Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Understanding the connection between nuclear activity and galaxy environment remains critical in constraining models of galaxy evolution. By exploiting the extensive cataloged data from the Galaxy and Mass Assembly survey, we identify a representative sample of 205 quasars at 0.1 &lt; <jats:italic>z</jats:italic> &lt; 0.35 and establish a comparison sample of galaxies, closely matched to the quasar sample in terms of both stellar mass and redshift. On scales &lt;1 Mpc, the galaxy number counts and group membership of quasars appear entirely consistent with those of the matched galaxy sample. Despite this, we find that quasars are ∼1.5 times more likely to be classified as the group center, indicating a potential link between quasar activity and cold gas flows or galaxy interactions associated with rich group environments. On scales of ∼a few Mpc, the clustering strengths of both samples are statistically consistent, and beyond 10 Mpc, we find no evidence that quasars trace large-scale structures any more than the galaxy control sample. Both populations are found to prefer intermediate-density sheets and filaments to either very high-density environments or very low-density environments. This weak dependence of quasar activity on galaxy environment supports a paradigm in which quasars represent a phase in the lifetime of all massive galaxies and in which secular processes and a group-centric location are the dominant triggers of quasars at low redshift.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The absolute total cross sections for the charge exchange between highly charged ions <jats:sup>15</jats:sup>N<jats:sup>7+</jats:sup>, O<jats:sup>7+</jats:sup>, and atomic H have been measured with the ion-atom merged-beams apparatus at Oak Ridge National Laboratory. The collision energy range is from 1224 down to 2 eV u<jats:sup>−1</jats:sup>, which covers outflowing hot components of astrophysical charge exchange plasmas like stellar-wind and supernova remnants. Good agreement with the previous measurements and theory is found for the collision energies above 100 eV u<jats:sup>−1</jats:sup>, while below 100 eV u<jats:sup>−1</jats:sup> limited agreement is achieved with the available calculations. These cross-section data are useful for modeling X-ray emission resulting from the charge exchange at the interface of hot plasma interacting with ambient neutral gas.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a polarimetric study of the pulsar wind nebula (PWN) in supernova remnant G21.5−0.9, using archival Very Large Array data taken at 5 and 7.4 GHz. The rotation measure (RM) map of the PWN shows a symmetric pattern that aligns with the presumed pulsar spin axis direction, implying a significant contribution to the RM from the nebula. We suggest that the spatial variation of the internal RM is mostly caused by the nonuniform distribution of electrons originating from the supernova ejecta. Our high-resolution radio polarization map reveals a global radial <jats:italic>B-</jats:italic>field. We show that a simple model with overall radial field and turbulence on a small scale can reproduce many observed features of the PWN, including the polarization pattern and polarized fraction. The modeling results also reject a strong large-scale toroidal <jats:italic>B</jats:italic>-field, suggesting that the toroidal field observed in the inner PWN cannot propagate to the entire nebula. Lastly, our model predicts that the internal Faraday rotation would break the linear relation between the polarization angle and the square of the wavelength, and cause severe depolarization at low frequencies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Primordial black holes (PBHs) from the early universe constitute attractive dark matter candidates. First detections of black hole–neutron star (BH–NS) candidate gravitational wave events by the LIGO/Virgo collaboration, GW200105 and GW200115, already prompted speculations about nonastrophysical origin. We analyze, for the first time, the total volumetric merger rates of PBH–NS binaries formed via two-body gravitational scattering, finding them to be subdominant to the astrophysical BH–NS rates. In contrast to binary black holes, a significant fraction of which can be of primordial origin, either formed in dark matter halos or in the early universe, PBH–NS rates cannot be significantly enhanced by contributions preceding star formation. Our findings imply that the identified BH–NS events are of astrophysical origin, even when PBH–PBH events significantly contribute to the gravitational wave observations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The properties of dust change during the transition from diffuse to dense clouds as a result of ice formation and dust coagulation, but much is still unclear about this transformation. We present 2–20 <jats:italic>μ</jats:italic>m spectra of 49 field stars behind the Perseus and Serpens Molecular Clouds and establish relationships between the near-infrared continuum extinction (<jats:italic>A</jats:italic> <jats:sub>K</jats:sub>) and the depths of the 9.7 <jats:italic>μ</jats:italic>m silicate (<jats:italic>τ</jats:italic> <jats:sub>9.7</jats:sub>) and 3.0 <jats:italic>μ</jats:italic>m H<jats:sub>2</jats:sub>O ice (<jats:italic>τ</jats:italic> <jats:sub>3.0</jats:sub>) absorption bands. The <jats:italic>τ</jats:italic> <jats:sub>9.7</jats:sub>/<jats:italic>A</jats:italic> <jats:sub>K</jats:sub> ratio varies from large, diffuse interstellar medium-like values (∼0.55), to much lower ratios (∼0.26). Above extinctions of <jats:italic>A</jats:italic> <jats:sub>K</jats:sub> ∼ 1.2 (<jats:italic>A</jats:italic> <jats:sub>V</jats:sub> ∼ 10; Perseus, Lupus, dense cores) and ∼2.0 (<jats:italic>A</jats:italic> <jats:sub>V</jats:sub> ∼ 17; Serpens), the <jats:italic>τ</jats:italic> <jats:sub>9.7</jats:sub>/<jats:italic>A</jats:italic> <jats:sub>K</jats:sub> ratio is lowest. The <jats:italic>τ</jats:italic> <jats:sub>9.7</jats:sub>/<jats:italic>A</jats:italic> <jats:sub>K</jats:sub> reduction from diffuse to dense clouds is consistent with a moderate degree of grain growth (sizes up to ∼0.5 <jats:italic>μ</jats:italic>m), increasing the near-infrared color excess (and thus <jats:italic>A</jats:italic> <jats:sub>K</jats:sub>), but not affecting the ice and silicate band profiles. This grain growth process seems to be related to the ice column densities and dense core formation thresholds, highlighting the importance of density. After correction for Serpens foreground extinction, the H<jats:sub>2</jats:sub>O ice formation threshold is in the range of <jats:italic>A</jats:italic> <jats:sub>K</jats:sub> = 0.31–0.40 (<jats:italic>A</jats:italic> <jats:sub>V</jats:sub> = 2.6–3.4) for all clouds, and thus grain growth takes place after the ices are formed. Finally, abundant CH<jats:sub>3</jats:sub>OH ice (∼21% relative to H<jats:sub>2</jats:sub>O) is reported for 2MASSJ18285266+0028242 (Serpens), a factor of &gt;4 larger than for the other targets.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Sparse aperture masking interferometry (SAM) is a high-resolution observing technique that allows for imaging at and beyond a telescope’s diffraction limit. The technique is ideal for searching for stellar companions at small separations from their host star; however, previous analyses of SAM observations of young stars surrounded by dusty disks have had difficulties disentangling planet and extended disk emission. We analyze VLT/SPHERE-IRDIS SAM observations of the transition disk LkCa 15, model the extended disk emission, probe for planets at small separations, and improve contrast limits for planets. We fit geometrical models directly to the interferometric observables and recover previously observed extended disk emission. We use dynamic nested sampling to estimate uncertainties on our model parameters and to calculate evidences to perform model comparison. We compare our extended disk emission models against point-source models to robustly conclude that the system is dominated by extended emission within 50 au. We report detections of two previously observed asymmetric rings at ∼17 and ∼45 au. The peak brightness location of each model ring is consistent with the previous observations. We also, for the first time with imaging, robustly recover an elliptical Gaussian inner disk, previously inferred via SED fitting. This inner disk has an FWHM of 5 au and a similar inclination and orientation to the outer rings. Finally, we recover no clear evidence for candidate planets. By modeling the extended disk emission, we are able to place a lower limit on the near-infrared companion contrast of at least 1000.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We estimate the amount of negative feedback energy injected into the interstellar medium (ISM) of the host galaxy of 3C 273, a prototypical radio-loud quasar. We obtained 93, 233, and 343 GHz continuum images with the Atacama Large Millimeter/submillimeter Array (ALMA). After self-calibration and point-source subtraction, we reach an image dynamic range of ∼85,000 at 93 GHz, ∼39,000 at 233 GHz, and ∼2500 at 343 GHz. These are currently the highest image dynamic range obtained using ALMA. We detect spatially extended millimeter emission associated with the host galaxy, cospatial with the extended emission line region (EELR) observed in the optical. The millimeter spectral energy distribution and comparison with centimeter data show that the extended emission cannot be explained by dust thermal emission or synchrotron or thermal bremsstrahlung arising from massive star formation. We interpret the extended millimeter emission as thermal bremsstrahlung from gas directly ionized by the central source. The extended flux indicates that at least ∼7% of the bolometric flux of the nuclear source was used to ionize atomic hydrogen in the host galaxy. The ionized gas is estimated to be as massive as 10<jats:sup>10</jats:sup>–10<jats:sup>11</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, but the molecular gas fraction with respect to the stellar mass is consistent with other ellipticals, suggesting that direct ionization ISM by the QSO may not be sufficient to suppress star formation, or we are witnessing a short timescale before negative feedback becomes observable. The discovery of a radio counterpart to EELRs provides a new pathway to studying the QSO–host ISM interaction.