Main Filament Research Articles

Transient Evolution of Argon Radio Frequency Atmospheric Pressure Discharge After the Very First Breakdown

The very first breakdown in argon radio frequency (RF) atmospheric pressure discharge was realized by pulse modulation with a sufficiently long off-time. The afterward nonsteady temporal stage was monitored with voltage/current probes and a fast camera. Experimental results show that conventionally observed uniform RF atmospheric pressure discharge glows at steady phrase stem from the initial local weak glow through the intermediate stages of filamentation, splitting, branching, expansion, decay, and homogenization. Such a process should also possibly occur after the breakdown of a continuous wave RF atmospheric pressure discharge. During the filamentary stage of the discharge, unusual parallel branching is originated from centers of axial main filaments driven with symmetrical parallel electrodes. Physical mechanisms underlying the transient process are discussed.

Mechanical responses of the mechanosensitive unstructured domains in cardiac titin.

Titin is one of the three main filaments in cardiac sarcomere. Besides a chain of Ig domains, cardiac titin also contains a proline (P), glutamate (E), valine (V), lysine (K) (PEVK) domain and a cardiac-specific N2B domain, both are largely unstructured. While they are believed to be involved in the elastic (PEVK and N2B) and the trophic (N2B) functions of the heart, their mechanical responses in physiological level of forces remains poorly understood. In order to gain understanding on their mechanical responses, we used magnetic tweezers to investigate their force responses from 1 to 30pN. We confirmed that in vitro the PEVK domain is intrinsically disordered within the force range. Surprisingly, we discovered a mechanosensitive folded element in the disordered region of N2B, ∼84 amino acids in length, which has a large folding energy of approximately -10 kB T. Based on the force responses of PEVK and N2B domains, as well as an approximated force-dependent unfolding and refolding rates of titin Ig domains, we show that the tension in cardiac titin fluctuates within 5pN during cardiac contraction and extension cycle using Gillespie simulation algorithm. Exceptionally, the simulation shows that deletion of N2B domain results in 10-fold increase in peak force. Our results highlight a critical role that N2B may potentially play in regulating tension on cardiac titin. The study provides new insights into the tension regulatory role of unstructured domains in the elastic function of the heart, which has broad implication in diastolic dysfunction and cardiac trophic mechanisms. In addition, the method can be applied to probing other unstructured mechanosensitive proteins/domains.

Correlation of gas dynamics and dust in the evolved filament G82.65-02.00

Context. The combination of line and continuum observations can provide vital insight into the formation and fragmentation of filaments and the initial conditions for star formation. We have carried out line observations to map the kinematics of an evolved, actively star forming filament G82.65-2.00. The filament was first identified from the Planck data as a region of particularly cold dust emission and was mapped at 100–500 μm as a part of the Herschel key program Galactic Cold Cores. The Herschel observations cover the central part of the filament, corresponding to a filament length of ~ 12 pc at the assumed distance of 620 pc. Aims. CO observations show that the filament has an intriguing velocity field with several velocity components around the filament. In this paper, we study the velocity structure in detail, to quantify possible mass accretion rate onto the filament, and study the masses of the cold cores located in the filament. Methods. We have carried out line observations of several molecules, including CO isotopologues, HCO+, HCN, and CS with the Osaka 1.85 m telescope and the Nobeyama 45 m telescope. The spectral line data are used to derive velocity and column density information. Results. The observations reveal several velocity components in the field, with strongest line emission concentrated to velocity range ~[3,5] km s-1. The column density of molecular hydrogen along the filament varies from 1.0 to 2.3 × 1022cm2. We have examined six cold clumps from the central part of the filament. The clumps have masses in the range 10−20M⊙ (~ 70 M⊙ in total) and are close to or above the virial mass. Furthermore, the main filament is heavily fragmented and most of the substructures have a mass lower than or close to the virial mass, suggesting that the filament is dispersing as a whole. Position-velocity maps of 12CO and 13CO lines indicate that at least one of the striations is kinematically connected to two of the clumps, potentially indicating mass accretion from the striation onto the main filament. We tentatively estimate the accretion rate to be Ṁ = 2.23 × 10-6M⊙/ yr. Conclusions. Our line observations have revealed two or possibly three velocity components connected to the filament G82.65-2.00 and putative signs of mass accretion onto the filament. The line observations combined with Herschel and WISE maps suggest a possible collision between two cloud components.

