Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>In this era of Gaia and ALMA, dynamical stellar mass measurements, derived from spatially and spectrally resolved observations of the Keplerian rotation of circumstellar disks, provide benchmarks that are independent of observations of stellar characteristics and their uncertainties. These benchmarks can then be used to validate and improve stellar evolutionary models, the latter of which can lead to both imprecise and inaccurate mass predictions for pre-main-sequence, low-mass (≤0.5<jats:italic> M</jats:italic> <jats:sub>⊙</jats:sub>) stars. We present the dynamical stellar masses derived from disks around three M stars (FP Tau, J0432+1827, and J1100–7619) using ALMA observations of <jats:sup>12</jats:sup>CO (<jats:italic>J</jats:italic> = 2–1) and <jats:sup>13</jats:sup>CO (<jats:italic>J</jats:italic> = 2–1) emission. These are the first dynamical stellar mass measurements for J0432+1827 and J1100–7619 (0.192 ± 0.005 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> and 0.461 ± 0.057 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, respectively) and the most precise measurement for FP Tau (0.395 ± 0.012 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>). Fiducial stellar evolutionary model tracks, which do not include any treatment of magnetic activity, agree with the dynamical stellar mass measurement of J0432+1827 but underpredict the mass by ∼60% for FP Tau and by ∼80% for J1100–7619. Possible explanations for the underpredictions include inaccurate assumptions of stellar effective temperature, undetected binarity for J1100–7619, and that fiducial stellar evolutionary models are not complex enough to represent these stars. In the former case, the stellar effective temperatures would need to be increased by amounts ranging from ∼40 to ∼340 K to reconcile the fiducial stellar evolutionary model predictions with the dynamically measured masses. In the latter case, we show that the dynamical masses can be reproduced using results from stellar evolutionary models with starspots, which incorporate fractional starspot coverage to represent the manifestation of magnetic activity. Folding in low-mass M stars from the literature and assuming that the stellar effective temperatures are imprecise but accurate, we find tentative evidence of a relationship between fractional starspot coverage and observed effective temperature for these young, cool stars.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We analyzed archival molecular line data of pre-main-sequence (PMS) stars in the Lupus and Taurus star-forming regions obtained with ALMA surveys with an integration time of a few minutes per source. We stacked the data of <jats:sup>13</jats:sup>CO and C<jats:sup>18</jats:sup>O (<jats:italic>J</jats:italic> = 2–1 and 3–2) and CN (<jats:italic>N</jats:italic> = 3–2, <jats:italic>J</jats:italic> = 7/2–5/2) lines to enhance the signal-to-noise ratios and measured the stellar masses of 45 out of 67 PMS stars from the Keplerian rotation in their circumstellar disks. The measured dynamical stellar masses were compared to the stellar masses estimated from the spectroscopic measurements with seven different stellar evolutionary models. We found that the magnetic model of Feiden provides the best estimate of the stellar masses in the mass range of 0.6 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> ≤ <jats:italic>M</jats:italic> <jats:sub>⋆</jats:sub> ≤ 1.3 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> with a deviation of &lt;0.7<jats:italic>σ</jats:italic> from the dynamical masses, while all the other models underestimate the stellar masses in this mass range by 20%–40%. In the mass range of &lt;0.6 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, the stellar masses estimated with the magnetic model of Feiden have a larger deviation (&gt;2<jats:italic>σ</jats:italic>) from the dynamical masses, and other, nonmagnetic stellar evolutionary models of Siess et al., Baraffe et al., and Feiden show better agreement with the dynamical masses with the deviations of 1.4<jats:italic>σ</jats:italic>–1.6<jats:italic>σ</jats:italic>. Our results show the mass dependence of the accuracy of these stellar evolutionary models.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>With current and upcoming experiments such as the Wide Field Infrared Survey Telescope, Euclid, and Large Synoptic Survey Telescope, we can observe up to billions of galaxies. While such surveys cannot obtain spectra for all observed galaxies, they produce galaxy magnitudes in color filters. This data set behaves like a high-dimensional nonlinear surface, an excellent target for machine learning. In this work, we use a lightcone of semianalytic galaxies tuned to match Cosmic Assembly Near-infrared Deep Legacy Survey (CANDELS) observations from Lu et al. to train a set of neural networks on a set of galaxy physical properties. We add realistic photometric noise and use trained neural networks to predict stellar masses and average star formation rates (SFRs) on real CANDELS galaxies, comparing our predictions to SED-fitting results. On semianalytic galaxies, we are nearly competitive with template-fitting methods, with biases of 0.01 dex for stellar mass, 0.09 dex for SFR, and 0.04 dex for metallicity. For the observed CANDELS data, our results are consistent with template fits on the same data at 0.15 dex bias in <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{\mathrm{star}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabd179ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> and 0.61 dex bias in the SFR. Some of the bias is driven by SED-fitting limitations, rather than limitations on the training set, and some is intrinsic to the neural network method. Further errors are likely caused by differences in noise properties between the semianalytic catalogs and data. Our results show that galaxy physical properties can in principle be measured with neural networks at a competitive degree of accuracy and precision to template-fitting methods.