scholarly journals Core mass function: a comparison study between Orion A and other massive filamentary clouds.

2015 ◽  
Vol 11 (S315) ◽  
Author(s):  
Zhiyuan Ren ◽  
Di Li
Keyword(s):  
Mass Function ◽  
High Mass ◽  
Comparison Study ◽  
Core Mass ◽  
Similar Morphology ◽  
Dark Clouds ◽  
Power Law Index ◽  
Infrared Dark Clouds ◽  
Mass Functions ◽  
Measured Mass

AbstractAs a giant compact filamentary cloud, Orion A has a similar morphology with those more distant filaments in infrared dark clouds as revealed in Herschel surveys. We compared their core mass functions and found a similar power law index of N(>m)∝ m−1.0 for the high-mass end, which may possibly indicates a common case for massive filamentary clouds. We also show that the measured mass function for a certain cloud would largely depend on its distance, thus call for caution in interpreting individual measurements of CMF.

scholarly journals Massive and low-mass protostars in massive “starless” cores

2019 ◽  
Vol 622 ◽  
pp. A54 ◽  
Author(s):  
Thushara Pillai ◽  
Jens Kauffmann ◽  
Qizhou Zhang ◽  
Patricio Sanhueza ◽  
Silvia Leurini ◽  
...  
Keyword(s):  
Star Formation ◽  
Detection Limit ◽  
High Mass ◽  
Mass Star ◽  
Core Mass ◽  
Filamentary Structure ◽  
Dark Clouds ◽  
Low Mass ◽  
Infrared Dark Clouds ◽  
Dense Clump

The infrared dark clouds (IRDCs) G11.11−0.12 and G28.34+0.06 are two of the best-studied IRDCs in our Galaxy. These two clouds host clumps at different stages of evolution, including a massive dense clump in both clouds that is dark even at 70 and 100 μm. Such seemingly quiescent massive dense clumps have been speculated to harbor cores that are precursors of high-mass stars and clusters. We observed these two “prestellar” regions at 1 mm with the Submillimeter Array (SMA) with the aim of characterizing the nature of such cores. We show that the clumps fragment into several low- to high-mass cores within the filamentary structure of the enveloping cloud. However, while the overall physical properties of the clump may indicate a starless phase, we find that both regions host multiple outflows. The most massive core though 70 μm dark in both clumps is clearly associated with compact outflows. Such low-luminosity, massive cores are potentially the earliest stage in the evolution of a massive protostar. We also identify several outflow features distributed in the large environment around the most massive core. We infer that these outflows are being powered by young, low-mass protostars whose core mass is below our detection limit. These findings suggest that low-mass protostars have already formed or are coevally formed at the earliest phase of high-mass star formation.

scholarly journals The accretion history of high-mass stars: an ArTéMiS pilot study of infrared dark clouds

2020 ◽  
Vol 496 (3) ◽  
pp. 3482-3501 ◽  
Author(s):  
N Peretto ◽  
A Rigby ◽  
Ph André ◽  
V Könyves ◽  
G Fuller ◽  
...  
Keyword(s):  
Central Element ◽  
Dynamical Evolution ◽  
Mass Function ◽  
Initial Mass Function ◽  
High Mass ◽  
Mass Star ◽  
Mass Growth ◽  
Dark Clouds ◽  
History Of ◽  
Infrared Dark Clouds

ABSTRACT The mass growth of protostars is a central element to the determination of fundamental stellar population properties such as the initial mass function. Constraining the accretion history of individual protostars is therefore an important aspect of star formation research. The goal of the study presented here is to determine whether high-mass (proto)stars gain their mass from a compact (<0.1 pc) fixed-mass reservoir of gas, often referred to as dense cores, in which they are embedded, or whether the mass growth of high-mass stars is governed by the dynamical evolution of the parsec-scale clump that typically surrounds them. To achieve this goal, we performed a 350-μm continuum mapping of 11 infrared dark clouds, along side some of their neighbouring clumps, with the ArTéMiS camera on APEX. By identifying about 200 compact ArTéMiS sources, and matching them with Herschel Hi-GAL 70 -μm sources, we have been able to produce mass versus temperature diagrams. We compare the nature (i.e. starless or protostellar) and location of the ArTéMiS sources in these diagrams with modelled evolutionary tracks of both core-fed and clump-fed accretion scenarios. We argue that the latter provide a better agreement with the observed distribution of high-mass star-forming cores. However, a robust and definitive conclusion on the question of the accretion history of high-mass stars requires larger number statistics.

