The Serpens filament, a prominent elongated structure in a relatively nearby molecular cloud, is believed to be at an early evolutionary stage, so studying its physical and chemical properties can shed light on filament formation and early evolution. The main goal is to address the physical and chemical properties as well as the dynamical state of the Serpens filament at a spatial resolution of $\sim$0.07 pc and a spectral resolution of $\lesssim$0.1~km~s$^{-1}$. We performed $^{13}$CO (1--0), C$^{18}$O (1--0), C$^{17}$O (1--0), $^{13}$CO (2--1), C$^{18}$O (2--1), and C$^{17}$O (2--1) imaging observations toward the Serpens filament with the Institut de Radioastronomie Millim{é}trique 30-m (IRAM-30 m) and Atacama Pathfinder EXperiment (APEX) telescopes. Widespread narrow $^{13}$CO (2--1) self-absorption is observed in this filament, causing the $^{13}$CO morphology to be different from the filamentary structure traced by C$^{18}$O and C$^{17}$O. Our excitation analysis suggests that the opacities of C$^{18}$O transitions become higher than unity in most regions, and this analysis confirms the presence of widespread CO depletion. Further we show that the local velocity gradients have a tendency to be perpendicular to the filament's long axis in the outskirts and parallel to the large-scale magnetic field direction. The magnitudes of the local velocity gradients decrease toward the filament's crest. The observed velocity structure can be a result of gravity-driven accretion flows. The isochronic evolutionary track of the C$^{18}$O freeze-out process indicates the filament is young with an age of $\lesssim$2 Myr. We propose that the Serpens filament is a newly-formed slightly-supercritical structure which appears to be actively accreting material from its ambient gas.
The Serpens filament, as one of the nearest infrared dark clouds, is regarded as a pristine filament at a very early evolutionary stage of star formation. In order to study its molecular content and dynamical state, we mapped this filament in seven species. Among them, HCO$^{+}$, HNC, HCN, and CS show self-absorption, while C$^{18}$O is most sensitive to the filamentary structure. A kinematic analysis demonstrates that this filament forms a velocity-coherent (trans-)sonic structure, a large part of which is one of the most quiescent regions in the Serpens cloud. Widespread C$^{18}$O depletion …
TRAO Survey of the Nearby Filamentary Molecular Clouds, the Universal Nursery of Stars (TRAO-FUNS). IV. Filaments and Dense Cores in the W40 and Serpens South Regions of Aquila
Filaments represent a key structure during the early stages of the star formation process. Simulations show filamentary structure commonly formed before and during the formation of cores. Aims. The Serpens Core represents an ideal laboratory to test the state-of-the-art of simulations of turbulent Giant Molecular Clouds. We use Herschel observations of the Serpens Core to compute temperature and column density maps of the region. Among the simulations of Dale et al. (2012), we select the early stages of their Run I, before stellar feedback is initiated, with similar total mass and physical siz…
We present H13CO+ (J=1-0) and HNC (J=1-0) maps of regions in Serpens South, Serpens Main and NGC 1333 containing filaments. We also observe the Serpens regions using H13CN (J=1-0). These dense gas tracer molecular line observations carried out with CARMA have an angular resolution of ~7", a spectral resolution of ~0.16 km/s and a sensitivity of 50-100 mJy/beam. Although the large scale structure compares well with the Herschel dust continuum maps, we resolve finer structure within the filaments identified by Herschel. The H13CO+ emission distribution agrees with the existing CARMA N2H+ (J=1-0)…
Filamentary structures are ubiquitous in molecular clouds, and have been recently argued to play an important role in regulating the size and mass of embedded clumps through fragmentation and mass accretion. Here, we reveal the dynamical state and fragmentation of filamentary molecular gas associated with the Serpens South protocluster through analysis of wide (~4 x 4 pc) observations of NH3 (1,1) and (2,2) inversion transitions with the Green Bank Telescope. Detailed modeling of the NH3 lines reveals that the kinematics of the cluster and surrounding filaments are complex. We identify hierarc…
