Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Interstellar dust extinction curves provide valuable information about dust properties, including the composition and size of the dust grains, and are essential to correct observations for the effects of interstellar dust. In this work, we measure a representative sample of near-infrared (NIR; 0.8–5.5 <jats:italic>μ</jats:italic>m) spectroscopic extinction curves for the first time, enabling us to investigate the extinction at wavelengths where it is usually only measured in broad photometric bands. We use IRTF/SpeX spectra of a sample of reddened and comparison stars to measure 15 extinction curves with the pair method. Our sample spans <jats:italic>A</jats:italic>(<jats:italic>V</jats:italic>) values from 0.78 to 5.65 and <jats:italic>R</jats:italic>(<jats:italic>V</jats:italic>) values from 2.43 to 5.33. We confirm that the NIR extinction curves are well fit by a power law, with indices and amplitudes differing from sight line to sight line. Our average diffuse NIR extinction curve can be represented by a single power law with index <jats:italic>α</jats:italic> = 1.7, but because of the sight line-to-sight line variations, the shape of any average curve will depend on the parental sample. We find that most of the variation in our sample can be linked to the ratio of total-to-selective extinction <jats:italic>R</jats:italic>(<jats:italic>V</jats:italic>), a rough measurement of the average dust grain size. Two sight lines in our sample clearly show the ice extinction feature at 3 <jats:italic>μ</jats:italic>m, which can be fitted by a modified Drude profile. We find tentative ice detections with slightly over 3<jats:italic>σ</jats:italic> significance in two other sight lines. In our average diffuse extinction curve, we measure a 3<jats:italic>σ</jats:italic> upper limit of <jats:italic>A</jats:italic>(ice)/<jats:italic>A</jats:italic>(<jats:italic>V</jats:italic>) = 0.0021 for this ice feature.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Massive, star-forming clumps are a common feature of high-redshift star-forming galaxies. How they formed, and why they are so rare at low redshift, remains unclear. In this paper we identify the largest sample yet of clumpy galaxies (7050) at low redshift using data from the citizen science project Galaxy Zoo: Clump Scout, in which volunteers classified 58,550 Sloan Digital Sky Survey (SDSS) galaxies spanning redshift 0.02 &lt; <jats:italic>z</jats:italic> &lt; 0.15. We apply a robust completeness correction by comparing with simulated clumps identified by the same method. Requiring that the ratio of clump to galaxy flux in the SDSS <jats:italic>u</jats:italic> band be greater than 8% (similar to clump definitions used by other works), we estimate the fraction of local star-forming galaxies hosting at least one clump (<jats:italic>f</jats:italic> <jats:sub>clumpy</jats:sub>) to be <jats:inline-formula> <jats:tex-math> <?CDATA ${3.22}_{-0.34}^{+0.38} \% $?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>3.22</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.34</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.38</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>%</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac6512ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>. We also compute the same fraction with a less stringent relative flux cut of 3% (<jats:inline-formula> <jats:tex-math> <?CDATA ${12.68}_{-0.88}^{+1.38} \% $?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>12.68</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.88</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>1.38</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>%</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac6512ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>), as the higher number count and lower statistical noise of this fraction permit finer comparison with future low-redshift clumpy galaxy studies. Our results reveal a sharp decline in <jats:italic>f</jats:italic> <jats:sub>clumpy</jats:sub> over 0 &lt; <jats:italic>z</jats:italic> &lt; 0.5. The minor merger rate remains roughly constant over the same span, so we suggest that minor mergers are unlikely to be the primary driver of clump formation. Instead, the rate of galaxy turbulence is a better tracer for <jats:italic>f</jats:italic> <jats:sub>clumpy</jats:sub> over 0 &lt; <jats:italic>z</jats:italic> &lt; 1.5 for galaxies of all masses, which supports the idea that clump formation is primarily driven by violent disk instability for all galaxy populations during this period.