Large Area Mapping at 850 μm. IV. Analysis of the Clump Distribution in the Orion B South Molecular Cloud

Johnstone, Doug; Matthews, H. E.; Mitchell, G. F.

doi:10.1086/499258

Cited by 74 publications

(104 citation statements)

References 62 publications

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“…For example, the Class 0 sources SMM 3 and IRAS 05405-0117 have T kin values at the low end in the sample (11.3 K for both sources). This is consistent with the notion that embedded low-mass protostars do not heat significantly the parent cores, but the heating is localised in their immediate vicinity ( We note that in several previous submm surveys of Orion B dust temperatures around 20 K have been derived or assumed for dense cores (Johnstone et al 2001(Johnstone et al , 2006Nutter & Ward-Thompson 2007). Together with the results of Ikeda et al (2009) the present temperature determinations demonstrate that Orion B contains also several very cold cores resembling cores in nearby low-mass star forming regions (see, e.g., Rosolowsky et al 2008;Schnee et al 2009;Friesen et al 2009 and references therein).…”

Section: Discussionsupporting

confidence: 89%

Physical properties of dense cores in Orion B9

Miettinen

Harju

Haikala

et al. 2010

A&A

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Aims. We aim to determine the physical and chemical properties of the starless and protostellar cores in Orion B9, which represents a relatively quiescent star-forming region in Orion B. Methods. We observed the NH 3 (J, K) = (1, 1) and (2, 2) inversion lines and the N 2 H + (3−2) rotational lines, with the Effelsberg 100-m and APEX telescopes, respectively, towards the submillimetre peak positions in Orion B9. These data are used in conjunction with our APEX/LABOCA 870 μm dust continuum data of the region. Results. The gas kinetic temperature in the cores derived from the NH 3 data is between ∼9.4−13.9 K. The non-thermal velocity dispersion is subsonic in most of the cores. The non-thermal linewidth in protostellar cores appears to increase with increasing bolometric luminosity. The core masses, ∼2−8 M , are very likely drawn from the same parent distribution as the core masses in Orion B North. Based on the virial parameter analysis, starless cores in the region are likely to be gravitationally bound, and thus prestellar. Some of the cores have a lower radial velocity than the systemic velocity of the region, suggesting that they are members of the "low-velocity part" of Orion B. The observed core-separation distances deviate from the corresponding random-like model distributions. The distances between the nearest neighbours are comparable to the thermal Jeans length. The fractional abundances of NH 3 and N 2 H + in the cores are ∼1.5−9.8 × 10 −8 and ∼0.2−5.9 × 10 −10 , respectively. The NH 3 abundance appears to decrease with increasing H 2 column and number densities. The NH 3 /N 2 H + column density ratio is larger in starless cores than in cores with embedded protostars. Conclusions. The core population in Orion B9 is comparable in physical properties to those in nearby low-mass star-forming regions. The Orion B9 cores also seem to resemble cores found in isolation rather than those associated with clusters. Moreover, because the cores may not be randomly distributed within the region (contrary to what was suggested in our Paper I), it is unclear whether the origin of cores could be explained by turbulent fragmentation. On the other hand, many of the core properties conform to the picture of dynamic core evolution. The Orion B9 region has probably been influenced by the feedback from the nearby Ori OB 1b group, and the fragmentation of the parental cloud into cores could be caused by gravitational instability.

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Section: Discussionsupporting

confidence: 89%

Physical properties of dense cores in Orion B9

Miettinen

Harju

Haikala

et al. 2010

A&A

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“…The dust temperature is found to be on average ∼17.5 K (with β = 2) in the diffuse atomic medium (Boulanger et al 1996) and to be lower in molecular clouds with no embedded bright stars (Lagache et al 1998). Small patches of bright molecular clouds have been observed in more detail from the ground by the JCMT (Johnstone et al 2006), and from the balloon borne experiments PRONAOS (Ristorcelli et al 2006) and Archeops (Désert et al 2008). At low temperatures (T < 30 K), the dust optical properties appear to change significantly in terms of absolute value of the emissivity and the spectral index β.…”

Section: Interstellar Dustmentioning

confidence: 99%

Evolution of interstellar dust withHerschel. First results in the photodissociation regions of NGC 7023

