Stellar Archaeology as a Time Machine to the First Stars

Detailed Elemental Abundances in the M31 Stellar Halo: Low-Resolution Resolved Stellar Spectroscopy

7 Dec 2018, 14:40

10m

Lecture Hall (Kavli IPMU)

Dwarf galaxies & Galactic chemical evolution Dwarf Galaxies

Speaker

Ivanna Escala (Caltech)

Description

The stellar halo and tidal streams of M31 provide an essential counterpoint to the same structures around the Galaxy. While Galactic measurements of [Fe/H] and [$\alpha$/Fe] have been made, little is known about the detailed chemical abundances of the M31 system. To make progress with existing telescopes, we apply spectral synthesis to low-resolution spectroscopy (R $\sim$ 2500 at 7000 Angstroms) across a wide spectral range (4500 $<$ $\lambda$ $<$ 9100 Angstroms). We have obtained deep spectra of red giant branch stars (RGB) in the tidal streams and smooth halo of M31 using the DEIMOS 600ZD grating, resulting in higher signal-to-noise per spectral resolution element (S/N $\sim$ 30 Angstrom${}^{-1}$). By applying our technique to RGB stars in Galactic globular clusters with existing measurements from higher-resolution spectroscopy, we demonstrate that our technique reproduces previous measurements derived from higher resolution spectra over a more limited spectral range (6300 - 9100 Angstroms) using the DEIMOS 1200G grating. For the first time, we present measurements of [Fe/H] and [$\alpha$/Fe] of sufficient quality and sample size to construct quantitative models of galactic chemical evolution in the M31 system. We also discuss this work in the context of future Subaru/PFS spectra in M31's stellar halo.

Affiliation

California Institute of Technology

Presentation materials

escala.pdf