Chemical Tagging

Chemical Homogeneity in the Hyades

We present an abundance analysis of the heavy elements Zr, Ba, La, Ce, and Nd for Hyades F-K dwarfs based on high-resolution, high signal-to-noise ratio spectra from Keck HIRES. The derived abundances show the stellar members to be highly uniform, although some elements show a small residual trend with temperature. The rms scatter for each element for the cluster members is as follows: Zr=0.055, Ba=0.049, Ce=0.025, La=0.025, and Nd=0.032 dex. This is consistent with the measurement errors and implies that there is little or no intrinsic scatter among the Hyades members.

Galaxy Genesis - Unravelling the Epoch of Dissipation in the Early Disk

How did the Galactic disk form and can the sequence of events ever be unravelled from the vast stellar inventory? This will require that some of the residual inhomogeneities from prehistory escaped the dissipative process at an early stage. Fossil hunting to date has concentrated mostly on the stellar halo, but a key source of information will be the thick disk. This is believed to be a `snap frozen' relic which formed during or shortly after the last major epoch of dissipation, or it may have formed from infalling systems early in the life of the Galaxy.

The New Galaxy: Signatures of Its Formation

The formation and evolution of galaxies is one of the great outstanding problems of astrophysics. Within the broad context of hierachical structure formation, we have only a crude picture of how galaxies like our own came into existence. A detailed physical picture where individual stellar populations can be associated with (tagged to) elements of the protocloud is far beyond our current understanding. Important clues have begun to emerge from both the Galaxy (near-field cosmology) and the high redshift universe (far-field cosmology).

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