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Dynamics of cluster-forming hub-filament systems: The case of the high-mass star-forming complex Monoceros R2.

ABSTRACT: Context:High-mass stars and star clusters commonly form within hub-filament systems. Monoceros R2 (hereafter Mon R2), at a distance of 830 pc, harbors one of the closest such systems, making it an excellent target for case studies. Aims:We investigate the morphology, stability and dynamical properties of the Mon R2 hub-filament system. Methods:We employ observations of the 13CO and C18O 1?0 and 2?1 lines obtained with the IRAM-30m telescope. We also use H2 column density maps derived from Herschel dust emission observations. Results:We identified the filamentary network in Mon R2 with the DisPerSE algorithm and characterized the individual filaments as either main (converging into the hub) or secondary (converging to a main filament) filaments. The main filaments have line masses of 30-100 M ? pc-1 and show signs of fragmentation, while the secondary filaments have line masses of 12-60 M ? pc-1 and show fragmentation only sporadically. In the context of Ostriker's hydrostatic filament model, the main filaments are thermally supercritical. If non-thermal motions are included, most of them are trans-critical. Most of the secondary filaments are roughly transcritical regardless of whether non-thermal motions are included or not. From the morphology and kinematics of the main filaments, we estimate a mass accretion rate of 10-4-10-3 M ? yr-1 into the central hub. The secondary filaments accrete into the main filaments with a rate of 0.1-0.4×10-4 M ? yr-1. The main filaments extend into the central hub. Their velocity gradients increase towards the hub, suggesting acceleration of the gas.We estimate that with the observed infall velocity, the mass-doubling time of the hub is ~ 2:5 Myr, ten times larger than the free-fall time, suggesting a dynamically old region. These timescales are comparable with the chemical age of the Hii region. Inside the hub, the main filaments show a ring- or a spiral-like morphology that exhibits rotation and infall motions. One possible explanation for the morphology is that gas is falling into the central cluster following a spiral-like pattern.

SUBMITTER: Trevino-Morales SP

PROVIDER: S-EPMC6823053 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature

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Dynamics of cluster-forming hub-filament systems: The case of the high-mass star-forming complex Monoceros R2.

Treviño-Morales S P SP Fuente A A Sánchez-Monge Á Á Kainulainen J J Didelon P P Suri S S Schneider N N Ballesteros-Paredes J J Lee Y-N YN Hennebelle P P Pilleri P P González-García M M Kramer C C García-Burillo S S Luna A A Goicoechea J R JR Tremblin P P Geen S S

Astronomy and astrophysics 20190912

<h4>Context</h4>High-mass stars and star clusters commonly form within hub-filament systems. Monoceros R2 (hereafter Mon R2), at a distance of 830 pc, harbors one of the closest such systems, making it an excellent target for case studies.<h4>Aims</h4>We investigate the morphology, stability and dynamical properties of the Mon R2 hub-filament system.<h4>Methods</h4>We employ observations of the <sup>13</sup>CO and C<sup>18</sup>O 1→0 and 2→1 lines obtained with the IRAM-30m telescope. We also us ...[more]

PMID: 31673163

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Project description:Cytidine triphosphate (CTP) is essential for DNA, RNA and phospholipid biosynthesis. De novo synthesis is catalyzed by CTP synthases (CTPS). Arabidopsis encodes five CTPS isoforms that unanimously share conserved motifs found across kingdoms, suggesting all five are functional enzymes. Whereas CTPS1-4 are expressed throughout Arabidopsis tissues, CTPS5 reveals exclusive expression in developing embryos. CTPS activity and substrates affinities were determined for a representative plant enzyme on purified recombinant CTPS3 protein. As demonstrated in model organisms such as yeast, fruit fly and mammals, CTPS show the capacity to assemble into large filaments called cytoophidia. Transient expression of N- and C-terminal YFP-CTPS fusion proteins in Nicotiana benthamiana allowed to monitor such filament formation. Interestingly, CTPS1 and 2 always appeared as soluble proteins, whereas filaments were observed for CTPS3, 4 and 5 independent of the YFP-tag location. However, when similar constructs were expressed in Saccharomyces cerevisiae, no filaments were observed, pointing to a requirement for organism-specific factors in vivo. Indications for filament assembly were also obtained in vitro when recombinant CTPS3 protein was incubated in the presence of CTP. T-DNA-insertion mutants in four CTPS loci revealed no apparent phenotypical alteration. In contrast, CTPS2 T-DNA-insertion mutants did not produce homozygous progenies. An initial characterization of the CTPS protein family members from Arabidopsis is presented. We provide evidence for their involvement in nucleotide de novo synthesis and show that only three of the five CTPS isoforms were able to form filamentous structures in the transient tobacco expression system. This represents a striking difference from previous observations in prokaryotes, yeast, Drosophila and mammalian cells. This finding will be highly valuable to further understand the role of filament formation to regulate CTPS activity.

Dataset Information

Dynamics of cluster-forming hub-filament systems: The case of the high-mass star-forming complex Monoceros R2.

Publications

Dynamics of cluster-forming hub-filament systems: The case of the high-mass star-forming complex Monoceros R2.

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