Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Subarcsecond imaging of the X-ray emission in the type 2 active galactic nucleus (AGN) Mrk 78 with Chandra shows complex structure with spectral variations on scales from ∼200 pc to ∼2 kpc. Overall the X-ray emission is aligned E–W with the radio (3.6 cm) and narrow emission line region as mapped in [O <jats:sc>iii</jats:sc>], with a marked E–W asymmetry. The eastern X-ray emission is mostly in a compact knot coincident with the location where the radio source is deflected, while the western X-ray emission forms a loop or shell ∼2 kpc from the nucleus with radius ∼0.7 kpc. There is suggestive evidence of shocks in both the eastern knot and the western arc. Both these positions coincide with large changes in the velocities of the [O <jats:sc>iii</jats:sc>] outflow. We discuss possible reasons why the X-ray shocks on the western side occur ∼1 kpc farther out than on the eastern side. We estimate that the thermal energy injected by the shocks into the interstellar medium corresponds to 0.05%–0.6% of the AGN bolometric luminosity.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present <jats:sc>starduster</jats:sc>, a supervised deep-learning model that predicts the multiwavelength spectral energy distribution (SED) from galaxy geometry parameters and star formation history by emulating dust radiative transfer simulations. The model is composed of three specifically designed neural networks, which take into account the features of dust attenuation and emission. We utilize the <jats:sc>skirt</jats:sc> radiative transfer simulation to produce data for the training data of neural networks. Each neural network can be trained using ∼4000–5000 samples. Compared with the direct results of the <jats:sc>skirt</jats:sc> simulation, our deep-learning model produces ∼0.005 mag and ∼0.1–0.2 mag errors for dust attenuation and emission, respectively. As an application, we fit our model to the observed SEDs of IC 4225 and NGC 5166. Our model can reproduce the observations and provide reasonable measurements of the inclination angle and stellar mass. However, some predicted geometry parameters are different from an image-fitting study. Our analysis implies that including a constraint at (rest-frame) ∼40 <jats:italic>μ</jats:italic>m could alleviate the degeneracy in the parameter space for both IC 4225 and NGC 5166, leading to broadly consistent results with the image-fitting predictions. Our SED code is publicly available and can be applied to both SED fitting and SED modeling of galaxies from semianalytic models.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The process of migration into resonance capture has been well studied for planetary systems where the gravitational potential is generated exclusively by the star and planets. However, massive protoplanetary disks add a significant perturbation to these models. In this paper we consider two limiting cases of disk-induced precession on migrating planets and find that small amounts of precession significantly affect the equilibrium reached by migrating planets. We investigate these effects with a combination of semianalytic models of the resonance and numerical integrations. We also consider the case of the disk’s dispersal, which can excite significant libration amplitude and can cause ejection from resonance for large enough precession rates. Both of these effects have implications for interpreting the known exoplanet population and may prove to be important considerations as the population of well-characterized exoplanet systems continues to grow.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Theoretically, misalignment between the magnetic field and rotational axis in a dense core is considered to be dynamically important in the star formation process; however, the extent of this influence remains observationally unclear. For a sample of 32 Class 0 and I protostars in the Perseus Molecular Cloud, we analyzed gas motions using C<jats:sup>18</jats:sup>O data from the SMA MASSES survey and the magnetic field structures using 850 <jats:italic>μ</jats:italic>m polarimetric data from the JCMT BISTRO-1 survey and archive. We do not find any significant correlation between the velocity gradients in the C<jats:sup>18</jats:sup>O emission in the protostellar envelopes at a 1000 au scale and the misalignment between the outflows and magnetic field orientations in the dense cores at a 4000 au scale, and there is also no correlation between the velocity gradients and the angular dispersions of the magnetic fields. However, a significant dependence on the misalignment angles emerges after we normalize the rotational motion by the infalling motion, where the ratios increase from ≲1 to ≳1 with increasing misalignment angle. This suggests that the misalignment could prompt angular momentum transportation to the envelope scale but is not a dominant factor in determining the envelope rotation, and other parameters, such as mass accretion in protostellar sources, also play an important role. These results remain valid after taking into account projection effects. The comparison between our estimated angular momentum in the protostellar envelopes and the sizes of the known protostellar disks suggests that significant angular momentum is likely lost between radii of ∼1000 and 100 au in protostellar envelopes.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the long-term spectro-temporal evolution of the average radio emission properties of the magnetar XTE J1810−197 (PSR J1809−1943), following its most recent outburst in late 2018. We report the results from a 2.5 yr monitoring campaign with the upgraded Giant Metrewave Radio Telescope, carried out over the frequency range of 300–1450 MHz. Our observations show intriguing time variability in the average profile width, flux density, spectral index, and broadband spectral shape. While the average profile width appears to gradually decrease at later epochs, the flux density shows multiple episodes of radio rebrightening over the course of our monitoring. Our systematic monitoring observations reveal that the radio spectrum has steepened over time, resulting in evolution from a magnetar-like spectrum to a more pulsar-like spectrum. A more detailed analysis reveals that the radio spectrum has a turnover, and that this turnover shifts toward lower frequencies with time. We present the details of our analysis leading to these results, and discuss our findings in the context of magnetar radio emission mechanisms, as well as potential manifestations of the intervening medium. We also briefly discuss whether an evolving spectral turnover could be a ubiquitous property of radio magnetars.