URSO, Riccardo GiovanniRiccardo GiovanniURSOPALUMBO, Maria ElisabettaMaria ElisabettaPALUMBOCeccarelli, C.C.CeccarelliBalucani, N.N.BalucaniBottinelli, S.S.BottinelliCODELLA, CLAUDIOCLAUDIOCODELLAFONTANI, FRANCESCOFRANCESCOFONTANILETO, PAOLOPAOLOLETOTRIGILIO, CORRADOCORRADOTRIGILIOVastel, C.C.VastelBachiller, R.R.BachillerBaratta, G.G.BarattaBUEMI, CARLA SIMONACARLA SIMONABUEMICaux, E.E.CauxJaber Al-Edhari, A.A.Jaber Al-EdhariLefloch, B.B.LeflochLópez-Sepulcre, A.A.López-SepulcreUMANA, Grazia Maria GloriaGrazia Maria GloriaUMANATesti, L.L.Testi2021-01-192021-01-1920190004-6361http://hdl.handle.net/20.500.12386/29856Context. C<SUB>2</SUB>O and C<SUB>3</SUB>O belong to the carbon chain oxides family. Both molecules have been detected in the gas phase towards several star-forming regions, and to explain the observed abundances, ion-molecule gas-phase reactions have been invoked. On the other hand, laboratory experiments have shown that carbon chain oxides are formed after energetic processing of CO-rich solid mixtures. Therefore, it has been proposed that they are formed in the solid phase in dense molecular clouds after cosmic ion irradiation of CO-rich icy grain mantles and released in the gas phase after their desorption. <BR /> Aims: In this work, we contribute to the understanding of the role of both gas-phase reactions and energetic processing in the formation of simple carbon chain oxides that have been searched for in various low-mass star-forming regions. <BR /> Methods: We present observations obtained with the Noto-32m and IRAM-30 m telescopes towards star-forming regions. We compare these with the results of a gas-phase model that simulates C<SUB>2</SUB>O and C<SUB>3</SUB>O formation and destruction, and laboratory experiments in which both molecules are produced after energetic processing (with 200 keV protons) of icy grain mantle analogues. <BR /> Results: New detections of both molecules towards L1544, L1498, and Elias 18 are reported. The adopted gas phase model is not able to reproduce the observed C<SUB>2</SUB>O/C<SUB>3</SUB>O ratios, while laboratory experiments show that the ion bombardment of CO-rich mixtures produces C<SUB>2</SUB>O/C<SUB>3</SUB>O ratios that agree with the observed values. <BR /> Conclusions: Based on the results obtained here, we conclude that the synthesis of both species is due to the energetic processing of CO-rich icy grain mantles. Their subsequent desorption because of non-thermal processes allows the detection in the gas-phase of young star-forming regions. In more evolved objects, the non-detection of both C<SUB>2</SUB>O and C<SUB>3</SUB>O is due to their fast destruction in the warm gas. <P />Data in Fig. 1 are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/628/A72">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/628/A72STAMPAenArticle10.1051/0004-6361/2018343222-s2.0-85090163720000480314200005https://www.aanda.org/articles/aa/full_html/2019/08/aa34322-18/aa34322-18.html2019A&A...628A..72UFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation