Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We report the results of analyses of galactic outflows in a sample of 45 low-redshift starburst galaxies in the COS Legacy Archive Spectroscopic SurveY (CLASSY), augmented by five additional similar starbursts with Cosmic Origins Spectrograph (COS) data. The outflows are traced by blueshifted absorption lines of metals spanning a wide range of ionization potential. The high quality and broad spectral coverage of CLASSY data enable us to disentangle the absorption due to the static interstellar medium (ISM) from that due to outflows. We further use different line multiplets and doublets to determine the covering fraction, column density, and ionization state as a function of velocity for each outflow. We measure the outflow’s mean velocity and velocity width, and find that both correlate in a highly significant way with the star formation rate, galaxy mass, and circular velocity over ranges of four orders of magnitude for the first two properties. We also estimate outflow rates of metals, mass, momentum, and kinetic energy. We find that, at most, only about 20% of silicon created and ejected by supernovae in the starburst is carried out in the warm phase we observe. The outflows’ mass-loading factor increases steeply and inversely with both circular and outflow velocity (log–log slope ∼−1.6), and reaches ∼10 for dwarf galaxies. We find that the outflows typically carry about 10%–100% of the momentum injected by massive stars and about 1%–20% of the kinetic energy. We show that these results place interesting constraints on, and new insights into, models and simulations of galactic winds.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The extragalactic background light (EBL) contains all the radiation emitted by nuclear and accretion processes in stars and compact objects since the epoch of recombination. Measuring the EBL density directly is challenging, especially in the near-to-far-infrared wave band, mainly due to the zodiacal light foreground. Instead, gamma-ray astronomy offers the possibility to indirectly set limits on the EBL by studying the effects of gamma-ray absorption in the very high energy (VHE: &gt;100 GeV) spectra of distant blazars. The High Altitude Water Cherenkov Gamma Ray Observatory (HAWC) is one of the few instruments sensitive to gamma rays with energies above 10 TeV. This offers the opportunity to probe the EBL in the near/mid-IR region: <jats:italic>λ</jats:italic> = 1–100 <jats:italic>μ</jats:italic>m. In this study, we fit physically motivated emission models to Fermi-LAT gigaelectronvolt data to extrapolate the intrinsic teraelectronvolt spectra of blazars. We then simulate a large number of absorbed spectra for different randomly generated EBL model shapes and calculate Bayesian credible bands in the EBL intensity space by comparing and testing the agreement between the absorbed spectra and HAWC extragalactic observations of two blazars. The resulting bands are in agreement with current EBL lower and upper limits, showing a downward trend toward higher wavelength values <jats:italic>λ</jats:italic> &gt; 10 <jats:italic>μ</jats:italic>m also observed in previous measurements.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The BL Lac object PKS 0735+178 has shown some complex multiwavelength variation phenomena in previous studies, especially in its color behavior. Bluer-when-brighter, redder-when-brighter, and achromatic behavior were all found to be possible long-term trends of PKS 0735+178. In this work, we collected long-term multiwavelength data on PKS 0735+178, and also performed a multicolor optical monitoring on intraday timescales. Intraday variability was detected on one night. On long timescales, a possible 22 day time lag was found between the <jats:italic>R</jats:italic> and <jats:italic>γ</jats:italic>-ray bands. The results of a cross-correlation analysis exhibited strong correlations between various optical bands on both intraday and long timescales. However, only a mild correlation was found between the long-term <jats:italic>γ</jats:italic>-ray and <jats:italic>R</jats:italic>-band light curves, which could be interpreted as different emission mechanisms for the <jats:italic>γ</jats:italic>-ray and optical emissions. PKS 0735+178 showed a significant harder-when-brighter (HWB) behavior in the <jats:italic>γ</jats:italic>-ray band, which is consistent with the observed optical bluer-when-brighter (BWB) trend on both long-term and intraday timescales. We found that the HWB and BWB trends will be enhanced during active states, especially for the historical low state. Such a phenomenon indicates a special activity-dependent color behavior of PKS 0735+178, and it could be well interpreted by the jet emission model.