We present the N2H+(J=1-0) map of the Serpens South molecular cloud obtained as part of the CARMA Large Area Star Formation Survey (CLASSy). The observations cover 250 square arcminutes and fully sample structures from 3000 AU to 3 pc with a velocity resolution of 0.16 km/s, and they can be used to constrain the origin and evolution of molecular cloud filaments. The spatial distribution of the N2H+ emission is characterized by long filaments that resemble those observed in the dust continuum emission by Herschel. However, the gas filaments are typically narrower such that, in some cases, two o…
One puzzle in understanding how stars form in clusters is the source of mass -- is all of the mass in place before the first stars are born, or is there an extended period when the cluster accretes material which can continuously fuel the star formation process? We use a multi-line spectral survey of the southern filament associated with the Serpens South embedded cluster-forming region in order to determine if mass is accreting from the filament onto the cluster, and whether the accretion rate is significant. Our analysis suggests that material is flowing along the filament's long axis at a r…
We present observations of N2H+(1-0), HCO+(1-0), and HCN(1-0) toward the Serpens Main molecular cloud from the CARMA Large Area Star Formation Survey (CLASSy). We mapped 150 square arcminutes of Serpens Main with an angular resolution of 7 arcsecs. The gas emission is concentrated in two subclusters (the NW and SE subclusters). The SE subcluster has more prominent filamentary structures and more complicated kinematics compared to the NW subcluster. The majority of gas in the two subclusters has subsonic to sonic velocity dispersions. We applied a dendrogram technique with N2H+(1-0) to study th…
Observations indicate that molecular clouds are strongly magnetized, and that magnetic fields influence the formation of stars. A key observation supporting the conclusion that molecular clouds are significantly magnetized is that the orientation of their internal structure is closely related to that of the magnetic field. At low column densities the structure aligns parallel with the field, whereas at higher column densities, the gas structure is typically oriented perpendicular to magnetic fields, with a transition at visual extinctions $A_V\gtrsim{}3~\rm{}mag$. Here we use far-infrared pola…
The Serpens South infrared dark cloud consists of several filamentary ridges, some of which fragment into dense clumps. On the basis of CCS ($J_N=4_3-3_2$), HC$_3$N ($J=5-4$), N$_2$H$^+$ ($J=1-0$), and SiO ($J=2-1, v=0$) observations, we investigated the kinematics and chemical evolution of these filamentary ridges. We find that CCS is extremely abundant along the main filament in the protocluster clump. We emphasize that Serpens South is the first cluster-forming region where extremely-strong CCS emission is detected. The CCS-to-N$_2$H$^+$ abundance ratio is estimated to be about 0.5 toward t…
We present the results of N$_2$H$^+$ ($J=1-0$) observations toward Serpens South, the nearest cluster-forming, infrared dark cloud. The physical quantities are derived by fitting the hyperfine structure of N$_2$H$^+$. The Herschel and 1.1-mm continuum maps show that a pc-scale filament fragments into three clumps with radii of $0.1-0.2$ pc and masses of $40-230M_\odot$. We find that the clumps contain smaller-scale ($\sim 0.04$ pc) structures, i.e., dense cores. We identify 70 cores by applying CLUMPFIND to the N$_2$H$^+$ data cube. In the central cluster-forming clump, the excitation temperat…
We mapped 12CO and 13CO J = 2-1 emission over 1.04 square deg of the Serpens molecular cloud with 38 arcsec spatial and 0.3 km/s spectral resolution using the Arizona Radio Observatory Heinrich Hertz Submillimeter telescope. Our maps resolve kinematic properties for the entire Serpens cloud. We also compare our velocity moment maps with known positions of Young Stellar Objects (YSOs) and 1.1 mm continuum emission. We find that 12CO is self-absorbed and 13CO is optically thick in the Serpens core. Outside of the Serpens core, gas appears in filamentary structures having LSR velocities which are…
Jets and outflows accompany the mass accretion process in protostars and young stellar objects. Using a large and unbiased sample, they can be used to study statistically the local feedback they provide and the typical mass accretion history. Here we analyse such a sample of Molecular Hydrogen emission line Objects in the Serpens and Aquila part of the Galactic Plane. Distances are measured by foreground star counts with an accuracy of 25%. The resulting spacial distribution and outflow luminosities indicate that our objects sample the formation of intermediate mass objects. The outflows are u…
