Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>To understand the formation and evolution of the Milky Way disk, we must connect its current properties to its past. We explore hydrodynamical cosmological simulations to investigate how the chemical abundances of stars might be linked to their origins. Using hierarchical clustering of abundance measurements in two Milky Way–like simulations with distributed and steady star formation histories, we find that groups of chemically similar stars comprise different groups in birth place (<jats:italic>R</jats:italic> <jats:sub>birth</jats:sub>) and time (age). Simulating observational abundance errors (0.05 dex), we find that to trace distinct groups of (<jats:italic>R</jats:italic> <jats:sub>birth</jats:sub>, age) requires a large vector of abundances. Using 15 element abundances (Fe, O, Mg, S, Si, C, P, Mn, Ne, Al, N, V, Ba, Cr, Co), up to ≈10 groups can be defined with ≈25% overlap in (<jats:italic>R</jats:italic> <jats:sub>birth</jats:sub>, age). We build a simple model to show that in the context of these simulations, it is possible to infer a star’s age and <jats:italic>R</jats:italic> <jats:sub>birth</jats:sub> from abundances with precisions of ±0.06 Gyr and ±1.17 kpc, respectively. We find that abundance clustering is ineffective for a third simulation, where low-<jats:italic>α</jats:italic> stars form distributed in the disk and early high-<jats:italic>α</jats:italic> stars form more rapidly in clumps that sink toward the Galactic center as their constituent stars evolve to enrich the interstellar medium. However, this formation path leads to large age dispersions across the [<jats:italic>α</jats:italic>/Fe]–[Fe/H] plane, which is inconsistent with the Milky Way’s observed properties. We conclude that abundance clustering is a promising approach toward charting the history of our Galaxy.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report the results obtained from a multiwavelength study of the H <jats:sc>ii</jats:sc> region G18.148−0.283 using the upgraded Giant Metrewave Radio Telescope at 1350 MHz, along with other archival data. In addition to the radio continuum emission, we have detected the H169<jats:italic>α</jats:italic> and H170<jats:italic>α</jats:italic> radio recombination lines toward G18.148−0.283 using a correlator bandwidth of 100 MHz. The moment-1 map of the ionized gas reveals a velocity gradient of approximately 10 km s<jats:sup>−1</jats:sup> across the radio continuum peaks. The <jats:sup>12</jats:sup>CO (<jats:italic>J</jats:italic> = 3−2) molecular line data from the CO High-Resolution Survey (COHRS) also show the presence of two velocity components that are very close to the velocities detected in the ionized gas. The spectrum and position–velocity diagram from CO emission reveal molecular gas at an intermediate-velocity range bridging the velocity components. We see mid-infrared absorption and far-infrared emission establishing the presence of a filamentary infrared dark cloud, the extent of which includes the targeted H <jats:sc>ii</jats:sc> region. The magnetic field inferred from dust polarization is perpendicular to the filament within the H <jats:sc>ii</jats:sc> region. We have also identified two O9 stars and 30 young stellar objects toward the target using data from the Two Micron All Sky Survey (2MASS), UKIRT Infrared Deep Sky Survey (UKIDSS), and Galactic Legacy Infrared Midplane Survey Extraordinaire (GLIMPSE). Cumulatively, this suggests that the region is the site of a cloud–cloud collision that has triggered massive star formation and subsequent formation of an H <jats:sc>ii</jats:sc> region.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>White dwarfs (WDs) often show metal lines in their spectra, indicating accretion of asteroidal material. Our Sun is to become a WD in several gigayears. Here, we examine how the solar WD accretes from the three major small body populations: the main belt asteroids (MBAs), Jovian Trojan asteroids (JTAs), and trans-Neptunian objects (TNOs). Owing to the solar mass loss during the giant branch, 40% of the JTAs are lost but the vast majority of MBAs and TNOs survive. During the WD phase, objects from all three populations are sporadically scattered onto the WD, implying ongoing accretion. For young cooling ages ≲100 Myr, accretion of MBAs predominates; our predicted accretion rate ∼10<jats:sup>6</jats:sup> g s<jats:sup>−1</jats:sup> falls short of observations by two orders of magnitude. On gigayear timescales, thanks to the consumption of the TNOs that kicks in ≳100 Myr, the rate oscillates around 10<jats:sup>6</jats:sup>–10<jats:sup>7</jats:sup> g s<jats:sup>−1</jats:sup> until several gigayears and drops to ∼10<jats:sup>5</jats:sup> g s<jats:sup>−1</jats:sup> at 10 Gyr. Our solar WD accretion rate from 1 Gyr and beyond agrees well with those of the extrasolar WDs. We show that for the solar WD, the accretion source region evolves in an inside-out pattern. Moreover, in a realistic small body population with individual sizes covering a wide range as WD pollutants, the accretion is dictated by the largest objects. As a consequence, the accretion rate is lower by an order of magnitude than that from a population of bodies of a uniform size and the same total mass and shows greater scatter.