Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>3FGL J1544.6−1125 is a candidate transitional millisecond pulsar (tMSP). Similar to the well-established tMSPs—PSR J1023+0038, IGR J18245−2452, and XSS J12270−4859—3FGL J1544.6−1125 shows <jats:italic>γ</jats:italic>-ray emission and discrete X-ray “low” and “high” modes during its low-luminosity accretion-disk state. Coordinated radio/X-ray observations of PSR J1023+0038 in its current low-luminosity accretion-disk state showed rapidly variable radio continuum emission—possibly originating from a compact, self-absorbed jet, the “propellering” of accretion material, and/or pulsar moding. 3FGL J1544.6−1125 is currently the only other (candidate) tMSP system in this state, and can be studied to see whether tMSPs are typically radio-loud compared to other neutron star binaries. In this work, we present a quasi-simultaneous Very Large Array and Swift radio/X-ray campaign on 3FGL J1544.6−1125. We detect 10 GHz radio emission varying in flux density from 47.7 ± 6.0 <jats:italic>μ</jats:italic>Jy down to ≲15 <jats:italic>μ</jats:italic>Jy (3<jats:italic>σ</jats:italic> upper limit) at four epochs spanning three weeks. At the brightest epoch, the radio luminosity is <jats:italic>L</jats:italic> <jats:sub>5 GHz</jats:sub> = (2.17 ± 0.17) × 10<jats:sup>27</jats:sup> erg s<jats:sup>−1</jats:sup> for a quasi-simultaneous X-ray luminosity <jats:italic>L</jats:italic> <jats:sub>2–10 keV</jats:sub> = (4.32 ± 0.23) × 10<jats:sup>33</jats:sup> erg s<jats:sup>−1</jats:sup> (for an assumed distance of 3.8 kpc). These luminosities are close to those of PSR J1023+0038, and the results strengthen the case that 3FGL J1544.6−1125 is a tMSP showing similar phenomenology to PSR J1023+0038.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The measurements from the Mars Atmosphere and Volatile EvolutioN spacecraft, in orbit around Mars, are utilized to investigate interplanetary coronal mass ejections (ICMEs) near 1.52 au. We identify 24 ICMEs from 2014 December 6 to 2019 February 21. The ICME list is used to examine the statistical properties of ICMEs. On average, the magnetic field strength of 5.99 nT in ICMEs is higher than that of 5.38 nT for stream interaction regions (SIRs). The density of 5.27 cm<jats:sup>−3</jats:sup> for ICMEs is quite comparable to that of 5.17 cm<jats:sup>−3</jats:sup> for SIRs, the velocity of 394.7 km s<jats:sup>−1</jats:sup> for ICMEs is slightly lower than that of 432.8 km s<jats:sup>−1</jats:sup> for SIRs, and the corresponding dynamic pressure of 1.34 nPa for ICMEs is smaller than that of 1.50 nPa for SIRs. Using existing databases of ICMEs at 1 au for the same time period, we compare ICME average properties at 1.52 au with those at 1 au. The averages of the characteristic quantities decrease by a factor of 1.1–1.7 from 1 to 1.52 au. In addition, we analyze an unusual space weather event associated with the ICME on 2015 March 9–10, and propose that the extremely strong dynamic pressure with a maximum of ∼18 nPa on March 8 is caused by the combined effects of the enhanced density inside a heliospheric plasma sheet (HPS), the compression of the HPS by the forward shock, and the high velocity of the sheath ahead of the ICME.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present new Atacama Large Millimeter/submillimeter Array Band 7 observational results of a Lyman-break galaxy at <jats:italic>z</jats:italic> = 7.15, B14-65666 (“Big Three Dragons”), which is an object detected in [O <jats:sc>iii</jats:sc>] 88 <jats:italic>μ</jats:italic>m, [C <jats:sc>ii</jats:sc>] 158 <jats:italic>μ</jats:italic>m, and dust continuum emission during the epoch of reionization. Our targets are the [N <jats:sc>ii</jats:sc>] 122 <jats:italic>μ</jats:italic>m fine-structure emission line and the underlying 120 <jats:italic>μ</jats:italic>m dust continuum. The dust continuum is detected with a ∼19<jats:italic>σ</jats:italic> significance. From far-infrared spectral energy distribution sampled at 90, 120, and 160 <jats:italic>μ</jats:italic>m, we obtain a best-fit dust temperature of 40 K (79 K) and an infrared luminosity of <jats:inline-formula> <jats:tex-math> <?CDATA ${\mathrm{log}}_{10}({L}_{\mathrm{IR}}/{L}_{\odot })=11.6$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>log</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> </mml:msub> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>L</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>IR</mml:mi> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:msub> <mml:mrow> <mml:mi>L</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> <mml:mo>=</mml:mo> <mml:mn>11.6</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac2a36ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> (12.1) at the emissivity index <jats:italic>β</jats:italic> = 2.0 (1.0). The [N <jats:sc>ii</jats:sc>] 122 <jats:italic>μ</jats:italic>m line is not detected. The 3<jats:italic>σ</jats:italic> upper limit of the [N <jats:sc>ii</jats:sc>] luminosity is 8.1 × 10<jats:sup>7</jats:sup> <jats:italic>L</jats:italic> <jats:sub>⊙</jats:sub>. From the [N <jats:sc>ii</jats:sc>], [O <jats:sc>iii</jats:sc>], and [C <jats:sc>ii</jats:sc>] line luminosities, we use the Cloudy photoionization code to estimate nebular parameters as functions of metallicity. If the metallicity of the galaxy is high (<jats:italic>Z</jats:italic> &gt; 0.4 <jats:italic>Z</jats:italic> <jats:sub>⊙</jats:sub>), the ionization parameter and hydrogen density are <jats:inline-formula> <jats:tex-math> <?CDATA ${\mathrm{log}}_{10}U\simeq -2.7\pm 0.1$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>log</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> </mml:msub> <mml:mi>U</mml:mi> <mml:mo>≃</mml:mo> <mml:mo>−</mml:mo> <mml:mn>2.7</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.1</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac2a36ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> and <jats:italic>n</jats:italic> <jats:sub>H</jats:sub> ≃ 50–250 cm<jats:sup>−3</jats:sup>, respectively, which are comparable to those measured in low-redshift galaxies. The nitrogen-to-oxygen abundance ratio, N/O, is constrained to be subsolar. At <jats:italic>Z</jats:italic> &lt; 0.4 <jats:italic>Z</jats:italic> <jats:sub>⊙</jats:sub>, the allowed <jats:italic>U</jats:italic> drastically increases as the assumed metallicity decreases. For high ionization parameters, the N/O constraint becomes weak. Finally, our Cloudy models predict the location of B14-65666 on the BPT diagram, thereby allowing a comparison with low-redshift galaxies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The role of active galactic nuclei (AGNs) during galaxy interactions and how they influence the star formation in the system are still under debate. We use a sample of 1156 galaxies in galaxy pairs or mergers (hereafter “pairs”) from the MaNGA survey. This pair sample is selected by the velocity offset, projected separation, and morphology, and is further classified into four cases along the merger sequence based on morphological signatures. We then identify a total of 61 (5.5%) AGNs in pairs based on the emission-line diagnostics. No evolution of the AGN fraction is found, either along the merger sequence or compared to isolated galaxies (5.0%). We observe a higher fraction of passive galaxies in galaxy pairs, especially in the pre-merging cases, and associate the higher fraction to their environmental dependence. The isolated AGN and AGNs in pairs show similar distributions in their global stellar mass, star-formation rate (SFR), and central [O <jats:sc>iii</jats:sc>] surface brightness. AGNs in pairs show radial profiles of increasing specific SFR and declining Dn4000 from center to outskirts, and no significant difference from the isolated AGNs. This is clearly different from star-forming galaxies (SFGs) in our pair sample, which show enhanced central star formation, as reported before. AGNs in pairs have lower Balmer decrements at outer regions, possibly indicating less dust attenuation. Our findings suggest that AGNs are likely follow an inside-out quenching and the merger impact on the star formation in AGNs is less prominent than in SFGs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Optical observations of a sample of 12 <jats:italic>γ</jats:italic>-ray-bright blazars from four optical data archives—American Association of Variable Star Observers, Small and Moderate Aperture Research Telescope System, Catalina, and Steward Observatory—are compiled to create densely sampled light curves spanning more than a decade. As a part of the blazar multiwavelength studies, several methods of analysis, e.g., flux distribution and rms–flux relation, are performed on the observations with the aim to compare the results with the similar ones in the <jats:italic>γ</jats:italic>-ray band presented in Bhatta &amp; Dhital. It is found that, similar to the <jats:italic>γ</jats:italic>-ray band, blazars display significant variability in the optical band that can be characterized with lognormal flux distribution and a power-law dependence of rms on flux. It could be an indication of a possible inherent linear rms–flux relation, yet the scatter in the data does not allow to rule out other possibilities. When comparing variability properties in the two bands, the blazars in the <jats:italic>γ</jats:italic>-rays are found to exhibit stronger variability with a steeper possible linear rms–flux relation and a flux distribution that is more skewed toward higher fluxes. The cross-correlation study shows that except for source 3C 273, the overall optical and the <jats:italic>γ</jats:italic>-ray emission in the sources are highly correlated, suggesting a cospatial existence of the particles responsible for both the optical and <jats:italic>γ</jats:italic>-ray emission. Moreover, sources S5 0716+714, Mrk 421, Mrk 501, PKS 1424-418, and PKS 2155-304 revealed possible evidence of quasiperiodic oscillations in the optical emission with the characteristic timescales, which are comparable to those in the <jats:italic>γ</jats:italic>-ray band detected in our previous work.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>One of the primary goals for the upcoming James Webb Space Telescope is to observe the first galaxies. Predictions for planned and proposed surveys have typically focused on average galaxy counts, assuming a random distribution of galaxies across the observed field. The first and most-massive galaxies, however, are expected to be tightly clustered, an effect known as cosmic variance. We show that cosmic variance is likely to be the dominant contribution to uncertainty for high-redshift mass and luminosity functions, and that median high-redshift and high-mass galaxy counts for planned observations lie significantly below average counts. Several different strategies are considered for improving our understanding of the first galaxies, including adding depth, area, and independent pointings. Adding independent pointings is shown to be the most efficient both for discovering the single highest-redshift galaxy and also for constraining mass and luminosity functions.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Ultra-diffuse galaxies (UDGs) are very-low-surface-brightness galaxies with large effective radii. Spectroscopic measurements of a few UDGs have revealed a low dark-matter content based on the internal motion of stars or globular clusters (GCs). This is in contrast to the large number of GCs found for these systems, from which it would be expected to correspond to a large dark-matter halo mass. Here we present HST+ACS observations for the UDG MATLAS-2019 in the NGC 5846 group. Using the <jats:italic>F</jats:italic>606<jats:italic>W</jats:italic> and <jats:italic>F</jats:italic>814<jats:italic>W</jats:italic> filters, we trace the GC population two magnitudes below the peak of the GC luminosity function (GCLF). Employing Bayesian considerations, we identify 26 ± 6 GCs associated with the dwarf, yielding a large specific frequency of <jats:italic>S</jats:italic> <jats:sub> <jats:italic>N</jats:italic> </jats:sub> = 58 ± 14. We use the turnover of the GCLF to derive a distance of 21 ± 2 Mpc, which is consistent with the NGC 5846 group of galaxies. Due to the superior image quality of the HST, we are able to resolve the GCs and measure their sizes, which are consistent with the sizes of GCs around Local Group galaxies. Using the linear relation between the total mass of galaxies and of GCs, we derive a halo mass of 0.9 ± 0.2 × 10<jats:sup>11</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> (<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>/<jats:italic>L</jats:italic> <jats:sub>⊙</jats:sub> &gt; 1000). The high abundance of GCs, together with the small uncertainties, make MATLAS-2019 one of the most extreme UDGs, which likely sets an upper limit of the number of GCs for UDGs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The large, faint H<jats:italic>α</jats:italic> emission surrounding the early B-star binary Spica has been used to constrain the total hydrogen recombination rate of the nebula and indirectly probe the Lyman continuum luminosity of the primary star. Early