Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We present a study of the incidence of active galactic nucleus (AGN) in a sample of major merging systems at 0.3 &lt; <jats:italic>z</jats:italic> &lt; 2.5. Galaxies in this merger sample have projected separations between 3 and 15 kpc and are selected from the CANDELS/3D-Hubble Space Telescope catalogs using a peak-finding algorithm. AGNs in mergers and non-mergers are identified on the basis of their X-ray emission, optical lines, mid-infrared colors, and radio emission. Among galaxies with adequate measurements to find potential AGNs, we find a similar fraction of AGNs in mergers (16.4<jats:inline-formula> <jats:tex-math> <?CDATA ${\pm }_{3.1}^{5.0}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabdbb1ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>%) compared to the fraction found in non-merging galaxies (15.4% ± 0.6%). In mergers, this fraction is obtained by assuming that, in unresolved observations, only one of the merging galaxies is the AGN source (16 merging systems have at least one AGN galaxy). The similarity between the fractions is possibly due to the higher availability of cold gas at high redshifts, where the excess of nuclear activity as a result of merging is less important than at lower redshifts. Star-forming galaxies have a higher incidence of AGNs than quiescent galaxies. In particular, starbursts in mergers are the most common sites of AGN activity, since they present higher AGN fractions and black hole accretion rates. We find no clear correlation between the black hole accretion rate and the galaxy properties (i.e., star formation rate, stellar mass) in mergers and non-mergers. However, mergers seem to have a higher correlation with star formation than non-mergers, which possibly indicates that the merging process is starting to influence the star formation and AGN activity even at this pre-coalescence stage.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Over half of disk galaxies are barred, yet the mechanisms for bar formation and the lifetime of bar buckling remain poorly understood. In simulations, a thin bar undergoes a rapid (&lt;1 Gyr) event called “buckling,” during which the inner part of the bar is asymmetrically bent out of the galaxy plane and eventually thickens, developing a peanut/X-shaped profile when viewed side-on. Through analyzing stellar kinematics of <jats:italic>N</jats:italic>-body model snapshots of a galaxy before, during, and after the buckling phase, we confirm a distinct quadrupolar pattern of out-of-plane stellar velocities in nearly face-on galaxies. This kinematic signature of buckling allows us to identify five candidates of currently buckling bars among 434 barred galaxies in the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) Survey, an integral field unit spectroscopic survey that measures the composition and kinematic structure of nearby galaxies. The frequency of buckling events detected is consistent with the 0.5–1 Gyr timescale predicted by simulations. The five candidates we present more than double the total number of candidate buckling bars and are the only ones found using the kinematic signature.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Electromagnetic observations of gravitational-wave and high-energy neutrino events are crucial in understanding the physics of their astrophysical sources. X-ray counterparts are especially useful in studying the physics of the jet, the energy of the outflow, and the particle acceleration mechanisms in the system. Ultraviolet and optical observations can help us constrain the mass and velocity of the outflow and provide hints on the viewing angle. We present the Neil Gehrels Swift Observatory prompt searches for X-ray and UV/optical counterparts to the joint gravitational-wave and high-energy neutrino coincident events that happened during the third observing run of LIGO/Virgo. Swift observed the overlap between gravitational-wave and neutrino error regions for three of the considerable (<jats:italic>p</jats:italic>-value &lt; 1%) joint gravitational-wave and high-energy neutrino coincident alerts, which were generated by the IceCube Neutrino Observatory in real time after triggering by the LIGO/Virgo gravitational-wave public alerts. The searches did not associate any X-ray or UV/optical counterparts with any of the joint gravitational-wave and high-energy neutrino coincident events; however, the follow-up of these alerts significantly improved the tiling techniques covering regions between the gravitational-wave sky maps and the neutrino’s error regions, making the real-time system ready for future potential discoveries. We discuss the details of each follow-up procedure, the results of each search, and the plans for future searches.