Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We report Hubble Space Telescope Cosmic Origins Spectrograph spectroscopy of 10 quasars with foreground star-forming galaxies at 0.02 &lt; <jats:italic>z</jats:italic> &lt; 0.14 within impact parameters of ∼1–7 kpc. We detect damped/sub-damped Ly<jats:italic>α</jats:italic> (DLA/sub-DLA) absorption in 100% of cases where no higher-redshift Lyman-limit systems extinguish the flux at the expected wavelength of Ly<jats:italic>α</jats:italic> absorption, obtaining the largest targeted sample of DLA/sub-DLAs in low-redshift galaxies. We present absorption measurements of neutral hydrogen and metals. Additionally, we present Green Bank Telescope 21 cm emission measurements for five of the galaxies (including two detections). Combining our sample with the literature, we construct a sample of 117 galaxies associated with DLA/sub-DLAs spanning 0 &lt; <jats:italic>z</jats:italic> &lt; 4.4, and examine trends between gas and stellar properties, and with redshift. The H <jats:sc>i</jats:sc> column density is anticorrelated with impact parameter and stellar mass. More massive galaxies appear to have gas-rich regions out to larger distances. The specific star formation rate (sSFR) of absorbing galaxies increases with redshift and decreases with <jats:italic>M</jats:italic>*, consistent with evolution of the star formation main sequence (SFMS). However, ∼20% of absorbing galaxies lie below the SFMS, indicating that some DLA/sub-DLAs trace galaxies with longer-than-typical gas-depletion timescales. Most DLA/sub-DLA galaxies with 21 cm emission have higher H <jats:sc>i</jats:sc> masses than typical galaxies with comparable <jats:italic>M</jats:italic>*. High <jats:italic>M</jats:italic> <jats:sub>HI</jats:sub>/<jats:italic>M</jats:italic>* ratios and high sSFRs in DLA/sub-DLA galaxies with <jats:italic>M</jats:italic>* &lt; 10<jats:sup>9</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> suggest these galaxies may be gas-rich because of recent gas accretion rather than inefficient star formation. Our study demonstrates the power of absorption and emission studies of DLA/sub-DLA galaxies for extending galactic evolution studies to previously under-explored regimes of low <jats:italic>M</jats:italic>* and low SFR.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We investigate the cold and warm gas content, kinematics, and spatial distribution of six local massive elliptical galaxies to probe the origin of the multiphase gas in their atmospheres. We report new observations, including Stratospheric Observatory for Infrared Astronomy [C <jats:sc>ii</jats:sc>], Atacama Large Millimeter/submillimeter Array CO, Multi Unit Spectroscopic Explorer (MUSE) H<jats:italic>α</jats:italic>+[N <jats:sc>ii</jats:sc>], and Very Large Array (VLA) radio observations. These are complemented by a large suite of multiwavelength archival data sets, including thermodynamical properties of the hot gas and radio jets, which are leveraged to investigate the role of active galactic nucleus (AGN) feeding/feedback in regulating the multiphase gas content. Our galactic sample shows a significant diversity in cool gas content, spanning filamentary and rotating structures. In our noncentral galaxies, the distribution of such gas is often concentrated, at variance with the more extended features observed in central galaxies. Misalignment between the multiphase gas and stars suggest that stellar mass loss is not the primary driver. A fraction of the cool gas might be acquired via galaxy interactions, but we do not find quantitative evidence of mergers in most of our systems. Instead, key evidence supports the origin via condensation out of the diffuse halo. Comparing with chaotic cold accretion (CCA) simulations, we find that our cool gas-free galaxies are likely in the overheated phase of the self-regulated AGN cycle, while for our galaxies with cool gas, the k-plot and AGN power correlation corroborate the phase of CCA feeding in which the condensation rain is triggering more vigorous AGN heating. The related C-ratio further shows that central/noncentral galaxies are expected to generate an extended/inner rain, consistent with our sample.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Upcoming ground- and space-based experiments may have sufficient accuracy to place significant constraints upon high-redshift star formation, Reionization, and dark matter (DM) using the global 21 cm signal of the intergalactic medium. In the early universe, when the relative abundance of low-mass DM halos was important, measuring the global signal would place constraints on the damping of structure formation caused by DM having a higher relic velocity (warm dark matter, or WDM) than in cold dark matter. Such damping, however, can be mimicked by altering the star formation efficiency (SFE) and can be difficult to detect because of the presence of Population III stars with unknown properties. We study these various cases and their degeneracies with the WDM mass parameter <jats:italic>m</jats:italic> <jats:sub>X</jats:sub> using a Fisher matrix analysis. We study the <jats:italic>m</jats:italic> <jats:sub>X</jats:sub> = 7 keV case and a star formation model that parameterizes the SFE as a strong function of halo mass and include several variations of this model along with three different input noise levels for the likelihood; we also use a minimum halo virial temperature for collapse near the molecular cooling threshold. We find that when the likelihood includes only Population II stars, <jats:italic>m</jats:italic> <jats:sub>X</jats:sub> is constrained to an uncertainty of ∼0.4 keV for all models and noise levels at the 68% confidence level. When the likelihood includes weak Population III stars, <jats:italic>m</jats:italic> <jats:sub>X</jats:sub> ∼ 0.3 keV, and if Population III star formation is relatively efficient, <jats:italic>m</jats:italic> <jats:sub>X</jats:sub> ∼ 0.1 keV uncertainty, with tight Population III star formation parameter constraints. Our results show that the global 21 cm signal is a promising test-bed for WDM models, even in the presence of strong degeneracies with astrophysical parameters.