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Staff Record
Photo of Sarah Martell
Scientia Fellow and Senior Lecturer

Sarah Martell

[p]: 

+61 2 9385 6547

[f]: 

+61 2 9385 6060

Role(s): 

co-Project Scientist for the GALAH (Galactic Archaeology with HERMES) survey
Steering Committee, Astronomical Society of Australia chapter for Early-Career Researchers, 2013-
UNSW Canberra A-B promotions committee, 2017-2019
School coordinator for undergraduate experience, 2016-
School equity committee and research committee, 2014-

Education: 

  • 2008: PhD Astronomy & Astrophysics, University of California Santa Cruz, USA
  • 2001: BS Astronomy, University of Washington, USA
  • 2001: BS Physics, University of Washington, USA

Research Interests: 

My research

My main research focus is on "Galactic archaeology" - unwinding the present-day orbits and chemical compositions of stars in the Milky Way to study the processes at work early in Galactic history. I am one of two Project Scientists for the GALAH (Galactic Archaeology with HERMES) survey, which began collecting data in late 2013. Over the course of our observing program, we will use the HERMES spectrograph, together with the 2dF 400-fiber positioner, to take high-resolution spectra of 1 million stars in the Milky Way's disk and halo from the Anglo-Australian Telescope. We will determine abundances of up to 29 important chemical elements for each star, and plan to use this unprecedented data set to identify stars that originally formed together. Combining this with the precise positions and distances the ESA Gaia spacecraft will measure for all of our stars, we will study the history of star formation, chemical evolution, migration and minor mergers in the Galaxy.

In other work, I use moderate-resolution spectroscopy from Keck Observatory, Lick Observatory and the Very Large Telescope to study the compositions of stars in globular clusters, some of the oldest stars in the Milky Way, and to compare them to star clusters in nearby dwarf galaxies. Since globular cluster stars formed at the very beginning of our galaxy's lifetime, we can use their properties to reconstruct the early history of the Milky Way. Roughly half of the stars in globular clusters have an unusual abundance pattern in the "light" elements (carbon, nitrogen, oxygen, sodium, magnesium and aluminum), indicating that star formation in clusters in the early Galaxy happened quickly and involved recycling material between subsequent generations of stars.

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.

Student projects

  • GALAH data exploration: Build tools to help classify and search the large and growing dataset from the GALAH (Galactic Archaeology with HERMES) survey. Any level of programming experience welcome.
  • Rare stars in the Galaxy: Search for stars that have migrated from star clusters into the Galactic halo, or have captured material from a binary companion, using spectroscopy from the AAOmega Evolution of Galactic Structure survey.
  • Star clusters and stellar abundances: A star's chemical abundance pattern is a record of where and when it formed. Investigate the differences between stars in clusters that are young and old, in the Milky Way and in nearby dwarf galaxies, to explore the effect of environment and time on star clusters.

You can find more information about these and other available research projects in the School of Physics on the Research Projects page.

Honours, Awards and Memberships: 

Awards

  • 2019-2022 UNSW Scientia Fellow
  • 2014-2016 DECRA (Discovery Early Career Researcher Award) Fellowship (Australia)
  • 2010 MPIA-ZAH Ernst Patzer Prize for excellent publication by an early-career researcher in Heidelberg (Germany)

 

Recent invited talks

  • "The Survival of Dense Star Clusters in the Milky Way System", 2018, Heidelberg, Germany
  • "The Formation of Globular Clusters at High and Low Redshift", 2018, Sexten, Italy
  • "Multiple Populations in Stellar Clusters", 2018, Sexten, Italy 
  • "The Metal-Poor Galaxy", 2018, Ringberg, Germany
  • "Globular Cluster Systems and their host Galaxies", 2017, Sexten, Italy
  • "Multiple Populations in Globular Clusters: Where do we stand?", 2016, Sexten, Italy
  • "Multiwavelength Dissection of Galaxies", 2015, Southern Cross Conference Series VIII, Sydney, Australia
  • "Young Stars & Planets Near the Sun", 2015, IAU Symposium 314, Atlanta, Georgia, USA
  • "Multi-Object Spectroscopy in the Next Decade", 2015, La Palma, Spain

Memberships

  • 2014-2015, Australian member of the Gemini Observatory Science and Technology Advisory Committee
  • 2014-2015, member ex officio of the Optical Telescopes Advisory Committee
  • 2011-present, Member of the Astronomical Society of Australia
  • 2009-2016, International Affiliate of the American Astronomical Society

Selected Publications: 

Recent publications on survey science

  1. "The GALAH survey: observational overview and Gaia DR1 companion", Monthly Notices of the Royal Astronomical Society 2017, Martell, S L and 33 coauthors
  2. "The TESS-HERMES survey Data Release 1: high-resolution spectroscopy of the TESS southern continuous viewing zone", Monthly Notices of the Royal Astronomical Society 2017, Sharma, S and 23 coauthors
  3. "Calibrations of Atmospheric Parameters Obtained from the First Year of SDSS-III APOGEE Observations", Astrophysical Journal 2013, Meszaros, S and 27 coauthors

 

Recent publications on Galactic archaeology

  1. "Purveyors of fine halos: Re-assessing globular cluster contributions to the Milky Way halo build-up with SDSS-IV", Astronomy & Astrophysics 2019, Koch, A, Grebel, E and Martell, S L
  2. "The GALAH survey: Co-orbiting stars and chemical tagging", Monthly Notices of the Royal Astronomical Society 2019, Simpson, J D, Martell, S L and 25 coauthors
  3. "ESO 452-SC11: The lowest mass globular cluster with a potential chemical inhomogeneity", Monthly Notices of the Royal Astronomical Society 2017, Simpson, J D, De Silva, G M, Martell, S L, Navin, C A and Zucker, D B
  4. "A broad perspective on multiple abundance populations in the globular cluster NGC 1851", Monthly Notices of the Royal Astronomical Society 2017, Simpson, J D, Martell, S L and Navin, C A
  5. "Chemical tagging in the SDSS-III/APOGEE survey: New identifications of halo stars with globular cluster origins", Astrophysical Journal 2017, Martell S L and 8 coauthors