Very Cold and Massive Cores near ISOSS J18364−0221: Implications for the Initial Conditions of High‐Mass Star Formation

Birkmann, Stephan M.; Krause, O.; Lemke, D.

doi:10.1086/498259

Cited by 16 publications

(45 citation statements)

References 26 publications

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“…1, there are two known dense clumps (ISOSS J18364-0221 SMM1/SMM2) with >30 km s −1 LSR velocities from molecular line measurements (Birkmann et al 2006). Their LSR velocities correspond to a kinematical distance of ∼2.2 kpc.…”

Section: Post-selection Checksmentioning

confidence: 94%

A census of dense cores in the Aquila cloud complex: SPIRE/PACS observations from theHerschelGould Belt survey

Könyves

André

Men’shchikov

et al. 2015

A&A

394

471

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We present and discuss the results of the Herschel Gould Belt survey (HGBS) observations in an ∼11 deg 2 area of the Aquila molecular cloud complex at d ∼ 260 pc, imaged with the SPIRE and PACS photometric cameras in parallel mode from 70 μm to 500 μm. Using the multi-scale, multi-wavelength source extraction algorithm getsources, we identify a complete sample of starless dense cores and embedded (Class 0-I) protostars in this region, and analyze their global properties and spatial distributions. We find a total of 651 starless cores, ∼60% ± 10% of which are gravitationally bound prestellar cores, and they will likely form stars in the future. We also detect 58 protostellar cores. The core mass function (CMF) derived for the large population of prestellar cores is very similar in shape to the stellar initial mass function (IMF), confirming earlier findings on a much stronger statistical basis and supporting the view that there is a close physical link between the stellar IMF and the prestellar CMF. The global shift in mass scale observed between the CMF and the IMF is consistent with a typical star formation efficiency of ∼40% at the level of an individual core. By comparing the numbers of starless cores in various density bins to the number of young stellar objects (YSOs), we estimate that the lifetime of prestellar cores is ∼1 Myr, which is typically ∼4 times longer than the core free-fall time, and that it decreases with average core density. We find a strong correlation between the spatial distribution of prestellar cores and the densest filaments observed in the Aquila complex. About 90% of the Herschel-identified prestellar cores are located above a background column density corresponding to A V ∼ 7, and ∼75% of them lie within filamentary structures with supercritical masses per unit length > ∼ 16 M /pc. These findings support a picture wherein the cores making up the peak of the CMF (and probably responsible for the base of the IMF) result primarily from the gravitational fragmentation of marginally supercritical filaments. Given that filaments appear to dominate the mass budget of dense gas at A V > 7, our findings also suggest that the physics of prestellar core formation within filaments is responsible for a characteristic "efficiency" SFR/M dense ∼ 5 +2 −2 × 10 −8 yr −1 for the star formation process in dense gas.

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Section: Post-selection Checksmentioning

confidence: 94%

A census of dense cores in the Aquila cloud complex: SPIRE/PACS observations from theHerschelGould Belt survey

Könyves

André

Men’shchikov

et al. 2015

A&A

394

471

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“…Submillimetre and/or millimetre dust continuum maps of our sources are published in the papers by Beuther et al (2002a Birkmann et al (2006;SCUBA 450 & 850 μm). For the sources I18102 MM1, I18182 MM2, and J18364 SMM1 we retrieved 850 μm dust continuum data from the JCMT/SCUBA archive (Di Francesco et al 2008) 5 .…”

Section: Archival Dust Continuum Datamentioning

confidence: 99%

“…Its CO(1−0) radial velocity of ∼33 km s −1 corresponds to a kinematic distance of ∼2.2 kpc according to the Brand & Blitz (1993) rotation curve (see Birkmann et al 2006). We recomputed this distance from the LSR velocity of C 17 O(2−1) (34.8 km s −1 ) because it is tracing higher density gas than the main CO isotopologue (similar radial velocity was obtained for the other detected transitions).…”

Section: Kinematic Distancesmentioning

confidence: 99%

“…For the source J18364 SMM1 we scaled the effective radius ≈0.2 pc reported by Birkmann et al (2006) using the revised distance (R eff = 0.23 pc), and used the total mass within the clump area.…”

Section: Clump Masses Radii and H 2 Column And Number Densitiesmentioning

confidence: 99%

“…We used the values of T kin and A134, page 10 of 23 ). In the case of J18364 SMM1, we give the SCUBA 850-μm flux density from Birkmann et al (2006).…”

Section: Molecular Column Densities and Fractional Abundancesmentioning

confidence: 99%

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Deuterium fractionation and the degree of ionisation in massive clumps within infrared dark clouds