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The paper develops a theoretical relationship between the polytropic index and the temperature anisotropy that may characterize space plasmas. The derivation is based on the correlation among the kinetic energies of particles with velocities described by anisotropic kappa distributions. The correlation coefficient depends on the effective dimensionality of the velocity distribution, which is determined by the temperature anisotropy caused by the ambient magnetic field; on the other hand, the effective dimensionality is directly dependent on the polytropic index. This analysis leads to the connection between the correlation coefficient, effective dimensionality of the velocity space, and the polytropic index, with the temperature anisotropy. Moreover, a data and statistical analysis is performed to test the developed model in the solar wind proton plasma near 1 au. The derived theoretical relationship is in good agreement with observations, showing that the lowest and classical value of the adiabatic polytropic index occurs in the isotropic case, while higher values of the adiabatic index characterize more anisotropic plasmas. Finally, possible extensions of the theory considering (i) nonadiabatic polytropic behavior and (ii) more general distributions, are further discussed.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We investigate the atmospheric responses of modeled hypothetical Earth-like planets in the habitable zone of the M-dwarf AD Leonis to reduced oxygen (O<jats:sub>2</jats:sub>), removed biomass (“dead” Earth), and varying carbon dioxide (CO<jats:sub>2</jats:sub>) and surface relative humidity (sRH). Results suggest large O<jats:sub>2</jats:sub> differences between the reduced-O<jats:sub>2</jats:sub> and dead scenarios in the lower but not the upper atmosphere layers. Ozone (O<jats:sub>3</jats:sub>) and nitrous oxide (N<jats:sub>2</jats:sub>O) also show this behavior. Methane depends on hydroxyl (OH), its main sink. Abiotic production of N<jats:sub>2</jats:sub>O occurs in the upper layers. Chloromethane (CH<jats:sub>3</jats:sub>Cl) decreases everywhere on decreasing biomass. Changing CO<jats:sub>2</jats:sub> (from ×1 to ×100 present atmospheric levels (PALs)) and sRH (from 0.1% to 100%) does not influence CH<jats:sub>3</jats:sub>Cl as much as lowering biomass. Therefore, CH<jats:sub>3</jats:sub>Cl can be considered a good biosignature. Changing sRH and CO<jats:sub>2</jats:sub> has a greater influence on temperature than changing O<jats:sub>2</jats:sub> or biomass alone. Changing the biomass produces an ∼6 km effective height in transmission compared with changing CO<jats:sub>2</jats:sub> and sRH (∼25 km). In transmission O<jats:sub>2</jats:sub> is discernible at 0.76 <jats:italic>μ</jats:italic>m for &gt;0.1 PAL. The O<jats:sub>3</jats:sub> 9.6 <jats:italic>μ</jats:italic>m band is weak for the low-O<jats:sub>2</jats:sub> runs and difficult to discern from dead Earth; however O<jats:sub>3</jats:sub> at 0.3 <jats:italic>μ</jats:italic>m could serve as an indicator to distinguish between reduced-O<jats:sub>2</jats:sub> and dead Earth. The spectral features of N<jats:sub>2</jats:sub>O and CH<jats:sub>3</jats:sub>Cl correspond to effective heights of a few kilometers. CH<jats:sub>4</jats:sub> could be detectable tens of parsecs away with the Extremely Large Telescope except for the 10<jats:sup>−4</jats:sup> and 10<jats:sup>−6</jats:sup> PAL O<jats:sub>2</jats:sub> scenarios. O<jats:sub>2</jats:sub> is barely detectable for the 1 PAL O<jats:sub>2</jats:sub> case and unfeasible at lower abundances.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>HectoMAP is a dense, red-selected redshift survey to a limiting <jats:italic>r</jats:italic> = 21.3 mag covering 55 deg<jats:sup>2</jats:sup> in a contiguous 1.°5 strip across the northern sky. This region is also covered by the Subaru/Hyper Suprime-Cam (HSC) Subaru Strategic Program photometric survey enabling a range of applications that combine a dense foreground redshift survey with both strong and weak lensing maps. The median redshift of HectoMAP exceeds 0.3 throughout the survey region, and the mean density of the redshift survey is ∼2000 galaxies deg<jats:sup>−2</jats:sup>. Here we report a total of 17,313 redshifts in a first data release covering 8.7 deg<jats:sup>2</jats:sup>. We include the derived quantities <jats:italic>D</jats:italic> <jats:sub> <jats:italic>n</jats:italic> </jats:sub>4000 and stellar mass for nearly all of the objects. Among these galaxies, 8117 constitute a 79% complete red-selected subsample with <jats:italic>r</jats:italic> ≤ 20.5 mag, and an additional 4318 constitute a 68% complete red-selected subsample with 20.5 &lt; <jats:italic>r</jats:italic>(mag) &lt; 21.3. As examples of the strengths of HectoMAP data, we discuss two applications: refined membership of redMaPPer photometrically selected clusters and a test of HSC photometric redshifts. We highlight a remarkable redMaPPer strong lensing system. The comparison of photometric redshifts with spectroscopic redshifts in a dense survey uncovers subtle systematic issues in the photometric redshifts.