Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Gravitational-wave observations of binary neutron star mergers provide valuable information about neutron star structure and the equation of state of dense nuclear matter. Numerous methods have been proposed to analyze the population of observed neutron stars, and previous work has demonstrated the necessity of jointly fitting the astrophysical distribution and the equation of state in order to accurately constrain the equation of state. In this work, we introduce a new framework to simultaneously infer the distribution of binary neutron star masses and the nuclear equation of state using Gaussian mixture model density estimates, which mitigates some of the limitations previously used methods suffer from. Using our method, we reproduce previous projections for the expected precision of our joint mass distribution and equation-of-state inference with tens of observations. We also show that mismodeling the equation of state can bias our inference of the neutron star mass distribution. While we focus on neutron star masses and matter effects, our method is widely applicable to population inference problems.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Baldwin, Philips, &amp; Terlevich diagram of [O <jats:sc>iii</jats:sc>]/H<jats:italic>β</jats:italic> versus [N <jats:sc>ii</jats:sc>]/H<jats:italic>α</jats:italic> (hereafter N2-BPT) has long been used as a tool for classifying galaxies based on the dominant source of ionizing radiation. Recent observations have demonstrated that galaxies at <jats:italic>z</jats:italic> ∼ 2 reside offset from local galaxies in the N2-BPT space. In this paper, we conduct a series of controlled numerical experiments to understand the potential physical processes driving this offset. We model nebular line emission in a large sample of galaxies, taken from the <jats:sc>simba</jats:sc> cosmological hydrodynamic galaxy formation simulation, using the <jats:sc>cloudy</jats:sc> photoionization code to compute the nebular line luminosities from H <jats:sc>ii</jats:sc> regions. We find that the observed shift toward higher [O <jats:sc>iii</jats:sc>]/H<jats:italic>β</jats:italic> and [N <jats:sc>ii</jats:sc>]/H<jats:italic>α</jats:italic> values at high redshift arises from sample selection: when we consider only the most massive galaxies <jats:italic>M</jats:italic> <jats:sub>*</jats:sub> ∼ 10<jats:sup>10–11</jats:sup> <jats:italic> M</jats:italic> <jats:sub>⊙</jats:sub>, the offset naturally appears, due to their high metallicities. We predict that deeper observations that probe lower-mass galaxies will reveal galaxies that lie on a locus comparable to <jats:italic>z</jats:italic> ∼ 0 observations. Even when accounting for samples-selection effects, we find that there is a subtle mismatch between simulations and observations. To resolve this discrepancy, we investigate the impact of varying ionization parameters, H <jats:sc>ii</jats:sc> region densities, gas-phase abundance patterns, and increasing radiation field hardness on N2-BPT diagrams. We find that either decreasing the ionization parameter or increasing the N/O ratio of galaxies at fixed O/H can move galaxies along a self-similar arc in N2-BPT space that is occupied by high-redshift galaxies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We study spatially resolved properties (on spatial scales of ∼1–2 kpc out to at least 3 effective radii) of the stars, dust, and gas in 10 nearby spiral galaxies. The properties of the stellar population and dust are derived by fitting the spatially resolved spectral energy distribution (SED) with more than 20 photometric bands ranging from far-ultraviolet to far-infrared. Our newly developed software <jats:monospace>piXedfit</jats:monospace> performs point-spread function matching of images, pixel binning, and models the stellar light, dust attenuation, dust emission, and emission from a dusty torus heated by an active galactic nucleus simultaneously through the energy-balance approach. With this self-consistent analysis, we present the spatially resolved version of the IRX–<jats:italic>β</jats:italic> relation, finding that it is consistent with the relationship from the integrated photometry. We show that the old stellar populations contribute to the dust heating, which causes an overestimation of the star formation rate (SFR) derived from the total ultraviolet and infrared luminosities on kiloparsec scales. With archival high-resolution maps of atomic and molecular gas, we study the radial variation of the properties of the stellar populations (including stellar mass, age, metallicity, and SFR), dust (including dust mass, dust temperature, and abundance of polycyclic aromatic hydrocarbon), and gas, as well as dust-to-stellar mass and dust-to-gas mass ratios. We observe a depletion of the molecular gas mass fraction in the central region of the majority of the galaxies, suggesting that the lack of available fuel is an important factor in suppressing the specific SFR at the center.