Galaxy evolution in merging clusters: The passive core of the “Train Wreck” cluster of galaxies, A 520

The mergers of galaxy clusters are the most energetic events in the universe after the Big Bang. With the increased availability of multi-object spectroscopy and X-ray data an ever increasing fraction of local clusters are recognised as exhibiting signs of recent or past merging events on various scales. Our goal is to probe how these mergers affect the evolution and content of their member galaxies. We specifically aim to answer the following questions: Is the quenching of star formation in merging clusters enhanced when compared with relaxed clusters? Is the quenching preceded by a (short lived) burst of star formation? We obtained optical spectroscopy of >400 galaxies in the field of the merging cluster Abell 520. We combine these observations with archival data to get a comprehensive picture of the state of star formation in the members of this merging cluster. Finally, we compare these observations with a control sample of 10 non-merging clusters at the same redshift from The Arizona Cluster Redshift Survey (ACReS). We split the member galaxies in passive, star forming or recently quenched depending on their spectra. The core of the merger shows a decreased fraction of star forming galaxies compared to clusters in the non-merging sample. This region, dominated by passive galaxies, is extended along the axis of the merger. We find evidence of rapid quenching of the galaxies during the core passage with no signs of a star burst on the time scales of the merger (~0.4Gyr). Additionally, we report the tentative discovery of an infalling group along the main filament feeding the merger, currently at ~2.5 Mpc from the merger centre. This group contains a high fraction of star forming galaxies as well as ~2/3 of all the recently quenched galaxies in our survey.

Expression of vimentin and glial fibrillary acidic protein in central nervous system development of rats.

To investigate the distribution and contents of vimentin (Vim) and glial fibrillary acidic protein (GFAP) immunoreactivities in the central nervous system (CNS) of normal newborn, adult and aged rats. In this study, thirty healthy and normal Sprague-Dawley rats were simply classified into three groups: Newborn (7 days aged), adult (5 months aged) and aged (24 months aged) rats. Brains and spinal cord were dissected and cut into frozen sections. The expression of Vim and GFAP in CNS were detected by confocal immunofluorescence. In each group, Vim was expressed in all the regions of CNS including the hippocampal, cerebral cortex, the third ventricle and spinal cord, and the expression was highest in neuron-like cell of newborn rats, while Vim was mainly expressed in cell bodies in adult and aged rats. GFAP was expressed in all the regions of CNS including the hippocampal, cerebral cortex, the third ventricle and spinal cord, and the expression was in astrocytes of aged rats. In the third ventricle, Vim was detected in all groups, and only observed in neuron-like cells of newborn. Meanwhile, the GFAP expression showed no significant differences between adult and aged rats in this region. The co-localization of Vim and GFAP were mainly observed in hippocampus and cerebral cortex of newborn, but this co-localization was found in the third ventricle of the rats in all groups. Our data demonstrate for the first time that the expression of Vim and GFAP in the rat's CNS during development. This data may provide a foundation for the further mechanistic studies of these two main intermediate filaments during development of CNS.