We present a Chandra study of the deeply embedded Serpens South star-forming region, examining cluster structure and disk properties at the earliest stages. In total, 152 X-ray sources are detected. Combined with Spitzer and 2MASS photometry, 66 X-ray sources are reliably matched to an IR counterpart. We identify 21 class I, 6 flat spectrum, 16 class II, and 18 class III young stars; 5 were unclassified. Eighteen sources were variable in X-rays, 8 exhibiting flare-like emission, and one periodic source. The cluster X-ray luminosity distance was estimated, the best match was to the nearer dista…
The complexity of the ISM is such that it is unlikely that star formation is initiated in the same way in all molecular clouds. While some clouds seem to collapse on their own, others may be triggered by an external event such as a cloud/flow collision forming a gravitationally unstable enhanced density layer. This work tests cloud-cloud collisions as the triggering mechanism for star formation in the Serpens Main Cluster as has been suggested by previous work. A set of smoothed particle hydrodynamics (SPH) simulations of the collision between two cylindrical clouds are performed and compared …
We present 850 $μ$m polarimetric observations toward the Serpens Main molecular cloud obtained using the POL-2 polarimeter on the James Clerk Maxwell Telescope (JCMT) as part of the B-fields In STar-forming Region Observations (BISTRO) survey. These observations probe the magnetic field morphology of the Serpens Main molecular cloud on about 6000 au scales, which consists of cores and six filaments with different physical properties such as density and star formation activity. Using the histogram of relative orientation (HRO) technique, we find that magnetic fields are parallel to filaments in…
During the protostellar phase of stellar evolution, accretion onto the star is expected to be variable, but this suspected variability has been difficult to detect because protostars are deeply embedded. In this paper, we describe a sub-mm luminosity burst of the Class I protostar EC 53 in Serpens Main, the first variable found during our dedicated JCMT/SCUBA-2 monitoring program of eight nearby star-forming regions. EC 53 remained quiescent for the first 6 months of our survey, from February to August 2016. The sub-mm emission began to brighten in September 2016, reached a peak brightness of …
We study accretion driven turbulence for different inflow velocities in star forming filaments using the code ramses. Filaments are rarely isolated objects and their gravitational potential will lead to radially dominated accretion. In the non-gravitational case, accretion by itself can already provoke non-isotropic, radially dominated turbulent motions responsible for the complex structure and non-thermal line widths observed in filaments. We find that there is a direct linear relation between the absolute value of the total density weighted velocity dispersion and the infall velocity. The tu…
In typical environments of star-forming clouds, converging supersonic turbulence generates shock-compressed regions, and can create strongly-magnetized sheet-like layers. Numerical MHD simulations show that within these post-shock layers, dense filaments and embedded self-gravitating cores form via gathering material along the magnetic field lines. As a result of the preferred-direction mass collection, a velocity gradient perpendicular to the filament major axis is a common feature seen in simulations. We show that this prediction is in good agreement with recent observations from the CARMA L…
We explore how dense filament widths, when measured using different molecular species, may change as a consequence of gas accretion toward the filament. As a gas parcel falls into the filament, it will experience different density, temperature, and extinction values. The rate at which this environment changes will affect differently the abundance of different molecules. So, a molecule that forms quickly will better reflect the local physical conditions a gas parcel experiences than a slower-forming molecule. Since these differences depend on how the respective timescales compare, the different…
A comparison of accretion and (turbulent) magnetic diffusion timescales for sheets and filaments demonstrates that dense star-forming clouds generally will -- under realistic conditions -- become supercritical due to mass accretion on timescales at least an order of magnitude shorter than ambipolar and/or turbulent diffusion timescales. Thus, ambipolar or turbulent diffusion -- while present -- is unlikely to control the formation of cores and stars.
