HUDAGA - The search for the smallest galaxies

Team: Tom Oosterloo, Betsey Adams, Antonino Marasco

 Understanding the formation and evolution of the smallest galaxies is a challenging task. The dark matter potentials in which small galaxies live are shallow, making them delicate and fragile systems. Even small changes in the balance between the various processes occurring during their evolution, in particular during the epoch the very first stars formed, may result in entirely different objects: from galaxies containing only stars and no gas, to systems containing mainly gas and only a few stars. Although the gap between predictions and observations of the population of dwarf galaxies has narrowed recently, several key problems remain. One is to understand what happens for the very smallest galaxies, i.e. at the limit to galaxy mass below which no stars form anymore and whether the dark, starless objects below this limit are nevertheless observable through other tracers, such as cold gas. There are indeed indications, from both theory and observations, that a large population of yet undiscovered gas-dominated, (almost) dark dwarf galaxies could exist and this project will make an important step forward in assessing this population. This project will provide important input to understanding galaxy formation, in particular for the period in the early Universe when the very first stars and galaxies formed.


Optical image of Leo T (colour image) with overlaid the contours of the distribution of the atomic hydrogen (contour levels 5, 10, 20 and 50 x 1019 cm-2). The stellar body of Leo T is very dim and consists of the barely visible, small concentration of bluish stars in this image. On the other hand, the atomic hydrogen is bright and easily detectable with radio telescopes.
Leo T is one of the smallest galaxies known. The main questions this project tries to address are whether there are even smaller, fainter galaxies, and if they exist what they look like, and what they may tell us about galaxy formation and the early Universe.

Design: Kuenst.    Development: Dripl.    © 2021 ASTRON