Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>The search for new global scaling relations linking the physical properties of galaxies has a fundamental interest. Furthermore, their recovery from spatially resolved relations has been in the spotlight of integral field spectroscopy (IFS). In this study, we investigate the existence of global and local relations between stellar age (Age<jats:sub>⋆</jats:sub>) and gas-phase metallicity (<jats:italic>Z</jats:italic> <jats:sub> <jats:italic>g</jats:italic> </jats:sub>). To this aim, we analyze IFS data for a sample of 736 star-forming disk galaxies from the MaNGA survey. We report a positive correlation between the global <jats:italic>Z</jats:italic> <jats:sub> <jats:italic>g</jats:italic> </jats:sub> and <jats:italic>D</jats:italic>(4000) (an indicator of stellar age), with a slope that decreases with increasing galaxy mass. Locally, a similar trend is found when analyzing the <jats:italic>Z</jats:italic> <jats:sub> <jats:italic>g</jats:italic> </jats:sub> and <jats:italic>D</jats:italic>(4000) of the star-forming regions, as well as the residuals resulting from removing the radial gradients of both parameters. The local laws have systematically smaller slopes than the global one. We ascribe this difference to random errors that cause the true slope of the Age<jats:sub>⋆</jats:sub>–<jats:italic>Z</jats:italic> <jats:sub> <jats:italic>g</jats:italic> </jats:sub> relation to be systematically underestimated when performing a least-squares fitting. The explored relation is intimately linked with the already known relation between gas metallicity and star formation rate at fixed mass, both presenting a common physical origin.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The chemical homogeneity of surviving stellar clusters contains important clues about interstellar medium (ISM) mixing efficiency, star formation, and the enrichment history of the Galaxy. Existing measurements in a handful of open clusters suggest homogeneity in several elements at the 0.03 dex level. Here we present (i) a new cluster member catalog based only on APOGEE radial velocities and Gaia-DR2 proper motions, (ii) improved abundance uncertainties for APOGEE cluster members, and (iii) the dependence of cluster homogeneity on Galactic and cluster properties, using abundances of eight elements from the APOGEE survey for 10 high-quality clusters. We find that cluster homogeneity is uncorrelated with Galactocentric distance, <jats:inline-formula> <jats:tex-math> <?CDATA $| Z| $?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabb93eieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, age, and metallicity. However, velocity dispersion, which is a proxy for cluster mass, is positively correlated with intrinsic scatter at relatively high levels of significance for [Ca/Fe] and [Mg/Fe]. We also see a possible positive correlation at a low level of significance for [Ni/Fe], [Si/Fe], [Al/Fe], and [Fe/H], while [Cr/Fe] and [Mn/Fe] are uncorrelated. The elements that show a correlation with velocity dispersion are those that are predominantly produced by core-collapse supernovae (CCSNe). However, the small sample size and relatively low correlation significance highlight the need for follow-up studies. If borne out by future studies, these findings would suggest a quantitative difference between the correlation lengths of elements produced predominantly by Type Ia SNe versus CCSNe, which would have implications for Galactic chemical evolution models and the feasibility of chemical tagging.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>It is well established that a gas density gradient inside molecular clouds and clumps raises their star formation rate (SFR) compared with what they would experience from a gas reservoir of uniform density. This effect should be observed in the relation between dense-gas mass <jats:italic>M</jats:italic> <jats:sub> <jats:italic>dg</jats:italic> </jats:sub> and SFR of molecular clouds and clumps, with steeper gas density gradients yielding higher SFR/<jats:italic>M</jats:italic> <jats:sub> <jats:italic>dg</jats:italic> </jats:sub> ratios. The content of this paper is twofold. First, we build on the notion of a magnification factor introduced by Parmentier to redefine the dense-gas relation (i.e., the relation between <jats:italic>M</jats:italic> <jats:sub> <jats:italic>dg</jats:italic> </jats:sub> and SFR). Not only does the SFR/<jats:italic>M</jats:italic> <jats:sub> <jats:italic>dg</jats:italic> </jats:sub> ratio depend on the mean freefall time of the gas and on its (intrinsic) star formation efficiency per freefall time, but it also depends on the clump density profile (e.g., the logarithmic slope <jats:inline-formula> <jats:tex-math> <?CDATA $-p$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabb8d3ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> of