We present an overview of the first data release (DR1) and first-look science from the Green Bank Ammonia Survey (GAS). GAS is a Large Program at the Green Bank Telescope to map all Gould Belt star-forming regions with A V 7 mag visible from the northern hemisphere in emission from NH 3 and other key molecular tracers. This first release includes the data for four regions in Gould Belt clouds: B18 in Taurus, NGC 1333 in Perseus, L1688 in Ophiuchus, and Orion A North in Orion. We compare the NH 3 emission to dust continuum emission from Herschel, and find that the two tracers correspond closely. NH 3 is present in over 60 % of lines-of-sight with A V 7 mag in three of the four DR1 regions, in agreement with expectations from previous observations. The sole exception is B18, where NH 3 is detected toward ∼ 40 % of lines-of-sight with A V 7 mag. Moreover, we find that the NH 3 emission is generally extended beyond the typical 0.1 pc length scales of dense cores. We produce maps of the gas kinematics, temperature, and NH 3 column densities through forward modeling of the hyperfine structure of the NH 3 (1,1) and (2,2) lines. We show that the NH 3 velocity dispersion, σ v , and gas kinetic temperature, T K , vary systematically between the regions included in this release, with an increase in both the mean value and spread of σ v and T K with increasing star formation activity. The data presented in this paper are publicly available.

We use gas temperature and velocity dispersion data from the Green Bank Ammonia Survey and core masses and sizes from the James Clerk Maxwell Telescope Gould Belt Survey to estimate the virial states of dense cores within the Orion A molecular cloud. Surprisingly, we find that almost none of the dense cores are sufficiently massive to be bound when considering only the balance between selfgravity and the thermal and non-thermal motions present in the dense gas. Including the additional pressure binding imposed by the weight of the ambient molecular cloud material and additional smaller pressure terms, however, suggests that most of the dense cores are pressure confined.

Complex organic molecules have been observed for decades in the interstellar medium. Some of them might be considered as small bricks of the macromolecules at the base of terrestrial life. It is hence particularly important to understand organic chemistry in Solar-like star-forming regions. In this article, we present a new observational project: Seeds Of Life In Space (SOLIS). This is a Large Project using the IRAM-NOEMA interferometer, and its scope is to image the emission of several crucial organic molecules in a sample of Solar-like star-forming regions in different evolutionary stages and environments. Here we report the first SOLIS results, obtained from analyzing the spectra of different regions of the Class 0 source NGC 1333-IRAS4A, the protocluster OMC-2 FIR4, and the shock site L1157-B1. The different regions were identified based on the images of formamide (NH 2 CHO) and cyanodiacetylene (HC 5 N) lines. We discuss the observed large diversity in the molecular and organic content, both on large (3000-10,000 au) and relatively small (300-1000 au) scales. Finally, we derive upper limits to the methoxy fractional abundance in the three observed regions of the same order of magnitude of that measured in a few cold prestellar objects, namely 10 12 --10 −11 with respect to H 2 molecules.

Context. Ammonia and its deuterated isotopologues probe physical conditions in dense molecular cloud cores. The time-dependence of deuterium fractionation and the relative abundances of different nuclear spin modifications are supposed to provide means of determining the evolutionary stages of these objects. Aims. We aim to test the current understanding of spin-state chemistry of deuterated species by determining the abundances and spin ratios of NH 2 D, NHD 2 , and ND 3 in a quiescent, dense cloud. Methods. Spectral lines of NH 3 , NH 2 D, NHD 2 , ND 3 , and N 2 D + were observed towards a dense, starless core in Ophiuchus with the APEX, GBT, and IRAM 30-m telescopes. The observations were interpreted using a gas-grain chemistry model combined with radiative transfer calculations. The chemistry model distinguishes between the different nuclear spin states of light hydrogen molecules, ammonia, and their deuterated forms. Different desorption schemes can be considered. Results. High deuterium fractionation ratios with NH 2 D/NH 3 ∼ 0.4, NHD 2 /NH 2 D ∼ 0.2, and ND 3 /NHD 2 ∼ 0.06 are found in the core. The observed ortho/para ratios of NH 2 D and NHD 2 are close to the corresponding nuclear spin statistical weights. The chemistry model can approximately reproduce the observed abundances, but predicts uniformly too low ortho/para-NH 2 D, and too large ortho/para-NHD 2 ratios. The longevity of N 2 H + and NH 3 in dense gas, which is prerequisite to their strong deuteration, can be attributed to the chemical inertia of N 2 on grain surfaces. Conclusions. The discrepancies between the chemistry model and the observations are likely to be caused by the fact that the model assumes complete scrambling in principal gas-phase deuteration reactions of ammonia, which means that all the nuclei are mixed in reactive collisions. If, instead, these reactions occur through proton hop/hydrogen abstraction processes, statistical spin ratios are to be expected. The present results suggest that while the deuteration of ammonia changes with physical conditions and time, the nuclear spin ratios of ammonia isotopologues do not probe the evolutionary stage of a cloud.

The interstellar delivery of carbon atoms locked into molecules might be one of the key ingredients for the emergence of life. Cyanopolyynes are carbon chains delimited at their two extremities by an atom of hydrogen and a cyano group, meaning that they could be excellent reservoirs of carbon. The simplest member, HC 3 N, is ubiquitous in the galactic interstellar medium and found also in external galaxies. Thus, understanding the growth of cyanopolyynes in regions forming stars similar to our Sun, and what affects them, is particularly relevant. In the framework of the IRAM/NOEMA Large Program SOLIS (Seeds Of Life In Space), we have obtained a map of two cyanopolyynes, HC 3 N and HC 5 N, in the protocluster OMC-2 FIR4. Because our Sun is thought to be born in a rich cluster, OMC-2 FIR4 is one of the closest and best known representatives of the environment in which the Sun may have been born. We find a HC 3 N/HC 5 N abundance ratio across the source in the range ∼1−30, with the smallest values (≤10) in FIR5 and in the eastern region of FIR4. The ratios ≤10 can be reproduced by chemical models only if: (1) the cosmic-ray ionisation rate ζ is ∼4 × 10 −14 s −1 ; (2) the gaseous elemental ratio C/O is close to unity; and (3) oxygen and carbon are largely depleted. The large ζ is comparable to that measured in FIR4 by previous works and was interpreted as due to a flux of energetic (≥10 MeV) particles from embedded sources. We suggest that these sources could lie east of FIR4 and FIR5. A temperature gradient across FIR4, with T decreasing from east to west by about 10 K, could also explain the observed change in the HC 3 N/HC 5 N line ratio, without the need of a cosmic ray ionisation rate gradient. However, even in this case, a high constant cosmic-ray ionisation rate (of the order of 10 −14 s −1) is necessary to reproduce the observations.