Dissecting the Homunculus nebula around Eta Carinae with spatially resolved near-infrared spectroscopy

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Abstract

Near-infrared emission lines are unique diagnostics of the geometry, structure, kinematics, and excitation of the circumstellar ejecta of η Carinae, and give clues to the nature of its wind. The infrared spectrum is a strong function of position in η Car's nebula, with a mix of intrinsic and reflected emission. Molecular hydrogen traces cool gas and dust in the polar lobes, while [Fe II] blankets their inner surfaces. These lines reveal the back wall of the SE polar lobe for the first time, and give the clearest picture yet of the three-dimensional geometry. Additionally collisionally excited [Fe II] reveals the kinematic structure of a recently discovered 'Little Homunculus' expanding inside the larger one. Equatorial gas in the 'Fan', on the other hand, shows a spectrum indicating recombination and fluorescent Lyα pumping. Some equatorial ejecta glow in the He I λ10830 line, showing evidence for material ejected in the 1890 outburst of η Car Closer to the star, the compact 'Weigelt blobs' are marginally resolved, allowing their infrared spectrum to be separated from the star for the first time. In general, infrared spectra reveal a coherent, directional dependence of excitation in the Homunculus: polar ejecta are collisionally excited, whereas equatorial ejecta are dominated by fluorescence and normal photoexcitation. These are important clues to the geometry of the central star's ultraviolet radiation field. Reflected near-infrared emission lines also reveal interesting latitudinal dependence in the stellar wind.

Original languageEnglish (US)
Pages (from-to)1252-1268
Number of pages17
JournalMonthly Notices of the Royal Astronomical Society
Volume337
Issue number4
DOIs
StatePublished - Dec 21 2002
Externally publishedYes

Fingerprint

ejecta
nebulae
infrared spectroscopy
near infrared
infrared spectra
geometry
stars
lobes
automobile
kinematics
blankets
stellar winds
ultraviolet radiation
photoexcitation
fans
gases
gas
outburst
radiation distribution
recombination

Keywords

  • Circumstellar matter
  • Reflection nebulae
  • Stars: individual: η Car
  • Stars: mass-loss
  • Stars: winds, outflows

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

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title = "Dissecting the Homunculus nebula around Eta Carinae with spatially resolved near-infrared spectroscopy",
abstract = "Near-infrared emission lines are unique diagnostics of the geometry, structure, kinematics, and excitation of the circumstellar ejecta of η Carinae, and give clues to the nature of its wind. The infrared spectrum is a strong function of position in η Car's nebula, with a mix of intrinsic and reflected emission. Molecular hydrogen traces cool gas and dust in the polar lobes, while [Fe II] blankets their inner surfaces. These lines reveal the back wall of the SE polar lobe for the first time, and give the clearest picture yet of the three-dimensional geometry. Additionally collisionally excited [Fe II] reveals the kinematic structure of a recently discovered 'Little Homunculus' expanding inside the larger one. Equatorial gas in the 'Fan', on the other hand, shows a spectrum indicating recombination and fluorescent Lyα pumping. Some equatorial ejecta glow in the He I λ10830 line, showing evidence for material ejected in the 1890 outburst of η Car Closer to the star, the compact 'Weigelt blobs' are marginally resolved, allowing their infrared spectrum to be separated from the star for the first time. In general, infrared spectra reveal a coherent, directional dependence of excitation in the Homunculus: polar ejecta are collisionally excited, whereas equatorial ejecta are dominated by fluorescence and normal photoexcitation. These are important clues to the geometry of the central star's ultraviolet radiation field. Reflected near-infrared emission lines also reveal interesting latitudinal dependence in the stellar wind.",
keywords = "Circumstellar matter, Reflection nebulae, Stars: individual: η Car, Stars: mass-loss, Stars: winds, outflows",
author = "Nathan Smith",
year = "2002",
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doi = "10.1046/j.1365-8711.2002.05966.x",
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T1 - Dissecting the Homunculus nebula around Eta Carinae with spatially resolved near-infrared spectroscopy

AU - Smith, Nathan

PY - 2002/12/21

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N2 - Near-infrared emission lines are unique diagnostics of the geometry, structure, kinematics, and excitation of the circumstellar ejecta of η Carinae, and give clues to the nature of its wind. The infrared spectrum is a strong function of position in η Car's nebula, with a mix of intrinsic and reflected emission. Molecular hydrogen traces cool gas and dust in the polar lobes, while [Fe II] blankets their inner surfaces. These lines reveal the back wall of the SE polar lobe for the first time, and give the clearest picture yet of the three-dimensional geometry. Additionally collisionally excited [Fe II] reveals the kinematic structure of a recently discovered 'Little Homunculus' expanding inside the larger one. Equatorial gas in the 'Fan', on the other hand, shows a spectrum indicating recombination and fluorescent Lyα pumping. Some equatorial ejecta glow in the He I λ10830 line, showing evidence for material ejected in the 1890 outburst of η Car Closer to the star, the compact 'Weigelt blobs' are marginally resolved, allowing their infrared spectrum to be separated from the star for the first time. In general, infrared spectra reveal a coherent, directional dependence of excitation in the Homunculus: polar ejecta are collisionally excited, whereas equatorial ejecta are dominated by fluorescence and normal photoexcitation. These are important clues to the geometry of the central star's ultraviolet radiation field. Reflected near-infrared emission lines also reveal interesting latitudinal dependence in the stellar wind.

AB - Near-infrared emission lines are unique diagnostics of the geometry, structure, kinematics, and excitation of the circumstellar ejecta of η Carinae, and give clues to the nature of its wind. The infrared spectrum is a strong function of position in η Car's nebula, with a mix of intrinsic and reflected emission. Molecular hydrogen traces cool gas and dust in the polar lobes, while [Fe II] blankets their inner surfaces. These lines reveal the back wall of the SE polar lobe for the first time, and give the clearest picture yet of the three-dimensional geometry. Additionally collisionally excited [Fe II] reveals the kinematic structure of a recently discovered 'Little Homunculus' expanding inside the larger one. Equatorial gas in the 'Fan', on the other hand, shows a spectrum indicating recombination and fluorescent Lyα pumping. Some equatorial ejecta glow in the He I λ10830 line, showing evidence for material ejected in the 1890 outburst of η Car Closer to the star, the compact 'Weigelt blobs' are marginally resolved, allowing their infrared spectrum to be separated from the star for the first time. In general, infrared spectra reveal a coherent, directional dependence of excitation in the Homunculus: polar ejecta are collisionally excited, whereas equatorial ejecta are dominated by fluorescence and normal photoexcitation. These are important clues to the geometry of the central star's ultraviolet radiation field. Reflected near-infrared emission lines also reveal interesting latitudinal dependence in the stellar wind.

KW - Circumstellar matter

KW - Reflection nebulae

KW - Stars: individual: η Car

KW - Stars: mass-loss

KW - Stars: winds, outflows

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