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>For many years it has been suggested that the carbonaceous material found in association with Fe/Ni metal and metal carbides in primitive bodies is linked to the Fischer–Tropsch reaction. This is especially true with chondritic-porous interplanetary dust particles, which are considered to have a cometary origin and are among some of the most primitive and least processed materials available for study. Another phenomenon which occurs under the same carburizing conditions as the Fischer–Tropsch reaction is called metal dusting and could be a possible pathway to forming some of the carbonaceous material found in primitive bodies. Metal dusting is a catastrophic corrosion of metal under these carburizing conditions that results in a porous mixture of carbonaceous material, metal, and metal carbides. In the case of pure iron, type I metal dusting results in the formation of a metastable iron carbide, typically cementite, Fe<jats:sub>3</jats:sub>C. While metal dusting has been studied industrially for over 50 years, it does not appear to have been applied to the formation of carbonaceous material in astrophysical settings. In this work, the general mechanism of metal dusting on iron is described and a thermodynamic analysis of the dusting phenomena applied to solar nebula conditions. Rate measurements are made with pure iron samples over the temperature range from 400°C to 950°C. In addition, the products from experimental runs at 500°C and 600°C are studied by transmission electron microscopy. Results show that iron carbide particles are formed with carbonaceous material consisting of poorly graphitized carbon.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a study of the Trapezium cluster in Orion. We analyze flux-calibrated Very Large Telescope/Multi-Unit Spectroscopic Explorer spectra of 361 stars to simultaneously measure the spectral types, reddening, and the optical veiling due to accretion. We find that the extinction law from Cardelli et al. with a total-to-selective extinction value of <jats:italic>R</jats:italic> <jats:sub>V</jats:sub> = 5.5 is more suitable for this cluster. For 68% of the sample the new spectral types are consistent with literature spectral types within two subclasses but, as expected, we derive systematically later types than the literature by one to two subclasses for the sources with significant accretion levels. Here we present an improved Hertzsprung–Russell (H-R) diagram of the Trapezium cluster, in which the contamination by optical veiling on spectral types and stellar luminosities has been properly removed. A comparison of the locations of the stars in the H-R diagram with the non-magnetic and magnetic pre-main-sequence evolutionary tracks indicates an age of 1–2 Myr. The magnetic pre-main-sequence evolutionary tracks can better explain the luminosities of the low-mass stars. In the H-R diagram, the cluster exhibits a large luminosity spread (<jats:italic>σ</jats:italic>(Log <jats:italic>L</jats:italic> <jats:sub>⋆</jats:sub>/<jats:italic>L</jats:italic> <jats:sub>⊙</jats:sub>) ∼ 0.3). By collecting a sample of 14 clusters/groups with different ages, we find that the luminosity spread tends to be constant (<jats:italic>σ</jats:italic>(Log <jats:italic>L</jats:italic> <jats:sub>⋆</jats:sub>/<jats:italic>L</jats:italic> <jats:sub>⊙</jats:sub>) ∼ 0.2–0.25) after 2 Myr, which suggests that age spread is not the main cause of the luminosity spread. There are ∼0.1 dex larger luminosity spreads for the younger clusters, e.g., the Trapezium cluster, than the older clusters, which can be explained by the starspots, accretion history, and circumstellar disk orientations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the early-time light curves of Type Ia supernovae (SNe Ia) observed in the first six sectors of Transiting Exoplanet Survey Satellite (TESS) data. Ten of these SNe were discovered by ASAS-SN, seven by ATLAS, six by ZTF, and one by Gaia. For nine of these objects with sufficient dynamic range (&gt;3.0 mag from detection to peak), we fit power-law models and searched for signatures of companion stars. We found a diversity of early-time light-curve shapes, although most of our sources are consistent with fireball models where the flux increases as ∝<jats:italic>t</jats:italic> <jats:sup>2</jats:sup>. Three SNe displayed a flatter rise with flux ∝<jats:italic>t</jats:italic>. We did not find any obvious evidence for additional structures, such as multiple power-law components, in the early rising light curves. For assumptions about the SN properties and the observer viewing angle (ejecta mass of 1.4 