The initial conditions of high-mass star formation: radiative transfer models of IRDCs seen in the<i>Herschel</i>Hi-GAL survey

Wilcock, L. A.; Kirk, J. M.; Stamatellos, Dimitris; Ward-Thompson, Derek; Whitworth, Anthony Peter; Battersby, Cara; Brunt, Christopher M.; Fuller, G. A.; Griffin, M.; Molinari, S.; Martín, P. G.; Mottram, J. C.; Peretto, N.; Plume, R.; Smith, H. A.

doi:10.1051/0004-6361/201015488

Cited by 17 publications

(21 citation statements)

References 30 publications

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“…density was 10 6−7 cm −3 over the integrated radius range between 200 AU and 0.1 pc, which are similar to the values used in recent radiative transfer calculations of IRDC cores (Stamatellos et al 2010;Wilcock et al 2011). At the assumed distance, 4 kpc, the core would be 10 in diameter, which would be unresolved in our PACS 160 μm observations.…”

Section: The Source Of Emission At Pacs Wavelengthssupporting

confidence: 82%

The Earliest Phases of Star Formation (EPoS): aHerschelkey program

Ragan

Henning

Krause

et al. 2012

A&A

125

201

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Context. Stars are born deeply embedded in molecular clouds. In the earliest embedded phases, protostars emit the bulk of their radiation in the far-infrared wavelength range, where Herschel is perfectly suited to probe at high angular resolution and dynamic range. In the high-mass regime, the birthplaces of protostars are thought to be in the high-density structures known as infrareddark clouds (IRDCs). While massive IRDCs are believed to have the right conditions to give rise to massive stars and clusters, the evolutionary sequence of this process is not well-characterized. Aims. As part of the Earliest Phases of Star formation (EPoS) Herschel guaranteed time key program, we isolate the embedded structures within IRDCs and other cold, massive molecular clouds. We present the full sample of 45 high-mass regions which were mapped at PACS 70, 100, and 160 μm and SPIRE 250, 350, and 500 μm. In the present paper, we characterize a population of cores which appear in the PACS bands and place them into context with their host molecular cloud and investigate their evolutionary stage. Methods. We construct spectral energy distributions (SEDs) of 496 cores which appear in all PACS bands, 34% of which lack counterparts at 24 μm. From single-temperature modified blackbody fits of the SEDs, we derive the temperature, luminosity, and mass of each core. These properties predominantly reflect the conditions in the cold, outer regions. Taking into account optical depth effects and performing simple radiative transfer models, we explore the origin of emission at PACS wavelengths. Results. The core population has a median temperature of 20 K and has masses and luminosities that span four to five orders of magnitude. Cores with a counterpart at 24 μm are warmer and bluer on average than cores without a 24 μm counterpart. We conclude that cores bright at 24 μm are on average more advanced in their evolution, where a central protostar(s) have heated the outer bulk of the core, than 24 μm-dark cores. The 24 μm emission itself can arise in instances where our line of sight aligns with an exposed part of the warm inner core. About 10% of the total cloud mass is found in a given cloud's core population. We uncover over 300 further candidate cores which are dark until 100 μm. These are possibly starless objects, and further observations will help us determine the nature of these very cold cores.

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Section: The Source Of Emission At Pacs Wavelengthssupporting

confidence: 82%

The Earliest Phases of Star Formation (EPoS): aHerschelkey program

Ragan

Henning

Krause

et al. 2012

A&A

125

201

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“…Similar examples of fragmentation within larger cores to form smaller ones has been identified in for instance, the Serpens North (Duarte-Cabral et al 2010), or within a number of IRDCs (e.g. Wilcock et al 2011Wilcock et al , 2012. t=0.01 Myr t=0.2 Myr t=0.9 Myr t=1.9 Myrs t=2.5 Myrs Figure 13.…”

Section: Stability Of Filaments In Star-forming Clouds and The Formatsupporting

confidence: 61%

Stability of Filaments in Star-Forming Clouds and the Formation of Prestellar Cores in Them

Anathpindika

Freundlich

2015

Publ. Astron. Soc. Aust.

