Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Line intensity mapping (LIM) is a promising observational method to probe large-scale fluctuations of line emission from distant galaxies. Data from wide-field LIM observations allow us to study the large-scale structure of the universe as well as galaxy populations and their evolution. A serious problem with LIM is contamination by foreground/background sources and various noise contributions. We develop conditional generative adversarial networks (cGANs) that extract designated signals and information from noisy maps. We train the cGANs using 30,000 mock observation maps with assuming a Gaussian noise matched to the expected noise level of NASA’s SPHEREx mission. The trained cGANs successfully reconstruct H<jats:italic>α</jats:italic> emission from galaxies at a target redshift from observed, noisy intensity maps. Intensity peaks with heights greater than 3.5<jats:italic>σ</jats:italic> <jats:sub>noise</jats:sub> are located with 60% precision. The one-point probability distribution and the power spectrum are accurately recovered even in the noise-dominated regime. However, the overall reconstruction performance depends on the pixel size and on the survey volume assumed for the training data. It is necessary to generate training mock data with a sufficiently large volume in order to reconstruct the intensity power spectrum at large angular scales. The suitably trained cGANs perform robustly against variations of the galaxy line emission model. Our deep-learning approach can be readily applied to observational data with line confusion and with noise.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>From a new perspective, we reexamine self-gravity and turbulence jointly, in hopes of understanding the physical basis for one of the most important empirical relations governing clouds in the interstellar medium (ISM), the Larson’s relation relating velocity dispersion (<jats:italic>σ</jats:italic> <jats:sub> <jats:italic>R</jats:italic> </jats:sub>) to cloud size (<jats:italic>R</jats:italic>). We report on two key new findings. First, the correct form of the Larson’s relation is <jats:inline-formula> <jats:tex-math> <?CDATA ${\sigma }_{R}={\alpha }_{v}^{1/5}{\sigma }_{\mathrm{pc}}{(R/1\mathrm{pc})}^{3/5}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlabcecbieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, where <jats:italic>α</jats:italic> <jats:sub> <jats:italic>v</jats:italic> </jats:sub> is the virial parameter of clouds and <jats:italic>σ</jats:italic> <jats:sub>pc</jats:sub> is the strength of the turbulence, if the turbulence has the Kolmogorov spectrum. Second, the amplitude of Larson’s relation, <jats:italic>σ</jats:italic> <jats:sub>pc</jats:sub>, is not universal, differing by a factor of about 2 between clouds on the Galactic disk and those at the Galactic center, as evidenced by observational data.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the results of a search in LIGO O2 public data for continuous gravitational waves from the neutron star in the low-mass X-ray binary Scorpius X-1. We search for signals with ≈ constant frequency in the range 40–180 Hz. Thanks to the efficiency of our search pipeline we can use a long coherence time and achieve unprecedented sensitivity, significantly improving on existing results. This is the first search that has been able to probe gravitational wave amplitudes that could balance the accretion torque at the neutron star radius. Our search excludes emission at this level between 67.5 and 131.5 Hz, for an inclination angle 44° ± 6° derived from radio observations, and assuming that the spin axis is perpendicular to the orbital plane. If the torque arm is ≈26 km—a conservative estimate of the Alfvén radius—our results are more constraining than the indirect limit across the band. This allows us to exclude certain mass–radius combinations and to place upper limits on the strength of the star’s magnetic field with a different probe than ever used before. We also correct a mistake that appears in the literature in the equation that gives the gravitational wave amplitude at the torque balance and we re-interpret the associated latest LIGO/Virgo results in light of this.