John E. Norris

Learn More
We find that the globular cluster systems of the Milky Way and of our neighboring spiral galaxy, M31, comprise two distinct entities, differing in three respects. First, M31 has a set of young globular clusters (GCs), ranging in age from a few 100 Myr to 5 Gyr old, as well as old globular clusters. No such very young GCs are known in the Milky Way. Second,(More)
The halo of the Milky Way provides unique elemental abundance and kinematic information on the first objects to form in the Universe, and this information can be used to tightly constrain models of galaxy formation and evolution. Although the halo was once considered a single component, evidence for its dichotomy has slowly emerged in recent years from(More)
We present a sample of 1777 bright (9 < B < 14) metal-poor candidates selected from the Hamburg/ESO Survey (HES). Despite saturation effects present in the red portion of the HES objectiveprism spectra, the data were recoverable and quantitative selection criteria could be applied to select the sample. Analyses of medium-resolution (∼ 2 Å) follow-up(More)
Abundances of C, N, and O are determined in four bright red giants that span the known abundance range for light (Na and Al) and s-process (Zr and La) elements in the globular cluster NGC 1851. The abundance sum C+N+O exhibits a range of 0.6 dex, a factor of 4, in contrast to other clusters in which no significant C+N+O spread is found. Such an abundance(More)
We report the detection of the Pb i l4057.8 line in the very metal-poor ( ), carbon-rich star, [Fe/H] = 22.7 LP 625-44. We determine the abundance of Pb ( ) and 15 other neutron-capture elements. The [Pb/Fe] = 2.65 abundance pattern between Ba and Pb agrees well with a scaled solar system s-process component, while the lighter elements (Sr–Zr) are less(More)
We determine the metallicity distribution function (MDF) of the Galactic halo by means of a sample of 1638 metal-poor stars selected from the Hamburg/ESO objective-prism survey (HES). The sample was corrected for minor biases introduced by the strategy for spectroscopic follow-up observations of the metal-poor candidates, namely “best and brightest stars(More)
We report the discovery and high-resolution, high S/N , spectroscopic analysis of the ultra-metal-poor red giant HE 0557−4840, which is the third most heavy-element deficient star currently known. Its atmospheric parameters are Teff = 4900K, log g = 2.2, and [Fe/H] = –4.75. This brings the number of stars with [Fe/H] < –4.0 to three, and the discovery of HE(More)
We report on an analysis of the chemical composition of five carbon-rich, very metalpoor stars based on high-resolution spectra. One star, CS 22948-027, exhibits very large overabundances of carbon, nitrogen, and the neutron-capture elements, as found in the previous study of Hill et al.. This result may be interpreted as a consequence of mass transfer from(More)
We present a detailed chemical abundance analysis of HE 1300+0157, a subgiant with [Fe/H] = −3.9. From a high-resolution, high-S/N Subaru/HDS spectrum we find the star to be enriched in C ([C/Fe]1D ∼ +1.4) and O ([O/Fe]1D ∼ +1.8). With the exception of these species, HE 1300+0157 exhibits an elemental abundance pattern similar to that found in many other(More)