Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>The Tibet AS<jats:italic>γ</jats:italic> experiment has measured a <jats:italic>γ</jats:italic>-ray flux of supernova remnant G106.3+2.7 of up to 100 TeV, suggesting it is potentially a “PeVatron.” Challenges arise when the hadronic scenario requires a hard proton spectrum (with spectral index ≈1.8), while usual observations and numerical simulations prefer a soft proton spectrum (with spectral index ≥2). In this paper, we explore an alternative scenario to explain the <jats:italic>γ</jats:italic>-ray spectrum of G106.3+2.7 within the current understanding of acceleration and escape processes. We consider that cosmic ray particles are scattered by turbulence driven by Bell instabilities. The resulting hadronic <jats:italic>γ</jats:italic>-ray spectrum is novel, dominating the contribution to the emission above 10 TeV, and can explain the bizarre broadband spectrum of G106.3+2.7 in combination with leptonic emission from the remnant.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We have observed the young protostellar system NGC 2264 CMM3 in the 1.3 mm and 2.0 mm bands at a resolution of about 0.″1 (70 au) with ALMA. The structures of two distinct components, CMM3A and CMM3B, are resolved in the continuum images of both bands. CMM3A has an elliptical structure extending along the direction almost perpendicular to the known outflow, while CMM3B reveals a round shape. We have fitted two 2D Gaussian components to the elliptical structure of CMM3A and CMM3B and have separated the disk and envelope components for each source. The spectral index <jats:italic>α</jats:italic> between 2.0 and 0.8 mm is derived to be 2.4–2.7 and 2.4–2.6 for CMM3A and CMM3B, respectively, indicating optically thick dust emission and/or grain growth. A velocity gradient in the disk/envelope direction is detected for CMM3A in the CH<jats:sub>3</jats:sub>CN, CH<jats:sub>3</jats:sub>OH, and <jats:sup>13</jats:sup>CH<jats:sub>3</jats:sub>OH lines detected in the 1.3 mm band, which can be interpreted as the rotation of the disk/envelope system. From this result, the protostellar mass of CMM3A is roughly evaluated to be 0.1–0.5 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> by assuming Keplerian rotation. The mass accretion rate is thus estimated to be 5 × 10<jats:sup>−5</jats:sup> − 4 × 10<jats:sup>−3</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup>, which is higher than the typical mass accretion rate of low-mass protostars. The OCS emission line shows a velocity gradient in both outflow direction and disk/envelope direction. A hint of outflow rotation is found, and the specific angular momentum of the outflow is estimated to be comparable to that of the disk. These results provide us with novel information on the initial stage of a binary/multiple system.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Coronal upflows at the edges of active regions (ARs), which are a possible source of slow solar wind, have been found to connect with dynamics in the transition region. To infer at what scale transition region dynamics connect to AR upflows, we investigate the statistical properties of the small-scale dynamics in the transition region underneath the upflows at the edge of NOAA Active Region 11934. With observations from the Interface Region Imaging Spectrograph (IRIS), we found that the Si <jats:sc>iv</jats:sc> 1403 Å Doppler map consists of numerous blueshifted and redshifted patches mostly with sizes less than 1 Mm<jats:sup>2</jats:sup>. The blueshifted structures in the transition region tend to be brighter than the redshifted ones, but their nonthermal velocities have no significant difference. With the SWAMIS feature-tracking procedure, we found in IRIS slit-jaw 1400 Å images that dynamic bright dots with an average size of about 0.3 Mm<jats:sup>2</jats:sup> and lifetimes of mostly less than 200 s were spread all over the region. Most of the bright dots appear to be localized, without a clear signature of plasma propagation to a long distance on the projection plane. Surge-like motions with speeds of about 15 km s<jats:sup>−1</jats:sup> could be seen in some events at the boundaries of the upflow region, where the magnetic field appeared to be inclined. We conclude that the transition region dynamics connecting to coronal upflows should occur in at a very fine scale, suggesting that the corresponding coronal upflows should also be highly structured. It is also plausible that the transition region dynamics might just act as stimulation at the coronal base, which then drives the upflows in the corona.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We leverage the 1 pc spatial resolution of the Leike et al. three-dimensional (3D) dust map to characterize the 3D structure of nearby molecular clouds (<jats:italic>d</jats:italic> ≲ 400 pc). We start by “skeletonizing” the clouds in 3D volume density space to determine their “spines,” which we project on the sky to constrain cloud distances with ≈1% uncertainty. For each cloud, we determine an average radial volume density profile around its 3D spine and fit the profiles using Gaussian and Plummer functions. The radial volume density profiles are well described by a two-component Gaussian function, consistent with clouds having broad, lower-density outer envelopes and narrow, higher-density inner layers. The ratio of the outer to inner envelope widths is ≈3:1. We hypothesize that these two components may be tracing a transition between atomic and diffuse molecular gas or between the unstable and cold neutral medium. Plummer-like models can also provide a good fit, with molecular clouds exhibiting shallow power-law wings with density, <jats:italic>n</jats:italic>, falling off like <jats:italic>n</jats:italic> <jats:sup>−2</jats:sup> at large radii. Using Bayesian model selection, we find that parameterizing the clouds’ profiles using a single Gaussian is disfavored. We compare our results with two-dimensional dust extinction maps, finding that the 3D dust recovers the total cloud mass from integrated approaches with fidelity, deviating only at higher levels of extinction (<jats:italic>A</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub> ≳ 2–3 mag). The 3D cloud structure described here will enable comparisons with synthetic clouds generated in simulations, offering unprecedented insight into the origins and fates of molecular clouds in the interstellar medium.</jats:p>