Interferometric Imaging of IRAS 04368+2557 in the L1527 Molecular Cloud Core: A Dynamically Infalling Envelope with Rotation

Ohashi, Nagayoshi; Hayashi, Masahiko; Ho, Paul T. P.; Momose, Munetake

doi:10.1086/303533

Cited by 186 publications

(229 citation statements)

References 41 publications

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“…It is observed in a nearly edge-on configuration (∼90 • viewing angle) (Ohashi et al 1997) and features a large, dense circumstellar envelope (Ladd et al 1991;Chen et al 1995;Motte & André 2001). It also exhibits a prominent bipolar outflow whose lobes are oriented along the east-west direction (Parker et al 1991).…”

Section: L1527mentioning

confidence: 99%

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Toward understanding the formation of multiple systems

Maury¹,

André²,

Hennebelle

et al. 2010

A&A

156

230

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Context. The formation process of binary stars and multiple systems is poorly understood. The multiplicity rate of Class II premain-sequence stars and Class I protostars is well documented and known to be high (∼ 30% to 50% between ∼100 and 4000 AU). However, optical / near-infrared observations of Class I/Class II YSOs barely constrain the pristine properties of multiple systems, since dynamical evolution can quickly alter these properties during the protostellar phase. Aims. Here, we seek to determine the typical outcome of protostellar collapse and to constrain models of binary formation by core fragmentation during collapse, using high-resolution millimeter continuum imaging of very young (Class 0) protostars observed at the beginning of the main accretion phase. Methods. We carried out a pilot high-resolution study of 5 Class 0 objects, including 3 Taurus sources and 2 Perseus sources, using the most extended (A) configuration of the IRAM Plateau de Bure Interferometer (PdBI) at 1.3 mm. Our PdBI observations have a typical HPBW resolution ∼0.3 −0.5 and rms continuum sensitivity ∼0.1−1 mJy/beam, which allow us to probe the multiplicity of Class 0 protostars down to separations a ∼ 50 AU and circumstellar mass ratios q ∼ 0.07. Results. We detected all 5 primary Class 0 sources in the 1.3 mm dust continuum. A single component associated with the primary Class 0 object was detected in the case of the three Taurus sources, while robust evidence of secondary components was found toward the two Perseus sources: L1448-C and NGC1333-IR2A. We show that the secondary 1.3 mm continuum component detected ∼600 AU south-east of L1448-C, at a position angle close to that of the CO(2−1) jet axis traced by our data, is an outflow feature directly associated with the powerful jet driven by L1448-C. The secondary 1.3 mm continuum component detected ∼1900 AU southeast of NGC1333-IR2A may either be a genuine protostellar companion or trace the edge of an outflow cavity. Therefore, our PdBI observations revealed only wide (>1500 AU) protobinary systems and/or outflow-generated features. Conclusions. When combined with previous millimeter interferometric observations of Class 0 protostars, our pilot PdBI study tentatively suggests that the binary fraction in the ∼75−1000 AU range increases from the Class 0 to the Class I stage. It also seems to argue against purely hydrodynamic models of binary star formation. We briefly discuss possible alternative scenarios to reconcile the low multiplicity rate of Class 0 protostars on small scales with the higher binary fraction observed at later (e.g. Class I) evolutionary stages.

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Section: L1527mentioning

confidence: 99%

“…This is a well-known low-mass Class 0 protostar (Barsony et al 1998) driving a powerful, highly collimated outflow (Bachiller et al 1990), which has been imaged at high Jørgensen et al (2007); (c) André et al (1999); (d) Ohashi et al (1997); (e) Bourke et al (2006); (f) Crapsi et al (2004).…”

Section: L1448-cmentioning

confidence: 99%

Toward understanding the formation of multiple systems

Maury¹,

André²,

Hennebelle

et al. 2010

A&A

156

230

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“…Abundant observational data, in several molecular species, is available in the literature for these clouds (Cernicharo & Guélin 1987;Daniel et al 2007;Duvert et al 1986;Fuller et al 1996;Hogerheijde et al 1997;Hogerheijde 2001;Myers et al 1995;Ohashi et al 1997;Takakuwa et al 2000;Brinch et al 2007). Except for TMC1 for which the position corresponds to the cyanopolyyne peak, the selected pointing positions for the other sources correspond to the envelope surrounding the dense cores.…”