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>To study the demographics of interstellar ices in the Central Molecular Zone (CMZ) of the Milky Way, we obtain near-infrared spectra of 109 red point sources using NASA IRTF/SpeX at Maunakea. We select the sample from near- and mid-infrared photometry, including 12 objects in the previous paper of this series, to ensure that these sources trace a large amount of absorption through clouds in each line of sight. We find that most of the sample (100 objects) show CO band-head absorption at 2.3 <jats:italic>μ</jats:italic>m, tagging them as red (super-) giants. Despite the photospheric signature, however, a fraction of the sample with <jats:italic>L</jats:italic>-band spectra (9/82 = 0.11) exhibit large H<jats:sub>2</jats:sub>O ice column densities (<jats:italic>N</jats:italic> &gt; 2 × 10<jats:sup>18</jats:sup> cm<jats:sup>−2</jats:sup>), and six of them also reveal CH<jats:sub>3</jats:sub>OH ice absorption. As one of such objects is identified as a young stellar object (YSO) in our previous work, these ice-rich sight lines are likely associated with background stars in projection to an extended envelope of a YSO or a dense cloud core. The low frequency of such objects in the early stage of stellar evolution implies a low star-formation rate (≲0.02 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup>), reinforcing the previous claim on the suppressed star-formation activity in the CMZ. Our data also indicate that the strong “shoulder” CO<jats:sub>2</jats:sub> ice absorption at 15.4 <jats:italic>μ</jats:italic>m observed in YSO candidates in the previous paper arises from CH<jats:sub>3</jats:sub>OH-rich ice grains having a large CO<jats:sub>2</jats:sub> concentration [<jats:italic>N</jats:italic>(CO<jats:sub>2</jats:sub>)/<jats:italic>N</jats:italic>(CH<jats:sub>3</jats:sub>OH) ≈ 1/3].</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Gravitational-wave detectors are starting to reveal the redshift evolution of the binary black hole (BBH) merger rate, <jats:italic>R</jats:italic> <jats:sub>BBH</jats:sub>(<jats:italic>z</jats:italic>). We make predictions for <jats:italic>R</jats:italic> <jats:sub>BBH</jats:sub>(<jats:italic>z</jats:italic>) as a function of black hole mass for systems originating from isolated binaries. To this end, we investigate correlations between the delay time and black hole mass by means of the suite of binary population synthesis simulations, <jats:monospace>COMPAS</jats:monospace>. We distinguish two channels: the common envelope (CE), and the stable Roche-lobe overflow (RLOF) channel, characterized by whether the system has experienced a common envelope or not. We find that the CE channel preferentially produces BHs with masses below about 30 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> and short delay times (<jats:italic>t</jats:italic> <jats:sub>delay</jats:sub> ≲ 1 Gyr), while the stable RLOF channel primarily forms systems with BH masses above 30 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> and long delay times (<jats:italic>t</jats:italic> <jats:sub>delay</jats:sub> ≳ 1 Gyr). We provide a new fit for the metallicity-dependent specific star formation rate density based on the Illustris TNG simulations, and use this to convert the delay time distributions into a prediction of <jats:italic>R</jats:italic> <jats:sub>BBH</jats:sub>(<jats:italic>z</jats:italic>). This leads to a distinct redshift evolution of <jats:italic>R</jats:italic> <jats:sub>BBH</jats:sub>(<jats:italic>z</jats:italic>) for high and low primary BH masses. We furthermore find that, at high redshift, <jats:italic>R</jats:italic> <jats:sub>BBH</jats:sub>(<jats:italic>z</jats:italic>) is dominated by the CE channel, while at low redshift, it contains a large contribution (∼40%) from the stable RLOF channel. Our results predict that, for increasing redshifts, BBHs with component masses above 30 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> will become increasingly scarce relative to less massive BBH systems. Evidence of this distinct evolution of <jats:italic>R</jats:italic> <jats:sub>BBH</jats:sub>(<jats:italic>z</jats:italic>) for different BH masses can be tested with future detectors.