Westiellopsis ramosa sp. nov., intensely branched species of Westiellopsis (cyanobacteria) from a freshwater habitat of Jabalpur, Madhya Pradesh, India

An axenic culture of a cyanobacterium (strain HPS) was raised from a field specimen of greenish planktonic floccose mass from a local lake, Ganga Sagar. Intense morphological examination and comparative morphological assessment with the genera Fischerella and Hapalosiphon and all the known strains of the genus Westiellopsis indicated that the strain HPS differed in morphology with the closely related strains in trichome arrangement, size of vegetative cells, heterocytes, monocytes, and number of rows of main filaments. There were also differences in the habitat preference, being aquatic rather than terrestrial or subaerial. Intense ecological characterization of the habitat was performed through measurements of important physicochemical characteristics. 16S rRNA gene-based identification and phylogenetic placement indicated conclusively that the strain HPS was different from the most closely related strain Westiellopsis prolifica SAG 16.93. Phylogenetic inferences drawn in between all the branched heterocytous forms and subsequent 16S-23S ITS analyses and folding of the secondary structures revealed an entirely new form that is unknown till now. Subsequent nifD and rbcL gene-based phylogenetic assessments indicated that strain HPS is phylogenetically different from all the other previously known species of true branching cyanobacteria, along with also pointing toward the huge database inconsistencies in case of true branched cyanobacteria. Assessment of morphological and ecological differences along with comprehensive phylogenetic evaluation indicated that the strain HPS is a new species of the genus Westiellopsis and the name being proposed is Westiellopsis ramosa sp. nov.

CO(J = 1–0) Observations of a Filamentary Molecular Cloud in the Galactic Region Centered at l = 150°, b = 3.°5

Abstract We present large-field (4.25 × 3.75 deg2) mapping observations toward the Galactic region centered at in the J = 1–0 emission line of CO isotopologues (12CO, 13CO, and C18O), using the 13.7 m millimeter-wavelength telescope of the Purple Mountain Observatory. Based on the 13CO observations, we reveal a filamentary cloud in the Local Arm at a velocity range of −0.5 to 6.5 km s−1. This molecular cloud contains 1 main filament and 11 sub-filaments, showing the so-called “ridge-nest” structure. The main filament and three sub-filaments are also detected in the C18O line. The velocity structures of most identified filaments display continuous distribution with slight velocity gradients. The measured median excitation temperature, line width, length, width, and linear mass of the filaments are ∼9.28 K, 0.85 km s−1, 7.30 pc, 0.79 pc, and 17.92 pc−1, respectively, assuming a distance of 400 pc. We find that the four filaments detected in the C18O line are thermally supercritical, and two of them are in the virialized state, and thus tend to be gravitationally bound. We identify in total 146 13CO clumps in the cloud, about 77% of the clumps are distributed along the filaments. About 56% of the virialized clumps are found to be associated with the supercritical filaments. Three young stellar object candidates are also identified in the supercritical filaments, based on the complementary infrared data. These results indicate that the supercritical filaments, especially the virialized filaments, may contain star-forming activities.

Filamentary flow and magnetic geometry in evolving cluster-forming molecular cloud clumps

We present an analysis of the relationship between the orientation of magnetic fields and filaments that form in 3D magnetohydrodynamic simulations of cluster-forming, turbulent molecular cloud clumps. We examine simulated cloud clumps with size scales of L ~ 2-4 pc and densities of n ~ 400-1000 cm^-3 with Alfven Mach numbers near unity. We simulated two cloud clumps of different masses, one in virial equilibrium, the other strongly gravitationally bound, but with the same initial turbulent velocity field and similar mass-to-flux ratio. We apply various techniques to analyze the filamentary and magnetic structure of the resulting cloud, including the DisPerSE filament-finding algorithm in 3D. The largest structure that forms is a 1-2 parsec-long filament, with smaller connecting sub-filaments. We find that our simulated clouds, wherein magnetic forces and turbulence are comparable, coherent orientation of the magnetic field depends on the virial parameter. Subvirial clumps undergo strong gravitational collapse and magnetic field lines are dragged with the accretion flow. We see evidence of filament-aligned flow and accretion flow onto the filament in the subvirial cloud. Magnetic fields oriented more parallel in the subvirial cloud and more perpendicular in the denser, marginally bound cloud. Radiative feedback from a 16 Msun star forming in a cluster in one of our simulations ultimately results in the destruction of the main filament, the formation of an HII region, and the sweeping up of magnetic fields within an expanding shell at the edges of the HII region.

