Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Although the spatial curvature has been precisely determined via observations of the cosmic microwave background by the Planck satellite, it still suffers from the well-known cosmic curvature tension. As a standard siren, gravitational waves (GWs) from binary neutron star mergers provide a direct way to measure the luminosity distance. In addition, the accelerating expansion of the universe may cause an additional phase shift in the gravitational waveform, which will allow us to measure the acceleration parameter. This measurement provides an important opportunity to determine the curvature parameter Ω<jats:sub> <jats:italic>k</jats:italic> </jats:sub> in the GW domain based on the combination of two different observables for the same objects at high redshifts. In this study, we investigate how such an idea could be implemented with the future generation of the space-based Decihertz Interferometer Gravitational-wave Observatory (DECIGO) in the framework of two model-independent methods. Our results show that DECIGO could provide a reliable and stringent constraint on the cosmic curvature at a precision of ΔΩ<jats:sub> <jats:italic>k</jats:italic> </jats:sub> = 0.12, which is comparable to existing results based on different electromagnetic data. Our constraints are more stringent than the traditional electromagnetic method from the Pantheon sample of Type Ia supernovae, which shows no evidence for a deviation from a flat universe at <jats:italic>z</jats:italic> ∼ 2.3. More importantly, with our model-independent method, such a second-generation space-based GW detector would also be able to explore the possible evolution of Ω<jats:sub> <jats:italic>k</jats:italic> </jats:sub> with redshift, through direct measurements of cosmic curvature at different redshifts (<jats:italic>z</jats:italic> ∼ 5). Such a model-independent Ω<jats:sub> <jats:italic>k</jats:italic> </jats:sub> reconstruction to the distant past could become a milestone in gravitational-wave cosmology.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>HESS J1843–033 is a very high energy gamma-ray source whose origin remains unidentified. This work presents, for the first time, the energy spectrum of gamma rays beyond 100 TeV from the HESS J1843–033 region using the data recorded by the Tibet air shower array and its underground muon detector array. A gamma-ray source with an extension of 0.°34 ± 0.°12 is successfully detected above 25 TeV at (<jats:italic>α</jats:italic>, <jats:italic>δ</jats:italic>) = (281.°09 ± 0.°10, −3.°76 ± 0.°09) near HESS J1843–033 with a statistical significance of 6.2<jats:italic>σ</jats:italic>, and the source is named TASG J1844–038. The position of TASG J1844–038 is consistent with those of HESS J1843–033, eHWC J1842–035, and LHAASO J1843–0338. The measured gamma-ray energy spectrum in 25 TeV &lt; <jats:italic>E</jats:italic> &lt; 130 TeV is described with <jats:inline-formula> <jats:tex-math> <?CDATA ${dN}/{dE}=(9.70\pm 1.89)\times {10}^{-16}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="italic">dN</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi mathvariant="italic">dE</mml:mi> <mml:mo>=</mml:mo> <mml:mo stretchy="false">(</mml:mo> <mml:mn>9.70</mml:mn> <mml:mo>±</mml:mo> <mml:mn>1.89</mml:mn> <mml:mo stretchy="false">)</mml:mo> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>16</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac6ef4ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> (<jats:italic>E</jats:italic>/40 TeV)<jats:sup>−3.26±0.30</jats:sup> TeV<jats:sup>−1</jats:sup> cm<jats:sup>−2</jats:sup> s<jats:sup>−1</jats:sup>, and the spectral fit to the combined spectra of HESS J1843–033, LHAASO J1843–0338, and TASG J1844–038 implies the existence of a cutoff at 49.5 ± 9.0 TeV. Associations of TASG J1844–038 with SNR G28.6–0.1 and PSR J1844–0346 are also discussed in detail for the first time.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a study of the stellar populations of globular clusters (GCs) in the Virgo Cluster core with a homogeneous spectroscopic catalog of 692 GCs within a major-axis distance <jats:italic>R</jats:italic> <jats:sub>maj</jats:sub> = 840 kpc from M87. We investigate radial and azimuthal variations in the mean age, total metallicity, [Fe/H], and <jats:italic>α</jats:italic>-element abundance of blue (metal-poor) and red (metal-rich) GCs using their co-added spectra. We find that the blue GCs have a steep radial gradient in [Z/H] within <jats:italic>R</jats:italic> <jats:sub>maj</jats:sub> = 165 kpc, with roughly equal contributions from [Fe/H] and [<jats:italic>α</jats:italic>/Fe], and flat gradients beyond. By contrast, the red GCs show a much shallower gradient in [Z/H], which is entirely driven by [Fe/H]. We use GC-tagged Illustris simulations to demonstrate an accretion scenario where more massive satellites (with more metal- and <jats:italic>α</jats:italic>-rich GCs) sink further into the central galaxy than less massive ones, and where the gradient flattening occurs because of the low GC occupation fraction of low-mass dwarfs disrupted at larger distances. The dense environment around M87 may also cause the steep [<jats:italic>α</jats:italic>/Fe] gradient of the blue GCs, mirroring what is seen in the dwarf galaxy population. The progenitors of red GCs have a narrower mass range than those of blue GCs, which makes their gradients shallower. We also explore spatial inhomogeneity in GC abundances, finding that the red GCs to the northwest of M87 are slightly more metal-rich. Future observations of GC stellar population gradients will be useful diagnostics of halo merger histories.