Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We describe the Studying Quenching in Intermediate-<jats:italic>z</jats:italic> Galaxies: Gas, <jats:inline-formula> <jats:tex-math> <?CDATA ${\rm{angu}}\overrightarrow{L}{\rm{ar}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mi mathvariant="normal">angu</mml:mi> </mml:mrow> <mml:mover accent="true"> <mml:mi>L</mml:mi> <mml:mo stretchy="true">→</mml:mo> </mml:mover> <mml:mspace width="-0.25em" /> <mml:mrow> <mml:mi mathvariant="normal">ar</mml:mi> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac404aieqn5.gif" xlink:type="simple" /> </jats:inline-formula> momentum, and Evolution (<jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{SQuIGG}\vec{L}{\rm{E}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>SQuIGG</mml:mi> <mml:mover accent="true"> <mml:mrow> <mml:mi>L</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⃗</mml:mo> </mml:mrow> </mml:mover> <mml:mi mathvariant="normal">E</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac404aieqn6.gif" xlink:type="simple" /> </jats:inline-formula>) survey of intermediate-redshift post-starburst galaxies. We leverage the large sky coverage of the Sloan Digital Sky Survey to select ∼ 1300 recently quenched galaxies at 0.5 &lt; <jats:italic>z</jats:italic> ≤ 0.9 based on their unique spectral shapes. These bright, intermediate-redshift galaxies are ideal laboratories to study the physics responsible for the rapid quenching of star formation: they are distant enough to be useful analogs for high-redshift quenching galaxies, but low enough redshift that multiwavelength follow-up observations are feasible with modest telescope investments. We use the <jats:monospace>Prospector</jats:monospace> code to infer the stellar population properties and nonparametric star formation histories (SFHs) of all galaxies in the sample. We find that <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{SQuIGG}\vec{L}{\rm{E}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>SQuIGG</mml:mi> <mml:mover accent="true"> <mml:mrow> <mml:mi>L</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⃗</mml:mo> </mml:mrow> </mml:mover> <mml:mi mathvariant="normal">E</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac404aieqn7.gif" xlink:type="simple" /> </jats:inline-formula> galaxies are both very massive (<jats:italic>M</jats:italic> <jats:sub>*</jats:sub> ∼ 10<jats:sup>11.25</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) and quenched, with inferred star formation rates ≲1 <jats:italic>M</jats:italic> <jats:sub>⊙ </jats:sub>yr<jats:sup>−1</jats:sup>, more than an order of magnitude below the star-forming main sequence. The best-fit SFHs confirm that these galaxies recently quenched a major burst of star formation: &gt;75% of <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{SQuIGG}\vec{L}{\rm{E}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>SQuIGG</mml:mi> <mml:mover accent="true"> <mml:mrow> <mml:mi>L</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⃗</mml:mo> </mml:mrow> </mml:mover> <mml:mi mathvariant="normal">E</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac404aieqn8.gif" xlink:type="simple" /> </jats:inline-formula> galaxies formed at least a quarter of their total stellar mass in the recent burst, which ended just ∼200 Myr before observation. We find that <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{SQuIGG}\vec{L}{\rm{E}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>SQuIGG</mml:mi> <mml:mover accent="true"> <mml:mrow> <mml:mi>L</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⃗</mml:mo> </mml:mrow> </mml:mover> <mml:mi mathvariant="normal">E</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac404aieqn9.gif" xlink:type="simple" /> </jats:inline-formula> galaxies are on average younger and more burst-dominated than most other <jats:italic>z</jats:italic> ≲ 1 post-starburst galaxy samples. This large sample of bright post-starburst galaxies at intermediate redshift opens a wide range of studies into the quenching process. In particular, the full <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{SQuIGG}\vec{L}{\rm{E}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>SQuIGG</mml:mi> <mml:mover accent="true"> <mml:mrow> <mml:mi>L</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⃗</mml:mo> </mml:mrow> </mml:mover> <mml:mi mathvariant="normal">E</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac404aieqn10.gif" xlink:type="simple" /> </jats:inline-formula> survey will investigate the molecular gas reservoirs, morphologies, kinematics, resolved stellar populations, active galactic nucleus incidence, and infrared properties of this unique sample of galaxies in order to place definitive constraints on the quenching process.