Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We present high-cadence, comprehensive data on the nearby (<jats:italic>D</jats:italic> ≃ 33 Mpc) Type II supernova (SN II) 2017ahn, discovered within about one day of the explosion, from the very early phases after explosion to the nebular phase. The observables of SN 2017ahn show a significant evolution over the ≃470 days of our follow-up campaign, first showing prominent, narrow Balmer lines and other high-ionization features purely in emission (i.e., flash spectroscopy features), which progressively fade and lead to a spectroscopic evolution similar to that of more canonical SNe II. Over the same period, the decline of the light curves in all bands is fast, resembling the photometric evolution of linearly declining H-rich core-collapse SNe. The modeling of the light curves and early flash spectra suggests that a complex circumstellar medium surrounds the progenitor star at the time of explosion, with a first dense shell produced during the very late stages of its evolution that is swept up by the rapidly expanding ejecta within the first ∼6 days of the SN evolution, while signatures of interaction are observed also at later phases. Hydrodynamical models support the scenario in which linearly declining SNe II are predicted to arise from massive yellow super- or hypergiants depleted of most of their hydrogen layers.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The PO molecule (<jats:italic>X</jats:italic> <jats:sup>2</jats:sup>Π<jats:sub>r</jats:sub>) has been detected toward Orion-KL via its <jats:italic>J</jats:italic> = 2.5 → 1.5 transition near 109 GHz using the 12 m telescope of the Arizona Radio Observatory. This transition consists of a quartet of lines, generated by lambda-doubling and phosphorus hyperfine interactions, creating a distinct pattern of doublets of doublets. All four features (<jats:italic>F</jats:italic> = 3 → 2, <jats:italic>e, f</jats:italic> and 2 → 1, <jats:italic>e, f</jats:italic> ) were detected. The line profiles measured were relatively broad, with Δ<jats:italic>V</jats:italic> <jats:sub>1/2</jats:sub> ∼ 21–25 km s<jats:sup>−1</jats:sup>, and <jats:italic>V</jats:italic> <jats:sub>LSR</jats:sub> ∼ 10 km s<jats:sup>−1</jats:sup>, clearly identifying the molecule as arising from the Orion “plateau” region. The <jats:italic>J</jats:italic> = 2  → 1 transition of PN (<jats:italic>X</jats:italic> <jats:sup>1</jats:sup>Σ) at 94 GHz was also measured, and its line profile indicates a plateau origin in Orion, as found previously by Ziurys. Therefore, PO and PN arise from the same gas. There was no evidence of a “hot core” or “ridge” component in either molecule. The column densities determined for PO and PN in the Orion plateau are <jats:italic>N</jats:italic> <jats:sub>tot</jats:sub> ≈ 5.4(0.2) × 10<jats:sup>13</jats:sup> and 2.0(0.4) × 10<jats:sup>13</jats:sup> cm<jats:sup>−2</jats:sup>, respectively, with corresponding abundances, relative to H<jats:sub>2</jats:sub>, of <jats:italic>f</jats:italic> ∼ 1.6(0.1) × 10<jats:sup>−10</jats:sup> and 6.1(0.6) × 10<jats:sup>−11</jats:sup>, resulting in PO/PN ∼ 3. The PO and PN line profiles also resemble those of SiO and SiS, suggesting that the phosphorus molecules are produced by shocks in the plateau outflow. The observed PO/PN ratio in Orion-KL is very close in value to that measured in other warm molecular clouds, indicating a common synthesis pathway for these two molecules in outflows caused by star formation.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Milky Way’s dark matter halo is expected to host numerous low-mass subhalos with no detectable associated stellar component. Such subhalos are invisible unless their dark matter annihilates to visible states such as photons. One of the established methods for identifying candidate subhalos is to search for individual unassociated gamma-ray sources with properties consistent with the dark matter expectation. However, robustly ruling out an astrophysical origin for any such candidate is challenging. In this work, we present a complementary approach that harnesses information about the entire population of subhalos—such as their spatial and mass distribution in the Galaxy—to search for a signal of annihilating dark matter. Using simulated data, we show that the collective emission from subhalos can imprint itself in a unique way on the statistics of observed photons, even when individual subhalos may be too dim to be resolved on their own. Additionally, we demonstrate that, for the models we consider, the signal can be identified even in the face of unresolved astrophysical point-source emission of extragalactic and Galactic origin. This establishes a new search technique for subhalos that is complementary to established methods, and that could have important ramifications for gamma-ray dark matter searches using observatories such as the Fermi Large Area Telescope and the Cerenkov Telescope Array.