Late gas accretion on to primordial minihaloes: a model for Leo T, dark galaxies and extragalactic high-velocity clouds
Abstract
In this Letter, we revisit the idea of reionization feedback on dwarf galaxy formation. We show that primordial minihaloes with vcir < 20 km s-1 stop accreting gas after reionization, as it is usually assumed, but in virtue of their increasing concentration and the decreasing temperature of the intergalactic medium as redshift decreases below z = 3, they have a late phase of gas accretion and possibly star formation. We expect that pre-reionization fossils that evolved on the outskirts of the Milky Way or in isolation show a bimodal star formation history with 12- and <10-Gyr old population of stars. Leo T fits with this scenario. Another prediction of the model is the possible existence of a population of gas-rich minihaloes that never formed stars. More work is needed to understand whether a subset of compact high-velocity clouds can be identified as such objects or whether an undiscovered population of dark galaxies exists in the voids between galaxies.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- January 2009
- DOI:
- 10.1111/j.1745-3933.2008.00586.x
- arXiv:
- arXiv:0806.2402
- Bibcode:
- 2009MNRAS.392L..45R
- Keywords:
-
- galaxies: formation;
- cosmology: theory;
- Astrophysics
- E-Print:
- 5 pages, 4 figures, accepted version MNRAS 392, L45