The segregation of starless and protostellar clumps in the Hi-GALℓ= 224° region

Stars form in dense, dusty structures, which are embedded in larger clumps of molecular clouds often showing a clear filamentary structure on large scales (> 1pc). One of the best-studied regions in the Hi-GAL survey can be observed toward the l=224deg field. Here, a filamentary region has been studied and it has been found that protostellar clumps are mostly located along the main filament, whereas starless clumps are detected off this filament and are instead found on secondary, less prominent filaments. We want to investigate this segregation effect and how it may affect the clumps properties. We mapped the 12CO(1-0) line and its main three isotopologues toward the two most prominent filaments observed toward the l=224deg field using the Mopra radio telescope, in order to set observational constraints on the dynamics of these structures and the associated starless and protostellar clumps. Compared to the starless clumps, the protostellar clumps are more luminous, more turbulent and lie in regions where the filamentary ambient gas shows larger linewidths. We see evidence of gas flowing along the main filament, but we do not find any signs of accretion flow from the filament onto the Hi-GAL clumps. We analyze the radial column density profile of the filaments and their gravitational stability. The more massive and highly fragmented main filament appears to be thermally supercritical and gravitationally bound, assuming that all of the non-thermal motion is contributing thermal-like support, suggesting a later stage of evolution compared to the secondary filament. The status and evolutionary phase of the Hi-GAL clumps would then appear to correlate with that of the host filament.

Characterizing filaments in regions of high-mass star formation: High-resolution submilimeter imaging of the massive star-forming complex NGC 6334 with ArTéMiS

Herschel observations of nearby molecular clouds suggest that interstellar filaments and prestellar cores represent two fundamental steps in the star formation process. The observations support a picture of low-mass star formation according to which ~ 0.1 pc-wide filaments form first in the cold interstellar medium, probably as a result of large-scale compression of interstellar matter by supersonic turbulent flows, and then prestellar cores arise from gravitational fragmentation of the densest filaments. Whether this scenario also applies to regions of high-mass star formation is an open question, in part because Herschel data cannot resolve the inner width of filaments in the nearest regions of massive star formation. We used the bolometer camera ArTeMiS on the APEX telescope to map the central part of the NGC6334 complex at a factor of > 3 higher resolution than Herschel at 350 microns. Combining ArTeMiS data with Herschel data allowed us to study the structure of the main filament of the complex with a resolution of 8" or < 0.07 pc at d ~ 1.7 kpc. Our study confirms that this filament is a very dense, massive linear structure with a line mass ranging from ~ 500 Msun/pc to ~ 2000 Msun/pc over nearly 10 pc. It also demonstrates that its inner width remains as narrow as W ~ 0.15 +- 0.05 pc all along the filament length, within a factor of < 2 of the characteristic 0.1 pc value found with Herschel for lower-mass filaments in the Gould Belt. While it is not completely clear whether the NGC 6334 filament will form massive stars or not in the future, it is two to three orders of magnitude denser than the majority of filaments observed in Gould Belt clouds, and yet has a very similar inner width. This points to a common physical mechanism for setting the filament width and suggests that some important structural properties of nearby clouds also hold in high-mass star forming regions.

