Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>The presence of asymptotic giant branch (AGB) stars in clusters provides key constraints for stellar models, as has been demonstrated with historical data from the Magellanic Clouds. In this work, we look for candidate AGB stars in M31 star clusters from the Panchromatic Hubble Andromeda Treasury survey. Our photometric criteria selects stars brighter than the tip of the red giant branch, which includes the bulk of the thermally pulsing AGB stars as well as early-AGB stars and other luminous cool giants expected in young stellar populations (e.g., massive red supergiants, and intermediate-mass red helium-burning stars). The AGB stars can be differentiated, a posteriori, using the ages already estimated for our cluster sample. 937 candidates are found within the cluster aperture radii, half (∼450) of which are very likely cluster members. Cross-matching with additional databases reveals two carbon stars and 10 secure variables among them. The field-corrected age distribution reveals the presence of young supergiants peaking at ages smaller than 10<jats:sup>8</jats:sup> yr, followed by a long tail of AGB stars extending up to the oldest possible ages. This long tail reveals the general decrease in the numbers of AGB stars from initial values of <jats:inline-formula> <jats:tex-math> <?CDATA $\sim 50\times {10}^{-6}{M}_{\odot }^{-1}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabad3aieqn1.gif" xlink:type="simple" /> </jats:inline-formula> at 10<jats:sup>8</jats:sup> yr down to <jats:inline-formula> <jats:tex-math> <?CDATA $\sim 5\times {10}^{-6}{M}_{\odot }^{-1}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabad3aieqn2.gif" xlink:type="simple" /> </jats:inline-formula> at 10<jats:sup>10</jats:sup> yr. Theoretical models of near-solar metallicity reproduce this general trend, although with localized discrepancies over some age intervals, whose origin is not yet identified. The entire catalog is released together with finding charts to facilitate follow-up studies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The detailed magnetic field structure of the dense core SL 42 (CrA-E) in the Corona Australis molecular cloud complex was investigated based on near-infrared polarimetric observations of background stars to measure dichroically polarized light produced by magnetically aligned dust grains. The magnetic fields in and around SL 42 were mapped using 206 stars, and curved magnetic fields were identified. On the basis of simple hourglass (parabolic) magnetic field modeling, the magnetic axis of the core on the plane of the sky was estimated to be 40° ± 3°. The plane-of-sky magnetic field strength of SL 42 was found to be 22.4 ± 13.9 <jats:italic>μ</jats:italic>G. Taking into account the effects of thermal/turbulent pressure and the plane-of-sky magnetic field component, the critical mass of SL 42 was obtained to be <jats:italic>M</jats:italic> <jats:sub>cr</jats:sub> = 21.2 ± 6.6 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, which is close to the observed core mass of <jats:italic>M</jats:italic> <jats:sub>core</jats:sub> ≈ 20 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. We thus conclude that SL 42 is in a condition close to the critical state if the magnetic fields lie near the plane of the sky. Because there is a very low-luminosity object toward the center of SL 42, it is unlikely that this core is in a highly subcritical condition (i.e., the magnetic inclination angle is significantly deviated from the plane of the sky). The core probably started to collapse from a nearly kinematically critical state. In addition to the hourglass magnetic field modeling, the Inoue &amp; Fukui mechanism may explain the origin of the curved magnetic fields in the SL 42 region.