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the formation and eruption of a sigmoidal filament driven by rotating network magnetic fields (RNFs) near the center of the solar disk, which was observed by the 1 m aperture New Vacuum Solar Telescope at the Fuxian Solar Observatory on 2018 July 12. Counterclockwise RNFs twist two small-scale filaments at their northeastern foot-point region, giving a rotation of nearly 200° within about 140 minutes. The motion of the RNF has a tendency to accelerate at first and then decelerate obviously, as the average rotation speed increased from 10 to 150° hr<jats:sup>−1</jats:sup>, and then slowed down to 50° hr<jats:sup>−1</jats:sup>. Coalescence then occurs between filaments F1 and F2. Meanwhile the fine structures in the southwestern region of the filament was involved in another interaction of coalescence. The subsequent EUV brightening due to plasma heating is observed in the two interaction regions. These interacting structures, including F1, F2 and the fine structures in the southwestern region, eventually evolve into a larger-scale sigmoidal filament twisted in the same direction as the RNFs gave. The twist of the sigmoidal filament has exceeded 4<jats:italic>π</jats:italic> and the filament finally erupted. The motion of the sigmoidal filament remains uniform until a nearby jet collides, causing the filament to erupt faster. These results provide evidence that RNF plays an important role in the formation and eruption of the sigmoidal filament. The phenomena also suggests that the kink instability is the trigger mechanism for the filament eruption.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The aim of this study is to model the nature of nonlinear torsional magnetohydrodynamic waves propagating in solar jets as they are elevated to the outer solar atmosphere. The contribution of sequential processes to the transfer of energy is taken under consideration: the nonlinear cascade and shock formation. Thus a straight magnetic cylinder embedded in a plasma with an initial magnetic field and parallel flow to the cylinder axis is implemented. To resemble a jet where the oscillation wavelength highly exceeds the radius, the second-order thin flux tube approximation proves adequate. A Cohen–Kulsrud type equation is presented, and its solution highly depends on the parameter presented in this study, which itself is constituted of various environmental and equilibrium conditions that affect the perturbations of the variables as well as the nonlinear forces connected to Alfvén wave propagation. The shock formation time of torsional waves is inversely proportional to the density contrast of the jet, while the efficiency of energy transfer to shorter scales is directly proportional to the density contrast. While the parallel flow with a shear at the boundary expedites shock formation, its efficiency regarding energy transfer is dramatically enhanced by the plasma-<jats:italic>β</jats:italic>, significantly contributing to coronal heating. The observational and seismological aspect of the present study is that faster jets are less probable for observations at higher altitudes, as they experience energy transfer mostly at the base of the corona, while slow speed jets may be observed at higher altitudes contributing to solar wind acceleration.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Recent simulation studies suggest that the compaction of star-forming galaxies (SFGs) at high redshift might be a critical process, during which the central bulge is being rapidly built, followed by quenching of the star formation. To explore dust properties of SFGs with compact morphology, we investigate the dependence of dust temperature, <jats:italic>T</jats:italic> <jats:sub>dust</jats:sub>, on their size and star formation activity, using a sample of massive SFGs with <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}({M}_{* }/{M}_{\odot })\gt 10$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabc9bbieqn1.gif" xlink:type="simple" /> </jats:inline-formula> at 1 &lt; <jats:italic>z</jats:italic> &lt; 3, drawn from the 3D-HST/CANDELS database in combination with deep Herschel observations. <jats:italic>T</jats:italic> <jats:sub>dust</jats:sub> is derived via fitting the mid-to-far-infrared photometry with a mid-infrared power law and a far-infrared modified blackbody. We find that both extended and compact SFGs generally follow a similar <jats:italic>T</jats:italic> <jats:sub>dust</jats:sub> − <jats:italic>z</jats:italic> evolutionary track as that of the main-sequence galaxies. The compact SFGs seem to share similar dust temperature with extended SFGs. Despite the frequent occurrence of active galactic nuclei (AGNs) in compact SFGs, we do not