Detection of the CN Zeeman Effect in Molecular Clouds

Crutcher, R. M.; Troland, T. H.; Lazareff, B.; Paubert, G.; Kazès, I.

doi:10.1086/311952

Cited by 135 publications

(153 citation statements)

References 4 publications

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“…1. The masers in question lie midway between the regions studied by Crutcher et al (1999). We draw the conclusion that the magnetic field is rather nonuniform in this zone and that our assumption of a field of 1 mG is acceptable.…”

Section: The Rôle Of Shocksmentioning

confidence: 66%

“…There are two measurements of the magnetic field in Orion reasonably close to the region of interest. Crutcher et al (1999) have used CN hyperfine splitting to measure a field of magnitude 0.19±0.09 mG and another undetectably weak, in a 23 arcsec beam, measurements referring to two different areas centered about 35 to 40 arcsec from the centre of our region. Norris (1984) gave an estimate of a magnetic field of 3 mG, based on the apparent velocity difference of a presumed Zeeman pair of OH masers at 1665 MHz.…”

Section: The Rôle Of Shocksmentioning

confidence: 99%

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H₂infrared emission and the formation of dense structures in the Orion molecular cloud

Vannier

Lemaire

Field

et al. 2001

A&A

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Abstract.Observations are reported of IR emission of H2 from a region of the Orion molecular cloud (OMC1) between the Becklin-Neugebauer object and IRc2 to the north and the Trapezium stars to the south. Data were obtained using the ESO 3.6 m telescope in the K-band around 2 µm with the ADONIS adaptive optics system. Images of H2 v = 1−0 S(1) show a spatial resolution of ∼0.15 . Detailed investigations of the distribution of sizes of structures in our images have been performed by area-perimeter analysis, Fourier analysis and brightness distribution studies. These demonstrate that structure is not fractal but shows a preferred scales of between 3 10 −3 and 4 10 −3 pc. In an attempt to estimate the density in observed structures, predictions of both shock models and photodissociation region models have been compared with measured emission brightness in the H2 v = 1−0 S(1) line. Magnetic (C-type) shocks with velocities of 30 km s −1 and pre-shock densities of 10 6 cm −3 yield the best representation of our data, notwithstanding significant discrepancies for the brightness ratio between v = 2−1 S(1) and v = 1−0 S(1) lines. Our results show that post-shock densities are several times 10 7 cm −3 . This is sufficiently high that the passage of C-type shocks in Orion yields gravitational instability which may in turn trigger star formation in the post-shock gas.

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Section: The Rôle Of Shocksmentioning

confidence: 66%

Section: The Rôle Of Shocksmentioning

confidence: 99%

H₂infrared emission and the formation of dense structures in the Orion molecular cloud

Vannier

Lemaire

Field

et al. 2001

A&A

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“…Few radicals are known to be suitable and while Crutcher et al (1996bCrutcher et al ( , 1999 explored the use of CN, we explored the potential of SO and CCS. Despite using the most sensitive telescope available, a dedicated receiver, and spending many hundreds of hours of observation/integration time, we failed to detect any field via the SO and CCS transitions.…”

Section: Discussionmentioning

confidence: 99%

Zeeman line splitting measurements sampling dense gas in dark cloud and star-forming cores

Uchida

Fiebig

Güsten

2001

A&A

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Abstract. We present measurements of Zeeman splitting in SO JN = 12 − 11 line emission/absorption arising from dense thermal gas (>10 6 cm −3 ) associated with ten compact H II and star-forming regions. No line-of-sight magnetic field, above an average 1σ limit of 0.57 mG, is detected toward any of these sources. The W3(OH) region, found in a previous study to have a line-of-sight field of 3 mG in its dense gas, is thus unique in this respect. The implication of this study is that the magnetic fields in dense clouds are supercritical in the sense that they are not capable of supporting their host clouds against gravitational collapse. The relatively low average field limit is consistent with those theories predicting the quick onset of and short timescales for ambipolar diffusion. Also presented are (1) Zeeman splitting measurements of the CCS JN = 10 − 01 line probing the 10 4−5 cm −3 gas towards three positions in the Taurus star forming region, giving a 1σ average upper limit of 66 µG, and (2) measurements of Zeeman splitting in the OH 2 Π 3/2 J = 7/2 F = 3 + − 3 − hyperfine line toward the compact H II regions DR-21 and G10.62.

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“…Since the region may be permeated by magnetic fields (Norris 1984;Crutcher et al 1999) and the gas is at least weakly ionized, shock models include not only J-type (Hollenbach & McKee 1989;Lim et al 2002) and but also continuous-type (C-type) shock waves. The latter have been investigated by Draine et al (1983), Pineau des Forêts et al (1988), Smith & Brand (1990), Kaufman & Neufeld (1996a,b), Timmerman (1998), Wilgenbus et al (2000), whose results were used in V2001, and most recently by Le Bourlot et al (2002).…”

Section: The Influence Of Shocksmentioning

confidence: 99%

H₂excitation imaging of the Orion Molecular Cloud

Kristensen

Gustafsson

Field

et al. 2003

A&A

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Abstract.Observations are reported of IR emission in H 2 , around 2 µm in the K-band, obtained with the ESO 3.6 m telescope using the ADONIS adaptive optics system. Data cover a region of the Orion Molecular Cloud north of the Trapezium stars and SW of the Becklin-Neugebauer object. Excellent seeing yielded diffraction limited images in the v = 2−1 S(1) line at 2.247 µm. Excitation temperature images were created by combining these data with similar data for H 2 emission in the v = 1−0 S(1) line reported earlier ). Shock models are used to estimate densities in emitting clumps of material. In local zones with high excitation temperatures, post-shock densities are found to be as high as several times 10 8 cm −3 , an order of magnitude denser than our previous estimates. We propose that the nature of these zones is dictated by the combined activity of shocks, which create dense structures, and the powerful radiation field of θ 1 C Ori which photoevaporates the boundaries of these structures.

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Detection of the CN Zeeman Effect in Molecular Clouds

Cited by 135 publications

References 4 publications

H₂infrared emission and the formation of dense structures in the Orion molecular cloud

H₂infrared emission and the formation of dense structures in the Orion molecular cloud

Zeeman line splitting measurements sampling dense gas in dark cloud and star-forming cores

H₂excitation imaging of the Orion Molecular Cloud

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Detection of the CN Zeeman Effect in Molecular Clouds

Cited by 135 publications

References 4 publications

H2infrared emission and the formation of dense structures in the Orion molecular cloud

H2infrared emission and the formation of dense structures in the Orion molecular cloud

Zeeman line splitting measurements sampling dense gas in dark cloud and star-forming cores

H2excitation imaging of the Orion Molecular Cloud

Contact Info

Product

Resources

About

H₂infrared emission and the formation of dense structures in the Orion molecular cloud

H₂infrared emission and the formation of dense structures in the Orion molecular cloud

H₂excitation imaging of the Orion Molecular Cloud