Penetrating the Homunculus, Near-Infrared Adaptive Optics Images of Eta Carinae

Artigau, Étienne [1]; Martin, John C. [2]; Humphreys, Roberta M. [3]; Davidson, Kris [3]; Chesneau, Olivier [4]; Smith, Nathan[5]

[1] Gemini Observatory-South and Département de Physique and Observatoire du Mont Mégantic, Université de Montréal
[2] Department of Physics and Astronomy, University of Illinois-Springfield
[3] Astronomy Department, University of Minnesota
[4] H. Fizeau, Univ. Nice Sophia Antipolis, CNRS, Observatoire de la Côte d'Azur, France
[5] Astronomy Department, University of California, Berkeley

Near-infrared adaptive optics imaging with the Near-Infrared Coronagraphic Imager (NICI) and NaCO reveal what appears to be a three-winged or lobed pattern, the "butterfly nebula," outlined by bright Brγ and H2 emission and light scattered by dust. In contrast, the [Fe II] emission does not follow the outline of the wings, but shows an extended bipolar distribution which is tracing the Little Homunculus ejected in η Car's second or lesser eruption in the 1890s. Proper motions measured from the combined NICI and NaCO images together with radial velocities show that the knots and filaments that define the bright rims of the butterfly were ejected at two different epochs corresponding approximately to the great eruption and the second eruption. Most of the material is spatially distributed 10°-20° above and below the equatorial plane apparently behind the Little Homunculus and the larger SE lobe. The equatorial debris either has a wide opening angle or the clumps were ejected at different latitudes relative to the plane. The butterfly is not a coherent physical structure or equatorial torus but spatially separate clumps and filaments ejected at different times, and now 2000-4000 AU from the star.

Reference: The Astronomical Journal, Volume 141, Issue 6, article id. 202 (2011)
Status: Manuscript has been accepted