Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>The principle of the background-eliminated extinction-parallax (BEEP) method is examining the extinction difference between on- and off-cloud regions to reveal the extinction jump caused by molecular clouds, thereby revealing the distance in complex dust environments. The BEEP method requires high-quality images of molecular clouds and high-precision stellar parallaxes and extinction data, which can be provided by the Milky Way Imaging Scroll Painting (MWISP) CO survey and the Gaia DR2 catalog, as well as supplementary <jats:italic>A</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub> extinction data. In this work, the BEEP method is further improved (BEEP-II) to measure molecular cloud distances in a global search manner. Applying the BEEP-II method to three regions mapped by the MWISP CO survey, we collectively measured 238 distances for 234 molecular clouds. Compared with previous BEEP results, the BEEP-II method measures distances efficiently, particularly for those molecular clouds with large angular size or in complicated environments, making it suitable for distance measurements of molecular clouds in large samples.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We study dynamical friction in the Newtonian regime of nonlocal gravity (NLG), which is a classical nonlocal generalization of Einstein’s theory of gravitation. The nonlocal aspect of NLG simulates dark matter. The attributes of the resulting effective dark matter are described and the main physical predictions of NLG, which has a characteristic length scale of order 1 kpc, for galactic dynamics are presented. Within the framework of NLG, we derive the analog of Chandrasekhar’s formula for dynamical friction. The astrophysical implications of the results for the apparent rotation of a central bar subject to dynamical friction in a barred spiral galaxy are briefly discussed.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present a generic mechanism for the thermal damping of compressive waves in the interstellar medium (ISM), occurring due to radiative cooling. We solve for the dispersion relation of magnetosonic waves in a two-fluid (ion-neutral) system in which density- and temperature-dependent heating and cooling mechanisms are present. We use this dispersion relation, in addition to an analytic approximation for the nonlinear turbulent cascade, to model dissipation of weak magnetosonic turbulence. We show that in some ISM conditions, the cutoff wavelength for magnetosonic turbulence becomes tens to hundreds of times larger when the thermal damping is added to the regular ion-neutral damping. We also run numerical simulations, which confirm that this effect has a dramatic impact on cascade of compressive wave modes.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Recent observations have detected excess H<jats:italic>α</jats:italic> emission from young stellar systems with an age of several Myr such as PDS 70. One-dimensional radiation-hydrodynamic models of shock-heated flows that we developed previously demonstrate that planetary accretion flows of &gt;a few ten km s<jats:sup>−1</jats:sup> can produce H<jats:italic>α</jats:italic> emission. It is, however, a challenge to understand the accretion process of proto-giant planets from observations of such shock-originated emission because of a huge gap in scale between the circumplanetary disk (CPD) and the microscopic accretion shock. To overcome the scale gap problem, we combine two-dimensional, high-spatial-resolution global hydrodynamic simulations and the one-dimensional local radiation-hydrodynamic model of the shock-heated flow. From such combined simulations for the protoplanet–CPD system, we find that the H<jats:italic>α</jats:italic> emission is mainly produced in localized areas on the protoplanetary surface. The accretion shocks above the CPD produce much weaker H<jats:italic>α</jats:italic> emission (approximately one to two orders of magnitude smaller in luminosity). Nevertheless, the accretion shocks above the CPD significantly affect the accretion process onto the protoplanet. The accretion occurs at a quasi-steady rate if averaged on a 10 day timescale, but its rate shows variability on shorter timescales. The disk surface accretion layers including the CPD shocks largely fluctuate, which results in the time-variable accretion rate and H<jats:italic>α</jats:italic> luminosity of the protoplanet. We also model the spectral emission profile of the H<jats:italic>α</jats:italic> line and find that the line profile is less time-variable despite the large variability in luminosity. High-spectral-resolution spectroscopic observation and monitoring will be key to revealing the property of the accretion process.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Cosmic-ray transport on galactic scales depends on the detailed properties of the magnetized, multiphase interstellar medium (ISM). In this work, we postprocess a high-resolution TIGRESS magnetohydrodynamic simulation modeling a local galactic disk patch with a two-moment fluid algorithm for cosmic-ray transport. We consider a variety of prescriptions for the cosmic rays, from a simple, purely diffusive formalism with constant scattering coefficient, to a physically motivated model in which the scattering coefficient is set by the critical balance between streaming-driven Alfvén wave excitation and damping mediated by local gas properties. We separately focus on cosmic rays with kinetic energies of ∼1 GeV (high-energy) and ∼30 MeV (low energy), respectively important for ISM dynamics and chemistry. We find that simultaneously accounting for advection, streaming, and diffusion of cosmic rays is crucial for properly modeling their transport. Advection dominates in the high-velocity, low-density hot phase, while diffusion and streaming are more important in higher-density, cooler phases. Our physically motivated model shows that there is no single diffusivity for cosmic-ray transport: the scattering coefficient varies by four or more orders of magnitude, maximal at density <jats:italic>n</jats:italic> <jats:sub>H</jats:sub> ∼ 0.01 cm<jats:sup>−3</jats:sup>. The ion-neutral damping of Alfvén waves results in strong diffusion and nearly uniform cosmic-ray pressure within most of the mass of the ISM. However, cosmic rays are trapped near the disk midplane by the higher scattering rate in the surrounding lower-density, higher-ionization gas. The transport of high-energy cosmic rays differs from that of low-energy cosmic rays, with less effective diffusion and greater energy losses for the latter.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present spatially resolved Hubble Space Telescope grism spectroscopy of 15 galaxies at <jats:italic>z</jats:italic> ∼ 0.8 drawn from the DEEP2 survey. We analyze H<jats:italic>α</jats:italic>+[N <jats:sc>ii</jats:sc>], [S <jats:sc>ii</jats:sc>], and [S <jats:sc>iii</jats:sc>] emission on kiloparsec scales to explore which mechanisms are powering emission lines at high redshifts, testing which processes may be responsible for the well-known offset of high-redshift galaxies from the <jats:italic>z</jats:italic> ∼ 0 locus in the [O <jats:sc>iii</jats:sc>]/H<jats:italic>β</jats:italic> versus [N <jats:sc>ii</jats:sc>]/H<jats:italic>α</jats:italic> Baldwin—Phillips—Terlevich (BPT) excitation diagram. We study spatially resolved emission-line maps to examine evidence for active galactic nuclei (AGN), shocks, diffuse ionized gas (DIG), or escaping ionizing radiation, all of which may contribute to the BPT offsets observed in our sample. We do not find significant evidence of AGN in our sample and quantify that, on average, AGN would need to contribute ∼25% of the H<jats:italic>α</jats:italic> flux in the central resolution element in order to cause the observed BPT offsets. We find weak (2<jats:italic>σ</jats:italic>) evidence of DIG emission at low surface brightnesses, yielding an implied total DIG emission fraction of ∼20%, which is not significant enough to be the dominant emission line driver in our sample. In general we find that the observed emission is dominated by star-forming H <jats:sc>ii</jats:sc> regions. We discuss trends with demographic properties and the possible role of <jats:italic>α</jats:italic>-enhanced abundance patterns in the emission spectra of high-redshift galaxies. Our results indicate that photoionization modeling with stellar population synthesis inputs is a valid tool to explore the specific star formation properties which may cause BPT offsets, to be explored in future work.</jats:p>