Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Closure phases and closure amplitudes have proven critical to modern radio interferometry due to their insensitivity to the uncertain station gains. We present the first set of closure quantities constructed from parallel-hand and cross-hand visibilities that are insensitive to both station gains and to polarimetric leakage. These complex “closure traces” are a natural extension of closure amplitudes and closure phases, are independent of all station-based linear corruptions of the polarized visibilities, and are complete in the sense that they contain all remaining information present in the visibility data. Products of closure traces on so-called “conjugate” quadrangles are sensitive only to structure in the source polarization fraction—independent of variations in the Stokes <jats:italic>I</jats:italic> structure—and thereby provide unambiguous probes of polarization in astronomical sources.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Recent deep millimeter-wave surveys have attempted to measure the carbon monoxide (CO) luminosity function and mean molecular gas density through blind detections of CO emission lines. While the cosmic star formation rate density is now constrained in fields of hundreds of square arcminutes or more, molecular gas studies have been limited to ≤50 arcmin<jats:sup>2</jats:sup>. These small fields result in significant biases that have not been accounted for in published results. To quantify these biases, we assign CO luminosities to halos in cosmological simulations to produce mock observations for a range of field sizes. We find that fields of ≲10 arcmin<jats:sup>2</jats:sup> alter the recovered shape of the luminosity function, causing underestimates of the number of bright objects. Our models suggest that current surveys are sensitive enough to detect sources responsible for approximately half of the cosmic molecular gas density at high redshift. However, uncertainties in the gas density measurement are large, and cosmic variance may double the uncertainty claimed in these surveys. As a result, the field size needed to detect redshift evolution in the molecular gas at high confidence may be more than one order of magnitude larger than what current surveys have achieved. Shot power intensity mapping measurements are particularly sensitive to Poisson variance and require yet larger areas to constrain the gas density or its evolution. We provide a simple prescription for approximating uncertainty in total CO emission as a function of survey area and redshift for both direct detection and intensity mapping surveys.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a detailed theoretical exploration of the refractory compositions and volatile enrichments of planets forming in protoplanetary disks with solar-like conditions. The two cases of the Sun and WASP-12 are studied due to the availability of spectral measurements and their known planets. The distribution throughout their disks of solid compounds with a wide range of volatilities is computed by a comprehensive chemical thermodynamics code. After the calculation of refractory compounds down to the water snowline, the compositional distributions are documented for planets generated in certain locations of protoplanetary disks depending on thermodynamic conditions. These results are referred to proposed bulk compositions for solar terrestrial planets, and for the core of the hot Jupiter WASP-12b. The material left over after the formation of rocky components is collected and treated in calculations to determine the abundances of fundamental volatile molecules in the outer regions of the disks. The distributions of planetesimal volatile composition are then altered for four different cases of the carbon-to-oxygen ratios, and for oxidizing and reducing conditions, in order to adjust the best fit for the accretion zone of Jupiter and WASP-12b. We compare the Jovian results to in situ atmospheric measurements from Jupiter’s atmosphere. Overall, this study proposes a holistic approach to estimate possible planetary interior and envelope compositions from hot toward cold disk zones, along with the mass of planetesimals accreted into the envelopes of gas giants.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The atomic-to-molecular (H <jats:sc>i</jats:sc>-to-H<jats:sub>2</jats:sub>) transition in photodissociation regions (PDRs) has been investigated over the past several decades through analytic and numerical modeling. However, classical PDR models typically assume a uniform-density gas, ignoring the turbulent nature of the interstellar medium. Recently, Bialy et al. have presented a theoretical framework for studying the H <jats:sc>i</jats:sc>-to-H<jats:sub>2</jats:sub> transition in a realistic turbulent medium with a nonhomogeneous density structure. Here we extend these turbulent-chemical models to explore the possibility of tracing the magnetic field direction in turbulent PDRs using the gradient technique. We utilize both subsonic and supersonic magnetohydrodynamic numerical simulations for chemical H <jats:sc>i</jats:sc>/H<jats:sub>2</jats:sub> balance calculations. We confirm that the density fluctuations induced by turbulence can disperse the distribution of the H<jats:sub>2</jats:sub> and H <jats:sc>i</jats:sc> fractions. We find that the energy spectrum of moment maps gets shallower when the sonic Mach number <jats:italic>M</jats:italic> <jats:sub>S</jats:sub> increases. We explore the ability in magnetic field tracing of gradients of higher-order velocity centroids and compare their performance with that of traditional velocity centroid gradients (VCGs) and with intensity gradients (IGs). We find that the velocity gradients of the second-order centroids (VC<jats:sub>2</jats:sub>Gs) are more accurate than VCGs and IGs in probing the magnetic field orientation.