Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We present Gemini Multi-Object Spectrograph (GMOS) integral field unit (IFU) observations of six massive (<jats:italic>M</jats:italic> <jats:sub>⋆</jats:sub> ≥ 10<jats:sup>11</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) A-star dominated post-starburst galaxies at <jats:italic>z</jats:italic> ∼ 0.6. These galaxies are a subsample of the <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{SQuIGG}\vec{L}{\rm{E}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabc265ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> Survey, which selects intermediate-redshift post-starbursts from the Sloan Digital Sky Survey spectroscopic sample (DR14) with spectral shapes that indicate they have recently shut off their primary epoch of star formation. Using <jats:italic>Hδ</jats:italic> <jats:sub> <jats:italic>A</jats:italic> </jats:sub> absorption as a proxy for stellar age, we constrain five of the galaxies to have young (∼600 Myr) light-weighted ages at all radii and find that the sample on average has flat age gradients. We examine the spatial distribution of mass-weighted properties by fitting our profiles with a toy model including a young, centrally concentrated burst superimposed on an older, extended population. We find that galaxies with flat <jats:italic>Hδ</jats:italic> <jats:sub> <jats:italic>A</jats:italic> </jats:sub> profiles are inconsistent with formation via a central secondary starburst. This implies that the mechanism responsible for shutting off this dominant episode of star formation must have done so uniformly throughout the galaxy.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The sputtering rate of presolar silicon carbide grains due to galactic cosmic rays has been computed for their experimentally deduced lifetimes (∼1 Gyr) in the interstellar medium. An ion target simulator, SDTrimSP, was used to model the sputtering of interstellar grains with varying sizes and thicknesses of the ice mantle formed around the grain during their journey through the interstellar medium. Temperature, composition, and density for four different types of molecular cloud environments (quiescent, low-mass young stellar objects (YSOs), intermediate-mass YSOs, and high-mass YSO weak processing) considered indicate the sputtering rate on the mantle ice composition depends on water composition to a certain extent. The model simulations indicate galactic cosmic ray(s) with an energy range from 10 MeV to 1 GeV are just capable of sputtering/destructing ∼13%–15% of the grain itself. This value, stretched over 1 Gyr is not as significant as the other destruction processes and therefore can be classified as a minor destruction process. The effect of galactic cosmic rays on the ice mantle and core is also noted with particular emphasis on amorphization/recoils generated inside the SiC core and their distribution within the grain.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We study the characteristics of near-Earth networks (NENs) of gamma-ray burst (GRB) detectors, with the objective of defining a network with all-sky, full-time localization capability for multimessenger astrophysics. We show that a minimum network consisting of nine identical spacecraft in two orbits with different inclinations provides a good combination of sky coverage with several-degree localization accuracy with detector areas of 100 cm<jats:sup>2</jats:sup>. In order to achieve this, careful attention must be paid to systematics. This includes accurate photon timing (∼0.1 ms), good energy resolution (∼10%), and reduction of Earth albedo, which are all within current capabilities. Such a network can be scaled in both the number and size of detectors to produce increased accuracy. We introduce a new method of localization that does not rely on on-board trigger systems or on the cross-correlation of time histories, but rather it tests positions in ground processing over the entire sky and assigns probabilities to them to detect and localize events. We demonstrate its capabilities with simulations. If the NEN spacecraft can downlink at least several hundred time- and energy-tagged events per second, and the data can be ground-processed as they are received, it can in principle derive GRB positions in near-real time over the entire sky.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We conducted 22 GHz 1″ Jansky Very Large Array imaging of 100 radio-quiet X-ray-selected active galactic nuclei (AGN) from the Swift–Burst Array Telescope (Swift–BAT) survey. We find AGN-driven kiloparsec-scale radio structures inconsistent with pure star formation in 11 AGN. The host galaxies of these AGN lie significantly below the star-forming main sequence, indicating suppressed star formation. While these radio structures tend to be physically small compared to the host galaxy, the global star formation rate of the host is affected. We evaluate the energetics of the radio structures interpreted first as immature radio jets, and then as consequences of an AGN-driven radiative outflow, and compare them to two criteria for successful feedback: the ability to remove the CO-derived molecular gas mass from the galaxy gravitational potential and the kinetic energy transfer to molecular clouds leading to <jats:italic>v</jats:italic> <jats:sub>cloud</jats:sub> &gt; <jats:italic>σ</jats:italic> <jats:sub>*</jats:sub>. In most cases, the jet interpretation is insufficient to provide the energy necessary to cause the star formation suppression. Conversely, the wind interpretation provides ample energy in all but one case. We conclude that it is more likely that the observed suppression of star formation in the global host galaxy is due to interstellar medium interactions of a radiative outflow, rather than a small-scale radio jet.