Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We report new measurements of millimeter-wave power spectra in the angular multipole range 2000 ≤ <jats:italic>ℓ</jats:italic> ≤ 11,000 (angular scales <jats:inline-formula> <jats:tex-math> <?CDATA $5^{\prime} \gtrsim \theta \gtrsim 1^{\prime} $?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabd407ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>). By adding 95 and 150 GHz data from the low-noise 500 deg<jats:sup>2</jats:sup> SPTpol survey to the SPT-SZ three-frequency 2540 deg<jats:sup>2</jats:sup> survey, we substantially reduce the uncertainties in these bands. These power spectra include contributions from the primary cosmic microwave background, cosmic infrared background, radio galaxies, and thermal and kinematic Sunyaev–Zel’dovich (SZ) effects. The data favor a thermal SZ (tSZ) power at 143 GHz of <jats:inline-formula> <jats:tex-math> <?CDATA ${D}_{3000}^{\mathrm{tSZ}}=3.42\pm 0.54\,\,\mu {{\rm{K}}}^{2}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabd407ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> and a kinematic SZ (kSZ) power of <jats:inline-formula> <jats:tex-math> <?CDATA ${D}_{3000}^{\mathrm{kSZ}}=3.0\pm 1.0\,\,\mu {{\rm{K}}}^{2}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabd407ieqn3.gif" xlink:type="simple" /> </jats:inline-formula>. This is the first measurement of kSZ power at ≥3<jats:italic>σ</jats:italic>. However, different assumptions about the CIB or SZ models can reduce the significance down to 2.4<jats:italic>σ</jats:italic> in the worst case. We study the implications of the measured kSZ power for the epoch of reionization under the Calabrese et al. model for the kSZ power spectrum and find the duration of reionization to be <jats:inline-formula> <jats:tex-math> <?CDATA ${\rm{\Delta }}{z}_{\mathrm{re}}={1.1}_{-0.7}^{+1.6}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabd407ieqn4.gif" xlink:type="simple" /> </jats:inline-formula> (<jats:inline-formula> <jats:tex-math> <?CDATA ${\rm{\Delta }}{z}_{\mathrm{re}}\lt 4.1$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabd407ieqn5.gif" xlink:type="simple" /> </jats:inline-formula> at 95% confidence), when combined with our previously published tSZ bispectrum measurement. The upper limit tightens to <jats:inline-formula> <jats:tex-math> <?CDATA ${\rm{\Delta }}{z}_{\mathrm{re}}\lt 3.2$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabd407ieqn6.gif" xlink:type="simple" /> </jats:inline-formula> if the assumed homogeneous kSZ power is increased by 25% (∼0.5 <jats:italic>μ</jats:italic>K<jats:sup>2</jats:sup>) and relaxes to <jats:inline-formula> <jats:tex-math> <?CDATA ${\rm{\Delta }}{z}_{\mathrm{re}}\lt 5.2$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabd407ieqn7.gif" xlink:type="simple" /> </jats:inline-formula> if the homogeneous kSZ power is decreased by the same amount.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Ancient, very metal-poor (VMP) stars offer a window into the earliest epochs of galaxy formation and assembly. We combine data from the H3 Spectroscopic Survey and Gaia to measure metallicities, abundances of <jats:italic>α</jats:italic> elements, stellar ages, and orbital properties of a sample of 482 VMP ([Fe/H] &lt; −2) stars in order to constrain their origins. This sample is confined to 1 ≲ ∣<jats:italic>Z</jats:italic>∣ ≲ 3 kpc from the Galactic plane. We find that &gt;70% of VMP stars near the disk are on prograde orbits and this fraction increases toward lower metallicities. This result is unexpected if metal-poor stars are predominantly accreted from many small systems with no preferred orientation, as such a scenario would imply a mostly isotropic distribution. Furthermore, we find there is some evidence for higher fractions of prograde orbits among stars with lower [<jats:italic>α</jats:italic>/Fe]. Isochrone-based ages for main-sequence turn-off stars reveal that these VMP stars are uniformly old (≈12 Gyr) irrespective of the <jats:italic>α</jats:italic> abundance and metallicity, suggesting that the metal-poor population was not born from the same well-mixed gas disk. We speculate that the VMP population has a heterogeneous origin, including both in situ formation in the ancient disk and accretion from a satellite with the same direction of rotation as the ancient disk at early times. Our precisely measured ages for these VMP stars on prograde orbits show that the Galaxy has had a relatively quiescent merging history over most of cosmic time, and implies the angular momentum alignment of the Galaxy has been in place for at least 12 Gyr.