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the [C <jats:sc>ii</jats:sc>] 157.7 <jats:italic>μ</jats:italic>m map of galaxy NGC 7331 obtained with the Field-Imaging Far-Infrared Line Spectrometer on board the Stratospheric Observatory for Infrared Astronomy (SOFIA). This map extends an existent Herschel/Photodetector Array Camera and Spectrometer observation of the central strip of the galaxy to encompass the entire molecular ring and much of the disk, including multiple spiral arms with intense far-IR emission. We also present Herschel archival data of the [N <jats:sc>ii</jats:sc>] 205 <jats:italic>μ</jats:italic>m line, which covers a substantial part of the [C <jats:sc>ii</jats:sc>] SOFIA observations and allows us to estimate the neutral fraction of the [C <jats:sc>ii</jats:sc>] emission along the ring and disk of the galaxy. We find that the neutral fraction rises with the distance from the center. In addition, by tracing the azimuthal variation of the neutral fraction, we are able to see how our observing perspective affects this measurement. The high inclination of NGC 7331 allows us to glimpse the internal walls of the molecular ring. There, young bright stars emit UV radiation causing more [C <jats:sc>ii</jats:sc>] emission to be produced in the ionized gas. On the outer walls, opaque dust shrouds the rest of the ring, making the neutral medium the dominant source of [C <jats:sc>ii</jats:sc>] emission. Through spatial analysis comparing the [C <jats:sc>ii</jats:sc>] emission to tracers of gas heating, we are able to investigate how the photoelectric heating efficiency varies throughout NGC 7331 and extend global measurements of the [C <jats:sc>ii</jats:sc>] deficit to local environments. Since the origin of [C <jats:sc>ii</jats:sc>] emission has typically been studied in face-on galaxies, our results shed a new light on the interpretation of [C <jats:sc>ii</jats:sc>] emission, especially when studying distant galaxies with unknown inclination.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We investigate the formation of merging binary black holes (BHs) through isolated binary evolution, performing binary population synthesis calculations covering an unprecedentedly wide metallicity range of Population (Pop) I, II, III, and extremely metal-poor (EMP) binary stars. We find that the predicted merger rate density and primary BH mass (<jats:italic>m</jats:italic> <jats:sub>1</jats:sub>) distribution are consistent with the gravitational wave (GW) observations. Notably, Population III and EMP (&lt;10<jats:sup>−2</jats:sup> <jats:italic>Z</jats:italic> <jats:sub>⊙</jats:sub>) binary stars yield most of the pair instability (PI) mass gap events with <jats:italic>m</jats:italic> <jats:sub>1</jats:sub> = 65–130 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. Population III binary stars contribute more to the PI mass gap events with increasing redshift, and all the PI mass gap events have the Population III origin at redshifts ≳8. Our result can be assessed by future GW observations in the following two points. First, there are no binary BHs with <jats:italic>m</jats:italic> <jats:sub>1</jats:sub> = 100–130 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> in our result, and thus the <jats:italic>m</jats:italic> <jats:sub>1</jats:sub> distribution should suddenly drop in the range of <jats:italic>m</jats:italic> <jats:sub>1</jats:sub> = 100–130 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. Second, the PI mass gap event rate should increase toward higher redshift up to ∼11, since those events mainly originate from the Population III binary stars. We find that the following three assumptions are needed to reproduce the current GW observations: a top-heavy stellar initial mass function and the presence of close binary stars for Population III and EMP binary stars, and inefficient convective overshoot in the main-sequence phase of stellar evolution. Without any of the above, the number of PI mass gap events becomes too low to reproduce current GW observations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present measurements of the expansion of Kepler’s Supernova Remnant (SNR) over three epochs of Chandra X-ray observations from 2000, 2006, and 2014. As the remnant of a historical supernova (observed in 1604 CE), Kepler’s SNR presents the rare opportunity to study the dynamical evolution of such an object in real time. Measurements of the asymmetry in the forward shock velocity can also provide insight into the nature of the explosion and density of the circumstellar material. By combining data from 2014 with previous epochs in 2000 and 2006, we can observe the proper motion of filaments along the outer rim of the SNR. Prior studies of Kepler’s SNR have shown proper motion differences up to a factor of 3 between the northern and southern regions around the remnant. With the longer time baseline we use here, we find results that are consistent with previous studies, but with smaller uncertainties. Additionally, by adding a third epoch of observations, we search for any systemic change in the velocity in the form of a deceleration of the blast wave, as was recently reported in Tycho’s SNR. We find little to no conclusive evidence of such deceleration, and conclude that Kepler’s SNR is encountering circumstellar material that is roughly constant in density, though substantially varied around the periphery.