HD and H-2 formation in low-metallicity dusty gas clouds at high redshift

摘要: Context. HD and H-2 molecules play important roles in the cooling of primordial very metal-poor gas at high redshift. Aims. Grain surface phase formation are investigated to assess importance trace amounts dust, 10(-5)-10(-3) Z(circle dot), production H-2. Methods. We consider carbonaceous silicate grains include both physisorption chemisorption, tunneling, realistic grain barriers. find that, for a collapsing cloud environment with coupled chemical thermal balance, dust abundances as small 10(-5) solar lead strong boost rate due reactions. As result this enhancement H-2, is formed more efficiently through D+ + reaction. Direct on cannot compete well process temperatures below 150 K. also derive up-to-date analytic fitting formulae an HD, including different binding energies H D. Results. reactions crucial availability environments. Above metallicities solar, route dominates which turn drives phase. At above K, laboratory experiments theoretical modeling suggest that suppressed while not.