scholarly journals Core and stellar mass functions in massive collapsing filaments

2019 ◽  
Vol 625 ◽  
pp. A82 ◽  
Author(s):  
Evangelia Ntormousi ◽  
Patrick Hennebelle
Keyword(s):  
Star Formation ◽  
Flux Ratio ◽  
Mass Function ◽  
Initial Mass Function ◽  
Core Stability ◽  
High Mass ◽  
Core Mass ◽  
Hydrodynamical Simulation ◽  
Core Selection ◽  
Mass Functions

Context. The connection between the prestellar core mass function (CMF) and the stellar initial mass function (IMF) lies at the heart of all star formation theories, but it is inherently observationally unreachable. Aims. In this paper we aim to elucidate the earliest phases of star formation with a series of high-resolution numerical simulations that include the formation of sinks from high-density clumps. In particular, we focus on the transition from cores to sink particles within a massive molecular filament, and work towards identifying the factors that determine the shape of the CMF and the IMF. Methods. We have compared the CMF and IMF between magnetized and unmagnetized simulations, and between different resolutions. In order to study the effect of core stability, we applied different selection criteria according to the virial parameter and the mass-to-flux ratio of the cores. Results. We find that, in all models, selecting cores based on their kinematic virial parameter tends to exclude collapsing objects, because they host high velocity dispersions. Selecting only the thermally unstable magnetized cores, we observe that their mass-to-flux ratio spans almost two orders of magnitude for a given mass. We also see that, when magnetic fields are included, the CMF peaks at higher core mass values with respect to a pure hydrodynamical simulation. Nonetheless, all models produce sink mass functions with a high-mass slope consistent with Salpeter. Finally, we examined the effects of resolution and find that, in these isothermal simulations, even models with very high dynamical range fail to converge in the mass function. Conclusions. Our main conclusion is that, although the resulting CMFs and IMFs have similar slopes in all simulations, the cores have slightly different sizes and kinematical properties when a magnetic field is included, and this affects their gravitational stability. Nonetheless, a core selection based on the mass-to-flux ratio is not enough to alter the shape of the CMF, if we do not take thermal stability into account. Finally, we conclude that extreme care should be given to resolution issues when studying sink formation with an isothermal equation of state, since with each increase in resolution, fragmentation continues to smaller scales in a self-similar way.

scholarly journals Properties of the dense core population in Orion B as seen by the Herschel Gould Belt survey

2020 ◽  
Vol 635 ◽  
pp. A34 ◽  
Author(s):  
V. Könyves ◽  
Ph. André ◽  
D. Arzoumanian ◽  
N. Schneider ◽  
A. Men’shchikov ◽  
...  
Keyword(s):  
Molecular Cloud ◽  
Column Density ◽  
Mass Function ◽  
Smooth Transition ◽  
High Mass ◽  
Core Mass ◽  
Gould Belt ◽  
Dense Cores ◽  
Prestellar Cores ◽  
Consistent Manner

We present a detailed study of the Orion B molecular cloud complex (d ~ 400 pc), which was imaged with the PACS and SPIRE photometric cameras at wavelengths from 70 to 500 μm as part of the Herschel Gould Belt survey (HGBS). We release new high-resolution maps of column density and dust temperature for the whole complex, derived in the same consistent manner as for other HGBS regions. In the filamentary subregions NGC 2023 and 2024, NGC 2068 and 2071, and L1622, a total of 1768 starless dense cores were identified based on Herschel data, 490–804 (~28−45%) of which are self-gravitating prestellar cores that will likely form stars in the future. A total of 76 protostellar dense cores were also found. The typical lifetime of the prestellar cores was estimated to be tpreOrionB = 1.7−0.6+0.8Myr. The prestellar core mass function (CMF) derived for the whole sample of prestellar cores peaks at ~0.5 M⊙ (in dN/dlogM format) and is consistent with a power-law with logarithmic slope −1.27 ± 0.24 at the high-mass end, compared to the Salpeter slope of − 1.35. In the Orion B region, we confirm the existence of a transition in prestellar core formation efficiency (CFE) around a fiducial value AVbg ~ 7 mag in background visual extinction, which is similar to the trend observed with Herschel in other regions, such as the Aquila cloud. This is not a sharp threshold, however, but a smooth transition between a regime with very low prestellar CFE at AVbg < 5 and a regime with higher, roughly constant CFE at AVbg ≳ 10. The total mass in the form of prestellar cores represents only a modest fraction (~20%) of the dense molecular cloud gas above AVbg ≳ 7 mag. About 60–80% of the prestellar cores are closely associated with filaments, and this fraction increases up to >90% when a more complete sample of filamentary structures is considered. Interestingly, the median separation observed between nearest core neighbors corresponds to the typical inner filament width of ~0.1 pc, which is commonly observed in nearby molecular clouds, including Orion B. Analysis of the CMF observed as a function of background cloud column density shows that the most massive prestellar cores are spatially segregated in the highest column density areas, and suggests that both higher- and lower-mass prestellar cores may form in denser filaments.