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Quasi-periodic eruptions (QPEs) are found in the center of five galaxies, where a tidal disruption event (TDE)-like event has been reported in GSN 069, which occurred a couple of years before the QPEs. We explain the connection of these phenomena based on a model of a highly eccentric white dwarf (WD) 10<jats:sup>4−6</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> massive black hole (MBH) binary formed by the Hill mechanism. In this system, the tidally induced internal oscillation of a WD can heat the WD envelope thereby inducing tidal nova and inflating the WD envelope, which can be captured by the MBH and form a TDE. The tidal stripping of the surviving WD in the eccentric orbit can produce QPEs. We also apply this model to the other four QPE sources. Based on the estimated fallback rate, we find that the remaining time after the QPE-observed time for these QPEs is only around 1–2 yr based on our simple model estimation, after which the WD will be fully disrupted. We also show that the accretion rate can be much higher than the Eddington accretion rate in the final stage of these QPE sources. The peak frequency of the spectral energy distribution of the disk stays in the soft X-ray band (∼0.1–1 keV), which is consistent with observational results.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report on a new capability added to our general relativistic radiation-magnetohydrodynamics code, <jats:italic>Cosmos++</jats:italic>: an implicit Monte Carlo (IMC) treatment for radiation transport. The method is based on a Fleck-type implicit discretization of the radiation-hydrodynamics equations, but generalized for both Newtonian and relativistic regimes. A multiple reference frame approach is used to geodesically transport photon packets (and solve the hydrodynamics equations) in the coordinate frame, while radiation–matter interactions are handled either in the fluid or electron frames then communicated via Lorentz boosts and orthonormal tetrad bases attached to the fluid. We describe a method for constructing estimators of radiation moments using path-weighting that generalizes to arbitrary coordinate systems in flat or curved spacetime. Absorption, emission, scattering, and relativistic Comptonization are among the matter interactions considered in this report. We discuss our formulations and numerical methods, and validate our models against a suite of radiation and coupled radiation-hydrodynamics test problems in both flat and curved spacetimes.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Here we present an ensemble study of spin–orbit alignment in 43 close double star systems. We determine spin–orbit angles, obliquities, in 31 of these systems making use of recently improved apsidal motion rate measurements and apsidal motion constants. In the remaining 12 systems researchers have constrained spin–orbit alignment by different combinations of measurements of apsidal motion rates, projected obliquities, and stellar inclinations. Of the 43 systems 40 are consistent with alignment albeit with some measurements having large uncertainties. A Fisher distribution with mean zero and a concentration factor <jats:italic>κ</jats:italic> = 6.1 represents this ensemble well. Indeed employing a bootstrapping resampling technique we find our data on these 40 systems are consistent with perfect alignment. We also confirm significant misalignment in two systems that travel on eccentric orbits and where misalignments have been reported on before; namely DI Her and AS Cam. The third misaligned system CV Vel orbits on a circular orbit. So while there are some glaring exceptions, the majority of close double star systems for which data are available appear to be well aligned.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a study of the size–mass relation for local post-starburst (PSB) galaxies at <jats:italic>z</jats:italic> ≲ 0.33 selected from the Sloan Digital Sky Survey Data Release 8. We find that PSB galaxies with stellar mass (<jats:italic>M</jats:italic> <jats:sub>*</jats:sub>) at 10<jats:sup>9</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>12</jats:sup> <jats:italic>M</jats:italic> <jats:sub>☉</jats:sub> have a galaxy size smaller than or comparable to those of quiescent galaxies (QGs). After controlling redshift and stellar mass, the sizes of PSBs are ∼13% smaller on average than those of QGs; such differences become larger and significant toward the low-<jats:italic>M</jats:italic> <jats:sub>*</jats:sub> end, especially at 10<jats:sup>9.5</jats:sup> <jats:italic>M</jats:italic> <jats:sub>☉</jats:sub> ≲ <jats:italic>M</jats:italic> <jats:sub>*</jats:sub> ≲ 10<jats:sup>10.5</jats:sup> <jats:italic>M</jats:italic> <jats:sub>☉</jats:sub> where PSBs can be on average ∼19% smaller than QGs. By comparing predictions of possible PSB evolutionary pathways from cosmological simulations, we suggest that a fast quenching of star formation following a short-lived starburst event (which might be induced by a major merger) should be the dominant pathway of our PSB sample. Furthermore, by cross-matching with group catalogs, we confirm