Browsing by Author "Goicoechea, J. R."

Now showing 1 - 6 of 6
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    Abundances of sulphur molecules in the Horsehead nebula First NS+ detection in a photodissociation region
    (2019) Riviere-Marichalar, P.; Fuente, A.; Goicoechea, J. R.; Pety, J.; Le Gal, R.; Gratier, P.; Guzman, V; Roueff, E.; Loison, J. C.; Wakelam, V; Gerin, M.
    Context. Sulphur is one of the most abundant elements in the Universe (S/H similar to 1.3 x 10(-5)) and plays a crucial role in biological systems on Earth. The understanding of its chemistry is therefore of major importance.
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    C18O, 13CO, and 12CO abundances and excitation temperatures in the Orion B molecular cloud : analysis of the achievable precision in modeling spectral lines within the approximation of the local thermodynamic equilibrium
    (2021) Roueff, A.; Gerin, M.; Gratier, P.; Levrier, F.; Pety, J.; Gaudel, M.; Goicoechea, J. R.; Orkisz, J. H.; De Souza Magalhaes, V.; Guzmán Veloso, Viviana Gabriela; Vono, M.; Bardeau, S.; Bron, E.; Chanussot, J.; Chainais, P.; Hughes, A.; Kainulainen, J.; Languignon, D.; Le Bourlot, J.; Le Petit, F.; Liszt, H. S.; Marchal, A.; Miville Deschênes, M. A.; Peretto, N.; Roueff, E.; Sievers, A.
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    HCN emission from translucent gas and UV-illuminated cloud edges revealed by wide-field IRAM 30 m maps of the Orion B GMC
    (2023) Santa-Maria, M. G.; Goicoechea, J. R.; Pety, J.; Gerin, M.; Orkisz, J. H.; Le Petit, F.; Einig, L.; Palud, P.; Magalhaes, V. de Souza; Beslic, I.; Segal, L.; Bardeau, S.; Bron, E.; Chainais, P.; Chanussot, J.; Gratier, P.; Guzman, V. V.; Hughes, A.; Languignon, D.; Levrier, F.; Lis, D. C.; Liszt, H. S.; Le Bourlot, J.; Oya, Y.; Oberg, K.; Peretto, N.; Roueff, E.; Roueff, A.; Sievers, A.; Thouvenin, P. -A.; Yamamoto, S.
    Context. Massive stars form within dense clumps inside giant molecular clouds (GMCs). Finding appropriate chemical tracers of the dense gas (n(H-2) > several 10(4) cm(-)3 or A(V) > 8 mag) and linking their line luminosity with the star formation rate is of critical importance.
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    Quantitative inference of the H2column densities from 3 mm molecular emission : Case study towards Orion B
    (2021) Gratier, P.; Pety, J.; Bron, E.; Roueff, A.; Orkisz, J. H.; Gerin, M.; De Souza Magalhaes, V.; Gaudel, M.; Vono, M.; Guzmán Veloso, Viviana Gabriela; Bardeau, S.; Chanussot, J.; Chainais, P.; Goicoechea, J. R.; Hughes, A.; Kainulainen, J.; Languignon, D.; Le Bourlot, J.; Le Petit, F.; Levrier, F.; Liszt, H.; Peretto, N.; Roueff, E.; Sievers, A.
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    The extremely sharp transition between molecular and ionized gas in the Horsehead nebula
    (2023) Hernandez-Vera, C.; Guzman, V. V.; Goicoechea, J. R.; Maillard, V.; Pety, J.; Le Petit, F.; Gerin, M.; Bron, E.; Roueff, E.; Abergel, A.; Schirmer, T.; Carpenter, J.; Gratier, P.; Gordon, K.; Misselt, K.
    Massive stars can determine the evolution of molecular clouds by eroding and photo-evaporating their surfaces with strong ultraviolet (UV) radiation fields. Moreover, UV radiation is relevant in setting the thermal gas pressure in star-forming clouds, whose influence can extend across various spatial scales, from the rims of molecular clouds to entire star-forming galaxies. Probing the fundamental structure of nearby molecular clouds is therefore crucial to understand how massive stars shape their surrounding medium and how fast molecular clouds are destroyed, specifically at their UV-illuminated edges, where models predict an intermediate zone of neutral atomic gas between the molecular cloud and the surrounding ionized gas whose size is directly related to the exposed physical conditions. We present the highest angular resolution (similar to 0 ''.5, corresponding to 207 au) and velocity-resolved images of the molecular gas emission in the Horsehead nebula, using CO J = 3-2 and HCO+ J = 4-3 observations with the Atacama Large Millimeter/submillimeter Array (ALMA). We find that CO and HCO+ are present at the edge of the cloud, very close to the ionization (H+/H) and dissociation fronts (H/H-2), suggesting a very thin layer of neutral atomic gas (<650 au) and a small amount of CO-dark gas (AV = 0.006-0.26 mag) for stellar UV illumination conditions typical of molecular clouds in the Milky Way. The new ALMA observations reveal a web of molecular gas filaments with an estimated thermal gas pressure of P-th = (2.3 - 4.0) x 10(6) K cm(-3), and the presence of a steep density gradient at the cloud edge that can be well explained by stationary isobaric photo-dissociation region (PDR) models with pressures consistent with our estimations. However, in the HII region and PDR interface, we find P-th,P-PDR > P-th,P-HII, suggesting the gas is slightly compressed. Therefore, dynamical effects cannot be completely ruled out and even higher angular observations will be needed to unveil their role.
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    Tracers of the ionization fraction in dense and translucent gas : I. Automated exploitation of massive astrochemical model grids
    (2021) Bron, E.; Roueff, E.; Gerin M.; Pety J.; Gratier, P.; Le Petit, F.; Guzman Veloso, Viviana Gabriela; Orkisz, J. H.; De Souza Magalhaes, V.; Gaudel, M.; Vono, M.; Bardeau, S.; Chainais, P.; Goicoechea, J. R.; Hughes, A.; Kainulainen, J.; Languignon, D.; Le Bourlot, J.; Levrier, F.; Liszt, H.; Öberg, K.; Peretto, N.; Roueff, A.; Sievers, A.