the gas density profile and on the relative extent of the constant-density region at the clump center). Second, we show that nearby molecular clouds follow the newly defined dense-gas relation, provided that their dense-gas mass is defined based on a volume density criterion. We also find the same trend for the dense molecular clouds of the Central Molecular Zone (CMZ) of the Galaxy, although this one is scaled down by a factor of 10 compared with nearby clouds, even when including the Sgr C and Sgr B2 clouds. The respective locii of both nearby and CMZ clouds in the <jats:inline-formula> <jats:tex-math> <?CDATA $(p,{SFR}/{M}_{{dg}})$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabb8d3ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> parameter space is discussed.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report the detection of extended X-ray emission from two high-redshift radio quasars. These quasars, J1405+0415 at <jats:italic>z</jats:italic> = 3.208 and J1610+1811 at <jats:italic>z</jats:italic> = 3.118, were observed in a Chandra snapshot survey selected from a complete sample of the radio-brightest quasars in the overlap area of the VLA-FIRST radio survey and the Sloan Digital Sky Survey. The extended X-ray emission is located along the line connecting the core to a radio knot or hotspot, favoring the interpretation of X-ray jets. The inferred rest-frame jet X-ray luminosities from 2 to 30 keV would be of order 10<jats:sup>45</jats:sup> erg s<jats:sup>−1</jats:sup> if emitted isotropically and without relativistic beaming. In the scenario of inverse Compton scattering of the cosmic microwave background (CMB), X-ray jets without a coincident radio counterpart may be common, and should be readily detectable to redshifts even beyond 3.2 due to the (1+<jats:italic>z</jats:italic>)<jats:sup>4</jats:sup> increase of the CMB energy density compensating for the (1+<jats:italic>z</jats:italic>)<jats:sup>−4</jats:sup> cosmological diminution of surface brightness. If these can be X-ray confirmed, they would be the second and third examples of quasar X-ray jets without detection of underlying continuous radio jets.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this paper we present our studies on the stellar populations and star formation histories (SFHs) for the Reines et al. sample of 136 dwarf galaxies that host active galactic nuclei (AGNs), selected from the Sloan Digital Sky Survey Data Release 8. We derive stellar populations and reconstruct SFHs for these AGN-host dwarfs using the stellar population synthesis code STARLIGHT. Our results suggest that these AGN-host dwarfs have assembled their stellar masses within a narrow period of time with the stellar mass-weighted ages in the range of 10<jats:sup>9</jats:sup>–10<jats:sup>10</jats:sup> yr, but show a wide diversity of SFHs with the luminosity-weighted stellar ages in the range of 10<jats:sup>7</jats:sup>–10<jats:sup>10</jats:sup> yr. The old population (<jats:italic>t</jats:italic> &gt; 10<jats:sup>9</jats:sup> yr) contributes most to the galaxy light for the majority of the sample; the young population (<jats:italic>t</jats:italic> &lt; 10<jats:sup>8</jats:sup> yr) also appears in significant but widely varying fractions, while the intermediate-age population (10<jats:sup>8</jats:sup> &lt; <jats:italic>t</jats:italic> &lt; 10<jats:sup>9</jats:sup> yr) in general contributes less to the optical continuum at 4020 Å. We also find that these dwarfs follow a similar mass–metallicity relation to normal star-forming galaxies, indicating that AGNs have little effect on the chemical evolution of the host galaxy. We further investigate the relation between the derived SFHs and morphology of the host galaxy, and find no correlation. Comparing the SFHs with the luminosity of the [O <jats:sc>iii</jats:sc>] <jats:italic>λ</jats:italic>5007 line (<jats:inline-formula> <jats:tex-math> <?CDATA ${L}_{[{\rm{O}}{\rm\small{III}}]}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabb81cieqn1.gif" xlink:type="simple" /> </jats:inline-formula>), we find a mild correlation exists when <jats:inline-formula> <jats:tex-math> <?CDATA ${L}_{[{\rm{O}}{\rm\small{III}}]}\gt {10}^{39}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabb81cieqn2.gif" xlink:type="simple" /> </jats:inline-formula> erg s<jats:sup>−1</jats:sup>, indicating a physical connection between star formation and AGN activities in these dwarf galaxies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We study the impact of supernovae on individual molecular clouds, using a high-resolution magnetohydrodynamic simulation of a 250 pc region where we resolve the formation of individual massive stars. The supernova feedback is implemented with real supernovae, meaning supernovae that are the natural evolution of the resolved massive