Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>The tip of the red giant branch has been used to measure distances to 500 nearby galaxies with the Hubble Space Telescope (HST) which are available in the Color–Magnitude Diagrams and Tip of the Red Giant Branch (CMDs/TRGB) catalog on the Extragalactic Distance Database (EDD). Our established methods are employed to perform an independent reduction of the targets presented by the Carnegie-Chicago Hubble Program (CCHP) in the series of papers culminating in Freedman (2021). Our distinct methodology involves modeling the observed luminosity function of red giant branch and asymptotic giant branch stars, which differs from the edge-detection algorithms employed by the CCHP. We find excellent agreement between distances for 11 hosts with new imaging, all at <jats:italic>D</jats:italic> &lt; 20 Mpc. However, we are unable to measure the TRGB for four hosts that use archival data designed to measure distances with Cepheids, all at <jats:italic>D</jats:italic> &gt; 23 Mpc. With two new HST observations taken in the halo of the megamaser host NGC 4258, the first with the same ACS <jats:italic>F</jats:italic>606<jats:italic>W</jats:italic> and <jats:italic>F</jats:italic>814<jats:italic>W</jats:italic> filters and state of the electronics used for SN Ia hosts, we then calibrate our TRGB distance scale to the geometric megamaser distance. Using our TRGB distances, we find a value of the Hubble Constant of <jats:italic>H</jats:italic> <jats:sub>0</jats:sub> = 71.5 ± 1.8 km s<jats:sup>−1</jats:sup> Mpc<jats:sup>−1</jats:sup> when using either the Pantheon or Carnegie Supernova Project (CSP) samples of supernovae. In the future, the James Webb Space Telescope will extend measurements of the TRGB to additional hosts of SN Ia and surface-brightness fluctuation measurements for separate paths to <jats:italic>H</jats:italic> <jats:sub>0</jats:sub>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This paper reports a recent development of the high-order spectral difference method with divergence cleaning (SDDC) for accurate simulations of both ideal and resistive magnetohydrodynamics (MHD) on curved unstructured grids consisting of high-order isoparametric quadrilateral elements. The divergence cleaning approach is based on the improved generalized Lagrange multiplier, which is thermodynamically consistent. The SDDC method can achieve an arbitrarily high order of accuracy in spatial discretization, as demonstrated in the test problems with smooth solutions. The high-order SDDC method combined with the artificial dissipation method can sharply capture shock interfaces with the oscillation-free property and resolve small-scale vortex structures and density fluctuations on relatively sparse grids. The robustness of the codes is demonstrated through long time simulations of ideal MHD problems with progressively interacting shock structures, resistive MHD problems with high Lundquist numbers, and viscous resistive MHD problems on complex curved domains.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Radio emission of the quiet Sun is considered to be due to thermal bremsstrahlung emission of the hot solar atmosphere. The properties of the quiet Sun in the microwave band have been well studied, and they can be well described by the spectrum of bremsstrahlung emission. In the meter-wave and decameter-wave bands, properties of the quiet Sun have rarely been studied due to the instrumental limitations. In this work, we use the LOw Frequency ARray telescope to perform high quality interferometric imaging spectroscopy observations of quiet Sun coronal emission at frequencies below 90 MHz. We present the brightness temperature spectrum and the size of the Sun in the frequency range of 20–80 MHz. We report on dark coronal regions with low brightness temperatures that persist with frequency. The brightness temperature spectrum of the quiet Sun is discussed and compared with the bremsstrahlung emission of a coronal model and previous quiet Sun observations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Coupling between active galactic nuclei (AGNs) and the circumgalactic medium (CGM) is critical to the interplay between radiative cooling and feedback heating in the atmospheres of the universe’s most massive galaxies. This paper presents a detailed analysis of numerical simulations showing how kinetic AGN feedback with a strong momentum flux interacts with the CGM. Our analysis shows that large-scale CGM circulation driven by that momentum flux plays an important role in reconfiguring the galactic atmosphere and regulating the atmosphere’s central entropy level. We find that most of the AGN's energy output goes into lifting of circumgalactic gas rather than heating of atmospheric gas within the galaxy, consequently reconfiguring the CGM by replacing low-entropy gas originally in the core with higher-entropy gas from larger radii. Circulation of the CGM on ∼10–100 kpc scales therefore plays a critical role in preventing overcooling of gas in these simulated galaxies, but leads to elevated entropy profiles ∼1–10 kpc compared to the observed entropy profiles of massive elliptical galaxies in the same mass range. The simulations also show that our choices of accretion efficiency and jet opening angle significantly affect the AGN–CGM coupling. Reducing the jet opening angle to one-quarter of the fiducial opening angle increases the jet momentum flux, enabling it to drill through to larger radii without effectively coupling with the CGM at the center (<jats:italic>r</jats:italic> &lt; 5 kpc). Outflows with a lower momentum flux decelerate and thermalize the bulk of their energy at smaller radii (<jats:italic>r</jats:italic> ≲ 10 kpc).