Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Polycyclic aromatic hydrocarbons (PAHs) have long been invoked in the study of interstellar and protostellar sources, but the unambiguous identification of any individual PAH has proven elusive until very recently. As a result, the formation mechanisms for this important class of molecules remain poorly constrained. Here we report the first interstellar detection of a pure hydrocarbon PAH, indene (C<jats:sub>9</jats:sub>H<jats:sub>8</jats:sub>), as part of the GBT Observations of TMC-1: Hunting for Aromatic Molecules (GOTHAM) survey. This detection provides a new avenue for chemical inquiry, complementing the existing detections of CN-functionalized aromatic molecules. From fitting the GOTHAM observations, indene is found to be the most abundant organic ring detected in TMC-1 to date. And from astrochemical modeling with <jats:monospace>nautilus</jats:monospace>, the observed abundance is greater than the model’s prediction by several orders of magnitude, suggesting that current formation pathways in astrochemical models are incomplete. The detection of indene in relatively high abundance implies related species such as cyanoindene, cyclopentadiene, toluene, and styrene may be detectable in dark clouds.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We use the gravitational wave signals from binary black hole merger events observed by LIGO and Virgo to reconstruct the underlying mass and spin distributions of the population of merging black holes. We reconstruct the population using the mixture model framework VAMANA using observations in GWTC-2 occurring during the first two observing runs and the first half of the third run (O1, O2, and O3a). Our analysis identifies a structure in the chirp mass distribution of the observed population. Specifically, we identify peaks in the chirp mass distribution at 8, 14, 26, and 45 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> and a complementary structure in the component mass distribution with an excess of black holes at masses of 9, 16, 45, and 57 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. Intriguingly, for both the distributions, the location of subsequent peaks are separated by a factor of around two and there is a lack of mergers with chirp masses of 10–12 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. The appearance of multiple peaks is a feature of a hierarchical merger scenario when, due to a gap in the black hole mass spectrum, a pile-up occurs at the first peak followed by mergers of lower mass black holes to hierarchically produce higher mass black holes. However, cross-generation merger peaks and observations with high spins are also predicted to occur in such a scenario that we are not currently observing. The results presented are limited in measurement accuracy due to small numbers of observations but if corroborated by future gravitational wave observations these features have far-reaching implications.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Finding and characterizing extrasolar Earth analogs will rely on interpretation of the planetary system’s environmental context. The total budget and fractionation between C–H–O species sensitively affect the climatic and geodynamic state of terrestrial worlds, but their main delivery channels are poorly constrained. We connect numerical models of volatile chemistry and pebble coagulation in the circumstellar disk with the internal compositional evolution of planetesimals during the primary accretion phase. Our simulations demonstrate that disk chemistry and degassing from planetesimals operate on comparable timescales and can fractionate the relative abundances of major water and carbon carriers by orders of magnitude. As a result, individual planetary systems with significant planetesimal processing display increased correlation in the volatile budget of planetary building blocks relative to no internal heating. Planetesimal processing in a subset of systems increases the variance of volatile contents across planetary systems. Our simulations thus suggest that exoplanetary atmospheric compositions may provide constraints on <jats:italic>when</jats:italic> a specific planet formed.