Abergel¹,

Arab²,

Compiègne

et al. 2010

A&A

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Context. In photodissociation regions (PDRs), the physical conditions and the excitation evolve on short spatial scales as a function of depth within the cloud, providing a unique opportunity to study how the dust and gas populations evolve with the excitation and physical conditions. The mapping of the PDRs in NGC 7023 performed during the science demonstration phase of Herschel is part of the "Evolution of interstellar dust" key program. The goal of this project is to build a coherent database on interstellar dust emission from diffuse clouds to the sites of star formation. Aims. We study the far-infrared/submillimeter emission of the PDRs and their fainter surrounding regions. We combine the Herschel and Spitzer maps to derive at each position the full emission spectrum of all dust components, which we compare to dust and radiative transfer models in order to learn about the spatial variations in both the excitation conditions and the dust properties. Methods. We adjust the emission spectra derived from PACS and SPIRE maps using modified black bodies to derive the temperature and the emissivity index β of the dust in thermal equilibrium with the radiation field. We present a first modeling of the NGC 7023-E PDR with standard dust properties and abundances. Results. At the peak positions, a value of β equal to 2 is compatible with the data. The detected spectra and the spatial structures are strongly influenced by radiative transfer effects. We are able to reproduce the spectra at the peak positions deduced from Herschel maps and emitted by dust particles at thermal equilibrium, and also the evolution of the spatial structures observed from the near infrared to the submillimeter. On the other hand, the emission of the stochastically heated smaller particles is overestimated by a factor ∼2.

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“…A similar result was obtained by Könyves et al (2010) with Herschel observations (i.e., in the far-IR spectrum) of the Aquila rift (see also André et al 2010). Extending to a few solar-like masses, there are for example the works of Johnstone et al (2006) and Nutter & Ward-Thompson (2007) on Orion. In these cases, which are also based on single-dish sub-mm observations, they recover a mass function similar to the IMF.…”

Section: The Cmf Of Iras 19410+2336mentioning

confidence: 99%

Fragmentation in the massive star-forming region IRAS 19410+2336

Rodón

Beuther

Schilke

2012

A&A

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Context. The core mass functions (CMFs) of low-mass star-forming regions are found to resemble the shape of the initial mass function (IMF). A similar result is observed for the dust clumps in high-mass star-forming regions, although on spatial scales of clusters that do not resolve the substructure that is found in these massive clumps. The region IRAS 19410+2336 is one exception, having been observed on spatial scales on the order of ∼2500 AU, which are sufficient to resolve the clump substructure into individual cores. Aims. We investigate the protostellar content of IRAS 19410+2336 at high spatial resolution at 1.4 mm, determining the temperature structure of the region and deriving its CMF. Methods. The massive star-forming region IRAS 19410+2336 was mapped with the PdBI (BCD configurations) at 1.4 mm and 3 mm in the continuum and several transitions of formaldehyde (H 2 CO) and methyl cyanide (CH 3 CN). The H 2 CO transitions were also observed with the IRAM 30 m Telescope. Results. We detect 26 continuum sources at 1.4 mm with a spatial resolution as low as ∼2200 AU, several of them with counterparts at near-and mid-infrared wavelengths, distributed in two (proto)clusters. With the PdBI CH 3 CN and PdBI/IRAM 30 m H 2 CO emission, we derive the temperature structure of the region, ranging from 35 K to 90 K. Using these temperatures, we calculate the core masses of the detected sources, ranging from ∼0.7 M to ∼8 M . These masses are strongly affected by the spatial filtering of the interferometer, which removes a common envelope with ∼90% of the single-dish flux. Considering only the detected dense cores and accounting for binning effects as well as cumulative distributions, we derive a CMF, with a power-law index β = −2.3 ± 0.2. We resolve the Jeans length of the (proto)clusters by one order of magnitude, and only find a small velocity dispersion between the different subsources. Conclusions. Since we cannot unambiguously differentiate between protostellar and prestellar cores, the derived CMF is not prestellar. Furthermore, because of the large fraction of missing flux, we cannot establish a firm link between the CMF and the IMF. This implies that future high-mass CMF studies will need to complement the interferometer continuum data with the short spacing information, a task suitable for ALMA. We note that the method of extracting temperatures using H 2 CO lines becomes less applicable when reaching the dense core scales of the interferometric observations because most of the H 2 CO appears to originate in the envelope structure.

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Large Area Mapping at 850 μm. IV. Analysis of the Clump Distribution in the Orion B South Molecular Cloud

Cited by 74 publications

References 62 publications

Physical properties of dense cores in Orion B9

Physical properties of dense cores in Orion B9

Evolution of interstellar dust withHerschel. First results in the photodissociation regions of NGC 7023

Fragmentation in the massive star-forming region IRAS 19410+2336

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