Speaker
Description
Analysing the stellar kinematic properties of a dwarf galaxy makes it possible to investigate which internal mechanisms have shaped its evolution. Isolated dwarf galaxies with an extended star formation history, in particular, offer the opportunity to study not only star formation processes at low-mass and low-metallicity scales, but also to understand how internal kinematic properties evolve thanks to the possibility of a combined comparison of gas kinematics with that of young and old stars.
In this context, we have analysed a new spectroscopic dataset of the isolated gas-rich dwarf galaxy IC 1613 taken with the integral-field-unit MUSE instrument mounted on the Very Large Telescope (VLT), capable of combining high spatial resolution to a wide spectral coverage (4750 − 9300 AA) with a resolving power of R = 1500 − 3000. Thanks to this revolutionary instrument, we obtained a large dataset of ~2000 sources extracted from 3 pointings, of which we could reliably perform spectral classification and radial velocity determination for more than 800 stars. We were also able to obtain metallicities from Ca II triplet lines for a selected subsample of ~300 red giant branch stars. This dataset is the largest currently collected for an isolated dwarf galaxy in the Local Group.
From the spectral classification we found giant stars of all stellar types, with a large predominance of red giant branch stars, as to be expected. We were also able to identify a sample of C-star candidates, useful for determining the spectroscopic C/M ratio, and hot emission line stars as an additional kinematic tracer for young stars.
The preliminary kinematic analysis has led to a systemic velocity and a velocity dispersion both in agreement with previous literature values. We also found with high statistical significance a linear rotation signal along the optical major axis of the galaxy, which is a novelty. Stars follow the velocity field of the neutral HI component, although they start to decouple from the gas motion around the half-light radius. When subdivided according to age, young and old stars seem to follow similar kinematic trends, although the statistics for young stars drop dramatically in the outermost pointings.
Finally, chemical analysis resulted in an average [Fe/H] that was slightly higher than literature values, but within the rms dispersion of the stellar luminosity-metallicity relation. We found no evidence of a radial metallicity gradient, compatible with results from other similarly luminous dwarf galaxies.
Regardless of results actually obtained, we want to show the vast research possibilities that MUSE offers in the field of resolved stellar populations in nearby dwarf galaxies, whose surface we have only scratched.
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