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, expansion velocity of 10<jats:sup>4</jats:sup> km s<jats:sup>−1</jats:sup>, opacity of 0.2 cm<jats:sup>2</jats:sup> g<jats:sup>−1</jats:sup>, and viewing angle of 45°) and a further assumption that any companion stars would be in Roche lobe overflow, it is possible to place upper limits on the radii of any companion stars. Six of the nine SNe had complete coverage of the early-time light curves, and we placed upper limits on the radii of companion stars of ≲32 <jats:italic>R</jats:italic> <jats:sub>⊙</jats:sub> for these SNe, ≲20 <jats:italic>R</jats:italic> <jats:sub>⊙</jats:sub> for five of the six, and ≲4 <jats:italic>R</jats:italic> <jats:sub>⊙</jats:sub> for two of the six. The small sample size did not allow us to put limits on the occurrence rate of companion stars in the progenitors of SNe Ia. However, we expect that TESS observed enough SNe in its two-year primary mission (26 sectors) to either detect the signature of a large companion (<jats:italic>R</jats:italic> &gt; 20<jats:italic> R</jats:italic> <jats:sub>⊙</jats:sub>) or constrain the occurrence rate of such systems, at least for the fiducial SN properties adopted here. We also show that TESS is capable of detecting emission from a 1 <jats:italic>R</jats:italic> <jats:sub>⊙</jats:sub> companion for an SN Ia within 50 Mpc and has a reasonable chance of doing so after about six years.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>X-ray emission from quasars has been detected up to redshift <jats:italic>z</jats:italic> = 7.5, although only limited to a few objects at <jats:italic>z</jats:italic> &gt; 6.5. In this work, we present new Chandra observations of five <jats:italic>z</jats:italic> &gt; 6.5 quasars. By combining with archival Chandra observations of six additional <jats:italic>z</jats:italic> &gt; 6.5 quasars, we perform a systematic analysis on the X-ray properties of these earliest accreting supermassive black holes (SMBHs). We measure the black hole masses, bolometric luminosities (<jats:italic>L</jats:italic> <jats:sub>bol</jats:sub>), Eddington ratios (<jats:italic>λ</jats:italic> <jats:sub>Edd</jats:sub>), emission line properties, and infrared luminosities (<jats:italic>L</jats:italic> <jats:sub>IR</jats:sub>) of these quasars using infrared and submillimeter observations. Correlation analysis indicates that the X-ray bolometric correction (the factor that converts from X-ray luminosity to bolometric luminosity) decreases with increasing <jats:italic>L</jats:italic> <jats:sub>bol</jats:sub>, and that the UV/optical-to-X-ray ratio, <jats:italic>α</jats:italic> <jats:sub>ox</jats:sub>, strongly correlates with <jats:italic>L</jats:italic> <jats:sub>2500 <jats:italic>Å</jats:italic> </jats:sub>, and moderately correlates with <jats:italic>λ</jats:italic> <jats:sub>Edd</jats:sub> and blueshift of C <jats:sc>iv</jats:sc> emission lines. These correlations are consistent with those found in lower-<jats:italic>z</jats:italic> quasars, indicating quasar accretion physics does not evolve with redshift. We also find that <jats:italic>L</jats:italic> <jats:sub>IR</jats:sub> does not correlate with <jats:italic>L</jats:italic> <jats:sub>2–10 keV</jats:sub> in these luminous distant quasars, suggesting that the ratio of the SMBH growth rate and their host galaxy growth rate in these early luminous quasars are different from those of local galaxies. A joint spectral analysis of the X-ray detected <jats:italic>z</jats:italic> &gt; 6.5 quasars yields an average X-ray photon index of <jats:inline-formula> <jats:tex-math> <?CDATA ${\rm{\Gamma }}={2.32}_{-0.30}^{+0.31}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabcc5eieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, steeper than that of low-<jats:italic>z</jats:italic> quasars. By comparing it with the Γ − <jats:italic>λ</jats:italic> <jats:sub>Edd</jats:sub> relation, we conclude that the steepening of Γ for quasars at <jats:italic>z</jats:italic> &gt; 6.5 is mainly driven by their higher Eddington ratios.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present Atacama Large Millimeter/submillimeter Array (ALMA) CO(2–1) spectroscopy of six massive (log<jats:sub>10</jats:sub> <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{* }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabcbf6ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>/<jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{\odot }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabcbf6ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> &gt; 11.3) quiescent galaxies at <jats:italic>z</jats:italic> ∼ 1.5. These data represent the largest sample using CO emission to trace molecular gas in quiescent galaxies above <jats:italic>z</jats:italic> &gt; 1, achieving an average 3<jats:italic>σ</jats:italic> sensitivity of <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{{{\rm{H}}}_{2}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabcbf6ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> ∼ 10<jats:sup>10</jats:sup> <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{\odot }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabcbf6ieqn4.gif" xlink:type="simple" /> </jats:inline-formula>. We detect one galaxy at 4<jats:italic>σ</jats:italic> significance and place upper limits on the molecular gas reservoirs of the other five, finding molecular gas mass fractions <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{{{\rm{H}}}_{2}}/{M}_{* }={f}_{{{\rm{H}}}_{2}}\lt 2 \% \mbox{--}6 \% $?