Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>In this work, we use the spectroscopy-based stellar color regression method with ∼0.7 million common stars between LAMOST DR7 and Gaia EDR3 to acquire color corrections in <jats:italic>G</jats:italic> − <jats:italic>G</jats:italic> <jats:sub>RP</jats:sub> and <jats:italic>G</jats:italic> <jats:sub>BP</jats:sub> − <jats:italic>G</jats:italic> <jats:sub>RP</jats:sub>. A sub-millimagnitude precision is achieved. Our results demonstrate that improvements in the calibration process of the EDR3 have removed the color term in <jats:italic>G</jats:italic> <jats:sub>BP</jats:sub> − <jats:italic>G</jats:italic> <jats:sub>RP</jats:sub> and eliminated the discontinuity caused by the changes of instrument configurations to a great extent. However, modest systematic trends with <jats:italic>G</jats:italic> magnitude are still detected. The corresponding color correction terms as a function of <jats:italic>G</jats:italic> are provided for 9.5 mag &lt; <jats:italic>G</jats:italic> &lt; 17.5 mag and compared with other determinations. We conclude that the corrections given in this work are particularly suited for cases where the color–color investigations are required, while for color–magnitude investigations other corrections may be better owing to systematics with reddening. Possible applications of our results are discussed.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Both observations and recent numerical simulations of the circumgalactic medium (CGM) support the hypothesis that a self-regulating feedback loop suspends the gas density of the ambient CGM close to the galaxy in a state with a ratio of cooling time to freefall time ≳10. This limiting ratio is thought to arise because circumgalactic gas becomes increasingly susceptible to multiphase condensation as the ratio declines. If the timescale ratio gets too small, then cold clouds precipitate out of the CGM, rain into the galaxy, and fuel energetic feedback that raises the ambient cooling time. The astrophysical origin of this so-called precipitation limit is not simple but is critical to understanding the CGM and its role in galaxy evolution. This paper therefore attempts to interpret its origin as simply as possible, relying mainly on conceptual reasoning and schematic diagrams. It illustrates how the precipitation limit can depend on both the global configuration of a galactic atmosphere and the degree to which dynamical disturbances drive CGM perturbations. It also frames some tests of the precipitation hypothesis that can be applied to both CGM observations and numerical simulations of galaxy evolution.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We use data from the ESA Gaia mission Early Data Release 3 (EDR3) to measure the trigonometric parallax of <jats:italic>ω</jats:italic> Cen, the first high-precision parallax measurement for the most massive globular cluster in the Milky Way. We use a combination of positional and high-quality proper motion data from EDR3 to identify over 100,000 cluster members, of which 67,000 are in the magnitude and color range where EDR3 parallaxes are best calibrated. We find the estimated parallax to be robust, demonstrating good control of systematics within the color–magnitude diagram of the cluster. We find a parallax for the cluster of 0.191 ± 0.001 (statistical) ±0.004 (systematic) mas (2.2% total uncertainty) corresponding to a distance of 5.24 ± 0.11 kpc. The parallax of <jats:italic>ω</jats:italic> Cen provides a unique opportunity to directly and geometrically calibrate the luminosity of the tip of the red giant branch (TRGB) because it is the only cluster with sufficient mass to provide enough red giant stars, more than 100 one magnitude below the tip, for a precise, model-free measurement of the tip. Combined with the preexisting and most widely used measurements of the tip and foreground Milky Way extinction, we find <jats:italic>M</jats:italic> <jats:sub> <jats:italic>I</jats:italic>,TRGB</jats:sub> =−3.97 ± 0.06 mag for the <jats:italic>I</jats:italic>-band luminosity of the blue edge. Using the TRGB luminosity calibrated from the Gaia EDR3 parallax of <jats:italic>ω</jats:italic> Cen to calibrate the luminosity of Type Ia supernovae results in a value for the Hubble constant of <jats:italic>H</jats:italic> <jats:sub>0</jats:sub> = 72.1 ± 2.0 km s<jats:sup>−1</jats:sup> Mpc<jats:sup>−1</jats:sup>. We make the data for the stars in <jats:italic>ω</jats:italic> Cen available electronically and encourage independent analyses of the results presented here.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present an expanded sample of 75 Milky Way Cepheids with Hubble Space Telescope <jats:italic>(</jats:italic>HST<jats:italic>)</jats:italic> photometry and Gaia EDR3 parallaxes, which we use to recalibrate the extragalactic distance ladder and refine the determination of the Hubble constant. All HST observations were obtained with the same instrument (WFC3) and filters (F555W, F814W, F160W) used for imaging of extragalactic Cepheids in Type Ia supernova (SN Ia) hosts. The HST observations used the WFC3 spatial scanning mode to mitigate saturation and reduce pixel-to-pixel calibration errors, reaching a mean photometric error of 5 millimags per observation. We use new Gaia EDR3 parallaxes, greatly improved since DR2, and the period–luminosity (P–L) relation of these Cepheids to simultaneously calibrate the extragalactic distance ladder and to refine the determination of the Gaia EDR3 parallax offset. The resulting geometric calibration of Cepheid luminosities has 1.0% precision, better than any alternative geometric anchor. Applied to the calibration of SNe Ia, it results in a measurement of the Hubble constant of 73.0 ± 1.4 km s<jats:sup>−1</jats:sup> Mpc<jats:sup>−1</jats:sup>, in good agreement with conclusions based on earlier Gaia data releases. We also find the slope of the Cepheid P–L relation in the Milky Way, and the metallicity dependence of its zero-point, to be in good agreement with the mean values derived from other galaxies. In combination with the best complementary sources of Cepheid calibration, we reach 1.8% precision and find <jats:italic>H</jats:italic> <jats:sub>0</jats:sub> = 73.2 ± 1.3 km s<jats:sup>−1</jats:sup> Mpc<jats:sup>−1</jats:sup>, a 4.2<jats:italic>σ</jats:italic> difference with the prediction from Planck CMB observations under ΛCDM. We expect to reach ∼1.3% precision in the near term from an expanded sample of ∼40 SNe Ia in Cepheid hosts.