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present an analysis of the nebular spectra of 103 stripped-envelope (SE) supernovae (SNe) collected from the literature and observed with the Subaru Telescope from 2002 to 2012, focusing on [O <jats:sc>i</jats:sc>] <jats:italic>λλ</jats:italic>6300, 6363. The line profile and width of [O <jats:sc>i</jats:sc>] are employed to infer the ejecta geometry and the expansion velocity of the inner core; these two measurements are then compared with the SN subtypes, and further with the [O <jats:sc>i</jats:sc>]/[Ca <jats:sc>ii</jats:sc>] ratio, which is used as an indicator of the progenitor CO core mass. Based on the best-fit results of the [O <jats:sc>i</jats:sc>] profile, the objects are classified into different morphological groups, and we conclude that the deviation from spherical symmetry is a common feature for all types of SESNe. There is a hint (at the ∼1<jats:italic>σ</jats:italic> level) that the distributions of the line profile fractions are different between canonical SESNe and broad-line SNe Ic. A correlation between [O <jats:sc>i</jats:sc>] width and [O <jats:sc>i</jats:sc>]/[Ca <jats:sc>ii</jats:sc>] is discerned, indicating that the oxygen-rich material tends to expand faster for objects with a more massive CO core. Such a correlation can be utilized to constrain the relation between the progenitor mass and the kinetic energy of the explosion. Further, when [O <jats:sc>i</jats:sc>]/[Ca <jats:sc>ii</jats:sc>] increases, the fraction of objects with Gaussian [O <jats:sc>i</jats:sc>] profile increases, while those with double-peaked profile decreases. This phenomenon connects ejecta geometry and the progenitor CO core mass.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Next-generation large sky surveys will observe up to billions of galaxies for which basic structural parameters are needed to study their evolution. This is a challenging task that, for ground-based observations, is complicated by seeing-limited point-spread functions (PSFs). To perform a fast and accurate analysis of galaxy surface brightness, we have developed a family of supervised convolutional neural networks (CNNs) to derive Sérsic profile parameters of galaxies. This work presents the first two Galaxy Light profile CNNs (GaLNets) of this family. The first one is trained using galaxy images only (GaLNet-1), and the second is trained with both galaxy images and the local PSF (GaLNet-2). We have compared the results from GaLNets with structural parameters (total magnitude, effective radius, Sérsic index, etc.) derived from a set of galaxies from the Kilo-Degree Survey by 2DPHOT as a representative of the “standard” PSF-convolved Sérsic fitting tools. The comparison shows that GaLNet-2 can reach an accuracy as high as that of 2DPHOT, while GaLNet-1 performs worse because it misses the information from the local PSF. Both GaLNets are three orders of magnitude faster than standard methods in terms of computational speed. This first application of CNNs to ground-based galaxy surface photometry shows that they are promising tools to perform parametric analyses of very large galaxy samples, like the ones expected from the Vera Rubin/LSST surveys. However, GaLNets can be easily modified for space observations from Euclid and the China Space Station Telescope.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We select 52 long gamma-ray bursts (GRBs) that have precursor activity in the third Swift-BAT catalog. Each episode shown in both the precursors and the main bursts is fitted by the Norris function. We systematically analyze the temporal properties for both the precursors and the main bursts. We do not find any significant difference between the temporal profile of the precursor and that of the main burst. The photon count of the precursor is related to that of the main burst. It is indicated that the precursor and the main burst might have the same physical origin, as the precursor and the main burst follow the same <jats:italic>τ</jats:italic> <jats:sub> <jats:italic>p</jats:italic> </jats:sub>–<jats:italic>ω</jats:italic> relation. However, we do not find the explicit relation between the energy release of the precursor and the quiescent time. Some theoretical models, such as the fallback collapsar scenario and the jet-cocoon scenario, may be helpful to explain the GRB-precursor phenomena.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Numerous observational evidence has suggested the presence of active meteorology in the atmospheres of brown dwarfs. A near-infrared brightness variability has been observed. Clouds have a major role in shaping the thermal structure and spectral properties of these atmospheres. The mechanism of such variability is still unclear, and neither 1D nor global circulation models can fully study this topic due to resolution. In this study, a convective-resolving model is coupled to gray-band radiative transfer in order to study the coupling between the convective atmosphere and the variability of clouds over a large temperature range with a domain of several hundred kilometers. Six types of clouds are considered, with microphysics including settling. The clouds are radiatively active through the Rosseland mean coefficient. Radiative cloud feedback can drive spontaneous atmospheric variability in both temperature and cloud