Scientific news

Molecular ions have long been considered key intermediates in the evolution of molecular complexity in the interstellar medium. However, owing to their reactivity and transient nature, ions have historically proved challenging to study in terrestrial laboratory experiments. In turn, their detection and characterization in space is often contingent upon advances in the laboratory spectroscopic techniques used to measure their spectra. In this Review, we discuss the advances over the past 50 years in laboratory methodologies for producing molecular ions and probing their rotational, vibrational and electronic spectra. We largely focus this discussion around the widespread H₃⁺ cation and the ionic products originating from its reaction with carbon atoms. Finally, we discuss the current frontiers in this research and the technical advances required to address the spectroscopic challenges that they represent.

Nature Reviews Physics

We present numerical simulations of molecular clouds formation including the chemical evolution of H2 and CO. We discuss the spatial resolution required to obtain numerically converged chemical abundances.

https://doi.org/10.1093/mnras/stz052

We present dust polarisation radiative transfer simulations obtained with POLARIS of simulations of magnetised molecular clouds. We discuss the accuracy of actual polarisation observations and the origin of depolarisation in molecular clouds.

https://doi.org/10.1093/mnras/sty2831

We present molecular cloud simulations including radiative stellar feedback. We discuss the reduction of the star formation efficiency and the dispersal of molecular clouds due to stellar feedback.

https://doi.org/10.1093/mnras/sty2938

To date, infrared interferometry at best achieved contrast ratios of a few times 10−4 on bright targets. GRAVITY, with its dual-field mode, is now capable of high contrast observations, enabling the direct observation of exoplanets. We demonstrate the technique on HR 8799, a young planetary system composed of four known giant exoplanets.

https://doi.org/10.1051/0004-6361/201935253

We measure for the first time the overall extent within which stars in distant galaxies were born. At all cosmic epochs, star formation in massive galaxies preferentially takes place in their central region, indicating that we are witnessing the final assembly of their stellar bulges. Few galaxies have a more compact star-forming extent, and all of them produce stars at a much higher rate than the average. This suggests a different mechanism triggering their star formation activities, such as the merger of two gas-rich disks.

https://doi.org/10.1051/0004-6361/201935178

The IRAM/GISMO 2 millimeter survey in the COSMOS field provides a unique view on star formation at the time when the Universe was only two billion years old. It reveals a significant population of extreme galaxies. Compared to the Milky-Way, they are about three times more massive, and form about 1000 times more stars per year. The sheer existence of these galaxies, soon after the Big-Bang, challenges current galaxy formation models.

https://iopscience.iop.org/article/10.3847/1538-4357/ab1912

This article reports the interstellar detection of urea. The detection was made possible thanks to a new, sensitive spectral line survey carried out with ALMA toward the high-mass star-forming region Sgr B2(N).

https://arxiv.org/abs/1906.04614

This article analyzes the chemical composition of a sample of hot molecular cores detected with ALMA in the high-mass star forming region Sgr B2(N). It shows that a cosmic-ray ionization rate enhanced by a factor 50 best reproduces the observed abundance ratios of various complex organic molecules.

https://arxiv.org/abs/1906.04695

The low-frequency stretching and bending vibrations of the isotopologues  and  have been recorded at low temperature and low resolution. For this, a cryogenic 22-pole trapping machine coupled to an IR beamline of the FELIX free electron laser facility has been used. To record the overview spectra, the laser induced reactions have been applied for these species. As this scheme is not applicable to , the latter has been tagged with He and subsequently dissociated by the IR beam. For the resulting - spectrum, broad features are observed below 1000 possibly related to vibrational motions involving the He atom. The extracted vibrational band positions for all species are compared to results from high-level quantum-chemical calculations.

https://doi.org/10.1016/j.jms.2018.02.006