stars, so their position and timing are self-consistent. We select a large sample of molecular clouds from the simulation to investigate the supernova energy injection and the resulting properties of molecular clouds. We find that molecular clouds have a lifetime of a few dynamical times, less than half of them contract to the point of becoming gravitationally bound, and the dispersal time of bound clouds of order one dynamical time is a factor of 2 shorter than that of unbound clouds. We stress the importance of internal supernovae, that is, massive stars that explode inside their parent cloud, in setting the cloud dispersal time, and their huge overdensity compared to models where the supernovae are randomly distributed. We also quantify the energy injection efficiency of supernovae as a function of supernova distance to the clouds. We conclude that intermittent driving by supernovae can maintain molecular cloud turbulence and may be the main process for cloud dispersal and that the full role of supernovae in the evolution of molecular clouds cannot be fully accounted for without a self-consistent implementation of the supernova feedback.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We analyze the energy distributions of final (stable) products—gamma rays, neutrinos, and electrons—produced in inelastic proton–proton collisions in the PeV energy regime. We also calculate the energy spectrum of synchrotron radiation from secondary electrons, assuming that these are promptly cooled in the surrounding magnetic field. We show that the synchrotron radiation has an energy distribution much shallower than that of primary protons, hence we suggest taking advantage of such a feature in the spectral analysis of the highest-energy (cutoff) emission region from particle accelerators. For a broad range of energy distributions in the parent protons, we propose simple analytical presentations for the spectra of secondaries in the cutoff region. These results can be used in the interpretation of high-energy radiation from PeVatrons—cosmic-ray factories accelerating protons to energies up to 1 PeV.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Long-lasting activity complexes (ACs), characterized as a series of closely located, continuously emerging solar active regions (ARs), are considered generating prominent poleward surges from observations. The surges lead to significant variations of the polar field, which are important for the modulation of solar cycles. We aim to study a prominent poleward surge during solar cycle 24 on the southern hemisphere, and analyze its originating ACs and the effect on the polar field evolution. We automatically identify and characterize ARs based on synoptic magnetograms from the Solar Dynamics Observatory. We assimilate these ARs with realistic magnetic configuration into a surface flux transport model, and simulate the creation and migration of the surge. Our simulations well reproduce the characteristics of the surge and show that the prominent surge is mainly caused by the ARs belonging to two ACs during Carrington rotations 2145–2159 (2013 December–2015 January). The surge has a strong influence on the polar field evolution of the southern hemisphere during the latter half of cycle 24. Without the about one-year-long flux emergence in the form of ACs, the polar field around the cycle minimum would have remained at a low level and even reversed to the polarity at cycle 23 minimum. Our study also shows that the long-lived unipolar regions due to the decay of the earlier emerging ARs cause an intrinsic difficulty of automatically identifying and precisely quantifying later emerging ARs in ACs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We describe the first spectroscopic tomographic (spectrotomographic) weak-lensing measurement for a galaxy cluster based only on background galaxies with spectroscopically determined redshifts. We use the massive cluster A2029 to demonstrate the power of combining spectroscopy and lensing to obtain accurate masses and to overcome biases from contamination and photometric redshift errors. We detect the shear signal from the cluster at &gt; 3.9<jats:italic>σ</jats:italic> significance. The shear signal scales with source redshift in a way that is consistent with the angular diameter distance ratio variation in a ΛCDM universe. Furthermore, the amplitude of the measured signal is consistent with the X-ray mass. Upcoming spectroscopic instruments such as the Prime Focus Spectrograph on Subaru will permit spectrotomographic weak-lensing measurements with a signal-to-noise ratio comparable with current photometric-redshift-based weak-lensing measurements for hundreds of galaxy clusters. Thus, spectrotomography may enable sensitive cosmological constraints that complement and are independent of other measurement techniques.</jats:p>