Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We propose a transport theory for the kinetic evolution of solar-wind electrons in the heliosphere. We derive a gyro-averaged kinetic transport equation that accounts for the spherical expansion of the solar wind and the geometry of the Parker spiral magnetic field. To solve our three-dimensional kinetic equation, we develop a mathematical approach that combines the Crank–Nicolson scheme in velocity space and a finite-difference Euler scheme in configuration space. We initialize our model with isotropic electron distribution functions and calculate the kinetic expansion at heliocentric distances from 5 to 20 solar radii. In our kinetic model, the electrons evolve mainly through the combination of ballistic particle streaming, the magnetic mirror force, and the electric field. By applying fits to our numerical results, we quantify the parameters of the electron strahl and the core part of the electron velocity distributions. The strahl fit parameters show that the density of the electron strahl is around 7% of the total electron density at a distance of 20 solar radii, the strahl bulk velocity and strahl temperature parallel to the background magnetic field stay approximately constant beyond a distance of 15 solar radii, and <jats:italic>β</jats:italic> <jats:sub>∥<jats:italic>s</jats:italic> </jats:sub> (i.e., the ratio of the strahl parallel thermal pressure to the magnetic pressure) is approximately constant with heliocentric distance at a value of about 0.02. We compare our results with data measured by the Parker Solar Probe. Furthermore, we provide theoretical evidence that the electron strahl is not scattered by the oblique fast-magnetosonic/whistler instability in the near-Sun environment.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Kilonovae are ultraviolet, optical, and infrared transients powered by the radioactive decay of heavy elements following a neutron star merger. Joint observations of kilonovae and gravitational waves can offer key constraints on the source of Galactic <jats:italic>r</jats:italic>-process enrichment, among other astrophysical topics. However, robust constraints on heavy element production require rapid kilonova detection (within ∼1 day of merger) as well as multiwavelength observations across multiple epochs. In this study, we quantify the ability of 13 wide-field-of-view instruments to detect kilonovae, leveraging a large grid of over 900 radiative transfer simulations with 54 viewing angles per simulation. We consider both current and upcoming instruments, collectively spanning the full kilonova spectrum. The Roman Space Telescope has the highest redshift reach of any instrument in the study, observing kilonovae out to <jats:italic>z</jats:italic> ∼ 1 within the first day post-merger. We demonstrate that BlackGEM, DECam, GOTO, the Vera C. Rubin Observatory’s LSST, ULTRASAT, VISTA, and WINTER can observe some kilonovae out to <jats:italic>z</jats:italic> ∼ 0.1 (∼475 Mpc), while DDOTI, MeerLICHT, PRIME, Swift/UVOT, and ZTF are confined to more nearby observations. Furthermore, we provide a framework to infer kilonova ejecta properties following nondetections and explore variation in detectability with these ejecta parameters.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We take advantage of the publicly available LEGA-C spectroscopic survey to measure the stellar population properties of 140 individual massive and passive galaxies at <jats:italic>z</jats:italic> ∼ 0.7. We develop and publicly release <jats:monospace>PyLick</jats:monospace>, a flexible Python code to measure UV to near-IR spectral indices. With <jats:monospace>PyLick</jats:monospace> we study the H/K ratio as a new diagnostic based on the pseudo-Lick Ca <jats:sc>ii</jats:sc> H and K indices and find that a cut in H/K &lt; 1.1 can be used jointly with other criteria to select (or verify the purity of) samples of passive galaxies. By combining photometric and spectroscopic criteria, we select a reliable sample of passively evolving galaxies. We constrain single-burst stellar ages, metallicities [Z/H], and [<jats:italic>α</jats:italic>/Fe] with an optimized set of Lick indices, exploring in detail the robustness of our measurement against different combinations. Even without imposing cosmological priors, the derived ages follow a clear trend compatible with the expected cosmological aging of the universe. We observe no significant redshift evolution for the metal abundance with respect to the values derived at <jats:italic>z</jats:italic> = 0, with median [Z/H] = 0.08 ± 0.18 and [<jats:italic>α</jats:italic>/Fe] = 0.13 ± 0.11. Finally, we analyze the relations between log age, [Z/H], [<jats:italic>α</jats:italic>/Fe], and the stellar velocity dispersion, finding slopes of (0.5 ± 0.1), (0.3 ± 0.2), and (0.2 ± 0.1), respectively; the small scatter of &lt;0.2 dex points to rather homogeneous and short star formation histories. Overall, these results confirm and extend low-redshift findings of a mass-downsizing evolution. This work further strengthens the possibility of selecting pure samples of passive galaxies to be exploited reliably as cosmic chronometers to place independent cosmological constraints.