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J. M. Guie, S. J. Kannappan (UT Austin)
In a previous study of the frequency of gas-stellar counterrotation for a sample of E/S0 and spiral galaxies from the Nearby Field Galaxy Survey, counterrotation was found to occur primarily in low-luminosity early-type systems. However, no conclusions on counterrotation frequency could be reached for later type low-luminosity galaxies, due to inadequate sampling of their stellar kinematics. We present new stellar kinematic data for 10 late-type dwarf galaxies from the Nearby Field Galaxy Survey, obtained with the FAST spectrograph on the 60 inch telescope on Mount Hopkins. Our sample consists of galaxies with absolute B magnitudes between -16.5 and -19.1, and B-band effective surface brightnesses between 20.8 and 23.6. Of these, seven are classified as type Sdm-Im and three are classified as type Pec. We attempt to measure both gas and stellar rotation curves using emission and absorption lines in the 4000-6000 Angstrom range. All galaxies with well defined gas and stellar rotation show kinematics consistent with co-rotation. However, we see preliminary evidence of decoupled gas and stellar kinematics in some systems. We relate our results to plausible scenarios for the origin of kinematically decoupled gas, including late-stage gas accretion and galaxy mergers.
In addition, we examine new, deeper stellar kinematic data for the four E/S0 galaxies in the Nearby Field Galaxy Survey with previously identified gas-stellar counterrotation, in order to search for stellar-stellar counterrotation. We present preliminary results from this analysis.
JMG acknowledges support under NSF grant AST-0444634. SJK acknowledges support as an NSF Astronomy & Astrophysics Postdoctoral Fellow under grant AST-0401547.
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Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.