We extend our previous work on simulations with the code RAMSES on accretion driven turbulence by including self-gravity and study the effects of core formation and collapse. We show that radial accretion onto filaments drives turbulent motions which are not isotropic but radially dominated. In contrast to filaments without gravity, the velocity dispersion of self-gravitating filaments does not settle in an equilibrium. Despite showing similar amounts of driven turbulence, they continually dissipate their velocity dispersion until the onset of core formation. This difference is connected to th…
Filamentary structures are ubiquitous in high-mass star-forming molecular clouds. Their relation with high-mass star formation is still to be understood. Here we report interferometric observations toward 8 filamentary high-mass star-forming clouds. A total of 50 dense cores are identified in these clouds, most of which present signatures of high-mass star formation. Five of them are not associated with any star formation indicators, hence are prestellar core candidates. Evolutionary phases of these cores and their linewidths, temperatures, NH$_3$ abundances, and virial parameters are found to…
High-resolution observations of the Perseus B5 "core" have previously revealed that this subsonic region actually consists of several filaments that are likely in the process of forming a quadruple stellar system. Since subsonic filaments are thought to be produced at the $\sim 0.1$ pc sonic scale by turbulent compression, a detailed kinematic study is crucial to test such a scenario in the context of core and star formation. Here we present a detailed kinematic follow-up study of the B5 filaments at a 0.009 pc resolution using the VLA and GBT combined observations fitted with multi-component …
Recent Herschel observations have confirmed that filaments are ubiquitous in molecular clouds and suggest that irrespectively of the column density, there is a characteristic width of about 0.1 pc whose physical origin remains unclear. We develop an analytical model that can be applied to self-gravitating accreting filaments. It is based on one hand on the virial equilibrium of the central part of the filament and on the other hand on energy balance between the turbulence driven by accretion onto the filament and dissipation. We consider two dissipation mechanisms the turbulent cascade and the…
Herschel observations have emphasized the role of molecular filaments in star formation. However, the origin and evolution of these filaments are not yet well understood, partly because of the lack of kinematic information. To examine whether the B211/B213 filament is accreting background gas due to its gravitational potential, we produced a toy accretion model and compared its predictions to the 12CO(1--0) and 13CO(1--0) velocity patterns. We also examined the spatial distributions of Halpha, 857 GHz continuum, and HI emission to search for evidence of large-scale external effects. We estimat…
Context. Dense molecular filaments are ubiquituous in the interstellar medium, yet their internal physical conditions and formation mechanism remain debated. Aims. We study the kinematics and physical conditions in the Musca filament and the Chamaeleon-Musca complex to constrain the physics of filament formation. Methods. We produced CO(2-1) isotopologue maps with the APEX telescope that cut through the Musca filament. We further study a NANTEN2 $^{12}$CO(1-0) map of the Musca cloud and the HI emission of the Chamaeleon-Musca complex. Results. The Musca cloud contains multiple velocity compone…
Filament S242 is 25 pc long with massive clumps and YSO clusters concentrated in its end regions; it is considered a good example of edge collapse. We mapped this filament in the $^{12}$CO(1-0) and $^{13}$CO(1-0) lines. A large-scale velocity gradient along filament S242 has been detected; the relative velocity between the two end-clumps is $\sim$ 3 km s$^{-1}$, indicating an approaching motion between them. These signatures are consistent with the filament S242 being formed through the collapse of a single elongated entity, where an effect known as "gravitational focusing" drives the ends of …
