Evidence for the disky origin of luminous Virgo dwarf ellipticals from the kinematics of their globular cluster systems

TL;DR

This study provides evidence that luminous Virgo dwarf ellipticals have rotating globular cluster systems and stellar components, supporting the idea that they originate from transformed disk galaxies, with globular clusters serving as sensitive dynamical probes.

Contribution

It demonstrates the presence of significant rotation in globular cluster systems and stellar components of luminous Virgo dwarf ellipticals, linking their dynamics to disk galaxy origins.

Findings

Globular cluster systems exhibit v_rot/sigma > 1, indicating significant rotation.

Both galaxies show rapid rotation in their inner stellar regions.

Globular clusters extend further out and are sensitive probes of galaxy dynamics.

Abstract

We report evidence for dynamically significant rotation in the globular cluster systems of two luminous Virgo dwarf ellipticals, VCC1261 and VCC1528. Including previous results for VCC1087, the globular cluster systems of all three Virgo dwarf ellipticals studied in detail to date exhibit v_rot/sigma > 1. Taking the rotation seen in the globular clusters as maximal disk rotation, we find all three dEs lie on the r-band Tully-Fisher relation. We argue that these data support the hypothesis that luminous dEs are the remnants of transformed disk galaxies. We also obtained deep, longslit data for the stars in VCC1261 and VCC1528. Both these galaxies show rapid rotation in their inner regions, with spatial scales of ~0.5 kpc. These rotation velocities are similar to those seen in the GC systems. Since our longslit data for Virgo dEs extend out to 1-2 effective radii (typical of deep observations), whereas the globular clusters extend out to 4--7 effective radii, we conclude that non-detections of rotation in many luminous dEs may simply be due to a lack of radial coverage in the stellar data, and that globular clusters represent singularly sensitive probes of the dynamics of dEs. Based on these data, we suggest that gas disks are significant sites of globular cluster formation in the early universe.