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Fuzzy dark matter (FDM), a scalar particle coupled to the gravitational field without self-interaction, whose mass range is <jats:italic>m</jats:italic> ∼ 10<jats:sup>−24</jats:sup>–10<jats:sup>−20</jats:sup> eV, is one of the promising alternative dark matter candidates to cold dark matter. The quantum interference pattern, which is a unique structure of FDM, can be seen in halos in cosmological FDM simulations. In this paper, we first provide an analytic model of the subgalactic matter power spectrum originating from quantum clumps in FDM halos, in which the density distribution of the FDM is expressed by a superposition of quantum clumps whose size corresponds to the de Broglie wavelength of the FDM. These clumps are assumed to be distributed randomly, such that the ensemble average density follows a halo profile such as the Navarro–Frenk–White profile. We then compare the convergence power spectrum projected along the line of sight around the Einstein radius, which is converted from the subgalactic matter power spectrum, to that measured in the strong lens system SDSS J0252 + 0039. While we find that the current observation provides no useful constraint on the FDM mass, we show that future deep, high spatial resolution observations of strong lens systems can tightly constrain FDM with a mass around 10<jats:sup>−22</jats:sup> eV.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Motivated by evidences favoring a rapid and late hydrogen reionization process completing at <jats:italic>z</jats:italic> ∼ 5.2–5.5 and mainly driven by rare and luminous sources, we have reassessed the estimate of the space density of ultra-luminous QSOs at <jats:italic>z</jats:italic> ∼ 5 in the framework of the QUBRICS survey. A ∼ 90% complete sample of 14 spectroscopically confirmed QSOs at <jats:italic>M</jats:italic> <jats:sub>1450</jats:sub> ≤ −28.3 and 4.5 ≤ <jats:italic>z</jats:italic> ≤ 5.0 has been derived in an area of 12,400 deg<jats:sup>2</jats:sup>, thanks to multiwavelength selection and Gaia astrometry. The space density of <jats:italic>z</jats:italic> ∼ 5 QSOs within −29.3 ≤ <jats:italic>M</jats:italic> <jats:sub>1450</jats:sub> ≤ −28.3 is three times higher than previous determinations. Our results suggest a steep bright-end slope for the QSO luminosity function at <jats:italic>z</jats:italic> ∼ 5 and a mild redshift evolution of the space density of ultrabright QSOs (<jats:italic>M</jats:italic> <jats:sub>1450</jats:sub> ∼ −28.5) at 3 &lt; <jats:italic>z</jats:italic> &lt; 5.5, in agreement with the redshift evolution of the much fainter active galactic nucleus (AGN) population at <jats:italic>M</jats:italic> <jats:sub>1450</jats:sub> ∼ −23. These findings are consistent with a pure density evolution for the AGN population at <jats:italic>z</jats:italic> &gt; 3. Adopting our <jats:italic>z</jats:italic> ∼ 4 QSO luminosity function and applying a mild density evolution in redshift, a photoionization rate of <jats:inline-formula> <jats:tex-math> <?CDATA ${{\rm{\Gamma }}}_{\mathrm{HI}}={0.46}_{-0.09}^{+0.17}\times {10}^{-12}\,{{\rm{s}}}^{-1}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">Γ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>HI</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>0.46</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.09</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.17</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>12</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em" /> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">s</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac33a4ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> has been obtained at <jats:italic>z</jats:italic> = 4.75, assuming an escape fraction of ∼70% and a steep faint-end slope of the AGN luminosity function. The derived photoionization rate is ∼50–100% of the ionizing background measured at the end of the reionization epoch, suggesting that AGNs could play an important role in the cosmological reionization process.