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>High-resolution spectra are unique indicators of three-dimensional (3D) processes in exoplanetary atmospheres. For instance, in 2020, Ehrenreich et al. reported transmission spectra from the ESPRESSO spectrograph yielding an anomalously large Doppler blueshift from the ultrahot Jupiter WASP-76b. Interpretations of these observations invoke toy model depictions of gas-phase iron condensation in lower-temperature regions of the planet’s atmosphere. In this work, we forward model the atmosphere of WASP-76b with double-gray general circulation models (GCMs) and ray-striking radiative transfer to diagnose the planet’s high-resolution transmission spectrum. We confirm that a physical mechanism driving strong east–west asymmetries across the terminator must exist to reproduce large Doppler blueshifts in WASP-76b’s transmission spectrum. We identify low atmospheric drag and a deep radiative-convective boundary as necessary components of our GCM to produce this asymmetry (the latter is consistent with existing Spitzer phase curves). However, we cannot reproduce either the magnitude or the time-dependence of the WASP-76b Doppler signature with gas-phase iron condensation alone. Instead, we find that high-altitude, optically thick clouds composed of Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>, Fe, or Mg<jats:sub>2</jats:sub>SiO<jats:sub>4</jats:sub> provide reasonable fits to the Ehrenreich et al. observations—with marginal contributions from condensation. This fit is further improved by allowing a small orbital eccentricity (<jats:italic>e</jats:italic> ≈ 0.017), consistent with prior WASP-76b orbital constraints. We additionally validate our forward-modeled spectra by reproducing lines of nearly all species detected in WASP-76b by Tabernero et al. Our procedure’s success in diagnosing phase-resolved Doppler shifts demonstrates the benefits of physical, self-consistent, 3D simulations in modeling high-resolution spectra of exoplanet atmospheres.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a strong lensing analysis of the galaxy cluster SDSS J1029+2623 at <jats:italic>z</jats:italic> = 0.588, one of the few currently known lens clusters with multiple images of a background (<jats:italic>z</jats:italic> = 2.1992) quasar with a measured time delay. We use archival Hubble Space Telescope multiband imaging and new Multi Unit Spectroscopic Explorer follow-up spectroscopy to build an accurate lens mass model, a crucial step toward future cosmological applications. The spectroscopic data enable the secure identification of 57 cluster members and of two nearby perturbers along the line of sight. We estimate the inner kinematics of a subset of 20 cluster galaxies to calibrate the scaling relations parameterizing the sub-halo mass component. We also reliably determine the redshift of four multiply imaged sources, provide a tentative measurement for one system, and report the discovery of a new four-image system. The final catalog comprises 26 multiple images from seven background sources, spanning a wide redshift range, from 1.02 to 5.06. We present two parametric lens models, with slightly different cluster mass parameterizations. The observed positions of the multiple images are accurately reproduced within approximately 0.″2, the three image positions of the quasar within only ∼0.″1. We estimate a cluster projected total mass of <jats:italic>M</jats:italic>(&lt;300 kpc) ∼ 2.1 × 10<jats:sup>14</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, with a statistical uncertainty of a few percent. Both models, which include a small galaxy close to one of the quasar images, predict magnitude differences and time delays between the quasar images that are consistent with the observations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Spheromak-type flux ropes are increasingly used for modeling coronal mass ejections (CMEs). Many models aim at accurately reconstructing the magnetic field topology of CMEs, considering its importance in assessing their impact on modern technology and human activities in space and on the ground. However, so far there is little discussion about how the details of the magnetic structure of a spheromak affect its evolution through the ambient field in the modeling domain and what impact this has on the accuracy of magnetic field topology predictions. If the spheromak has its axis of symmetry (geometric axis) at an angle with respect to the direction of the ambient field, then the spheromak starts rotating so that its symmetry axis finally aligns with the ambient field. When using the spheromak in space weather forecasting models, this tilting can happen already during insertion and significantly affects the results. In this paper, we highlight this issue previously not examined in the field of space weather and we estimate the angle by which the spheromak rotates under different conditions. To do this, we generated simple purely radial ambient magnetic field topologies (weak/strong, positive/negative) and inserted spheromaks with varying initial speed, tilt, and magnetic helicity sign. We employ different physical and geometric criteria to locate the magnetic center of mass and axis of symmetry of the spheromak. We confirm that spheromaks rotate in all investigated conditions and their direction and angle of rotation depend on the spheromak’s initial properties and ambient magnetic field strength and orientation.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In the context of extreme adaptive optics for large telescopes, we present the Kraken multi-frame blind deconvolution (MFBD) algorithm for processing high-cadence acquisitions, capable of providing a diffraction-limited estimation of the source brightness distribution. This is achieved by a data modeling of each frame in the sequence driven by the estimation of the instantaneous wave front at the entrance pupil. Under suitable physical constraints, numerical convergence is guaranteed by an iteration scheme starting from a compact MFBD, which provides a very robust initial guess that only employs a few frames. We describe the mathematics behind the process and report the high-resolution reconstruction of the spectroscopic binary <jats:italic>α</jats:italic> And (16.3 mas separation) acquired with the precursor of SHARK-VIS, the upcoming high-contrast camera in the visible for the Large Binocular Telescope.</jats:p>