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The impact of streaming between baryons and dark matter on the first structures has been actively explored by recent studies. We investigate how the key results are affected by two popular approximations. One is to implement the streaming by accounting for only the relative motion while assuming “baryons trace dark matter” spatially at the initialization of simulation. This neglects the smoothing on the gas density taking place before the initialization. In our simulation initialized at <jats:italic>z</jats:italic> <jats:sub> <jats:italic>i</jats:italic> </jats:sub> = 200, it overestimates the gas density power spectrum by up to 40% at <jats:italic>k</jats:italic> ≈ 10<jats:sup>2</jats:sup> <jats:italic>h</jats:italic> Mpc<jats:sup>−1</jats:sup> at <jats:italic>z</jats:italic> = 20. Halo mass (<jats:italic>M</jats:italic> <jats:sub> <jats:italic>h</jats:italic> </jats:sub>) and baryonic fraction in halos (<jats:inline-formula> <jats:tex-math> <?CDATA ${f}_{b,h}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaba26eieqn1.gif" xlink:type="simple" /> </jats:inline-formula>) are also overestimated, but the relation between the two remains unchanged. The other approximation tested is to artificially amplify the density/velocity fluctuations in the cosmic mean density to simulate the first minihalos that form in overdense regions. This gives a head start to the halo growth while the subsequent growth is similar to that in the mean density. The growth in a true overdense region, on the other hand, is accelerated gradually in time. For example, raising <jats:italic>σ</jats:italic> <jats:sub>8</jats:sub> by 50% effectively transforms <jats:inline-formula> <jats:tex-math> <?CDATA $z\to \sqrt{1.5}z$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaba26eieqn2.gif" xlink:type="simple" /> </jats:inline-formula> in the halo mass growth history while, at 2<jats:italic>σ</jats:italic> overdensity, the growth is accelerated by a constant in redshift: <jats:inline-formula> <jats:tex-math> <?CDATA $z\to z+4.8$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaba26eieqn3.gif" xlink:type="simple" /> </jats:inline-formula>. As a result, halos have grown more massive in the former than in the latter before <jats:italic>z</jats:italic> ≈ 27 and vice versa after. The <jats:inline-formula> <jats:tex-math> <?CDATA ${f}_{b,h}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaba26eieqn4.gif" xlink:type="simple" /> </jats:inline-formula>–<jats:italic>M</jats:italic> <jats:sub> <jats:italic>h</jats:italic> </jats:sub> relation is unchanged in those cases as well, suggesting that the Population III formation rate for a given <jats:italic>M</jats:italic> <jats:sub> <jats:italic>h</jats:italic> </jats:sub> is insensitive to the tested approximations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We reexamine a 50+ yr old problem of deep central reversals predicted for strong solar spectral lines, in contrast to the smaller reversals seen in observations. We examine data and calculations for the resonance lines of H <jats:sc>i</jats:sc>, Mg <jats:sc>ii</jats:sc>, and Ca <jats:sc>ii</jats:sc>, the self-reversed cores of which form in the upper chromosphere. Based on 3D simulations, as well as data for the Mg <jats:sc>ii</jats:sc> lines from the Interface Region Imaging Spectrograph (IRIS), we argue that the resolution lies not in velocity fields on scales in either of the micro- or macroturbulent limits. Macroturbulence is ruled out using observations of optically thin lines formed in the upper chromosphere, and by showing that it would need to have unreasonably special properties to account for critical observations of the Mg <jats:sc>ii</jats:sc> resonance lines from the IRIS mission. The power in “turbulence” in the upper chromosphere may therefore be substantially lower than earlier analyses have inferred. Instead, in 3D calculations horizontal radiative transfer produces smoother source functions, smoothing out intensity gradients in wavelength and in space. These effects increase in stronger lines. Our work will have consequences for understanding the onset of the transition region, for understanding the energy in motions available for heating the corona, and for the interpretation of polarization data in terms of the Hanle effect applied to resonance line profiles.