L1642 — A Dust Cloud in a Cometary Globule?

Taylor, Morgan; Taylor, Keith; Vaile, R. A.

doi:10.1017/s1323358000021391

Cited by 7 publications

(8 citation statements)

References 4 publications

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“…This is in good agreement with the direct measurement and we adopt 140 pc for the distance of L1642. Based on previous multiwavelength data (Liljeström & Mattila 1988;Taylor et al 1982;Laureijs et al 1987;Liljeström 1991) L1642 appears as a cool and quiescent cloud. It is associated with a much larger HI cloud (over 4…”

Section: Introductionmentioning

confidence: 90%

“…in the 100 µm IRAS map. Furthermore, HI data shows a velocity gradient along the tail, with increasing velocity towards the northeast (Taylor et al 1982). This suggests that the first PMF component represents the very head of the whole structure, and gas in the head is flowing relative to the rest of the structure, not only towards the south-west but also more towards us.…”

Section: Summary Of Kinematics and Environmental Effectsmentioning

confidence: 96%

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Morphology and kinematics of Lynds 1642

Russeil

Juvela

Lehtinen

et al. 2003

A&A

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Abstract. The high latitude translucent molecular cloud L1642 has been mapped in the J = 1-0 and J = 2-1 transitions of 12 CO, 13 CO and C 18 O using the SEST radio telescope. We have analysed the morphology and velocity structure of the cloud using the Positive Matrix Factorization (PMF) method. The results show that L1642 is composed of a main structure at radial velocity 0.2 km s −1 while the higher velocity components at ∼0.5 and 1.0 km s −1 form an incomplete ring around it, suggesting an expanding shell structure. Fainter emission extends to the north with a still higher velocity of up to 1.6 km s −1 . Such a velocity structure suggests an elongated morphology in the line of sight direction. The physical properties of the cloud have been investigated assuming LTE conditions, but non-LTE radiative transfer models are also constructed for the 13 CO observations. We confirm that L1642 follows an r −1 density distribution in its outer parts while the distribution is considerably flatter in the core. The cloud is close to virial equilibrium. In an Appendix the PMF results are compared with the view obtained through the analysis of channel maps and by the use of Principal Component Analysis (PCA). Both PMF and PCA present the observations as a linear combination of basic spectral shapes that are extracted from the data. Comparison of the methods shows that the PMF method in particular is able to produce a presentation of the complex velocity that is both compact and easily interpreted.

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Section: Introductionmentioning

confidence: 90%

Section: Summary Of Kinematics and Environmental Effectsmentioning

confidence: 96%

Morphology and kinematics of Lynds 1642

Russeil

Juvela

Lehtinen

et al. 2003

A&A

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“…The view of L1642 has changed from a "small, somewhat insignificant cloud" (Taylor et al 1982) to an interesting object in several aspects, as shown by the various studies already mentioned. So far, B-1 and B-2 are the only known stars associated to L1642.…”

Section: Star Formation In L1642mentioning

confidence: 99%

“…The overall kinematics is explained by a cometary structure where the low-velocity gradients on the western side may be a result of a geometry, where on that side of the cloud the gas is flowing mainly in the plane of the sky. Taylor et al (1982) predicted that the shearing flow will enhance the density towards the head of the cometary cloud, increase turbulence in the outer parts, and can lead to the formation of hydrodynamical instabilities.…”

Section: Structure and Evolution Of L1642mentioning

confidence: 99%

Multiwavelength study of the high-latitude cloud L1642: chain of star formation

Malinen

Juvela

Zahorecz

et al. 2014

A&A

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Context. L1642 is one of the two high galactic latitude (|b| > 30 • ) clouds confirmed to have active star formation. Aims. We examine the properties of this cloud, especially the large-scale structure, dust properties, and compact sources at different stages of star formation.Methods. We present high-resolution far-infrared and submillimetre observations with the Herschel and AKARI satellites and millimetre observations with the AzTEC/ASTE telescope, which we combined with archive data from near-and mid-infrared (2MASS, WISE) to millimetre wavelength observations (Planck).Results. The Herschel observations, combined with other data, show a sequence of objects from a cold clump to young stellar objects (YSOs) at different evolutionary stages. Source B-3 (2MASS J04351455-1414468) appears to be a YSO forming inside the L1642 cloud, instead of a foreground brown dwarf, as previously classified. Herschel data reveal striation in the diffuse dust emission around the cloud L1642. The western region shows striation towards the NE and has a steeper column density gradient on its southern side. The densest central region has a bow-shock like structure showing compression from the west and has a filamentary tail extending towards the east. The differences suggest that these may be spatially distinct structures, aligned only in projection. We derive values of the dust emission cross-section per H nucleon of σ e (250 μm) = 0.5−1.5 × 10 −25 cm 2 /H for different regions of the cloud. Modified black-body fits to the spectral energy distribution of Herschel and Planck data give emissivity spectral index β values 1.8-2.0 for the different regions. The compact sources have lower β values and show an anticorrelation between T and β. Conclusions. Markov chain Monte Carlo calculations demonstrate the strong anticorrelation between β and T errors and the importance of millimetre wavelength Planck data in constraining the estimates. L1642 reveals a more complex structure and sequence of star formation than previously known.

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“…Taylor et al (1982) made HI observations of a region adjacent to and including L 1642. They suggested that L 1642 is a result of hydrodynamic instability within a larger cometary cloud.…”

Section: Introductionmentioning

confidence: 99%

ISO far infrared observations of the high latitude cloud L 1642

Lehtinen¹,

Russeil

Juvela³

et al. 2004

A&A

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Abstract.We have performed a large-scale mapping of the high-latitude, moderate extinction dark cloud L 1642 with ISO (Infrared Space Observatory) at 200 µm to study the properties of dust, the virial equilibrium condition of the cloud, and their relation to star formation. The cloud consists of three denser regions which are connected by diffuse material. Only one of the regions, the one most massive and with the greatest optical depth, is related to a temperature mimimum. The pre-main sequence binary stars IRAS 04325−1419 and IRAS 04327−1419, probably born within the cloud, are located close to this temperature mimimum coinciding with the column density maximum. The minimum dust temperature is ∼13.8 K. The ratio 2E kin /|E pot | for the star-forming region is about 1.2, and thus it is close to being gravitationally bound. However, the other regions are not gravitationally bound. On a 1 −10 spatial scale the radial density distributions, derived from far-infared optical depth maps, are similar between the star-forming and non star-forming regions. The differences that distinguish the star-forming core appear to be its higher density and lower dust temperature.

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L1642 — A Dust Cloud in a Cometary Globule?

Cited by 7 publications

References 4 publications

Morphology and kinematics of Lynds 1642

Morphology and kinematics of Lynds 1642

Multiwavelength study of the high-latitude cloud L1642: chain of star formation

ISO far infrared observations of the high latitude cloud L 1642

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