Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>The growth of supermassive black holes, especially the associated state of active galactic nuclei (AGNs), is generally believed to be the key step in regulating star formation in massive galaxies. As the fuel of star formation, the cold gas reservoir is a direct probe of the effect of AGN feedback on their host galaxies. However, in observations, no clear connection has been found between AGN activity and the cold gas mass. In this paper, we find observational signals of the significant depletion of the total neutral hydrogen gas reservoir in optically selected Type 2 AGN-host central galaxies of stellar mass 10<jats:sup>9</jats:sup>–10<jats:sup>10</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. The effect of AGN feedback on the cold gas reservoir is stronger for higher star formation rates and higher AGN luminosity. But it becomes much weaker above this mass range, consistent with previous findings focusing on massive galaxies. Our result suggests that low-mass and gas-rich AGN-host central galaxies would first form dense cores before AGN feedback is triggered, removing their neutral hydrogen gas. More massive central galaxies may undergo a significantly different formation scenario by gradually building up dense cores with less effective and recurrent AGN feedback.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Using proper motions from Gaia Early Data Release 3 (Gaia EDR3) and radial velocities from several surveys, we identify 60 candidate high-velocity stars with a total velocity greater than 75% of the escape velocity that probably originated from the Sagittarius dwarf spheroidal galaxy (Sgr) by orbital analysis. Sgr’s gravity has little effect on the results and the Large Magellanic Cloud’s gravity has a nonnegligible effect on only a few stars. The closest approach of these stars to the Sgr occurred when the Sgr passed its pericenter (∼38.2 Myr ago), which suggests they were tidally stripped from the Sgr. The positions of these stars in the Hertzsprung–Russell diagram and the chemical properties of 19 of them with available [Fe/H] are similar to the Sgr stream member stars. This is consistent with the assumption of their accretion origin. Two of the 60 are hypervelocity stars, which may also be produced by the Hills mechanism.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Coalescing binary black hole (BBH) systems are likely formed via several channels, and it is challenging to understand their formation/evolutionary processes. Some features in the mass function of the primary components (<jats:italic>m</jats:italic> <jats:sub>1</jats:sub>), such as the distinct Gaussian-like peak located at ∼34 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, have been previously found. In this work, we investigate the possible dependence of the mass ratio (<jats:italic>q</jats:italic> = <jats:italic>m</jats:italic> <jats:sub>2</jats:sub>/<jats:italic>m</jats:italic> <jats:sub>1</jats:sub>) distribution on the primary mass. We find a Bayesian odds ratio of 18.1 in favor of divergence in the mass ratio distributions between the low- and high-mass ranges over an invariable mass ratio distribution. BBHs with <jats:italic>m</jats:italic> <jats:sub>1</jats:sub> ≳ 29 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> have a stronger preference of being symmetric compared to those with <jats:italic>m</jats:italic> <jats:sub>1</jats:sub> ≲ 29 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> at a 97.6% credible level. Additionally, we find mild evidence that BBHs with <jats:italic>m</jats:italic> <jats:sub>1</jats:sub> located in the Gaussian-like peak have a mass ratio distribution different from that of other BBHs. Our findings may favor some formation channels, such as chemically homogeneous evolution and dynamical assembly in globular clusters/nuclear star clusters, which are more likely to provide symmetric BBHs in the high-mass range.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present Hubble Space Telescope observations of active asteroid P/2020 O1 taken to examine its development for a year after perihelion. We find that the mass loss peaks at ≲1 kg s<jats:sup>−1</jats:sup> in 2020 August and then declines to nearly zero over four months. Long-duration mass loss (∼180 days) is consistent with a sublimation origin, indicating that this object is likely an ice-bearing main-belt comet. Equilibrium sublimation of water ice from an area as small as 1580 m<jats:sup>2</jats:sup> can supply the observed mass loss. Time-series photometry shows tentative evidence for extremely rapid rotation (double-peaked period &lt;2 hr) of the small nucleus (effective radius ∼420 m). Ejection velocities of 0.1 mm particles are comparable to the 0.3 m s<jats:sup>−1</jats:sup> gravitational escape speed from the nucleus, while larger particles are ejected at speeds less than the escape velocity. These properties are consistent with the sublimation of near-surface ice aided by centripetal acceleration. If water-ice sublimation is confirmed, P/2020 O1 would be an icy asteroid with the smallest semimajor axis (highest temperature), setting new bounds on the distribution of ice in the asteroid belt.