Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>The fuzzy dark matter model (FDM; also known as quantum wave dark matter model) argues that light bosons with a mass of <jats:inline-formula> <jats:tex-math> <?CDATA $\sim {10}^{-22}\,\mathrm{eV}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjab6598ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> are a possible candidate for dark matter in the universe. One of the most important predictions of FDM is the formation of a soliton core instead of a density cusp at the center of galaxies. If FDM is the correct theory of dark matter, then the predicted soliton core can help form the Central Molecular Zone (CMZ) in the Milky Way. We present high-resolution hydrodynamical simulations of gas flow patterns to constrain the properties of the soliton core based on a realistic Milky Way potential. We find that a dense center is required to form a reasonable CMZ. The size and kinematics of the CMZ offer a relatively strong constraint on the inner enclosed mass profile of the Galaxy. If a soliton core is not considered, a compact nuclear bulge alone with a radially varying mass-to-light ratio can match the observed size and kinematics of the CMZ. A soliton core model with a mass of <jats:inline-formula> <jats:tex-math> <?CDATA $\approx 4.0\times {10}^{8}\,{M}_{\odot }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjab6598ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> and a core radius of <jats:inline-formula> <jats:tex-math> <?CDATA $\approx 0.05\,\mathrm{kpc}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjab6598ieqn3.gif" xlink:type="simple" /> </jats:inline-formula>, together with a less massive nuclear bulge with a constant mass-to-light ratio, also agrees nicely with the current data. Such an FDM soliton core corresponds to a boson mass of <jats:inline-formula> <jats:tex-math> <?CDATA $(\sim 2\mbox{--}7)\times {10}^{-22}\,\mathrm{eV}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjab6598ieqn4.gif" xlink:type="simple" /> </jats:inline-formula>, which could be further constrained by the improved determination of the mass-to-light ratio in the Galactic center.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We study six luminous Ly<jats:italic>α</jats:italic> emitters (LAEs) with very blue rest-frame UV continua at 5.7 ≤ <jats:italic>z</jats:italic> ≤ 6.6. These LAEs have previous <jats:italic>Hubble Space Telescope</jats:italic> (<jats:italic>HST</jats:italic>) and <jats:italic>Spitzer</jats:italic> IRAC observations. Combining our newly acquired <jats:italic>HST</jats:italic> images, we find that their UV-continuum slopes <jats:italic>β</jats:italic> are in a range of −3.4 ≤ <jats:italic>β</jats:italic> ≤ −2.6. Unlike previous, tentative detections of <jats:italic>β</jats:italic> ≃ −3 in photometrically selected, low-luminosity galaxies, our LAEs are spectroscopically confirmed and luminous (<jats:italic>M</jats:italic> <jats:sub>UV</jats:sub> &lt; −20 mag). We model their broadband spectral energy distributions (SEDs), and find that two <jats:italic>β</jats:italic> ≃ −2.6 ± 0.2 galaxies can be well fitted with young and dust-free stellar populations. However, it becomes increasingly difficult to fit bluer galaxies. We explore further interpretations by including the non-zero LyC escape fraction <jats:italic>f</jats:italic> <jats:sub>esc</jats:sub>, very low metallicities, and/or active galactic nucleus contributions. Assuming <jats:italic>f</jats:italic> <jats:sub>esc</jats:sub> ≃ 0.2, we achieve the bluest slopes <jats:italic>β</jats:italic> ≃ −2.7 when nebular emission is considered. This can nearly explain the SEDs of two galaxies with <jats:italic>β</jats:italic> ≃ −2.8 and −2.9 (<jats:italic>σ</jats:italic> <jats:sub> <jats:italic>β</jats:italic> </jats:sub> = 0.15). Larger <jats:italic>f</jats:italic> <jats:sub>esc</jats:sub> values and very low metallicities are not favored by the strong nebular line emission (evidenced by the IRAC flux) or the observed (IRAC 1 − IRAC 2) color. Finally, we find that the <jats:italic>β</jats:italic> ≃ −2.9 galaxy can potentially be well explained by the combination of a very young population with a high <jats:italic>f</jats:italic> <jats:sub>esc</jats:sub> (≥0.5) and an old, dusty population. We are not able to produce two <jats:italic>β</jats:italic> ≃ −3.4 ± 0.4 galaxies. Future deep spectroscopic observations are needed to fully understand these