that local PSBs at <jats:italic>M</jats:italic> <jats:sub>*</jats:sub> ≲ 10<jats:sup>10</jats:sup> <jats:italic>M</jats:italic> <jats:sub>☉</jats:sub> are more clustered than more massive ones. PSBs residing in groups are found to be slightly larger in galaxy size and more disk-like compared to field PSBs, which is qualitatively consistent with and thus hints at the environment-driven fast quenching pathway for group PSBs. Taken together, our results support multiple evolutionary pathways for local PSB galaxies: while massive PSBs are thought of as products of fast quenching following a major merger-induced starburst, environment-induced fast quenching should play a role in the evolution of less massive PSBs, especially at <jats:italic>M</jats:italic> <jats:sub>*</jats:sub> ≲ 10<jats:sup>10</jats:sup> <jats:italic>M</jats:italic> <jats:sub>☉</jats:sub>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We built the first-ever statistically significant sample of ≈80,000 background quasar–foreground cluster pairs to study the cool, metal-rich gas in the outskirts (&gt;<jats:italic>R</jats:italic> <jats:sub>500</jats:sub>) of <jats:italic>z</jats:italic> ≈ 0.5 clusters with a median mass of ≈10<jats:sup>14.2</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. The sample was obtained by crossmatching the Sloan Digital Sky Survey (SDSS) cluster catalog of Wen &amp; Han and the SDSS quasar catalog of Lyke et al. The median impact parameter (<jats:italic>ρ</jats:italic> <jats:sub>cl</jats:sub>) of the clusters from the quasar sightlines is 2.4 Mpc (median <jats:italic>ρ</jats:italic> <jats:sub>cl</jats:sub>/<jats:italic>R</jats:italic> <jats:sub>500</jats:sub> = 3.6). A strong Mg <jats:sc>II</jats:sc>, along with marginal Fe <jats:sc>II</jats:sc>, absorption is detected in the mean and median stacked spectra of the quasars with a total Mg <jats:sc>II</jats:sc> rest-frame equivalent width (<jats:inline-formula> <jats:tex-math> <?CDATA ${W}_{r}^{2796+2803}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi>W</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>r</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2796</mml:mn> <mml:mo>+</mml:mo> <mml:mn>2803</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac7155ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>) of 0.034 ± 0.005 Å (7<jats:italic>σ</jats:italic>) and 0.010 ± 0.003 Å (3<jats:italic>σ</jats:italic>), respectively. The <jats:inline-formula> <jats:tex-math> <?CDATA ${W}_{r}^{2796+2803}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi>W</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>r</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2796</mml:mn> <mml:mo>+</mml:mo> <mml:mn>2803</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac7155ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> shows a declining trend with increasing <jats:italic>ρ</jats:italic> <jats:sub>cl</jats:sub> and <jats:italic>ρ</jats:italic> <jats:sub>cl</jats:sub>/<jats:italic>R</jats:italic> <jats:sub>500</jats:sub>, but does not show any significant trend with mass (<jats:italic>M</jats:italic> <jats:sub>500</jats:sub>) or redshift (<jats:italic>z</jats:italic> <jats:sub>cl</jats:sub>) within the small <jats:italic>M</jats:italic> <jats:sub>500</jats:sub> and <jats:italic>z</jats:italic> <jats:sub>cl</jats:sub> ranges probed here. The Mg <jats:sc>II</jats:sc> absorption signal and the trends persist even if we exclude the quasar–cluster pairs where the background quasars may be probing the circumgalactic medium of bright galaxies with impact parameters &lt;300 kpc. The Mg <jats:sc>II</jats:sc> (and Fe <jats:sc>II</jats:sc>) absorption reported here is the first detection of its kind. It indicates the presence of a cool, metal-rich gas reservoir surrounding galaxy clusters out to several <jats:italic>R</jats:italic> <jats:sub>500</jats:sub>. We suggest that the metal-rich gas in the cluster outskirts arise from stripped materials and that gas stripping may be important out to large clustocentric distances (&gt;3<jats:italic>R</jats:italic> <jats:sub>500</jats:sub>).</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Titan’s atmosphere is a natural laboratory for exploring the photochemical synthesis of organic molecules. Significant recent advances in the study of the atmosphere of Titan include: (a) detection of C<jats:sub>3</jats:sub> molecules: C<jats:sub>3</jats:sub>H<jats:sub>6</jats:sub>, CH<jats:sub>2</jats:sub>CCH<jats:sub>2</jats:sub>, c-C<jats:sub>3</jats:sub>H<jats:sub>2</jats:sub>, and (b) retrieval of C<jats:sub>6</jats:sub>H<jats:sub>6</jats:sub>, which is formed primarily via C<jats:sub>3</jats:sub> chemistry, from Cassini Ultraviolet Imaging Spectrograph data. The detection of <jats:italic>c</jats:italic>-C<jats:sub>3</jats:sub>H<jats:sub>2</jats:sub> is of particular significance as ring molecules are of great astrobiological importance. Using the Caltech/JPL KINETICS code, along with the best available photochemical rate coefficients and parameterized vertical transport, we are able to account for the recent observations. It is significant that ion chemistry, reminiscent of that in the interstellar medium, plays a major role in the production of c-C<jats:sub>3</jats:sub>H<jats:sub>2</jats:sub> above 1000 km.