Related papers: Adenine Abundance in a Collapsing Molecular Cloud

A dense cloud of atoms with randomly changing positions exhibits coherent and incoherent scattering. We show that an atomic cloud of subwavelength dimensions can be modeled as a single scatterer where both coherent and incoherent components…

The past decade has led to significant improvements in our understanding of the physical structure of the molecular cores of cold dark clouds. Observational efforts, in combination with improved knowledge of cloud structure, now provide…

One of the key problems in star formation research is to determine the role of magnetic fields. Starting from the atomic inter-cloud medium (ICM) which has density nH ~ 1 per cubic cm, gas must accumulate from a volume several hundred pc…

The bulk composition of the Earth is dramatically carbon poor compared to that of the interstellar medium, and this phenomenon extends to the asteroid belt. To interpret this carbon deficit problem, the carbonaceous component in grains must…

Protoplanetary disks, debris disks, and disrupted or evaporating planets can all feed accretion onto stars. The photospheric abundances of such stars may then reveal the composition of the accreted material. This is especially likely in B…

Using self-gravitational hydrodynamical numerical simulations, we investigated the evolution of high-density turbulent molecular clouds swept by a colliding flow. The interaction of shock waves due to turbulence produces networks of thin…

Astrochemistry lies at the nexus of astronomy, chemistry, and molecular physics. On the basis of precise laboratory data, a rich collection of more than 200 familiar and exotic molecules have been identified in the interstellar medium, the…

Atomic collapse is a phenomenon inherent to relativistic quantum mechanics where electron states dive in the positron continuum for highly charged nuclei. This phenomenon was recently observed in graphene. Here we investigate a novel…

Stars and more particularly massive stars, have a drastic impact on galaxy evolution. Yet the conditions in which they form and collapse are still not fully understood. In particular, the influence of the magnetic field on the collapse of…

We present a novel method to characterize dust depletion, namely, the depletion of metals into dust grains. We used observed correlations among relative abundances combining a total of 17 metals in diverse galactic environments, including…

The density of cosmic rays inside molecular clouds determines the ionization rate in the dense cores where stars form. It is also one of the drivers of astrochemistry leading to the creation of complex molecules. Through Fermi Large Area…

We present observations of 25 transitions of 17 isotopologues of 9 molecules toward B335. With a goal of constraining chemical models of collapsing clouds, we compare our observations, along with data from the literature, to models of…

We study the hypothesis of high metallicity clumps being responsible for the abundance discrepancy found in planetary nebulae between the values obtained from recombination and collisionaly excited lines. We generate grids of…

We investigate the role of ambipolar diffusion (AD) in collisions between magnetized giant molecular clouds (GMCs), which may be an important mechanism for triggering star cluster formation. Three dimensional simulations of GMC collisions…

While the best tracer of the molecular component and its dynamics in galaxies is the CO molecule, which excitation is revealed by its isotopic and (2-1)/(1-0) ratios, the denser gas is revealed by molecules such as HCN, HNC, HCO+ or CN,…

Using archival, high-resolution far-ultraviolet HST/STIS spectra of 34 Galactic O and B stars, we measure CI column densities and compare them with measurements from the literature of CO and H_2 with regard to understanding the presence of…

For a molecular cloud clump to form stars some transport of magnetic flux is required from the denser, inner regions to the outer regions of the cloud, otherwise this can prevent the collapse. Fast magnetic reconnection which takes place in…

We present a tutorial on the determination of the physical conditions and chemical abundances in gaseous nebulae. We also include a brief review of recent results on the study of gaseous nebulae, their relevance for the study of stellar…

We present chemical abundances of carbon (C) and oxygen (O) in the Large and Small Magellanic Clouds from deep and high-quality optical spectra of HII regions. The data have been taken using the Ultraviolet-Visual Echelle Spectrograph at…

Molecular clouds often exhibit filamentary or sheet-like shapes. We compute the free-fall time ($\tff$) for finite, uniform, self-gravitating circular sheets and filamentary clouds of small but finite thickness, so that their volume density…