and color distributions, as well as luminosity- and color-dependent clustering. We also compare to cluster–galaxy cross correlations, where we find significant discrepancies with measurements from SDSS that are likely linked to artificial subhalo disruption in the simulations. Applications of this model to simulations of deep wide-area photometric surveys, including modeling weak-lensing statistics, photometric redshifts, and galaxy cluster finding, are presented in DeRose et al., and an application to a full cosmology analysis of Dark Energy Survey (DES) Year 3 like data is presented in DeRose et al. We plan to publicly release a 10,313 square degree catalog constructed using <jats:sc>Addgals</jats:sc> with magnitudes appropriate for several existing and planned surveys, including SDSS, DES, VISTA, Wide-field Infrared Survey Explorer, and Rubin Observatory’s Legacy Survey of Space and Time.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The chemical abundances of very metal-poor stars provide important constraints on the nucleosynthesis of the first generation of stars and early chemical evolution of the Galaxy. We have obtained high-resolution spectra with the Subaru Telescope for candidates of very metal-poor stars selected with a large survey of Galactic stars carried out with LAMOST. In this series of papers, we report on the elemental abundances of about 400 very metal-poor stars and discuss the kinematics of the sample obtained by combining the radial velocities measured in this study and recent astrometry obtained with Gaia. This paper provides an overview of our survey and follow-up program, and reports radial velocities for the whole sample. We identify seven double-lined spectroscopic binaries from our high-resolution spectra, for which radial velocities of the components are reported. We discuss the frequency of such relatively short-period binaries at very low metallicity.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present homogeneous abundance analysis of over 20 elements for 385 very metal-poor (VMP) stars based on the LAMOST survey and follow-up observations with the Subaru Telescope. It is the largest high-resolution VMP sample (including 363 new objects) studied by a single program, and the first attempt to accurately determine evolutionary stages for such a large sample based on Gaia parallaxes. The sample covers a wide metallicity range from [Fe/H] ≲ −1.7 down to [Fe/H] ∼ −4.3, including over 110 objects with [Fe/H] ≤ −3.0. The expanded coverage in evolutionary status makes it possible to define the abundance trends respectively for giants and turnoff stars. The newly obtained abundance data confirm most abundance trends found by previous studies, but also provide useful updates and new samples of outliers. The Li plateau is seen in main-sequence turnoff stars with −2.5 &lt; [Fe/H] &lt; −1.7 in our sample, whereas the average Li abundance is clearly lower at lower metallicity. Mg, Si, and Ca are overabundant with respect to Fe, showing decreasing trend with increasing metallicity. Comparisons with chemical evolution models indicate that the overabundance of Ti, Sc, and Co are not well reproduced by current theoretical predictions. Correlations are seen between Sc and <jats:italic>α</jats:italic>-elements, while Zn shows a detectable correlation only with Ti but not with other <jats:italic>α</jats:italic>-elements. The fraction of carbon-enhanced stars ([C/Fe] &gt; 0.7) is in the range of 20%–30% for turnoff stars depending on the treatment of objects for which C abundance is not determined, which is much higher than that in giants (∼8%). Twelve Mg-poor stars ([Mg/Fe] &lt; 0.0) have been identified in a wide metallicity range from [Fe/H] ∼ −3.8 through −1.7. Twelve Eu-rich stars ([Eu/Fe] &gt; 1.0) have been discovered in −3.4 &lt; [Fe/H] &lt; −2.0, enlarging the sample of <jats:italic>r</jats:italic>-process-enhanced stars with relatively high metallicity.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this work, predictions of the Ginzburg–Landau theory of dark energy (GLT) for cosmic microwave background (CMB) lensing are studied. We find that the time and scale dependence of the dark energy fluctuations in this semiphenomenological model is favored by data in several ways. First, unlike ΛCDM, <jats:italic>ℓ</jats:italic> ≤ 801 and <jats:italic>ℓ</jats:italic> &gt; 801 ranges of the CMB angular power spectrum are consistent in this framework. Second, the lensing amplitude <jats:italic>A</jats:italic> <jats:sub> <jats:italic>L</jats:italic> </jats:sub> is completely consistent with unity when GLT is confronted with CMB data, even without including CMB lensing data. Therefore the lensing anomaly is absent in this model. Although the background evolution of dark energy in this model is able to reconcile the <jats:italic>H</jats:italic> <jats:sub>0</jats:sub> inferred from CMB with that directly measured through observing nearby standard candles, the inclusion of Baryon Acoustic Oscillations (BAO) data brings the inferred <jats:italic>H</jats:italic> <jats:sub>0</jats:sub> close to what ΛCDM predicts and hence the Hubble tension is not fully eased. However, this does not affect the posterior on <jats:italic>A</jats:italic> <jats:sub> <jats:italic>L</jats:italic> </jats:sub> and the lensing anomaly is still absent.