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Interstellar dust grains are often aligned. If the grain alignment direction varies along the line of sight, the thermal emission becomes circularly polarized. In the diffuse interstellar medium, the circular polarization at far-infrared and submillimeter wavelengths is predicted to be very small, and probably unmeasurable. However, circular polarization may reach detectable levels in photodissociation regions viewed through molecular clouds, in infrared dark clouds, and in protoplanetary disks. Measurement of circular polarization could help constrain the structure of the magnetic field in infrared dark clouds, and may shed light on the mechanisms responsible for grain alignment in protoplanetary disks.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We observed BL Lac in the <jats:italic>B</jats:italic>, <jats:italic>V</jats:italic>, <jats:italic>R</jats:italic>, and <jats:italic>I</jats:italic> bands with an 85 cm telescope on nine nights from 2019 September 18 to 2019 December 6. More than 2300 data points were collected. All intraday light curves were examined for variations by using the most reliable power-enhanced <jats:italic>F</jats:italic>-test and the ANOVA test, and intraday variability was found on five nights. Thanks to our high precision and high temporal resolution data, two key discoveries were made in the following analyses. (1) In addition to the strong bluer-when-brighter behavior on most nights, we observed a color reversal that is rarely found in BL Lac objects. This indicates that there are two different energy distributions of injected electrons on this night. (2) The object traced clockwise loops on the color–magnitude diagrams on one night. These are the first intraday spectral hysteresis loops reported in the optical bands in this object, suggesting interband time lags. We estimated the interband lags by using the ZDCF, ICCF, and <jats:monospace>JAVELIN</jats:monospace>, and found the variations in the <jats:italic>V</jats:italic> and <jats:italic>R</jats:italic> band lagged that in the <jats:italic>B</jats:italic> band by about 16 and 18 minutes, respectively. Such optical time lags are expected if the acceleration timescale is much shorter than the cooling timescale.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We explore populations of ultra-diffuse galaxies (UDGs) in isolated, satellite, and cluster environments using the R<jats:sc>omulus</jats:sc>25 and R<jats:sc>omulus</jats:sc> C simulations, including how the populations vary with UDG definition and viewing orientation. Using a fiducial definition of UDGs, we find that isolated UDGs have notably larger semimajor (<jats:italic>b</jats:italic>/<jats:italic>a</jats:italic>) and smaller semiminor (<jats:italic>c</jats:italic>/<jats:italic>a</jats:italic>) axis ratios than their non-UDG counterparts, i.e., they are more oblate, or diskier. This is in line with previous results that adopted the same UDG definition and showed that isolated UDGs form via early, high-spin mergers. However, the choice of UDG definition can drastically affect what subsets of a dwarf population are classified as UDGs, changing the number of UDGs by up to ∼45% of the dwarf population. We also find that a galaxy’s classification as a UDG is dependent on its viewing orientation, and this dependence decreases as environmental density increases. Overall, we conclude that some definitions for UDGs used in the literature manage to isolate a specific formation mechanism for isolated dwarfs, while less restrictive definitions erase a link to the formation mechanism. Thus, how we define UDG populations must be considered if we want to understand the formation and evolution of UDGs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Ultraviolet spectra of Comet 96/P Machholz were obtained during its 2002 perihelion with the UltraViolet Coronagraph Spectrometer instrument on board the SOHO satellite. Emission from H <jats:sc>i</jats:sc>, C <jats:sc>ii</jats:sc>, C <jats:sc>iii</jats:sc>, and O <jats:sc>i</jats:sc> is detected near the nucleus. The outgassing rate is in line with the value extrapolated from rates at larger distances from the Sun, and abundances of C and O are estimated. Reconstructed images show a nearly spherical cloud of H <jats:sc>i</jats:sc> Ly<jats:italic>α</jats:italic> emission and an ion tail seen in C <jats:sc>iii</jats:sc>. Radiation pressure on the hydrogen atoms produces a modest distortion of the shape of the Ly<jats:italic>α</jats:italic> cloud as seen from SOHO and Doppler shifts up to 30 km s<jats:sup>−1</jats:sup> in the outer parts of the cloud. We estimate a ratio of C to H<jats:sub>2</jats:sub>O similar to what is observed in other comets, so low carbon abundance does not account for the anomalously low C<jats:sub>2</jats:sub> and C<jats:sub>3</jats:sub> ratios to NH<jats:sub>2</jats:sub> observed at optical wavelengths.