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16 pags., 11 figs., 5 tabs. ; Context. The [C II] 158 μm fine-structure line is one of the dominant coolants of the neutral interstellar medium. It is hence one of the brightest far-infrared (FIR) emission lines and can be observed not only in star-forming regions throughout the Galaxy, but also in the diffuse interstellar medium and in distant galaxies. [C II] line emission has been suggested to be a powerful tracer of star formation. Aims. We aim to understand the origin of [C II] emission and its relation to other tracers of interstellar gas and dust. This includes a study of the heating efficiency of interstellar gas as traced by the [C II] line to test models of gas heating. Methods. We made use of a one-square-degree map of velocity-resolved [C II] line emission toward the Orion Nebula complex, including M 43 and NGC 1977. We employed Herschel FIR photometric images to determine dust properties. Moreover, we compared with Hα emission from the ionized gas, Spitzer mid-infrared photometry to trace hot dust and large polycyclic aromatic hydrocarbons (PAHs), and velocity-resolved IRAM 30m CO(2-1) observations of the molecular gas. Results. The [C II] intensity is tightly correlated with PAH emission in the IRAC 8 μm band and FIR emission from warm dust. However, the [C II] intensity depends less than linearly on the 8 μm and FIR intensity, while 8 μm and FIR intensities are approximately linearly correlated. The correlation between [C II] and CO(2-1) does not show a clear trend and is affected by the detailed geometry of the region. We find particularly low [C II]-over-FIR intensity ratios toward large columns of (warm and cold) dust, which suggest the interpretation of the "[C II] deficit"in terms of a "FIR excess". Conclusions. In terms of the [C II] deficit, we find clear evidence in our data for the importance of [O I] 63 μm emission in the photodissociation regions (PDRs) associated with the Huygens region. A smaller contribution is made by a decreased heating efficiency in regions of high UV irradiation. FIR emission from deeply embedded protostars leads to palpably deficient [C II]/FIR intensity ratios. The [C II] directly associated with the M 42, M 43, and NGC 1977 regions underestimates the star formation rate derived from extragalactic scaling relations. We ascribe this to the importance of [C II] emission from low surface brightness PDR surfaces of molecular clouds which are not included in our survey. Future studies of more active regions of massive star formation will be instrumental in validating the general applicability of these conclusions. ; This work is based on observations made with the NASA/DLR Stratospheric Observatory for Infrared Astronomy (SOFIA). SOFIA is jointly operated by the Universities Space Research Association, Inc. (USRA), under NASA contract NNA17BF53C, and the Deutsches SOFIA Institut (DSI) under DLR contract 50 OK 0901 to the University of Stuttgart. This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 851435). JRG thanks the Spanish MCIU for funding support under grants AYA2017-85111-P and PID2019-106110GB-I00. Research on the interstellar medium at Leiden Observatory is supported through a Spinoza award of the Dutch Science Organisation (NWO).

I. Tanarro et al. -- 16 pags., 18 figs., app. ; We present a proof of concept on the coupling of radio astronomical receivers and spectrometers with chemical reactors and the performances of the resulting setup for spectroscopy and chemical simulations in laboratory astrophysics. Several experiments including cold plasma generation and UV photochemistry were performed in a 40 cm long gas cell placed in the beam path of the Aries 40 m radio telescope receivers operating in the 41–49 GHz frequency range interfaced with fast Fourier transform spectrometers providing 2 GHz bandwidth and 38 kHz resolution. The impedance matching of the cell windows has been studied using di erent materials. The choice of the material and its thickness was critical to obtain a sensitivity identical to that of standard radio astronomical observations. Spectroscopic signals arising from very low partial pressures of CH3OH, CH3CH2OH, HCOOH, OCS, CS, SO2 (<103 mbar) were detected in a few seconds. Fast data acquisition was achieved allowing for kinetic measurements in fragmentation experiments using electron impact or UV irradiation. Time evolution of chemical reactions involving OCS, O2 and CS2 was also observed demonstrating that reactive species, such as CS, can be maintained with high abundance in the gas phase during these experiments ; The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013)/ERC-SyG-2013 Grant Agreement No. 610256 NANOCOSMOS and from spanish MINECO CSD2009-00038 (ASTROMOL) under the Consolider-Ingenio Program. We also thank spanish MINECO for funding under grants AYA2012-32032, AYA2016-75066-C2-1-P, FIS2013-48087-C2-1-P, FIS2016-77726-C3-1-P, FIS2016-77578-R, MAT2014- 54231-C4-1-P. ; Peer reviewed

