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

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)

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

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

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.

Rotation in VCC 1528 PA ~ 28 deg from gal major axis (dE1) vrot ~ 90 - 180 km/s (depending on fit) can’t measure ! Assuming < 30 km/s --> v/ > 3 - 6

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

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.