Ammonia Clumps in the Orion and Cepheus Clouds

Harju, J.; Walmsley, C. M.; Wouterloot, J. G. A.

doi:10.1007/978-94-011-3384-5_60

Cited by 104 publications

(210 citation statements)

References 8 publications

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“…The integrated NH 3 (1, 1) and (2, 2) intensity maps of the clump (see Appendix A in Harju et al 1993) show roughly the same morphology as the submm map. The NH 3 column densities toward IRAS 05405-0117, Ori B9 E, and Ori B9 N are 11.9±1.3×10 14 , 7.2±1.3×10 14 , and 9.7±4.6× 10 14 cm −2 , respectively.…”

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

confidence: 59%

“…For all the IRAS sources as well as for SMM 3 and SMM 4, we adopted the dust temperatures resulting from the SED fitting (see Table 6, Col. 4). For all the other sources, it was assumed that T d = 10 K. The assumed dust temperature of 10 K is justified by estimates derived from NH 3 (Harju et al 1993) and is commonly adopted for starless cores. The assumption that T d = T kin , where T kin is the gas kinetic temperature, is probably valid at densities n(H 2 ) > 10 5 cm −3 (Burke & Hollenbach 1983).…”

Section: Linear Sizes and Mass Estimates And Densitiesmentioning

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

confidence: 59%

Section: Linear Sizes and Mass Estimates And Densitiesmentioning

confidence: 99%

Prestellar and protostellar cores in Orion B9

Miettinen

Harju

Haikala

et al. 2009

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“…Interestingly, the line emission of all the species peaks towards the southeastern core, rather than towards I05399. Particularly their N 2 H + map appears very similar to that of NH 3 (Harju et al 1993), which might not be surprising given that both species are excellent tracers of the dense interstellar gas (e.g., Bergin & Langer 1997). By utilising the molecular ion data, Bergin et al (1999) constrained the fractional ionisation in I05399 to lie in the range 9.3 × 10 −8 < x(e) < 1.8 × 10 −7 , with the best-fit value being ∼1.3 × 10 −7 .…”

Section: Introductionmentioning

confidence: 73%

“…To our knowledge, the first millimetre dust continuum emission map of LBS 30 was made by Launhardt et al (1996). They used both the SEST 15-m and IRAM 30-m telescopes to image the 1.3-mm dust emission of LBS 30, and found a dust core associated with I05399 and a subcore southeast of it, resembling the morphology seen in the NH 3 map by Harju et al (1993). Assuming a distance of 400 pc and dust temperature of T dust = 30 K, Launhardt et al (1996) estimated the total mass of 1 In the present paper, we adopt a distance of 450 pc to the Orion giant molecular cloud (Genzel & Stutzki 1989).…”

Section: Introductionmentioning

confidence: 99%

SABOCA 350-μm and LABOCA 870-μm dust continuum imaging of IRAS 05399-0121: mapping the dust properties of a pre- and protostellar core system

Miettinen

Offner

2013

A&A

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Context. Thermal emission from dust provides a valuable tool for determining important physical properties of the dense structures within molecular clouds. Aims. We attempt to map the distributions of dust temperature and H 2 column density of IRAS 05399-0121/SMM 1, which is a dense double-core system in Orion B9. We also search for substructures within the cores through high-resolution submillimetre imaging. Methods. The source was mapped with APEX/SABOCA at 350 μm. We combined these data with our previous LABOCA 870-μm data. The spatial resolution of the new SABOCA image, ∼3400 AU, is about 2.6 times better than provided by LABOCA, and is therefore well-suited to our purposes. We also make use of the Spitzer infrared observations to characterise the star-formation activity in the source. Results. The filamentary source remains a double-core system on the 3400 AU scale probed here, and the projected separation between IRAS 05399 and SMM 1 is 0.14 pc. The temperature map reveals warm spots towards IRAS 05399 and the southeastern tip of the source. Both IRAS 05399 and SMM 1 stand out as peaks in the column density map. A simple analysis suggests that the density profile has the form ∼r −(2.3 +2.2 −0.9 ) , as determined at the position of SMM 1. The broadband spectral energy distribution of IRAS 05399 suggests that it is near the Stage 0/I borderline. A visual inspection of the Spitzer/IRAC images provides hints of a quadrupolar-like jet morphology around IRAS 05399, supporting the possibility that it is a binary system. Conclusions. The source splitting into two subcores along the long axis can be explained by cylindrical Jeans-type fragmentation, but the steepness of the density profile is shallower than what is expected for an isothermal cylinder. The difference between the evolutionary stages of IRAS 05399 (protostellar) and SMM 1 (starless) suggests that the former has experienced a phase of rapid mass accretion, supported by the very long outflow it drives. The protostellar jet from IRAS 05399 might have influenced the nearby core SMM 1. In particular, the temperature map features are likely to be imprints of protostellar or shock heating, while external heating could be provided by the nearby high-mass star-forming region NGC 2024.

