The chemistry of Young Stellar Objects at low metallicity
Our program probes the chemistry of young stellar object (YSO) envelopes in the low metallicity environments of the LMC and SMC. Oliveira et al. (2009, 2011) find that CO2 and CO ices are more abundant with respect to H2O ice in the LMC than in the Galaxy. Since both ice species are enhanced consistently, it is unlikely this results from increased CO2 production as previously suggested. Instead it may result from a reduced H2O column density in the LMC YSO envelopes, a consequence of stronger UV radiation and reduced dust-to-gas ratio at lower metallicity.
Oliveira et al. (2011) also show that while H2O and CO2 ice are detected, CO ice is not detected in the SMC YSOs; we also observe a reduction in CO2 column density. This suggests that low gas-phase CO density and higher dust temperature in the SMC inhibit CO freeze-out and CO2 survival.
With an ongoing Herschel spectroscopy program we will study the gas-phase abundance of H2O, CO, OH, atomic O and C, to constrain the cooling budget at low metallicity.