galaxies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We propose a radically different picture for X-shaped radio galaxies compared with existing models as transition objects between cold-mode accreting, low-spinning retrograde black holes and low-spinning prograde black holes. This model explains their smaller average black hole masses; their general aversion for cluster compared with isolated environments; the negligible difference in spectral index between primary and secondary jets, despite a time difference in their formation; their absence among the most powerful radio quasars and radio galaxies; and their connection to the elusive Fanaroff–Riley I quasar class, among others. The key to their formation is cold gas accretion onto Schwarzschild black holes.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present optical photometry and spectroscopy of the Type Ia supernova SN2018cqj/ATLAS18qtd. The supernova exploded in an isolated region at ∼65 kpc from the S0 galaxy IC 550 at <jats:italic>z</jats:italic> = 0.0165 (<jats:italic>D</jats:italic> ≈ 74 Mpc) and has a redshift consistent with a physical association to this galaxy. Multicolor photometry show that SN2018cqj/ATLAS18qtd is a low-luminosity (<jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{{B}_{\max }}\approx -17.9$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjab6323ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> mag), fast-declining Type Ia, with color stretch <jats:italic>s</jats:italic> <jats:sub> <jats:italic>BV</jats:italic> </jats:sub> ≈ 0.6 and <jats:italic>B</jats:italic>-band decline rate Δ<jats:italic>m</jats:italic> <jats:sub>15</jats:sub>(<jats:italic>B</jats:italic>) ≈ 1.77 mag. Two nebular-phase spectra obtained as part of the 100IAS survey at +193 and +307 days after peak show the clear detection of a narrow H<jats:italic>α</jats:italic> line in emission that is resolved in the first spectrum with FWHM ≈ 1200 km s<jats:sup>−1</jats:sup> and <jats:italic>L</jats:italic> <jats:sub>H<jats:italic>α</jats:italic> </jats:sub> ≈ 3.8 × 10<jats:sup>37</jats:sup> erg s<jats:sup>−1</jats:sup>. The detection of a resolved H<jats:italic>α</jats:italic> line with a declining luminosity is broadly consistent with recent models where hydrogen is stripped from the nondegenerate companion in a single-degenerate progenitor system. However, the amount of hydrogen consistent with the luminosities of the H<jats:italic>α</jats:italic> line would be ∼10<jats:sup>−3</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, which is significantly less than theoretical model predictions in the classical single-degenerate progenitor systems. SN2018cqj/ATLAS18qtd is the second low-luminosity, fast-declining SN Ia after SN2018fhw/ASASSN-18tb that shows narrow H<jats:italic>α</jats:italic> in emission in its nebular-phase spectra.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We consider some observational consequences of replacing all black holes (BHs) with a class of non-singular solutions that mimic BHs but with dark energy (DE) interiors; GEneric Objects of DE (GEODEs). We focus on the BH mass function and chirp-mass redshift distribution of mergers visible to gravitational-wave observatories. We incorporate the GEODE blueshift into an initially Salpeter stellar remnant distribution, and model the binary population by evolving synthesized binary remnant distributions, published before LIGO’s first measurements. We find that a GEODE produced between 20 ≲ <jats:italic>z</jats:italic> ≲ 40, and observed at <jats:italic>z</jats:italic> ∼ 7, will have its initial mass amplified by ∼20–140×. This can relieve tension between accretion-only growth models and the inferred masses of BHs in quasars at <jats:italic>z</jats:italic> ≳ 6. Moreover, we find that merger rates of GEODE binaries increase by a factor of ∼2× relative to classical BHs. The resulting GEODE mass function is consistent with the most recent LIGO constraints at &lt;0.5<jats:italic>σ</jats:italic>. In contrast, a Salpeter stellar distribution that evolves into classical remnants is in tension at ≳2<jats:italic>σ</jats:italic>. This agreement occurs without low-metallicity regions, abnormally massive progenitor stars, novel formation channels, or primordial object formation at extreme rates. In particular, we find that solar metallicity progenitors, which produce 1.1–1.8<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> remnants, overlap with many LIGO observations when evolved as GEODEs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We observed rapid variability (≲60 s) at the footpoints of transient, hot (∼8–10 MK) coronal loops in active region cores, with the <jats:italic>Interface Region Imaging Spectrograph</jats:italic> (<jats:italic>IRIS</jats:italic>). The high spatial (∼0.