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The pulsed radio emission of rotating neutron stars is connected to slow tearing instabilities feeding off an inhomogeneous twist profile within the open circuit. This paper considers the stability of a weakly sheared, quantizing magnetic field in which the current is supported by a relativistic particle flow. The electromagnetic field is almost perfectly force free, and particles are confined to the lowest Landau state, experiencing no appreciable curvature drift. In a charge-neutral plasma, we find multiple branches of slowly growing tearing modes, relativistic analogs of the double-tearing mode, with peak growth rate <jats:inline-formula> <jats:tex-math> <?CDATA $s\gtrsim 4\pi {\widetilde{k}}_{y}{J}_{z}/{B}_{z}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>s</mml:mi> <mml:mo>≳</mml:mo> <mml:mn>4</mml:mn> <mml:mi>π</mml:mi> <mml:msub> <mml:mrow> <mml:mover accent="true"> <mml:mrow> <mml:mi>k</mml:mi> </mml:mrow> <mml:mrow> <mml:mo stretchy="true">˜</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mi>y</mml:mi> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi>J</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>z</mml:mi> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:msub> <mml:mrow> <mml:mi>B</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>z</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac501fieqn1.gif" xlink:type="simple" /> </jats:inline-formula>. Here, <jats:italic>B</jats:italic> <jats:sub> <jats:italic>z</jats:italic> </jats:sub> is the strong (nearly potential) guide magnetic field, <jats:italic>J</jats:italic> <jats:sub> <jats:italic>z</jats:italic> </jats:sub> the field-aligned current density, and <jats:inline-formula> <jats:tex-math> <?CDATA ${\widetilde{k}}_{y}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mover accent="true"> <mml:mrow> <mml:mi>k</mml:mi> </mml:mrow> <mml:mrow> <mml:mo stretchy="true">˜</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mi>y</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac501fieqn2.gif" xlink:type="simple" /> </jats:inline-formula> is the mode wavenumber normalized by the current gradient scale. These modes are overstable when the plasma carries a net charge, with the real frequency <jats:inline-formula> <jats:tex-math> <?CDATA $\omega \sim s\cdot | {n}_{0}^{+}-{n}_{0}^{-}| /({n}_{0}^{+}+{n}_{0}^{-})$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>ω</mml:mi> <mml:mo>∼</mml:mo> <mml:mi>s</mml:mi> <mml:mo>·</mml:mo> <mml:mo stretchy="false">∣</mml:mo> <mml:msubsup> <mml:mrow> <mml:mi>n</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> </mml:mrow> </mml:msubsup> <mml:mo>−</mml:mo> <mml:msubsup> <mml:mrow> <mml:mi>n</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> </mml:mrow> </mml:msubsup> <mml:mo stretchy="false">∣</mml:mo> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mo stretchy="false">(</mml:mo> <mml:msubsup> <mml:mrow> <mml:mi>n</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> </mml:mrow> </mml:msubsup> <mml:mo>+</mml:mo> <mml:msubsup> <mml:mrow> <mml:mi>n</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> </mml:mrow> </mml:msubsup> <mml:mo stretchy="false">)</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac501fieqn3.gif" xlink:type="simple" /> </jats:inline-formula> proportional to the imbalance in the densities of positive and negative charges. An isolated current sheet thinner than the skin depth supports localized tearing modes with growth rate scaling as (sheet thickness/skin depth)<jats:sup>−1/2</jats:sup>. In a pulsar, the peak growth rate is comparable to the angular frequency of rotation, <jats:inline-formula> <jats:tex-math> <?CDATA $s\gtrsim 2{\widetilde{k}}_{y}{\rm{\Omega }}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>s</mml:mi> <mml:mo>≳</mml:mo> <mml:mn>2</mml:mn> <mml:msub> <mml:mrow> <mml:mover accent="true"> <mml:mrow> <mml:mi>k</mml:mi> </mml:mrow> <mml:mrow> <mml:mo stretchy="true">˜</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mi>y</mml:mi> </mml:mrow> </mml:msub> <mml:mi mathvariant="normal">Ω</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac501fieqn4.gif" xlink:type="simple" /> </jats:inline-formula>, slow compared with the longitudinal oscillations of particles and fields in a polar gap. The tearing modes experience azimuthal drift reminiscent of subpulse drift and are a promising driver of pulse-to-pulse flux variations. A companion paper demonstrates a Cerenkov-like instability of current-carrying Alfvén waves in thin current sheets with relativistic particle flow and proposes coherent curvature emission by these waves as a source of pulsar radio emission.</jats:p>