Recent observations of global velocity gradients across and along molecular filaments have been interpreted as signs of gas accreting onto and along these filaments, potentially feeding star-forming cores and proto-clusters. The behavior of velocity gradients in filaments, however, has not been studied in detail, particularly on small scales (< 0.1 pc). In this paper, we present MUFASA, an efficient, robust, and automatic method to fit ammonia lines with multiple velocity components, generalizable to other molecular species. We also present CRISPy, a Python package to identify filament spines …
Two aspects of filamentary molecular cloud evolution are addressed: (1) Exploring analytically the role of the environment for the evolution of filaments demonstrates that considering them in isolation (i.e. just addressing the fragmentation stability) will result in unphysical conclusions about the filament's properties. Accretion can also explain the observed decorrelation between FWHM and peak column density. (2) Free-fall accretion onto finite filaments can lead to the characteristic "fans" of infrared-dark clouds around star-forming regions. The fans may form due to tidal forces mostly ar…
We present idealized numerical simulations of prestellar gravitational collapse of a moderate initial filamentary perturbation with an additional central ellipsoidal enhancement (a core) considering a uniform, and a stratified background, the latter representing flattened clouds. Both simulations maintain the filamentary structure during the collapse, developing a hierarchical accretion flow from the cloud to the plane; from there to the filament, and from the filament to the core. The flow changes direction smoothly at every step of the hierarchy, with no density divergence nor a shock develo…
DR21 south filament (DR21SF) is a unique component of the giant network of filamentary molecular clouds in the north region of Cygnus X complex. Unlike the highly fragmented and star-forming active environment it resides, DR21SF exhibits a coherent profile in the column density map with very few star formation signposts, even though the previously reported linear density of the filament is an order of magnitude higher than the thermal stable threshold. We derive the size (3.6~pc by 0.13~pc), temperature (10 to 15~K), and mass (1048~\textit{M$_\odot$}) of DR21SF from Shanghai 65 m TianMa Radio …
We use a suite a cooling halo simulations to study a new mechanism for rapid accretion of hot halo gas onto star-forming galaxies. Correlated supernovae events create converging 'superbubbles' in the halo gas. Where these collide, the density increases, driving cooling filaments of low metallicity gas that feed the disc. At our current numerical resolution (20 pc) we are only able to resolve the most dramatic events; these could be responsible for the build-up of galaxy discs after the most massive gas-rich mergers have completed (z < 1). As we increase the numerical resolution, we find that t…
We present mapping results of two prestellar cores, L1544 and L694-2, embedded in filamentary clouds in C$^{18}$O (3-2), $^{13}$CO (3-2), $^{12}$CO (3-2), HCO$^+$ (4-3), and H$^{13}$CO$^+$ (4-3) with the JCMT telescope to examine the role of the filamentary structures in the formation of dense cores in the clouds, with new distance estimates for L1544 ($175_{-3}^{+4}$ pc) and L694-2 ($203_{-7}^{+6}$ pc). From these observations, we found that the non-thermal velocity dispersion of two prestellar cores and their surrounding clouds are smaller than or comparable to the sound speed. This may indi…
Dark matter haloes are formed through hierarchical mergers of smaller haloes in large-scale cosmic environments, and thus anisotropic subhalo accretion through cosmic filaments have some impacts on halo structures. Recent studies using cosmological simulations have shown that the orientations of haloes correlate with the direction of cosmic filaments, and these correlations significantly depend on the halo mass. Using high-resolution cosmological $N$-body simulations, we quantified the strength of filamentary subhalo accretion for galaxy- and group-sized host haloes ($M_{\rm host}=5\times10^{1…
We examine the HI-to-stellar mass ratio (HI fraction) for galaxies near filament backbones within the nearby Universe ($d <$ 181 Mpc). This work uses the 6 degree Field Galaxy Survey and the Discrete Persistent Structures Extractor to define the filamentary structure of the local cosmic web. HI spectral stacking of HI Parkes all sky survey observations yields the HI fraction for filament galaxies and a field control sample. The HI fraction is measured for different stellar masses and fifth nearest neighbour projected densities ($Σ_{5}$) to disentangle what influences cold gas in galaxies. For …
