Related papers: High NH2D/NH3 ratios in protostellar cores
The total deuterium abundance [D/H] in the universe is set by just two processes: the creation of deuterium in Big Bang Nucleosynthesis at an abundance of [D/H]$=2.58\pm0.13\times10^{-5}$, and its destruction within stellar interiors.…
IRAS 16293-2422 is a well studied low-mass protostar characterized by a strong level of deuterium fractionation. In the line of sight of the protostellar envelope, an additional absorption layer, rich in singly and doubly deuterated water…
We determine the ortho/para ratios of NH2D and NHD2 in two dense, starless cores, where their formation is supposed to be dominated by gas-phase reactions, which, in turn, is predicted to result in deviations from the statistical spin…
Deuterated interstellar molecules frequently have abundances relative to their main isotopologues much higher than the overall elemental D-to-H ratio in the cold dense interstellar medium. The H$_3^+$ and its isotopologues play a key role…
We have studied the evolution of molecular gas during the early stages of protostellar collapse. In addition to allowing for the freeze out of `heavy' species on to grains, we have computed the variation of population densities of the…
We present the results of on-the-fly mapping observations of 44 fields containing 107 SCUBA-2 cores in the emission lines of molecules, N$_2$H$^+$, HC$_3$N, and CCS at 82$-$94 GHz using the Nobeyama 45-m telescope. This study aimed at…
We have investigated the evolution and distribution of molecules in collapsing prestellar cores via numerical chemical models, adopting the Larson-Penston solution and its delayed analogues to study collapse. Molecular abundances and…
Seven isolated, nearby low-mass starless molecular cloud cores have been observed as part of the Herschel key program Earliest Phases of Star formation (EPoS). By applying a ray-tracing technique to the obtained continuum emission and…
High deuterium fractionation is observed in various types of environment such as prestellar cores, hot cores and hot corinos. It has proven to be an efficient probe to study the physical and chemical conditions of these environments. The…
Deuterium fractionation processes in the interstellar medium (ISM) have been shown to be highly efficient in the family of nitrogen hydrides. To date, observations were limited to ammonia (NH$_2$D, NHD$_2$, ND$_3$) and imidogen radical (ND)…
Infrared-dark high-mass clumps are among the most promising objects to study the initial conditions of the formation process of high-mass stars and rich stellar clusters. In this work, we have observed the (3-2) rotational transition of…
The HDO/H2O ratio is a powerful diagnostic to understand the evolution of water from the first stages of star formation to the formation of planets and comets. Our aim is to determine precisely the abundance distribution of HDO towards the…
Pre-stellar cores are the first steps in the process of star and planet formation. However, the dynamical and chemical evolution of pre-stellar cores is still not well understood. We aim at estimating the central density of the pre-stellar…
Understanding the chemical processes during starless core and prestellar core evolution is an important step in understanding the initial stages of star and disk formation. This project is a study of deuterated ammonia, o-NH$_2$D, in the…
We have used archival FUSE data to complete a survey of interstellar HD in 41 lines of sight with a wide range of extinctions. This follow up to an earlier survey was made to further assess the utility of HD as a cosmological probe; to…
The isotopic ratios of deuterated methanol derived around protostars are commonly used to infer the physical conditions under which they formed in the earlier prestellar stage. However, there is a discrepancy in the ratio of the singly…
Supernova remnants (SNRs) may regulate star formation in galaxies. For example, SNR-driven shocks may form new molecular gas or compress pre-existing clouds and trigger the formation of new stars. To test this scenario, we measure the…
Chemical features of the local stellar disk have firmly established that long-term, continuous star formation has been accompanied by a steady rate of accretion of low-metallicity gas from the halo. We now argue that the recent discovery of…
Although chemical models predict that the deuterium fractionation in N$_2$H$^+$ is a good evolutionary tracer in the star formation process, the fractionation of nitrogen is still a poorly understood process. Recent models have questioned…
Sufficiently massive clumps of molecular gas collapse under self-gravity and fragment to spawn a cluster of stars that have a range of masses. We investigate observationally the early stages of formation of a stellar cluster in a massive…