analysis suggested that a stellar atmosphere model, consistent with Spica A’s spectral type, has a Lyman continuum luminosity about two times lower than required to account for the measured H<jats:italic>α</jats:italic> surface brightness within the nebula. To more consistently model both the stellar and nebular emission, we have used a model atmosphere for Spica A that includes the effects of gravity darkening as input to photoionization models to produce synthetic H<jats:italic>α</jats:italic> surface brightness distributions for comparison to data from the Southern H<jats:italic>α</jats:italic> Sky Survey Atlas. This paper presents a method for the computation of projected surface brightness profiles from 1D volume emissivity models and constrains both stellar and nebular parameters. A mean effective temperature for Spica A of ≃24,800 K is sufficient to match both the observed absolute spectrophotometry, from the far-UV to the near-IR, and radial H<jats:italic>α</jats:italic> surface brightness distributions. Model hydrogen densities increase with the distance from the star, more steeply and linearly toward the southeast. The northwest matter-bounded portion of the nebula is predicted to leak ∼17% of Lyman continuum photons. Model H <jats:sc>ii</jats:sc> region column densities are consistent with archival observations along the line of sight.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present spatially resolved stellar kinematics for 797 <jats:italic>z</jats:italic> = 0.6–1 galaxies selected from the LEGA-C survey and construct axisymmetric Jeans models to quantify their dynamical mass and degree of rotational support. The survey is <jats:italic>K</jats:italic> <jats:sub> <jats:italic>s</jats:italic> </jats:sub>-band selected, irrespective of color or morphological type, and allows for a first assessment of the stellar dynamical structure of the general <jats:italic>L</jats:italic>* galaxy population at large look-back time. Using light profiles from Hubble Space Telescope imaging as a tracer, our approach corrects for observational effects (seeing convolution and slit geometry), and uses well-informed priors on inclination, anisotropy, and a non-luminous mass component. Tabulated data include total mass estimates in a series of spherical apertures (1, 5, and 10 kpc; 1 × and 2 × <jats:italic>R</jats:italic> <jats:sub>e</jats:sub>), as well as rotational velocities, velocity dispersions, and anisotropy. We show that almost all star-forming galaxies and ∼50% of quiescent galaxies are rotation dominated, with deprojected <jats:italic>V</jats:italic>/<jats:italic>σ</jats:italic> ∼ 1–2. Revealing the complexity in galaxy evolution, we find that the most massive star-forming galaxies are among the most rotation dominated, and the most massive quiescent galaxies among the least rotation-dominated galaxies. These measurements set a new benchmark for studying galaxy evolution, using stellar dynamical structure for galaxies at large look-back time. Together with the additional information on stellar population properties from the LEGA-C spectra, the dynamical mass and <jats:italic>V</jats:italic>/<jats:italic>σ</jats:italic> measurements presented here create new avenues for studying galaxy evolution at large look-back time.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We measure the near-UV (rest-frame ∼2400 Å) to optical color for early-type galaxies in 12 clusters at 0.3 &lt; <jats:italic>z</jats:italic> &lt; 1.0. We show that this is a suitable proxy for the more common far-ultraviolet bandpass used to measure the ultraviolet upturn and find that the upturn is detected to <jats:italic>z</jats:italic> = 0.6 in these data, in agreement with previous work. We find evidence that the strength of the upturn starts to wane beyond this redshift and largely disappears at <jats:italic>z</jats:italic> = 1. Our data are most consistent with models where early-type galaxies contain minority stellar populations with non-cosmological helium abundances, up to around 46%, formed at <jats:italic>z</jats:italic> ≥ 3, resembling globular clusters with multiple stellar populations in our Galaxy. This suggests that elliptical galaxies and globular clusters share similar chemical evolution and star formation histories. The vast majority of the stellar mass in these galaxies also must have been in place at <jats:italic>z</jats:italic> &gt; 3.</jats:p>