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this study, we present an observational analysis of a coronal hole (CH) observed on 2018 November 1 and solar wind (SW) that originated from it, using the Solar Dynamics Observatory, the Parker Solar Probe (PSP) observations at 68 solar radii, ACE and WIND data at 1 au, and interplanetary scintillation (IPS) observations from 0.2 to 1 au. The CH-originated SW stream was observed by L1 on 2018 November 4 and by PSP on 2018 November 15. We examined the CH for nine Carrington Rotations (CR) and find that the SW stream to reach L1 varied from one CR to other. We find that the pressure, temperature, and magnetic fields increase as the speed of the SW increases and the density decreases with distance. We noticed suprathermal particle enhancement at and after the stream interaction region in both PSP and L1 observations, but the enhancement lasted longer in PSP compared to measurements made at L1. The multiple-rotation observations of the CH imply that any differences in observations between PSP and spacecraft at L1 are due to the radial evolution of the solar wind stream rather than of the CH or the source plasma itself. In addition, IPS measured the radio signal irregularities driven by the SW. Furthermore, we employed a standard analytical model to extrapolate the magnetic field at larger heights. We find that the extrapolated magnetic field at 68 <jats:italic>R</jats:italic> <jats:sub>⊙</jats:sub> and 1 au matches well with the magnetic field measured by PSP and OMNI.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Within an imaging instrument’s field of view, there may be many observational targets of interest. Similarly, within a spectrograph’s bandpass, there may be many emission lines of interest. The brightness of these targets and lines can be orders of magnitude different, which poses a challenge to instrument and mission design. A single exposure can saturate the bright emission and/or have a low signal-to-noise ratio (S/N) for faint emission. Traditional high dynamic range (HDR) techniques solve this problem by either combining multiple sequential exposures of varied duration or splitting the light to different sensors. These methods, however, can result in the loss of science capability, reduced observational efficiency, or increased complexity and cost. The simultaneous HDR method described in this paper avoids these issues by utilizing a special type of detector whose rows can be read independently to define zones that are then composited, resulting in areas with short or long exposure measured simultaneously. We demonstrate this technique for the Sun, which is bright on disk and faint off disk. We emulated these conditions in the lab to validate the method. We built an instrument simulator to demonstrate the method for a realistic solar imager and input. We then calculated S/Ns, finding a value of 45 for a faint coronal mass ejection and 200 for a bright one, both at 3.5 <jats:inline-formula> <jats:tex-math> <?CDATA ${{\boldsymbol{ \mathcal R }}}_{\odot }^{{\rm{N}}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi mathvariant="bold-italic"></mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">N</mml:mi> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac33a1ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>—meeting or far exceeding the international standard for digital photography that defines an S/N of 10 as acceptable and 40 as excellent. Future missions should consider this type of hardware and technique in their trade studies for instrument design.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present Hubble Space Telescope Cosmic Origin Spectrograph (COS) UV line spectroscopy and integral-field unit (IFU) observations of the intragroup medium in Stephan’s Quintet (SQ). SQ hosts a 30 kpc long shocked ridge triggered by a galaxy collision at a relative velocity of 1000 km s<jats:sup>−1</jats:sup>, where large amounts of molecular gas coexist with a hot, X-ray-emitting, plasma. COS spectroscopy at five positions sampling the diverse environments of the SQ intragroup medium reveals very broad (≈2000 km s<jats:sup>−1</jats:sup>) Ly<jats:italic>α</jats:italic> line emission with complex line shapes. The Ly<jats:italic>α</jats:italic> line profiles are similar to or much broader than those of H<jats:italic>β</jats:italic>, [C <jats:sc>ii</jats:sc>]157.7 <jats:italic>μ</jats:italic>m, and CO (1–0) emission. The extreme breadth of the Ly<jats:italic>α</jats:italic> emission, compared with H<jats:italic>β</jats:italic>, implies resonance scattering within the observed structure. Scattering indicates that the neutral gas of the intragroup medium is clumpy, with a