Physical properties and chemical composition of the cores in the California molecular cloud

Zhang, Guoyin; Xu, Jin-Long; Vasyunin, A. I.; Semenov, D.; Wang, Junjie; Dib, Sami; Liu, Sheng-Yuan; Zhang, Chuan-Peng; Liu, Xiaolan; Wang, Ke; Li, Di; Wu, Zhibo; Yuan, Jinghua; Li, Da-Lei

doi:10.1051/0004-6361/201833622

Cited by 32 publications

(26 citation statements)

References 115 publications

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“…Only one B-type main-sequence star is found in the southeastern part of the California MC and it is associated with relatively intense star formation in a local region around it (Andrews & Wolk 2008). The global star formation efficiency estimated by Zhang et al (2018) for the California MC is only ∼1%, which is half of the typical value (∼2%) in the molecular clouds of the Milky Way (Evans 1991). The California MC is therefore an ideal place to study star formation at early stages.…”

Section: Introductionmentioning

confidence: 79%

Fragmentation of star-forming filaments in the X-shaped nebula of the California molecular cloud

Zhang

André

Wang

2020

A&A

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Context. Dense molecular filaments are central to the star formation process, but the detailed manner in which they fragment into prestellar cores is not well understood yet. Aims. Here, we investigate the fragmentation properties and dynamical state of several star-forming filaments in the X-shaped nebula region of the California molecular cloud in an effort to shed some light on this issue. Methods. We used multiwavelength far-infrared images from Herschel as well as the getsources and getfilaments extraction methods to identify dense cores and filaments in the region and derive their basic properties. We also used a map of 13CO(2−1) emission from the Arizona 10m Submillimeter Telescope (SMT) to constrain the dynamical state of the filaments. Results. We identified ten filaments with aspect ratios of AR > 4 and column density contrasts of C > 0.5, as well as 57 dense cores, including two protostellar cores, 20 robust prestellar cores, 11 candidate prestellar cores, and 24 unbound starless cores. All ten filaments have roughly the same deconvolved full width at half maximum (FWHM), with a median value of 0.12 ± 0.03 pc, which is independent of their column densities ranging from <1021 cm−2 to >1022 cm−2. Two star-forming filaments (# 8 and # 10) stand out since they harbor quasi-periodic chains of dense cores with a typical projected core spacing of ~0.15 pc. These two filaments have thermally supercritical line masses and are not static. Filament 8 exhibits a prominent transverse velocity gradient, suggesting that it is accreting gas from the parent cloud gas reservoir at an estimated rate of ~40 ± 10 M⊙ Myr−1 pc−1. Filament 10 includes two embedded protostars with outflows and it is likely at a somewhat later evolutionary stage than filament 8. In both cases, the observed (projected) core spacing is similar to the filament width and significantly shorter than the canonical separation of ~4 times the filament width predicted by classical cylinder fragmentation theory. It is unlikely that projection effects can explain this discrepancy. We suggest that the continuous accretion of gas onto the two star-forming filaments, as well as the geometrical bending of the filaments, may account for the observed core spacing. Conclusions. Our findings suggest that the characteristic fragmentation lengthscale of molecular filaments is quite sensitive to external perturbations from the parent cloud, such as the gravitational accretion of ambient material.

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Section: Introductionmentioning

confidence: 79%

Fragmentation of star-forming filaments in the X-shaped nebula of the California molecular cloud

Zhang

André

Wang

2020

A&A

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“…Fell-Walker has been used in other SCUBA-2 surveys (e.g. Rumble et al 2015;Eden et al 2017;Johnstone et al 2017;Juvela et al 2018b;Eden et al 2019), as well as in, for example, Zhang et al (2018), using Herschel column density maps. The input values used in the algorithm are presented in Appendix E. The RMS noise values are calculated from the reference regions (Table F.1, Appendix F).…”

Section: Clump Detectionmentioning

confidence: 99%

Characterization of dense Planck clumps observed with Herschel and SCUBA-2

Mannfors

Juvela

Bronfman

et al. 2021

A&A

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Context. Although the basic processes of star formation (SF) are known, more research is needed on SF across multiple scales and environments. The Planck all-sky survey provided a large catalog of Galactic cold clouds and clumps that have been the target of several follow-up surveys. Aims. We aim to characterize a diverse selection of dense, potentially star-forming cores, clumps, and clouds within the Milky Way in terms of their dust emission and SF activity. Methods. We studied 53 fields that have been observed in the JCMT SCUBA-2 continuum survey SCOPE and have been mapped with Herschel. We estimated dust properties by fitting Herschel observations with modified blackbody functions, studied the relationship between dust temperature and dust opacity spectral index β, and estimated column densities. We extracted clumps from the SCUBA-2 850 µm maps with the FellWalker algorithm and examined their masses and sizes. Clumps are associated with young stellar objects found in several catalogs. We estimated the gravitational stability of the clumps with virial analysis. The clumps are categorized as unbound starless, prestellar, or protostellar. Results. We find 529 dense clumps, typically with high column densities from (0.3-4.8)×10 22 cm −2 , with a mean of (1.5±0.04)×10 22 cm −2 , low temperatures (T ∼10 -20 K), and estimated submillimeter β=1.7±0.1. We detect a slight increase in opacity spectral index toward millimeter wavelengths. Masses of the sources range from 0.04 M to 4259 M . Mass, linear size, and temperature are correlated with distance. Furthermore, the estimated gravitational stability is dependent on distance, and more distant clumps appear more virially bound. Finally, we present a catalog of properties of the clumps. Conclusions. Our sources present a large array of SF regions, from high-latitude, nearby diffuse clouds to large SF complexes near the Galactic center. Analysis of these regions will continue with the addition of molecular line data, which will allow us to study the densest regions of the clumps in more detail.

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“…To explain the origin of these, one must characterise the preceding step, the prestellar cores, looking at the corresponding core formation efficiency (CFE, the fraction of cloud mass converted into cores) and core mass function (CMF) (Motte et al 1998, Kiss et al 2006, Alves et al 2007. CFE estimates vary in wide range (at least 5 -35%) between different clouds, probably also depending on the observations used and the chosen extent of the region (Palau et al 2013, Zhang et al 2019. Many studies have commented on the similarity of the IMF and the prestellar CMF after a ∼30% relative shift (efficiency) in masses (e.g.…”

Section: Birth Of Prestellar Coresmentioning

confidence: 99%

Star formation in the solar neighbourhood

Juvela

2018

Proc. IAU

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Star formation started as a cosmic process soon after the big bang and still continues in the Milky Way, although at a decreasing rate. The formation of dense interstellar clouds, their fragmentation and eventual collapse lead to the birth of stars. The nearby clouds provide the highest resolution for the study of this process. The progress is closely following the improvement of the infrared and radio-wavelength facilities that enables us to follow even the earliest stages of the star-formation process inside molecular clouds. On the other hand, modern numerical simulations can take into account most of the relevant physics and often provide a more direct access into the general principles of star formation. The comparison of observations and simulations is therefore essential. In this paper, will discuss star formation in the solar neighbourhood, concentrating on the prestellar phases leading up to the formation of protostars.

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Physical properties and chemical composition of the cores in the California molecular cloud

Cited by 32 publications

References 115 publications

Fragmentation of star-forming filaments in the X-shaped nebula of the California molecular cloud

Fragmentation of star-forming filaments in the X-shaped nebula of the California molecular cloud

Characterization of dense Planck clumps observed with Herschel and SCUBA-2

Star formation in the solar neighbourhood

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