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The activation energies for desorption (<jats:italic>E</jats:italic> <jats:sub>des</jats:sub>) and for surface diffusion (<jats:italic>E</jats:italic> <jats:sub>sd</jats:sub>) of adsorbed molecules on dust grains are two of the most important parameters for the chemistry in the interstellar medium. Although <jats:italic>E</jats:italic> <jats:sub>des</jats:sub> is often measured by laboratory experiments, the measurement of <jats:italic>E</jats:italic> <jats:sub>sd</jats:sub> is sparse. Due to the lack of data, astrochemical models usually assume a simple scaling relation, <jats:italic>E</jats:italic> <jats:sub>sd</jats:sub> = <jats:italic>f</jats:italic> <jats:italic>E</jats:italic> <jats:sub>des</jats:sub>, where <jats:italic>f</jats:italic> is a constant, irrespective of the adsorbed species. Here, we experimentally measure <jats:italic>E</jats:italic> <jats:sub>sd</jats:sub> for CH<jats:sub>4</jats:sub>, H<jats:sub>2</jats:sub>S, OCS, CH<jats:sub>3</jats:sub>OH, and CH<jats:sub>3</jats:sub>CN on water-ice surfaces using an ultrahigh-vacuum transmission electron microscope. Compiling the measured <jats:italic>E</jats:italic> <jats:sub>sd</jats:sub> values and <jats:italic>E</jats:italic> <jats:sub>des</jats:sub> values from the literature, we find that the value of <jats:italic>f</jats:italic> ranges from ∼0.2 to ∼0.7, depending on the species. Unless <jats:italic>f</jats:italic> (or <jats:italic>E</jats:italic> <jats:sub>sd</jats:sub>) for the majority of species is available, a natural alternative approach for astrochemical models is running multiple simulations, varying <jats:italic>f</jats:italic> for each species randomly. In this approach, ranges of molecular abundances predicted by multiple simulations, rather than abundances predicted by each simulation, are important. We here run 10,000 simulations of astrochemical models of molecular clouds and protostellar envelopes, randomly assigning a value of <jats:italic>f</jats:italic> for each species. In the former case, we identify several key species whose <jats:italic>E</jats:italic> <jats:sub>sd</jats:sub> most strongly affects the uncertainties of the model predictions; <jats:italic>E</jats:italic> <jats:sub>sd</jats:sub> for those species should be investigated in future laboratory and quantum chemical studies. In the latter case, uncertainties in the <jats:italic>E</jats:italic> <jats:sub>sd</jats:sub> of many species contribute to the uncertainties in the model predictions.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The rotation rates of main-sequence stars slow over time as they gradually lose angular momentum to their magnetized stellar winds. The rate of angular momentum loss depends on the strength and morphology of the magnetic field, the mass-loss rate, and the stellar rotation period, mass, and radius. Previous observations suggested a shift in magnetic morphology between two F-type stars with similar rotation rates but very different ages (88 Leo and <jats:italic>ρ</jats:italic> CrB). In this Letter, we identify a comparable transition in an evolutionary sequence of solar analogs with ages between 2–7 Gyr. We present new spectropolarimetry of 18 Sco and 16 Cyg A and B from the Large Binocular Telescope, and we reanalyze previously published Zeeman Doppler images of HD 76151 and 18 Sco, providing additional constraints on the nature and timing of this transition. We combine archival X-ray observations with updated distances from Gaia to estimate mass-loss rates, and we adopt precise stellar properties from asteroseismology and other sources. We then calculate the wind braking torque for each star in the evolutionary sequence, demonstrating that the rate of angular momentum loss drops by more than an order of magnitude between the ages of HD 76151 and 18 Sco (2.6–3.7 Gyr) and continues to decrease modestly to the age of 16 Cyg A and B (7 Gyr). We suggest that this magnetic transition may represent a disruption of the global dynamo arising from weaker differential rotation, and we outline plans to probe this phenomenon in additional stars spanning a wide range of spectral types.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We use time-resolved spectra from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) to examine the distribution of radial velocity (RV) variations in 249 stars identified as members of the Sagittarius (Sgr) dwarf spheroidal (dSph) galaxy by Hayes et al. We select Milky Way (MW) stars that have stellar parameters (<jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}(g)\ $?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mi>g</mml:mi> <mml:mo stretchy="false">)</mml:mo> <mml:mspace width="0.33em" /> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac79afieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, <jats:italic>T</jats:italic> <jats:sub>eff</jats:sub>, and [Fe/H] ) similar to those of the Sagittarius members by means of a k-d tree of dimension 3. We find that the shape of the distribution of RV shifts in Sgr dSph stars is similar to that measured in their MW analogs, but the total fraction of RV variable stars in the Sgr dSph is larger by a factor of ∼2. After ruling out other explanations for this difference, we conclude that the fraction of close binaries in the Sgr dSph is intrinsically higher than in the MW. We discuss the implications of this result for the physical processes leading to the formation of close binaries in dwarf spheroidal and spiral galaxies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present new observations with the Atacama Large Millimeter/submillimeter Array for a gravitationally lensed galaxy at <jats:italic>z</jats:italic> = 9.1, MACS1149-JD1. [O <jats:sc>iii</jats:sc>] 88 <jats:italic>μ</jats:italic>m emission is detected at 10<jats:italic>σ</jats:italic> with a spatial resolution of ∼0.3 kpc in the source plane, enabling the most distant morphokinematic study of a galaxy. The [O <jats:sc>iii</jats:sc>] emission is distributed smoothly without any resolved clumps and shows a clear velocity gradient with Δ<jats:italic>V</jats:italic> <jats:sub>obs</jats:sub>/2<jats:italic>σ</jats:italic> <jats:sub>tot</jats:sub> = 0.84 ± 0.23, where