significant surface covering factor. We observe significant variations in the Ly<jats:italic>α</jats:italic>/H<jats:italic>β</jats:italic> flux ratio between positions and velocity components. From the mean line ratio averaged over positions and velocities, we estimate the effective escape fraction of Ly<jats:italic>α</jats:italic> photons to be ≈10%–30%. Remarkably, over more than four orders of magnitude in temperature, the powers radiated by X-rays, Ly<jats:italic>α</jats:italic>, H<jats:sub>2</jats:sub>, and [C <jats:sc>ii</jats:sc>] are comparable within a factor of a few, assuming that the ratio of the Ly<jats:italic>α</jats:italic> to H<jats:sub>2</jats:sub> fluxes over the whole shocked intragroup medium stay in line with those observed at those five positions. Both shocks and mixing layers could contribute to the energy dissipation associated with a turbulent energy cascade. Our results may be relevant for the cooling of gas at high redshifts, where the metal content is lower than in this local system, and a high amplitude of turbulence is more common.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Ram pressure stripping is a crucial evolutionary driver for cluster galaxies. It is thought to be able to accelerate the evolution of their star formation, trigger the activity of their central active galactic nucleus (AGN) and the interplay between galactic and environmental gas, and eventually dissipate their gas reservoirs. We explored the outcomes of ram pressure stripping by studying the nonthermal radio emission of the jellyfish galaxy JW100 in the cluster A2626 (<jats:italic>z</jats:italic> = 0.055), by combining LOw Frequency Array, MeerKAT, and Very Large Array observations from 0.144 to 5.5 GHz. We studied the integrated spectra of the stellar disk, the stripped tail, and the AGN; mapped the spectral index over the galaxy; and constrained the magnetic field intensity to between 11 and 18 <jats:italic>μ</jats:italic>G in the disk and &lt;10 <jats:italic>μ</jats:italic>G in the tail. The stellar disk radio emission is dominated by a radiatively old plasma, likely related to an older phase of a high star formation rate. This suggests that the star formation was quickly quenched by a factor of 4 in a few 10<jats:sup>7</jats:sup> yr. The radio emission in the tail is consistent with the stripping scenario, where the radio plasma that originally accelerated in the disk is subsequently displaced in the tail. The morphology of the radio and X-ray emissions supports the scenario of the accretion of magnetized environmental plasma onto the galaxy. The AGN nonthermal spectrum indicates that relativistic electron acceleration may have occurred simultaneously with a central ionized gas outflow, thus suggesting a physical connection between the two processes.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We explore the connection between the <jats:italic>γ</jats:italic>-ray and radio emission in the jet of the blazar 0716+714 by using 15, 37, and 230 GHz radio and 0.1–200 GeV <jats:italic>γ</jats:italic>-ray light curves spanning 10.5 yr (2008–2019). We find significant positive and negative correlations between radio and <jats:italic>γ</jats:italic>-ray fluxes in different time ranges. The time delays between radio and <jats:italic>γ</jats:italic>-ray emission suggest that the observed <jats:italic>γ</jats:italic>-ray flares originated from multiple regions upstream of the radio core, within a few parsecs from the central engine. Using time-resolved 43 GHz Very Long Baseline Array maps we identified 14 jet components moving downstream along the jet. Their apparent speeds range from 6<jats:italic>c</jats:italic> to 26<jats:italic>c</jats:italic>, and they show notable variations in their position angles upstream from the stationary component (∼0.53 mas from the core). The brightness temperature declines as a function of distance from the core according to a power law that becomes shallower at the location of the stationary component. We also find that the periods at which significant correlations between radio and <jats:italic>γ</jats:italic>-ray emission occur overlap with the times when the jet was oriented to the north. Our results indicate that the passage of a propagating disturbance (or shock) through the radio core and the orientation of the jet might be responsible for the observed correlation between the radio and <jats:italic>γ</jats:italic>-ray variability. We present a scenario that connects the positive correlation and the unusual anticorrelation by combining the production of a flare and a dip at <jats:italic>γ</jats:italic>-rays by a strong moving shock at different distances from the jet apex.</jats:p>