Observations of L1521F: A highly evolved starless core

Crapsi, A.; Caselli, P.; Walmsley, C. M.; Tafalla, M.; Lee, C. W.; Bourke, Tyler L.; Myers, Philip C.

doi:10.1051/0004-6361:20035915

Cited by 92 publications

(181 citation statements)

References 65 publications

(163 reference statements)

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“…A low CO depletion factor of 1.4 close to N 2 H + peak Ori B9 N (see Sect. 4.4) is consistent with the R deut value of Ori B9 N (e.g., Crapsi et al 2004; see also …”

Section: Deuterium Fractionation and Depletion In The Iras 05405-0117supporting

confidence: 85%

“…The corresponding CO depletion factor, f D , is only 1.4 with respect to the often adopted fractional abundance from Frerking et al (1982) 10 . The small value of R deut is consistent with a low CO depletion factor (e.g., Crapsi et al 2004).…”

Section: Ionization Degree and Cosmic-ray Ionization Ratesupporting

confidence: 60%

“…4.1 and 5.1) can represent an extreme case of depletion, where N 2 H + has also disappeared from the gas phase due to freeze-out on to the dust grain surfaces. There is evidence of N 2 H + depletion in the centres of chemically evolved cores, such as B68 (Bergin et al 2002), L1544 (Caselli et al 2002a), L1512 (Lee et al 2003), and L1521F (Crapsi et al 2004). Example of the N 2 H + depletion toward Class 0 source is IRAM 04191+1522 in Taurus (Belloche & André 2004).…”

Section: Evidence Of a N 2 H + "Hole" And Chemical Differentiationmentioning

confidence: 99%

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Prestellar and protostellar cores in Orion B9

Miettinen

Harju

Haikala

et al. 2009

A&A

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Context. Dense molecular cores are studied to gain insight into the processes causing clouds to fragment and form stars. In this study, we concentrate on a region that is assumed to represent an early stage of clustered star-formation in a giant molecular cloud. Aims. We aim to determine the properties and spatial distribution of dense cores in the relatively quiescent Ori B9 cloud, and to estimate their ages and dynamical timescales. Methods. The cloud was mapped in the 870 μm continuum with APEX/LABOCA, and selected positions were observed in the lines of N 2 H + and N 2 D + using IRAM-30 m. These were used together with our previous H 2 D + observations to derive the degree of deuteration and some other chemical characteristics. Archival far-infrared Spitzer/MIPS maps were combined with the LABOCA map to distinguish between prestellar and protostellar cores, and to estimate the evolutionary stages of protostars. Results. Twelve dense cores were detected at 870 μm continuum in the Ori B9 cloud. The submm cores constitute ∼4% of the total mass of the Ori B9 region. There is an equal number of prestellar and protostellar cores. Two of the submm sources, which we call SMM 3 and SMM 4, are previously unknown Class 0 candidates. There is a high likelihood of the core masses and mutual separations representing the same distributions as observed in other parts of Orion. We found a moderate degree of deuteration in N 2 H + (0.03-0.04). There is, furthermore, evidence of N 2 H + depletion in the core SMM 4. These features suggest that the cores have reached chemical maturity. We derive a relatively high degree of ionization (∼10 −7 ) in the clump associated with IRAS 05405-0117. The ambipolar diffusion timescales for two of the cores are ∼70-100 times longer than the free-fall time.Conclusions. The distribution and masses of dense cores in Ori B9 are similar to those observed in more active regions of Orion, where the statistical core properties have been explained by turbulent fragmentation. The 50/50 proportions of prestellar and protostellar cores imply that the duration of the prestellar phase is comparable to the free-fall time. However, on the basis of chemical data of the IRAS 05405-0117 region, this timescale could be questioned. A possible explanation is that this survey samples only the densest, i.e., dynamically most advanced cores.

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“…A low CO depletion factor of 1.4 close to N 2 H + peak Ori B9 N (see Sect. 4.4) is consistent with the R deut value of Ori B9 N (e.g., Crapsi et al 2004; see also …”

Section: Deuterium Fractionation and Depletion In The Iras 05405-0117supporting

confidence: 85%

Section: Ionization Degree and Cosmic-ray Ionization Ratesupporting

confidence: 60%

Section: Evidence Of a N 2 H + "Hole" And Chemical Differentiationmentioning

confidence: 99%

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Prestellar and protostellar cores in Orion B9

Miettinen

Harju

Haikala

et al. 2009

A&A

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“…In this case, the very high R D (N 2 H + ) value would be remnant of the earlier COdepleted phase, and not yet affected by the gas-phase CO which destroys N 2 H + and N 2 D + . An opposite situation was found by Crapsi et al (2004) towards the chemically evolved dense core L1521F which harbours a very low luminosity object or VeLLO (Bourke et al 2006), where f D ∼ 15 but R D (N 2 H + ) is only ∼0.1. For comparison, Crapsi et al (2005) derived the values of R D (N 2 H + ) in the range 0.02−0.44 for their sample of starless cores, and Daniel et al (2007) derived comparable values of R D (N 2 H + ) ∼ 0.07−0.53 towards another sample of starless cores.…”