scholarly journals MAGNETIC FIELDS IN HIGH-MASS INFRARED DARK CLOUDS

2015 ◽  
Vol 799 (1) ◽  
pp. 74 ◽  
Author(s):  
T. Pillai ◽  
J. Kauffmann ◽  
J. C. Tan ◽  
P. F. Goldsmith ◽  
S. J. Carey ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
High Mass ◽  
Dark Clouds ◽  
Infrared Dark Clouds

scholarly journals Analogues of Cores and Stars in Simulated Molecular Clouds

2010 ◽  
Vol 6 (S270) ◽  
pp. 129-132
Author(s):  
James Wadsley ◽  
Michael Reid ◽  
Farid Qamar ◽  
Alison Sills ◽  
Nicholas Petitclerc
Keyword(s):  
Molecular Cloud ◽  
Molecular Clouds ◽  
Angular Resolution ◽  
Mass Function ◽  
High Mass ◽  
Finite Image ◽  
Cautionary Tales ◽  
Mass Functions

AbstractWe use images derived from collapsing, turbulent molecular cloud simulations without sinks to explore the effects of finite image angular resolution and noise on the derived clump mass function. These effects randomly perturb the clump masses, producing a lognormal clump mass function with a Salpeter-like high mass end. We show that the characteristic break mass of the simulated clump mass functions changes with the angular resolution of the images in a way that is entirely consistent with the observations. We also present some cautionary tales regarding sink particles and highlight the need to ensure that sinks actually correspond to distinct collapsing objects. We test several popular numerical sink criteria in the literature and compare to converged, non-sink results.

scholarly journals Observational Studies of Pre-Stellar Cores and Infrared Dark Clouds

2011 ◽  
Vol 7 (S280) ◽  
pp. 19-32 ◽  
Author(s):  
Paola Caselli
Keyword(s):  
Molecular Cloud ◽  
Chemical Structure ◽  
Initial Conditions ◽  
Theoretical Work ◽  
High Mass ◽  
Mass Star ◽  
Stellar Cluster ◽  
Dark Clouds ◽  
Low Mass ◽  
Infrared Dark Clouds

AbstractStars like our Sun and planets like our Earth form in dense regions within interstellar molecular clouds, called pre-stellar cores (PSCs). PSCs provide the initial conditions in the process of star and planet formation. In the past 15 years, detailed observations of (low-mass) PSCs in nearby molecular cloud complexes have allowed us to find that they are cold (T < 10K) and quiescent (molecular line widths are close to thermal), with a chemistry profoundly affected by molecular freeze-out onto dust grains. In these conditions, deuterated molecules flourish, becoming the best tools to unveil the PSC physical and chemical structure. Despite their apparent simplicity, PSCs still offer puzzles to solve and they are far from being completely understood. For example, what is happening to the gas and dust in their nuclei (the future stellar cradles) is still a mystery that awaits for ALMA. Other important questions are: how do different environments and external conditions affect the PSC physical/chemical structure? Are PSCs in high-mass star forming regions similar to the well-known low-mass PSCs? Here I review observational and theoretical work on PSCs in nearby molecular cloud complexes and the ongoing search and study of massive PSCs embedded in infrared dark clouds (IRDCs), which host the initial conditions for stellar cluster and high-mass star formation.

scholarly journals Statistical mass function of prestellar cores from the density distribution of their natal clouds

2020 ◽  
Vol 635 ◽  
pp. A88
Author(s):  
S. Donkov ◽  
T. V. Veltchev ◽  
Ph. Girichidis ◽  
R. S. Klessen
Keyword(s):  
Power Law ◽  
Molecular Clouds ◽  
Mass Density ◽  
Mass Function ◽  
Initial Mass Function ◽  
High Mass ◽  
Core Mass ◽  
Density Relationship ◽  
Prestellar Cores ◽  
Spherical Cloud