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The general behavior of the nuclear equation of state (EOS), relevant for the description of neutron stars (NSs), is studied within a Bayesian approach applied to a set of models based on a density-dependent relativistic mean-field description of nuclear matter. The EOS is subjected to a minimal number of constraints based on nuclear saturation properties and the low-density pure neutron matter EOS obtained from a precise next-to-next-to-next-to-leading order (N<jats:sup>3</jats:sup>LO) calculation in chiral effective field theory (<jats:italic>χ</jats:italic>EFT). The posterior distributions of the model parameters obtained under these minimal constraints are employed to construct the distributions of various nuclear matter properties and NS properties such as radii, tidal deformabilities, central energy densities, speeds of sound, etc. We found that a 90% confidence interval for the allowed NS mass–radius relationship and tidal deformabilities is compatible with GW170817 and recent Neutron star Interior Composition ExploreR observations, without invoking the exotic degrees of freedom. A central speed of sound of the order of <jats:inline-formula> <jats:tex-math> <?CDATA $\sqrt{2/3}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msqrt> <mml:mrow> <mml:mn>2</mml:mn> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> </mml:msqrt> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac5d3cieqn1.gif" xlink:type="simple" /> </jats:inline-formula> <jats:italic>c</jats:italic> is obtained. The maximum NS mass allowed by the model is 2.5 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Spacecraft observations around Mars show that ionospheric irregularities occur frequently in the Martian ionosphere. In this study, Mars Atmosphere and Volatile Evolution data (the region is below ∼200 km) during 2015 January to 2021 March were used to revisit the statistical characteristics of ionospheric irregularities and the comparison of irregularities in Martian years with higher or lower solar activity phase of solar cycle. Results show that the characteristics of the irregularities with a larger length scale associated with the magnetic field and solar zenith angle are similar to the previous studies. Moreover, our results show that the occurrence rate of irregularities exhibits dawn and dusk asymmetry, and the occurrence rate at dusk is higher than that at dawn. In addition, results demonstrate that the occurrence rate of irregularities is higher in Martian years with higher solar activity than Martian years with lower solar activity, which means that the solar cycle might play an important role in the formation of irregularity events. Further studies show that the solar zenith angle (SZA) and altitude at the maximum occurrence rate depend on the level of solar activity. The SZA and altitude of the maximum occurrence rate are smaller in the Martian year with higher solar activity than the lower. We also found that the rate of events is lower during the day than the terminator in the ionospheric dynamo region. By contrast, in the regions where both electrons and ions are magnetized, events have a higher rate during the day than the terminator. Furthermore, the seasonal variation of the irregularity events was also presented in this study. Results show that the occurrence rate in the dynamo region with 80° &lt; SZA &lt; 150° in MY34 and MY35 show an incremental trend from spring to winter, but this trend is not obvious in MY33.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We perform the first systematic search of all NICER archival observations of black hole (and candidate) low-mass X-ray binaries for signatures of reverberation. Reverberation lags result from the light travel time difference between the direct coronal emission and the reflected disk component, and therefore their properties are a useful probe of the disk-corona geometry. We detect new signatures of reverberation lags in eight sources, increasing the total sample from three to 11, and study the evolution of reverberation lag properties as the sources evolve in outbursts. We find that in all of the nine sources with more than one reverberation lag detection, the reverberation lags become longer and dominate at lower Fourier frequencies during the hard-to-soft state transition. This result shows that the evolution in reverberation lags is a global property of the state transitions of black hole low-mass X-ray binaries, which is valuable in constraining models of such state transitions. The reverberation lag evolution suggests that the corona is the base of a jet that vertically expands and/or gets ejected during state transition. We also discover that in the hard state, the reverberation lags get shorter, just as the quasiperiodic oscillations (QPOs) move to higher frequencies, but then in the state transition, while the QPOs continue to higher frequencies, the lags get longer. We discuss the implications of the coronal geometry and physical models of QPOs in light of this new finding.