Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>The H <jats:sc>i</jats:sc> gas content is a key ingredient in galaxy evolution, the study of which has been limited to moderate cosmological distances for individual galaxies due to the weakness of the hyperfine H <jats:sc>i</jats:sc> 21 cm transition. Here we present a new approach that allows us to infer the H <jats:sc>i</jats:sc> gas mass <jats:italic>M</jats:italic> <jats:sub>HI</jats:sub> of individual galaxies up to <jats:italic>z</jats:italic> ≈ 6, based on a direct measurement of the [C <jats:sc>ii</jats:sc>]-to-H <jats:sc>i</jats:sc> conversion factor in star-forming galaxies at <jats:italic>z</jats:italic> ≳ 2 using <jats:italic>γ</jats:italic>-ray burst afterglows. By compiling recent [C <jats:sc>ii</jats:sc>]-158 <jats:italic>μ</jats:italic>m emission line measurements we quantify the evolution of the H <jats:sc>i</jats:sc> content in galaxies through cosmic time. We find that <jats:italic>M</jats:italic> <jats:sub>HI</jats:sub> starts to exceed the stellar mass <jats:italic>M</jats:italic> <jats:sub>⋆</jats:sub> at <jats:italic>z</jats:italic> ≳ 1, and increases as a function of redshift. The H <jats:sc>i</jats:sc> fraction of the total baryonic mass increases from around 20% at <jats:italic>z</jats:italic> = 0 to about 60% at <jats:italic>z</jats:italic> ∼ 6. We further uncover a universal relation between the H <jats:sc>i</jats:sc> gas fraction <jats:italic>M</jats:italic> <jats:sub>HI</jats:sub>/<jats:italic>M</jats:italic> <jats:sub>⋆</jats:sub> and the gas-phase metallicity, which seems to hold from <jats:italic>z</jats:italic> ≈ 6 to <jats:italic>z</jats:italic> = 0. The majority of galaxies at <jats:italic>z</jats:italic> &gt; 2 are observed to have H <jats:sc>i</jats:sc> depletion times, <jats:italic>t</jats:italic> <jats:sub>dep,HI</jats:sub> = <jats:italic>M</jats:italic> <jats:sub>HI</jats:sub>/SFR, less than ≈2 Gyr, substantially shorter than for <jats:italic>z</jats:italic> ∼ 0 galaxies. Finally, we use the [C <jats:sc>ii</jats:sc>]-to-H <jats:sc>i</jats:sc> conversion factor to determine the cosmic mass density of H <jats:sc>i</jats:sc> in galaxies, <jats:italic>ρ</jats:italic> <jats:sub>HI</jats:sub>, at three distinct epochs: <jats:italic>z</jats:italic> ≈ 0, <jats:italic>z</jats:italic> ≈ 2, and <jats:italic>z</jats:italic> ∼ 4–6. These measurements are consistent with previous estimates based on 21 cm H <jats:sc>i</jats:sc> observations in the local universe and with damped Ly<jats:italic>α</jats:italic> absorbers (DLAs) at <jats:italic>z</jats:italic> ≳ 2, suggesting an overall decrease by a factor of ≈5 in <jats:italic>ρ</jats:italic> <jats:sub>HI</jats:sub>(<jats:italic>z</jats:italic>) from the end of the reionization epoch to the present.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In recent years, dust masses of a few tenths of a solar mass have been found in the expanding ejecta of a number of core-collapse supernovae. How dust forms in such quantities remains poorly understood; theories of dust formation predict lower total masses and much faster formation rates than observations imply. One suggestion to reconcile observations and theory was made by Dwek et al., who proposed that the dust forms very rapidly, and because of its optical depth, is not initially observationally detectable, only being gradually revealed as the ejecta expand. Observational dust masses at early times would then only be lower limits. Using a large grid of radiative transfer models covering dust masses from 10<jats:sup>−4</jats:sup> to 1 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> to calculate both the spectral energy distribution and the emission line profiles from clumpy dust shells, we show that this cannot be the case. Some clump distributions allow dust masses of ∼0.01 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> to be concealed in clumps and still predict an SED consistent with the observations. However, these geometries predict emission line profiles that are inconsistent with the observations. Similarly, clump geometries that reproduce the observed emission line profiles with dust masses &gt;0.01 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> do not reproduce the SED. However, models with ∼10<jats:sup>−3</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> of amorphous carbon can reproduce both the SED and the emission line profiles. We conclude that no large masses of dust can be hidden from view in the ejecta of SN 1987A at early epochs, and that the majority of dust must thus have formed at epochs &gt;1000 days.