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The atmospheres on tidally locked planets likely exhibit large differences between their day- and night-sides. In this paper, we illustrate how the combined effects of aerosols and day–night temperature gradients shape transit spectra of tidally locked exoplanets and evaluate the implications for retrievals of atmospheric properties. We have developed a new code, Multi-dimensional Exoplanet TransIt Spectra (METIS), which can compute transit spectra for arbitrary longitude–latitude–altitude grids of temperature and pressure. Using METIS, we pair flexible treatments of clouds and hazes with simple parameterized day–night temperature gradients to compute transit spectra and perform retrieval experiments across a wide array of possible exoplanet atmospheric properties. Our key findings are that: (1) the presence of aerosols can increase the effects of day–night temperature gradients on transit spectra; (2) ignoring day–night temperature gradients when attempting to perform Bayesian parameter estimation will return biased results, even when aerosols are present; (3) when a day–night temperature gradient is accounted for in the retrieval, some spectra contain sufficient information to constrain temperatures and the width of the transition from day to night. The presence of clouds and hazes can actually tighten such constraints, but also weaken constraints on metallicity and reference pressure. These last findings are predicated on the assumptions made in parameterizing the day–night atmospheric structure and the assumption of thermochemical equilibrium. Our results imply that this may be a promising avenue to pursue and represent a step toward the larger goal of developing models and theory of adequate complexity to match the superior-quality data that will soon be available.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Using 10 sight lines observed with the Hubble Space Telescope/Cosmic Origins Spectrograph, we study the circumgalactic medium (CGM) and outflows of IC 1613, which is a low-mass (<jats:italic>M</jats:italic> <jats:sub>*</jats:sub> ∼ 10<jats:sup>8</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>), dwarf irregular galaxy on the outskirts of the Local Group. Among the sight lines, four are pointed toward UV-bright stars in IC 1613, and the other six sight lines are background QSOs at impact parameters from 6 kpc (&lt;0.1<jats:italic>R</jats:italic> <jats:sub>200</jats:sub>) to 61 kpc (0.6<jats:italic>R</jats:italic> <jats:sub>200</jats:sub>). We detect a number of Si <jats:sc>ii</jats:sc>, Si <jats:sc>iii</jats:sc>, Si <jats:sc>iv</jats:sc>, C <jats:sc>ii</jats:sc>, and C <jats:sc>iv</jats:sc> absorbers, most of which have velocities less than the escape velocity of IC 1613 and thus are gravitationally bound. The line strengths of these ion absorbers are consistent with the CGM absorbers detected in dwarf galaxies at low redshifts. Assuming that Si <jats:sc>ii</jats:sc>, Si <jats:sc>iii</jats:sc>, and Si <jats:sc>iv</jats:sc> comprise nearly 100% of the total silicon, we find 3% (∼8 × 10<jats:sup>3</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>), 2% (∼7 × 10<jats:sup>3</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>), and 32%–42% [∼(1.0–1.3) × 10<jats:sup>5</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>] of the silicon mass in the stars, interstellar medium, and within 0.6<jats:italic>R</jats:italic> <jats:sub>200</jats:sub> of the CGM of IC 1613. We also estimate the metal outflow rate to be <jats:inline-formula> <jats:tex-math> <?CDATA ${\dot{{\rm{M}}}}_{\mathrm{out},{\rm{Z}}}\geqslant 1.1\times {10}^{-5}\,{{\rm{M}}}_{\odot }\,{\mathrm{yr}}^{-1}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabc875ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> and the instantaneous metal mass loading factor to be <jats:italic>η</jats:italic> <jats:sub>Z</jats:sub> ≥ 0.004, which are in broad agreement with available observation and simulation values. This work is the first time a dwarf galaxy of such low mass is probed by a number of both QSO and stellar sight lines, and it shows that the CGM of low-mass, gas-rich galaxies can be a large reservoir enriched with metals from past and ongoing outflows.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Until recently, black holes (BHs) could be discovered only through accretion from other stars in X-ray binaries, or in merging double compact objects. Improvements in astrometric and spectroscopic measurements have made it possible to detect BHs also in noninteracting BH binaries (nBHBs) through a precise analysis of the companion’s motion. In this study, using an updated version of the <jats:monospace>StarTrack</jats:monospace> binary-star population modeling code and a detailed model of the Milky Way (MW) galaxy, we calculate the expected number of detections for Gaia and LAMOST surveys. We develop a formalism to convolve the binary population synthesis output with a realistic stellar density distribution, star formation history (SFH), and chemical evolution for the MW, which produces a probability distribution function of the predicted compact-binary population over the MW. This avoids the additional statistical uncertainty that is introduced by methods that Monte Carlo sample from binary population synthesis output to produce one potential specific realization of the MW compact-binary distribution, and our method is also comparatively fast to such Monte Carlo realizations. Specifically, we predict ∼41–340 nBHBs to be observed by Gaia, although the numbers may drop to ∼10–70 if the recent (≲100 Myr) star formation is low (∼1 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>  yr<jats:sup>−1</jats:sup>). For LAMOST we predict ≲14 detectable nBHBs, which is lower partially because its field of view covers just ∼6% of the Galaxy.