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This paper studies cosmic-ray (CR) transport in magnetohydrodynamic (MHD) turbulence. CR transport is strongly dependent on the properties of the magnetic turbulence. We perform test particle simulations to study the interactions of CR with both total MHD turbulence and decomposed MHD modes. The spatial diffusion coefficients and the pitch angle scattering diffusion coefficients are calculated from the test particle trajectories in turbulence. Our results confirm that the fast modes dominate the CR propagation, whereas Alfvén and slow modes are much less efficient and have shown similar pitch-angle scattering rates. We investigate the cross field transport on large and small scales. On large/global scales, normal diffusion is observed and the diffusion coefficient is suppressed by <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{A}^{\zeta }$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>A</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>ζ</mml:mi> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac46c8ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> compared to the parallel diffusion coefficients, with <jats:italic>ζ</jats:italic> closer to 4 in Alfvén modes than that in total turbulence, as theoretically expected. For the CR transport on scales smaller than the turbulence injection scale, both the local and global magnetic reference frames are adopted. Superdiffusion is observed on such small scales in all the cases. Particularly, CR transport in Alfvén modes show clear Richardson diffusion in the <jats:italic>local</jats:italic> reference frame. The diffusion transitions smoothly from the Richardson’s one with index 1.5 to normal diffusion as the particle mean free path decreases from <jats:italic>λ</jats:italic> <jats:sub>∥</jats:sub> ≫ <jats:italic>L</jats:italic> to <jats:italic>λ</jats:italic> <jats:sub>∥</jats:sub> ≪ <jats:italic>L</jats:italic>, where <jats:italic>L</jats:italic> is the injection/coherence length of turbulence. Our results have broad applications to CRs in various astrophysical environments.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The production site of gamma rays in blazars is closely related to their interaction with the photon fields surrounding the active galactic nucleus. In this paper, we discuss an indirect method that may help to unveil the presence of ambient structures in BL Lac objects through the analysis of their gamma-ray spectrum. Gamma rays, passing through structures at different distances from the black hole, interact via <jats:italic>γ</jats:italic> <jats:italic>γ</jats:italic> pair production with the corresponding photon fields and produce absorption features in their spectral energy distribution. An interaction with a putative broad-line region may reduce the gamma-ray flux only if its production site were very close to the central engine. However, if jet photons interact with a bath of optical-UV seed photons produced by a narrow-line region extended over the parsec scale, the consequent <jats:italic>γ</jats:italic> <jats:italic>γ</jats:italic> process may cause absorption features detectable at a few hundreds of GeV. The detection of such absorption features is facilitated in sources with spectra reaching TeV energies, and specifically HBLs and EHBLs (extreme blazars) may represent exceptional probes to investigate this topic. We discuss recent observations of an extreme blazar named 2WHSP J073326.7+515354 (or PGC 2402248), which shows evidence of such an absorption feature in its gamma-ray spectrum and narrow emission lines in the optical spectrum, suggesting the presence of narrow-line regions in its large-scale environment. Finally, we discuss how sub-TeV absorption features in the spectra of BL Lac objects may affect their broadband modeling and eventually represent a powerful diagnostic tool to constrain the gamma-ray production site and the jet environment.