Origin of the prestellar core mass function and link to the IMF – <i>Herschel</i> first results

André, Ph.; Könyves, V.; Arzoumanian, D.

doi:10.1017/s1743921311000470

Cited by 10 publications

(7 citation statements)

References 38 publications

(56 reference statements)

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“…At this stage, it is evident that sub-fragmentation of larger clumps into smaller cores is still likely underway as there is a significant population of massive fragments. However, even at this fairly early stage in their life cycle, this initial mass-spectrum appears similar to that derived for cores detected in SFCs (see e.g., Motte, André, & Neri 1998;Nutter & Ward-Thompson 2007;Enoch et al 2008;André et al 2011), and is very well approximated by a power-law at the high-mass end. Using the peaks in respective histograms for M clump and L clump , the condition…”

Section: Diagnostic Properties Of Clumpssupporting

confidence: 73%

Formation of Prestellar Cores via Non-Isothermal Gas Fragmentation

Anathpindika

2015

Publ. Astron. Soc. Aust.

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Sheet-like clouds are common in turbulent gas and perhaps form via collisions between turbulent gas flows. Having examined the evolution of an isothermal shocked slab in an earlier contribution, in this work we follow the evolution of a sheet-like cloud confined by (thermal) pressure and gas in it is allowed to cool. The extant purpose of this endeavour is to study the early phases of core-formation. The observed evolution of this cloud supports the conjecture that molecular clouds themselves are three-phase media (comprising viz. a stable cold and warm medium, and a third thermally unstable medium), though it appears, clouds may evolve in this manner irrespective of whether they are gravitationally bound. We report, this sheet fragments initially due to the growth of the thermal instability (TI) and some fragments are elongated, filament-like. Subsequently, relatively large fragments become gravitationally unstable and sub-fragment into smaller cores. The formation of cores appears to be a three stage process: first, growth of the TI leads to rapid fragmentation of the slab; second, relatively small fragments acquire mass via gas-accretion and/or merger and third, sufficiently massive fragments become susceptible to the gravitational instability and sub-fragment to form smaller cores. We investigate typical properties of clumps (and smaller cores) resulting from this fragmentation process. Findings of this work support the suggestion that the weak velocity field usually observed in dense clumps and smaller cores is likely seeded by the growth of dynamic instabilities. Simulations were performed using the smooth particle hydrodynamics algorithm.

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Section: Diagnostic Properties Of Clumpssupporting

confidence: 73%

Formation of Prestellar Cores via Non-Isothermal Gas Fragmentation

Anathpindika

2015

Publ. Astron. Soc. Aust.

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“…Although B1-E does not appear filamentary, there is ample material from which dense cores may form. With higher resolution data, André et al (2011) found a threshold column density of 7 × 10 21 cm −2 for dense structures to form in Aquila via thermal instabilities along a filament at 10 K.…”

Section: Sed Fitting To Herschel Datamentioning

confidence: 98%

Herschelobservations of a potential core-forming clump: Perseus B1-E

Sadavoy

Francesco

André

et al. 2012

A&A

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We present continuum observations of the Perseus B1-E region from the Herschel Gould Belt Survey. These Herschel data reveal a loose grouping of substructures at 160−500 μm not seen in previous submillimetre observations. We measure temperature and column density from these data and select the nine densest and coolest substructures for follow-up spectral line observations with the Green Bank Telescope. We find that the B1-E clump has a mass of ∼100 M and appears to be gravitationally bound. Furthermore, of the nine substructures examined here, one substructure (B1-E2) appears to be itself bound. The substructures are typically less than a Jeans length from their nearest neighbour and thus, may interact on a timescale of ∼1 Myr. We propose that B1-E may be forming a first generation of dense cores, which could provide important constraints on the initial conditions of prestellar core formation. Our results suggest that B1-E may be influenced by a strong, localized magnetic field, but further observations are still required.

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“…These results suggest that the CMF from the filamentary structures resembles the stellar IMF which is consistent with the gravo-turbulent scenario (see Motte et al 1998;André et al 2010). However, because prestellar cores are primarily found inside dense self-gravitating filaments, the Herschel results on nearby clouds suggest that the peak of the pre-stellar CMF may result from the pure gravitational fragmentation of filaments, independently of the cloud PDF (see André et al 2010André et al , 2011. A detailed analysis of the data is therefore needed to fully characterize the CMF/IMF relationship (e.g., environmental effects on the M * /M core conversion) and also to determine precisely the role of the turbulence, gravity, and feedback in the PDF/CMF relationship.…”

Section: Pre-existing Versus Triggered Dense Structuresmentioning

confidence: 99%

Ionization compression impact on dense gas distribution and star formation

Tremblin

Schneider

Minier

et al. 2014

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Aims. Ionization feedback should impact the probability distribution function (PDF) of the column density of cold dust around the ionized gas. We aim to quantify this effect and discuss its potential link to the core and initial mass function (CMF/IMF). Methods. We used Herschel column density maps of several regions observed within the HOBYS key program in a systematic way: M 16, the Rosette and Vela C molecular clouds, and the RCW 120 H ii region. We computed the PDFs in concentric disks around the main ionizing sources, determined their properties, and discuss the effect of ionization pressure on the distribution of the column density. Results. We fitted the column density PDFs of all clouds with two lognormal distributions, since they present a "double-peak" or an enlarged shape in the PDF. Our interpretation is that the lowest part of the column density distribution describes the turbulent molecular gas, while the second peak corresponds to a compression zone induced by the expansion of the ionized gas into the turbulent molecular cloud. Such a double peak is not visible for all clouds associated with ionization fronts, but it depends on the relative importance of ionization pressure and turbulent ram pressure. A power-law tail is present for higher column densities, which are generally ascribed to the effect of gravity. The condensations at the edge of the ionized gas have a steep compressed radial profile, sometimes recognizable in the flattening of the power-law tail. This could lead to an unambiguous criterion that is able to disentangle triggered star formation from pre-existing star formation. Conclusions. In the context of the gravo-turbulent scenario for the origin of the CMF/IMF, the double-peaked or enlarged shape of the PDF may affect the formation of objects at both the low-mass and the high-mass ends of the CMF/IMF. In particular, a broader PDF is required by the gravo-turbulent scenario to fit the IMF properly with a reasonable initial Mach number for the molecular cloud. Since other physical processes (e.g., the equation of state and the variations among the core properties) have already been said to broaden the PDF, the relative importance of the different effects remains an open question.

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Origin of the prestellar core mass function and link to the IMF – Herschel first results

Cited by 10 publications

References 38 publications

Formation of Prestellar Cores via Non-Isothermal Gas Fragmentation

Formation of Prestellar Cores via Non-Isothermal Gas Fragmentation

Herschelobservations of a potential core-forming clump: Perseus B1-E

Ionization compression impact on dense gas distribution and star formation

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