Mathematics – Logic
Scientific paper
Jan 2012
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012aas...21922201b&link_type=abstract
American Astronomical Society, AAS Meeting #219, #222.01
Mathematics
Logic
Scientific paper
The Lambda CDM paradigm predicts that the outer parts of galaxies should, in large part, consist of material tidally stripped off of smaller dwarf galaxies as they are incorporated into the potential of the larger galaxy. We present results from the exploration of the structure and stellar populations of the Milky Way stellar halo. To date, we have focused on understanding the structure of the stellar halo as probed by two key tracer stellar populations - main sequence turn-off stars (MSTO; a well-populated diagnostic of a wide range of stellar populations), and blue horizontal branch stars (BHB; a sparsely-sampled standard candle indicative of ancient metal-poor populations, but available to larger distances). We find that the stellar halo is richly substructured as traced by MSTO and BHB stars, in both 3D space and in velocity space. Furthermore, we find that the degree and type of substructure showed by both populations are different - the ratio of BHB to MSTO stars changes from place to place in the halo, with coherent values of BHB/MSTO star number in given clearly-recognizable structured (e.g., the Sagittarius stream, low-latitude stream, etc.) Where possible, we compare quantitatively with models of galaxy formation in a cosmological context. The quantitative predictions of such models do depend on the assumptions underlying the model, and we demonstrate in particular the importance of a disk potential in driving the character and structure of stellar halos in a cosmological context. We find a close quantitative correspondence between predictions of spatial and velocity substructure from the cosmologically-motivated models and the observations for both MSTO and BHB stars, giving weight to the notion that stellar halos, at least to first order, present an unparalleled opportunity to study the formation of individual galaxies in a cosmological context.
Bailin Jeremy
Bell Eric F.
Martin Nicolas F.
Pan-STARRS 1 Consortium
Ruhland Christine
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