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Using hydrodynamic principles we investigate the nature of the disk viscosity following the parameterization by Shakura &amp; Sunyaev adopted for the viscous decretion model in classical Be stars. We consider a radial viscosity distribution including a constant value, a radially variable <jats:italic>α</jats:italic> assuming a power-law density distribution, and isothermal disks, for a late-B central star. We also extend our analysis by determining a self-consistent temperature disk distribution to model the late-type Be star 1 Delphini, which is thought to have a nonvariable, stable disk as evidenced by H<jats:italic>α</jats:italic> emission profiles that have remained relatively unchanged for decades. Using standard angular momentum loss rates given by Granada et al., we find values of <jats:italic>α</jats:italic> of approximately 0.3. Adopting lower values of angular momentum loss rates, i.e., smaller mass loss rates, leads to smaller values of <jats:italic>α</jats:italic>. The values for <jats:italic>α</jats:italic> vary smoothly over the H<jats:italic>α</jats:italic> emitting region and exhibit the biggest variations nearest the central star within about five stellar radii for the late-type, stable Be stars.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Stellar streams are excellent probes of the underlying gravitational potential in which they evolve. In this work, we fit dynamical models to five streams in the Southern Galactic hemisphere, combining observations from the Southern Stellar Stream Spectroscopic Survey (<jats:italic>S</jats:italic> <jats:sup>5</jats:sup>), Gaia EDR3, and the Dark Energy Survey, to measure the mass of the Large Magellanic Cloud (LMC). With an ensemble of streams, we find a mass of the LMC ranging from ∼14–19 × 10<jats:sup>10</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, probed over a range of closest approach times and distances. With the most constraining stream (Orphan–Chenab), we measure an LMC mass of <jats:inline-formula> <jats:tex-math> <?CDATA ${18.8}_{-4.0}^{+3.5}\times {10}^{10}\,{M}_{\odot }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>18.8</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>4.0</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>3.5</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em" /> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac2e93ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, probed at a closest approach time of 310 Myr and a closest approach distance of 25.4 kpc. This mass is compatible with previous measurements, showing that a consistent picture is emerging of the LMC’s influence on structures in the Milky Way. Using this sample of streams, we find that the LMC’s effect depends on the relative orientation of the stream and LMC at their point of closest approach. To better understand this, we present a simple model based on the impulse approximation and we show that the LMC’s effect depends both on the magnitude of the velocity kick imparted to the stream and the direction of this kick.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We investigate the properties of anisotropic, spherically symmetric compact stars, especially neutron stars (NSs) and strange quark stars (SQSs), made of strongly magnetized matter. The NSs are described by the SLy equation of state (EOS) and the SQSs by an EOS based on the MIT Bag model. The stellar models are based on an a priori assumed density dependence of the magnetic field and thus anisotropy. Our study shows that not only the presence of a strong magnetic field and anisotropy, but also the orientation of the magnetic field itself, have an important influence on the physical properties of stars. Two possible magnetic field orientations are considered: a radial orientation where the local magnetic fields point in the radial direction, and a transverse orientation, where the local magnetic fields are perpendicular to the radial direction. Interestingly, we find that for a transverse orientation of the magnetic field, the stars become more massive with increasing anisotropy and magnetic-field strength and increase in size since the repulsive, effective anisotropic force increases in this case. In the case of a radially oriented magnetic field, however, the masses and radii of the stars decrease with increasing magnetic-field strength because of the decreasing effective anisotropic force. Importantly, we also show that in order to achieve hydrostatic equilibrium configurations of magnetized matter, it is essential to account for both the local anisotropy effects as well as the anisotropy effects caused by a strong magnetic field. Otherwise, hydrostatic equilibrium is not achieved for magnetized stellar models.