Section: Observation Of Absorption Of So 2 Against the Cosmic Backgroundmentioning

confidence: 99%

Collisional excitation of sulfur dioxide in cold molecular clouds

Cernicharo

Spielfiedel

Balança

et al. 2011

A&A

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We present collisional rate coefficients for SO 2 with ortho and para molecular hydrogen for the physical conditions prevailing in dark molecular clouds. Rate coefficients for the first 31 rotational levels of this species (energies up to 55 K) and for temperatures between 5 and 30 K are provided. We have found that these rate coefficients are about ten times more than those previously computed for SO 2 with helium. We calculated the expected emission of the centimeter wavelength lines of SO 2 . We find that the transition connecting the metastable 2 02 level with the 1 11 one is in absorption against the cosmic background for a wide range of densities. The 4 04 −3 13 line is found to be inverted for densities below a few 10 4 cm −3 . We observed the 1 11 −2 02 transition with the 100 m Green Bank Telescope towards some dark clouds. The line is observed, as expected, in absorption and provides an abundance of SO 2 in these objects of a few 10 −10 . The potential use of millimeter lines of SO 2 as tracers of the physical conditions of dark clouds is discussed.

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“…The mass evolution of the disk and envelope can be deduced from millimeter surveys that combine both aperture synthesis and singledish observations (Keene & Masson 1990;Terebey et al 1993;Looney et al 2003;Jørgensen et al 2009;Enoch et al 2011). However, precise determination of stellar masses requires spatially and spectrally resolved molecular line observations of the velocity gradient in the inner regions of embedded YSOs (Sargent & Beckwith 1987;Ohashi et al 1997;Brinch et al 2007;Lommen et al 2008;Jørgensen et al 2009;Takakuwa et al 2012;Yen et al 2013). Here we apply a similar analysis to the synthetic continuum and molecular line data as performed on the observations to test the reliability of the inferred masses.…”

Section: Introductionmentioning

confidence: 99%

Testing protostellar disk formation models with ALMA observations

Harsono

Dishoeck

Bruderer

et al. 2015

A&A

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Context. Recent simulations have explored different ways to form accretion disks around low-mass stars. However, it has been difficult to differentiate between the proposed mechanisms because of a lack of observable predictions from these numerical studies. Aims. We aim to present observables that can differentiate a rotationally supported disk from an infalling rotating envelope toward deeply embedded young stellar objects (M env > M disk ) and infer their masses and sizes. Methods. Two 3D magnetohydrodynamics (MHD) formation simulations are studied with a rotationally supported disk (RSD) forming in one but not the other (where a pseudo-disk is formed instead), together with the 2D semi-analytical model. We determine the dust temperature structure through continuum radiative transfer RADMC3D modeling. A simple temperature-dependent CO abundance structure is adopted and synthetic spectrally resolved submm rotational molecular lines up to J u = 10 are compared with existing data to provide predictions for future ALMA observations. Results. The 3D MHD simulations and 2D semi-analytical model predict similar compact components in continuum if observed at the spatial resolutions of 0.5-1 (70-140 AU) typical of the observations to date. A spatial resolution of ∼14 AU and high dynamic range (>1000) are required in order to differentiate between RSD and pseudo-disk formation scenarios in the continuum. The first moment maps of the molecular lines show a blue-to red-shifted velocity gradient along the major axis of the flattened structure in the case of RSD formation, as expected, whereas it is along the minor axis in the case of a pseudo-disk. The peak position-velocity diagrams indicate that the pseudo-disk shows a flatter velocity profile with radius than does an RSD. On larger scales, the CO isotopolog line profiles within large (>9 ) beams are similar and are narrower than the observed line widths of low-J (2-1 and 3-2) lines, indicating significant turbulence in the large-scale envelopes. However a forming RSD can provide the observed line widths of high-J (6-5, 9-8, and 10-9) lines. Thus, either RSDs are common or a higher level of turbulence (b ∼ 0.8 km s −1 ) is required in the inner envelope compared with the outer part (0.4 km s −1 ). Conclusions. Multiple spatially and spectrally resolved molecular line observations can differentiate between the pseudo-disk and the RSD much better than continuum data. The continuum data give a better estimate of disk masses, whereas the disk sizes can be estimated from the spatially resolved molecular lines observations. The general observable trends are similar between the 2D semi-analytical models and 3D MHD RSD simulations.

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Interferometric Imaging of IRAS 04368+2557 in the L1527 Molecular Cloud Core: A Dynamically Infalling Envelope with Rotation

Cited by 186 publications

References 41 publications

Toward understanding the formation of multiple systems

Toward understanding the formation of multiple systems

Collisional excitation of sulfur dioxide in cold molecular clouds

Testing protostellar disk formation models with ALMA observations

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