The mass function of clumps observed in molecular clouds raises interesting theoretical issues, especially in its relation to the stellar initial mass function (IMF). We propose a statistical model of the mass function of prestellar cores (CMF), formed in self-gravitating isothermal clouds at a given stage of their evolution. The latter is characterized by the mass-density probability distribution function (ρ-PDF), which is a power-law with slope q. The different molecular clouds are divided into ensembles according to the PDF slope and each ensemble is represented by a single spherical cloud. The cores are considered as elements of self-similar structure typical for fractal clouds and are modeled by spherical objects populating each cloud shell. Our model assumes relations between size, mass, and density of the statistical cores. Out of these, a core mass-density relationship ρ ∝ mx is derived where x = 1∕(1 + q). We find that q determines the existence or nonexistence of a threshold density for core collapse. The derived general CMF is a power law of slope − 1 while the CMF of gravitationally unstable cores has a slope (−1 + x∕2), comparable with the slopes of the high-mass part of the stellar IMF and of observational CMFs.

scholarly journals Dense cores and star formation in the giant molecular cloud Vela C

2019 ◽  
Vol 628 ◽  
pp. A110 ◽  
Author(s):  
F. Massi ◽  
A. Weiss ◽  
D. Elia ◽  
T. Csengeri ◽  
E. Schisano ◽  
...  
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Galactic Plane ◽  
Mass Function ◽  
Initial Mass Function ◽  
High Mass ◽  
Mass Star ◽  
Ancillary Data ◽  
Core Mass ◽  
Giant Molecular Cloud

Context. The Vela Molecular Ridge is one of the nearest (700 pc) giant molecular cloud (GMC) complexes hosting intermediate-mass (up to early B, late O stars) star formation, and is located in the outer Galaxy, inside the Galactic plane. Vela C is one of the GMCs making up the Vela Molecular Ridge, and exhibits both sub-regions of robust and sub-regions of more quiescent star formation activity, with both low- and intermediate(high)-mass star formation in progress. Aims. We aim to study the individual and global properties of dense dust cores in Vela C, and aim to search for spatial variations in these properties which could be related to different environmental properties and/or evolutionary stages in the various sub-regions of Vela C. Methods. We mapped the submillimetre (345 GHz) emission from vela C with LABOCA (beam size ~19′′2, spatial resolution ~0.07 pc at 700 pc) at the APEX telescope. We used the clump-finding algorithm CuTEx to identify the compact submillimetre sources. We also used SIMBA (250 GHz) observations, and Herschel and WISE ancillary data. The association with WISE red sources allowed the protostellar and starless cores to be separated, whereas the Herschel dataset allowed the dust temperature to be derived for a fraction of cores. The protostellar and starless core mass functions (CMFs) were constructed following two different approaches, achieving a mass completeness limit of 3.7 M⊙. Results. We retrieved 549 submillimetre cores, 316 of which are starless and mostly gravitationally bound (therefore prestellar in nature). Both the protostellar and the starless CMFs are consistent with the shape of a Salpeter initial mass function in the high-mass part of the distribution. Clustering of cores at scales of 1–6 pc is also found, hinting at fractionation of magnetised, turbulent gas.

Binary “Post-AGB” Stars

2000 ◽  
Vol 177 ◽  
pp. 285-291 ◽  
Author(s):  
Hans Van Winckel ◽  
Christoffel Waelkens ◽  
Laurens B.F.M. Waters
Keyword(s):  
Large Mass ◽  
Mass Function ◽  
High Mass ◽  
Evolutionary Stage ◽  
Agb Stars ◽  
Near Ir ◽  
Widespread Phenomenon ◽  
Orbital Periods ◽  
Mass Functions ◽  
Chemical Influence

In this contribution we report on our radial-velocity monitoring of optically bright, high-latitude supergiants that appear to be in a post-AGB evolutionary stage. Binarity is a widespread phenomenon among our sample stars. More precisely: all objects with a near-IR excess in their energy distribution turn out to be binaries while the fraction of binaries in our program stars with only a far-IR excess is very small. The orbital periods, the often non-zero eccentricities, and the sometimes large mass functions set strong constraints on the previous evolution in which mass transfer must have been an important ingredient. We have accumulated observational evidence that the presence of a circum-binary dusty disk has an important dynamical and sometimes even chemical influence on the binary and its evolution. Some objects with a high mass function still defy an explanation.

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