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report on the discovery of a new diffuse stellar substructure protruding for &gt;5° from the northeastern rim of the LMC disk. The structure, which we dub the northeast structure (NES), was identified by applying a Gaussian mixture model to a sample of strictly selected candidate members of the Magellanic System, extracted from the Gaia EDR3 catalog. The NES fills the gap between the outer LMC disk and other known structures in the same region of the LMC, namely the northern tidal arm and the eastern substructures. Particularly noteworthy is that the NES is placed in a region where <jats:italic>N</jats:italic>-body simulations foresee a bending of the LMC disk due to tidal stresses induced by the MW. The velocity field in the plane of the sky indicates that the complex of tidal structures in the northeastern part of the LMC, including NES, shows a complex pattern. Additional data, as well as extensive dynamical modeling, is required to shed light onto the origin of NES as well as on the relationships with the surrounding substructures.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The prospect of combining integral field spectroscopy with the solar gravitational lens (SGL) to spectrally and spatially resolve the surfaces and atmospheres of extrasolar planets is investigated. The properties of hyperbolic orbits visiting the focal region of the SGL are calculated analytically, demonstrating trade-offs between departure velocity and time of arrival, as well as gravity assist maneuvers and heliocentric angular velocity. Numerical integration of the solar barycentric motion demonstrates that navigational acceleration of <jats:inline-formula> <jats:tex-math> <?CDATA ${dv}\lesssim 80\tfrac{{\rm{m}}}{{\rm{s}}}+6.7\tfrac{{\rm{m}}}{{\rm{s}}}\tfrac{t}{\mathrm{year}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="italic">dv</mml:mi> <mml:mo>≲</mml:mo> <mml:mn>80</mml:mn> <mml:mstyle displaystyle="false"> <mml:mfrac> <mml:mrow> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">s</mml:mi> </mml:mrow> </mml:mfrac> </mml:mstyle> <mml:mo>+</mml:mo> <mml:mn>6.7</mml:mn> <mml:mstyle displaystyle="false"> <mml:mfrac> <mml:mrow> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">s</mml:mi> </mml:mrow> </mml:mfrac> </mml:mstyle> <mml:mstyle displaystyle="false"> <mml:mfrac> <mml:mrow> <mml:mi>t</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>year</mml:mi> </mml:mrow> </mml:mfrac> </mml:mstyle> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac5e9dieqn1.gif" xlink:type="simple" /> </jats:inline-formula> is needed to obtain and maintain alignment. Obtaining target ephemerides of sufficient precision is an open problem. The optical properties of an oblate gravitational lens are reviewed, including calculations of the magnification and the point-spread function that forms inside a telescope. Image formation for extended, incoherent sources is discussed when the projected image is smaller than, approximately equal to, and larger than the critical caustic. Sources of contamination that limit observational signal-to-noise ratio (S/N) are considered in detail, including the Sun, the solar corona, the host star, and potential background objects. A noise mitigation strategy of spectrally and spatially separating the light using integral field spectroscopy is emphasized. A pseudo-inverse-based image reconstruction scheme demonstrates that direct reconstruction of an Earth-like source from <jats:italic>single</jats:italic> measurements of the Einstein ring is possible when the critical caustic and observed S/N are sufficiently large. In this arrangement, a mission would not require multiple telescopes or navigational symmetry breaking, enabling continuous monitoring of the atmospheric composition and dynamics on other planets.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The X-ray emission from a supernova remnant is a powerful diagnostic of the state of its shocked plasma. The temperature and the emission measure are related to the energy of the explosion, the age of the remnant, and the density of the surrounding medium. Here we present the results of a study of the remnant population of the Small Magellanic Cloud. Progress in X-ray observations of remnants has resulted in a sample of 20 remnants in the Small Magellanic Cloud with measured temperatures and emission measures. We apply spherically symmetric supernova remnant evolution models to this set of remnants to estimate ages, explosion energies, and circumstellar medium densities. The distribution of ages yields a remnant birth rate of ∼1/1200 yr. The energies and densities are well fit with log-normal distributions, with means of 1.6 × 10<jats:sup>51</jats:sup> erg and 0.14 cm<jats:sup>−3</jats:sup>, and 1<jats:italic>σ</jats:italic> dispersions of a factor of 1.87 in energy and 3.06 in density, respectively.</jats:p>