Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We measure the star cluster mass function (CMF) for the Local Group galaxy M33. We use the catalog of stellar clusters selected from the Panchromatic Hubble Andromeda Treasury: Triangulum Extended Region survey. We analyze 711 clusters in M33 with <jats:inline-formula> <jats:tex-math> <?CDATA $7.0\lt \mathrm{log}(\mathrm{Age}/\mathrm{yr})\lt 8.5$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>7.0</mml:mn> <mml:mo>&lt;</mml:mo> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mi>Age</mml:mi> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mi>yr</mml:mi> <mml:mo stretchy="false">)</mml:mo> <mml:mo>&lt;</mml:mo> <mml:mn>8.5</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac51cfieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, and log(<jats:italic>M</jats:italic>/<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) &gt; 3.0 as determined from color–magnitude diagram fits to individual stars. The M33 CMF is best described by a Schechter function with power-law slope <jats:italic>α</jats:italic> = −<jats:inline-formula> <jats:tex-math> <?CDATA ${2.06}_{-0.13}^{+0.14}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>2.06</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.13</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.14</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac51cfieqn2.gif" xlink:type="simple" /> </jats:inline-formula>, and truncation mass log(<jats:italic>M</jats:italic> <jats:sub> <jats:italic>c</jats:italic> </jats:sub>/<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) <jats:inline-formula> <jats:tex-math> <?CDATA $=\,{4.24}_{-0.13}^{+0.16}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>=</mml:mo> <mml:mspace width="0.50em" /> <mml:msubsup> <mml:mrow> <mml:mn>4.24</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.13</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.16</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac51cfieqn3.gif" xlink:type="simple" /> </jats:inline-formula>. The data show strong evidence for a high-mass truncation, thus strongly favoring a Schechter function fit over a pure power law. M33's truncation mass is consistent with the previously identified linear trend between <jats:italic>M</jats:italic> <jats:sub> <jats:italic>c</jats:italic> </jats:sub>, and star formation rate surface density, Σ<jats:sub>SFR</jats:sub>. We also explore the effect that individual cluster mass uncertainties have on derived mass function parameters, and find evidence to suggest that large cluster mass uncertainties have the potential to bias the truncation mass of fitted mass functions at the 1<jats:italic>σ</jats:italic> level.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report the discovery of statistically significant spatial structures in the projected two-dimensional distributions of Globular Cluster (GC) systems of 10 galaxies that are among the brightest in the Fornax Cluster. We use a catalog of GCs extracted from the Hubble Space Telescope Advanced Camera for Surveys Fornax Cluster Survey imaging data. We characterize the size, shape, and location relative to the host galaxies of the GC structures and suggest a classification based on their morphology and location that is suggestive of different formation mechanisms. We also investigate the GC structures in the context of the positions of their host galaxies relative to the general spatial distributions of galaxies and intracluster GCs in the Fornax Cluster. We finally estimate the dynamical masses of the progenitors of some GC structures under the assumption that they are the relics of past accretion events of satellite galaxies by their hosts.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We explore the significance of noise from thermal Sunyaev–Zel’dovich (tSZ) signals for cluster detection using cosmic microwave background (CMB) surveys. The noise arises both from neighboring objects and also from haloes below the detection limit. A wide range of surveys are considered: SPT-SZ, SPTpol, and SPT-3G from the South Pole Telescope; SO-Baseline and SO-Goal configurations for Simons Observatory; CMB-S4's wide-area (S4-Wide) and deep (S4-Ultra deep) surveys; and the futuristic CMB-HD experiment. We find that the noise from tSZ signals has a significant impact on CMB-HD and to some extent on S4-Ultra deep. For other experiments, the effect is negligible as the noise in the tSZ map is dominated by residual foregrounds or experimental noise. In the limit when the noise from tSZ signals is important, we find that removing the detected clusters and rerunning the cluster finder allows us to find a new set of less massive and distant clusters. Since the detected clusters are the dominant source of the tSZ power, removing them reduces the power at <jats:italic>ℓ</jats:italic> = 3000 by ×5 for CMB-HD; ×3.1 of S4-Ultra deep; ×2.4 for S4-Wide and SPT-3G; ×1.5 for SO-Goal and SPTpol; ×1.35 for SO-Baseline; and ×1.08 for SPT-SZ. We forecast the expected number of clusters and also derive parameter constraints by combining cluster counts with primary CMB and tSZ power spectra finding that the future surveys can reduce the error on the dark energy equation of state parameter to sub-percent levels and can also enable ≥3<jats:italic>σ</jats:italic> detection of the sum of neutrino masses.