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Current observational facilities have yet to conclusively detect 10<jats:sup>3</jats:sup>–10<jats:sup>4</jats:sup> <jats:italic> M</jats:italic> <jats:sub>⊙</jats:sub> intermediate-mass black holes (IMBHs) that fill in the evolutionary gap between seed black holes in the early universe and <jats:italic>z</jats:italic> ∼ 0 supermassive black holes. Dwarf galaxies present an opportunity to reveal active IMBHs amidst persistent star formation. We introduce photoionization simulations tailored to address key physical uncertainties: coincident versus noncoincident mixing of IMBH and starlight excitation, open versus closed geometries of surrounding gas clouds, and different shapes of the spectral energy distribution of active galactic nuclei (AGN). We examine possible AGN emission line diagnostics in the optical and mid-IR, and find that the diagnostics are often degenerate with respect to the investigated physical uncertainties. In spite of these setbacks, and in contrast to recent work, we are able to show that [O <jats:sc>iii</jats:sc>]/H<jats:italic>β</jats:italic> typically remains bright for dwarf AGN powered by IMBHs down to 10<jats:sup>3</jats:sup> <jats:italic> M</jats:italic> <jats:sub>⊙</jats:sub>. Dwarf AGN are predicted to have inconsistent star-forming and Seyfert/LINER classifications using the most common optical diagnostics. In the mid-IR, [O <jats:sc>iv</jats:sc>] 25.9 <jats:italic>μ</jats:italic>m and [Ar <jats:sc>ii</jats:sc>] 6.98 <jats:italic>μ</jats:italic>m are less sensitive to physical uncertainties than are optical diagnostics. Based on these emission lines, we provide several diagrams of mid-IR emission line diagnostic diagrams with demarcations for separating starbursts and AGN with varying levels of activity. The diagrams are valid over a wide range of ionization parameters and metallicities out to <jats:italic>z</jats:italic> ∼ 0.1, so will prove useful for future JWST observations of local dwarf AGN in the search for IMBHs. We make our photoionization simulation suite freely available.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a detailed spectral and imaging analysis of the central 15″ radius (∼7.5 kpc) region of the merger galaxy NGC 6240 that makes use of all the available Chandra-ACIS data (0.3–3 keV effective exposure of ∼190 ks). This region shows extended X-ray structures with lower-energy counterparts imaged in CO, [O <jats:sc>iii</jats:sc>], and H<jats:italic>α</jats:italic> line emission. We find both photoionized phases of possible nuclear excitation and thermal shock-excited emission in the different large-scale components: the northwest “loop” detected in H<jats:italic>α</jats:italic>, the region surrounding the two nuclei, the large outflow region to the northeast detected in [O <jats:sc>iii</jats:sc>], and the southern X-ray extensions. The latter could be the ionization cone of the northern nucleus, with the N counterpart being obscured by the galaxy disk. The radial distribution of the X-ray surface brightness suggests a confined hot interstellar medium at <jats:italic>r</jats:italic> &lt; 2.5 kpc, with a free-flowing wind at larger radii; if the confinement is magnetic, we estimate <jats:italic>B</jats:italic>-field values of ∼100 <jats:italic>μ</jats:italic>G, similar to those measured in the halo of M82. The thermal gas of the extended halo at <jats:italic>kT</jats:italic> ∼ 1 keV absorbs soft X-rays from the active galactic nucleus, but not the extreme ultraviolet radiation leading to a rapid increase in <jats:italic>F</jats:italic> <jats:sub>[O <jats:sc>III</jats:sc>]</jats:sub>/<jats:italic>F</jats:italic> <jats:sub>X</jats:sub> beyond ∼3 kpc. The <jats:italic>α</jats:italic>-element to Fe abundance ratios of the thermal components in the different regions of the extended X-ray emission are generally compatible with Type II supernova yields, confirming the importance of active star formation in NGC 6240.