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabcbf6ieqn5.gif" xlink:type="simple" /> </jats:inline-formula> (3<jats:italic>σ</jats:italic> upper limits). This is 1–2 orders of magnitude lower than coeval star-forming galaxies at similar stellar mass, and comparable to galaxies at <jats:italic>z</jats:italic> = 0 with similarly low specific star formation rate (sSFR). This indicates that their molecular gas reservoirs were rapidly and efficiently used up or destroyed, and that gas fractions are uniformly low (&lt;6%) despite the structural diversity of our sample. The implied rapid depletion time of molecular gas (<jats:inline-formula> <jats:tex-math> <?CDATA ${t}_{\mathrm{dep}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabcbf6ieqn6.gif" xlink:type="simple" /> </jats:inline-formula>&lt; 0.6 Gyr) disagrees with extrapolations of empirical scaling relations to low sSFR. We find that our low gas fractions are instead in agreement with predictions from both the recent <jats:sc>simba</jats:sc> cosmological simulation, and from analytical “bathtub” models for gas accretion onto galaxies in massive dark matter halos (log<jats:inline-formula> <jats:tex-math> <?CDATA ${}_{10}{M}_{\mathrm{halo}}/{M}_{\odot }\sim 14$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabcbf6ieqn7.gif" xlink:type="simple" /> </jats:inline-formula> at <jats:italic>z</jats:italic> = 0). Such high mass halos reach a critical mass of log<jats:inline-formula> <jats:tex-math> <?CDATA ${}_{10}{M}_{\mathrm{halo}}/{M}_{\odot }\gt 12$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabcbf6ieqn8.gif" xlink:type="simple" /> </jats:inline-formula> by <jats:italic>z</jats:italic> ∼ 4 that halt the accretion of baryons early in the universe. Our data are consistent with a simple picture where galaxies truncate accretion and then consume the existing gas at or faster than typical main-sequence rates. Alternatively, we cannot rule out that these galaxies reside in lower mass halos, and low gas fractions may instead reflect either stronger feedback, or more efficient gas consumption.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a statistical analysis for the characteristics and radial evolution of linear magnetic holes (LMHs) in the solar wind from 0.166 to 0.82 au using Parker Solar Probe observations of the first two orbits. It is found that the LMHs mainly have a duration less than 25 s and the depth is in the range from 0.25 to 0.7. The durations slightly increase and the depths become slightly deeper with the increasing heliocentric distance. Both the plasma temperature and the density for about 50% of all events inside the holes are higher than the ones surrounding the holes. The average occurrence rate is 8.7 events day<jats:sup>−1</jats:sup>, much higher than that of the previous observations. The occurrence rate of the LMHs has no clear variation with the heliocentric distance (only a slight decreasing trend with the increasing heliocentric distance), and has several enhancements around ∼0.525 and ∼0.775 au, implying that there may be new locally generated LMHs. All events are segmented into three parts (i.e., 0.27, 0.49, and 0.71 au) to investigate the geometry evolution of the linear magnetic holes. The results show that the geometry of LMHs are prolonged both across and along the magnetic field direction from the Sun to the Earth, while the scales across the field extend a little faster than along the field. The present study could help us understand the evolution and formation mechanism of the LMHs in the solar wind.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Einstein's general relativity, as the most successful theory of gravity, is one of the cornerstones of modern physics. However, the experimental tests for gravity in the high energy region are limited. The emerging gravitational-wave astronomy has opened an avenue for probing the fundamental properties of gravity in a strong and dynamical field, and in particular, a high energy regime. In this work, we test the parity conservation of gravity with gravitational waves. If the parity symmetry is broken, the left- and right-handed modes of gravitational waves would follow different equations of motion, dubbed as birefringence. We perform full Bayesian inference by comparing the state-of-the-art waveform with parity violation with the compact binary coalescence data released by LIGO and Virgo collaboration. We do not find any violations of general relativity, thus constrain the lower bound of the parity-violating energy scale to be 0.09 GeV through the velocity birefringence of gravitational waves. This provides the most stringent experimental test of gravitational parity symmetry to date. We also find third generation gravitational-wave detectors can enhance this bound to <jats:inline-formula> <jats:tex-math> <?CDATA ${ \mathcal O }({10}^{2})$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabd7a6ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> GeV if there is still no violation, comparable to the current energy scale in particle physics, which indicates gravitational-wave astronomy can usher in a new era of testing the ultraviolet behavior of gravity in the high energy region.</jats:p>