Evidence for Stellar Streaming in the Cores of Elliptical Galaxies: A Kinematic Signature of Mergers?
We present evidence for non-Gaussian velocity fields within the cores of luminous elliptical galaxies. This evidence is based on high signal-to-noise ratio, medium-resolution spectroscopy of the cores of early-type members of the Virgo and Coma Clusters obtained with the Wisconsin-Indiana-Yale-NOAO 3.5 m telescope. The Virgo data were acquired using an integral-field unit (DensePak), which allows the velocity field to be sampled over a variety of spatial scales. The Coma data were obtained through single 2&arcsec; diameter fibers. The cross-correlation profiles of luminous elliptical galaxies show considerable structure, often having several features with amplitudes as high as 10% that of the cross-correlation peak itself. This structure is most obvious within a radius of 1&farcs;5 (at Virgo), or </=100 pc, and is nearly undetectable when the data are binned over R<15", or </=1 kpc. Similar features are found in the single-fiber spectra of the luminous elliptical galaxies in the Coma Cluster, suggesting that they are ubiquitous in giant elliptical galaxies. Interestingly, only the most luminous elliptical galaxies show these phenomena; the central regions of lower luminosity elliptical galaxies have regular Gaussian-like profiles. We interpret this kinematic structure as "stellar streaming" and suggest that these phenomena could be a relic signature of the merger history of luminous elliptical galaxies.
Pierce
MJ
Berrington
RC