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Millilensing of gamma-ray bursts (GRBs) is expected to manifest as multiple emission episodes in a single triggered GRB with similar light-curve patterns and similar spectrum properties. Identifying such lensed GRBs could help improve constraints on the abundance of compact dark matter. Here we present a systemic search for millilensing among 3000 GRBs observed by the Fermi GBM up to 2021 April. Eventually we find four interesting candidates by performing an autocorrelation test, hardness test, and time-integrated/resolved spectrum test. GRB 081126A and GRB 090717A are ranked as the first-class candidates based on their excellent performance in both temporal and spectrum analysis. GRB 081122A and GRB 110517B are ranked as the second-class candidates (suspected candidates), mainly because their two emission episodes show clear deviations in part of the time-resolved spectrum or in the time-integrated spectrum. Considering a point-mass model for the gravitational lens, our results suggest that the density parameter of lens objects with mass <jats:italic>M</jats:italic> <jats:italic> <jats:sub>L</jats:sub> </jats:italic> ∼ 10<jats:sup>6</jats:sup> <jats:italic> M</jats:italic> <jats:sub>⊙</jats:sub> is larger than 1.5 × 10<jats:sup>−3</jats:sup>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The measurements of the bulk properties of most isolated neutron stars (INSs) are challenging tasks. Tang et al. have developed a new method, based on the equation of state (EoS) of neutron star (NS) material constrained by the observational data, to infer the gravitational masses of a few INSs whose gravitational redshifts are available. However, in that work, the authors only considered the constraints on the EoS from nuclear experiments/theories and the gravitational wave data of GW170817; the possible phase transition has not been taken into account. In this work, we adopt three EoS models (including the one incorporates a first-order strong phase transition) that are constrained by the latest multimessenger NS data, including in particular the recent mass–radius measurements of two NSs by Neutron Star Interior Composition Explorer, to update the estimation of the gravitational masses of RBS 1223, RX J0720.4-3125, and RX J1856.5-3754. In comparison to our previous approach, the new constraints are tighter, and the gravitational masses are larger by about 0.1<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. All the inferred gravitational masses are within the range of the NS masses measured in other ways. We have also calculated the radius, tidal-deformability, and moment of inertia of these sources. The inclusion of the first-order strong phase transition has little influence on modifying the results.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The nearby Type II active galactic nucleus (AGN) 1ES 1927+654 went through a violent changing-look (CL) event beginning 2017 December during which the optical and UV fluxes increased by four magnitudes over a few months, and broad emission lines newly appeared in the optical/UV. By 2018 July, the X-ray coronal emission had completely vanished, only to reappear a few months later. In this work we report the evolution of the radio, optical, UV and X-rays from the preflare state through mid-2021 with new and archival data from the Very Long Baseline Array, the European VLBI Network, the Very Large Array, the Telescopio Nazionale Galileo, Gran Telescopio Canarias, The Neil Gehrels Swift observatory, and XMM-Newton. The main results from our work are (i) the source has returned to its pre-CL state in optical, UV, and X-ray; the disk–corona relation has been reestablished as it has been in the pre-CL state, with an <jats:italic>α</jats:italic> <jats:sub>OX</jats:sub> ∼ 1.02. The optical spectra are dominated by narrow emission lines. (ii) The UV light curve follows a shallower slope of ∝ <jats:italic>t</jats:italic> <jats:sup>−0.91±0.04</jats:sup> compared to that predicted by a tidal disruption event. We conjecture that a magnetic flux inversion event is the possible cause for this enigmatic event. (iii) The compact radio emission which we tracked in the pre-CL (2014), during CL (2018), and post-CL (2021) at spatial scales &lt;1 pc was at its lowest level during the CL event in 2018, nearly contemporaneous with a low 2–10 keV emission. The radio to X-ray ratio of the compact source <jats:italic>L</jats:italic> <jats:sub>Radio</jats:sub>/<jats:italic>L</jats:italic> <jats:sub>X−ray</jats:sub> ∼ 10<jats:sup>−5.5</jats:sup> follows the Güdel–Benz relation, typically found in coronally active stars and several AGNs. (iv) We do not detect any presence of nascent jets at the spatial scales of ∼5–10 pc.</jats:p>