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Interior models of giant planets traditionally assume that at a given radius (i.e., pressure) the density should be larger than or equal to the one corresponding to a homogeneous, adiabatic stratification throughout the planet (referred to as the “outer adiabat”). The observations of Jupiter’s gravity field by Juno combined with the constraints on its atmospheric composition appear to be incompatible with such a profile. In this Letter, we show that the above assumption stems from an incorrect understanding of the Schwarzschild–Ledoux criterion, which is only valid on a local scale. In order to fulfill the buoyancy stability condition, the density gradient with pressure in a nonadiabatic region must indeed rise more steeply than the <jats:italic>local</jats:italic> adiabatic density gradient. However, the density gradient can be smaller than the one corresponding to the outer adiabat at the same pressure because of the higher temperature in an inhomogeneously stratified medium. Deep enough, the density can therefore be lower than the one corresponding to the outer adiabat. We show that this is permitted only if the slope of the local adiabat becomes shallower than the slope of the outer adiabat at the same pressure, as found in recent Jupiter models due to the increase of both specific entropy and adiabatic index with depth. We examine the dynamical stability of this structure and show that it is stable against nonadiabatic perturbations. The possibility of such an unconventional density profile in Jupiter further complicates our understanding of the internal structure and evolution of (extrasolar) giant planets.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We identify an effective proxy for the analytically unknown second integral of motion (<jats:italic>I</jats:italic> <jats:sub>2</jats:sub>) for rotating barred or tri-axial potentials. Planar orbits of a given energy follow a tight sequence in the space of the time-averaged angular momentum and its amplitude of fluctuation. The sequence monotonically traces the main orbital families in the Poincaré map, even in the presence of resonant and chaotic orbits. This behavior allows us to define the calibrated angular momentum, the average angular momentum (<jats:inline-formula> <jats:tex-math> <?CDATA $\overline{{L}_{z}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlabfdb2ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>) normalized by the amplitude of its fluctuation (<jats:inline-formula> <jats:tex-math> <?CDATA ${\sigma }_{{L}_{z}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlabfdb2ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>), as a numerical proxy for <jats:italic>I</jats:italic> <jats:sub>2</jats:sub>. It also implies that the amplitude of fluctuation in <jats:italic>L</jats:italic> <jats:sub> <jats:italic>z</jats:italic> </jats:sub>, previously underappreciated, contains valuable information. This new proxy allows one to classify orbital families easily and accurately, even for real orbits in <jats:italic>N</jats:italic>-body simulations of barred galaxies. It is a good diagnostic tool of dynamical systems, and may facilitate the construction of equilibrium models.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report a ≈400 hr Giant Metrewave Radio Telescope (GMRT) search for H<jats:sc>i</jats:sc> 21 cm emission from star-forming galaxies at <jats:italic>z</jats:italic> = 1.18–1.39 in seven fields of the DEEP2 Galaxy Survey. Including data from an earlier 60 hr GMRT observing run, we co-added the H<jats:sc>i</jats:sc> 21 cm emission signals from 2841 blue star-forming galaxies that lie within the FWHM of the GMRT primary beam. This yielded a 5.0<jats:italic>σ</jats:italic> detection of the average H<jats:sc>i</jats:sc> 21 cm signal from the 2841 galaxies at an average redshift 〈<jats:italic>z</jats:italic>〉 ≈ 1.3, only the second detection of H<jats:sc>i</jats:sc> 21 cm emission at <jats:italic>z</jats:italic> ≥ 1. We obtain an average H<jats:sc>i</jats:sc> mass of 〈M<jats:sub> <jats:sc>HI</jats:sc> </jats:sub>〉 = (3.09 ± 0.61) × 10<jats:sup>10</jats:sup> M<jats:sub>⊙</jats:sub> and an H<jats:sc>i</jats:sc>-to-stellar mass ratio of 2.6 ± 0.5, both significantly higher than values in galaxies with similar stellar masses in the local universe. We also stacked the 1.4 GHz continuum emission of the galaxies to obtain a median star formation rate (SFR) of 14.5 ± 1.1 M<jats:sub>⊙</jats:sub>yr<jats:sup>−1</jats:sup>. This implies an average H<jats:sc>i</jats:sc> depletion timescale of ≈2 Gyr for blue star-forming galaxies at <jats:italic>z</jats:italic> ≈ 1.3, a factor of ≈3.5 lower than that of similar local galaxies. Our results suggest that the H<jats:sc>i</jats:sc> content of galaxies toward the end of the epoch of peak cosmic SFR density is insufficient to sustain their high SFR for more than ≈2 Gyr. Insufficient gas accretion to replenish the H<jats:sc>i</jats:sc> could then explain the observed decline in the cosmic SFR density at <jats:italic>z</jats:italic> &lt; 1.