Prestellar and protostellar cores in Ori B9

Abstract

The aims of this study are to determine the properties and spatial distribution of dense cores in Ori B9, and to estimate their ages and dynamical timescales. The cloud was mapped in the 870 micron continuum with APEX/LABOCA, and selected positions were observed in the lines of N2H+ and N2D+ using IRAM-30m. These were used together with our previous H2D+ observations. Moreover, archival FIR Spitzer/MIPS maps were combined with the LABOCA map to distinguish between pre- and protostellar cores, and to estimate the evolutionary stages of protostars. Twelve dense cores were detected at 870 micron 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 pre- and protostellar cores. Two of the submm sources, which we call SMM 3 and SMM 4, are previously unknown Class 0 candidates. We found a moderate degree of deuteration in N2H+ (0.03-0.04). There is, furthermore, evidence for N2H+ depletion in the core SMM 4. 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. The distribution and masses of dense cores in Ori B9 are similar to those observed in more active regions in Orion, where the statistical core properties have been explained by turbulent fragmentation. The 50/50 proportions of pre- and protostellar cores suggest that duration of the prestellar phase is comparable to the free-fall time. This timescale can be questioned, however, on the basis of chemical data on the IRAS 05405-0117 region. A possible explanation is that this survey samples only the densest, i.e., dynamically most advanced cores.

17 pages, 8 figures, 9 tables. Revised version accepted for publication in A&A (Figs. 1, 3, and 7 revised, minor revisions in Sect. 5.2, updated reference information)

References in corpus (29)

• The Mass Distribution and Lifetime of Prestellar Cores in Perseus, Serpens, and Ophiuchus
• Observing the gas temperature drop in the high-density nucleus of L 1544
• Star formation in Perseus - V. Outflows detected by HARP
• Molecular Evolution and Star Formation: From Prestellar Cores to Protostellar Cores
• Magnetic Fields in Dark Cloud Cores: Arecibo OH Zeeman Observations
• A SCUBA survey of Orion, the low-mass end of the core mass function
• On the internal structure of starless cores. II. A molecular survey of L1498 and L1517B
• Comparing Star Formation on Large Scales in the c2d Legacy Clouds: Bolocam 1.1 mm Dust Continuum Surveys of Serpens, Perseus, and Ophiuchus
• The importance of the ortho:para H2 ratio for the deuteration of molecules during pre-protostellar collapse
• Survey of ortho-H2D+(1_{1,0}-1_{1,1}) in dense cloud cores
• Depletion and low gas temperature in the L183 prestellar core : the N2H+ - N2D+ tool
• The N2D+/N2H+ ratio as an evolutionary tracer of Class 0 protostars
• Dynamics of Dense Cores in the Perseus Molecular Cloud
• On the frequency of N2H+ and N2D+
• A highly-collimated SiO jet in the HH212 protostellar outflow
• PdBI sub-arcsecond study of the SiO microjet in HH212 - Origin and collimation of Class 0 jets
• Searching for massive pre--stellar cores through observations of N2H+ and N2D+
• HH 212: SMA Observations of a Remarkable Protostellar Jet
• The Excitation of N${}_2$H${}^{+}$ in Interstellar Molecular Clouds. I - Models
• The abundances of nitrogen-containing molecules during pre-protostellar collapse
• The relationship between the prestellar core mass function and the stellar initial mass function
• The initial conditions of star formation VIII: an observational study of the Ophiuchus cloud L1688 and implications for the prestellar core mass function
• TMC-1C: an accreting starless core
• ATCA and Spitzer Observations of the Binary Protostellar Systems CG30 and BHR71
• On the Evolution of the Dense Core Mass Function
• Star formation in a clustered environment around the UCHII region in IRAS 20293+3952
• Statistics of Core Lifetimes in Numerical Simulations of Turbulent, Magnetically Supercritical Molecular Clouds
• Highly deuterated pre-stellar cores in a high-mass star formation region
• Detection of H2D+ in a massive prestellar core in Orion B

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• HCN emission from translucent gas and UV-illuminated cloud edges revealed by wide-field IRAM 30m maps of Orion B GMC: Revisiting its role as tracer of the dense gas reservoir for star formation
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• Protostellar classification using supervised machine learning algorithms
• The APEX Large CO Heterodyne Orion Legacy Survey (ALCOHOLS). I. Survey overview
• APEX observations of ortho-H${}_2$D${}^{+}$ towards dense cores in the Orion B9 filament
• Ion and neutral molecules in the W43-MM1(G30.79 FIR 10) infalling clump
• Gas kinematics around filamentary structures in the Orion B cloud
• Deuterated species in extragalactic star-forming regions
• Dynamics, CO depletion, and deuterium fractionation of the dense condensations within the fragmented prestellar core Orion B9-SMM 6
• 13CO and C18O J=2-1 mapping of the environment of the Class 0 protostellar core SMM 3 in Orion B9
• SABOCA 350-micron and LABOCA 870-micron dust continuum imaging of IRAS 05399-0121: mapping the dust properties of a pre- and protostellar core system
• Characterising the physical and chemical properties of a young Class 0 protostellar core embedded in the Orion B9 filament
• ArTéMiS imaging of the filamentary infrared dark clouds G1.75-0.08 and G11.36+0.80: Dust-based physical properties of the clouds and their clumps