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The evolution of the dark energy (DE) density is a crucial quantity for understanding the nature of DE. Often, the quantity is described by the so-called equation of state; that is, the ratio of the DE pressure to its density. In this scenario, the DE density is always positive throughout cosmic history, and a negative value is not allowed. Assuming a homogeneous and isotropic universe, we reconstruct the DE density directly from observational data and investigate its evolution throughout cosmic history. We consider the latest Type Ia supernova, baryon acoustic oscillation, and cosmic chronometer data, and reconstruct the DE density in both flat and nonflat universes up to redshift <jats:italic>z</jats:italic> ∼ 3. The results are well in agreement with ΛCDM up to redshift <jats:italic>z</jats:italic> ∼ 1.5, but we see a weak sign of negative DE density at high redshifts.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present Atacama Large Millimeter/submillimeter Array observations at a spatial resolution of 0.″2 (60 pc) of CO emission from the Taffy galaxies (UGC 12914/5). The observations are compared with narrowband Pa<jats:italic>α</jats:italic>, mid-IR, radio continuum and X-ray imaging, plus optical spectroscopy. The galaxies have undergone a recent head-on collision, creating a massive gaseous bridge that is known to be highly turbulent. The bridge contains a complex web of narrow molecular filaments and clumps. The majority of the filaments are devoid of star formation, and fall significantly below the Kennicutt–Schmidt relationship for normal galaxies, especially for the numerous regions undetected in Pa<jats:italic>α</jats:italic> emission. Within the loosely connected filaments and clumps of gas we find regions of high velocity dispersion that appear gravitationally unbound for a wide range of likely values of <jats:italic>X</jats:italic> <jats:sub>CO</jats:sub>. Like the “Firecracker” region in the Antennae system, they would require extremely high external dynamical or thermal pressure to stop them dissipating rapidly on short crossing timescales of 2–5 Myr. We suggest that the clouds may be transient structures within a highly turbulent multiphase medium that is strongly suppressing star formation. Despite the overall turbulence in the system, stars seem to have formed in compact hotspots within a kiloparsec-sized extragalactic H <jats:sc>ii</jats:sc> region, where the molecular gas has a lower velocity dispersion than elsewhere, and shows evidence for a collision with an ionized gas cloud. Like the shocked gas in the Stephan’s Quintet group, the conditions in the Taffy bridge shows how difficult it is to form stars within a turbulent, multiphase, gas.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>TMC-1A is a protostellar source harboring a young protostar, IRAS 04365+2353, and shows highly asymmetric features of a few 100 au scale in its molecular emission lines. Blueshifted emission is much stronger in the CS (<jats:italic>J</jats:italic> = 5–4) line than redshifted emission. This asymmetry can be explained if the gas accretion is episodic and takes the form of cloudlet capture, given that the cloudlet is approaching toward us. The gravity of the protostar transforms the cloudlet into a stream and changes its velocity along the flow. The emission from the cloudlet should be blueshifted before the periastron, while it should be redshifted after the periastron. If a major part of cloudlet has not reached the periastron, the former should be dominant. We perform hydrodynamical simulations to examine the validity of the scenario. Our numerical simulations can reproduce the observed asymmetry if the orbit of the cloudlet is inclined to the disk plane. The inclination can explain the slow infall velocity observed in the C<jats:sup>18</jats:sup>O (<jats:italic>J</jats:italic> = 2–1) line emission. Such episodic accretion may occur in various protostellar cores since actual clouds could have inhomogeneous density distributions. We also discuss the implication of the cloudlet capture on observations of related objects.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Electrostatic dust lofting may be a common occurrence on small bodies in the solar system, whereby the upward electrostatic force on a grain is able to overcome the surface gravity and cohesion binding it to the surface. This electrostatic lofting may serve to redistribute and transport dust across the surface of these bodies to produce features such as dust ponds and lineations found on Eros, or even to rid bodies of small particles completely. Classical models, which distribute charge evenly across a dust grain, have historically predicted electric field strengths that are insufficient to loft dust. However, recent studies have developed grain-scale charging models that account for the buildup of charge in the microcavities of regolith and assume unequal distribution of charge on a dust grain. These models predict electric field strengths orders of magnitude larger than classical models, which may explain how electrostatic dust lofting occurs on small bodies. In this paper, we compare the grain-scale supercharging models developed by Zimmerman et al. and survey how the different parameters affect grain charging—namely, charge separation, grain size, and dielectric breakdown strength. Furthermore, we investigate how each of the charging models can be used to bound initial condition requirements such as charge and velocity for dust lofting to occur on these small bodies. Initial condition requirements are examined for a range of grain sizes, regolith cohesive strengths, and small body sizes.