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Galactic bars are frequent in disk galaxies and they may support the transfer of matter toward the central engine of active nuclei. The barred galaxy NGC 1097 has magnetic forces controlling the gas flow at several kpc scales, which suggest that magnetic fields (<jats:italic>B</jats:italic>-fields) are dynamically important along the bar and nuclear ring. However, the effect of the <jats:italic>B</jats:italic>-field on the gas flows in the central kpc scale has not been characterized. Using thermal polarized emission at 89 <jats:italic>μ</jats:italic>m with HAWC+/SOFIA, here, we measure that the polarized flux is spatially located at the contact regions of the outer bar with the starburst ring. The linear polarization decomposition analysis shows that the 89 <jats:italic>μ</jats:italic>m and radio (3.5 and 6.2 cm) polarization traces two different modes, <jats:italic>m</jats:italic>, of the <jats:italic>B</jats:italic>-field: a constant <jats:italic>B</jats:italic>-field orientation and dominated by <jats:italic>m</jats:italic> = 0 at 89 <jats:italic>μ</jats:italic>m, and a spiral <jats:italic>B</jats:italic>-field dominated by <jats:italic>m</jats:italic> = 2 at radio. We show that the <jats:italic>B</jats:italic>-field at 89 <jats:italic>μ</jats:italic>m is concentrated in the warmest region of a shock driven by the galactic-bar dynamics in the contact regions between the outer bar with the starburst ring. Radio polarization traces a superposition of the spiral <jats:italic>B</jats:italic>-field outside and within the starburst ring. According to Faraday rotation measures between 3.5 and 6.2 cm, the radial component of the <jats:italic>B</jats:italic>-field along the contact regions points toward the galaxy's center on both sides. We conclude that gas streams outside and within the starburst ring follow the <jats:italic>B</jats:italic>-field, which feeds the black hole with matter from the host galaxy.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>WL 17 is a young transition disk in the Ophiuchus L1688 molecular cloud complex. Even though WL 17 is among the brightest disks in L1688 and massive enough to expect dust self-scattering, it was undetected in polarization down to Atacama Large Millimeter/submillimeter Array’s (ALMA’s) instrument sensitivity limit. Such low polarization fractions could indicate unresolved polarization within the beam or optically thin dust emission. We test the latter case by combining the high-sensitivity 233 GHz Stokes <jats:italic>I</jats:italic> data from the polarization observations with previous ALMA data at 345 and 100 GHz. We use simple geometric shapes to fit the observed disk visibilities in each band. Using our simple models and assumed dust temperature profiles, we estimate the optical depth in all three bands. The optical depth at 233 GHz peaks at <jats:italic>τ</jats:italic> <jats:sub>233</jats:sub> ∼ 0.3, which suggests the dust emission may not be optically thick enough for dust self-scattering to be efficient. We also find the higher-sensitivity 233 GHz data show substructure in the disk for the first time. The substructure appears as brighter lobes along the major axis, on either side of the star. We attempt to fit the lobes with a simple geometric model, but they are unresolved in the 233 GHz data. We propose that the disk may be flared at 1 mm such that there is a higher column of dust along the major axis than the minor axis when viewed at an inclination. These observations highlight the strength of high-sensitivity continuum data from dust polarization observations to study disk structures.