Filamentary structure and magnetic field orientation in Musca

Herschel has shown that filamentary structures are ubiquitous in star-forming regions, in particular in nearby molecular clouds associated with Gould's Belt. High dynamic range far-infrared imaging of the Musca cloud with SPIRE and PACS reveals at least two types of filamentary structures: (1) the main ~10-pc scale high column-density linear filament; and (2) low column-density striations in close proximity to the main filament. In addition, we find features with intermediate column densities (hair-like strands) that appear physically connected to the main filament. We present an analysis of this filamentary network traced by Herschel and explore its connection with the local magnetic field. We find that both the faint dust emission striations and the plane-of-the-sky (POS) magnetic field are locally oriented close to perpendicular to the high-density main filament (position angle ~25-35°). The low-density striations and strands are oriented parallel to the POS magnetic field lines, which are derived previously from optical polarization measurements of background stars and more recently from Planck observations of dust polarized emission. The position angles are 97 ± 25°, 105 ± 7°, and 105 ± 5°. From these observations, we propose a scenario in which local interstellar material in this cloud has condensed into a gravitationally-unstable filament (with supercritical mass per unit length) that is accreting background matter along field lines through the striations. We also compare the filamentary structure in Musca with what is seen in similar Herschel observations of the Taurus B211/3 filament system and find that there is significantly less substructure in the Musca main filament than in the B211/3 filament. We suggest that the Musca cloud may represent an earlier evolutionary stage in which the main filament has not yet accreted sufficient mass and energy to develop a multiple system of intertwined filamentary components. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

Apicomplexans pulling the strings: manipulation of the host cell cytoskeleton dynamics.

Invasive stages of apicomplexan parasites require a host cell to survive, proliferate and advance to the next life cycle stage. Once invasion is achieved, apicomplexans interact closely with the host cell cytoskeleton, but in many cases the different species have evolved distinct mechanisms and pathways to modulate the structural organization of cytoskeletal filaments. The host cell cytoskeleton is a complex network, largely, but not exclusively, composed of microtubules, actin microfilaments and intermediate filaments, all of which are modulated by associated proteins, and it is involved in diverse functions including maintenance of cell morphology and mechanical support, migration, signal transduction, nutrient uptake, membrane and organelle trafficking and cell division. The ability of apicomplexans to modulate the cytoskeleton to their own advantage is clearly beneficial. We here review different aspects of the interactions of apicomplexans with the three main cytoskeletal filament types, provide information on the currently known parasite effector proteins and respective host cell targets involved, and how these interactions modulate the host cell physiology. Some of these findings could provide novel targets that could be exploited for the development of preventive and/or therapeutic strategies.

Asymmetric Distribution of GFAP in Glioma Multipotent Cells.

Asymmetric division (AD) is a fundamental mechanism whereby unequal inheritance of various cellular compounds during mitosis generates unequal fate in the two daughter cells. Unequal repartitions of transcription factors, receptors as well as mRNA have been abundantly described in AD. In contrast, the involvement of intermediate filaments in this process is still largely unknown. AD occurs in stem cells during development but was also recently observed in cancer stem cells. Here, we demonstrate the asymmetric distribution of the main astrocytic intermediate filament, namely the glial fibrillary acid protein (GFAP), in mitotic glioma multipotent cells isolated from glioblastoma (GBM), the most frequent type of brain tumor. Unequal mitotic repartition of GFAP was also observed in mice non-tumoral neural stem cells indicating that this process occurs across species and is not restricted to cancerous cells. Immunofluorescence and videomicroscopy were used to capture these rare and transient events. Considering the role of intermediate filaments in cytoplasm organization and cell signaling, we propose that asymmetric distribution of GFAP could possibly participate in the regulation of normal and cancerous neural stem cell fate.

