Probing the Evolutionary Status of Starless Cores through N2H+and N2D+Observations

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

doi:10.1086/426472

Cited by 391 publications

(771 citation statements)

References 69 publications

Supporting

102

Mentioning

640

Contrasting

Unclassified

Order By: Relevance

“…The SABOCA peaks appeared to systematically lie southeast from the LABOCA peak positions. The difference in angular resolution between SABOCA and LABOCA data did not of deuteration, or the N(N 2 D + )/N(N 2 H + ) column density ratio, towards selected positions and found the values in the range 0.03-0.04, comparable to those seen in other low-mass starforming regions (e.g., Crapsi et al 2005;Emprechtinger et al 2009;Friesen et al 2010b). Taking advantage of the H 2 D + data from Harju et al (2006), the ionisation degree and the cosmicray ionisation rate of H 2 towards the same target positions were estimated to be x(e) ∼ 10 −7 and ζ H 2 ∼ 1−2 × 10 −16 s −1 , respectively.…”

Section: Introductionmentioning

confidence: 68%

See 1 more Smart Citation

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

Miettinen

Harju

Haikala

et al. 2012

A&A

View full text Add to dashboard Cite

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.

show abstract

Section: Introductionmentioning

confidence: 68%

“…For N 2 D + , we used as T ex the values obtained hand, N 2 D + emission has been found to trace dust emission very well in low-mass dense cores (e.g., Crapsi et al 2005). Therefore, the assumption of unity beam filling factor is reasonable.…”

Section: Molecular Column Densities and Fractional Abundancesmentioning

confidence: 99%

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

Miettinen

Harju

Haikala

et al. 2012

A&A

View full text Add to dashboard Cite

show abstract

“…Caselli et al 2002;Bacmann et al 2003;Millar 2005;Crapsi et al 2005;Chen et al 2011). Therefore, we studied the influence of varying the depletion percentage on the fractional abundances of the species in hot corinos and cores.…”

Section: Impact Of Varying the Depletion Efficiencymentioning

confidence: 99%

Deuterium chemistry of dense gas in the vicinity of low-mass and massive star-forming regions

Awad

Viti

Bayet

et al. 2014

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

The standard interstellar ratio of deuterium to hydrogen (D/H) atoms is ∼ 1.5×10 −5 . However, the deuterium fractionation is in fact found to be enhanced, to different degrees, in cold, dark cores, hot cores around massive star forming regions, lukewarm cores, and warm cores (hereafter, hot corinos) around low-mass star forming regions. In this paper, we investigate the overall differences in the deuterium chemistry between hot cores and hot corinos. We have modelled the chemistry of dense gas around low-mass and massive star forming regions using a gas-grain chemical model. We investigate the influence of varying the core density, the depletion efficiency of gaseous species on to dust grains, the collapse mode and the final mass of the protostar on the chemical evolution of star forming regions. We find that the deuterium chemistry is, in general, most sensitive to variations of the depletion efficiency on to grain surfaces, in agreement with observations. In addition, the results showed that the chemistry is more sensitive to changes in the final density of the collapsing core in hot cores than in hot corinos. Finally, we find that ratios of deuterated sulphur bearing species in dense gas around hot cores and corinos may be good evolutionary indicators in a similar way as their non deuterated counterparts.

show abstract

“…Since both transitions have similar critical densities, we fix the N2D + (3-2) excitation temperature to the value from the N2H + (3-2) fit. This procedure is similar to the one followed by Crapsi et al (2005) and Pineda & Teixeira (2013). For N2D + (3-2), in all cases the optical depth obtained from the hyperfine structure fit is lower than 1.…”

Section: Resultsmentioning

confidence: 91%

“…The deuterated species preferentially trace the coldest parts of dense cores (i.e. single star progenitors), and have been shown to be an important tool to determine the degree of evolution in low-mass cores (Caselli et al 2002;Crapsi et al 2005;Emprechtinger et al 2009) and high-mass cores (Fontani et al 2011;Pillai et al 2012). Chemical models (e.g.…”

Section: Introductionmentioning

confidence: 99%

Deuteration in infrared dark clouds

Lackington

Fuller

Pineda

et al. 2015

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

Much of the dense gas in molecular clouds has a filamentary structure but the detailed structure and evolution of this gas is poorly known. We have observed 54 cores in infrared dark clouds (IRDCs) using N 2 H + (1-0) and (3-2) to determine the kinematics of the densest material, where stars will form. We also observed N 2 D + (3-2) towards 29 of the brightest peaks to analyse the level of deuteration which is an excellent probe of the quiescent of the early stages of star formation. There were 13 detections of N 2 D + (3-2). This is one of the largest samples of IRDCs yet observed in these species. The deuteration ratio in these sources ranges between 0.003 and 0.14. For most of the sources the material traced by N 2 D + and N 2 H + (3-2) still has significant turbulent motions, however three objects show subthermal N 2 D + velocity dispersion. Surprisingly the presence or absence of an embedded 70µm source shows no correlation with the detection of N 2 D + (3-2), nor does it correlate with any change in velocity dispersion or excitation temperature. Comparison with recent models of deuteration suggest evolutionary time-scales of these regions of several freefall times or less.

show abstract

Probing the Evolutionary Status of Starless Cores through N₂H⁺and N₂D⁺Observations

Cited by 391 publications

References 69 publications

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

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

Deuterium chemistry of dense gas in the vicinity of low-mass and massive star-forming regions

Deuteration in infrared dark clouds

Contact Info

Product

Resources

About