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This paper presents a correction to the scaling relations for red giant stars using model-based masses and radii. We measure radial-mode frequencies from Kepler observations for 3642 solar-like oscillators on the red giant branch and use them to characterize the stars with grid-based modeling. We determine fundamental stellar parameters with good precision: the typical uncertainty is 4.5% for mass, 16% for age, 0.006 dex for surface gravity, and 1.7% for radius. We also achieve good accuracy for estimated masses and radii, based on a comparison with those determined for eclipsing binaries. We find a systematic offset of ∼15% in mass and ∼7% in radius between the modeling solutions and the scaling relations. Further investigation indicates that these offsets are mainly caused by a systematic bias in the Δ<jats:italic>ν</jats:italic> scaling relation: the original scaling relation underestimates the Δ<jats:italic>ν</jats:italic> value by ∼4%, on average, and it is important to correct for the surface term in the calibration. We find no significant offset in the <jats:inline-formula> <jats:tex-math> <?CDATA ${\nu }_{\max }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>ν</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>max</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac4fbfieqn1.gif" xlink:type="simple" /> </jats:inline-formula> scaling relation, although a clear metallicity dependence is seen and we suggest including a metallicity term in the formulae. Lastly, we calibrate new scaling relations for red giant stars based on observed global seismic parameters, spectroscopic effective temperatures and metallicities, and modeling-inferred masses and radii.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The trajectories since <jats:italic>z</jats:italic> = 4 of systems of galaxies (“halos”) with <jats:italic>cz</jats:italic> &lt; 8000 km s<jats:sup>−1</jats:sup> are found through numerical action reconstructions. A set of 9719 halos from a Two Micron All Sky Survey group catalog and Cosmicflows-3 catalogs are given attention. Present distances are adjusted to minimize departures from observed redshifts. For those with the most precisely determined distances, compromises are made between distance and redshift agreement. <jats:italic>H</jats:italic> <jats:sub>0</jats:sub> is varied from 69 to 77 km s<jats:sup>−1</jats:sup> Mpc<jats:sup>−1</jats:sup>, with Ω<jats:sub> <jats:italic>m</jats:italic> </jats:sub> set by the baryon acoustic oscillation constraint from the Planck satellite. A best-fitting amplitude of the mass-to-light relation is found. A uniform density associated with the interhalo medium accounts for the matter not in halos. The solution paths provide the histories of the formation of the nearby large structures and depict how the voids emptied. Assuming no local over/underdensity, the best model has <jats:italic>H</jats:italic> <jats:sub>0</jats:sub> = 73 km s<jats:sup>−1</jats:sup> Mpc<jats:sup>−1</jats:sup>, with nearly the same density arising from interhalo matter (IHM) as from halos. We examine local over/underdensities by varying the IHM density and find a valley of best-fit models along <jats:italic>H</jats:italic> <jats:sub>0</jats:sub> = 73.0(1 + 0.165<jats:italic>δ</jats:italic>) km s<jats:sup>−1</jats:sup> Mpc<jats:sup>−1</jats:sup>. Friedmann models with distinct densities internal and external to the study region give a similar relationship. The fraction of matter in the IHM seen in <jats:italic>n</jats:italic>-body simulations roughly matches that in our <jats:italic>H</jats:italic> <jats:sub>0</jats:sub> = 72 scenario. Videos have been created to visualize the complexities of formation of large-scale structures. Standard <jats:italic>n</jats:italic>-body calculations, starting from the first time steps as tests of the numerical action method solutions and continuing until cosmic scale factor <jats:italic>a</jats:italic> = 2, provide glimpses into the future.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>With the aim of unraveling the complexity of the morphokinematics of the circumstellar envelope (CSE) of Mira Ceti, we review, extend, and in some cases revisit Atacama Large Millimeter/submillimeter Array observations of the emission of the SiO(5–4) and CO(3–2) molecular lines. In addition, we present a detailed analysis of the optically thin <jats:sup>13</jats:sup>CO(3–2) emission, which provides several important new results. In agreement with observations at infrared and visible wavelengths, we give evidence for the confinement and probably rotation of a dense gas volume within ∼50 au from the star and for a large SiO line width within ∼15 au. We show that the mass-loss process is episodic and takes the form of clumps having a very low SiO/CO abundance ratio compared with similar oxygen-rich long-period variables, probably a result of depletion on dust grains and photodissociation. We evaluate the mass-loss rate associated with the main clumps and compare it with values obtained from single-dish observations. We argue that the SiO emission observed in the southwestern quadrant is not related to the mechanism of generation of the nascent wind but to a mass ejection that occurred 11 years before the observations. We remark that Mira Ceti is not a good archetype in terms of its wind: models aiming at describing the very complex gas-dust chemistry in action in the CSE of oxygen-rich AGB stars may find it difficult to account for its peculiar features and small variations in the parameters deciding when and where mass loss can proceed significantly.