A census of the Carina Nebula - II. Energy budget and global properties of the nebulosity

Nathan Smith, Kate J. Brooks

Research output: Contribution to journalArticle

62 Citations (Scopus)

Abstract

The first paper in this series took a direct census of energy input from the known OB stars in the Carina Nebula, and in this paper we study the global properties of the surrounding nebulosity. This detailed comparison may prove useful for interpreting observations of extragalactic giant H ii regions and ultraluminous infrared (IR) galaxies. We find that the total IR luminosity of Carina is about 1.2 × 107 L⊙, accounting for only about 50-60 per cent of the known stellar luminosity from Paper I. Similarly, the ionizing photon luminosity derived from the integrated radio continuum is about 7 × 1050 s-1, accounting for ∼75 per cent of the expected Lyman continuum from known OB stars. The total kinetic energy of the nebula is about 8 × 1051 erg, or ∼30 per cent of the mechanical energy from stellar winds over the lifetime of the nebula, so there is no need to invoke a supernova (SN) explosion based on energetics. Warm dust grains residing in the H ii region interior dominate emission at 10-30 μm, but cooler grains at 30-40 K dominate the IR luminosity and indicate a likely gas mass of ∼106 M⊙. We find an excellent correlation between the radio continuum and 20-25 μm emission, consistent with the idea that the ∼80-K grain population is heated by trapped Lyα photons. Similarly, we find a near perfect correlation between the far-IR optical depth map of cool grains and 8.6-μm hydrocarbon emission, indicating that most of the nebular mass resides as atomic gas in photodissociation regions and not in dense molecular clouds. Synchronized star formation around the periphery of Carina provides a strong case that star formation here was indeed triggered by stellar winds and ultraviolet radiation. This second generation appears to involve a cascade toward preferentially intermediate- and low-mass stars, but this may soon change when η Carinae and its siblings explode. If the current reservoir of atomic and molecular gas can be tapped at that time, massive star formation may be rejuvenated around the periphery of Carina much as if it were a young version of Gould's Belt. Furthermore, when these multiple SNe occur, the triggered second generation will be pelted repeatedly with SN ejecta bearing short-lived radioactive nuclides. Carina may therefore represent the most observable analogue to the cradle of our own Solar system.

Original languageEnglish (US)
Pages (from-to)1279-1292
Number of pages14
JournalMonthly Notices of the Royal Astronomical Society
Volume379
Issue number4
DOIs
StatePublished - Aug 2007
Externally publishedYes

Fingerprint

census
energy budgets
nebulae
energy budget
star formation
monatomic gases
luminosity
stellar winds
continuums
stars
supernovae
gas
radio
stellar luminosity
photons
ejecta
ultraviolet radiation
molecular gases
molecular clouds
coolers

Keywords

  • H II regions
  • ISM: individual: NGC 3372
  • Stars: formation

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

A census of the Carina Nebula - II. Energy budget and global properties of the nebulosity. / Smith, Nathan; Brooks, Kate J.

In: Monthly Notices of the Royal Astronomical Society, Vol. 379, No. 4, 08.2007, p. 1279-1292.

Research output: Contribution to journalArticle

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abstract = "The first paper in this series took a direct census of energy input from the known OB stars in the Carina Nebula, and in this paper we study the global properties of the surrounding nebulosity. This detailed comparison may prove useful for interpreting observations of extragalactic giant H ii regions and ultraluminous infrared (IR) galaxies. We find that the total IR luminosity of Carina is about 1.2 × 107 L⊙, accounting for only about 50-60 per cent of the known stellar luminosity from Paper I. Similarly, the ionizing photon luminosity derived from the integrated radio continuum is about 7 × 1050 s-1, accounting for ∼75 per cent of the expected Lyman continuum from known OB stars. The total kinetic energy of the nebula is about 8 × 1051 erg, or ∼30 per cent of the mechanical energy from stellar winds over the lifetime of the nebula, so there is no need to invoke a supernova (SN) explosion based on energetics. Warm dust grains residing in the H ii region interior dominate emission at 10-30 μm, but cooler grains at 30-40 K dominate the IR luminosity and indicate a likely gas mass of ∼106 M⊙. We find an excellent correlation between the radio continuum and 20-25 μm emission, consistent with the idea that the ∼80-K grain population is heated by trapped Lyα photons. Similarly, we find a near perfect correlation between the far-IR optical depth map of cool grains and 8.6-μm hydrocarbon emission, indicating that most of the nebular mass resides as atomic gas in photodissociation regions and not in dense molecular clouds. Synchronized star formation around the periphery of Carina provides a strong case that star formation here was indeed triggered by stellar winds and ultraviolet radiation. This second generation appears to involve a cascade toward preferentially intermediate- and low-mass stars, but this may soon change when η Carinae and its siblings explode. If the current reservoir of atomic and molecular gas can be tapped at that time, massive star formation may be rejuvenated around the periphery of Carina much as if it were a young version of Gould's Belt. Furthermore, when these multiple SNe occur, the triggered second generation will be pelted repeatedly with SN ejecta bearing short-lived radioactive nuclides. Carina may therefore represent the most observable analogue to the cradle of our own Solar system.",
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