Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We analyzed Suzaku and Chandra observations of the soft diffuse X-ray background toward four sight lines with the goal of characterizing the X-ray emission from the Milky Way circumgalactic medium (CGM). We identified two thermal components of the CGM, one at a uniform temperature of <jats:italic>kT</jats:italic> = 0.176 ± 0.008 keV and the other at temperatures in the range <jats:italic>kT</jats:italic> = 0.65–0.90 keV. The uniform lower-temperature component is consistent with the Galaxy’s virial temperature (∼10<jats:sup>6</jats:sup> K). The temperatures of the hotter components are similar to that recently discovered (∼10<jats:sup>7</jats:sup> K) in the sight line to blazar 1ES 1553+113, passing close to the Fermi bubble. Alternatively, the spectra can be described by just one lower-temperature component with supersolar neon abundance, once again similar to that found in the 1ES 1553+113 sight line. The additional hot component or the overabundance of Ne is required at a significance of &gt;4<jats:italic>σ</jats:italic>, but we cannot distinguish between the two possibilities. These results show that the supervirial temperature gas or an enhanced Ne abundance in the warm-hot gas in the CGM is widespread, and these are not necessarily related to the Fermi bubble.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the first results from the Mapping Obscuration to Reionization with ALMA (MORA) survey, the largest Atacama Large Millimeter/submillimeter Array (ALMA) blank-field contiguous survey to date (184 arcmin<jats:sup>2</jats:sup>) and the only at 2 mm to search for dusty star-forming galaxies (DSFGs). We use the 13 sources detected above 5<jats:italic>σ</jats:italic> to estimate the first ALMA galaxy number counts at this wavelength. These number counts are then combined with the state-of-the-art galaxy number counts at 1.2 and 3 mm and with a backward evolution model to place constraints on the evolution of the IR luminosity function and dust-obscured star formation in the past 13 billion years. Our results suggest a steep redshift evolution on the space density of DSFGs and confirm the flattening of the IR luminosity function at faint luminosities, with a slope of <jats:inline-formula> <jats:tex-math> <?CDATA ${\alpha }_{\mathrm{LF}}=-{0.42}_{-0.04}^{+0.02}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabdb27ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>. We conclude that the dust-obscured component, which peaks at <jats:italic>z</jats:italic> ≈ 2–2.5, has dominated the cosmic history of star formation for the past ∼12 billion years, back to <jats:italic>z</jats:italic> ∼ 4. At <jats:italic>z</jats:italic> = 5, the dust-obscured star formation is estimated to be ∼35% of the total star formation rate density and decreases to 25%–20% at <jats:italic>z</jats:italic> = 6–7, implying a minor contribution of dust-enshrouded star formation in the first billion years of the universe. With the dust-obscured star formation history constrained up to the end of the epoch of reionization, our results provide a benchmark to test galaxy formation models, to study the galaxy mass assembly history, and to understand the dust and metal enrichment of the universe at early times.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Maunder Minimum (1645–1715; hereafter MM) is generally considered as the only grand minimum in the chronological coverage of telescopic sunspot observations. Characterized by scarce sunspot occurrences and their asymmetric concentrations in the southern solar hemisphere, the MM has frequently been associated with a special state of solar dynamo activity. As such, it is important to analyze contemporary observational records and improve our understanding of this peculiar interval, whereas the original records are frequently preserved in historical archives and can be difficult to access. In this study, we consult historical archives in the National Library of Russia, St. Petersburg, and analyze a series of sunspot observations conducted at the Eimmart Observatory from 1681 to 1709, which is the second-richest sunspot data set produced during the MM, following La Hire's series, among existing data sets. We have further extended our analyses to neighboring observations to extend our investigations up to 1718. We first analyze source documents and descriptions of observational instruments. Our analyses have significantly revised the existing data set, removed contaminations, and updated and labeled them as Eimmart Observatory (78 days), Altdorf Observatory (4 days), Hoffmann (22 days), and Wideburg (25 days). The revisions have updated the temporal coverage of the contemporary sunspot observations from 73.4% to 66.9% from 1677 to 1709. We have also derived the positions of the observed sunspot groups in comparison with contemporary observations. Our results indicate hemispheric asymmetry in the MM and recovery of sunspot groups in both hemispheres after 1716, supporting the common paradigm of the MM.