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The exact process(es) that generate(s) dense filaments which then form prestellar cores within them is unclear. Here we study the formation of a dense filament using a relatively simple set-up of a pressure-confined, uniform-density cylinder. We examine if its propensity to form a dense filament and further, to the formation of prestellar cores along this filament, bears on the gravitational state of the initial volume of gas. We report a radial collapse leading to the formation of a dense filamentary cloud is likely when the initial volume of gas is at least critically stable (characterised by the approximate equality between the mass line-density for this volume and its maximum value). Though self-gravitating, this volume of gas, however, is not seen to be in free-fall. This post-collapse filament then fragments along its length due to the growth of a Jeans-like instability to form prestellar cores. We suggest dense filaments in typical star-forming clouds classified as gravitationally super-critical under the assumption of: (i) isothermality when in fact, they are not, and (ii) extended radial profiles as against pressure-truncated, that significantly over-estimates their mass line-density, are unlikely to experience gravitational free-fall. The radial density and temperature profile derived for this post-collapse filament is consistent with that deduced for typical filamentary clouds mapped in recent surveys of nearby star-forming regions.

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“…Finally, we observe that even the densest clumps (with high column densities) cannot reach temperature lower than 7 K. This is in excellent agreement with recent observations of cold cores using Herschel (e.g., Wilcock et al 2011;). …”

Section: Column Densitiessupporting

confidence: 92%

Planckearly results. XXIII. The first all-sky survey of Galactic cold clumps

Ade¹,

Aghanim²,

Arnaud³

et al. 2011

A&A

Self Cite

154

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We present the statistical properties of the Cold Clump Catalogue of Planck Objects (C3PO), the first all-sky catalogue of cold objects, in terms of their spatial distribution, dust temperature, distance, mass, and morphology. We have combined Planck and IRAS data to extract 10 342 cold sources that stand out against a warmer environment. The sources are distributed over the whole sky, including in the Galactic plane, despite the confusion, and up to high latitudes (>30 • ). We find a strong spatial correlation of these sources with ancillary data tracing Galactic molecular structures and infrared dark clouds where the latter have been catalogued. These cold clumps are not isolated but clustered in groups. Dust temperature and emissivity spectral index values are derived from their spectral energy distributions using both Planck and IRAS data. The temperatures range from 7 K to 19 K, with a distribution peaking around 13 K. The data are inconsistent with a constant value of the associated spectral index β over the whole temperature range: β varies from 1.4 to 2.8, with a mean value around 2.1. Distances are obtained for approximately one third of the objects. Most of the detections lie within 2 kpc of the Sun, but more distant sources are also detected, out to 7 kpc. The mass estimates inferred from dust emission range from 0.4 M to 2.4 × 10 5 M . Their physical properties show that these cold sources trace a broad range of objects, from low-mass dense cores to giant molecular clouds, hence the "cold clump" terminology. This first statistical analysis of the C3PO reveals at least two colder populations of special interest with temperatures in the range 7 to 12 K: cores that mostly lie close to the Sun; and massive cold clumps located in the inner Galaxy. We also describe the statistics of the early cold core (ECC) sample that is a subset of the C3PO, containing only the 915 most reliable detections. The ECC is delivered as a part of the Planck Early Release Compact Source Catalogue (ERCSC).

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The initial conditions of high-mass star formation: radiative transfer models of IRDCs seen in theHerschelHi-GAL survey

Cited by 17 publications

References 30 publications

The Earliest Phases of Star Formation (EPoS): aHerschelkey program

The Earliest Phases of Star Formation (EPoS): aHerschelkey program

Stability of Filaments in Star-Forming Clouds and the Formation of Prestellar Cores in Them

Planckearly results. XXIII. The first all-sky survey of Galactic cold clumps

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