Astronomers measure detailed chemical abundances of 158 stars in a nearby dwarf galaxy
https://phys.org/news/2017-07-astronomers-chemical-abundances-stars-nearby.html
An international team of astronomers has performed detailed measurements of the chemical composition of 158 red giant stars in the nearby Sagittarius dwarf
galaxy. The study, presented in a paper published July 11 on arXiv.org, is so far the largest and most chemically extensive high-resolution survey of this galaxy.
Discovered in 1994, Sagittarius is a nearby, massive, elliptical loop-shaped satellite galaxy of the Milky Way. The dwarf is currently merging with our galaxy,
resulting in massive tidal tails that can be found in the Galactic halo. Therefore, detailed studies of Sagittarius could clarify the formation of Milky Way's halo.
Due to its proximity (about 88,000 light years away), the stars in the core of this dwarf galaxy are excellent targets for high-resolution spectroscopy observations
using ground-based telescopes.
So a team of researchers led by Sten Hasselquist of the New Mexico State University recently conducted detailed spectroscopic observations of Sagittarius as part of
the Apache Point Observatory Galactic Evolution Experiment, or APOGEE. The main goal of this survey is to study over 100,000 red giant stars across the full range of
the galactic bulge, bar, disk, and halo. APOGEE makes use of a high-resolution near-infrared spectrograph connected to the Sloan Foundation 2.5m Telescope at Apache
Point Observatory in New Mexico in order to penetrate the dust that obscures significant fractions of the disk and bulge of our galaxy.
Hasselquist and colleagues has used APOGEE's spectrograph to estimate chemical composition of a large group of stars in Sagittarius. They managed to measure chemical
abundances for the 16 elements, namely carbon (C), nitrogen (N), oxygen (O), sodium (Na), magnesium (Mg), aluminium (Al), silicon (Si), phosphorus (P), potassium (K),
calcium (Ca), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co) and nickel (Ni).
"The Apache Point Observatory Galactic Evolution Experiment provides the opportunity to measure elemental abundances for C, N, O, Na, Mg, Al, Si, P, K, Ca, V, Cr, Mn,
Fe, Co, and Ni in vast numbers of stars. We analyze the chemical abundance patterns of these elements for 158 red giant stars belonging to the Sagittarius dwarf galaxy
(Sgr)," the researchers wrote in the paper.