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present Ca–CN–CH–NH photometry for the well-known globular cluster (GC) M3 (NGC 5272). We show new evidence for two M3 populations with distinctly different carbon and nitrogen abundances, seen in a sharp division between CN-weak and CN-strong red-giant branches (RGBs) in M3. The CN-strong population shows a C–N anticorrelation that is a natural consequence of the CN cycle, while the CN-weak population shows at most a very weak C–N anticorrelation. Additionally, the CN-weak population exhibits an elongated spatial distribution that is likely linked to its fast rotation. Our derived metallicities reveal bimodal distributions in both populations, with 〈[Fe/H]〉 ≈ −1.60 and −1.45, which appear to be responsible for the discrete double RGB bumps in the CN-weak population and the large <jats:inline-formula> <jats:tex-math> <?CDATA ${W}_{{\rm{F}}275{\rm{W}}-{\rm{F}}814{\rm{W}}}^{1G}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabd948ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> range. From this discovery, we propose that M3 consists of two GCs, namely C1 (23%, 〈[Fe/H]〉 ≈ −1.60) and C2 (77%, 〈[Fe/H]〉 ≈ −1.45), each of which has its own C–N anticorrelation and structural and kinematical properties, which are strong indications of independent systems in M3. The fractions of the CN-weak population for both C1 and C2 are high compared to Galactic GCs but they are in good agreement with GCs in the Magellanic Clouds. We suggest that M3 is a merger remnant of two GCs, most likely in a dwarf galaxy environment, and accreted to our Galaxy later in time. This is consistent with recent proposals of an ex situ origin for M3.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We carry out general relativistic ray-tracing radiative-transfer calculations to study whether a localized emission from plasma rings created at the stagnation surface in the jet funnel, to which we refer as stagnation rings, can explain the ring image of M87* observed by the Event Horizon Telescope (EHT) 2017. The resultant images consist of the direct image of the stagnation rings and the ring images formed via the strong deflection by the black hole (BH) gravity, to which we refer as quasi photon-ring. For the model with the BH spin <jats:italic>a</jats:italic> <jats:sub>*</jats:sub> = 0.99, the direct image of the counter-jet and quasi photon-ring are almost coincident to the photon ring with diameter ∼ 40 <jats:italic>μ</jats:italic>as, while the approaching jet shows the small ring image inside them. The synthetic observation image assumes that the EHT2017 array is consistent with that observed in M87*, because the array is a bit sparse to detect the inner ring image. This indicates that the ring image in M87* may contain the important feature of the jet bases in addition to the photon ring. We find that forthcoming EHT observations can resolve the stagnation ring image and may enable us to explore the plasma-injection mechanism in the jet funnel.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The diffuse cosmic supernova neutrino background (DSNB) is an observational target of the gadolinium-loaded Super-Kamiokande (SK) detector and the forthcoming JUNO and Hyper-Kamiokande detectors. Current predictions are hampered by our still incomplete understanding of the supernova (SN) explosion mechanism and of the neutron star (NS) equation of state and maximum mass. In our comprehensive study we revisit this problem on grounds of the landscapes of successful and failed SN explosions obtained by Sukhbold et al. and Ertl et al. with parameterized one-dimensional neutrino engines for large sets of single-star and helium-star progenitors, with the latter serving as a proxy for binary evolution effects. Besides considering engines of different strengths, leading to different fractions of failed SNe with black hole (BH) formation, we also vary the NS mass limit and the spectral shape of the neutrino emission and include contributions from poorly understood alternative NS formation channels, such as accretion-induced and merger-induced collapse events. Since the neutrino signals of our large model sets are approximate, we calibrate the associated degrees of freedom by using state-of-the-art simulations of proto-NS cooling. Our predictions are higher than other recent ones because of a large fraction of failed SNe with long delay to BH formation. Our best-guess model predicts a DSNB <jats:inline-formula> <jats:tex-math> <?CDATA ${\bar{\nu }}_{{\rm{e}}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabd54eieqn1.gif" xlink:type="simple" /> </jats:inline-formula>-flux of <jats:inline-formula> <jats:tex-math> <?CDATA ${28.8}_{-10.9}^{+24.6}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabd54eieqn2.gif" xlink:type="simple" /> </jats:inline-formula> cm<jats:sup>−2</jats:sup> s<jats:sup>−1</jats:sup> with <jats:inline-formula> <jats:tex-math> <?CDATA ${6.0}_{-2.1}^{+5.1}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabd54eieqn3.gif" xlink:type="simple" /> </jats:inline-formula> cm<jats:sup>−2</jats:sup> s<jats:sup>−1</jats:sup> in the favorable measurement interval of [10, 30] MeV and <jats:inline-formula> <jats:tex-math> <?CDATA ${1.3}_{-0.4}^{+1.1}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabd54eieqn4.gif" xlink:type="simple" /> </jats:inline-formula> cm<jats:sup>−2</jats:sup> s<jats:sup>−1</jats:sup> with <jats:inline-formula> <jats:tex-math> <?CDATA ${\bar{\nu }}_{{\rm{e}}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabd54eieqn5.gif" xlink:type="simple" /> </jats:inline-formula> energies &gt; 17.3 MeV, which is roughly a factor of two below the current SK limit. The uncertainty range is dominated by the still insufficiently constrained cosmic rate of stellar core-collapse events.