DWARFGALAXIES

Exploring evolutionary links between dwarf galaxy types using distant Local Group late-type dwarfs

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 Obiettivo del progetto (Objective)

'Dwarf galaxies play a key role in our understanding of galaxy formation and evolution as they are the most numerous kind of galaxies in the Universe and they are also potentially powerful dark matter probes. Our understanding of this galaxy population and of the processes that drive its evolution is limited, mainly because a detailed observational picture of the properties of the various types of dwarf galaxies is lacking. We do not know whether the various types of dwarf galaxies originated from different formation processes, or whether they shared similar progenitors, and environmental effects and/or internal processes caused the observed differences in their properties.

In the Local Group we can study in great detail the two main types of dwarf galaxies, those that contain gas (dwarf irregulars, dIs, still forming stars, and transition types, dTs, with no current star formation) and those devoid of gas (dwarf spheroidals, dSphs).

This project aims to provide a leap forward in our knowledge of distant dIs and dTs and their relation to the well-studied nearby dSphs. For the first time the wide-area spatial distribution of stellar populations, metallicity and kinematic properties will be derived for stars covering a wide age range in a sample of isolated dIs and dTs. This will be done to a similar degree of detail and using the same tracers as for dSphs. Furthermore, by studying isolated dwarf galaxies, environmental and internal effects as main evolutionary drivers will be disentangled.

With the expertise of Prof.Dr.M.Tosi and her group, the applicant will be trained in complementary observational and theoretical approaches; in extracting and modeling star formation and chemical enrichment histories, dark matter mass content and distribution; and exploring the relation between the kinematic properties of the gas and the stars.

The proposed project and training will greatly benefit the development of the applicant's future career.'

Introduzione (Teaser)

As kids, many of us pondered what stars are made of. EU-funded astronomers wondered how the galaxies formed and evolved to the hundreds of billions stars we see.

Descrizione progetto (Article)

When astronomers observe galaxies that are billions of light years away from Earth, they see back in time at how star systems appeared billions of years ago. These observations from galaxies' past have resulted in a remarkable insight into how galaxies grow as big as they are. The first galaxies to form are dwarf galaxies and these subsequently merge to form larger star systems, according to the widely accepted 'cold dark matter' theory.

The smallest galaxies around our Milky Way are the nearby dwarf spheroidals, which may be leftovers of our galaxy formation. Further out are slightly misshaped dwarf irregular galaxies, which may be newcomers to our galactic neighbourhood. Astronomers working on the DWARFGALAXIES project wondered if the nearby dwarf spheroidal galaxies have all the same star-forming 'stuff' that we find in more distant dwarf galaxies.

Astronomers working on the DWARFGALAXIES project wondered why the nearby dwarf spheroidal galaxies do not have all the same star-forming 'stuff' that we find in more distant dwarf galaxies. Are dwarf spheroidal and dwarf irregular galaxies different objects? Or can they be considered as descending from similar progenitors which some mechanism made evolve differently? To find answers to these questions, the DWARFGALAXIES astronomers brought to bear the combined power of giant telescopes around the world on understanding the so-called dwarf galaxies.

Dwarf transition galaxies have intermediate properties to dwarf spheroidal and dwarf irregular galaxies, and so are thought to be caught in the act of transforming from one type to the other. Furthermore, they were found beyond the point that dwarf spheroidal galaxies become rare while the dwarf irregular counterparts flourish. This is the point that is thought to coincide with the edge of the Milky Way's dark matter distribution.

The researchers found hints of similarities in the way stars of different ages are distributed within dwarf galaxies, independently on the type of dwarf galaxy. Also the general motions of stars in dwarf spheroidals appear more alike to those of dwarf irregulars if one looks at the stars in these latter systems rather than in the gas. Their observations open up further questions that need follow-up, providing targets for future telescope facilities such as the MOONS spectrograph on the Very Large Telescope.

In the meantime, the new data acquired by the researchers will strengthen our understanding of similarities and differences in the properties of the various dwarf galaxy types. The Gaia space mission will provide invaluable information on what may have been the role of interaction with the Milky Way in shaping the nearby dwarf spheroidals.