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The cosmic infrared background (CIB) anisotropies and cosmic microwave background (CMB) lensing are powerful measurements for exploring cosmological and astrophysical problems. In this work, we measure the autocorrelation power spectrum of the CIB anisotropies in the Herschel–SPIRE HerMES Large Mode Survey (HeLMS) field, and the cross-power spectrum with the CMB lensing measurements from the Planck satellite. The HeLMS field covers more than 270 deg<jats:sup>2</jats:sup>, which is much larger than in previous analysis. We use the Herschel Level 1 time stream data to merge the CIB maps at 250, 350, and 500 <jats:italic>μ</jats:italic>m bands, and mask the areas where the flux is greater than <jats:inline-formula> <jats:tex-math> <?CDATA $3\sigma \ (\sim 50\,\mathrm{mJy}/\mathrm{beam})$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabada1ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> or there are no measured data. We obtain the final CIB power spectra at 100 ≤ <jats:italic>ℓ</jats:italic> ≤ 20,000 by considering several effects, such as beam function, mode coupling, transfer function, and so on. We also calculate the theoretical CIB auto- and cross-power spectra of CIB and CMB lensing by assuming that the CIB emissivity follows a Gaussian distribution in redshift. We find that, for the CIB auto-power spectra, we obtain signal-to-noise ratios (S/Ns) of 15.9, 15.7, and 15.3 at 250, 350, and 500 <jats:italic>μ</jats:italic>m, and for the CIB ⨯ CMB lensing power spectra, S/Ns of 7.5, 7.0, and 6.2 at 250, 350, and 500 <jats:italic>μ</jats:italic>m, respectively. Comparing to previous works, the constraints on the relevant CIB parameters are improved by factors of 2– 5 in this study.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Amide molecules produced in space could play a key role in the formation of biomolecules on a young planetary object. However, the formation and chemical network of amide molecules in space is not well understood. In this work, Atacama Large Millimeter/submillimeter Array observations are used to study a number of amide(-like) molecules toward the high-mass star-forming region NGC 6334I. The first detections of cyanamide (NH<jats:sub>2</jats:sub>CN), acetamide (CH<jats:sub>3</jats:sub>C(O)NH<jats:sub>2</jats:sub>), and N-methylformamide (CH<jats:sub>3</jats:sub>NHCHO) are presented for this source. These are combined with analyses of isocyanic acid (HNCO) and formamide (NH<jats:sub>2</jats:sub>CHO), and a tentative detection of urea (carbamide; NH<jats:sub>2</jats:sub>C(O)NH<jats:sub>2</jats:sub>). Abundance correlations show that most amides are likely formed in related reactions occurring in ices on interstellar dust grains in NGC 6334I. However, in an expanded sample of sources, large abundance variations are seen for NH<jats:sub>2</jats:sub>CN that seem to depend on the source type, which suggests that the physical conditions within the source heavily influence the production of this species. The rich amide inventory of NGC 6334I strengthens the case that interstellar molecules can contribute to the emergence of biomolecules on planets.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We perform Ly<jats:italic>α</jats:italic> radiative transfer calculations to reproduce the Ly<jats:italic>α</jats:italic> properties of star-forming galaxies at high redshifts. We model a galaxy as a halo in which the density distributions of Ly<jats:italic>α</jats:italic> sources and H <jats:sc>i</jats:sc> plus dust medium are described with exponential functions. We also consider an outflow of the medium that represents a momentum-driven wind in a gravitational potential well. We successfully reproduce both the spectra and the surface brightness profiles of eight star-forming galaxies at <jats:italic>z</jats:italic> = 3–6 observed with the Multi-Unit Spectroscopic Explorer using this outflowing-halo model with Ly<jats:italic>α</jats:italic> scattering. The best-fit model parameters (i.e., the outflowing velocity and optical depth) for these galaxies are consistent with those in other studies. We examine the impacts of individual model parameters and input spectrum on the emerging spectrum and surface brightness profile. Further investigations of the correlations among observables (i.e., the spatial extent of Ly<jats:italic>α</jats:italic> halos and Ly<jats:italic>α</jats:italic> spectral features) and model parameters, and of spatially resolved spectra are presented as well. We demonstrate that the combination of spectrum and surface brightness profile provides strong constraints on model parameters and thus on the spatial/kinematic distributions of the medium.