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Thermochemical equilibrium is one of the most commonly used assumptions in current exoplanet retrievals. As science operations with the James Webb Space Telescope (JWST) draw near and with the planned launch of Ariel, it is crucial to assess the underlying biases and assumptions made when applying self-consistent chemistry to spectral retrievals. Here we use the flexibility of TauREx 3.1 to cross-compare three state-of-the-art chemical equilibrium codes: ACE, FastChem, and GGchem. We simulate JWST spectra for ACE, FastChem, GGchem, and GGchem+condensation containing only the elements C, H, O, and N and spectra for FastChem, GGchem, and GGchem+condensation with a more extensive range of elements, giving seven simulated JWST spectra in total, and then cross-retrieve, giving a total of 56 retrievals. Our analysis demonstrates that, like-for-like, all chemical codes retrieve the correct parameters to within 1% of the truth. However, in retrievals, where the contained elements do not match the truth, parameters such as metallicity deviate by 20% while maintaining extremely low uncertainties &lt;1%, giving false confidence. This point is of major importance for future analyses on JWST and Ariel, highlighting that self-consistent chemical schemes that do not employ the proper assumptions (missing species, fixed elemental ratios, condensation) are at risk of confidently biasing interpretations. Free chemistry retrievals employing parametric descriptions of the chemical profiles can provide alternative unbiased explorations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The fact that the spatial velocity of pulsars is generally higher than that of their progenitor stars has bothered astronomers for nearly 50 years. It has been extensively argued that the high pulsar velocity should be acquired during a natal kick process on a timescale of 100 ms–10 s in the supernova explosion, in which some asymmetrical dynamical mechanism plays a key role. However, a satisfactory picture generally is still lacking. In this study, it is argued that the neutrino rocket model can well account for the high speed as well as the long-term evolution behaviors of pulsars. The neutrinos are emitted from superfluid vortex neutrons through the neutrino cyclotron radiation mechanism. The unique characters of left-handed neutrinos and right-handed antineutrinos resulting from the nonconservation of parity in weak interactions play a major role in the spatial asymmetry. The continuous acceleration of pulsars can be naturally explained by this model, which yields a maximum velocity surpassing 1000 km s<jats:sup>−1</jats:sup>. The alignment between the spinning axis and the direction of motion observed for the Crab pulsar (PSR 0531) and the Vela pulsar (PSR 0833) can be well accounted for. The observed correlation between the spin-down rate and the period of long-period pulsars with <jats:italic>P</jats:italic> ≳ 0.5 s can also be satisfactorily explained.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present recent updates and improvements of the graphical processing unit (GPU) <jats:italic>N</jats:italic>-body code GENGA. Modern state-of-the-art simulations of planet formation require the use of a very high number of particles to accurately resolve planetary growth and to quantify the effect of dynamical friction. At present the practical upper limit is in the range of 30,000–60,000 fully interactive particles; possibly a little more on the latest GPU devices. While the original hybrid symplectic integration method has difficulties to scale up to these numbers, we have improved the integration method by (i) introducing higher level changeover functions and (ii) code improvements to better use the most recent GPU hardware efficiently for such large simulations. We added treatments of non-Newtonian forces such as general relativity, tidal interaction, rotational deformation, the Yarkovsky effect, and Poynting–Robertson drag, as well as a new model to treat virtual collisions of small bodies in the solar system. We added new tools to GENGA, such as semi-active test particles that feel more massive bodies but not each other, a more accurate collision handling and a real-time openGL visualization. We present example simulations, including a 1.5 billion year terrestrial planet formation simulation that initially started with 65,536 particles, a 3.5 billion year simulation without gas giants starting with 32,768 particles, the evolution of asteroid fragments in the solar system, and the planetesimal accretion of a growing Jupiter simulation. GENGA runs on modern NVIDIA and AMD GPUs.</jats:p>