″33) and temporal (≲5–10 s) resolution of <jats:italic>IRIS</jats:italic> is often crucial for the detection of this variability. We show how, in combination with 1D RADYN loop modeling, these <jats:italic>IRIS</jats:italic> spectral observations of the transition region (TR) and chromosphere provide powerful diagnostics of the properties of coronal heating and energy transport (thermal conduction or nonthermal electrons, NTEs). Our simulations of nanoflare-heated loops indicate that emission in the Mg <jats:sc>ii</jats:sc> triplet can be used as a sensitive diagnostic for nonthermal particles. In our events, we observe a large variety of <jats:italic>IRIS</jats:italic> spectral properties (intensity, Doppler shifts, broadening, chromospheric/TR line ratios, Mg <jats:sc>ii</jats:sc> triplet emission) even for different footpoints of the same coronal events. In several events, we find spectroscopic evidence for NTEs (e.g., TR blueshifts and Mg <jats:sc>ii</jats:sc> triplet emission), suggesting that particle acceleration can occur even for very small magnetic reconnection events, which are generally below the detection threshold of hard X-ray instruments that provide direct detection of emission of nonthermal particles.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In past decades, much progress has been achieved in understanding the origin and evolution of coronal mass ejections (CMEs). In situ observations of the counterparts of CMEs, especially magnetic clouds (MCs) near the Earth, have provided measurements of the structure and total flux of CME flux ropes. However, it has been difficult to measure these properties in an erupting CME flux rope, in particular in a preexisting flux rope. In this work, we propose a model to estimate the toroidal flux of a preexisting flux rope by subtracting the flux contributed by magnetic reconnection during the eruption from the flux measured in the MC. The flux contributed by the reconnection is derived from geometric properties of two-ribbon flares based on a quasi-2D reconnection model. We then apply the model to four CME/flare events and find that the ratio of toroidal flux in the preexisting flux rope to that in the associated MC lies in the range 0.40–0.88. This indicates that the toroidal flux of the preexisting flux rope makes an important contribution to that of the CME flux rope and is usually at least as large as the flux arising from the eruption process for the selected events.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We analyzed the young (2.8 Myr-old) binary system FS Tau A using near-infrared (<jats:italic>H</jats:italic>-band) high-contrast polarimetry data from Subaru/HiCIAO and submillimeter CO (J = 2–1) line emission data from Atacama Large Millimeter/submillimeter Array (ALMA). Both the near-infrared and submillimeter observations reveal several clear structures extending to ∼240 au from the stars. Based on these observations at different wavelengths, we report the following discoveries. One arm-like structure detected in the near-infrared band initially extends from the south of the binary with a subsequent turn to the northeast, corresponding to two bar-like structures detected in ALMA observations with an local standard of rest kinematic (LSRK) velocity of 1.19–5.64 km s<jats:sup>−1</jats:sup>. Another feature detected in the near-infrared band extends initially from the north of the binary, relating to an arm-like structure detected in ALMA observations with an LSRK velocity of 8.17–16.43 km s<jats:sup>−1</jats:sup>. From their shapes and velocities, we suggest that these structures can mostly be explained by two streamers that connect the outer circumbinary disk and the central binary components. These discoveries will be helpful for understanding the evolution of streamers and circumstellar disks in young binary systems.