2004MNRAS.351L..15S

High-resolution spectra of molecular hydrogen in the Homunculus nebula allow for the first direct measurement of the systemic velocity of η Carinae. Near-infrared long-slit data for H₂1-0 S(1) λ21218 obtained with the Phoenix spectrometer on the Gemini South telescope give V_sys=-8.1 ±1 km/s (heliocentric), or V_LSR=-19.7±1 km/s, from the average of the near and far sides of the Homunculus. This measurement considerably improves the precision for the value of -7±10 km/s inferred from neighbouring O-type stars in the Carina nebula. New near-infrared spectra also provide a high-resolution line profile of [Feii]λ16435 emission from gas condensations known as the Weigelt objects without contamination from the central star, revealing a line shape with complex kinematic structure. Previously, uncertainty in the kinematics of the Weigelt knots was dominated by the adopted systemic velocity of η Car.