Gradients in the physical conditions of M101 and the pregalactic helium abundance

Journal Article · Thu Apr 01 04:00:00 EST 1982 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/159796· OSTI ID:5129305

Rayo, J F; Peimbert, M; Torres-Peimbert, S

Photoelectric spectrophotometry in the 3400-7400 A range is presented for five H II regions and the nucleus of M101. The abundances of He, N, O, Ne, S, and Ar relative to H are derived for three of the H II regions. Gradients were found in: electron temperature, He/H, N/H, O/H, S/H, and Ar/H. It was found that for a given O/H the N/O values are smaller in M101 than in the Galaxy, probably indicating that on the average the stellar population of M101 is younger than that of the Galaxy. For the first time the effects due to He and H stellar underlying emission and absorption in the N(He)/N(H) ratio were estimated quantitatively and they were found to be almost negligible. A pregalactic helium abundance of Y/sub p/ = 0.216 +- 0.0010 (3sigma) was derived.

• Research Organization: Instituto de Astronomia, Universidad Nacional Autonoma de Mexico
• OSTI ID: 5129305
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 255:1; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABUNDANCE
BALMER LINES
CHEMICAL COMPOSITION
COSMIC RADIO SOURCES
ELEMENTS
FLUIDS
GALACTIC EVOLUTION
GALAXIES
GALAXY NUCLEI
GASES
H2 REGIONS
HELIUM
HYDROGEN
NONMETALS
RARE GASES
SPECTRA
SPECTROPHOTOMETRY
VISIBLE SPECTRA