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The disks of active galactic nuclei (AGNs), traditionally studied as feeders of the supermassive black holes (SMBHs) at their centers, are also hosts to massive stars and hence their neutron star (NS) and black hole (BH) remnants. Migration traps and gas torques in these disks favor binary formation and enhance the rate of compact object mergers. In these environments both long gamma-ray bursts (GRBs) from the death of massive stars and short GRBs from NS–NS to NS–BH mergers are expected. However, their properties in the environment of AGN disks have never been studied. Here we show that GRBs in AGN disks can display unique features, owing to the unusual relative position of the shocks that characterize the burst evolution and the Thomson photosphere of the AGN disk. In dense environments, for example, a relativistic reverse shock develops early, likely powering the prompt emission instead of internal shocks. The transient’s time evolution is also compressed, yielding afterglow emission that is brighter and may peak earlier than for GRBs in the interstellar medium. Additionally, in regions of the disk that are sufficiently dense and extended, the light curves are dominated by diffusion, since the fireball remains inside the disk photosphere throughout the entire evolution. These diffusion-dominated transients emerge on timescales of days in disks around SMBHs of ∼ 10<jats:sup>6</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> to years for SMBHs of ∼ 10<jats:sup>8</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. Finally, a large fraction of events, especially in AGNs with SMBHs ≲ 10<jats:sup>7</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, display time-variable absorption in the X-ray band.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Distant quasars are unique tracers to study the formation of the earliest supermassive black holes (SMBHs) and the history of cosmic reionization. Despite extensive efforts, only two quasars have been found at <jats:italic>z</jats:italic> ≥ 7.5, due to a combination of their low spatial density and the high contamination rate in quasar selection. We report the discovery of a luminous quasar at <jats:italic>z</jats:italic> = 7.642, J0313−1806, the most distant quasar yet known. This quasar has a bolometric luminosity of 3.6 × 10<jats:sup>13</jats:sup> <jats:italic>L</jats:italic> <jats:sub>⊙</jats:sub>. Deep spectroscopic observations reveal a SMBH with a mass of (1.6 ± 0.4) × 10<jats:sup>9</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> in this quasar. The existence of such a massive SMBH just ∼670 million years after the big bang challenges significantly theoretical models of SMBH growth. In addition, the quasar spectrum exhibits strong broad absorption line (BAL) features in C <jats:sc>iv</jats:sc> and Si <jats:sc>iv</jats:sc>, with a maximum velocity close to 20% of the speed of light. The relativistic BAL features, combined with a strongly blueshifted C <jats:sc>iv</jats:sc> emission line, indicate that there is a strong active galactic nucleus (AGN)-driven outflow in this system. Atacama Large Millimeter/submillimeter Array observations detect the dust continuum and [C <jats:sc>ii</jats:sc>] emission from the quasar host galaxy, yielding an accurate redshift of 7.6423 ± 0.0013 and suggesting that the quasar is hosted by an intensely star-forming galaxy, with a star formation rate of ∼200 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup> and a dust mass of ∼7 × 10<jats:sup>7</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. Follow-up observations of this reionization-era BAL quasar will provide a powerful probe of the effects of AGN feedback on the growth of the earliest massive galaxies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present new Atacama Large Millimeter/submillimeter Array observations toward a compact (∼230 au separation) triple protostar system, L1448 IRS3B, at 879 <jats:italic>μ</jats:italic>m with 011 × 005 resolution. Spiral arm structure within the circum-multiple disk is well resolved in dust continuum toward IRS3B, and we detect the known wide (∼2300 au) companion, IRS3A, also resolving possible spiral substructure. Using dense gas tracers, C<jats:sup>17</jats:sup>O (<jats:italic>J</jats:italic> = 3 <jats:inline-formula> <jats:tex-math> <?CDATA $\to $?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlabcc02ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> 2), H<jats:sup>13</jats:sup>CO<jats:sup>+</jats:sup> (<jats:italic>J</jats:italic> = 4 <jats:inline-formula> <jats:tex-math> <?CDATA $\to $?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlabcc02ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> 3), and H<jats:sup>13</jats:sup>CN (<jats:italic>J</jats:italic> = 4 <jats:inline-formula> <jats:tex-math> <?CDATA $\to $?