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>CO(2–1) emission is often used as a tracer of giant molecular clouds (GMCs) as an alternative to CO(1–0) emission in recent years. Therefore, understanding the environmental dependence of the line ratio of CO(2–1)/CO(1–0), <jats:italic>R</jats:italic> <jats:sub>21</jats:sub>, on the GMC scale is important to accurately estimate the mass of GMCs. We thus measured <jats:italic>R</jats:italic> <jats:sub>21</jats:sub> in the strongly barred galaxy NGC 1300, where star formation activity strongly depends on galactic structure, on a ∼100 pc scale. CO images were obtained from the Atacama Large Millimeter/submillimeter Array and the Nobeyama 45 m telescope. The resultant typical <jats:italic>R</jats:italic> <jats:sub>21</jats:sub> in NGC 1300 is 0.57 ± 0.06. We find environmental variations in <jats:italic>R</jats:italic> <jats:sub>21</jats:sub>: it is the highest in the bar-end region (0.72 ± 0.08), followed by arm (0.60 ± 0.07) and bar regions (0.50 ± 0.06). GMCs with H<jats:italic>α</jats:italic> emission show a systematically higher ratio (0.67 ± 0.07) than those without H<jats:italic>α</jats:italic> (0.47 ± 0.05). In the bar region, where massive star formation is suppressed, H<jats:italic>α</jats:italic> emission is not associated with most GMCs, resulting in the lowest <jats:italic>R</jats:italic> <jats:sub>21</jats:sub>. These results raise a possibility that properties of GMCs derived from CO(2–1) observations with the assumption of a constant <jats:italic>R</jats:italic> <jats:sub>21</jats:sub> are different from those derived from CO(1–0) observations. Furthermore, we find the <jats:italic>R</jats:italic> <jats:sub>21</jats:sub> measured on the kiloparsec scale tends to be lower than that of the GMCs, probably due to the presence of an extended diffuse molecular gas in NGC 1300.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Using two-dimensional MHD simulations in different Lundquist numbers <jats:italic>S</jats:italic>, we investigate physical regimes of turbulent reconnection and the role of turbulence in enhancing the reconnection rate. Turbulence is externally injected into the system with varying strength. Externally driven turbulence contributes to the conversion of magnetic energy to kinetic energy flowing out of the reconnection site and thus enhances the reconnection rate. The plasmoids formed in high Lundquist numbers contribute to the fast reconnection rate, as well. Moreover, an analysis of the power of turbulence implies its possible association with the generation of plasmoids. Additionally, the presence of turbulence has great impact on the magnetic energy conversion and may be impactful also for the Kelvin–Helmholtz instability in the magnetic reconnection process.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Using ultraviolet (UV) light curves, we constrain the circumstellar environments of 1080 Type Ia supernovae (SNe Ia) within <jats:italic>z</jats:italic> &lt; 0.5 from archival Galaxy Evolution Explorer (GALEX) observations. All SNe Ia are required to have pre- and post-explosion GALEX observations to ensure adequate subtraction of the host-galaxy flux. Using the late-time GALEX observations, we look for the UV excess expected from any interaction between the SN ejecta and circumstellar material (CSM). Four SNe Ia are detected near maximum light, and we compare the GALEX photometry to archival data. However, we find that none of our targets show convincing evidence of CSM interaction. A recent Hubble Space Telescope (HST) survey estimates that ∼6% of SNe Ia may interact with distant CSM, but statistical inferences are complicated by the small sample size and selection effects. By injecting model light curves into our data and then recovering them, we constrain a broad range of CSM interactions based on the CSM interaction start time and the maximum luminosity. Combining our GALEX nondetections with the HST results, we constrain occurrence of late-onset CSM interaction among SNe Ia with moderate CSM interaction, similar to that observed in PTF11kx, to <jats:italic>f</jats:italic> <jats:sub>CSM</jats:sub> ≲ 5.1% between 0 and 500 days after discovery and ≲2.7% between 500 and 1000 days after discovery at 90% confidence. For weaker CSM interactions similar to SN 2015cp, we obtain limits of ≲16% and ≲4.8%, respectively, for the same time ranges.</jats:p>