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The dynamical stability of disk galaxies is sensitive to whether their anomalous rotation curves are caused by dark matter halos or Milgromian dynamics (MOND). We investigate this by setting up a MOND model of M33. We first simulate it in isolation for 6 Gyr, starting from an initial good match to the rotation curve (RC). Too large a bar and bulge form when the gas is too hot, but this is avoided by reducing the gas temperature. A strong bar still forms in 1 Gyr, but rapidly weakens and becomes consistent with the observed weak bar. Previous work showed this to be challenging in Newtonian models with a live dark matter halo, which developed strong bars. The bar pattern speed implies a realistic corotation radius of 3 kpc. However, the RC still rises too steeply, and the central line-of-sight velocity dispersion (LOSVD) is too high. We then add a constant external acceleration field of 8.4 × 10<jats:sup>−12</jats:sup> m s<jats:sup>−2</jats:sup> at 30° to the disk as a first-order estimate for the gravity exerted by M31. This suppresses buildup of material at the center, causing the RC to rise more slowly and reducing the central LOSVD. Overall, this simulation bears good resemblance to several global properties of M33, and highlights the importance of including even a weak external field on the stability and evolution of disk galaxies. Further simulations with a time-varying external field, modeling the full orbit of M33, will be needed to confirm its resemblance to observations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present observations of the four hyperfine structure components of the OH 18 cm transition (1612, 1665, 1667, and 1720 MHz) toward a filamentary dark cloud, the Pipe nebula, with the Green Bank Telescope. A statistical equilibrium analysis is applied to the spectra, and the kinetic temperature of a diffuse molecular gas surrounding dense cores is determined accurately; the derived temperature ranges from 40 to 75 K. From this result, we assess the heating effect on the filamentary structure of the nebula’s “stem” region due to UV photons from a nearby star <jats:italic>θ</jats:italic>-Ophiuchi and a possible filament–filament collision in the interface of the “stem” and “bowl” regions. In the stem region, the gas kinetic temperature is found to be almost independent of the apparent distance from <jats:italic>θ</jats:italic>-Ophiuchi: the UV-heating effect by the star is not visible. On the other hand, the gas kinetic temperature is raised, as high as ∼75 K, at the interface of the two filamentary structures. This result provides us with additional support for the filament–filament collision scenario in the Pipe nebula.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The discovery of high incidence of hot Jupiters in dense clusters challenges the field-based hot Jupiter formation theory. In dense clusters, interactions between planetary systems and flyby stars are relatively common. This has a significant impact on planetary systems, dominating hot Jupiter formation. In this paper, we perform high precision, few-body simulations of stellar flybys and subsequent planet migration in clusters. A large parameter space exploration demonstrates that close flybys that change the architecture of the planetary system can activate high eccentricity migration mechanisms: LK and planet–planet scattering, leading to high hot Jupiter formation rate in dense clusters. Our simulations predict that many of the hot Jupiters are accompanied by “ultra-cold Saturns,” expelled to apastra of thousands of astronomical units. This increase is particularly remarkable for planetary systems originally hosting two giant planets with semimajor axis ratios of ∼4 and the flyby star approaching nearly perpendicular to the planetary orbital plane. The estimated lower limit to the hot Jupiter formation rate of a virialized cluster is <jats:inline-formula> <jats:tex-math> <?CDATA $\sim 1.6\times {10}^{-4}{(\sigma /1\mathrm{km}{{\rm{s}}}^{-1})}^{5}{({a}_{{\rm{p}}}/20\mathrm{au})({M}_{{\rm{c}}}/1000{M}_{\odot })}^{-2}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabc619ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> Gyr<jats:sup>−1</jats:sup> per star, where <jats:italic>σ</jats:italic> is the cluster velocity dispersion, <jats:italic>a</jats:italic> <jats:sub>p</jats:sub> is the size of the planetary system, and <jats:italic>M</jats:italic> <jats:sub>c</jats:sub> is the mass of the cluster. Our simulations yield a hot Jupiter abundance that is ∼50 times smaller than that observed in the old open cluster M67. We expect that interactions involving binary stars, as well as a third or more giant planets, will close the discrepancy.</jats:p>