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We show that a combined analysis of cosmic microwave background anisotropy power spectra obtained by the Planck satellite and luminosity distance data simultaneously excludes a flat universe and a cosmological constant at 99% confidence level. These results hold separately when combining Planck with three different data sets: the two determinations of the Hubble constant from Riess et al. and Freedman et al., and the Pantheon catalog of high-redshift Type Ia supernovae. We conclude that either the Lambda cold dark matter model needs to be replaced by a different paradigm, or else there are significant but still undetected systematics. Our result calls for new observations and stimulates the investigation of alternative theoretical models and solutions.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The plethora of photometric data collected by the Kepler space telescope has promoted the detection of tens of thousands of stellar rotation periods. However, these periods are not found to an equal extent among different spectral types. Interestingly, early G-type stars with near-solar rotation periods are strongly underrepresented among those stars with known rotation periods. In this study we investigate whether the small number of such stars can be explained by difficulties in the period determination from photometric time series. For that purpose, we generate model light curves of early G-type stars with solar rotation periods for different inclination angles, metallicities, and (magnitude-dependent) noise levels. We find that the detectability is determined by the predominant type of activity (i.e., spot or faculae domination) on the surface, which defines the degree of irregularity of the light curve, and further depends on the level of photometric noise. These two effects significantly complicate the period detection and explain the lack of solar-like stars with known near-solar rotation periods. We conclude that the rotation periods of the majority of solar-like stars with near-solar rotation periods remain undetected to date. Finally, we promote the use of new techniques to recover more periods of near-solar rotators.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Collisions electrically charge grains, which promotes growth by coagulation. We present aggregation experiments with three large ensembles of basalt beads (150–180 <jats:italic>μ</jats:italic>m), two of which are charged, while one remains almost neutral as a control system. In microgravity experiments, free collisions within these samples are induced with moderate collision velocities (0–0.2 m s<jats:sup>−1</jats:sup>). In the control system, coagulation stops at (sub-)mm size while the charged grains continue to grow. A maximum agglomerate size of 5 cm is reached, limited only by bead depletion in the free volume. For the first time, charge-driven growth well into the centimeter range is directly proven by experiments. In protoplanetary disks, this agglomerate size is well beyond the critical size needed for hydrodynamic particle concentration as, e.g., by the streaming instabilities.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Black holes formed in the early universe, prior to the formation of stars, can exist as dark matter and also contribute to the black hole merger events observed in gravitational waves. We set a new limit on the abundance of primordial black holes (PBHs) by considering interactions of PBHs with the interstellar medium, which result in the heating of gas. We examine generic heating mechanisms, including emission from the accretion disk, dynamical friction, and disk outflows. Using the data from the Leo T dwarf galaxy, we set a new cosmology-independent limit on the abundance of PBHs in the mass range <jats:inline-formula> <jats:tex-math> <?CDATA ${ \mathcal O }(1){M}_{\odot }\mbox{--}{10}^{7}{M}_{\odot }$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlabdcb6ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, relevant for the recently detected gravitational-wave signals from intermediate-mass BHs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Active galactic nucleus (AGN) disks have been proposed as promising locations for the mergers of stellar-mass black hole binaries (BBHs). Much recent work has been done on this merger channel, but the majority focuses on stellar-mass black holes (BHs) orbiting in the prograde direction. Little work has been done to examine the impact of retrograde orbiters (ROs) on the formation and mergers of BBHs in AGN disks. Quantifying the retrograde contribution is important, as roughly half of all orbiters should initially be on retrograde orbits when the disk forms. We perform an analytic calculation of the evolution of ROs in an AGN disk. Because this evolution could cause the orbits of ROs to cross those of prograde BBHs, we derive the collision rate between a given RO and a given BBH orbiting in the prograde direction. In the examples given here, ROs in the inner region of the disk experience a rapid decrease in the semimajor axis of their orbits while also becoming highly eccentric in less than a million years. This rapid orbital evolution could lead to extreme mass ratio inspirals detectable by the Laser Interferometer Space Antenna. The collision rates of our example ROs with prograde BBHs in the migration trap depend strongly on the volume of the inner radiation-pressure-dominated region, which depends on the mass of the supermassive black hole (SMBH). Rates are lowest for larger-mass SMBHs, which dominate the AGN merger channel, suggesting that merger rates for this channel may not be significantly altered by ROs.</jats:p>