structure, as modeled for the first time in three dimensions. Silicate clouds have the most effect on the thermal structure with the generation of a secondary convective layer in some cases, depending on the assumed particle size. Iron and aluminum clouds also have a substantial impact on the atmosphere. Thermal spectra were computed, and we find the strongest effect of the clouds is the smoothing of spectral features at optical wavelengths. Compared to observed L and T dwarfs on the color–magnitude diagram, the simulated atmospheres are redder for most of the cases. Simulations with the presence of cloud holes are closer to observations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>With high-resolution narrowband He <jats:sc>i</jats:sc> 10830 Å filtergrams from Goode Solar Telescope, we give an extensive analysis for four granule-sized microeruptions which appear as the gentle ejection of material in He <jats:sc>i</jats:sc> 10830 Å band. The analysis was aided with the EUV data from Atmospheric Imaging Assembly and line-of-sight magnetograms from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. The microeruptions are situated on magnetic polarity inversion lines (PILs), and their roots are accurately traced down to intergranular lanes. Their durations are different: two microeruptions are repetitive microjets, lasting ∼50 and 27 minutes respectively, while the other two events are singular, lasting ∼5 minutes. For the two microjets, they are continuous and recurrent in the He <jats:sc>i</jats:sc> 10830 Å band, and the recurrence is quasiperiodic with a period of ∼5 minutes. We found that only transient cospatial EUV brightenings are observed for the longer duration microjets and EUV brightenings are absent for the two singular microeruptions. What is essential to the longer duration microjets is that granules with the concentration of a positive magnetic field persistently transport the magnetic field to the PILs, canceling the opposite magnetic flux and making the base of the two microjets and the underlying granules migrate with the speed of ∼0.25 and 1.0 km s<jats:sup>−1</jats:sup>. The observations support the scenario of magnetic reconnection for the quasiperiodic microjets and further show that the reconnection continuously generates multitemperature components, especially the cool component with chromospheric temperature. In addition, the ongoing reconnection is modulated by p-mode oscillations inside the Sun.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Post-starburst (PSB), or “E + A,” galaxies represent a rapid transitional phase between major, gas-rich mergers and gas-poor, quiescent, early-type galaxies. Surprisingly, many PSBs have been shown to host a significant interstellar medium (ISM), despite theoretical predictions that the majority of the star-forming gas should be expelled in active galactic nuclei– or starburst-driven outflows. To date, the resolved properties of this surviving ISM have remained unknown. We present high-resolution ALMA continuum and CO(2–1) observations in six gas- and dust-rich PSBs, revealing for the first time the spatial and kinematic structure of their ISM on sub-kpc scales. We find extremely compact molecular reservoirs, with dust and gas surface densities rivaling those found in (ultra)luminous infrared galaxies. We observe spatial and kinematic disturbances in all sources, with some also displaying disk-like kinematics. Estimates of the internal turbulent pressure in the gas exceed those of normal star-forming disks by at least 2 orders of magnitude, and rival the turbulent gas found in local interacting galaxies, such as the Antennae. Though the source of this high turbulent pressure remains uncertain, we suggest that the high incidence of tidal disruption events in PSBs could play a role. The star formation in these PSBs’ turbulent central molecular reservoirs is suppressed, forming stars only 10% as efficiently as starburst galaxies with similar gas surface densities. “The fall” of star formation in these galaxies was not precipitated by complete gas expulsion or redistribution. Rather, this high-resolution view of PSBs’ ISM indicates that star formation in their remaining compact gas reservoirs is suppressed by significant turbulent heating.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Solar coronal dimmings have been observed extensively in recent years. Due to their close association with coronal mass ejections (CMEs), there is a critical need to improve our understanding of the physical processes that cause dimmings as well as their relationship with CMEs. In this study, we investigate coronal dimmings by combining simulation and observational efforts. By utilizing a data-constrained global magnetohydrodynamics model (Alfvén-wave solar model), we simulate coronal dimmings resulting from different CME energetics and flux rope configurations. We synthesize the emissions of different EUV spectral bands/lines and compare with SDO/AIA and EVE observations. A detailed analysis of the simulation and observation data suggests that the transient dimming/brightening are related to plasma heating processes, while the long-lasting core and remote dimmings are caused by mass-loss process induced by the CME. Moreover, the interaction between the erupting flux rope with different orientations and the global solar corona could significantly influence the coronal dimming patterns. Using metrics such as dimming depth and dimming slope, we investigate the relationship between dimmings and CME properties (e.g., CME mass, CME speed) in the simulation. Our result suggests that coronal dimmings encode important information about the associated CMEs, which provides a physical basis for detecting stellar CMEs from distant solar-like stars.</jats:p>