</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We provide uniform RR Lyrae-based distances to 39 dwarf galaxies in and around the Local Group. We determine distances based on a Bayesian hierarchical model that uses periods and magnitudes of published RR Lyrae in dwarf galaxies and is anchored to well-studied Milky Way (MW) RR Lyrae with spectroscopic metallicities and Gaia eDR3 parallaxes. Gaia eDR3 parallaxes for the anchor sample are a factor of 2, on average, more precise than DR2 parallaxes, and allow for a much better constrained period–luminosity–metallicity relation. While ∼75% of our distances are within 1<jats:italic>σ</jats:italic> of recent RR Lyrae distances in the literature, our distances are also ∼2–3 times more precise than distances in the literature, on average. On average, our distances are ∼0.05 mag closer than distances in the literature, as well as ∼0.06 mag closer than distances derived using a theoretical period–luminosity–metallicity relation. These discrepancies are largely due to our eDR3 parallax anchor. We show that the Hipparcos-anchored RR Lyrae distance scale of Carretta et al. overpredicts distances to MW RR Lyrae by ∼0.05 mag. The largest uncertainties in our distances are (i) the lack of direct metallicity measurements for RR Lyrae and (ii) the heterogeneity of published RR Lyrae photometry. We provide simple formulae to place new dwarf galaxies with RR Lyrae on a common distance scale with this work. We provide a public code that can easily incorporate additional galaxies and data from future surveys, providing a versatile framework for the cartography of the local universe with RR Lyrae.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The elemental ratios of carbon, nitrogen, and oxygen in the atmospheres of hot Jupiters may hold clues to their formation locations in the protostellar disk. In this work, we adopt gas-phase chemical abundances of C, N, and O from several locations in a disk chemical kinetics model as sources for the envelope of the hot Jupiter HD 209458b and evolve the atmospheric composition of the planet using a 1D chemical kinetics model, treating both vertical mixing and photochemistry. We consider two atmospheric pressure-temperature profiles, one with and one without a thermal inversion. From each of the resulting 32 atmospheric composition profiles, we find that the molecules CH<jats:sub>4</jats:sub>, NH<jats:sub>3</jats:sub>, HCN, and C<jats:sub>2</jats:sub>H<jats:sub>2</jats:sub> are more prominent in the atmospheres computed using a realistic noninverted <jats:italic>P</jats:italic>–<jats:italic>T</jats:italic> profile in comparison to a prior equilibrium chemistry based work, which used an analytical <jats:italic>P</jats:italic>–<jats:italic>T</jats:italic> profile. We also compute the synthetic transmission and emission spectra for these atmospheres and find that many spectral features vary with the location in the disk where the planetary envelope was accreted. By comparing with the species detected using the latest high-resolution ground-based observations, our model suggests that HD 209458b could have accreted most of its gas between the CO<jats:sub>2</jats:sub> and CH<jats:sub>4</jats:sub> ice lines with a supersolar C/O ratio from its protostellar disk, which in turn directly inherited its chemical abundances from the protostellar cloud. Finally, we simulate observing the planet with the James Webb Space Telescope (JWST) and show that differences in spectral signatures of key species can be recognized. Our study demonstrates the enormous importance of JWST in providing new insights into hot-Jupiter formation environments.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Well-characterized binary systems will provide valuable opportunities to study the conditions that are necessary for the onset of both auroral and nonauroral magnetospheric radio emission in the ultracool dwarf regime. We present new detections of nonauroral “quiescent” radio emission at 4–8 GHz of the three ultracool dwarf binary systems GJ 564 BC, LP 415-20, and 2MASS J21402931+1625183. We also tentatively detect a highly circularly polarized pulse at 4–6 GHz that may indicate aurorae from GJ 564 BC. Finally, we show that the brightest binary ultracool dwarf systems may be more luminous than predictions from single-object systems.