Chemical composition of H ii regions in the Small Magellanic Cloud and the pregalactic helium abundance

Journal Article · Sun Feb 01 04:00:00 EST 1976 · Astrophys. J., v. 203, no. 3, pp. 581-586

DOI:https://doi.org/10.1086/154114· OSTI ID:4026746

Peimbert, M; Torres-Peimbert, S

Photoelectric spectrophotometry of emission lines in the 3700--7400 A range is presented for NGC 346, NGC 356, and NGC 456 in the Small Magellanic Cloud (SMC). The observations were obtained at CTIO with the 60 inch (1.5 m) telescope and the Harvard scanner. From these observations the chemical abundances of He, N, O, Ne, S, and Ar relative to hydrogen are derived. It is found that N (He)/N (H) =0.078 +- 0.005 for the three H ii regions is the SMC; this value is about 25 percent smaller than the values for the Orion and eta Car nebulae. Oxygen and neon are underabundant by a factor of 7, while nitrogen is underabundant by a factor of 15 in the SMC H ii regions with respect to the values for the Orion Nebula. From the chemical composition of H ii regions in our Galaxy and the Magellanic Clouds it is found that the pregalactic value of N (He)/N(H) is 0.074 +- 0.006 (Y=0.228 +- 0.014). The cosmological implications of this result are briefly discussed. (AIP)

• Research Organization: Instituto de Astronomia, Universidad Nacional Autonoma de Mexico
• Sponsoring Organization: USDOE
• NSA Number: NSA-33-030816
• OSTI ID: 4026746
• Journal Information: Astrophys. J., v. 203, no. 3, pp. 581-586, Journal Name: Astrophys. J., v. 203, no. 3, pp. 581-586; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

*H2 REGIONS-- CHEMICAL COMPOSITION
640105* --Physics Research--Astrophysics & Cosmology-- Galaxies
ABUNDANCE
ARGON
COSMOLOGY
EMISSION SPECTRA
HELIUM
HYDROGEN
MAGELLANIC CLOUDS
N56500* --Physics (Astrophysics & Cosmology)--Galaxies
N56600 --Physics (Astrophysics & Cosmology)--Cosmology
NEBULAE
NEON
NITROGEN
OXYGEN
PHOTOMETRY
SULFUR