Δ<jats:italic>V</jats:italic> <jats:sub>obs</jats:sub> is the observed maximum velocity difference and <jats:italic>σ</jats:italic> <jats:sub>tot</jats:sub> is the velocity dispersion measured in the spatially integrated line profile, suggesting a rotating system. Assuming a geometrically thin self-gravitating rotation disk model, we obtain <jats:inline-formula> <jats:tex-math> <?CDATA ${V}_{\mathrm{rot}}/{\sigma }_{V}={0.67}_{-0.26}^{+0.73}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>V</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>rot</mml:mi> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:msub> <mml:mrow> <mml:mi>σ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>V</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>0.67</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.26</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.73</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac7447ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, where <jats:italic>V</jats:italic> <jats:sub>rot</jats:sub> and <jats:italic>σ</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub> are the rotation velocity and velocity dispersion, respectively, still consistent with rotation. The resulting disk mass of <jats:inline-formula> <jats:tex-math> <?CDATA ${0.65}_{-0.40}^{+1.37}\times {10}^{9}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>0.65</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.40</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>1.37</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>9</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlac7447ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> is consistent with being associated with the stellar mass identified with a 300 Myr old stellar population independently indicated by a Balmer break in the spectral energy distribution. We conclude that the most of the dynamical mass is associated with the previously identified mature stellar population that formed at <jats:italic>z</jats:italic> ∼ 15.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Short <jats:italic>γ</jats:italic>-ray burst (sGRB) jets form in the aftermath of a neutron star merger, drill through disk winds and dynamical ejecta, and extend over four to five orders of magnitude in distance before breaking out of the ejecta. We present the first 3D general-relativistic magnetohydrodynamic sGRB simulations to span this enormous scale separation. They feature three possible outcomes: jet+cocoon, cocoon, and neither. Typical sGRB jets break out of the dynamical ejecta if (i) the bound ejecta’s isotropic equivalent mass along the pole at the time of the BH formation is ≲10<jats:sup>−4</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, setting a limit on the delay time between the merger and BH formation, otherwise, the jets perish inside the ejecta and leave the jet-inflated cocoon to power a low-luminosity sGRB; (ii) the postmerger remnant disk contains a strong large-scale vertical magnetic field, ≳10<jats:sup>15</jats:sup> G; and (iii) if the jets are weak (≲10<jats:sup>50</jats:sup> erg), the ejecta’s isotropic equivalent mass along the pole must be small (≲10<jats:sup>−2</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>). Generally, the jet structure is shaped by the early interaction with disk winds rather than the dynamical ejecta. As long as our jets break out of the ejecta, they retain a significant magnetization (≲1), suggesting that magnetic reconnection is a fundamental property of sGRB emission. The angular structure of the outflow isotropic equivalent energy after breakout consistently features a flat core followed by a steep power-law distribution (slope ≳3), similar to hydrodynamic jets. In the cocoon-only outcome, the dynamical ejecta broadens the outflow angular distribution and flattens it (slope ∼1.5).</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Close encounters between neutron stars and main-sequence stars occur in globular clusters and may lead to various outcomes. Here we study encounters resulting in the tidal disruption of the star. Using <jats:italic>N</jats:italic>-body models, we predict the typical stellar masses in these disruptions and the dependence of the event rate on the host cluster properties. We find that tidal disruption events occur most frequently in core-collapsed globular clusters and that roughly 25% of the disrupted stars are merger products (i.e., blue straggler stars). Using hydrodynamic simulations, we model the tidal disruptions themselves (over timescales of days) to determine the mass bound to the neutron star and the properties of the accretion disks formed. In general, we find roughly 80%–90% of the initial stellar mass becomes bound to the neutron star following disruption. Additionally, we find that neutron stars receive impulsive kicks of up to about 20 km s<jats:sup>−1</jats:sup> as a result of the asymmetry of unbound ejecta; these kicks place these neutron stars on elongated orbits within their host cluster, with apocenter distances well outside the cluster core. Finally, we model the evolution of the (hypercritical) accretion disks on longer timescales (days to years after disruption) to estimate the accretion rate onto the neutron stars and accompanying spin-up. As long as ≳1% of the bound mass accretes onto the neutron star, millisecond spin periods can be attained. We argue the growing numbers of isolated millisecond pulsars observed in globular clusters may have formed, at least in part, through this mechanism. In the case of significant mass growth, some of these neutron stars may collapse to form low-mass (≲3 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) black holes.</jats:p>