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The infrared solar spectrum contains a wealth of physical data about the Sun and is being explored using modern detectors and technology with new ground-based solar telescopes. One such instrument will be the ground-based Cryogenic Near-IR Spectro-Polarimeter of the Daniel K. Inouye Solar Telescope (DKIST), which will be capable of sensitive imaging of the faint infrared solar coronal spectra with full Stokes I, Q, U, and V polarization states. Highly ionized magnetic dipole emission lines have been observed in galaxies and the solar corona. Quantifying the accuracy of spectral inversion procedures requires a precise spectroscopic calibration of observations. A careful interpretation of the spectra around prominent magnetic dipole lines is essential for deriving physical parameters and particularly for quantifying the off-limb solar coronal observations from DKIST. In this work, we aim to provide an analysis of the spectral regions around the infrared coronal emission lines of Fe <jats:sc>xiii</jats:sc> 1074.68 nm, Fe <jats:sc>xiii</jats:sc> 1079.79 nm, Si <jats:sc>x</jats:sc> 1430.10 nm, and Si <jats:sc>ix</jats:sc> 3934.34 nm, aligning with the goal of identifying solar photospheric and telluric lines that will help facilitate production of reliable inversions and data products from four sets of solar coronal observations. The outputs can be integrated in processing pipelines to produce level 2 science-ready data.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We observed the nearly edge-on debris disk system HD 111520 at the <jats:italic>HJ</jats:italic> and <jats:italic>K</jats:italic>1 near-infrared (NIR) bands using both the spectral and polarization modes of the Gemini Planet Imager. With these new observations, we have performed an empirical analysis in order to better understand the disk morphology and its highly asymmetrical nature. We find that the disk features a large brightness and radial asymmetry, most prominent at shorter wavelengths. We also find that the radial location of the peak polarized intensity differs on either side of the star by 11 au, suggesting that the disk may be eccentric, although, such an eccentricity does not fully explain the large brightness and radial asymmetry observed. Observations of the disk halo with the Hubble Space Telescope also show the disk to be warped at larger separations, with a bifurcation feature in the northwest, further suggesting that there may be a planet in this system creating an asymmetrical disk structure. Measuring the disk color shows that the brighter extension is bluer compared to the dimmer extension, suggesting that the two sides have different dust grain properties. This finding, along with the large brightness asymmetry, are consistent with the hypothesis that a giant impact occurred between two large bodies in the northern extension of the disk, although confirming this based on NIR observations alone is not feasible. Follow-up imaging with the Atacama Large Millimeter/submillimeter Array to resolve the asymmetry in the dust mass distribution is essential in order to confirm this scenario.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Linear analysis of gas flows around orbiting binaries suggests that a centrifugal barrier ought to clear a low-density cavity around the binary and inhibit mass transfer onto it. Modern hydrodynamics simulations have confirmed the low-density cavity, but show that any mass flowing from large scales into the circumbinary disk is eventually transferred onto the binary components. Even though many numerical studies confirm this picture, it is still not understood precisely how gas parcels overcome the centrifugal barrier and ultimately accrete. We present a detailed analysis of the binary accretion process, using an accurate prescription for evolving grid-based hydrodynamics with Lagrangian tracer particles that track the trajectories of individual gas parcels. We find that binary accretion can be described in four phases: (1) gas is viscously transported through the circumbinary disk up to the centrifugal barrier at the cavity wall, (2) the cavity wall is tidally distorted into accretion streams consisting of near-ballistic gas parcels on eccentric orbits, (3) the portion of each stream moving inwards of an <jats:italic>accretion horizon</jats:italic> radius <jats:inline-formula> <jats:tex-math> <?CDATA $\bar{r}\simeq a$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>r</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> <mml:mo>≃</mml:mo> <mml:mi>a</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac6c2bieqn1.gif" xlink:type="simple" /> </jats:inline-formula>—the radius beyond which no material is returned to the cavity wall—becomes bound to a minidisk orbiting an individual binary component, and (4) the minidisk gas accretes onto the binary component through the combined effect of viscous and tidal stresses.</jats:p>