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Article: A spectroscopic study of the bipolar planetary nebula Mz 3

TitleA spectroscopic study of the bipolar planetary nebula Mz 3
Authors
KeywordsIsm: Abundances
Ism: Lines And Bands
Line: Identification
Planetary Nebulae: Individual: Mz 3
Issue Date2002
PublisherBlackwell Publishing Ltd. The Journal's web site is located at http://www.blackwellpublishing.com/journals/MNR
Citation
Monthly Notices Of The Royal Astronomical Society, 2002, v. 337 n. 2, p. 499-518 How to Cite?
AbstractWe have obtained a medium-resolution, deep optical long-slit spectrum of the bipolar planetary nebula Mz 3. The spectrum covers the wavelength range 3420-7400 Å. Over 200 emission lines have been detected, many of them permitted and forbidden transitions from Fe +, Fe 2+ and Fe 3+ and other iron-group elements. The spectra have been used to determine nebular thermal and density structures and elemental abundances. The very rich and prominent [Fe III] emission lines observed in the optical spectrum of Mz 3 are found to originate exclusively from an unresolved emission region centred on the central star. The relative intensities of [Fe III] lines arising from the same upper level are in good agreement with the theoretical predictions. The [Fe III] lines detected in Mz 3, arising from levels of different excitation energies and critical densities, provide powerful diagnostic tools to probe the physical conditions in the central emitting region. We find that all the observed [Fe III] diagnostic line ratios consistently yield an electron temperature of T e = 11 000 K and a density of log N e(cm -3) = 6.5. The latter value is close to the densities where the ratios of these [Fe III] diagnostic lines are most sensitive to density variations, suggesting that the density in the central emission core could be even higher. In contrast, all the other standard nebular density- and temperature-diagnostic line ratios, all of lower critical densities than the [Fe III] lines and therefore only useful at densities ≤ 10 6 cm -3, yield consistently lower electron densities, with the resultant values correlating with their critical densities. This indicates that the central dense emission core has a highly stratified density structure such that forbidden lines of relatively low critical densities are collisionally suppressed in high-density regions. Given the highly stratified thermal and density structures of the core emission region, no reliable elemental abundances can be determined for this region, except possibly for iron, for which we find an abundance of approximately half the solar value. In contrast to the dense central core, emission from the extended bipolar lobes of Mz 3 are well represented by a mean electron temperature of 6800 K and density of 5200 cm -3. The elemental abundances derived for this region, on a logarithmic scale where H = 12, are He = 10.93, C = 8.41, N = 8.37, O = 8.50, Ne = 7.64, S = 7.15, Cl = 5.28 and Ar = 7.14. In all cases, the abundances are close to the average values deduced for Galactic planetary nebulae. In particular, there is no evidence of He enrichment, as claimed in previous studies. The newly derived heavy-element abundances are significantly higher than those published in the literature. In those earlier studies, as a result of the contamination of emission from the dense central core, the average electron temperature in Mz 3 was significantly overestimated, resulting in grossly underestimated heavy-element abundances. However, Mz 3 does seem to have a relatively high N/O abundance ratio, in line with the result derived from the ISO observations of the far-infrared fine-structure lines.
Persistent Identifierhttp://hdl.handle.net/10722/174844
ISSN
2015 Impact Factor: 4.952
2015 SCImago Journal Rankings: 2.806
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorZhang, Yen_US
dc.contributor.authorLiu, XWen_US
dc.date.accessioned2012-11-26T08:47:46Z-
dc.date.available2012-11-26T08:47:46Z-
dc.date.issued2002en_US
dc.identifier.citationMonthly Notices Of The Royal Astronomical Society, 2002, v. 337 n. 2, p. 499-518en_US
dc.identifier.issn0035-8711en_US
dc.identifier.urihttp://hdl.handle.net/10722/174844-
dc.description.abstractWe have obtained a medium-resolution, deep optical long-slit spectrum of the bipolar planetary nebula Mz 3. The spectrum covers the wavelength range 3420-7400 Å. Over 200 emission lines have been detected, many of them permitted and forbidden transitions from Fe +, Fe 2+ and Fe 3+ and other iron-group elements. The spectra have been used to determine nebular thermal and density structures and elemental abundances. The very rich and prominent [Fe III] emission lines observed in the optical spectrum of Mz 3 are found to originate exclusively from an unresolved emission region centred on the central star. The relative intensities of [Fe III] lines arising from the same upper level are in good agreement with the theoretical predictions. The [Fe III] lines detected in Mz 3, arising from levels of different excitation energies and critical densities, provide powerful diagnostic tools to probe the physical conditions in the central emitting region. We find that all the observed [Fe III] diagnostic line ratios consistently yield an electron temperature of T e = 11 000 K and a density of log N e(cm -3) = 6.5. The latter value is close to the densities where the ratios of these [Fe III] diagnostic lines are most sensitive to density variations, suggesting that the density in the central emission core could be even higher. In contrast, all the other standard nebular density- and temperature-diagnostic line ratios, all of lower critical densities than the [Fe III] lines and therefore only useful at densities ≤ 10 6 cm -3, yield consistently lower electron densities, with the resultant values correlating with their critical densities. This indicates that the central dense emission core has a highly stratified density structure such that forbidden lines of relatively low critical densities are collisionally suppressed in high-density regions. Given the highly stratified thermal and density structures of the core emission region, no reliable elemental abundances can be determined for this region, except possibly for iron, for which we find an abundance of approximately half the solar value. In contrast to the dense central core, emission from the extended bipolar lobes of Mz 3 are well represented by a mean electron temperature of 6800 K and density of 5200 cm -3. The elemental abundances derived for this region, on a logarithmic scale where H = 12, are He = 10.93, C = 8.41, N = 8.37, O = 8.50, Ne = 7.64, S = 7.15, Cl = 5.28 and Ar = 7.14. In all cases, the abundances are close to the average values deduced for Galactic planetary nebulae. In particular, there is no evidence of He enrichment, as claimed in previous studies. The newly derived heavy-element abundances are significantly higher than those published in the literature. In those earlier studies, as a result of the contamination of emission from the dense central core, the average electron temperature in Mz 3 was significantly overestimated, resulting in grossly underestimated heavy-element abundances. However, Mz 3 does seem to have a relatively high N/O abundance ratio, in line with the result derived from the ISO observations of the far-infrared fine-structure lines.en_US
dc.languageengen_US
dc.publisherBlackwell Publishing Ltd. The Journal's web site is located at http://www.blackwellpublishing.com/journals/MNRen_US
dc.relation.ispartofMonthly Notices of the Royal Astronomical Societyen_US
dc.subjectIsm: Abundancesen_US
dc.subjectIsm: Lines And Bandsen_US
dc.subjectLine: Identificationen_US
dc.subjectPlanetary Nebulae: Individual: Mz 3en_US
dc.titleA spectroscopic study of the bipolar planetary nebula Mz 3en_US
dc.typeArticleen_US
dc.identifier.emailZhang, Y: zhangy96@hku.hken_US
dc.identifier.authorityZhang, Y=rp00841en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.1046/j.1365-8711.2002.05929.xen_US
dc.identifier.scopuseid_2-s2.0-0038480958en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-0038480958&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume337en_US
dc.identifier.issue2en_US
dc.identifier.spage499en_US
dc.identifier.epage518en_US
dc.identifier.isiWOS:000179494100013-
dc.publisher.placeUnited Kingdomen_US
dc.identifier.scopusauthoridZhang, Y=23768446500en_US
dc.identifier.scopusauthoridLiu, XW=7409287288en_US

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