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In an earlier analysis of Ca–K spectroheliograms obtained at the Kodaikanal Observatory, the “Good” images were used to investigate variations in the chromosphere. However, the contrast of the images varied on a day-to-day basis. We have developed a new methodology to generate images to form a uniform time series. We adjusted each image’s contrast until the FWHM of the normalized intensity distribution attained a value between 0.10 and 0.11. This “equal-contrast technique” is expected to compensate for the change of emulsion, development, and contrast of the images due to centering of the Ca–K line on the exit slit and sky transparency. In addition, this procedure will correct variations in density-to-intensity conversion for different images. We find that the correlation between sunspot and Ca–K line data improves to a large extent. For example, the correlation coefficient (CC) between monthly averaged sunspots and Ca–K plage areas for the equal-contrast data reaches 0.9 compared to 0.75 for the “Good” data with unequal contrast. The CC for equal-contrast images improves to ∼0.78 from ∼0.46 for the “Okay” data with unequal contrast. Even the CC between the plage area and the daily sunspot number is 0.85 for 100 years of data. This methodology also permits us, for the first time, to study the variations in enhanced, active, and quiet networks with time with high accuracy over about a century. Further, this procedure can be used to combine data from different observatories to make a long time series.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We develop a method to identify cosmic voids from the matter density field by adopting a physically motivated concept that voids are the counterpart of massive clusters. To prove the concept we use a pair of ΛCDM simulations, a reference and its initial density-inverted mirror simulation, and study the relation between the effective size of voids and the mass of corresponding clusters. Galaxy cluster-scale dark matter halos are identified in the Mirror simulation at <jats:italic>z</jats:italic> = 0 by linking dark matter particles. The void corresponding to each cluster is defined in the Reference simulation as the region occupied by the member particles of the cluster. We study the voids corresponding to the halos more massive than 10<jats:sup>13</jats:sup> <jats:italic>h</jats:italic> <jats:sup>−1</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. We find a power-law scaling relation between the void size and the corresponding cluster mass. Voids with a corresponding cluster mass above 10<jats:sup>15</jats:sup> <jats:italic>h</jats:italic> <jats:sup>−1</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> occupy ∼1% of the total simulated volume, whereas this fraction increases to ∼54% for voids with a corresponding cluster mass above 10<jats:sup>13</jats:sup> <jats:italic>h</jats:italic> <jats:sup>−1</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. It is also found that the density profile of the identified voids follows a universal functional form. Based on these findings, we propose a method to identify cluster-counterpart voids directly from the matter density field without their mirror information by utilizing three parameters such as the smoothing scale, density threshold, and minimum core fraction. We recover voids corresponding to clusters more massive than 3 × 10<jats:sup>14</jats:sup> <jats:italic>h</jats:italic> <jats:sup>−1</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> at a 70%–74% level of completeness and reliability. Our results suggest that we are able to identify voids in a way to associate them with clusters of a particular mass scale.