SDSS Globular Cluster Candidates Around M31

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SDSS Globular Cluster Candidates Around M31

• S.A. Bates
• J.A. Holtzman
• R.A.M. Walterbos
• NMSU
• APO
• May 2004

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Scientific Motivation

• SDSS scanned 2.6 x 18 degrees around M31 in Fall
  2002
• To use the large extent of the SDSS scan to
  locate new globular clusters at large radii

• Recent INT survey found clusters
• Halo clusters can help to better constrain the
  mass and chemical composition of M31 and the
  origin of clusters

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Procedure

• Matched known clusters to SDSS objects
• 2 arcsec distance
• magnitude range r(v-0.25) or brightest
• Plot clusters in multi-dimensional space
• object type, Petrosian radius, magnitude, color,
  ellipticity, r90/r50
• Choose candidates based upon concentration of
  clusters
• Final list of candidates
• eliminate objects scan ends and cluster
  duplicates
• visual inspection
• FWHM
• Spectra taken of two candidates last month at APO

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Selection

• Criteria
• GALAXY classification
• 2 lt Petrosian radius lt 5
• 2 lt r90/r50 lt 3
• ellipticity gt 0.8
• r lt 18

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Selection

• Color Criteria
• (g-r)-2(r-i) lt 0.5
• (u-r-1)-4(r-i) lt 0.75

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Previously Confirmed Clusters
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New Clusters

• 3367-r6-0051
• velocity
• large Balmer absorption lines

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New Clusters

• 3366-r2-0104
• velocity

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New Clusters

• 3367-r3-0061
• velocity

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Positions

• New clusters at large projected galactocentric
  radii

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Future Work

• Follow-up spectroscopy at APO next fall
• Bruzual Charlot stellar population synthesis
  models