The Astrochemical Impact of Cosmic Rays in Protoclusters. II. CI-to-H2 and CO-to-H2 Conversion Factors

We utilize a modified astrochemistry code that includes cosmic-ray (CR) attenuation in situ to quantify the impact of different CR models on the CO-to-H-2 and CI-to-H-2 conversion factors, Xco and XcI, respectively. We consider the impact of CRs accelerated by accretion shocks, and show that clouds with star formation efficiencies greater than 2% have X-CO = (2.5 1) x 10(20) cm(-2)(K km s(-1)) 1, consistent with Milky Way observations. We find that changing the CR ionization rate from external sources from the canonical zeta approximate to 10(-17) to zeta approximate to 10(-16) s(-1), which better represents observations in diffuse gas, reduces X-CO by 0.2 dex for clusters with surface densities below 3 g cm z. We show that embedded sources regulate X-CO and decrease its variance across a wide range of surface densities and star formation efficiencies. Our models reproduce the trends of a decreased X-CO in extreme CR environments. X-CI has been proposed as an alternative to Xco due to its brightness at high redshifts. The inclusion of internal CR sources leads to 1.2 dex dispersion in XcI ranging from 2 x 102 1 1 < XcI < 4 x 1021 cm (K km s). We show that X-CI is highly sensitive to the underlying CR model.