Abundance of HOCO⁺ and CO₂ in the outer layers of the L1544 prestellar core

C. Vastel (1) , C. Ceccarelli (2) , B. Lefloch (2) , R. Bachiller

1 IRAP - Institut de recherche en astrophysique et planétologie
2 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble

The L1544 prestellar core has been observed as part of the ASAI IRAM Large Program at 3 mm. These observations led to the detection of many complex molecules. In this Letter, we report the detection of two lines, at 85.5 GHz (4_0,4-3_0,3) and 106.9 GHz (5_0,5-4_0,4), respectively, of the protonated carbon dioxide ion, HOCO⁺. We also report the tentative detection of the line at 100.4 GHz (5_0,5-4_0,4) of DOCO⁺. The non-LTE analysis of the detected lines shows that the HOCO⁺ emission originates in the external layer where non-thermal desorption of other species has previously been observed. Its abundance is (5 ± 2) × 10^-11. Modelling of the chemistry involved in the formation and destruction of HOCO⁺ provides a gaseous CO₂ abundance of 2 × 10^-7 (with respect to H₂) with an upper limit of 2 × 10^-6.

Keywords: astrochemistry; line: identification; molecular data; radiative transfer

Domains: Sciences of the Universe [physics]; Astrophysics [astro-ph]

C. Vastel, C. Ceccarelli, B. Lefloch, R. Bachiller. Abundance of HOCO⁺ and CO₂ in the outer layers of the L1544 prestellar core. Astronomy and Astrophysics - A&A, 2016, 591, ⟨10.1051/0004-6361/201628427⟩. ⟨insu-03670227⟩