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“…The G35.03 region has been studied in several molecular high-density tracers, such as NH 3 (Harju et al 1993;Codella et al 2010;, CS (Anglada et al 1996;Bronfman et al 1996;Larionov et al 1999), H 13 CO + , and CH 3 OH (Cyganowski et al 2009). Interferometric centimeter continuum observations have revealed the presence of at least five compact sources see Fig.…”

Section: Introductionmentioning

confidence: 99%

Filamentary structure and Keplerian rotation in the high-mass star-forming region G35.03+0.35 imaged with ALMA

Beltrán

Sánchez-Monge

Cesaroni

et al. 2014

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Context. Theoretical scenarios propose that high-mass stars are formed by disk-mediated accretion. Aims. To test the theoretical predictions on the formation of massive stars, we wish to make a thorough study at high-angular resolution of the structure and kinematics of the dust and gas emission toward the high-mass star-forming region G35.03+0.35, which harbors a disk candidate around a B-type (proto)star. Methods. We carried out ALMA Cycle 0 observations at 870 μm of dust of typical high-density, molecular outflow, and cloud tracers with resolutions of <0. 5. Complementary Subaru COMICS 25 μm observations were carried out to trace the mid-infrared emission toward this star-forming region. Results. The submillimeter continuum emission has revealed a filamentary structure fragmented into six cores, called A-F. The filament could be in quasi-equilibrium taking into account that the mass per unit length of the filament, 200-375 M /pc, is similar to the critical mass of a thermally and turbulently supported infinite cylinder, ∼335 M /pc. The cores, which are on average separated by ∼0.02 pc, have deconvolved sizes of 1300-3400 AU, temperatures of 35-240 K, H 2 densities >10 7 cm −3 , and masses in the range 1-5 M , and they are subcritical. Core A, which is associated with a hypercompact Hii region and could be the driving source of the molecular outflow observed in the region, is the most chemically rich source in G35.03+0.35 with strong emission of typical hot core tracers such as CH 3 CN. Tracers of high density and excitation show a clear velocity gradient along the major axis of the core, which is consistent with a disk rotating about the axis of the associated outflow. The PV plots along the SE-NW direction of the velocity gradient show clear signatures of Keplerian rotation, although infall could also be present, and they are consistent with the pattern of an edge-on Keplerian disk rotating about a star with a mass in the range 5-13 M . The high t ff /t rot ratio for core A suggests that the structure rotates fast and that the accreting material has time to settle into a centrifugally supported disk. Conclusions. G35.03+0.35 is one of the most convincing examples of Keplerian disks rotating about high-mass (proto)stars. This supports theoretical scenarios according to which high-mass stars, at least B-type stars, would form through disk-mediated accretion.

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Ammonia Clumps in the Orion and Cepheus Clouds

Cited by 104 publications

References 8 publications

Prestellar and protostellar cores in Orion B9

Prestellar and protostellar cores in Orion B9

SABOCA 350-μm and LABOCA 870-μm dust continuum imaging of IRAS 05399-0121: mapping the dust properties of a pre- and protostellar core system

Filamentary structure and Keplerian rotation in the high-mass star-forming region G35.03+0.35 imaged with ALMA

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