Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>The discovery of substructures in protoplanetary disks by the Atacama Large Millimeter/submillimeter Array (ALMA) has provided us with key insights into the formation of planets. However, observational constraints on the formation of rocky planets have been still sparse, especially because of the limited spatial resolution. The inner edge of the so-called dead zone is one of the preferential sites of rocky planet formation. We investigate the capabilities of ALMA and Next Generation Very Large Array (ngVLA) for observing a dust concentration expected at the inner edge of the dead zone around a Herbig star. Herbig Ae/Be stars are useful laboratories for exploring the evolution of rocky grains in protoplanetary disks because of their high luminosity that pushes the dead zone inner edge outward. We find that, thanks to its unprecedented angular resolution and sensitivity, ngVLA can detect the dust concentration at the dead zone inner edge, with a reasonable integration time of 10 hr at <jats:italic>λ</jats:italic> = 3, 7 mm, and 1 cm. The dust concentration is expected to be optically thick at the ALMA wavelengths and cannot be spatially resolved due to its limited resolution. On the other hand, the flux density from the inner disk regions (∼3–4 au) observed with current VLA is higher for disks with a dust ring, and hence would be a useful indicator that helps us choose potential candidates of disks having a dust concentration at the innermost region. With these observations we can characterize the process of dust concentration in the innermost disk regions, where rocky planets can form.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The immense power of gamma-ray bursts (GRBs) makes them ideal probes of the early universe. By using absorption lines in the afterglows of high-redshift GRBs, astronomers can study the evolution of metals in the early universe. With an understanding of the nature of GRB progenitors, the rate and properties of GRBs observed at high redshift can probe the star formation history and the initial mass function of stars at high redshift. This paper presents a detailed study of the dependence on metallicity and mass of the properties of long-duration GRBs under the black hole accretion disk paradigm to predict the evolution of these properties with redshift. These models are calibrated on the current GRB observations and then used to make predictions for new observations and new missions (e.g., the proposed Gamow mission) studying high-redshift GRBs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Galactic circumnuclear environments of nearby galaxies provide unique opportunities for our understanding of the coevolution between supermassive black holes and their host galaxies. Here, we present a detailed study of ionized gas in the central kiloparsec region of M81, which hosts the closest prototype low-luminosity active galactic nucleus, based on optical integral-field spectroscopic observations taken with the CAHA 3.5 m telescope. It is found that much of the circumnuclear ionized gas is concentrated within a bright core of ∼200 pc in extent and a surrounding spiral-like structure known as the nuclear spiral. The total mass of the ionized gas is estimated to be ∼2 × 10<jats:sup>5</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, which corresponds to a few percent of the cold gas mass in this region, as traced by co-spatial dust extinction features. Plausible signature of a biconical outflow along the disk plane is suggested by a pair of blueshifted/redshifted low-velocity features, symmetrically located at ∼120–250 pc from the nucleus. The spatially resolved line ratios of [N <jats:sc>ii</jats:sc>]/H<jats:italic>α</jats:italic> and [O <jats:sc>iii</jats:sc>]/H<jats:italic>β</jats:italic> demonstrate that much of the circumnuclear region can be classified as a LINER. However, substantial spatial variations in the line intensities and line ratios strongly suggest that different ionization/excitation mechanisms, rather than just a central dominant source of photoionization, are simultaneously at work to produce the observed line signatures.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Bars may induce morphological features, such as rings, through their resonances. Previous studies suggested that the presence of “dark gaps,” or regions of a galaxy where the difference between the surface brightness along the bar major axis and that along the bar minor axis is maximal, can be attributed to the location of bar corotation. Here, using GALAKOS, a high-resolution <jats:italic>N</jats:italic>-body simulation of a barred galaxy, we test this photometric method’s ability to identify the bar corotation resonance. Contrary to previous work, our results indicate that “dark gaps” are a clear sign of the location of the 4:1 ultraharmonic resonance instead of bar corotation. Measurements of the bar corotation can indirectly be inferred using kinematic information, e.g., by measuring the shape of the rotation curve. We demonstrate our concept on a sample of 578 face-on barred galaxies with both imaging and integral field observations and find that the sample likely consists primarily of fast bars.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A major uncertainty in understanding the transport and feedback of cosmic rays (CRs) within and beyond our Galaxy lies in the unknown CR scattering rates, which are primarily determined by wave–particle interaction at microscopic gyroresonant scales. The source of the waves for the bulk CR population is believed to be self-driven by the CR streaming instability (CRSI), resulting from the streaming of CRs downward a CR pressure gradient. While a balance between driving by the CRSI and wave damping is expected to determine wave amplitudes and hence the CR scattering rates, the problem involves significant scale separation with substantial ambiguities based on quasi-linear theory (QLT). Here we propose a novel “streaming box” framework to study the CRSI with an imposed CR pressure gradient, enabling first-principles measurement of the CR scattering rates as a function of environmental parameters. By employing the magnetohydrodynamic particle-in-cell method with ion–neutral damping, we conduct a series of simulations with different resolutions and CR pressure gradients and precisely measure the resulting CR scattering rates in steady state. The measured rates show scalings consistent with QLT, but with a normalization smaller by a factor of several than typical estimates based on the single-fluid treatment of CRs. A momentum-by-momentum treatment provides better estimates when integrated over momentum but is also subject to substantial deviations, especially at small momentum. Our framework thus opens up the path toward providing comprehensive subgrid physics for macroscopic studies of CR transport and feedback in broad astrophysical contexts.