According to recent market studies of the North American company Allied Market Research, the field of photonic sensors is an emerging strategic field for the following years and it is expected to garner $18 billion by 2021. The integration of micro and nanofabrication technologies in the field of sensors has allowed the development of new technological concepts such as lab-on-a-chip, which have achieved extraordinary advances in terms of detection and applicability, for example in the field of biosensors. This continuous development has allowed that equipment consisting of many complex devices that occupied a whole room a few years ago, at present it is possible to handle them in the palm of the hand; that formerly long duration processes are carried out in a matter of milliseconds and that a technology previously dedicated solely to military or scientific uses is available to the vast majority of consumers. The adequate combination of micro and nanostructured coatings with optical fiber sensors has permitted us to develop novel sensing technologies, such as the first experimental demonstration of lossy mode resonances (LMRs) for sensing applications, with more than one hundred citations and related publications in high rank journals and top conferences. In fact, fiber optic LMR-based devices have been proven as devices with one of the highest sensitivity for refractometric applications. Refractive index sensitivity is an indirect and simple indicator of how sensitive the device is to chemical and biological species, topic where this proposal is focused. Consequently, the utilization of these devices for chemical and biosensing applications is a clear opportunity that could open novel and interesting research lines and applications as well as simplify current analytical methodologies. As a result, on the basis of our previous experience with LMR based sensors to attain very high sensitivities, the objective of this paper is presenting the route for the development of label-free optical waveguide sensing platform ...

28 pags., 22 figs., 4 tabs. ; Gas phase Elemental abundances in Molecular CloudS (GEMS) is an IRAM 30 m Large Program designed to provide estimates of the S, C, N, and O depletions and gas ionization degree, X(e−), in a selected set of star-forming filaments of Taurus, Perseus, and Orion. Our immediate goal is to build up a complete and large database of molecular abundances that can serve as an observational basis for estimating X(e−) and the C, O, N, and S depletions through chemical modeling. We observed and derived the abundances of 14 species (13CO, C18O, HCO+, H13CO+, HC18O+, HCN, H13CN, HNC, HCS+, CS, SO, 34SO, H2S, and OCS) in 244 positions, covering the AV ~3 to ~100 mag, n(H2) ~ a few 103 to 106 cm−3, and Tk ~10 to ~30 K ranges in these clouds, and avoiding protostars, HII regions, and bipolar outflows. A statistical analysis is carried out in order to identify general trends between different species and with physical parameters. Relations between molecules reveal strong linear correlations which define three different families of species: (1) 13CO and C18O isotopologs; (2) H13CO+, HC18O+, H13 CN, and HNC; and (3) the S-bearing molecules. The abundances of the CO isotopologs increase with the gas kinetic temperature until TK ~ 15 K. For higher temperatures, the abundance remains constant with a scatter of a factor of ~3. The abundances of H13 CO+, HC18 O+, H13 CN, and HNC are well correlated with each other, and all of them decrease with molecular hydrogen density, following the law ∝ n(H2)−0.8 ± 0.2. The abundances of S-bearing species also decrease with molecular hydrogen density at a rate of (S-bearing/H)gas ∝ n(H2)−0.6 ± 0.1. The abundances of molecules belonging to groups 2 and 3 do not present any clear trend with gas temperature. At scales of molecular clouds, the C18O abundance is the quantity that better correlates with the cloud mass. We discuss the utility of the 13CO/C18O, HCO+/H13CO+, and H13 CO+/H13CN abundance ratios as chemical diagnostics of star formation in external galaxies. ; We thank the Spanish the Spanish Ministerio de Ciencia e Innovación for funding support through AYA2016-75066-C2-1/2-P and PID2019-106235GB-I00. SG-B acknowledges support through grants PGC2018-094671-B-I00 (MICIU/AEI/FEDER,UE) and PID2019-106027GAC44. JRG acknowledges support through grants AYA2017-85111-P and PID2019-106110GB-I00. I.J.-S. has received partial support from the Spanish FEDER (project number ESP2017-86582-C4-1-R) and the State Research Agency (AEI; project number PID2019-105552RB-C41). SPTM acknowledges to the European Union's Horizon 2020 research and innovation program for funding support given under grant agreement No 639459 (PROMISE). ; Peer reviewed

