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Recent publications

• Chemical evolution in star clusters: the role of mass and environment
  Martell, S.L., Duffau, S., Milone, A.P., Smith, G.H., Briley, M.M. and Grebel, E.K.
  2013, to appear in Proceedings of "Reading the book of globular clusters with the lens of stellar evolution", Rome, Italy (Nov. 26-28, 2012)
  
• Lithium-Rich Field Giants in the Sloan Digital Sky Survey
  Martell, S.L. and Shetrone, M.D.
  2013, accepted for publication in MNRAS
  
• Globular cluster contributions to Galactic halo assembly
  Martell, S.L.
  2013, to appear in Proceedings of IAU XXVIII Special Session 1: "Origin and complexity of massive star clusters", Beijing, China (Aug. 20-24, 2012)
  
• Lithium-rich stars in the Sloan Digital Sky Survey
  Martell, S.L. and Shetrone, M.D.
  2013, to appear in Proceedings of XII Internation Symposium on Nuclei in the Cosmos, Cairns, Australia (Aug. 5-12, 2012)
  
• The Ninth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-III Baryon Oscillation Spectroscopic Survey
  Ahn, C.P. et al. (236 coauthors)
  2012, ApJS 203, 21
  
• Cyanogen in NGC 1851 Red Giant Branch and Asymptotic Giant Branch Stars: Quadrimodal Distributions
  Campbell, S.L., Yong, D., Wylie-de Boer, E.C., Stancliffe, R.J., Lattanzio, J.C., Angelou, G.C., D'Orazi, V., Martell, S.L., Grundahl, F. and Sneden, C.
  2012, ApJL 761, 2
  
• The AAO's Gemini High0Resolution Optical SpecTrograph (GHOST) concept
  Ireland, M.J., Barnes, S., Cochrane, D., Colless, M., Connor, P., Hortony, A., Gibson, S., Lawrence, J., Martell, S.L. et al.
  2012, SPIE 8446, 29
  
• Two views of globular cluster stars in the Galactic halo
  Martell, S.L.
  2011, in EPJ Web of Conferences, 19, 03007: Proceedings of "Assembling the Puzzle of the Milky Way", Le Grand Bornand, France (Apr. 17-22, 2011)
  
• A Survey of CN and CH Variations in Galactic Globular Clusters from SDSS Spectroscopy
  Smolinski, J.P., Martell, S.L., Beers, T.C. and Lee, Y.-S.
  2011, AJ 142, 126
  
• Building the Galactic halo from globular clusters: evidence from chemically unusual red giants
  Martell, S.L., Smolinski, J.P., Beers, T.C. and Grebel, E.K.
  2011, A&A 534, 136
  
• Light-element abundance variations in globular clusters
  Martell, S.L.
  2011, AN 332, 467
  
  

Research themes

My research focuses on connections between globular clusters and the formation history of the Galaxy. Since they are some of the oldest stars in the Galaxy, globular cluster stars carry information about the cosmological conditions of the early phases of the Milky Way's existence.

Specifically, I am interested in using the light-element abundance variations found in every globular cluster in the Milky Way to understand how star formation happened in old globular clusters. Presently favored models of globular cluster formation involve two closely spaced flashes of star formation, with the first generation modifying the chemical composition of the second. If this picture is qualitatively correct, all Galactic globular clusters were massive and dense enough in the past to retain chemically enriched winds from high-mass stars and convert it into new stars, although their current escape velocities can be quite low.

Comparing the abundance patterns in Galactic globular clusters with the patterns in star clusters in nearby dwarf galaxies illuminates the ways in which the large-scale galactic environment affects star formation, and comparing old globular clusters to intermediate-age clusters allows investigation of the ways that cluster formation has changed between the early Universe and the present day. Star clusters that are forming now are quite different from what we think the early phases of globular clusters were like: less massive, generally located in the disks of galaxies, and not able to recycle material into multiple generations. This implies that there has been significant evolution between the early Universe and the present day in the way that star clusters are formed, and also that individual globular clusters have evolved strongly over that same time period.