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present broadband X-ray spectroscopy of the energetic components that make up the supernova remnant (SNR) Kesteven 75 using concurrent 2017 August 17–20 XMM-Newton and NuSTAR observations, during which the pulsar PSR J1846−0258 is found to be in the quiescent state. The young remnant hosts a bright pulsar wind nebula powered by the highly energetic (<jats:inline-formula> <jats:tex-math> <?CDATA $\dot{E}=8.1\times {10}^{36}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabd32bieqn1.gif" xlink:type="simple" /> </jats:inline-formula> erg s<jats:sup>−1</jats:sup>) isolated, rotation-powered pulsar, with a spin-down age of only <jats:inline-formula> <jats:tex-math> <?CDATA $P/2\dot{P}\sim 728\,\mathrm{yr}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabd32bieqn2.gif" xlink:type="simple" /> </jats:inline-formula>. Its inferred magnetic field (<jats:italic>B</jats:italic> <jats:sub> <jats:italic>s</jats:italic> </jats:sub> = 4.9 × 10<jats:sup>13</jats:sup> G) is the largest known for these objects, and is likely responsible for intervals of flare and burst activity, suggesting a transition between/to a magnetar state. The pulsed emission from PSR J1846−0258 is well-characterized in the 2–50 keV range by a power-law model with photon index Γ<jats:sub>PSR</jats:sub> = 1.24 ± 0.09 and a 2–10 keV unabsorbed flux of (2.3 ± 0.4) × 10<jats:sup>−12</jats:sup> erg s<jats:sup>−1</jats:sup> cm<jats:sup>−2</jats:sup>. We find no evidence for an additional non-thermal component above 10 keV in the current state, as would be typical for a magnetar. Compared to the Chandra pulsar spectrum, the intrinsic pulsed fraction is 71 ± 16% in 2–10 keV band. A power-law spectrum for the pulsar wind nebulae (PWN) yields Γ<jats:sub>PWN</jats:sub> = 2.03 ± 0.02 in the 1–55 keV band, with no evidence of curvature in this range, and a 2–10 keV unabsorbed flux (2.13 ± 0.02) × 10<jats:sup>−11</jats:sup> erg s<jats:sup>−1</jats:sup> cm<jats:sup>−2</jats:sup>. The NuSTAR data reveal evidence for a hard X-ray component dominating the SNR spectrum above 10 keV that we attribute to a dust-scattered PWN component. We model the dynamical and radiative evolution of the Kes 75 system to estimate the birth properties of the neutron star, the energetics of its progenitor, and properties of the PWN. This suggests that the progenitor of Kes 75 was originally in a binary system which transferred most of its mass to a companion before exploding.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Magnetic reconnection modulated by nonlocal disturbances in the solar atmosphere has been investigated theoretically, but rarely observed. In this study, employing H<jats:italic>α</jats:italic> and extreme ultraviolet (EUV) images and line-of-sight magnetograms, we report the acceleration of reconnection by an adjacent filament eruption. In H<jats:italic>α</jats:italic> images, four groups of chromospheric fibrils are observed to form a saddle-like structure. Among them, two groups of fibrils converge and reconnect. Two newly reconnected fibrils then form and retract away from the reconnection region. In EUV images, similar structures and evolution of coronal loops are identified. The current sheet forms repeatedly at the interface of reconnecting loops, with a width and length of 1–2 and 5.3–7.2 Mm and a reconnection rate of 0.18–0.3. It appears in the EUV low-temperature channels, with an average differential emission measure (DEM) weighed temperature and EM of 2 MK and 2.5 × 10<jats:sup>27</jats:sup> cm<jats:sup>−5</jats:sup>. Plasmoids appear in the current sheet and propagate along it, and then further along the reconnection loops. The filament, located to the southeast of the reconnection region, erupts and pushes away the loops covering the reconnection region. Thereafter, the current sheet has a width and length of 2 and 3.5 Mm and a reconnection rate of 0.57. It becomes much brighter and appears in the EUV high-temperature channels, with an average DEM-weighed temperature and EM of 5.5 MK and 1.7 × 10<jats:sup>28</jats:sup> cm<jats:sup>−5</jats:sup>. In the current sheet, more hotter plasmoids form. More thermal and kinetic energy is hence converted. These results suggest that the reconnection is significantly accelerated by the propagating disturbance caused by the nearby filament eruption.