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>When ice on the surface of dust grains in protoplanetary disk sublimates, it adds its latent heat of water sublimation to the surrounding flow. Drawing on the analogy provided by tropical cyclones on Earth, we investigate whether this energy source is sufficient to sustain or magnify anticyclonic disk vortices that would otherwise fall victim to viscous dissipation. An analytical treatment, supported by exploratory two-dimensional simulations, suggests that even modestly undersaturated flows can extend the lifetime of vortices, potentially to a degree sufficient to aid particle trapping and planetesimal formation. We expect the best conditions for this mechanism to occur will be found near the disk’s water ice line if turbulent motions displace gas parcels out of thermodynamic equilibrium with the dust midplane.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report the localization of the X-ray emission from two strongly lensed AGN, CLASS B0712+472 (<jats:italic>z</jats:italic> = 1.34) and CLASS B1608+656 (<jats:italic>z</jats:italic> = 1.394). We obtain milliarcsecond X-ray astrometry by developing a novel method that combines parametric lens modeling with a Bayesian analysis. We spatially locate the X-ray sources in CLASS B0712+472 and CLASS B1608+656 within 11 mas and 9 mas from the radio source, respectively. For CLASS B0712+472, we find that the X-ray emission is cospatial with the radio and optical emission. On the other hand, for CLASS B1608+656, the X-ray emission is cospatial with radio but displaced with respect to the optical emission at the 1<jats:italic>σ</jats:italic> level, which positions this source as an offset AGN candidate. This high astrometric precision improves on the limitations of existing X-ray instruments by two orders of magnitude. The demonstrated method opens a path to search for offset and binary AGN at <jats:italic>z</jats:italic> &gt; 1, and to directly test supermassive black hole formation models in a redshift range that has been mostly underconstrained to date.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We investigate whether the considerable diversity in the satellite populations of nearby Milky Way (MW)-mass galaxies is connected with the diversity in their host’s merger histories. Analyzing eight nearby galaxies with extensive observations of their satellite populations and stellar halos, we characterize each galaxy’s merger history using the metric of its most dominant merger, <jats:italic>M</jats:italic> <jats:sub>⋆,Dom</jats:sub>, defined as the greater of either its total accreted stellar mass or most massive current satellite. We find an unexpectedly tight relationship between these galaxies’ number of <jats:italic>M</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub> &lt; − 9 satellites within 150 kpc (<jats:italic>N</jats:italic> <jats:sub>Sat</jats:sub>) and <jats:italic>M</jats:italic> <jats:sub>⋆,Dom</jats:sub>. This relationship remains even after accounting for differences in galaxy mass. Using the star formation and orbital histories of satellites around the MW and M81, we demonstrate that both likely evolved along the <jats:italic>M</jats:italic> <jats:sub>⋆,Dom</jats:sub>–<jats:italic>N</jats:italic> <jats:sub>Sat</jats:sub> relation during their current dominant mergers with the Large Magellanic Cloud and M82, respectively. We investigate the presence of this relation in galaxy formation models, including using the Feedback In Realistic Environments (FIRE) simulations to directly compare to the observations. We find no relation between <jats:italic>M</jats:italic> <jats:sub>⋆,Dom</jats:sub> and <jats:italic>N</jats:italic> <jats:sub>Sat</jats:sub> in FIRE, and a universally large scatter in <jats:italic>N</jats:italic> <jats:sub>Sat</jats:sub> with <jats:italic>M</jats:italic> <jats:sub>⋆,Dom</jats:sub> across simulations—in direct contrast with the tightness of the empirical relation. This acute difference in the observed and predicted scaling relation between two fundamental galaxy properties signals that current simulations do not sufficiently reproduce diverse merger histories and their effects on satellite populations. Explaining the emergence of this relation is therefore essential for obtaining a complete understanding of galaxy formation.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>While it is generally believed that supermassive black holes (SMBHs) lie in most galaxies with bulges, few SMBHs have been confirmed in bulgeless galaxies. Identifying such a population could provide important insights to the BH seed population and secular BH growth. To this end, we obtained near-infrared (NIR) spectroscopic observations of a sample of low-redshift bulgeless galaxies with mid-infrared colors suggestive of active galactic nuclei (AGNs). We find additional evidence of AGN activity (such as coronal lines and broad permitted lines) in 69% (9/13) of the sample, demonstrating that mid-infrared selection is a powerful tool to detect AGNs. More than half of the galaxies with confirmed AGN activity show fast outflows in [O <jats:sc>iii</jats:sc>] in the optical and/or [Si <jats:sc>vi</jats:sc>] in the NIR, with the latter generally having much faster velocities that are also correlated to their spatial extent. We are also able to obtain virial BH masses for some targets and find they fall within the scatter of other late-type galaxies in the <jats:italic>M</jats:italic> <jats:sub>BH</jats:sub>–<jats:italic>M</jats:italic> <jats:sub>stellar</jats:sub> relation. The fact that they lack a significant bulge component indicates that secular processes, likely independent of major mergers, grew these BHs to supermassive sizes. Finally, we analyze the rotational gas kinematics and find two notable exceptions: two AGN hosts with outflows that appear to be rotating faster than expected. There is an indication that these two galaxies have stellar masses significantly lower than expected from their dark matter halo masses. This, combined with the observed AGN activity and strong gas outflows, may be evidence of the effects of AGN feedback.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a data-driven method based on long short-term memory (LSTM) neural networks to analyze spectral time series of Type Ia supernovae (SNe Ia). The data set includes 3091 spectra from 361 individual SNe Ia. The method allows for accurate reconstruction of the spectral sequence of an SN Ia based on a single observed spectrum around maximum light. The precision of the spectral reconstruction increases with more spectral time coverages, but the significant benefit of multiple epoch data at around optical maximum is only evident for observations separated by more than a week. The method shows great power in extracting the spectral information of SNe Ia and suggests that the most critical information of an SN Ia can be derived from a single spectrum around the optical maximum. The algorithm we have developed is important for the planning of spectroscopic follow-up observations of future SN surveys with the LSST/Rubin and WFIRST/Roman telescopes.</jats:p>