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a detailed stellar population analysis of 11 bright (<jats:italic>H</jats:italic> &lt; 26.6) galaxies at <jats:italic>z</jats:italic> = 9–11 (three spectroscopically confirmed) to constrain the chemical enrichment and growth of stellar mass of early galaxies. We use the flexible Bayesian spectral energy distribution (SED) fitting code <jats:monospace>Prospector</jats:monospace> with a range of star formation histories (SFHs), a flexible dust attenuation law, and a self-consistent model of emission lines. This approach allows us to assess how different priors affect our results and how well we can break degeneracies between dust attenuation, stellar ages, metallicity, and emission lines using data that probe only the rest-frame ultraviolet (UV) to optical wavelengths. We measure a median observed UV spectral slope <jats:inline-formula> <jats:tex-math> <?CDATA $\beta =-{1.87}_{-0.43}^{+0.35}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>β</mml:mi> <mml:mo>=</mml:mo> <mml:mo>−</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>1.87</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.43</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.35</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac4cadieqn1.gif" xlink:type="simple" /> </jats:inline-formula> for relatively massive star-forming galaxies (<jats:inline-formula> <jats:tex-math> <?CDATA $9\lt \mathrm{log}({M}_{\star }/{M}_{\odot })\lt 10$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>9</mml:mn> <mml:mo>&lt;</mml:mo> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⋆</mml:mo> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> <mml:mo>&lt;</mml:mo> <mml:mn>10</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac4cadieqn2.gif" xlink:type="simple" /> </jats:inline-formula>), consistent with no change from <jats:italic>z</jats:italic> = 4 to <jats:italic>z</jats:italic> = 9–10 at these stellar masses, implying rapid enrichment. Our SED-fitting results are consistent with a star-forming main sequence with sublinear slope (0.7 ± 0.2) and specific star formation rates of 3–10 Gyr<jats:sup>−1</jats:sup>. However, the stellar ages and SFHs are less well constrained. Using different SFH priors, we cannot distinguish between median mass-weighted ages of ∼ 50–150 Myr, which corresponds to 50% formation redshifts of <jats:italic>z</jats:italic> <jats:sub>50</jats:sub> ∼ 10–12 at <jats:italic>z</jats:italic> ∼ 9 and is of the order of the dynamical timescales of these systems. Importantly, models with different SFH priors are able to fit the data equally well. We conclude that the current observational data cannot tightly constrain the mass-buildup timescales of these <jats:italic>z</jats:italic> = 9–11 galaxies, with our results consistent with SFHs implying both a shallow and steep increase in the cosmic SFR density with time at <jats:italic>z</jats:italic> &gt; 10.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>One Martian induced magnetosphere boundary (IMB) crossing at the subsolar region is analyzed here with multiple instruments on board MAVEN. Properties of the magnetic field and particles around the IMB are evaluated. We find different trends of variation in magnetic field components at the two sides of an interface coincident with the previously defined ion composition boundary. This case shows the IMB at the Martian dayside could be divided into three parts: two regions (denoted as R1 and R2), with different field and plasma properties, and an interface between them. Currents found in R1 and R2 are flowing in antiparallel, and the current density in R2 (at lower altitude) is significantly larger than that in R1 (at higher altitude). Results indicate the interaction between Mars and the solar wind could induce strong currents in the IMB, which are with antiparallel current directions and separated by an interface where the ion composition changes. This could be a typical feature that occurred during the interaction between the solar wind and the nonmagnetized planets.</jats:p>