M. Padovani

COSMIC-RAY AND X-RAY HEATING OF INTERSTELLAR CLOUDS AND PROTOPLANETARY DISKS

Cosmic-ray and X-ray heating are derived from the electron energy-loss calculations of Dalgarno, Yan, and Liu for hydrogen-helium gas mixtures. These authors treated the heating from elastic scattering and collisional de-excitation of rotationally excited hydrogen molecules. Here we consider the heating that can arise from all ionization and excitation processes, with particular emphasis on the reactions of cosmic-ray and X-ray generated ions with the heavy neutral species, which we refer to as chemical heating. In molecular regions, chemical heating dominates and can account for 50% of the energy expended in the creation of an ion pair. The heating per ion pair ranges in the limit of negligible electron fraction from ~4.3 eV for diffuse atomic gas to ~13 eV for the moderately dense regions of molecular clouds and to ~18 eV for the very dense regions of protoplanetary disks. An important general conclusion of this study is that cosmic-ray and X-ray heating depends on the physical properties of the medium, i.e., on the molecular and electron fractions, the total density of hydrogen nuclei, and, to a lesser extent, on the temperature. It is also noted that chemical heating, the dominant process for cosmic-ray and X-ray heating, plays a role in UV irradiated molecular gas.

The CN/C15N isotopic ratio towards dark clouds

Understanding the origin of the composition of solar system cosmomaterials is a central question, not only in the cosmochemistry and astrochemistry fields, and requires various approaches to be combined. Measurements of isotopic ratios in cometary materials provide strong constraints on the content of the protosolar nebula. Their relation with the composition of the parental dark clouds is, however, still very elusive. In this paper, we bring new constraints based on the isotopic composition of nitrogen in dark clouds, with the aim of understanding the chemical processes that are responsible for the observed isotopic ratios. We have observed and detected the fundamental rotational transition of C

The role of cosmic rays on magnetic field diffusion and the formation of protostellar discs

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INTERSTELLAR DUST CHARGING IN DENSE MOLECULAR CLOUDS: COSMIC RAY EFFECTS

N towards two starless dark clouds, L1544 and L1498. We were able to derive the column density ratio of C

Herschel Finds Evidence for Stellar Wind Particles in a Protostellar Envelope: Is This What Happened to the Young Sun?

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Protostars: Forges of cosmic rays?

N over

Cosmic-ray acceleration in young protostars

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THE IMPORTANCE OF THE MAGNETIC FIELD FROM AN SMA-CSO-COMBINED SAMPLE OF STAR-FORMING REGIONS

CN towards the same clouds, and obtain the CN/C

Cosmic-Ray Propagation in Molecular Clouds

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Resolving the Polarized Dust Emission of the Disk around the Massive Star Powering the HH 80–81 Radio Jet

N isotopic ratios, which were found to be