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We determine solar energetic particle (SEP) event He/H peak intensity ratios <jats:italic>A</jats:italic> <jats:sub>He</jats:sub> observed in the four energy channels of the SOHO EPHIN detector covering 4–53 MeV nuc<jats:sup>−1</jats:sup>. Those SEP <jats:italic>A</jats:italic> <jats:sub>He</jats:sub> values range over two orders of magnitude for 43 large western hemisphere SEP events through the period 1997–2017. <jats:italic>A</jats:italic> <jats:sub>He</jats:sub> of each SEP event are compared with average solar wind (SW) <jats:italic>A</jats:italic> <jats:sub>He</jats:sub> values measured for 8 hr after the SEP event onsets with the solar wind experiment Faraday Cup instrument on Wind. <jats:italic>A</jats:italic> <jats:sub>He</jats:sub> in the 4–8 and 8–21 MeV nuc<jats:sup>−1</jats:sup> range are significantly correlated with SW<jats:italic> A</jats:italic> <jats:sub>He</jats:sub> (CC = 0.45 and 0.41), but less so in the 21–41 and 41–53 MeV nuc<jats:sup>−1</jats:sup> range, where uncertainties of the <jats:italic>A</jats:italic> <jats:sub>He</jats:sub> values are higher. Median SEP <jats:italic>A</jats:italic> <jats:sub>He</jats:sub> values decline slightly with increasing energy and are ≤0.5 their associated SW values. Both median SEP and SW <jats:italic>A</jats:italic> <jats:sub>He</jats:sub> decline by a factor of ∼2 from the 27 events of cycle 23 to the 16 of cycle 24. Those results suggest a connection between the SW and the seed population of SEP events. An unexpected result is that SEP <jats:italic>A</jats:italic> <jats:sub>He</jats:sub> increases with event peak intensities in our 43 events as He peak intensities increase faster than those of H in larger events.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Gravitational-wave astronomy provides a unique new way to study the expansion history of the universe. In this work, we investigate the impact future gravitational-wave observatories will have on cosmology. Third-generation observatories like the Einstein Telescope and Cosmic Explorer will be sensitive to essentially all of the binary black hole coalescence events in the universe. Recent work by Farr et al. points out that features in the stellar-mass black hole population break the mass–redshift degeneracy, facilitating precise determination of the Hubble parameter without electromagnetic counterparts or host galaxy catalogs. Using a hierarchical Bayesian inference model, we show that with one year of observations by the Einstein Telescope, the Hubble constant will be measured to ≲1%. We also show that this method can be used to perform Bayesian model selection between cosmological models. As an illustrative example, we find that a decisive statement can be made comparing the ΛCDM and RHCT cosmological models using two weeks of data from the Einstein Telescope.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Quantification of the significance of a candidate multi-messenger detection of cosmic events is an emerging need in the astrophysics and astronomy communities. In this paper we show that a model-independent optimal search does not exist, and we present a general Bayesian method for the optimal model-dependent search, which is scalable to any number and any kind of messengers, and applicable to any model. In the end, we demonstrate it through an example for a joint gravitational wave, high-energy neutrino, short gamma-ray burst event search; which has not been examined heretofore.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the results of two-dimensional radiation-hydrodynamic simulations of expanding supernova ejecta with a central energy source. As suggested in previous multidimensional hydrodynamic simulations, a sufficiently powerful central energy source can blow away the expanding supernova ejecta, leading to efficient mixing of stratified layers in the ejecta. We assume that the energy injection is realized in the form of nonthermal radiation from the wind nebula embedded at the center of the ejecta. We found that the multidimensional mixing in the ejecta assists the injected nonthermal radiation escaping from the ejecta. When the nonthermal radiation is absorbed by the ejecta, it is converted into bright thermal radiation or is consumed as the kinetic energy of the supernova ejecta. We found that central energy sources with injection timescale similar to the photon diffusion timescale realize an efficient conversion of the injected energy into thermal radiation. On the other hand, rapid energy injection ends up accelerating the ejecta rather than giving rise to bright thermal emission. This remarkable difference potentially explains the diversity of energetic supernovae including broad-lined Ic and superluminous supernovae.</jats:p>