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The observed optical colors of quasars are generally interpreted in one of two frameworks: unified models that attribute the color to the random orientation of the accretion disk along the line of sight, and evolutionary models that invoke connections between quasar systems and their environments. We test these schemas by probing the dark matter halo environments of optically selected quasars as a function of <jats:italic>g</jats:italic> − <jats:italic>i</jats:italic> optical color by measuring the two-point correlation functions of ∼0.34 million eBOSS quasars as well as the gravitational deflection of cosmic microwave background photons around ∼0.66 million XDQSO photometric quasar candidates. We do not detect a trend of halo bias with optical color through either analysis, finding that optically selected quasars at 0.8 &lt; <jats:italic>z</jats:italic> &lt; 2.2 occupy halos of characteristic mass <jats:italic>M</jats:italic> <jats:sub> <jats:italic>h</jats:italic> </jats:sub> ∼ 3 × 10<jats:sup>12</jats:sup> <jats:italic>h</jats:italic> <jats:sup>−1</jats:sup> <jats:italic> M</jats:italic> <jats:sub>⊙</jats:sub> regardless of their color. This result implies that a quasar’s large-scale halo environment is not strongly connected to its observed optical color. We also confirm the findings of fundamental differences in the radio properties of red and blue quasars by stacking 1.4 GHz FIRST images at their positions, suggesting the observed differences cannot be attributed to orientation. Instead, the differences between red and blue quasars likely arise on nuclear-galactic scales, perhaps owing to reddening by a nuclear dusty wind. Finally, we show that optically selected quasars’ halo environments are also independent of their <jats:italic>r</jats:italic> − W2 optical–infrared colors, while previous work has suggested that mid-infrared-selected obscured quasars occupy more massive halos. We discuss the implications of this result for models of quasar and galaxy coevolution.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Stars are formed by gravitational collapse, spontaneously or, in some cases under the constructive influence of nearby massive stars, out of molecular cloud cores. Here we present an observational diagnosis of such triggered formation processes in the prominent H <jats:sc>ii</jats:sc> region Sh 2-142, which is associated with the young star cluster NGC 7380, and with some bright-rimmed clouds as the signpost of photoionization of molecular cloud surfaces. Using near- (2MASS) and mid-infrared (WISE) colors, we identified candidate young stars at different evolutionary stages, including embedded infrared sources having spectral energy distributions indicative of active accretion. We have also used data from our optical observations to be used in SEDs, and from Gaia EDR3 to study the kinematics of young objects. With this young stellar sample, together with the latest CO line emission data (spectral resolution ∼0.16 km s<jats:sup>−1</jats:sup>, sensitivity ∼0.5 K), a positional and aging sequence relative to the neighboring cloud complex, and to the bright-rimmed clouds, is inferred. The propagating stellar birth may be responsible, at least partially, for the formation of the cluster a few million years ago, and for the ongoing activity now witnessed in the cloud complex.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Sensitive radio instruments are optimized for observing faint astronomical sources, and usually need to attenuate the received signal when observing the Sun. There are only a handful of flux density calibrators that can comfortably be observed with the same attenuation setup as the Sun. Additionally, for wide field-of-view (FoV) instruments like the Murchison Widefield Array (MWA) calibrator observations are generally done when the Sun is below the horizon, to avoid the contamination from solar emissions. These considerations imply that the usual radio interferometric approach to flux density calibration is not applicable for solar imaging. A novel technique, relying on a good sky model and detailed characterization of the MWA hardware, was developed for solar flux density calibration for MWA. Though successful, this technique is not general enough to be extended to the data from the extended configuration of the MWA Phase II. Here, we present a robust flux density calibration method for solar observations with MWA independent of the array configuration. We use different approaches—the serendipitous presence of strong sources; detection of numerous background sources using high dynamic range images in the FoV along with the Sun; and