Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We study the evolution of the binary black hole (BBH) mass distribution across cosmic time. The second gravitational-wave transient catalog (GWTC-2) from LIGO/Virgo contains BBH events out to redshifts <jats:italic>z</jats:italic> ∼ 1, with component masses in the range ∼5–80 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. In this catalog, the biggest BBHs, with <jats:italic>m</jats:italic> <jats:sub>1</jats:sub> ≳ 45 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, are only found at the highest redshifts, <jats:italic>z</jats:italic> ≳ 0.4. We ask whether the absence of high-mass observations at low redshift indicates that the mass distribution evolves: the biggest BBHs only merge at high redshift, and cease merging at low redshift. Modeling the BBH primary-mass spectrum as a power law with a sharp maximum mass cutoff (<jats:sc>Truncated</jats:sc> model), we find that the cutoff increases with redshift (&gt; 99.9% credibility). An abrupt cutoff in the mass spectrum is expected from (pulsational) pair-instability supernova simulations; however, GWTC-2 is only consistent with a <jats:sc>Truncated</jats:sc> mass model if the location of the cutoff increases from <jats:inline-formula> <jats:tex-math> <?CDATA ${45}_{-5}^{+13}\,{M}_{\odot }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabee11ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> at <jats:italic>z</jats:italic> &lt; 0.4 to <jats:inline-formula> <jats:tex-math> <?CDATA ${80}_{-13}^{+16}\,{M}_{\odot }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabee11ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> at <jats:italic>z</jats:italic> &gt; 0.4. Alternatively, if the primary-mass spectrum has a break in the power law (<jats:sc>Broken Power Law</jats:sc>) at <jats:inline-formula> <jats:tex-math> <?CDATA ${38}_{-8}^{+15}\,{M}_{\odot }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabee11ieqn3.gif" xlink:type="simple" /> </jats:inline-formula>, rather than a sharp cutoff, the data are consistent with a nonevolving mass distribution. In this case, the overall rate of mergers, at all masses, increases with redshift. Future observations will distinguish between a sharp mass cutoff that evolves with redshift and a nonevolving mass distribution with a gradual taper, such as a <jats:sc>Broken Power Law</jats:sc>. After ∼100 BBH merger observations, a continued absence of high-mass, low-redshift events would provide a clear signature that the mass distribution evolves with redshift.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This article aims to draw the attention of astronomers to the ability of future cosmological surveys to put constraints on string theory. The fact that “quantum gravity” might be constrained by large-scale astrophysical observations is a remarkable fact that has recently concentrated a great amount of interest. In this work, we focus on future observatories and investigate their capability to put string theory, which is sometimes said to be “unfalsifiable,” under serious pressure. We show that the combined analysis of the Square Kilometer Array, Euclid, and the Vera Rubin observatory—together with Planck results—could substantially improve the current limits on the relevant string swampland parameter. In particular, our analysis leads to a nearly model-independent prospective upper bound on the quintessence potential, <jats:inline-formula> <jats:tex-math> <?CDATA $| V^{\prime} | /V\lt 0.16$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabedbeieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, in strong contradiction of the so-called de Sitter conjecture. Some lines of improvements for the very long run are also drawn, together with generic prospective results, underscoring the efficiency of this approach. The conjectures used in this work are discussed pedagogically, together with the cosmological models chosen in the analysis.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this work, we measure the Ly<jats:italic>α</jats:italic> escape fraction of 935 [O <jats:sc>iii</jats:sc>]-emitting galaxies between 1.9 &lt; <jats:italic>z</jats:italic> &lt; 2.35 by comparing stacked spectra from the Hubble Space Telescope/WFC3's near-IR grism to corresponding stacks from the Hobby–Eberly Telescope Dark Energy Experiment’s Internal Data Release 2. By measuring the stacks’ H<jats:italic>β</jats:italic> to Ly<jats:italic>α</jats:italic> ratios, we determine the Ly<jats:italic>α</jats:italic> escape fraction as a function of stellar mass, star-formation rate, internal reddening, size, and [O <jats:sc>iii</jats:sc>]/H<jats:italic>β</jats:italic> ratio. We show that the escape fraction of Ly<jats:italic>α</jats:italic> correlates with a number of parameters, such as galaxy size, star-formation rate, and nebular excitation. However, we also demonstrate that most of these relations are indirect, and that the primary variables controlling the escape of Ly<jats:italic>α</jats:italic> are likely to be stellar mass and internal extinction. Overall, the escape of Ly<jats:italic>α</jats:italic> declines from ≳16% in galaxies with <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}M/{M}_{\odot }\lesssim 9$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabedb9ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> to ≲1% for systems with <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}M/{M}_{\odot }\gtrsim 10$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabedb9ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>, with the sample’s mean escape fraction being <jats:inline-formula> <jats:tex-math> <?CDATA ${6.0}_{-0.5 \% }^{+0.6 \% }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabedb9ieqn3.gif" xlink:type="simple" /> </jats:inline-formula>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We use fluctuating magnetic helicity to investigate the polarization properties of Alfvénic fluctuations at ion-kinetic scales in the solar wind as a function of <jats:italic>β</jats:italic> <jats:sub> <jats:italic>p</jats:italic> </jats:sub>, the ratio of proton thermal pressure to magnetic pressure, and <jats:italic>θ</jats:italic> <jats:sub> <jats:italic>vB</jats:italic> </jats:sub>, the angle between the proton flow and local mean magnetic field, <jats:bold> <jats:italic>B</jats:italic> </jats:bold> <jats:sub>0</jats:sub>. Using almost 15 yr of Wind observations, we separate the contributions to helicity from fluctuations with wavevectors, <jats:bold> <jats:italic>k</jats:italic> </jats:bold>, quasi-parallel and oblique to <jats:bold> <jats:italic>B</jats:italic> </jats:bold> <jats:sub>0</jats:sub>, finding that the helicity of Alfvénic fluctuations is consistent with predictions from linear Vlasov theory. This result suggests that the nonlinear turbulent fluctuations at these scales share at least some polarization properties with Alfvén waves. We also investigate the dependence of proton temperature in the <jats:italic>β</jats:italic> <jats:sub> <jats:italic>p</jats:italic> </jats:sub>–<jats:italic>θ</jats:italic> <jats:sub> <jats:italic>vB</jats:italic> </jats:sub> plane to probe for possible signatures of turbulent dissipation, finding that it correlates with <jats:italic>θ</jats:italic> <jats:sub> <jats:italic>vB</jats:italic> </jats:sub>. The proton temperature parallel to <jats:bold> <jats:italic>B</jats:italic> </jats:bold> <jats:sub>0</jats:sub> is higher in the parameter space where we measure the helicity of right-handed Alfvénic fluctuations, and the temperature perpendicular to <jats:bold> <jats:italic>B</jats:italic> </jats:bold> <jats:sub>0</jats:sub> is higher where we measure left-handed fluctuations. This finding is inconsistent with the general assumption that by sampling different <jats:italic>θ</jats:italic> <jats:sub> <jats:italic>vB</jats:italic> </jats:sub> in the solar wind we can analyze the dependence of the turbulence distribution on <jats:italic>θ</jats:italic> <jats:sub> <jats:italic>kB</jats:italic> </jats:sub>, the angle between <jats:bold> <jats:italic>k</jats:italic> </jats:bold> and <jats:bold> <jats:italic>B</jats:italic> </jats:bold> <jats:sub>0</jats:sub>. After ruling out both instrumental and expansion effects, we conclude that our results provide new evidence for the importance of local kinetic processes that depend on <jats:italic>θ</jats:italic> <jats:sub> <jats:italic>vB</jats:italic> </jats:sub> in determining proton temperature in the solar wind.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>As ancient, gravitationally bound stellar populations, globular clusters represent abundant, vibrant laboratories, characterized by high frequencies of dynamical interactions, coupled to complex stellar evolution. Using surface brightness and velocity dispersion profiles from the literature, we fit 59 Milky Way globular clusters to dynamical models from the <jats:monospace>CMC Cluster Catalog</jats:monospace>. Without performing any interpolation, and without any directed effort to fit any particular cluster, 26 globular clusters are well matched by at least one of our models. We discuss in particular the core-collapsed clusters NGC 6293, NGC 6397, NGC 6681, and NGC 6624, and the non-core-collapsed clusters NGC 288, NGC 4372, and NGC 5897. As NGC 6624 lacks well-fitting snapshots on the main <jats:monospace>CMC Cluster Catalog</jats:monospace>, we run six additional models in order to refine the fit. We calculate metrics for mass segregation, explore the production of compact object sources such as millisecond pulsars, cataclysmic variables, low-mass X-ray binaries, and stellar-mass black holes, finding reasonable agreement with observations. In addition, closely mimicking observational cuts, we extract the binary fraction from our models, finding good agreement, except in the dense core regions of core-collapsed clusters. Accompanying this paper are a number of <jats:sans-serif>python </jats:sans-serif>methods for examining the publicly accessible <jats:monospace>CMC Cluster Catalog</jats:monospace>, as well as any other models generated using <jats:monospace>CMC</jats:monospace>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a comparative study of four physical dust models and two single-temperature modified blackbody models by fitting them to the resolved WISE, Spitzer, and Herschel photometry of M101 (NGC 5457). Using identical data and a grid-based fitting technique, we compare the resulting dust and radiation field properties derived from the models. We find that the dust mass yielded by the different models can vary by up to a factor of 3 (factor of 1.4 between physical models only), although the fits have similar quality. Despite differences in their definition of the carriers of the mid-IR aromatic features, all physical models show the same spatial variations for the abundance of that grain population. Using the well-determined metallicity gradient in M101 and resolved gas maps, we calculate an approximate upper limit on the dust mass as a function of radius. All physical dust models are found to exceed this maximum estimate over some range of galactocentric radii. We show that renormalizing the models to match the same Milky Way high-latitude cirrus spectrum and abundance constraints can reduce the dust mass differences between models and bring the total dust mass below the maximum estimate at all radii.