Hub-filament systems and the growth of massive stars: episodic accretion, clustered environments, and projection effects
Nazarbayev University（纳扎尔巴耶夫大学）；Institut de Ciències del Cosmos (ICCUB), Universitat de Barcelona (UB)（巴塞罗那大学宇宙科学研究所）；Dartmouth College（达特茅斯学院）；University of Helsinki（赫尔辛基大学）；Kavli Institute for Astronomy and Astrophysics, Peking University（北京大学卡尔文天体物理研究所）
The mid- and far-infrared view on high-mass star formation, in particular with the results from the Herschel space observatory, has shed light on many aspects of massive star formation. However, these continuum studies lack kinematic information. We study the kinematics of the molecular gas in high-mass star-forming regions. We complemented the PACS and SPIRE far-infrared data of 16 high-mass star-forming regions from the Herschel key project EPoS with N2H+ molecular line data from the MOPRA and Nobeyama 45m telescope. Using the full N2H+ hyperfine structure, we produced column density, veloci…
Theory suggests that there are two primary modes of accretion through which dark matter halos acquire the gas to form and fuel galaxies, hot and cold mode accretion. In cold mode accretion, gas streams along cosmic web filaments to the center of the halo, allowing for the efficient delivery of star-forming fuel. Recently, two QSO-illuminated HI Lyman alpha (Lyα) emitting objects were reported to have properties of cold, rotating structures (Martin et al. 2015, Martin et al. 2016). However, the spatial and spectral resolution available was insufficient to constrain radial flows associated with …
Observed HI accretion around nearby galaxies can only account for a fraction of the gas supply needed to sustain the currently observed star formation rates. It is possible that additional accretion happens in the form of low column density cold flows, as predicted by numerical simulations of galaxy formation. To contrain the presence and properties of such flows, we present deep HI observations obtained with the NRAO Green Bank Telescope of an area measuring 4 by 4 degrees around NGC 2403. These observations, with a 5 sigma detection limit of 2.4 x 10^18 cm^-2 over a 20 km/s linewidth, reveal…
G183: An outer galaxy filament feeding a massive protostar
Tata Institute of Fundamental Research（塔塔基础研究所）；Max Planck Institut für Radioastronomie（马克斯·普朗克射电天文研究所）；Institut de Radioastronomie Millimétrique (IRAM)（毫米波射电天文研究所）
We present ALMA observations of the dust continuum and [C II] 158um line emission from the z=6.0695 Lyman Break Galaxy WMH5. These observations at 0.3" spatial resolution show a compact (~3kpc) main galaxy in dust and [C II] emission, with a 'tail' of emission extending to the east by about 5kpc (in projection). The [C II] tail is comprised predominantly of two distinct sub-components in velocity, separated from the core by ~100 and 250km/s, with narrow intrinsic widths of about 80km/s, which we call 'sub-galaxies'. The sub-galaxies themselves are extended east-west by about 3kpc in individual…
We track subhalo orbits of galaxy and group sized halos in cosmological simulations. We identify filamentary structures around halos and we use these to define a sample of subhalos accreted from filaments as well as a control sample of subhalos accreted from other directions. We use these samples to study differences in satellite orbits produced by filamentary accretion. Our results depend on host halo mass. We find that for low masses, subhalos accreted from filaments show $\sim10\%$ shorter lifetimes compared to the control sample, they show a tendency towards more radial orbits, reach halo …
We investigate the impact of cosmic filaments on the gas accretion rate, $\dot{M}_{\rm{gas}}$, of dark matter halos in filaments, based on cosmological hydrodynamic simulation. We find that for halos less massive than $10^{12.0}\ \rm{M_{\odot}}$, $\dot{M}_{\rm{gas}}$ of halos residing in prominent filaments (with width $D_{\rm{fil}}>3\ \rm{Mpc}/h$) is lower than halos residing in tenuous filaments ($D_{\rm{fil}}<3\ \rm{Mpc}/h$) by $20-30\%$ at $z=0.5$, and by a factor of 2-3 at $z=0$. However, $\dot{M}_{\rm{gas}}$ depends weakly on the physical distance between halo center and the spine of fil…