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Stellar metallicity distribution functions (MDFs) have been measured for resolved stellar populations in the outer halos of many galaxies in nearby groups. Among them, the MDF of NGC 5128, the central giant elliptical in the Centaurus group, provides essential constraints for theories of massive galaxy formation and hierarchical assembly. To investigate the formation and chemical evolution history of the outer halo of giant elliptical galaxies, we examine the chemical properties of three zoom-in high-resolution cosmological hydrodynamical simulations of an NGC 5128–like giant elliptical galaxy and compare their outer halo MDFs to the observed one of NGC 5128. Even though the simulated galaxies have different merging histories and age distributions, all predicted MDFs are in good qualitative agreement with the observed one. The median metallicity of the simulated galaxies is, on average, [M/H] = −0.41 ± 0.06 compared to the observed value of [M/H] = −0.38 ± 0.02 for NGC 5128, and the dispersion in metallicity is ∼0.77 dex for both observed and simulated galaxies. We investigate the origin of the stars ending up in the outer halo field of simulated galaxies and show that most have an “accreted” origin, formed in other small galaxies and later accreted in mergers. Only ∼15% of the stars are formed in situ within the main progenitor of the galaxy and radially migrate outward. We show that the contribution of metal-rich in situ stars is subdominant in the outer halos of our simulated galaxies but can be prominent in the inner regions.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The pseudospectral method is a highly accurate numerical scheme suitable for turbulence simulations. We have developed an open-source pseudospectral code, <jats:sc>calliope</jats:sc>, which adopts the P3DFFT library to perform a fast Fourier transform with the two-dimensional (pencil) decomposition of numerical grids. <jats:sc>calliope</jats:sc> can solve incompressible magnetohydrodynamics (MHD), isothermal compressible MHD, and rotational reduced MHD with parallel computation using very large numbers of cores (&gt;10<jats:sup>5</jats:sup> cores for 2048<jats:sup>3</jats:sup> grids). The code can also solve for local magnetorotational turbulence in a shearing frame using the remapping method. <jats:sc>calliope</jats:sc> is currently the only pseudospectral code that can compute magnetorotational turbulence using pencil-domain decomposition. This paper presents the numerical scheme of <jats:sc>calliope</jats:sc> and the results of linear and nonlinear numerical tests, including compressible local magnetorotational turbulence with the largest grid number reported to date.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We revisit the eccentric neutron star (NS)–white dwarf (WD) binary model for the periodic activity of fast radio burst (FRB) sources, by including the effects of gravitational-wave (GW) radiation. In this model, the WD fills its Roche lobe at the periastron and mass transfer occurs from the WD to the NS. The accreted materials can be fragmented and arrive at the NS episodically, resulting in multiple bursts through curvature radiation. Consequently, the WD may be kicked away owing to the conservation of angular momentum. To initiate the next mass transfer, the WD has to refill its Roche lobe through GW radiation. In this scenario, whether the periodic activity can show up relies on three timescales, i.e., the orbital period <jats:italic>P</jats:italic> <jats:sub>orb</jats:sub>, the timescale <jats:italic>T</jats:italic> <jats:sub>GW</jats:sub> for the Roche lobe to be refilled, and the time span <jats:italic>T</jats:italic> <jats:sub>frag</jats:sub> for all the episodic events corresponding to each mass-transfer process. Only when the two conditions <jats:italic>T</jats:italic> <jats:sub>GW</jats:sub> ≲ <jats:italic>P</jats:italic> <jats:sub>orb</jats:sub> and <jats:italic>T</jats:italic> <jats:sub>frag</jats:sub> &lt; <jats:italic>P</jats:italic> <jats:sub>orb</jats:sub> are both satisfied, the periodic activity will manifest itself and the period should be equal to <jats:italic>P</jats:italic> <jats:sub>orb</jats:sub>. In this spirit, the periodic activity is more likely to show up for relatively long periods (<jats:italic>P</jats:italic> <jats:sub>orb</jats:sub> ≳ several days). Thus, it is reasonable that FRBs 180916 and 121102, the only two sources having been claimed to manifest periodic activity, both correspond to relatively long periods.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this paper, we fit the spectral energy distributions of iPTF 16asu, which has so far been classified as a luminous rapidly evolving broad-lined Ic supernova (SN Ic-BL), and reconstruct its postpeak bolometric light curve. We find that the luminosity of the postpeak bolometric light curve of iPTF 16asu is about 3 times that of the pseudobolometric light curve derived in the literature, and the extrapolated peak luminosity exceeds ∼10<jats:sup>44</jats:sup> erg s<jats:sup>−1</jats:sup>, which is higher than the threshold of superluminous supernovae (SLSNe). We then use the <jats:sup>56</jats:sup>Ni model and the magnetar plus <jats:sup>56</jats:sup>Ni model to fit the multiband light curves of iPTF 16asu, and construct the theoretical bolometric light curve using the best-fitting theoretical multiband light curves. We find that the magnetar plus <jats:sup>56</jats:sup>Ni model can account for the photometry of iPTF 16asu, and the peak luminosity of its theoretical bolometric light curve is ∼1.06 × 10<jats:sup>44</jats:sup> erg s<jats:sup>−1</jats:sup>. We suggest that iPTF 16asu and similar SNe (e.g., SN 2018gep) constitute the class of rapidly evolving SLSNe Ic-BL.</jats:p>