21 pags., 16 figs., 7 tabs., 2 apps. ; Context. Sulphur is one of the most abundant elements in the Universe. Surprisingly, sulphuretted molecules are not as abundant as expected in the interstellar medium and the identity of the main sulphur reservoir is still an open question. Aims. Our goal is to investigate the H2S chemistry in dark clouds, as this stable molecule is a potential sulphur reservoir. Methods. Using millimeter observations of CS, SO, H2S, and their isotopologues, we determine the physical conditions and H2S abundances along the cores TMC 1-C, TMC 1-CP, and Barnard 1b. The gas-grain model NAUTILUS is used to model the sulphur chemistry and explore the impact of photo-desorption and chemical desorption on the H2S abundance. Results. Our modeling shows that chemical desorption is the main source of gas-phase H2S in dark cores. The measured H2S abundance can only be fitted if we assume that the chemical desorption rate decreases by more than a factor of 10 when nH > 2 × 104. This change in the desorption rate is consistent with the formation of thick H2O and CO ice mantles on grain surfaces. The observed SO and H2S abundances are in good agreement with our predictions adopting an undepleted value of the sulphur abundance. However, the CS abundance is overestimated by a factor of 5-10. Along the three cores, atomic S is predicted to be the main sulphur reservoir. Conclusions. The gaseous H2S abundance is well reproduced, assuming undepleted sulphur abundance and chemical desorption as the main source of H2S. The behavior of the observed H2S abundance suggests a changing desorption efficiency, which would probe the snowline in these cold cores. Our model, however, highly overestimates the observed gas-phase CS abundance. Given the uncertainty in the sulphur chemistry, we can only conclude that our data are consistent with a cosmic elemental S abundance with an uncertainty of a factor of 10. ; We thank the Spanish MINECO for funding support from AYA2016-75066-C2-1/2-P, AYA2017-85111P, and ERC under ERC-2013-SyG, G. A. 610256 NANOCOSMOS. JM acknowledges the support of ERC-2015-STG No. 679852 RADFEEDBACK. S.P.T.M. acknowledge to the European Union's Horizon 2020 research and innovation program for funding support given under grant agreement No 639459 (PROMISE).

26 pags., 7 figs., 2 tabs., 2 apps. ; GEMS is an IRAM 30 m Large Program whose aim is determining the elemental depletions and the ionization fraction in a set of prototypical star-forming regions. This paper presents the first results from the prototypical dark cloud Taurus molecular cloud (TMC) 1. Extensive millimeter observations have been carried out with the IRAM 30 m telescope (3 and 2 mm) and the 40 m Yebes telescope (1.3 cm and 7 mm) to determine the fractional abundances of CO, HCO, HCN, CS, SO, HCS, and N H in three cuts which intersect the dense filament at the well-known positions TMC 1-CP, TMC 1-NH3, and TMC 1-C, covering a visual extinction range from A ~ 3 to ~20 mag. Two phases with differentiated chemistry can be distinguished: (i) the translucent envelope with molecular hydrogen densities of 1-5 × 10 cm; and (ii) the dense phase, located at A > 10 mag, with molecular hydrogen densities >10 cm. Observations and modeling show that the gas phase abundances of C and O progressively decrease along the C/C/CO transition zone (A~ 3 mag) where C/H ~ 8 × 10 and C/O ~ 0.8-1, until the beginning of the dense phase at A ~ 10 mag. This is consistent with the grain temperatures being below the CO evaporation temperature in this region. In the case of sulfur, a strong depletion should occur before the translucent phase where we estimate an S/ H ~ (0.4-2.2) × 10, an abundance ~7-40 times lower than the solar value. A second strong depletion must be present during the formation of the thick icy mantles to achieve the values of S/H measured in the dense cold cores (S H ~ 8 × 10) . Based on our chemical modeling, we constrain the value of ζ to ~(0.5-1.8) × 10 s in the translucent cloud. ; We thank the Spanish MINECO for funding support from AYA2016-75066-C2-1/2-P, and the ERC under ERC-2013-SyG, G. A. 610256 NANOCOSMOS. JM acknowledges the support of ERC-2015-STG No. 679852 RADFEEDBACK. SPTM acknowledges to the European Union's Horizon 2020 research and innovation program for funding support given under grant agreement No 639459 (PROMISE). RMD acknowledges support provided by an award from the Simons Foundation (SCOL#321183, KO). GMC acknowedges funding support fromAYA2017-85322-R. MT acknowledges partial support from project AYA2016-79006-P." ; Peer Reviewed