Bibcode
Diaz, Angeles I.; Terlevich, Elena; Pagel, B. E. J.; Vilchez, Jose M.; Edmunds, Michael G.
Bibliographical reference
Monthly Notices of the Royal Astronomical Society (ISSN 0035-8711), vol. 226, May 1, 1987, p. 19-37.
Advertised on:
5
1987
Citations
103
Refereed citations
94
Description
Detailed spectrophotometry in the visual and near-infrared is presented
for four different slit positions over the core of NGC 604. The
excitation ([O II]/[O III]) varies considerably both along the slit and
between different slit positions, but the line ratios ([O II]+[O
III])/Hβ, [N II]/[O II], [N II]/[S II] and ([O
II]/Hβ)×([O II]/[S II]) are effectively constant, confirming
the suitability of these line ratios as abundance-related parameters
characterizing an entire giant H II region. The [O III] electron
temperature shows significant variations across the nebula, but no
significant variations in relative abundances of O, N, Ne and S are
found. By introducing a new ionization correction scheme the authors
determine a helium abundance Y = 0.260±0.013 and this is also
constant except possibly in one place where the correction for neutral
helium is very uncertain. The spectrum is consistent with ionizing stars
having a representative effective temperature of 40000K (blanketed LTE
models) or 37000K (non-LTE models).