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this work we explore the power of future large-scale surveys to constrain possible deviations from the standard single-field slow-roll inflationary scenario. Specifically, we parameterize possible fluctuations around the almost scale-invariant primordial scalar power spectrum in a model-independent way. We then use their imprints on the simulated matter distribution, as observed by the galaxy clustering and weak lensing probes of Euclid and the Square Kilometer Array, to construct the best constrainable patterns of fluctuations. For comparison, we make similar forecasts for a futuristic CMB-S4-like survey. The modes are found to have similar, yet shifted, patterns, with increasing number of wiggles as the mode number increases. The forecasted constraints are tightest for cosmic microwave background anisotropies and galaxy clustering, depending on the details of the specifications of the survey. As case studies, we explore how two greatly different physically motivated patterns of primordial power spectrum are reconstructed by the proposed modes. We propose a figure of merit based on the amount of information delivered by the modes to truncate the mode hierarchy, which is automatically generated by the analysis.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Neutron tunneling between neutron-rich nuclei in inhomogeneous dense matter encountered in neutron star crusts can release enormous energy on a short timescale to power explosive phenomena in neutron stars. In this work, we clarify aspects of this process that can occur in the outer regions of neutron stars when oscillations or cataclysmic events increase the ambient density. We use a time-dependent Hartree–Fock–Bogoliubov formalism to determine the rate of neutron diffusion and find that large amounts of energy can be released rapidly. The roles of nuclear binding, two-body interaction, and pairing in neutron diffusion times are investigated. We consider a one-dimensional quantum diffusion model and extend our analysis to study the impact of diffusion in three dimensions. We find that these novel neutron transfer reactions can generate energy in the amount of ≃ 10<jats:sup>40</jats:sup>–10<jats:sup>44</jats:sup> erg under suitable conditions and assumptions.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Using a sample of 96,201 primary red clump stars selected from the LAMOST and Gaia surveys, we investigate the stellar structure of the Galactic disk. The sample stars show two separated sequences of high-[<jats:italic>α</jats:italic>/Fe] and low-[<jats:italic>α</jats:italic>/Fe] in the [<jats:italic>α</jats:italic>/Fe]–[Fe/H] plane. We divide the sample stars into five mono-abundance populations (MAPs) with different ranges of [<jats:italic>α</jats:italic>/Fe] and [Fe/H], named as the high-[<jats:italic>α</jats:italic>/Fe], high-[<jats:italic>α</jats:italic>/Fe] and high-[Fe/H], low-[Fe/H], solar, high-[Fe/H] MAPs, respectively. We present the stellar number density distributions in the <jats:italic>R</jats:italic>–<jats:italic>Z</jats:italic> plane, and the scale heights and scale lengths of the individual MAPs by fitting their vertical and radial density profiles. The vertical profiles, the variation trend of scale height with the Galactocentric radius, indicate that there is a clear disk flare in the outer disk both for the low-[<jats:italic>α</jats:italic>/Fe] and the high-[<jats:italic>α</jats:italic>/Fe] MAPs. While the radial surface-density profiles show a peak radius of 7 kpc and 8 kpc for the high-[<jats:italic>α</jats:italic>/Fe] and low-[<jats:italic>α</jats:italic>/Fe] MAPs, respectively. We also investigate the correlation between the mean rotation velocity and metallicity of the individual MAPs, and find that the mean rotation velocities are well separated and show different trends between the high-[<jats:italic>α</jats:italic>/Fe] and the low-[<jats:italic>α</jats:italic>/Fe] MAPs. Finally, we discuss the character of the high-[<jats:italic>α</jats:italic>/Fe] and high-[Fe/H] MAP and find that it is more similar to the high-[<jats:italic>α</jats:italic>/Fe] MAP either in the radial and vertical density profiles or in the rotation velocity.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Dust gaps and rings appear ubiquitous in bright protoplanetary disks. Disk–planet interaction with dust trapping at the edges of planet-induced gaps is one plausible explanation. However, the sharpness of some observed dust rings indicate that sub-millimeter-sized dust grains have settled to a thin layer in some systems. We test whether or not such dust around gas gaps opened by planets can remain settled by performing three-dimensional, dust-plus-gas simulations of protoplanetary disks with an embedded planet. We find planets massive enough to open gas gaps stir small, sub-millimeter-sized dust grains to high disk elevations at the gap edges, where the dust scale height can reach ∼70% of the gas scale height. We attribute this dust “puff up” to the planet-induced meridional gas flows previously identified by Fung &amp; Chiang and others. We thus emphasize the importance of explicit 3D simulations to obtain the vertical distribution of sub-millimeter-sized grains around gas gaps opened by massive planets. We caution that the gas-gap-opening planet interpretation of well-defined dust rings is only self-consistent with large grains exceeding millimeter size.</jats:p>