Filament fragmentation in high-mass star formation

Aims: We resolve the length-scales for filament formation and fragmentation (res. <=0.1pc), in particular the Jeans length and cylinder fragmentation scale. Methods: We observed the prototypical high-mass star-forming filament IRDC18223 with the Plateau de Bure Interferometer (PdBI) in the 3.2mm continuum and N2H+(1-0) line emission in a ten field mosaic at a spatial resolution of ~4'' (~14000AU). Results: The dust continuum emission resolves the filament into a chain of at least 12 relatively regularly spaced cores. The mean separation between cores is ~0.40(+-0.18)pc. While this is approximately consistent with the fragmentation of an infinite, isothermal, gravitationally bound gas cylinder, a high mass-to-length ratio of M/l~1000M_sun/pc requires additional turbulent and/or magnetic support against radial collapse of the filament. The N2H+(1-0) data reveal a velocity gradient perpendicular to the main filament. Although rotation of the filament cannot be excluded, the data are also consistent with the main filament being comprised of several velocity-coherent sub-filaments. Furthermore, this velocity gradient perpendicular to the filament resembles recent results toward Serpens south that are interpreted as signatures of filament formation within magnetized and turbulent sheet-like structures. Lower-density gas tracers ([CI] and C18O) reveal a similar red/blueshifted velocity structure on scales around 60'' east and west of the IRDC18223 filament. This may tentatively be interpreted as a signature of the large-scale cloud and the smaller-scale filament being kinematically coupled. We do not identify a velocity gradient along the axis of the filament. This may either be due to no significant gas flows along the filamentary axis, but it may partly also be caused by a low inclination angle of the filament with respect to the plane of the sky that could minimize such signature.

First record ofNeosiphonia echinata(Rhodomelaceae, Rhodophyta) in the South Pacific: an introduced species in Southeast Asia

AbstractNeosiphonia echinata,a well-known western Atlantic species, is here reported for the first time from Indonesia and this extends its distribution into Southeast Asia.Neosiphonia echinatawas collected from Sulawesi, Indonesia as an epiphyte onKappaphycus alvareziiand growing on ropes in a culture farm. We also collected this species from Florida, USA, and then compared their morphology and molecular data.Neosiphonia echinatais identified by having erect main filaments arising from prostrate filaments, numerous rhizoids cutting off from the proximal end of pericentral cells by a cross wall, four pericentral cells throughout the thallus, ecorticate axes, very long and abundant trichoblasts more than twice forked, abundant adventitious laterals, procarps with four-celled carpogonial branches, and a spiral arrangement of tetrasporangia. Our phylogenetic analyses ofrbcL andcox1 indicate thatN. echinatafound in Indonesia was very closely related to material from the Western Atlantic Ocean.Neosiphonia echinatamay be added as an introduced species to the Indonesian marine flora. The shipping routes western Atlantic-Mediterranean-Indonesia and western Atlantic-Pacific Ocean-Indonesia might be considered as possible pathways of introduction as a consequence of ballast water and hull fouling.

Probing the magnetic field structure in the filamentary cloud IC5146

AbstractIC5146 is one of the filamentary clouds observed in Herschel Gould Belt Survey. Here we present our polarization observations toward IC5146 taken with AIMPOL, TRIPOL and Mimir. Our results reveal that the large scale structure of magnetic field is well perpendicular to the main filament, but is likely parallel to the sub-filaments, which are structure extended out from the main filaments. We have also conducted CO observations to reveal the gas kinematics along the filaments or magnetic field; this result suggests the gas is possibly confined by magnetic field in most of the region until reaching supercritical. Based on our results, we suggests that at least four types of filaments can be found in IC5146, behaving different physical properties and consistent with different formation mechanisms. Our conclusions reveal that filaments are a combination of a variety types of objects.

Self-similar fragmentation regulated by magnetic fields in a region forming massive stars.