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Conclusively determining the states of the solar wind will aid in tracing the origins of those states to the Sun, and in the process help to find the wind’s origin and acceleration mechanism(s). Prior studies have characterized the various states of the wind, making lists that are only partially based on objective criteria; different approaches obtain substantially different results. To uncover the unbiased states of the solar wind, we use “<jats:italic>k</jats:italic>-means clustering”—an unsupervised machine learning method—including constructed multipoint variables. The method allows exploration of different descriptive state variables and numbers of fundamental states (clusters). We show that the clusters reveal structures similar to those found by more ad hoc means, including coronal hole wind, interplanetary coronal mass ejections, “slow wind” (better: noncoronal hole flow), “pseudostreamers,” and stream interaction regions, but with differences that should be useful in refining our previous ideas. These results demonstrate the viability of the approach and warrant further study to understand the origin of remaining discrepancies. Complexity in <jats:italic>k</jats:italic>-means characterization of the wind may ultimately point to complexity at the source; studies closer to the Sun with <jats:italic>Parker Solar Probe</jats:italic> will help. We confirm the utility of a set of variables that can serve as a proxy for composition measurements. This proxy permits studies at high time resolution and where composition is not available. This and our recently developed unsupervised multivariate clustering technique are expected to be beneficial in the automated identification of structures and events in a variety of studies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We measured [Fe/H] and [<jats:italic>α</jats:italic>/Fe] using spectral synthesis of low-resolution stellar spectroscopy for 70 individual red-giant-branch stars across four fields spanning the outer disk, Giant Stellar Stream (GSS), and inner halo of M31. Fields at M31-centric projected distances of 23 kpc in the halo, 12 kpc in the halo, 22 kpc in the GSS, and 26 kpc in the outer disk are <jats:italic>α</jats:italic>-enhanced, with <jats:inline-formula> <jats:tex-math> <?CDATA $\langle $?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjab6659ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>[<jats:italic>α</jats:italic>/Fe]<jats:inline-formula> <jats:tex-math> <?CDATA $\rangle $?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjab6659ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> = 0.43, 0.50, 0.41, and 0.58, respectively. The 23 and 12 kpc halo fields are relatively metal-poor, with <jats:inline-formula> <jats:tex-math> <?CDATA $\langle $?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjab6659ieqn3.gif" xlink:type="simple" /> </jats:inline-formula>[Fe/H]<jats:inline-formula> <jats:tex-math> <?CDATA $\rangle $?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjab6659ieqn4.gif" xlink:type="simple" /> </jats:inline-formula> = −1.54 and −1.30, whereas the 22 kpc GSS and 26 kpc outer disk fields are relatively metal-rich with <jats:inline-formula> <jats:tex-math> <?CDATA $\langle $?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjab6659ieqn5.gif" xlink:type="simple" /> </jats:inline-formula>[Fe/H]<jats:inline-formula> <jats:tex-math> <?CDATA $\rangle $?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjab6659ieqn6.gif" xlink:type="simple" /> </jats:inline-formula> = −0.84 and −0.92, respectively. For fields with substructure, we separated the stellar populations into kinematically hot stellar halo components and kinematically cold components. We did not find any evidence of a radial [<jats:italic>α</jats:italic>/Fe] gradient along the high surface brightness core of the GSS between ∼17 and 22 kpc. However, we found tentative suggestions of a negative radial [<jats:italic>α</jats:italic>/Fe] gradient in the stellar halo, which may indicate that different progenitor(s) or formation mechanisms contributed to the build up of the inner versus outer halo. Additionally, the [<jats:italic>α</jats:italic>/Fe] distribution of the metal-rich ([Fe/H] &gt; −1.5), smooth inner stellar halo (r<jats:sub>proj</jats:sub> ≲ 26 kpc) is inconsistent with having formed from the disruption of a progenitor(s) similar to present-day M31 satellite galaxies. The 26 kpc outer disk is most likely associated with the extended disk of M31, where its high <jats:italic>α</jats:italic>-enhancement provides support for an episode of rapid star formation in M31's disk possibly induced by a major merger.</jats:p>