Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Stellar streams from globular clusters (GCs) offer constraints on the nature of dark matter and have been used to explore the dark matter halo structure and substructure of our Galaxy. Detection of GC streams in other galaxies would broaden this endeavor to a cosmological context, yet no such streams have been detected to date. To enable such exploration, we develop the <jats:monospace>Hough Stream Spotter</jats:monospace> (<jats:monospace>HSS</jats:monospace>), and apply it to the Pan-Andromeda Archaeological Survey (PAndAS) photometric data of resolved stars in M31's stellar halo. We first demonstrate that our code can re-discover known dwarf streams in M31. We then use the <jats:monospace>HSS</jats:monospace> to blindly identify 27 linear GC stream-like structures in the PAndAS data. For each <jats:monospace>HSS</jats:monospace> GC stream candidate, we investigate the morphologies of the streams and the colors and magnitudes of all stars in the candidate streams. We find that the five most significant detections show a stronger signal along the red giant branch in color–magnitude diagrams than spurious non-stream detections. Lastly, we demonstrate that the <jats:monospace>HSS</jats:monospace> will easily detect globular cluster streams in future Nancy Grace Roman Space Telescope data of nearby galaxies. This has the potential to open up a new discovery space for GC stream studies, GC stream gap searches, and for GC stream-based constraints on the nature of dark matter.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>High-energy neutrinos from SN1987A were searched for using upward-going muons recorded by the Kamiokande-II experiment and the IMB experiment. Between 1987 August 11 and October 20, and from an angular window of 10° radius, two upward-going muon events were recorded by Kamiokande-II, and also two events were recorded by IMB. The probability that these upward-going muons were explained by a chance coincidence of atmospheric neutrinos was calculated to be 0.27%. This shows possible evidence of high-energy neutrinos from SN1987A.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report on the detection of a large, extended H <jats:sc>i</jats:sc> cloud complex in the Galaxy and Mass Survey G23 field, located at a redshift of <jats:italic>z</jats:italic> ∼ 0.03, observed as part of the MeerKAT Habitat of Galaxies Survey campaign (a pilot survey to explore the mosaicing capabilities of the MeerKAT telescope). The cloud complex, with a total mass of 10<jats:sup>10.0</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, lies in proximity to a large galaxy group with <jats:italic>M</jats:italic> <jats:sub>dyn</jats:sub> ∼ 10<jats:sup>13.5</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. We identify seven H ɪ peak concentrations, interconnected as a tenuous <jats:italic>chain</jats:italic> structure, extending ∼400 kpc from east to west, with the largest (central) concentration containing 10<jats:sup>9.7</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> in H ɪ gas distributed across 50 kpc. The main source is not detected in ultraviolet, optical, or infrared imaging. The implied gas mass-to-light ratio (<jats:italic>M</jats:italic> <jats:sub>H I</jats:sub>/<jats:italic>L</jats:italic> <jats:sub>r</jats:sub>) is extreme (&gt;1000) even in comparison to other <jats:italic>dark clouds</jats:italic>. The complex has very little kinematic structure (110 km s<jats:sup>−1</jats:sup>), making it difficult to identify cloud rotation. Assuming pressure support, the total mass of the central concentration is &gt; 10<jats:sup>10.2</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, while a lower limit to the dynamical mass in the case of full rotational support is 10<jats:sup>10.4</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. If the central concentration is a stable structure, it has to contain some amount of unseen matter, but potentially less than is observed for a typical galaxy. It is, however, not clear whether the structure has any gravitationally stable concentrations. We report a faint UV-optical-infrared source in proximity to one of the smaller concentrations in the gas complex, leading to a possible stellar association. The system nature and origins is enigmatic, potentially being the result of an interaction with or within the galaxy group it appears to be associated with.