Most molecular clouds are filamentary or elongated. For those forming low-mass stars (<8 solar masses), the competition between self-gravity and turbulent pressure along the dynamically dominant intercloud magnetic field (10 to 100 parsecs) shapes the clouds to be elongated either perpendicularly or parallel to the fields. A recent study also suggested that on the scales of 0.1 to 0.01 parsecs, such fields are dynamically important within cloud cores forming massive stars (>8 solar masses). But whether the core field morphologies are inherited from the intercloud medium or governed by cloud turbulence is unknown, as is the effect of magnetic fields on cloud fragmentation at scales of 10 to 0.1 parsecs. Here we report magnetic-field maps inferred from polarimetric observations of NGC 6334, a region forming massive stars, on the 100 to 0.01 parsec scale. NGC 6334 hosts young star-forming sites where fields are not severely affected by stellar feedback, and their directions do not change much over the entire scale range. This means that the fields are dynamically important. The ordered fields lead to a self-similar gas fragmentation: at all scales, there exist elongated gas structures nearly perpendicular to the fields. Many gas elongations have density peaks near the ends, which symmetrically pinch the fields. The field strength is proportional to the 0.4th power of the density, which is an indication of anisotropic gas contractions along the field. We conclude that magnetic fields have a crucial role in the fragmentation of NGC 6334.

A SPICE Compact Model for Unipolar RRAM Reset Process Analysis

A physically based circuit model is proposed for SPICE simulation of thermally assisted reset transitions in resistive switching devices. The model allows the simulation of conductive filaments with complex structures, such as a main filament with several subfilaments attached forming a tree structure, or several filaments interlaced between them. The model has been validated by comparing with experimental data and the simulations obtained with a previously published simulation tool. A study of the influence of different subfilaments configurations on the variability of resistive random access memory I-V reset curves is also presented.

MUSE discovers perpendicular arcs in the inner filament of Centaurus A

Evidence of AGN interaction with the IGM is observed in some galaxies and many cool core clusters. Radio jets are suspected to dig large cavities into the surrounding gas. In most cases, very large optical filaments are seen around the central galaxy. The origin of these filaments is still not understood. Star-forming regions are sometimes observed inside the filaments and are interpreted as evidence of positive feedback. Cen A is a nearby galaxy with huge optical filaments aligned with the AGN radio-jet direction. We searched for line ratio variations along the filaments, kinematic evidence of shock-broadend line widths, and large-scale dynamical structures. We observed a 1'x1' region around the inner filament of Cen A with MUSE on the VLT during Science Verification. The brightest lines detected are the Halpha, [NII], [OIII] and [SII]. MUSE shows that the filaments are made of clumpy structures inside a more diffuse medium aligned with the radio-jet axis. We find evidence of shocked shells surrounding the star-forming clumps from the line profiles, suggesting that the star formation is induced by shocks. The clump line ratios are best explained by a composite of shocks and star formation illuminated by a radiation cone from the AGN. We also report a previously undetected large arc-like structure: three streams running perpendicular to the main filament; they are kinematically, morphologically, and excitationally distinct. The clear difference in the excitation of the arcs and clumps suggests that the arcs are very likely located outside of the radiation cone and match the position of the filament only in projection. The three arcs are most consistent with neutral material swept along by a backflow of the jet plasma from the AGN outburst that is ionised through a diffuse radiation field with a low-ionisation parameter that continues to excite gas away from the radiation cone.

MAGNETIC FIELDS IN HIGH-MASS INFRARED DARK CLOUDS

High-mass Stars are cosmic engines known to dominate the energetics in the Milky Way and other galaxies. However, their formation is still not well understood. Massive, cold, dense clouds, often appearing as Infrared Dark Clouds (IRDCs), are the nurseries of massive stars. No measurements of magnetic fields in IRDCs in a state prior to the onset of high-mass star formation (HMSF) have previously been available, and prevailing HMSF theories do not consider strong magnetic fields. Here, we report observations of magnetic fields in two of the most massive IRDCs in the Milky Way. We show that IRDCs G11.11-0.12 and G0.253+0.016 are strongly magnetized and that the strong magnetic field is as important as turbulence and gravity for HMSF. The main dense filament in G11.11-0.12 is perpendicular to the magnetic field, while the lower density filament merging onto the main filament is parallel to the magnetic field. The implied magnetic field is strong enough to suppress fragmentation sufficiently to allow HMSF. Other mechanisms reducing fragmentation, such as the entrapment of heating from young stars via high mass surface densities, are not required to facilitate HMSF.