Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We have analyzed Atacama Large Millimeter/submillimeter Array Band 6 data of the hypercompact H <jats:sc>ii</jats:sc> region G24.78+0.08 A1 (G24 HC H <jats:sc>ii</jats:sc>) and report the detection of vibrationally excited lines of HC<jats:sub>3</jats:sub>N (<jats:italic>v</jats:italic> <jats:sub>7</jats:sub> = 2, <jats:italic>J</jats:italic> = 24 − 23). The spatial distribution and kinematics of a vibrationally excited line of HC<jats:sub>3</jats:sub>N (<jats:italic>v</jats:italic> <jats:sub>7</jats:sub> = 2, <jats:italic>J</jats:italic> = 24 − 23, <jats:italic>l</jats:italic> = 2<jats:italic>e</jats:italic>) are found to be similar to the CH<jats:sub>3</jats:sub>CN vibrationally excited line (<jats:italic>v</jats:italic> <jats:sub>8</jats:sub> = 1), which indicates that the HC<jats:sub>3</jats:sub>N emission is tracing the disk around the G24 HC H <jats:sc>ii</jats:sc> region previously identified by the CH<jats:sub>3</jats:sub>CN lines. We derive the <jats:sup>13</jats:sup>CH<jats:sub>3</jats:sub>CN/HC<jats:sup>13</jats:sup>CCN abundance ratios around G24 and compare them to the CH<jats:sub>3</jats:sub>CN/HC<jats:sub>3</jats:sub>N abundance ratios in disks around Herbig Ae and T Tauri stars. The <jats:sup>13</jats:sup>CH<jats:sub>3</jats:sub>CN/HC<jats:sup>13</jats:sup>CCN ratios around G24 (∼3.0–3.5) are higher than the CH<jats:sub>3</jats:sub>CN/HC<jats:sub>3</jats:sub>N ratios in the other disks (∼0.03–0.11) by more than 1 order of magnitude. The higher CH<jats:sub>3</jats:sub>CN/HC<jats:sub>3</jats:sub>N ratios around G24 suggest that the thermal desorption of CH<jats:sub>3</jats:sub>CN in the hot dense gas and efficient destruction of HC<jats:sub>3</jats:sub>N in the region irradiated by the strong UV radiation are occurring. Our results indicate that the vibrationally excited HC<jats:sub>3</jats:sub>N lines can be used as a disk tracer of massive protostars at the HC H <jats:sc>ii</jats:sc> region stage, and the combination of these nitrile species will provide information of not only chemistry but also physical conditions of the disk structures.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a beam pattern measurement of the Canadian Hydrogen Intensity Mapping Experiment (CHIME) made using the Sun as a calibration source. As CHIME is a pure drift-scan instrument, we rely on the seasonal north–south motion of the Sun to probe the beam at different elevations. This semiannual range in elevation, combined with the radio brightness of the Sun, enables a beam measurement that spans ∼7200 square degrees on the sky without the need to move the telescope. We take advantage of observations made near solar minimum to minimize the impact of solar variability, which is observed to be &lt;10% in intensity over the observation period. The resulting data set is highly complementary to other CHIME beam measurements—both in terms of angular coverage and systematics—and plays an important role in the ongoing program to characterize the CHIME primary beam.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Experimental and theoretical results are presented for double, triple, and quadruple photoionization of Si<jats:sup>+</jats:sup> and Si<jats:sup>2+</jats:sup> ions and for double photoionization of Si<jats:sup>3+</jats:sup> ions by a single photon. The experiments employed the photon–ion merged-beams technique at a synchrotron light source. The experimental photon-energy range 1835–1900 eV comprises resonances associated with the excitation of a 1<jats:italic>s</jats:italic> electron to higher subshells and subsequent autoionization. Energies, widths, and strengths of these resonances are extracted from high-resolution photoionization measurements, and the core-hole lifetime of K-shell ionized neutral silicon is inferred. In addition, theoretical cross sections for photoabsorption and multiple photoionization were obtained from large-scale multiconfiguration Dirac–Hartree–Fock calculations. The present calculations agree with the experiment much better than previously published theoretical results. The importance of an accurate energy calibration of laboratory data is pointed out. The present benchmark results are particularly useful for discriminating between silicon absorption in the gaseous and in the solid component (dust grains) of the interstellar medium.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Methanol (CH<jats:sub>3</jats:sub>OH) is an abundant interstellar species and is known to be an important precursor of various interstellar complex organic molecules. Among the methanol isotopologues, CH<jats:sub>2</jats:sub>DOH is one of the most abundant isotopologues and it is often used to study the deuterium fractionation of CH<jats:sub>3</jats:sub>OH in interstellar medium. However, the emission lines of CH<jats:sub>2</jats:sub>DOH can sometimes be optically thick, making the derivation of its abundance unreliable. Therefore, observations of its presumably optically thin <jats:sup>13</jats:sup>C substituted species, <jats:sup>13</jats:sup>CH<jats:sub>2</jats:sub>DOH, are essential to overcome this issue. In this study, the rotational transitions of <jats:sup>13</jats:sup>CH<jats:sub>2</jats:sub>DOH have been measured in the millimeter-wave region from 216 GHz to 264 GHz with an emission-type millimeter- and submillimeter-wave spectrometer by using a deuterium and <jats:sup>13</jats:sup>C enriched sample. The frequency accuracy of measured <jats:sup>13</jats:sup>CH<jats:sub>2</jats:sub>DOH is less than a few kHz, and the relative line intensity error is less than 10% in most of the frequency range by taking advantage of the wide simultaneous frequency-coverage of the emission-type spectrometer. These results offer a good opportunity to detect <jats:sup>13</jats:sup>CH<jats:sub>2</jats:sub>DOH in space, which will allow us to study the deuterium fractionation of CH<jats:sub>3</jats:sub>OH in various sources through accurate determination of the CH<jats:sub>2</jats:sub>DOH abundance.