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Soft X-ray transients are systems that are detected when they go into an outburst, wherein their X-ray luminosity increases by several orders of magnitude. These outbursts are markers of the poorly understood change in the spectral state of these systems from the low/hard state to the high/soft state. We report the spectral properties of one such soft X-ray transient: MAXI J0637−430, with data from the SXT and LAXPC instruments on board the AstroSat mission. The source was observed for a total of ∼60 ks in two observations on 2019 November 8 and 21 soon after its discovery. Flux-resolved spectral analysis of the source indicates the presence of a multicolor blackbody component arising from the accretion disk and a thermal Comptonization component. The stable low temperature (∼0.55 keV) of the blackbody component points to a cool accretion disk with an inner disk radius of the order of a few hundred kilometers. In addition, we report the presence of a relativistically broadened Gaussian line at 6.4 keV. The disk-dominated flux and photon power-law index of ⪆2 and a constant inner disk radius indicate the source to be in the soft state. From the study we conclude that MAXI J0637−430 is a strong candidate for a black hole X-ray binary.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this work, we present polarization profiles for 23 millisecond pulsars observed at 820 and 1500 MHz with the Green Bank Telescope as part of the NANOGrav pulsar timing array. We calibrate the data using Mueller matrix solutions calculated from observations of PSRs B1929+10 and J1022+1001. We discuss the polarization profiles, which can be used to constrain pulsar emission geometry, and present both the first published radio polarization profiles for nine pulsars and the discovery of very low-intensity average profile components (“microcomponents”) in four pulsars. We obtain the Faraday rotation measures for each pulsar and use them to calculate the Galactic magnetic field parallel to the line of sight for different lines of sight through the interstellar medium. We fit for linear and sinusoidal trends in time in the dispersion measure and Galactic magnetic field and detect magnetic field variations with a period of 1 yr in some pulsars, but overall find that the variations in these parameters are more consistent with a stochastic origin.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We provide observational evidence that galaxy mergers significantly affect stellar kinematics of early-type galaxies (ETGs) such as specific stellar angular momentum within the half-light radius (<jats:inline-formula> <jats:tex-math> <?CDATA ${\lambda }_{{R}_{e}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>λ</mml:mi> </mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>e</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac415dieqn1.gif" xlink:type="simple" /> </jats:inline-formula>) and kinematic misalignment (<jats:italic>ψ</jats:italic> <jats:sub>mis</jats:sub>), using MaNGA integral field unit spectroscopic data that are in the Stripe 82 region of the Sloan Digital Sky Survey. In this study, tidal features around ETGs, which are detected in deep coadded images, are used as direct evidence for mergers that occurred recently. In the case of ETGs that do not have dust lanes, <jats:inline-formula> <jats:tex-math> <?CDATA ${\lambda }_{{R}_{e}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>λ</mml:mi> </mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>e</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac415dieqn2.gif" xlink:type="simple" /> </jats:inline-formula> is lower in ETGs with tidal features than in those without tidal features (median <jats:inline-formula> <jats:tex-math> <?CDATA ${\lambda }_{{R}_{e}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>λ</mml:mi> </mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>e</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac415dieqn3.gif" xlink:type="simple" /> </jats:inline-formula>: 0.21 versus 0.39) in all stellar mass and Sérsic index ranges except the most massive bin, so that the fraction of ETGs with tidal features in slow rotators is more than twice as large as that in fast rotators (42% versus 18%). Moreover, ETGs with tidal features have larger <jats:italic>ψ</jats:italic> <jats:sub>mis</jats:sub> than those without tidal features (mean <jats:italic>ψ</jats:italic> <jats:sub>mis</jats:sub>: 28° versus 15°). By contrast, ETGs with dust lanes are fast rotators, and ETGs with both dust lanes and tidal features have the highest <jats:inline-formula> <jats:tex-math> <?CDATA ${\lambda }_{{R}_{e}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>λ</mml:mi> </mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>e</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac415dieqn4.gif" xlink:type="simple" /> </jats:inline-formula> (median <jats:inline-formula> <jats:tex-math> <?CDATA ${\lambda }_{{R}_{e}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>λ</mml:mi> </mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>e</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac415dieqn5.gif" xlink:type="simple" /> </jats:inline-formula>: 0.59) among all ETG categories. In addition, ETGs with dust lanes have small <jats:italic>ψ</jats:italic> <jats:sub>mis</jats:sub> regardless of the existence of tidal features (<jats:italic>ψ</jats:italic> <jats:sub>mis</jats:sub> &lt; 7.