Hen 2–104: a close-up look at the Southern Crab*
Isaac Newton Group of Telescopes, Ap. de Correos 321, 38700 Sta. Cruz de la Palma, Spain e-mail: [msantander;rcorradi;mischa]@ing.iac.es
2 Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain e-mail: [miguelsg;amr]@iac.es
3 Instituto de Astronomía, Universidad Nacional Autónoma de México, México, D. F., México e-mail: email@example.com
4 INAF Osservatorio Astronomico di Padova, via dell'Osservatorio 8, 36012 Asiago (VI), Italy e-mail: firstname.lastname@example.org
5 Department of Astronomy, University of Washington, Seattle, Washington 98195-1580, USA e-mail: email@example.com
6 Space Telescope Science Institute (STScI), 3700 San Martin Drive, Baltimore, MD 21218, USA e-mail: firstname.lastname@example.org
Accepted: 25 February 2008
Aims. The kinematics, shaping, density distribution, expansion distance, and ionized mass of the nebula Hen 2–104, and the nature of its symbiotic Mira are investigated.
Methods. A combination of multi-epoch HST images and VLT integral field high-resolution spectroscopy is used to study the nebular dynamics both along the line of sight and in the plane of the sky. These observations enable a 3-D spatio-kinematical model of the nebula to be constructed, which, with the measurement of its apparent expansion in the plane of the sky over a period of 4 years, provides the expansion parallax for the nebula. The integral-field data featuring the [Sii] 671.7, 673.1 emission line doublet provide a density map of the inner lobes of the nebula, which with the distance estimation provide a measurement of its ionized mass.
Results. We measure densities ranging from to 1000 cm-3 in the inner lobes, and from 300 to 500 cm-3 in the outer lobes. We determine an expansion-parallax distance of kpc to Hen 2–104, which implies an unexpectedly large ionized mass for the nebula of approximately one tenth of a solar mass.
Key words: stars: binaries: symbiotic / ISM: planetary nebulae: general / ISM: kinematics and dynamics
Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract No. NAS5-26555; and on observations obtained at the 4 m NTT and the 8 m VLT telescopes of the European Southern Observatory in Chile.
© ESO, 2008