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report an improved measurement of the degree-scale cosmic microwave background <jats:italic>B</jats:italic>-mode angular-power spectrum over 670 deg<jats:sup>2</jats:sup> sky area at 150 GHz with P<jats:sc>olarbear</jats:sc>. In the original analysis of the data, errors in the angle measurement of the continuously rotating half-wave plate, a polarization modulator, caused significant data loss. By introducing an angle-correction algorithm, the data volume is increased by a factor of 1.8. We report a new analysis using the larger data set. We find the measured <jats:italic>B</jats:italic>-mode spectrum is consistent with the ΛCDM model with Galactic dust foregrounds. We estimate the contamination of the foreground by cross-correlating our data and Planck 143, 217, and 353 GHz measurements, where its spectrum is modeled as a power law in angular scale and a modified blackbody in frequency. We place an upper limit on the tensor-to-scalar ratio <jats:italic>r</jats:italic> &lt; 0.33 at 95% confidence level after marginalizing over the foreground parameters.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Fisher information matrix (FM) plays an important role in forecasts and inferences in many areas of physics. While giving fast parameter estimation with Gaussian likelihood approximation in the parameter space, the FM can only give the ellipsoidal posterior contours of the parameters and it loses the higher-order information beyond Gaussianity. We extend the FM in gravitational-wave (GW) data analysis by using the Derivative Approximation for LIkelihoods (DALI), a method to expand the likelihood, while keeping it positive definite and normalizable at every order, for more accurate forecasts and inferences. When applied to two real GW events, GW150914 and GW170817, DALI can reduce the difference between the FM approximation and the real posterior by 5 times in the best case. The calculation times of DALI and the FM are at the same order of magnitude, while obtaining the real full posterior will take several orders of magnitude longer. Besides more accurate approximations, higher-order correction from DALI provides a fast assessment of the FM analysis and gives suggestions for complex sampling techniques that are computationally intensive. We recommend using the DALI method as an extension to the FM method in GW data analysis to pursue better accuracy while still keeping the speed.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The Large Magellanic Cloud (LMC) is the nearest laboratory for detailed studies on the formation and survival of complex organic molecules (COMs), including biologically important ones, in low-metallicity environments—typical of earlier cosmological epochs. We report the results of 1.2 mm continuum and molecular line observations of three fields in the star-forming region N 105 with the Atacama Large Millimeter/submillimeter Array. N 105 lies at the western edge of the LMC bar with ongoing star formation traced by H<jats:sub>2</jats:sub>O, OH, and CH<jats:sub>3</jats:sub>OH masers, ultracompact H <jats:sc>ii</jats:sc> regions, and young stellar objects. Based on the spectral line modeling, we estimated rotational temperatures, column densities, and fractional molecular abundances for 12 1.2 mm continuum sources. We identified sources with a range of chemical makeups, including two bona fide hot cores and four hot core candidates. The CH<jats:sub>3</jats:sub>OH emission is widespread and associated with all the continuum sources. COMs CH<jats:sub>3</jats:sub>CN and CH<jats:sub>3</jats:sub>OCH<jats:sub>3</jats:sub> are detected toward two hot cores in N 105 together with smaller molecules typically found in Galactic hot cores (e.g., SO<jats:sub>2</jats:sub>, SO, and HNCO) with the molecular abundances roughly scaling with metallicity. We report a tentative detection of the astrobiologically relevant formamide molecule (NH<jats:sub>2</jats:sub>CHO) toward one of the hot cores; if confirmed, this would be the first detection of NH<jats:sub>2</jats:sub>CHO in an extragalactic subsolar metallicity environment. We suggest that metallicity inhomogeneities resulting from the tidal interactions between the LMC and the Small Magellanic Cloud might have led to the observed large variations in COM abundances in LMC hot cores.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The stellar initial mass function (IMF) is a fundamental property in the measurement of stellar masses and galaxy star formation histories. In this work, we focus on the most massive galaxies in the nearby universe <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}({M}_{\star }/\,{M}_{\odot })\gt 11.2$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⋆</mml:mo> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mspace width="0.25em" /> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> <mml:mo>&gt;</mml:mo> <mml:mn>11.2</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac69eaieqn1.gif" xlink:type="simple" /> </jats:inline-formula>. We obtain high-quality Magellan/LDSS-3 long-slit spectroscopy with a wide wavelength coverage of 0.4–1.01 <jats:italic>μ</jats:italic>m for 41 early-type galaxies (ETGs) in the MASSIVE survey and derive high signal-to-noise spectra within an aperture of <jats:italic>R</jats:italic> <jats:sub>e</jats:sub>/8. Using detailed stellar synthesis models, we constrain the elemental abundances and stellar IMF of each galaxy through full spectral modeling. All the ETGs in our sample have an IMF that is steeper than a Milky Way (Kroupa) IMF. The best-fit IMF mismatch parameter, <jats:italic>α</jats:italic> <jats:sub>IMF</jats:sub> = (<jats:italic>M</jats:italic>/<jats:italic>L</jats:italic>)/(<jats:italic>M</jats:italic>/<jats:italic>L</jats:italic>)<jats:sub>MW</jats:sub>, ranges from 1.1 to 3.1, with an average of 〈<jats:italic>α</jats:italic> <jats:sub>IMF</jats:sub>〉 = 1.84, suggesting that on average, the IMF is more bottom heavy than Salpeter. Comparing the estimated stellar masses with the dynamical masses, we find that most galaxies have stellar masses that are smaller than their dynamical masses within the 1<jats:italic>σ</jats:italic> uncertainty. We complement our sample with lower-mass galaxies from the literature and confirm that <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}({\alpha }_{\mathrm{IMF}})$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>α</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>IMF</mml:mi> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac69eaieqn2.gif" xlink:type="simple" /> </jats:inline-formula> is positively correlated with <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}(\sigma )$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:mi>σ</mml:mi> <mml:mo stretchy="false">)</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac69eaieqn3.gif" xlink:type="simple" /> </jats:inline-formula>, <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}({M}_{\star })$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⋆</mml:mo> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac69eaieqn4.gif" xlink:type="simple" /> </jats:inline-formula>, and <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}({M}_{\mathrm{dyn}})$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>dyn</mml:mi> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac69eaieqn5.gif" xlink:type="simple" /> </jats:inline-formula>. From the combined sample, we show that the IMF in the centers of more massive ETGs is more bottom heavy. In addition, we find that <jats:inline-formula> <jats:tex-math> <?CDATA $\mathrm{log}({\alpha }_{\mathrm{IMF}})$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>α</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>IMF</mml:mi> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac69eaieqn6.gif" xlink:type="simple" /> </jats:inline-formula> is positively correlated with both [Mg/Fe] and the estimated total metallicity [Z/H]. We find suggestive evidence that the effective stellar surface density Σ<jats:sub>Kroupa</jats:sub> might be responsible for the variation of <jats:italic>α</jats:italic> <jats:sub>IMF</jats:sub>. We conclude that <jats:italic>σ</jats:italic>, [Mg/Fe], and [Z/H] are the primary drivers of the global stellar IMF variation.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We reported two new glitches of PSR B1822−09 that were detected at the Shanghai Tian Ma Radio Telescope. The glitches occurred around MJD 58,025 and 58,474.5, respectively. The shapes of the integrated mean pulse profiles in both the radio-bright (B-mode) and the radio-quiet (Q-mode) modes changed after two glitches. Such changes are probably related to the trigger mechanisms of the glitches. According to the Gaussian fitting to the integrated mean pulse profiles, variations of the integrated mean pulse profiles can be attributed to variations of the Gaussian components. The fitting also indicates that there may be changes in only a part of the Gaussian components after glitches. We proposed an interpretation of the relation between the precursor and the interpulse of PSR B1822−09 according to variations of Gaussian components. We analyzed the cumulative distributions of the glitch sizes and the waiting times of all 14 glitches of PSR B1822−09. The cumulative distribution of the glitch sizes can be fitted well by a power law with an index <jats:italic>α</jats:italic> of 0.985 ± 0.005. The cumulative distribution of the waiting times follows a Poisson model with a mean waiting time <jats:italic>λ</jats:italic> of 466 ± 66 days. The correlation coefficient between the waiting times and the sizes of the corresponding preceding glitches is 0.906. In contrast, there is no apparent correlation between the waiting times and the sizes of the corresponding trailing glitches.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We use 13 yr of Swift/BAT observations to probe the nature and origin of the hard X-ray (14–195 KeV) emission in Centaurus A. Since the beginning of the Swift operation in 2004, significant X-ray variability in the 14–195 KeV band has been detected, with mild changes in the source spectrum. Spectral variations became more eminent after 2013, following a softer-when-brighter trend. Using the power spectral density (PSD) method, we find that the observed hard X-ray photon flux variations are consistent with a red-noise process of slope, −1.3, with no evidence for a break in the PSD. We find a significant correlation between the hard X-ray and 230 GHz radio flux variations, with no time delay longer than 30 days. The temporal and spectral analysis confirms that the X-ray emission generated by the accretion in the ADAF model is sub-dominant as compared with the emission arising from that produced by the inner regions of the radio jet.</jats:p>