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We show that the James Webb Space Telescope (JWST) will be able to detect dwarf satellites of high-<jats:italic>z</jats:italic> Lyman break galaxies (LBGs). To this end, we use cosmological simulations following the evolution of a typical <jats:italic>M</jats:italic> <jats:sub>⋆</jats:sub> ≃ 10<jats:sup>10</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> LBG up to <jats:italic>z</jats:italic> ≃ 6, and analyze the observational properties of its five satellite dwarf galaxies (10<jats:sup>7</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> &lt; <jats:italic>M</jats:italic> <jats:sub>⋆</jats:sub> &lt; 10<jats:sup>9</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>). Modeling their stellar emission and dust attenuation, we reconstruct their rest-frame ultraviolet-optical spectra for 6 &lt; <jats:italic>z</jats:italic> &lt; 6.5. JWST/NIRCam synthetic images show that the satellites can be spatially resolved from their host, and their emission is detectable by planned deep surveys. Moreover, we build synthetic spectral energy distributions and color–magnitude diagrams for the satellites. We conclude that the color F200W–F356W is a powerful diagnostic tool for understanding their physical properties once they have been identified. For example, F200W–F356W ≲ −0.25 can be used to identify star-bursting (SFR ∼ 5 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> yr<jats:sup>−1</jats:sup>), low-mass (<jats:italic>M</jats:italic> <jats:sub>⋆</jats:sub> ≲ 5 × 10<jats:sup>8</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) systems, with ∼80% of their stars being young and metal poor <jats:inline-formula> <jats:tex-math> <?CDATA $[\mathrm{log}({Z}_{\star }/{Z}_{\odot })\lt -0.5$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlabfe6cieqn1.gif" xlink:type="simple" /> </jats:inline-formula>].</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Brown dwarfs with well-determined ages, luminosities, and masses provide rare but valuable tests of low-temperature atmospheric and evolutionary models. We present the discovery and dynamical mass measurement of a substellar companion to HD 47127, an old (≈7–10 Gyr) G5 main-sequence star with a mass similar to the Sun. Radial velocities of the host star with the Harlan J. Smith Telescope uncovered a low-amplitude acceleration of 1.93 ± 0.08 m s<jats:sup>−1</jats:sup> yr<jats:sup>−1</jats:sup> based on 20 years of monitoring. We subsequently recovered a faint (Δ<jats:italic>H</jats:italic> = 13.14 ± 0.15 mag) comoving companion at 1.″95 (52 au) with follow-up Keck/NIRC2 adaptive optics imaging. The radial acceleration of HD 47127 together with its tangential acceleration from Hipparcos and Gaia EDR3 astrometry provide a direct measurement of the three-dimensional acceleration vector of the host star, enabling a dynamical mass constraint for HD 47127 B (67.5–177 <jats:italic>M</jats:italic> <jats:sub>Jup</jats:sub> at 95% confidence) despite the small fractional orbital coverage of the observations. The absolute <jats:italic>H</jats:italic>-band magnitude of HD 47127 B is fainter than the benchmark T dwarfs HD 19467 B and Gl 229 B but brighter than Gl 758 B and HD 4113 C, suggesting a late-T spectral type. Altogether the mass limits for HD 47127 B from its dynamical mass and the substellar boundary imply a range of 67–78 <jats:italic>M</jats:italic> <jats:sub>Jup</jats:sub> assuming it is single, although a preference for high masses of ≈100 <jats:italic>M</jats:italic> <jats:sub>Jup</jats:sub> from dynamical constraints hints at the possibility that HD 47127 B could itself be a binary pair of brown dwarfs or that another massive companion resides closer in. Regardless, HD 47127 B will be an excellent target for more refined orbital and atmospheric characterization in the future.</jats:p>