We have used an unbiased, spectral line-survey that covers the frequency range from 211 to 275 GHz and was obtained with ALMA (angular resolution of 0.4 arcsec) to study the small-scale structure of the dense gas in Sagittarius B2 (north). Eight filaments are found converging to the central hub and extending for about 0.1 pc. The spatial structure, together with the presence of the massive central region, suggest that these filaments may be associated with accretion processes. In order to derive the kinematic properties of the gas in a chemically line-rich source like Sgr B2(N), we have develo…
We present ALMA Band-3/7 observations towards "the Heart" of a massive hub-filament system (HFS) SDC335, to investigate its fragmentation and accretion. At a resolution of $\sim0.03$ pc, 3 mm continuum emission resolves two massive dense cores MM1 and MM2, with $383(^{+234}_{-120})$ $M_\odot$ (10-24% mass of "the Heart") and $74(^{+47}_{-24})$ $M_\odot$, respectively. With a resolution down to 0.01 pc, 0.87 mm continuum emission shows MM1 further fragments into six condensations and multi-transition lines of H$_2$CS provide temperature estimation. The relation between separation and mass of co…
Cosmic web stripping and starvation of low-mass filament galaxies in TNG50
INAF – Osservatorio Astronomico di Trieste（意大利国家天体物理研究所的里雅斯特天文台）；IFPU – Institute for Fundamental Physics of the Universe（宇宙基础物理研究所）；INAF – Osservatorio Astronomico di Padova（意大利国家天体物理研究所帕多瓦天文台）；Tianjin Normal University（天津师范大学）；Sydney Institute for Astronomy (SIfA), School of Physics, The University of Sydney（悉尼大学物理学院天体物理研究所）；School of Physics and Astronomy, University of Birmingham（伯明翰大学物理与天文学院）
Discovery of a Compact Hub-Filament System in G286.21+0.17 with JWST and ALMA: Insights into Protocluster Formation and Competitive Accretion
Peking University（北京大学）；National Astronomical Research Institute of Thailand（泰国国家天文研究所）；Gifu University（岐阜大学）；Indian Institute of Technology Gandhinagar（甘地纳加尔印度理工学院）；Korea Astronomy and Space Science Institute（韩国天文学与宇宙科学研究所）；University of Science and Technology, Korea (UST)（韩国科学技术院）；Jet Propulsion Laboratory, California Institute of Technology（加州理工学院喷气推进实验室）；Nazarbayev University（纳扎尔巴耶夫大学）
We present the results of smoothed particle hydrodynamic simulations investigating the evolution and fragmentation of filaments that are accreting from a turbulent medium. We show that the presence of turbulence, and the resulting inhomogeneities in the accretion flow, play a significant role in the fragmentation process. Filaments which experience a weakly turbulent accretion flow fragment in a two-tier hierarchical fashion, similar to the fragmentation pattern seen in the Orion Integral Shaped Filament. Increasing the energy in the turbulent velocity field results in more sub-structure withi…
SIMPLIFI -- Study of Interstellar Magnetic Polarization: a Legacy Investigation of Filaments. I. Magnetically-Guided Accretion onto the DR21 Ridge
Massachusetts Institute of Technology（麻省理工学院）；Istituto di Astrofisica e Planetologia Spaziali (IAPS). INAF（空间天体物理学和行星科学研究所（IAPS），意大利国家天体物理研究所（INAF））；University of Vienna（维也纳大学）；University of Massachusetts, Amherst（马萨诸塞大学阿默斯特分校）；Queen’s University（女王大学）；Boston University（波士顿大学）；Nagoya City University（名古屋市立大学）；University of South Carolina（南卡罗来纳大学）；National Astronomical Observatory of Japan（日本国立天文台）；INAF - Istituto di Radioastronomia di Bologna（意大利国家天体物理研究所-博洛尼亚射电天文研究所）
The interstellar medium contains filamentary structure over a wide range of scales. Understanding the role of this structure, both as a conduit of gas across the scales and a diagnostic tool of local physics, is a major focus of star formation studies. We review recent progress in studying filamentary structure in the ISM, interpreting its properties in terms of physical processes, and exploring formation and evolution scenarios. We include structures from galactic-scale filaments to tenth-of-a-parsec scale filaments, comprising both molecular and atomic structures, from both observational and…
How mass is accumulated from cloud-scale down to individual stars is a key open question in understanding high-mass star formation. Here, we present the mass accumulation process in a hub-filament cloud G22 which is composed of four supercritical filaments. Velocity gradients detected along three filaments indicate that they are collapsing with a total mass infall rate of about 440 $M_\odot$ Myr$^{-1}$, suggesting the hub mass would be doubled in six free-fall times, adding up to $ \sim2 $ Myr. A fraction of the masses in the central clumps C1 and C2 can be accounted for through large-scale fi…