observations of strong flux density calibrators with and without the additional attenuation used for solar observations—to obtain the flux scaling parameters required for the flux density calibration. Using the present method, we have achieved an absolute flux density uncertainty ∼10% for solar observations even in the absence of dedicated calibrator observations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We input the solar wind parameters responsible for the main phases of 15 great geomagnetic storms (GGSs; ΔSYM-H ≤ −200 nT) into the empirical formulae created by Burton et al. (hereafter the Burton equation) and by OBrien &amp; McPherron (hereafter the OM equation) to evaluate whether these two equations can correctly estimate the intensities of GGSs. The results show that the intensities of most GGSs estimated by the OM equation are much smaller than the observed intensities. The rms error between the intensities estimated by the OM equation and the observed intensities is 203 nT, implying that the estimated storm intensity deviates significantly from the observed one. The rms error between the intensities estimated by the Burton equation and the observed intensities is 130.8 nT. The relative error caused by the Burton equation for storms with intensities ΔSYM-H&lt;−400 nT is larger than 27%, implying that the absolute error will be large for storms with ΔSYM-H &lt; −400 nT. The results indicate that the two equations cannot predict the intensities of GGSs correctly. On the contrary, the intensity of a GGS estimated by the empirical formula created by Wang et al. can approximate observations better if we select the right weight for the solar wind dynamic pressure, proving that solar wind dynamic pressure is an important factor of GGS intensity. This pressure is overlooked by the ring current injection terms of the Burton and OM equations. This is the reason why the two equations do not effectively estimate GGSs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Using simultaneous Very Long Baseline Array and Neil Gehrels Swift Observatory X-ray Telescope observations of the active galactic nucleus (AGN) in NGC 2992 over a six-month observing campaign, we observed a large drop in core 5 cm radio luminosity, by a factor of &gt;3, in tandem with a factor of &gt;5 increase in 2–10 keV X-ray luminosity. While NGC 2992 has long been an important object for studies of X-ray variability, our study is the first simultaneous X-ray and radio variability campaign for this object. We observe that the X-ray spectral index does not change over the course of the flare, consistent with a change in the bulk amount of Comptonizing plasma, potentially due to a magnetic reconnection event in the accretion disk. The drop in apparent radio luminosity can be explained by a change in free–free absorption, which we calculate to correspond to an ionized region with a physical extent and electron density consistent with the broad-line region (BLR). Our results are consistent with magnetic reconnection events in the dynamic accretion disk creating outbursts of ionizing material, increasing Compton up-scattering of UV accretion disk photons and feeding material into the BLR. These findings present an important physical picture for the dynamical relationship between X-ray and radio emission in AGNs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Tibet AS<jats:italic>γ</jats:italic> experiment provided the first measurement of the total diffuse gamma-ray emission from the Galactic disk in the sub-PeV energy range. Based on the analysis of TeV sources included in the H.E.S.S. Galactic Plane Survey catalog, we predict the expected contribution of unresolved pulsar-powered sources in the two angular windows of the Galactic plane observed by Tibet AS<jats:italic>γ</jats:italic>. We show that the sum of this additional diffuse component due to unresolved sources and the truly diffuse emission, due to cosmic-ray interaction with the interstellar medium, well saturates the Tibet data, without the need to introduce a progressive hardening of the cosmic-ray spectrum toward the Galactic center.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Using methods of differential evolution (DE), we determined the coronal elemental abundances and the differential emission measure (DEM) distributions for the plasma flaring on 2003 January 21. The analyses have been made based on RESIK X-ray spectra. DE belongs to the family of evolutionary algorithms. DE is conceptually simple and easy to implement, so it has been applied to solve many problems in science and engineering. In this study we apply this method in a new context: simultaneous determination of plasma composition and DEM. In order to increase the confidence of the results obtained using DE, we tested the use of its algorithms by comparing the DE synthesized with respective spectra observed by RESIK. Extensive discussion of the DE method used and the obtained physical characteristics of flaring plasma is presented.</jats:p>