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S.A.Bates J.A. Holtzman R.A.M. Walterbos SDSS M31 collaborators APO May 2004. APO 3.5m Follow UP Of SDSS Observations: Confirmation of Newly Discovered Globular Clusters in the Andromeda Galaxy. M31 has population of globular clusters like Milky Way, but more of them - PowerPoint PPT Presentation
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APO 3.5m Follow UP Of SDSS Observations:
Confirmation of Newly Discovered Globular Clusters in the
Andromeda GalaxyS.A.Bates
J.A. HoltzmanR.A.M. Walterbos
SDSS M31 collaborators
APOMay 2004
M31 has population of globular clusters like Milky Way, but more of them
Distribution of GCs in Milky Way suggests distant GCS in M31 may have yet to be found
Recent INT survey (Huxor et al.)found several new clustesr at largedistances
SDSS scanned 2.6x18 degrees along M31 major axis in fall 2002, but no followup spectroscopy
Distant clusters potentially important to constrain formation mechanism (clusters and galaxy) and mass/mass distribution in M31
ARC 3.5m well suited for spectroscopic followup/confirmation
Identifcation Procedure
Match known clusters to SDSS objects in photometry catalog2 arcsec distanceNearest in brightness to known cluster
Inspect clusters in multi-dimensional parameter spaceStructural parameters (object type, Petrosian radius, ellipticity, concentrationPopulation parameters (colors)Determine regions of parameter space inhabited by known clusters
Other objects in selected regions are cluster candidatesAdditional filtering/quality control from visual inspection
Confirm candidates spectroscopically with 3.5mInitial observation in February 2005 of 2 clusters appears to confirm them!
Structural parameters
Colors
SDSS Images of Previously Known Clusters
SDSS Images of New Candidate Clusters
ARC 3.5m DIS Spectra of Candidates
Short exposures of moderately bright objects on moderately cloudy night
Clear detection of strongest absorption features (Ca HK, G band, H beta
Velocities near systemic velocity of M31
Location of New Clusters in M31
New clusters at large projected galactocentric radii, 52 and 56 kpc!!
Possibly several dozen more to come!
Future Work
Follow-up spectroscopy of additional candidates at ARC 3.5m this fallPopulation studies using SDSS 5-color photometry and spectroscopic line strengthsDynamical modelling using 3.5m velocities
ARC 3.5m as a follow-up tool for SDSS
●High redshift quasars●Dynamical properties of galaxies●Supernovae type confirmation and spectroscopic light curves●Many others....