Helical fields and filamentary molecular clouds -- I

Fiege, Jason D.; Pudritz, Ralph E.

doi:10.1046/j.1365-8711.2000.03066.x

Cited by 289 publications

(353 citation statements)

References 39 publications

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“…Thus, SMM 6 appears to be a thermally supercritical filament susceptible to fragmentation, in agreement with the detected substructure. We note that in the case of a magnetised molecular-cloud filament, M crit line differs by only a factor of order unity from that of an unmagnetised case (Fiege & Pudritz 2000).…”

Section: Deuterated Formaldehydementioning

confidence: 67%

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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Section: Deuterated Formaldehydementioning

confidence: 67%

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

Miettinen

Harju

Haikala

et al. 2012

A&A

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“…Fiege & Pudritz 2000). In contrast, in the non-star-forming, translucent Polaris cloud (where only unbound starless cores are found but no prestellar cores nor protostars), all of the filaments have subcritical masses per unit length (cf.…”

Section: Implications For Our Understanding Of the Core Formation Promentioning

confidence: 99%

Origin of the prestellar core mass function and link to the IMF – Herschel first results

André¹,

Könyves²,

Arzoumanian³

2010

Proc. IAU

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Abstract. We briefly review ground-based (sub)millimeter dust continuum observations of the prestellar core mass function (CMF) and its connection to the stellar initial mass function (IMF). We also summarize the first results obtained on this topic from the Herschel Gould Belt survey, one of the largest key projects with the Herschel Space Observatory. Our early findings with Herschel confirm the existence of a close relationship between the CMF and the IMF. Furthermore, they suggest a scenario according to which the formation of prestellar cores occurs in two main steps: 1) complex networks of long, thin filaments form first, probably as a result of interstellar MHD turbulence; 2) the densest filaments then fragment and develop prestellar cores via gravitational instability.

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“…Similarly, R flat takes on a wide array of values, with most filaments characterized by flattened inner regions extending between 0.02 and 0.08 pc. While the parameters ρ c and R flat provide some useful quantities, the physical conditions that provide stability against gravitational collapse are predominantly represented through the radial decay parameter p. Since Ostriker's seminal paper on self-gravitating, isothermal, equilibrium cylinders (p ≈ 4), multiple analytical cylindrical models including support mechanisms such as logatropic equations of state and magnetic fields have been derived (Fiege & Pudritz 2000). These theoretical models of filament structure predict a range of p values between 1 and 4.…”

Section: The Plummer-profile Parametersmentioning

confidence: 99%

“…In support of this, hydrodynamical simulations predict the existence of high-density filaments that flow into star-forming clusters (Gómez & Vázquez-Semadeni 2014), while analytical models suggest that cylindrical geometries favour gravitational collapse over alternative geometries (Pon, Johnstone & Heitsch 2011). Previous studies of filamentary structure in Aquila, Polaris and IC 5146 using data from the Herschel Space Observatory have yielded results suggestive of a characteristic filament width of ∼0.1 pc (Arzoumanian et al 2011) and a radial fall-off parameter p ∼ 2 (see equation 4) consistent with the presence of helical magnetic fields (Fiege & Pudritz 2000) rather than a static isothermal self-gravitating cylinder (Ostriker 1964). The accurate determination of such quantities depends heavily upon spatial resolution as filaments at a distance of ∼400 pc are barely resolved using the Herschel instruments (Juvela, Malinen & Lunttila 2012).…”

mentioning

confidence: 95%