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Feedback from active galactic nuclei (AGNs) is expected to impact the amount of cold gas in galaxies by driving strong galactic winds, by preventing external gas inflows, or by changing the thermodynamical state of the gas. We use estimates of molecular gas mass based on dust absorption (H<jats:italic>α</jats:italic>/H<jats:italic>β</jats:italic>) to study gas content of large samples of type 2 AGN host galaxies in comparison with inactive galaxies. Using sparse principal component and clustering analysis, we analyze a suite of stellar and structural parameters of ∼27,100 face-on, central galaxies at redshift <jats:italic>z</jats:italic> = 0.02–0.15 and with stellar mass <jats:italic>M</jats:italic> <jats:sub>⋆</jats:sub> ≈ 10<jats:sup>10</jats:sup>–2 ×  10<jats:sup>11</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. We identify four galaxy groups of similar mass and morphology (mass surface density, velocity dispersion, concentration, and Sérsic index) that can be evolutionarily linked through a life cycle wherein gas content mediates their star formation rate (SFR) and level of AGN activity. Galaxies first consume their gas mostly through bursty star formation, then enter into a transition phase of intermediate gas richness in which star formation and AGNs coexist, before settling into retirement as gas-poor, quiescent systems with residual levels of AGN activity (LINERs). Strongly accreting black holes (Seyferts) live in gas-rich, star-forming hosts, but neither their gas reservoir nor their ability to form stars seems to be impacted <jats:italic>instantaneously</jats:italic> (timescales ≲0.5 Gyr) by AGN feedback. Our results are inconsistent with AGN feedback models that predict that central, bulge-dominated, Seyfert-like AGNs in massive galaxies have significantly lower molecular gas fractions than inactive galaxies of similar mass, morphology, and SFR.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present the first proper-motion (PM) measurements for the dwarf elliptical galaxies NGC 147 and NGC 185, two satellite galaxies of M31, using multiepoch Hubble Space Telescope (HST) imaging data with time baselines of ∼8 yr. For each galaxy, we take an error-weighted average of measurements from HST Advanced Camera for Surveys/WFC and Wide Field Camera 3/UVIS to determine the PMs. Our final results for the PMs are (<jats:italic>μ</jats:italic> <jats:sub>W</jats:sub>, <jats:italic>μ</jats:italic> <jats:sub>N</jats:sub>)<jats:sub>N147</jats:sub> = (−0.0232, 0.0378) ± (0.0143, 0.0146) mas yr<jats:sup>−1</jats:sup> for NGC 147 and (<jats:italic>μ</jats:italic> <jats:sub>W</jats:sub>, <jats:italic>μ</jats:italic> <jats:sub>N</jats:sub>)<jats:sub>N185</jats:sub> = (−0.0242, 0.0058) ± (0.0141, 0.0147) mas yr<jats:sup>−1</jats:sup> for NGC 185. The 2D direction of motion for NGC 147 about M31 is found to be aligned with its tidal tails. The 3D positions and velocities of both galaxies are transformed into a common M31-centric coordinate system to study the detailed orbital histories of the combined M31+NGC 147+NGC 185 system via numerical orbit integration. We find that NGC 147 (NGC 185) had its closest passage to M31 0.3–0.5 Gyr (≳1.6 Gyr) within the past 6 Gyr at distances of ∼70 kpc (70–260 kpc). The pericentric times of NGC 147/NGC 185 correlate qualitatively well with the presence/absence of tidal tails seen around the galaxies. Our PMs show that the orbital poles of NGC 147, as well as NGC 185, albeit to a lesser degree, agree within the uncertainties with the normal of the Great Plane of Andromeda (GPoA). These are the first measurements of the 3D angular momentum vector of any satellite identified as original GPoA members. Our results strengthen the hypothesis that the GPoA may be a dynamically coherent entity. We revisit previous claims that NGC 147 and NGC 185 are binary galaxies and conclude that it is very unlikely that the two galaxies were ever gravitationally bound to each other.</jats:p>