1. Spectroscopy of GCs in Virgo dEs
Beasley et al 2006
Jay Strader, GC-Dwarf, 8/29/07
with M Beasley, M Geha, J Brodie

2. Origin of dEs Most common galaxy type in clusters…
Transformation of disk galaxies is a popular model.
Can happen quickly or slowly.
Model test: are dEs rotating? Results inconclusive. (Geha; van Zee)
Use GCs---larger radii for kinematics, plus some stellar pops.
Note reff only 15” (7” for V1261)
Keck/LRIS blue spectra of GC in VCC 1087
(Beasley et al. 2006)

3. Three Virgo dEs MB = -17.1 ~ 75 GCs Bimodal GC colors Not rotating
VCC 1087
VCC 1261
VCC 1528
MB = -17.1
~ 75 GCs
Bimodal GC colors
Not rotating
MB = -18.1
~ 55 GCs
Bimodal GC colors
Not rotating
MB = -16.8
~ 60 GCs
Mostly blue GCs
No published kin. data
V1261: not rot from van zee et al; V1087 from geha et al. No info on V1528 (published)
N1261: bright but has an exponential profile: looks like a dE

4. Rotation in VCC 1087
Solid-body fit gives vrot = 104 +/- 35 km/s to outermost GC
Error and rot-corrected  = 29 +/- 6
--> v/ = 3.6 +/- 1.8
Most rotationally supported GC system known!
Note reff only 15” (7” for V1261)
Beasley et al 2006

5. Rotation in VCC 1261 PA ~ 30 deg from gal major axis
vrot = 109 +/- 32 km/s excluding last GC
Error and rot-corrected  = 27 +/- 10
--> v/ = 4.0 +/- 1.9
Same as VCC 1087 to limit of the data.

6. Rotation in VCC 1528 PA ~ 28 deg from gal major axis (dE1)
vrot ~ km/s (depending on fit)
can’t measure !
Assuming < 30 km/s
--> v/ > 3 - 6

7. VCC1261: Zeroth-Order Ages
Age of red GCs ~ matches galaxy (Geha et al. )
Did the red GCs form in transformation process?

8. Conclusions Three dEs---three rotating disk systems of GCs.
these three (bright) Virgo dEs are probably transformed disks.
P.A.s ~ match those of galaxy (also Puzia et al 2000)
Some evidence that younger red GCs can form in the transformation process.
Pushing (much) fainter will be tough; few GCs.