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Isolated dense molecular cores are investigated to study the onset of complex organic molecule formation in interstellar ice. Sampling three cores with ongoing formation of low-mass stars (B59, B335, and L483) and one starless core (L694-2), we sample lines of sight to nine background stars and five young stellar objects (YSOs; <jats:italic>A</jats:italic> <jats:sub> <jats:italic>K</jats:italic> </jats:sub>  ∼ 0.5–4.7). Spectra of these stars from 2 to 5 <jats:italic>μ</jats:italic>m with NASA’s Infrared Telescope Facility (IRTF) simultaneously display signatures from the cores of H<jats:sub>2</jats:sub>O (3.0 <jats:italic>μ</jats:italic>m), CH<jats:sub>3</jats:sub>OH (C–H stretching mode, 3.53 <jats:italic>μ</jats:italic>m), and CO (4.67 <jats:italic>μ</jats:italic>m) ices. The CO ice is traced by nine stars, in which five show a long-wavelength wing due to a mixture of CO with polar ice (CO<jats:sub> <jats:italic>r</jats:italic> </jats:sub>), presumably CH<jats:sub>3</jats:sub>OH. Two of these sightlines also show independent detections of CH<jats:sub>3</jats:sub>OH. For these we find the ratio of the CH<jats:sub>3</jats:sub>OH:CO<jats:sub> <jats:italic>r</jats:italic> </jats:sub> is 0.55 ± 0.06 and 0.73 ± 0.07 from L483 and L694-2, respectively. The detections of both CO and CH<jats:sub>3</jats:sub>OH for the first time through lines of sight toward background stars observationally constrains the conversion of CO into CH<jats:sub>3</jats:sub>OH ice. Along the lines of sight, most of the CO exists in the gas phase and ≤15% of the CO is frozen out. However, CH<jats:sub>3</jats:sub>OH ice is abundant with respect to CO (∼50%) and exists mainly as a CH<jats:sub>3</jats:sub>OH-rich CO ice layer. Only a small fraction of the lines of sight contains CH<jats:sub>3</jats:sub>OH ice, presumably those with the highest density. The high conversion of CO to CH<jats:sub>3</jats:sub>OH can explain the abundances of CH<jats:sub>3</jats:sub>OH ice found in later stage Class 1 low-mass YSO envelopes (CH<jats:sub>3</jats:sub>OH:CO<jats:sub> <jats:italic>r</jats:italic> </jats:sub> ∼  0.5–0.6). For high-mass YSOs and one Class 0 YSO, this ratio varies significantly, implying local variations can affect ice formation. The large CH<jats:sub>3</jats:sub>OH ice abundance indicates that the formation of complex organic molecules is likely during the prestellar phase in cold environments without higher energy particle interactions (e.g., cosmic rays).</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Three-wave interactions between Langmuir and electromagnetic waves in plasma with unstable electron flows are believed to be the main cause of type II and III solar radio emissions. The narrow band of type II bursts requires assuming that this radiation is generated in some local regions of shock fronts traveling in the solar corona, where the specific conditions for the enhancement of electromagnetic emissions near the plasma frequency harmonics are created. The reason for such enhancement at the second harmonic may be the formation of counterstreaming electron beams. There are different opinions in the literature on whether the second harmonic electromagnetic emission in the presence of an additional beam can be efficient enough to markedly dominate emissions produced by a single beam. In the present paper, we carry out particle-in-cell simulations of the collision of two symmetric electron beams in plasma with open boundary conditions and show that the efficiency of beam-to-radiation power conversion can be significantly increased compared to models with periodic boundary conditions and reach the level of a few percent if three-wave interactions with electromagnetic waves near the second harmonic of the plasma frequency becomes available for the most unstable, oblique, beam-driven modes.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Black widow and redback systems are compact binaries in which a millisecond pulsar heats and may even ablate its low-mass companion by its intense wind of relativistic particles and radiation. In such systems, an intrabinary shock can form as a site of particle acceleration and associated nonthermal emission. We model the X-ray and gamma-ray synchrotron and inverse Compton spectral components for select spider binaries, including diffusion, convection, and radiative energy losses in an axially symmetric, steady-state approach. Our new multizone code simultaneously yields energy-dependent light curves and orbital-phase-resolved spectra. Using parameter studies and matching the observed X-ray spectra and light curves, as well as Fermi Large Area Telescope spectra where available, with a synchrotron component, we can constrain certain model parameters. For PSR J1723–2837 these are notably the magnetic field and bulk flow speed of plasma moving along the shock tangent, the shock acceleration efficiency, and the multiplicity and spectrum of pairs accelerated by the pulsar. This affords a more robust prediction of the expected high-energy and very high energy gamma-ray flux. We find that nearby pulsars with hot or flaring companions may be promising targets for the future Cerenkov Telescope Array. Moreover, many spiders are likely to be of significant interest to future MeV-band missions such as AMEGO and e-ASTROGAM.</jats:p>