TY - JOUR
T1 - Diffuse ionized gas in irregular galaxies. I. GR 8 and ESO 245-G05
AU - Hidalgo-Gámez, A. M.
PY - 2006/4
Y1 - 2006/4
N2 - We have studied the spectral characteristics of the diffuse ionized gas (DIG) in two irregular galaxies with low metallicities and intermediate star formation rates: ESO 245-G05 and GR 8. The [O III]/Hβ ratio in these galaxies is higher than in the DIG of spiral galaxies but not as high as in other irregular galaxies previously studied, such as IC 10 and NGC 6822. The [N II]/Hα and [S II]/Hα ratios have very small values, indicating the absence of shocks as the ionization source for this gas. This ionization can be explained in both galaxies with photon leakage from the H II regions as the only source. The percentage of photons that have escaped from the H II regions is small in ESO 245-G05, only 35%, but varies from 35% up to 60% in GR 8. We also investigated whether the differences found between spiral and irregular galaxies in the [O III]/Hβ and the [N II]/Hα ratios are due to differences in the metal content between these types of galaxies. Although the number of galaxies studied is not very large, it can be concluded that the [O III]/Hβ ratio is not related to the oxygen content, while the situation is more ambiguous for the [N II]/Hα ratio.
AB - We have studied the spectral characteristics of the diffuse ionized gas (DIG) in two irregular galaxies with low metallicities and intermediate star formation rates: ESO 245-G05 and GR 8. The [O III]/Hβ ratio in these galaxies is higher than in the DIG of spiral galaxies but not as high as in other irregular galaxies previously studied, such as IC 10 and NGC 6822. The [N II]/Hα and [S II]/Hα ratios have very small values, indicating the absence of shocks as the ionization source for this gas. This ionization can be explained in both galaxies with photon leakage from the H II regions as the only source. The percentage of photons that have escaped from the H II regions is small in ESO 245-G05, only 35%, but varies from 35% up to 60% in GR 8. We also investigated whether the differences found between spiral and irregular galaxies in the [O III]/Hβ and the [N II]/Hα ratios are due to differences in the metal content between these types of galaxies. Although the number of galaxies studied is not very large, it can be concluded that the [O III]/Hβ ratio is not related to the oxygen content, while the situation is more ambiguous for the [N II]/Hα ratio.
KW - Galaxies: individual (GR 8, ESO 245-G05)
KW - Galaxies: irregular
KW - H II regions
UR - http://www.scopus.com/inward/record.url?scp=33744473572&partnerID=8YFLogxK
U2 - 10.1086/500810
DO - 10.1086/500810
M3 - Artículo
SN - 0004-6256
VL - 131
SP - 2078
EP - 2088
JO - Astronomical Journal
JF - Astronomical Journal
IS - 4
ER -