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Most globular clusters (GCs) show evidence for multiple stellar populations, suggesting the occurrence of several distinct star formation episodes. The large fraction of second population (2P) stars observed requires a very large 2P gaseous mass to have accumulated in the cluster core to form these stars. Hence, the first population of stars (1P) in the cluster core has had to become embedded in 2P gas, just prior to the formation of later populations. Here we explore the evolution of binaries in ambient 2P gaseous media of multiple-population GCs. We mostly focus on black hole binaries and follow their evolution as they evolve from wide binaries toward short periods through interaction with ambient gas, followed by gravitational-wave (GW) dominated inspiral and merger. We show that this novel GW merger channel could provide a major contribution to the production of GW sources. We consider various assumptions and initial conditions and calculate the resulting gas-mediated change in the population of binaries and the expected merger rates due to gas-catalyzed GW inspirals. For plausible conditions and assumptions, we find an expected GW merger rate observable by aLIGO of the order of up to a few tens of Gpc<jats:sup>−3</jats:sup> yr<jats:sup>−1</jats:sup> and an overall range for our various models of 0.08–25.51 Gpc<jats:sup>−3</jats:sup> yr<jats:sup>−1</jats:sup>. Finally, our results suggest that the conditions and binary properties in the early stage of GCs could be critically affected by gas interactions and may require a major revision in the current modeling of the evolution of GCs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Recently, the MAGIC Collaboration reported a ∼5<jats:italic>σ</jats:italic> statistical significance of the very-high-energy (VHE) emission from a distant gamma-ray burst (GRB), GRB 201216C. Such distant GRB may be effectively absorbed by the extragalactic background light (EBL). The origin of the VHE emission from such distant objects is still unknown. Here, we propose a numerical model for studying the afterglow emission of this distant GRB. The model solves the continuity equation governing the temporal evolution of electron distribution, and the broadband observed data can be explained by the synchrotron plus synchrotron self-Compton (SSC) radiation of the forward shock. The predicted observed 0.1 TeV flux can reach ∼10<jats:sup>−9</jats:sup>−10<jats:sup>−10</jats:sup> erg cm<jats:sup>−2</jats:sup> s<jats:sup>−1</jats:sup> at <jats:italic>t</jats:italic> ∼ 10<jats:sup>3</jats:sup>−10<jats:sup>4</jats:sup> s, even with strong EBL absorption, such strong sub-teraelectronvolt (sub-TeV) emissions still can be observed by the MAGIC telescope. Using this numerical model, the shock parameters in the modeling are similar to two other sub-TeV GRBs (i.e., GRB 190114C and GRB 180720B), implying that the sub-TeV GRBs have some commonalities: they have energetic burst energy, low circumburst medium density, and a low magnetic equipartition factor. We regard GRB 201216C as a typical GRB, and estimate the maximum redshift of GRB that can be detected by the MAGIC telescope, i.e., <jats:italic>z</jats:italic> ∼ 1.6. We also find that the VHE photon energy of such distant GRB can only reach ∼0.1 TeV. Improving the low energy sensitivity of the VHE telescope is very important to detect the sub-TeV emissions of these distant GRBs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present measurements of periodicity for transverse loop oscillations during the periods of activity of two remote and separated (both temporally and spatially) flares. The oscillations are observed in the same location more than 100 Mm away from the visible footpoints of the loops. Evidence for several possible excitation sources is presented. After close examination, we find that the eruptions during the flaring activities play an important role in triggering the oscillations. We investigate periodicities using time–distance, fast Fourier transform, and wavelet techniques. Despite different excitation sources in the vicinity of the loops and the changing nature of amplitudes, the periodicity of multiple oscillations is found to be 4–6 min.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Extended, old, and round stellar halos appear to be ubiquitous around high-mass dwarf galaxies (10<jats:sup>8.5</jats:sup> &lt; <jats:italic>M</jats:italic> <jats:sub>⋆</jats:sub>/<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> &lt; 10<jats:sup>9.6</jats:sup>) in the observed universe. However, it is unlikely that these dwarfs have undergone a sufficient number of minor mergers to form stellar halos that are composed of predominantly accreted stars. Here, we demonstrate that FIRE-2 (Feedback in Realistic Environments) cosmological zoom-in simulations are capable of producing dwarf galaxies with realistic structures, including both a thick disk and round stellar halo. Crucially, these stellar halos are formed in situ, largely via the outward migration of disk stars. However, there also exists a large population of “nondisky” dwarfs in FIRE-2 that lack a well-defined disk/halo and do not resemble the observed dwarf population. These nondisky dwarfs tend to be either more gas-poor or to have burstier recent star formation histories than the disky dwarfs, suggesting that star formation feedback may be preventing disk formation. Both classes of dwarfs underscore the power of a galaxy’s intrinsic shape—which is a direct quantification of the distribution of the galaxy’s stellar content—to interrogate the feedback implementation in simulated galaxies.</jats:p>