The Classification of M 1-78

Gussie, Gt

doi:10.1017/s1323358000020014

Cited by 6 publications

(10 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Matsuura et al 2009). Many authors argue that CKs are largely responsible for the H 2 emission produced within the ionized region (Beckwith et al 1978; Gussie & Pritchet 1988; Reay et al 1988; Tielens 1993; Schild 1995; Speck et al 2002; Matsuura et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Modelling the warm H2 infrared emission of the Helix nebula cometary knots

Aleman

Zijlstra

Matsuura

et al. 2011

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

Molecular hydrogen emission is commonly observed in planetary nebulae. Images taken in infrared H2 emission lines show that at least part of the molecular emission is produced inside the ionized region. In the best studied case, the Helix nebula, the H2 emission is produced inside cometary knots (CKs), comet‐shaped structures believed to be clumps of dense neutral gas embedded within the ionized gas. Most of the H2 emission of the CKs seems to be produced in a thin layer between the ionized diffuse gas and the neutral material of the knot, in a mini‐photodissociation region (mini‐PDR). However, PDR models published so far cannot fully explain all the characteristics of the H2 emission of the CKs. In this work, we use the photoionization code Aangaba to study the H2 emission of the CKs, particularly that produced in the interface H+/H0 of the knot, where a significant fraction of the H2 1–0 S(1) emission seems to be produced. Our results show that the production of molecular hydrogen in such a region may explain several characteristics of the observed emission, particularly the high excitation temperature of the H2 infrared lines. We find that the temperature derived from H2 observations, even of a single knot, will depend very strongly on the observed transitions, with much higher temperatures derived from excited levels. We also proposed that the separation between the Hα and [N ii] peak emission observed in the images of CKs may be an effect of the distance of the knot from the star, since for knots farther from the central star the [N ii] line is produced closer to the border of the CK than Hα.

show abstract

Section: Introductionmentioning

confidence: 99%

Modelling the warm H2 infrared emission of the Helix nebula cometary knots

Aleman

Zijlstra

Matsuura

et al. 2011

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

show abstract

“…Although this fact was considered by Gussie (1995) as an indication of the PN nature of the object, such supersonic expansion velocities are also common in WR ring nebulae (e.g. Rosado 1986) as well as in LBV nebulae (e.g.…”

Section: Discussion: the Nature Of M1-78mentioning

confidence: 99%

“…Peeters et al 2002). Such a distance implies a high luminosity of about 2 × 10 5 L/L (see again Peeters et al 2002), which makes the classification of M1−78 as a PN untenable, as pointed out already by Zijlstra et al (1990) and Gussie (1995). A classification as an ultracompact H ii region 1 http://simbad.u-strasbg.fr/simbad/ is favored instead by these authors.…”

Section: Introductionmentioning

confidence: 92%

“…A classification as an ultracompact H ii region 1 http://simbad.u-strasbg.fr/simbad/ is favored instead by these authors. Gussie (1995) even favors a rather unique classification for this region, that of an ultracompact H ii region with a post-main sequence central star, probably a Wolf-Rayet (WR) star, based on the high expansion velocity of the nebula (around 25 km s −1 ) and a possible overabundance of nitrogen (see also Perinotto 1991).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

M1–78: a nitrogen-rich Galactic compact H II region beyond the Perseus arm

Martín-Hernández

Esteban

Mesa‐Delgado

et al. 2008

A&A

View full text Add to dashboard Cite

Context. There is considerable controversy surrounding the nature of M1−78, a compact nebula located beyond the Perseus arm. It was first classified as a planetary nebula and is nowadays generally considered to be a compact H ii region.Aims. To investigate the nature of M1−78 further, we present a detailed spectroscopic study of M1−78 in the optical and near-infrared. Methods. We obtained long-slit, intermediate-resolution, optical spectroscopy with the ISIS spectrograph mounted on the William Herschel Telescope (WHT) at Roque de los Muchachos Observatory (La Palma, Spain). As a complement, we obtained long-slit, intermediate-resolution, near-infrared spectra using LIRIS, the near-infrared imager/spectrographer also installed at the WHT. Results. M1−78 is a high-density nebula with substantial physical differences between its two main morphological zones: a bright arc in the SW and a blob of emission in the NE. Specifically, the blob in the NE has a higher electron temperature (13 400 K) and visual extinction (about 9 mag) than the SW arc. The most important result, however, is the confirmation of a nitrogen enrichment in M1−78. This enrichment is stronger at the location of the NE blob and is correlated with a defficiency in the O abundance and a (dubious) He enrichment. Such an abundance pattern is typical of ejecta nebulae around evolved massive stars such as Wolf-Rayet and Luminous Blue Variable stars. The spatial variations in the physical conditions and chemical abundances and the presence of more than one possible ionizing source indicate, however, that M1−78 is better described as a combination of a compact H ii region + ejecta. This is confirmed by the He i 2.112 µm/Brγ line ratio, which indicates a hot (T eff > ∼ 40 000 K) O star in the SW arc. Finally, we detect H 2 emission that extends over a large (∼30 ) area around the ionized nebula. Analysis of the near-infrared H 2 lines indicates that the excitation mechanism is UV fluorescence.

show abstract

“…Atualmente, a molécula H (assim como outras moléculas) já é incluída em estudos da componente molecular em diversas situações astrofísicas, como nuvens interestelares , nuvens moleculares interestelares , nuvens escuras , gás primordial , Abel 1995, regiões de fotodissociação em geral , Draine & Bertoldi 1996, choques em nuvens interestelares (Hollenbach & McKee 1979e Hollenbach & McKee 1989 e mesmo em NPs (Black 1978;Gussie & Pritchet 1988 Usando como base o modelo de fotoionização de NP de Flower (1969), Black (1978) efetuou um cálculo não acoplado àquele modelo da distribuição da concentração de H 2 , He H 2 + ao longo de uma NP. No modelo de Flower (1969), a presença de grãos não é considerada.…”

Section: I In Nt Tr Ro Od Du Uç çã ãO Ounclassified

A Molécula H2 em Nebulosas Planetárias

Aleman¹

View full text Add to dashboard Cite

show abstract

The Classification of M 1-78

Cited by 6 publications

References 31 publications

Modelling the warm H2 infrared emission of the Helix nebula cometary knots

Modelling the warm H2 infrared emission of the Helix nebula cometary knots

M1–78: a nitrogen-rich Galactic compact H II region beyond the Perseus arm

A Molécula H2 em Nebulosas Planetárias

Contact Info

Product

Resources

About