Section: Depletion and Deuterationmentioning

confidence: 85%

A (sub)millimetre study of dense cores in Orion B9

Miettinen

Harju

Haikala

et al. 2012

A&A

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Context. Studies of dense molecular-cloud cores at (sub)millimetre wavelengths are needed to understand the early stages of star formation. Aims. We aim to further constrain the properties and evolutionary stages of dense cores in Orion B9. The prime objective of this study is to examine the dust emission of the cores near the peak of their spectral energy distributions, and to determine the degrees of CO depletion, deuterium fractionation, and ionisation. Methods. The central part of Orion B9 was mapped at 350 μm with APEX/SABOCA. A sample of nine cores in the region were observed in C 17 O(2−1), H 13 CO + (4−3) (towards 3 sources), DCO + (4−3), N 2 H + (3−2), and N 2 D + (3−2) with APEX/SHFI. These data are used in conjunction with our previous APEX/LABOCA 870-μm dust continuum data. Results. All the LABOCA cores in the region covered by our SABOCA map were detected at 350 μm. The strongest 350 μm emission is seen towards the Class 0 candidate SMM 3. Many of the LABOCA cores show evidence of substructure in the higher-resolution SABOCA image. In particular, we report on the discovery of multiple very low-mass condensations in the prestellar core SMM 6. Based on the 350-to-870 μm flux density ratios, we determine dust temperatures of T dust 7.9−10.8 K, and dust emissivity indices of β ∼ 0.5−1.8. The CO depletion factors are in the range f D ∼ 1.6−10.8. The degree of deuteration in N 2 H + is 0.04−0.99, where the highest value (seen towards the prestellar core SMM 1) is, to our knowledge, the most extreme level of N 2 H + deuteration reported so far. The level of HCO + deuteration is about 1-2%. The fractional ionisation and cosmic-ray ionisation rate of H 2 could be determined only towards two sources with the lower limits of ∼2−6 × 10 −8 and ∼2.6 × 10 −17 −4.8 × 10 −16 s −1 , respectively. We also detected D 2 CO towards two sources. Conclusions. The detected protostellar cores are classified as Class 0 objects, in agreement with our previous SED results. The detection of subcondensations within SMM 6 shows that core fragmentation can already take place during the prestellar phase. The origin of this substructure is likely caused by thermal Jeans fragmentation of the elongated parent core. Varying levels of f D and deuteration among the cores suggest that they are evolving chemically at different rates. A low f D value and the presence of gas-phase D 2 CO in SMM 1 suggest that the core chemistry is affected by the nearby outflow. The very high N 2 H + deuteration in SMM 1 is likely to be remnant of the earlier CO-depleted phase.

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“…Besides the high central density and infall asymmetry, L1521F also shows molecular depletion and enhanced deuterium fractionation (Crapsi et al 2004;Shinnaga et al 2004). Crapsi et al (2004) explain this by suggesting that L1521F is less chemically evolved and has a molecular hole of radius < 2000 AU.…”

Section: L1521fmentioning

confidence: 92%

Far-infrared/submillimetre properties of pre-stellar cores L1521E, L1521F and L1689B as revealed by theHerschelSPIRE instrument – I. Central positions

Makiwa

Naylor

Wiel

et al. 2016

Mon. Not. R. Astron. Soc.

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Dust grains play a key role in the physics of star-forming regions, even though they constitute only ∼1 % of the mass of the interstellar medium. The derivation of accurate dust parameters such as temperature (T d ), emissivity spectral index (β) and column density requires broadband continuum observations at far-infrared wavelengths. We present Herschel-SPIRE Fourier Transform Spectrometer (FTS) measurements of three starless cores: L1521E, L1521F and L1689B, covering wavelengths between 194 and 671 µm. This paper is the first to use our recently updated SPIRE-FTS intensity calibration, yielding a direct match with SPIRE photometer measurements of extended sources. In addition, we carefully assess the validity of calibration schemes depending on source extent and on the strength of background emission. The broadband far-infrared spectra for all three sources peak near 250 µm. Our observations therefore provide much tighter constraints on the spectral energy distribution (SED) shape than measurements that do not probe the SED peak. The spectra are fitted using modified blackbody functions, allowing both T d and β to vary as free parameters. This yields T d of 9.8±0.2 K, 15.6±0.5 K and 10.9±0.2 K and corresponding β of 2.6∓0.9, 0.8∓0.1 and 2.4∓0.8 for L1521E, L1521F and L1689B respectively. The derived core masses are 1.0±0.1, 0.10±0.01 and 0.49±0.05 M , respectively. The core mass/Jeans mass ratios for L1521E and L1689B exceed unity indicating that they are unstable to gravitational collapse, and thus prestellar cores. By comparison, the elevated temperature and gravitational stability of L1521F support previous arguments that this source is more evolved and likely a protostar.

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Observations of L1521F: A highly evolved starless core

Cited by 92 publications

References 65 publications

Prestellar and protostellar cores in Orion B9

Prestellar and protostellar cores in Orion B9

A (sub)millimetre study of dense cores in Orion B9

Far-infrared/submillimetre properties of pre-stellar cores L1521E, L1521F and L1689B as revealed by theHerschelSPIRE instrument – I. Central positions

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