Miettinen

Hennemann

Linz

2011

A&A

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Context. Massive clumps associated with infrared dark clouds (IRDCs) are promising targets for studying the earliest stages of highmass star and cluster formation. Aims. We aim to determine the degrees of CO depletion, deuterium fractionation, and ionisation in a sample of seven massive clumps associated with IRDCs. Methods. The APEX telescope was used to observe the C 17 O(2−1), H 13 CO + (3−2), DCO + (3−2), N 2 H + (3−2), and N 2 D + (3−2) transitions towards the clumps. The spectral line data were used in conjunction with the previously published and/or archival (sub)millimetre dust continuum observations of the sources. The data were used to derive the molecular column densities and fractional abundances for the analysis of deuterium fractionation and ionisation. Results. The CO molecules do not appear to be significantly depleted in the observed clumps. The DCO + /HCO + and N 2 D + /N 2 H + column density ratios are about 0.0002-0.014 and 0.002-0.028, respectively. The former ratio is found to decrease as a function of gas kinetic temperature. A simple chemical analysis suggests that the lower limit to the ionisation degree is in the range x(e) ∼ 10 −8 −10 −7 , whereas the estimated upper limits range from a few 10 −6 up to ∼10 −4 . Lower limits to x(e) imply that the cosmic-ray ionisation rate of H 2 lies between ζ H 2 ∼ 10 −17 −10 −15 s −1 . These are the first estimates of x(e) and ζ H 2 towards massive IRDCs reported so far. Some additional molecular transitions, mostly around 216 and 231 GHz, were detected towards all sources. In particular, IRDC 18102-1800 MM1 and IRDC 18151-1208 MM2 show relatively line-rich spectra. Some of these transitions might be assigned to complex organic molecules, although the line blending hampers the identification. The C 18 O(2−1) transition is frequently seen in the image band. Conclusions. The finding that CO is not depleted in the observed sources conforms to the fact that they show evidence of star formation activity, which is believed to release CO from the icy grain mantles back into the gas phase. The observed degree of deuteration is lower than in low-mass starless cores and protostellar envelopes. Decreasing deuteration with increasing temperature is likely to reflect the clump evolution. On the other hand, the association with young high-mass stars could enhance ζ H 2 and x(e) above the levels usually found in low-mass star-forming regions. On the scale probed by our observations, ambipolar diffusion cannot be a main driver of clump evolution unless it occurs on timescales 10 6 yr.

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Multiple low-turbulence starless cores associated with intermediate- to high-mass star formation

Beuther

Henning

2009

A&A

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Aims. Characterizing the gas and dust properties prior to and in the neighborhood of active intermediate-to high-mass star formation. Methods. Two Infrared Dark Clouds (IRDCs) -IRDC 19175-4 and IRDC 19175-5 -that are located in the vicinity of the luminous massive star-forming region IRAS 19175+1357, but that remain absorption features up to 70 μm wavelength, were observed with the Plateau de Bure Interferometer in the 3.23 mm dust continuum as well as the N 2 H + (1-0) and 13 CS(2-1) line emission. Results. While IRDC 19175-4 is clearly detected in the 3.23 mm continuum, the second source in the field, IRDC 19175-5, is only barely observable above the 3σ continuum detection threshold. However, the N 2 H + (1-0) observations reveal 17 separate sub-sources in the vicinity of the two IRDCs. Most of them exhibit low levels of turbulence (Δv ≤ 1 km s −1 ), indicating that the fragmentation process in these cores may be dominated by the interplay of thermal pressure and gravity, but not so much by turbulence. Combining the small line widths with the non-detection up to 70 μm and the absence of other signs of star formation activity, most of these 17 cores with masses between sub-solar to ∼10 M are likely still in a starless phase. The N 2 H + column density analysis indicates significant abundance variations between the cores. Furthermore, we find a large CS depletion factor of the order 100. Although the strongest line and continuum peak is close to virial equilibrium, its slightly broader line width compared to the other cores is consistent with it being in a contraction phase potentially at the verge of star formation. Based on the 3.23 mm upper limits, the other cores may be gravitationally stable or even transient structures. The relative peak velocities between neighboring cores are usually below 1 km s −1 , and we do not identify streaming motions along the filamentary structures. Average densities are between 10 5 and 10 6 cm −3 (one to two orders of magnitude larger than for example in the Pipe nebula) implying relatively small Jeans-lengths that are consistent with the observed core separations of the order 5000 AU. Environmental reasons potentially determining these values are discussed. Conclusions. These observations show that multiple low-to intermediate-mass low-turbulence starless cores can exist in the proximity of more turbulent active intermediate-to high-mass star-forming regions. While masses and levels of turbulence are consistent with low-mass starless core regions, other parameters like the densities or Jeans-lengths differ considerably. This may be due to environmental effects. The quest for high-mass starless cores prior to any star formation activity remains open.

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Very Cold and Massive Cores near ISOSS J18364−0221: Implications for the Initial Conditions of High‐Mass Star Formation

Cited by 16 publications

References 26 publications

A census of dense cores in the Aquila cloud complex: SPIRE/PACS observations from theHerschelGould Belt survey

A census of dense cores in the Aquila cloud complex: SPIRE/PACS observations from theHerschelGould Belt survey

Deuterium fractionation and the degree of ionisation in massive clumps within infrared dark clouds

Multiple low-turbulence starless cores associated with intermediate- to high-mass star formation

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