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Magnetic field line reconnection is a universal plasma process responsible for the conversion of magnetic field energy to plasma heating and charged particle acceleration. Solar flares and Earth's magnetospheric substorms are two of the most investigated dynamical systems where global magnetic field reconfiguration is accompanied by energization of plasma populations. Such a reconfiguration includes formation of a long-living current system connecting the primary energy release region and cold dense conductive plasma of the photosphere/ionosphere. In both flares and substorms the evolution of this current system correlates with the formation and dynamics of energetic particle fluxes (although energy ranges can be different for these systems). Our study is focused on the similarity between flares and substorms. Using a wide range of data sets available for flare and substorm investigations, we qualitatively compare the dynamics of currents and energetic particle fluxes for one flare and one substorm. We show that there is a clear correlation between energetic particle precipitations (associated with energy release due to magnetic reconnection seen from riometer and hard X-ray measurements) and magnetic field reconfiguration/formation of the current system, whereas the long-term current system evolution correlates better with hot plasma fluxes (seen from in situ and soft X-ray measurements). We then discuss how data sets of in situ measurements of magnetospheric substorms can help interpret solar flare data.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the first results from the ongoing, intensive, multiwavelength monitoring program of the luminous Seyfert 1 galaxy Mrk 817. While this active galactic nucleus was, in part, selected for its historically unobscured nature, we discovered that the X-ray spectrum is highly absorbed, and there are new blueshifted, broad, and narrow UV absorption lines, which suggest that a dust-free, ionized obscurer located at the inner broad-line region partially covers the central source. Despite the obscuration, we measure UV and optical continuum reverberation lags consistent with a centrally illuminated Shakura–Sunyaev thin accretion disk, and measure reverberation lags associated with the optical broad-line region, as expected. However, in the first 55 days of the campaign, when the obscuration was becoming most extreme, we observe a de-coupling of the UV continuum and the UV broad emission-line variability. The correlation recovered in the next 42 days of the campaign, as Mrk 817 entered a less obscured state. The short C <jats:sc>iv</jats:sc> and Ly<jats:italic>α</jats:italic> lags suggest that the accretion disk extends beyond the UV broad-line region.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Surface brightness fluctuation (SBF) magnitudes are a powerful standard candle to measure distances to semiresolved galaxies in the local universe, a majority of which are dwarf galaxies that often have bluer colors than bright early-type galaxies. We present an empirical <jats:italic>i</jats:italic>-band SBF calibration in a blue regime, 0.2 ≲ (<jats:italic>g</jats:italic> − <jats:italic>i</jats:italic>)<jats:sub>0</jats:sub> ≲ 0.8 in the Hyper Suprime-Cam (HSC) magnitude system. We measure SBF magnitudes for 12 nearby dwarf galaxies of various morphological types with archival HSC imaging data, and use their tip of the red giant branch distances to derive fluctuation–color relations. In order to subtract contributions of fluctuations due to young stellar populations, we use five different <jats:italic>g</jats:italic>-band magnitude masking thresholds, <jats:italic>M</jats:italic> <jats:sub> <jats:italic>g,</jats:italic>thres</jats:sub> = −3.5, −4.0, −4.5, −5.0, and −5.5 mag. We find that the rms scatter of the linear fit to the relation is the smallest (rms = 0.16 mag) in the case of <jats:italic>M</jats:italic> <jats:sub> <jats:italic>g,</jats:italic>thres</jats:sub> = −4.0 mag, <jats:inline-formula> <jats:tex-math> <?CDATA ${\overline{M}}_{i}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mover accent="true"> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo stretchy="true">¯</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mi>i</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac2d94ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> = (−2.65 ± 0.13) + (1.28 ± 0.24) × (<jats:italic>g</jats:italic> − <jats:italic>i</jats:italic>)<jats:sub>0</jats:sub>. This scatter is much smaller than those in the previous studies (rms = 0.26 mag), and is closer to the value for bright red galaxies (rms = 0.12 mag). This calibration is consistent with predictions from metal-poor simple stellar population models.</jats:p>