11:45 AM - 12:00 PM
[PCG19-05] Investigating the impact of X-rays on the molecular abundances of envelopes and disks around low-mass protostars with ngVLA
Keywords:astrochemistry, protostars, protoplanetary disks, snowline, ngVLA, molecules
Water has been used to study dynamical properties of star-forming regions, and it is also one of key molecules in chemical evolutions. Water destruction by X-rays has been proposed to explain the low water gas fractional abundances in the inner warm envelopes and disks around several low-mass protostars (e.g., Stauber et al. 2006), but the detailed chemistry, including the nature of alternative oxygen carriers, is not yet understood.
Recently, we computed the chemical composition of low-mass protostar envelopes using a gas-grain chemical reaction network (e.g., Walsh et al. 2015), with various X-ray luminosities of the central protostars. We aimed to understand the impact of X-rays on the composition of low-mass protostar envelopes, focusing specifically on water and related oxygen bearing species. According to our calculations, X- ray induced chemistry strongly affects the abundances of water and related species such as O, O2. In addition, the fractional abundances of HCO+ and CH3OH, which have been considered to be tracers of the water snowline (e.g., van’t Hoff et al. 2018a,b), significantly increase/decrease within the water snowline, respectively, as the X-ray fluxes become larger.
Moreover, the fractional abundances of some other dominant molecules, such as NH3, are also affected by strong X-ray fields, especially within their own snowlines. Future molecular line observations with ngVLA will be expected to constrain the inner gas abundances of CH3OH, HCO+, and NH3, creating a more complete picture of the oxygen chemistry and opening a window into the independent nitrogen chemistry.
Recently, we computed the chemical composition of low-mass protostar envelopes using a gas-grain chemical reaction network (e.g., Walsh et al. 2015), with various X-ray luminosities of the central protostars. We aimed to understand the impact of X-rays on the composition of low-mass protostar envelopes, focusing specifically on water and related oxygen bearing species. According to our calculations, X- ray induced chemistry strongly affects the abundances of water and related species such as O, O2. In addition, the fractional abundances of HCO+ and CH3OH, which have been considered to be tracers of the water snowline (e.g., van’t Hoff et al. 2018a,b), significantly increase/decrease within the water snowline, respectively, as the X-ray fluxes become larger.
Moreover, the fractional abundances of some other dominant molecules, such as NH3, are also affected by strong X-ray fields, especially within their own snowlines. Future molecular line observations with ngVLA will be expected to constrain the inner gas abundances of CH3OH, HCO+, and NH3, creating a more complete picture of the oxygen chemistry and opening a window into the independent nitrogen chemistry.