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Extreme emission-line galaxies (EELGs) at redshift <jats:italic>z</jats:italic> = 1−2 provide a unique view of metal-poor, starburst sources that are the likely drivers of the cosmic reionization at <jats:italic>z</jats:italic> ≥ 6. However, the molecular gas reservoirs of EELGs—the fuel for their intense star formation—remain beyond the reach of current facilities. We present ALMA [C <jats:sc>ii</jats:sc>] and PdBI CO(2–1) observations of the <jats:italic>z</jats:italic> = 1.8, strongly lensed EELG SL2S 0217, a bright Ly<jats:italic>α</jats:italic> emitter with a metallicity 0.05 <jats:italic>Z</jats:italic> <jats:sub>⊙</jats:sub>. We obtain a tentative (∼3<jats:italic>σ</jats:italic>–4<jats:italic>σ</jats:italic>) detection of the [C <jats:sc>ii</jats:sc>] line and set an upper limit on the [C <jats:sc>ii</jats:sc>]/SFR (star-forming rate) ratio of ≤1 × 10<jats:sup>6</jats:sup> <jats:italic>L</jats:italic> <jats:sub>⊙</jats:sub>/(<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup>), based on the synthesized images and visibility-plane analysis. The CO(2–1) emission is not detected. Photoionization modeling indicates that up to 80% of the [C <jats:sc>ii</jats:sc>] emission originates from neutral or molecular gas, although we cannot rule out that the gas is fully ionized. The very faint [C <jats:sc>ii</jats:sc>] emission is in line with both nearby metal-poor dwarfs and high-redshift Ly<jats:italic>α</jats:italic> emitters, and predictions from hydrodynamical simulations. However, the [C <jats:sc>ii</jats:sc>] line is 30× fainter than predicted by the De Looze et al. [C <jats:sc>ii</jats:sc>]–SFR relation for local dwarfs, illustrating the danger of extrapolating locally calibrated relations to high-redshift, metal-poor galaxies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Star formation rate density, Σ<jats:sub>SFR</jats:sub>, has shown a remarkable correlation with both components of the baryonic mass kiloparsec scales (i.e., the stellar mass density and molecular gas mass density, Σ<jats:sub>*</jats:sub> and Σ<jats:sub>mol</jats:sub>, respectively) for galaxies in the nearby universe. In this study, we propose an empirical relation between Σ<jats:sub>SFR</jats:sub> and the baryonic mass surface density (Σ<jats:sub>b</jats:sub> = Σ<jats:sub>mol,Av</jats:sub> + Σ<jats:sub>*</jats:sub>, where Σ<jats:sub>mol,Av</jats:sub> is the molecular gas derived from the optical extinction, <jats:italic>A</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub>) at kiloparsec scales using the spatially resolved properties of the MaNGA survey, the largest sample of galaxies observed via integral field spectroscopy (∼8400 objects). We find that Σ<jats:sub>SFR</jats:sub> tightly correlates with Σ<jats:sub>b</jats:sub>. Furthermore, we derive an empirical relation between Σ<jats:sub>SFR</jats:sub> and a second-degree polynomial of Σ<jats:sub>b</jats:sub>, yielding a one-to-one relation between these two observables. Both Σ<jats:sub>b</jats:sub> and its polynomial form show a stronger correlation and smaller scatter with respect to Σ<jats:sub>SFR</jats:sub> than the relations derived using the individual components of Σ<jats:sub>b</jats:sub>. Our results suggest that these three parameters are indeed physically correlated, suggesting a scenario in which the two components of the baryonic mass regulate the star formation activity at kiloparsec scales.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Faraday cups can measure velocity distribution functions of space plasmas and are frequent instruments on heliophysics missions. A new version of a Faraday cup instrument is in development for the Luna 26 mission and will be used for fast monitoring of the solar wind plasma parameters. The prototype of this instrument is exposed to dust impacts in a velocity range of 0.2–60 km s<jats:sup>−1</jats:sup> using an electrostatic dust accelerator. The collected data are used to evaluate the sensitivity and detection efficiency of dust particles on two different surfaces. The results indicate that the sensitivity is sufficient for detection of the interplanetary dust as well as for the registration of the dust lifted from the lunar surface. A simple modification of the FC electronics would increase the detection efficiency by an order of magnitude.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We study the photospheric footpoints of a set of 35 coronal jets in a coronal hole as observed by Hinode/EIS. We use SDO/AIA data to coalign the spectroscopic EIS data with SDO/HMI line-of-sight magnetograms and calculate the plane-of-sky flow field using local correlation tracking (LCT) on SDO/HMI white light images. The jets are put into categories according to the changes observed in the photospheric magnetic flux at the footpoints of the coronal bright point where the jets originate: flux cancellation, complex flux changes (flux appearance/emergence and cancellation), and no flux changes. We also present three jets in detail. Observed magnetic flux evolution, LCT flow field structure and location of the jet footpoints at supergranular boundaries do not support the flux emergence scenario used in most jet simulations and are also not consistent with a rotational photospheric driver. Detailed numerical jet simulations using our observed photospheric features, in particular converging flows and flux cancellation do not currently exist, although such models would provide a realistic eruptive event scenario.</jats:p>