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....