observe any effect on dust caused by the presence of AGNs in these galaxies during the compaction. Our results disfavor different ISM properties between compact and extended SFGs, suggesting that a rapid and violent compaction process might be not necessary for the formation of compact SFGs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We used existing data from the New Horizons Long-range Reconnaissance Imager (LORRI) to measure the optical-band (0.4 ≲ <jats:italic>λ</jats:italic> ≲ 0.9 <jats:italic>μ</jats:italic>m) sky brightness within seven high–Galactic latitude fields. The average raw level measured while New Horizons was 42–45 au from the Sun is 33.2 ± 0.5 nW m<jats:sup>−2</jats:sup> sr<jats:sup>−1</jats:sup>.  This is ∼10× as dark as the darkest sky accessible to the Hubble Space Telescope, highlighting the utility of New Horizons for detecting the cosmic optical background (COB). Isolating the COB contribution to the raw total required subtracting scattered light from bright stars and galaxies, faint stars below the photometric detection limit within the fields, and diffuse Milky Way light scattered by infrared cirrus. We removed newly identified residual zodiacal light from the IRIS 100 <jats:italic>μ</jats:italic>m all-sky maps to generate two different estimates for the diffuse Galactic light. Using these yielded a highly significant detection of the COB in the range 15.9 ± 4.2 (1.8 stat., 3.7 sys.) nW m<jats:sup>−2</jats:sup> sr<jats:sup>−1</jats:sup> to 18.7 ± 3.8 (1.8 stat., 3.3 sys.) nW m<jats:sup>−2</jats:sup> sr<jats:sup>−1</jats:sup> at the LORRI pivot wavelength of 0.608 <jats:italic>μ</jats:italic>m. Subtraction of the integrated light of galaxies fainter than the photometric detection limit from the total COB level left a diffuse flux component of unknown origin in the range 8.8 ± 4.9 (1.8 stat., 4.5 sys.) nW m<jats:sup>−2</jats:sup> sr<jats:sup>−1</jats:sup> to 11.9 ± 4.6 (1.8 stat., 4.2 sys.) nW m<jats:sup>−2</jats:sup> sr<jats:sup>−1</jats:sup>. Explaining it with undetected galaxies requires the assumption that the galaxy count faint-end slope steepens markedly at <jats:italic>V</jats:italic> &gt; 24 or that existing surveys are missing half the galaxies with <jats:italic>V</jats:italic> &lt; 30.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Solar activities, in particular coronal mass ejections (CMEs), are often accompanied by bursts of radiation at meter wavelengths. Some of these bursts have a long duration and extend over a wide frequency band, namely, type IV radio bursts. However, the association of type IV bursts with CMEs is still not well understood. In this article, we perform the first statistical study of type IV solar radio bursts in solar cycle 24. Our study includes a total of 446 type IV radio bursts that occurred during this cycle. Our results show that a clear majority, ∼81% of type IV bursts, were accompanied by CMEs, based on a temporal association with white-light CME observations. However, we found that only ∼2.2% of the CMEs are accompanied by type IV radio bursts. We categorized the type IV bursts as moving or stationary based on their spectral characteristics and found that only ∼18% of the total type IV bursts in this study were moving type IV bursts. Our study suggests that type IV bursts can occur with both “Fast” (≥500 km s<jats:sup>−1</jats:sup>) and “Slow” (&lt;500 km s<jats:sup>−1</jats:sup>), and also both “Wide” (≥60°) and “Narrow” (&lt;60°), CMEs. However, the moving type IV bursts in our study were mostly associated with “Fast” and “Wide” CMEs (∼52%), similar to type II radio bursts. Contrary to type II bursts, stationary type IV bursts have a more uniform association with all CME types.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A unique filament is identified in the Herschel maps of the Orion A giant molecular cloud. The filament, which we name the Stick, is ruler-straight and at an early evolutionary stage. Transverse position–velocity diagrams show two velocity components closing in on the Stick. The filament shows consecutive rings/forks in C<jats:sup>18</jats:sup>O (1−0) channel maps, which is reminiscent of structures generated by magnetic reconnection. We propose that the Stick formed via collision-induced magnetic reconnection (CMR). We use the magnetohydrodynamics code Athena++ to simulate the collision between two diffuse molecular clumps, each carrying an antiparallel magnetic field. The clump collision produces a narrow, straight, dense filament with a factor of &gt;200 increase in density. The production of the dense gas is seven times faster than freefall collapse. The dense filament shows ring/fork-like structures in radiative transfer maps. Cores in the filament are confined by surface magnetic pressure. CMR can be an important dense-gas-producing mechanism in the Galaxy and beyond.</jats:p>