Submillimetre continuum images of the NGC 2024 star-forming ridge

Visser, Anja E.; Richer, J. S.; Chandler, Claire J.; Padman, R.

doi:10.1046/j.1365-8711.1998.02092.x

Cited by 47 publications

(62 citation statements)

References 14 publications

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“…L 1157-mm region may thus be indicative of physical differences between the properties of the material toward the embedded source and those of the more extended region. This effect was already observed in other young embedded sources (Visser et al 1998;Johnstone & Bally 1999;Smith et al 2000;Beltrán et al 2002).…”

Section: Spectral Index Mapsupporting

confidence: 73%

L1157: Interaction of the molecular outflow with the Class 0 environment

Beltrán

Gueth

Guilloteau

et al. 2004

A&A

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Abstract. We present high angular resolution interferometric observations [ ] of the dust continuum at 2.7 and 1.3 mm, and of the HC 3 N (J = 12 → 11) and C 18 O (J = 2 → 1) emission around L1157-mm, a Class 0 object that drives a spectacular molecular outflow. The millimeter dust emission is clearly resolved into two components, a flattened compact source of ∼450 × 250 AU at 1.3 mm, and mass ∼0.1 M , plus an extended envelope of ∼3000 AU at 1.3 mm, and mass ∼1.1 M . The millimeter spectral index varies throughout the region, with the lower value found toward the compact protostar, possibly indicating grain growth in the denser regions. A strong interaction between the molecular outflow and the close protostellar environment is taking place and affects the structure of the innermost parts of the envelope. This is shown by the spatial coincidence between the molecular outflow and the dust (1.3 mm continuum) and HC 3 N emission: both tracers show structures associated to the edges of the outflow lobes. Basically, the global picture sketched for the Class 0 object L1157-mm by Gueth et al. (1997) is supported. We find possible evidence of infall, but we do not detect any velocity gradient indicative of a rotating circumstellar disk.

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Section: Spectral Index Mapsupporting

confidence: 73%

L1157: Interaction of the molecular outflow with the Class 0 environment

Beltrán

Gueth

Guilloteau

et al. 2004

A&A

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“…Observational studies have found evidence that β decreases as a result of grain growth at high densities (e.g., Goldsmith et al 1997;Visser et al 1998). More recently, Kwon et al (2009) found that β 1 for their sample of three Class 0 sources, resembling the values we found towards the Class 0 candidates IRAS 05405 and SMM 4.…”

Section: Dust Propertiesmentioning

confidence: 99%

A (sub)millimetre study of dense cores in Orion B9

Miettinen

Harju

Haikala

et al. 2012

A&A

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Context. Studies of dense molecular-cloud cores at (sub)millimetre wavelengths are needed to understand the early stages of star formation. Aims. We aim to further constrain the properties and evolutionary stages of dense cores in Orion B9. The prime objective of this study is to examine the dust emission of the cores near the peak of their spectral energy distributions, and to determine the degrees of CO depletion, deuterium fractionation, and ionisation. Methods. The central part of Orion B9 was mapped at 350 μm with APEX/SABOCA. A sample of nine cores in the region were observed in C 17 O(2−1), H 13 CO + (4−3) (towards 3 sources), DCO + (4−3), N 2 H + (3−2), and N 2 D + (3−2) with APEX/SHFI. These data are used in conjunction with our previous APEX/LABOCA 870-μm dust continuum data. Results. All the LABOCA cores in the region covered by our SABOCA map were detected at 350 μm. The strongest 350 μm emission is seen towards the Class 0 candidate SMM 3. Many of the LABOCA cores show evidence of substructure in the higher-resolution SABOCA image. In particular, we report on the discovery of multiple very low-mass condensations in the prestellar core SMM 6. Based on the 350-to-870 μm flux density ratios, we determine dust temperatures of T dust 7.9−10.8 K, and dust emissivity indices of β ∼ 0.5−1.8. The CO depletion factors are in the range f D ∼ 1.6−10.8. The degree of deuteration in N 2 H + is 0.04−0.99, where the highest value (seen towards the prestellar core SMM 1) is, to our knowledge, the most extreme level of N 2 H + deuteration reported so far. The level of HCO + deuteration is about 1-2%. The fractional ionisation and cosmic-ray ionisation rate of H 2 could be determined only towards two sources with the lower limits of ∼2−6 × 10 −8 and ∼2.6 × 10 −17 −4.8 × 10 −16 s −1 , respectively. We also detected D 2 CO towards two sources. Conclusions. The detected protostellar cores are classified as Class 0 objects, in agreement with our previous SED results. The detection of subcondensations within SMM 6 shows that core fragmentation can already take place during the prestellar phase. The origin of this substructure is likely caused by thermal Jeans fragmentation of the elongated parent core. Varying levels of f D and deuteration among the cores suggest that they are evolving chemically at different rates. A low f D value and the presence of gas-phase D 2 CO in SMM 1 suggest that the core chemistry is affected by the nearby outflow. The very high N 2 H + deuteration in SMM 1 is likely to be remnant of the earlier CO-depleted phase.

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“…Assuming that the dust opacity follows a power law with ( ) / and that the dust emission can be approximated by a blackbody at temperature T d , the dust emission is given by In practice, however, determining the dust temperature is complicated by the fact that the dust opacity power-law coefficient, , is poorly constrained and often varies with location and physical conditions (Goldsmith et al 1997;Visser et al 1998;Hogerheijde & Sandell 2000;Beuther et al 2004). In addition, the 450 and 850 m beam sizes at the JCMT are significantly different, and the 450 m beam is not well approximated by a single Gaussian function ( Hogerheijde & Sandell 2000 Assuming that ¼ 2 (Hildebrand 1983), the central dust temperature for each clump was estimated using the total flux in the convolved 850 and 450 m maps by inverting…”

Section: Clump Temperatures Derived From Submillimeter Colorsmentioning

confidence: 99%

Large Area Mapping at 850 μm. IV. Analysis of the Clump Distribution in the Orion B South Molecular Cloud

Johnstone

Matthews

Mitchell

2006

ApJ

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We present results from a survey of a 1300 arcmin 2 region of the Orion B South molecular cloud, including NGC 2024, NGC 2023, and the Horsehead Nebula ( B33), obtained using the Submillimetre Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope (JCMT). Submillimeter continuum observations at 450 and 850 m are discussed. Using an automated algorithm, 57 discrete emission features (''clumps'') are identified in the 850 m map. The physical conditions within these clumps are investigated under the assumption that the objects are in quasi-hydrostatic equilibrium. The best-fit dust temperature for the clumps is found to be T d ¼ 18 AE 4 K, with the exception of those associated with the few known far-infrared sources residing in NGC 2024. The latter internally heated sources are found to be much warmer. In the region surrounding NGC 2023, the clump dust temperatures agree with clump gas temperatures determined from molecular line excitation measurements of the CO molecule. The bounding pressure on the clumps lies in the range log (k À1 P cm 3 K À1 ) ¼ 6:1 AE 0:3. The cumulative mass distribution is steep at the high-mass end, as is the stellar initial mass function. The distribution flattens significantly at lower masses, with a turnover around 3-10 M .

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Submillimetre continuum images of the NGC 2024 star-forming ridge

Cited by 47 publications

References 14 publications

L1157: Interaction of the molecular outflow with the Class 0 environment

L1157: Interaction of the molecular outflow with the Class 0 environment

A (sub)millimetre study of dense cores in Orion B9

Large Area Mapping at 850 μm. IV. Analysis of the Clump Distribution in the Orion B South Molecular Cloud

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