°5). Our results can be explained if mergers with different gas fractions generate merger remnants that have different kinematic properties.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Most stars host convection zones in which heat is transported directly by fluid motion, but the behavior of convective boundaries is not well-understood. Here, we present 3D numerical simulations that exhibit penetration zones: regions where the entire luminosity <jats:italic>could</jats:italic> be carried by radiation, but where the temperature gradient is approximately adiabatic and convection is present. To parameterize this effect, we define the “penetration parameter” <jats:inline-formula> <jats:tex-math> <?CDATA ${ \mathcal P }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="italic"></mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac408dieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, which compares how far the radiative gradient deviates from the adiabatic gradient on either side of the Schwarzschild convective boundary. Following Roxburgh and Zahn, we construct an energy-based theoretical model in which <jats:inline-formula> <jats:tex-math> <?CDATA ${ \mathcal P }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="italic"></mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac408dieqn2.gif" xlink:type="simple" /> </jats:inline-formula> controls the extent of penetration. We test this theory using 3D numerical simulations that employ a simplified Boussinesq model of stellar convection. The convection is driven by internal heating, and we use a height-dependent radiative conductivity. This allows us to separately specify <jats:inline-formula> <jats:tex-math> <?CDATA ${ \mathcal P }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="italic"></mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac408dieqn3.gif" xlink:type="simple" /> </jats:inline-formula> and the stiffness <jats:inline-formula> <jats:tex-math> <?CDATA ${ \mathcal S }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="italic"></mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac408dieqn4.gif" xlink:type="simple" /> </jats:inline-formula> of the radiative–convective boundary. We find significant convective penetration in all simulations. Our simple theory describes the simulations well. Penetration zones can take thousands of overturn times to develop, so long simulations or accelerated evolutionary techniques are required. In stars, we expect <jats:inline-formula> <jats:tex-math> <?CDATA ${ \mathcal P }\approx 1$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="italic"></mml:mi> <mml:mo>≈</mml:mo> <mml:mn>1</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac408dieqn5.gif" xlink:type="simple" /> </jats:inline-formula>, and in this regime, our results suggest that convection zones may extend beyond the Schwarzschild boundary by up to ∼20%–30% of a mixing length. We present a MESA stellar model of the Sun that employs our parameterization of convective penetration as a proof of concept. Finally, we discuss prospects for extending these results to more realistic stellar contexts.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The observed lensed fraction of high-redshift quasars (∼0.2%) is significantly lower than previous theoretical predictions (≳4%). We revisit the lensed fraction of high-redshift quasars predicted by theoretical models, where we adopt recent measurements of galaxy velocity dispersion functions (VDFs) and explore a wide range of quasar luminosity function (QLF) parameters. We use both analytical methods and mock catalogs, which give consistent results. For ordinary QLF parameters and the depth of current high-redshift quasar surveys (<jats:italic>m</jats:italic> <jats:sub> <jats:italic>z</jats:italic> </jats:sub> ≲ 22), our model suggests a multiply imaged fraction of <jats:italic>F</jats:italic> <jats:sub>multi</jats:sub> ∼ 0.4%–0.8%. The predicted lensed fraction is ∼1%–6% for the brightest <jats:italic>z</jats:italic> <jats:sub> <jats:italic>s</jats:italic> </jats:sub> ∼ 6 quasars (<jats:italic>m</jats:italic> <jats:sub> <jats:italic>z</jats:italic> </jats:sub> ≲ 19), depending on the QLF. The systematic uncertainties of the predicted lensed fraction in previous models can be as large as 2–4 times and are dominated by the VDF. Applying VDFs from recent measurements decreases the predicted lensed fraction and relieves the tension between observations and theoretical models. Given the depth of current imaging surveys, there are ∼15 lensed quasars at <jats:italic>z</jats:italic> <jats:sub> <jats:italic>s</jats:italic> </jats:sub> &gt; 5.5 detectable over the sky. Upcoming sky surveys like the Legacy Survey of Space and Time survey and the Euclid survey will find several tens of lensed quasars at this redshift range.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Gamma-ray bursts (GRBs) are widely believed to be from massive collapsars and/or compact binary mergers,which, accordingly, would generate long and short GRBs, respectively. The details on this classification scheme have been in constant debate given more and more observational data available to us. In this work, we apply a series of data mining methods to studying the potential classification information contained in the prompt emission of GRBs detected by the Fermi Gamma-ray Burst Monitor. A tight global correlation is found between fluence (<jats:italic>f</jats:italic>), peak flux (<jats:italic>F</jats:italic>), and prompt duration (<jats:italic>T</jats:italic> <jats:sub>90</jats:sub>) which takes the form of <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}\,f=0.75\,\mathrm{log}\,{T}_{90}+0.92\mathrm{log}F-7.14$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mspace width="0.25em" /> <mml:mi>f</mml:mi> <mml:mo>=</mml:mo> <mml:mn>0.75</mml:mn> <mml:mspace width="0.25em" /> <mml:mi>log</mml:mi> <mml:mspace width="0.25em" /> <mml:msub> <mml:mrow> <mml:mi>T</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>90</mml:mn> </mml:mrow> </mml:msub> <mml:mo>+</mml:mo> <mml:mn>0.92</mml:mn> <mml:mi>log</mml:mi> <mml:mi>F</mml:mi> <mml:mo>−</mml:mo> <mml:mn>7.14</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac4753ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>. Based on this correlation, we can define a new parameter <jats:inline-formula> <jats:tex-math> <?CDATA $L=1.66\,\mathrm{log}\,{T}_{90}+0.84\mathrm{log}\,f-0.46\mathrm{log}F+3.24$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>L</mml:mi> <mml:mo>=</mml:mo> <mml:mn>1.66</mml:mn> <mml:mspace width="0.25em" /> <mml:mi>log</mml:mi> <mml:mspace width="0.25em" /> <mml:msub> <mml:mrow> <mml:mi>T</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>90</mml:mn> </mml:mrow> </mml:msub> <mml:mo>+</mml:mo> <mml:mn>0.84</mml:mn> <mml:mi>log</mml:mi> <mml:mspace width="0.25em" /> <mml:mi>f</mml:mi> <mml:mo>−</mml:mo> <mml:mn>0.46</mml:mn> <mml:mi>log</mml:mi> <mml:mi>F</mml:mi> <mml:mo>+</mml:mo> <mml:mn>3.24</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac4753ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> by linear discriminant analysis that would distinguish between long and short GRBs with much less ambiguity than <jats:italic>T</jats:italic> <jats:sub>90</jats:sub>. We also discussed the three subclasses scheme of GRB classification derived from clusters analysis based on a Gaussian mixture model, and suggest that, besides SGRBs, LGRBs may be divided into long-bright gamma-ray bursts (LBGRBs) and long-faint gamma-ray bursts (LFGRBs), LBGRBs have statistical higher <jats:italic>f</jats:italic> and <jats:italic>F</jats:italic> than LFGRBs; further statistical analysis found that LBGRBs also have higher number of GRB pulses than LFGRBs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We studied the presence and spatiotemporal characteristics and evolution of the variations in the differential rotation rates and radial magnetic fields in the Schwabe and quasi-biennial-oscillation (QBO) timescales. To achieve these objectives, we used rotation rate residuals and radial magnetic field data from the Michelson Doppler Imager on the Solar and Heliospheric Observatory and the Helioseismic and Magnetic Imager on the Solar Dynamics Observatory, extending from 1996 May to 2020 August, covering solar cycles 23 and 24, respectively. Under the assumption that the radial surface magnetic field is nonlocal and the differential rotation is symmetric around the equator, our results suggest that the source region of the Schwabe cycle is confined between ∼30° N and S throughout the convection zone. As for the source region of the QBO, our results suggest that it is below 0.78 <jats:italic>R</jats:italic> <jats:sub>⊙</jats:sub>.</jats:p>