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlabcc02ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> 3), we resolve the Keplerian rotation for both the circum-triple disk in IRS3B and the disk around IRS3A. Furthermore, we use the molecular line kinematic data and radiative transfer modeling of the molecular line emission to confirm that the disks are in Keplerian rotation with fitted masses of <jats:inline-formula> <jats:tex-math> <?CDATA ${1.19}_{-0.07}^{+0.13}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlabcc02ieqn4.gif" xlink:type="simple" /> </jats:inline-formula> <jats:italic> M</jats:italic> <jats:sub>⊙</jats:sub> for IRS3B-ab and <jats:inline-formula> <jats:tex-math> <?CDATA ${1.51}_{-0.07}^{+0.06}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlabcc02ieqn5.gif" xlink:type="simple" /> </jats:inline-formula> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> for IRS3A and place an upper limit on the central protostar mass for the tertiary IRS3B-c of 0.2 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. We measure the mass of the fragmenting disk of IRS3B to be ∼0.29 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> from the dust continuum emission of the circum-multiple disk and estimate the mass of the clump surrounding IRS3B-c to be 0.07 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. We also find that the disk around IRS3A has a mass of ∼0.04 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. By analyzing the Toomre <jats:italic>Q</jats:italic> parameter, we find the IRS3A circumstellar disk is gravitationally stable (<jats:italic>Q</jats:italic> &gt; 5), while the IRS3B disk is consistent with a gravitationally unstable disk (<jats:italic>Q</jats:italic> &lt; 1) between the radii ∼200–500 au. This coincides with the location of the spiral arms and the tertiary companion IRS3B-c, supporting the hypothesis that IRS3B-c was formed in situ via fragmentation of a gravitationally unstable disk.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The galactic diffuse <jats:italic>γ</jats:italic>-ray emission, as seen by Fermi Large Area Telescope (LAT), shows a sharp peak in the region around 4 kpc from the Galactic center, which can be interpreted either as due to an enhanced density of cosmic-ray accelerators or to a modification of the particle diffusion in that region. Observations of <jats:italic>γ</jats:italic>-rays originating in molecular clouds are a unique tool to infer the cosmic-ray density point by point, in distant regions of the Galaxy. We report here the analysis of 11 yr Fermi-LAT data, obtained in the direction of nine molecular clouds located in the 1.5–4.5 kpc region. The cosmic-ray density measured at the locations of these clouds is compatible with the locally measured one. We demonstrate that the cosmic-ray density gradient inferred from the diffuse gamma-ray emission is the result of the presence of cosmic-ray accelerators rather than a global change of the sea of Galactic cosmic rays due to their propagation.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present high-resolution optical images from the Hubble Space Telescope, X-ray images from the Chandra X-ray Observatory, and optical spectra from the Nordic Optical Telescope for a newly discovered galaxy cluster, CHIPS1911+4455, at <jats:italic>z</jats:italic> = 0.485 ± 0.005. CHIPS1911+4455 was discovered in the Clusters Hiding in Plain Sight survey, which sought to discover galaxy clusters with extreme central galaxies that were misidentified as isolated X-ray point sources in the ROSAT All-Sky Survey. With new Chandra X-ray observations, we find the core (<jats:italic>r</jats:italic> = 10 kpc) entropy to be <jats:inline-formula> <jats:tex-math> <?CDATA ${17}_{-9}^{+2}\,\mathrm{keV}\,{\mathrm{cm}}^{2}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlabd540ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, suggesting a strong cool core, which is typically found at the centers of relaxed clusters. However, the large-scale morphology of CHIPS1911+4455 is highly asymmetric, pointing to a more dynamically active and turbulent cluster. Furthermore, the Hubble images reveal a massive, filamentary starburst near the brightest cluster galaxy (BCG). We measure the star formation rate for the BCG to be 140–190 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup>, which is one of the highest rates measured in a central cluster galaxy to date. One possible scenario for CHIPS1911+4455 is that the cool core was displaced during a major merger and rapidly cooled, with cool, star-forming gas raining back toward the core. This unique system is an excellent case study for high-redshift clusters, where such phenomena are proving to be more common. Further studies of such systems will drastically improve our understanding of the relation between cluster mergers and cooling, and how these fit in the bigger picture of active galactic nuclei feedback.</jats:p>