PI Total time #2 (at least) Rodolfo Smiljanic 8.6n (ELT 42m) An observational spectroscopist with experience in spectrum synthesis. An specialist in chemical evolution of galaxies. Spectroscopy of luminous red giants in the Tucana dwarf galaxy This proposal intends to acquire medium resolution spectra of giant stars in the isolated Tucana dwarf spheroidal galaxy. Elemental abundances will be derived using spectrum synthesis. The abundances should help to understand the chemical evolution of this system, a possible remnant of the building blocks of galaxies.

Scientific Rationale Tucana is a dwarf spheroidal (DwSph) galaxy in the outskirts of the local group. Contrary to the majority of the local group dwarf galaxies it is not gravitationally bound to the Galaxy or M31. It offers an almost unique chance to study the evolution, the star formation history and the chemical enrichment of a dwarf galaxy subject to an environment different from the ones in the halo of giant spirals. This study would help to constrain models of the evolution of this kind of objects. In the hierarchical framework, dwarf galaxies are thought to be the building blocks of larger barionic structures. Thus, this should be a chance to study a possible galaxy building block. This DwSph galaxy may represent the evolution of the primordial dwarf galaxies.

Objectives We intend to obtain spectra of red giants near the tip of the red giant branch (I~21). Abundances for some elements would be derived using spectrum synthesis. The abundances would be used to discuss its chemical evolution in comparison to what is known for dwarf galaxies near giant spirals. This comparison might give clues on the influence of the environment in the evolution of these objects. The results might give important clues on the composition of the primordial dwarf galaxies, thought to be the building blocks of larger structures.

ELT Justification: According to the exposure time calculator, the same proposal in an 8m class telescope would require more than 250 nights. Legacy Value: S pectra of stars with different chemical composition than the ones in the Galaxy should be useful for stellar population synthesis. Data Reduction: Data reduction presents no special challenge. Standard procedure for reducing the spectra and some care during the spectral synthesis due to the resolution.

RunTargetR.A.Dec.ToTMagNotes ABCField 143h -64˚ 43h I ~21 S/N ~ 50 DEFField 243h-64˚ 43h I~21S/N ~ 50 RunMPModeAOT.FOVPixel c Notes ABCABC 20 R=10000 GLAO 20h 3h 1’50 510nm 580nm 850nm Mg, Fe, Ni Fe, Cr, Ba, Na Ca triplet DEFDEF 15 R=10000 GLAO 20h 3h 1’50 510nm 580nm 850nm Mg, Fe, Ni Fe, Cr, Ba, Na Ca triplet