Edinburgh Research Explorer

Revised rate coefficients for H-2 and H- destruction by realistic stellar spectra

Research output: Contribution to journalArticle

Related Edinburgh Organisations

Open Access permissions

Open

Original languageEnglish
Pages (from-to)160-168
Number of pages9
JournalMonthly Notices of the Royal Astronomical Society
Volume446
Issue number1
DOIs
StatePublished - Jan 2015

Abstract

Understanding the processes that can destroy H-2 and H- species is quintessential in governing the formation of the first stars, black holes and galaxies. In this study, we compute the reaction rate coefficients for H-2 photodissociation by Lyman-Werner photons (11.2-13.6 eV) and H- photodetachment by 0.76 eV photons emanating from self-consistent stellar populations that we model using publicly available stellar synthesis codes. So far, studies that include chemical networks for the formation of molecular hydrogen take these processes into account by assuming that the source spectra can be approximated by a power-law dependence or a blackbody spectrum at 10(4) or 10(5) K. We show that using spectra generated from realistic stellar population models can alter the reaction rates for photodissociation, k(di), and photodetachment, k(de), significantly. In particular, k(de) can be up to similar to 2-4 orders of magnitude lower in the case of realistic stellar spectra suggesting that previous calculations have overestimated the impact that radiation has on lowering H2 abundances. In contrast to burst modes of star formation, we find that models with continuous star formation predict increasing k(de) and k(di), which makes it necessary to include the star formation history of sources to derive self-consistent reaction rates, and that it is not enough to just calculate J(21) for the background. For models with constant star formation rate, the change in shape of the spectral energy distribution leads to a non-negligible late-time contribution to k(de) and k(di), and we present self-consistently derived cosmological reaction rates based on star formation rates consistent with observations of the high-redshift Universe.

    Research areas

  • astrochemistry, galaxies: high-redshift, cosmology: theory, dark ages, reionization, first stars, SUPERMASSIVE BLACK-HOLES, 1ST COSMOLOGICAL OBJECTS, POPULATION III STARS, DARK-MATTER HALOES, DIRECT COLLAPSE, EARLY UNIVERSE, VIRIAL TEMPERATURES, PRIMORDIAL GAS, RADIATIVE FEEDBACK, 10(4) K

ID: 21282310