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a detailed single-pulse analysis for PSR B1929+10 based on observations with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The main pulse (MP) and interpulse (IP) are found to be modulated with a periodicity of ∼12 times the pulsar’s rotational period (<jats:italic>P</jats:italic>). The ∼12<jats:italic>P</jats:italic> modulation is confirmed as a periodic amplitude modulation instead of systematic drifting. The periodic amplitude modulation in the IP is found to be anti-correlated with that in the weak preceding component of the MP (MP_<jats:sc>i</jats:sc>), but correlated with that in the first two components of the MP (MP_<jats:sc>ii</jats:sc>), which implies that the modulation patterns in the IP and the MP are phase-locked. What is more interesting is that the modulation in MP_<jats:sc>ii</jats:sc> is delayed from that in the IP by about 1<jats:italic>P</jats:italic>. Furthermore, high-sensitivity observations by FAST reveal that weak emission exists between the MP and the IP. In addition, we confirm that the separation between the IP and the MP is independent of radio frequency. The above results are a conundrum for pulsar theories and cannot be satisfactorily explained by the current pulsar models. Therefore, our results observed with FAST provide an opportunity to probe the structure of pulsar emission and the neutron star’s magnetosphere.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We have investigated the chemistry of dense interstellar clouds and found new bistable solutions in the nitrogen and carbon chemistries. We identify the autocatalytic processes that are present in the pure, reduced, chemical networks and find, as previously found for oxygen chemistry, that He<jats:sup>+</jats:sup> plays an important role. The applicability of these results to astronomical environments is briefly discussed. The bistable solutions found for carbon chemistry occur for low densities and high ionization fractions that are not compatible with those found in cold, dense clouds. Bistability in the pure nitrogen chemistry occurs for conditions that are relevant for prestellar cores in which significant CO depletion has taken place. We conclude that several autocatalyses are embedded in gas-phase interstellar chemistry and that many more are potentially present.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Is there oceanic superrotation on exoplanets? Atmospheric superrotation, characterized by west-to-east winds over the equator, is a common phenomenon in the atmospheres of Venus, Titan, Saturn, Jupiter, and tidally locked exoplanets. The stratospheric atmosphere of Earth is also superrotating during the westerly phase of the quasi-biennial oscillation. However, whether the same phenomenon can occur in the ocean is poorly known. Through numerical simulations, here we show that oceanic superrotation does occur on tidally locked terrestrial planets around low-mass stars. Its formation (spun up from rest) is associated with surface winds, the equatorward momentum convergence by Rossby waves, and the eastward propagation of Kelvin waves in the ocean. Its maintenance is driven by equatorward momentum transports of coupled Rossby–Kelvin waves in the ocean excited from the uneven stellar radiation distribution. The width of the superrotation is mainly constrained by the Rossby deformation radius in the ocean, while its strength is more complex. Many factors can influence the strength, including planetary rotation rate, stellar flux, greenhouse gas concentration, seawater salinity, and bottom drag, but a scaling theory for the strength of the oceanic superrotation is lacking. This work confirms that oceanic superrotation can occur on tidally locked terrestrial planets with seawater oceans and suggests that it may also occur on tidally locked hot planets with magma oceans that will possibly be observed in the near future.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The expansion index and relative contact discontinuity positions of young type Ia supernova remnants (SNRs) evolving in a turbulent medium are investigated via implementing two-dimensional cylindrical magnetohydrodynamic simulations. In our simulations, two kinds of initial ejecta density profiles are considered: a power-law (PL) profile and an exponential (Exp) profile; large-scale density and magnetic field fluctuations are calculated and mapped into the computational domain before the simulations; the back reaction of the accelerated particles is mimicked through a time-dependent effective adiabatic index <jats:italic>γ</jats:italic> <jats:sub>eff</jats:sub>(<jats:italic>n</jats:italic>, <jats:italic>t</jats:italic>). Our simulation results reveal that the density distributions and magnetic field structures have similar results for both initial profiles. Concerning the expansion index, both the PL and Exp profiles exhibit significant azimuthal variations along the remnant periphery, while the Exp profile manifests itself in a quick path down to the Sedov value as time proceeds. The derived expansion index distributions with both initial profiles are compatible with observations of two typical young type Ia SNRs: SN 1006 and Tycho. As for the relative contact discontinuity positions, when <jats:italic>γ</jats:italic> <jats:sub>eff</jats:sub>(<jats:italic>n</jats:italic>, <jats:italic>t</jats:italic>) works, the derived profiles of both scenarios are globally compatible with the observations despite some deviations. Besides, there are no obvious ejecta protrusions beyond the forward shock, with a lowest derived ratio reaching ∼1.01–1.02 for both initial profiles. Moreover, for purposes of comparison, we have also considered two supplementary scenarios: (1) the aforementioned two density profiles expanding in a homogeneous medium, and (2) a uniform ejecta profile evolving in a turbulent medium.</jats:p>