Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>The turbulence in the diffuse intergalactic medium (IGM) plays an important role in various astrophysical processes across cosmic time, but it is very challenging to constrain its statistical properties both observationally and numerically. Via the statistical analysis of turbulence along different sight lines toward a population of fast radio bursts (FRBs), we demonstrate that FRBs provide a unique tool to probe the intergalactic turbulence. We measure the structure function (SF) of dispersion measures (DMs) of FRBs to study the multiscale electron density fluctuations induced by the intergalactic turbulence. The SF has a large amplitude and a Kolmogorov power-law scaling with angular separations, showing large and correlated DM fluctuations over a range of length scales. Given that the DMs of FRBs are IGM dominated, our result tentatively suggests that the intergalactic turbulence has a Kolmogorov power spectrum and an outer scale on the order of 100 Mpc.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Phosphine (PH<jats:sub>3</jats:sub>), an important molecule for the chemistry of phosphorus (P)-bearing species in the interstellar medium (ISM) is considered to form primarily on interstellar grains. However, no report exists on the processes of PH<jats:sub>3</jats:sub> formation on grains. Here, we experimentally studied the reactions of hydrogen (H) atoms and PH<jats:sub>3</jats:sub> molecules on compact amorphous solid water, with a particular focus on the chemical desorption of PH<jats:sub>3</jats:sub> at 10–30 K. After exposure to H atoms for 120 minutes, up to 50% of solid PH<jats:sub>3</jats:sub> was lost from the icy surface. On the basis of experiments using deuterium atoms, it was concluded that the loss of PH<jats:sub>3</jats:sub> resulted from chemical desorption through the reactions PH<jats:sub>3</jats:sub> + H → PH<jats:sub>2</jats:sub> + H<jats:sub>2</jats:sub> and/or PH<jats:sub>2</jats:sub> + H → PH<jats:sub>3</jats:sub>. The effective desorption cross-section was ∼5 × 10<jats:sup>−17</jats:sup> cm<jats:sup>2</jats:sup>, which is three times larger than that of hydrogen sulfide measured under similar experimental conditions. The present results suggest that the formation of PH<jats:sub>3</jats:sub>, and possibly PH<jats:sub>2</jats:sub> and PH, followed by their desorption from icy grains, may contribute to the formation of PN and PO in the gas phase, and thus may play a role in the P chemistry of the ISM.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Galactic cosmic rays (GCRs) are highly energetic particles that can have significant effects on the atmospheres and potentially also surfaces of (exo)planets and moons. Their propagation through the Sun’s heliosphere and their interaction with planetary bodies have been widely studied in the solar system (e.g., Earth, Mars, Venus, and Europa). There is currently much interest in exoplanetary science, particularly in terms of characterizing the potential habitability of exoplanetary environments. As a consequence of this, models have been developed to quantify the effect of GCRs on exoplanet systems. However, many such studies assume Earth-like (1 au) GCR fluxes. Here we will demonstrate why this is not a reasonable assumption. We briefly discuss the journey that GCRs make from their birth to the arrival at an exoplanet, and discuss the various implications this will have on GCR fluxes. We demonstrate the importance of understanding the specific local interstellar medium (ISM) that an exoplanetary system resides within, as this determines the size of the astrosphere of the host star. This has strong implications for the modulation of GCR fluxes throughout an astrosphere. We estimate how GCR proton fluxes at 1 au (from the Sun) would be different from current values if the solar system was embedded in a different ISM environment. Furthermore, we provide estimates of the wide range of possible GCR proton fluxes at the exoplanets Kepler-20f and Kepler-88c using previously published estimates for the local ISM parameters at these bodies.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The first interstellar object observed in our solar system, 1I/2017 U1 (‘Oumuamua), exhibited a number of peculiar properties, including extreme elongation and acceleration excess. Recently, Seligman &amp; Laughlin proposed that the object was made out of molecular hydrogen (H<jats:sub>2</jats:sub>) ice. The question is whether H<jats:sub>2</jats:sub> objects could survive their travel from the birth sites to the solar system. Here we study destruction processes of icy H<jats:sub>2</jats:sub> objects through their journey from giant molecular clouds (GMCs) to the interstellar medium (ISM) and the solar system, owing to interstellar radiation, gas and dust, and cosmic rays. We find that thermal sublimation due to heating by starlight can destroy ‘Oumuamua-size objects in less than 10 Myr. Thermal sublimation by collisional heating in GMCs could destroy H<jats:sub>2</jats:sub> objects of ‘Oumuamua-size before their escape into the ISM. Most importantly, the formation of icy grains rich in H<jats:sub>2</jats:sub> is unlikely to occur in dense environments because collisional heating raises the temperature of the icy grains, so that thermal sublimation rapidly destroys the H<jats:sub>2</jats:sub> mantle before grain growth.</jats:p>