MAPPING STUDY OF 71 PLANCK COLD CLUMPS IN THE TAURUS, PERSEUS, AND CALIFORNIA COMPLEXES

Pelkonen

et al. 2015

A&A

Context. The study of prestellar cores is essential to understanding the initial stages of star formation. With Herschel more cold clumps have been detected than ever before. For this study we have selected 21 cold clumps from 20 Herschel fields observed as a follow-up on original Planck detections. We have observed these clumps in 13 CO (1−0), C 18 O (1−0), and N 2 H + (1−0) lines. Aims. Our aim is to find out if these cold clumps are prestellar. We have examined to what extent independent analysis of the dust and the molecular lines lead to similar conclusions about the masses of these objects. Methods. We calculate the clump masses and densities from the dust continuum and molecular line observations and compare these to each other and to the virial and Bonnor-Ebert masses calculated for each clump. Finally we examine two of the fields with radiative transfer models to estimate CO abundances. Results. When excitation temperatures could be estimated, the column densities derived from molecular line observations were comparable to those from dust continuum data. The median column density estimates are 4.2 × 10 21 cm −2 and 5.5 × 10 21 cm −2 for the line and dust emission data, respectively. The calculated abundances, column densities, volume densities, and masses all have large uncertainties and one must be careful when drawing conclusions. Abundance of 13 CO was found in modeling the two clumps in the field G131.65+9.75 to be close to the usual value of 10 −6 . The abundance ratio of 13 CO and C 18 O was ∼10. Molecular abundances could only be estimated with modeling, relying on dust column density data. Conclusions. The results indicate that most cold clumps, even those with dust color temperatures close to 11 K, are not necessarily prestellar.

Section: Discussionmentioning

confidence: 53%

The physical state of selected cold clumps

Parikka

Pelkonen

et al. 2015

A&A

“…Meng et al (2013) and Zhang et al (2016) made CO(1-0) observations at the Purple Mountain Observatory (PMO) radio telescope, fully or partially covering 17 of our SCUBA-2 fields. In Fig.…”

Section: Seds Of Iras and Planck Datamentioning

confidence: 99%

Herscheland SCUBA-2 observations of dust emission in a sample ofPlanckcold clumps

Pattle

et al. 2018

A&A

Self Cite

Context. Analysis of all-sky Planck submillimetre observations and the IRAS 100 µm data has led to the detection of a population of Galactic cold clumps. The clumps can be used to study star formation and dust properties in a wide range of Galactic environments. Aims. Our aim is to measure dust spectral energy distribution (SED) variations as a function of the spatial scale and the wavelength. Methods. We examine the SEDs at large scales using IRAS, Planck, and Herschel data. At smaller scales, we compare with JCMT/SCUBA-2 850 µm maps with Herschel data that are filtered using the SCUBA-2 pipeline. Clumps are extracted using the Fellwalker method and their spectra are modelled as modified blackbody functions. Results. According to IRAS and Planck data, most fields have dust colour temperatures T C ∼ 14 − 18 K and opacity spectral index values of β = 1.5 − 1.9. The clumps/cores identified in SCUBA-2 maps have T ∼ 13 K and similar β values. There are some indications of the dust emission spectrum becoming flatter at wavelengths longer than 500 µm. In fits involving Planck data, the significance is limited by the uncertainty of the corrections for CO line contamination. The fits to the SPIRE data give a median β value slightly above 1.8. In the joint SPIRE and SCUBA-2 850 µm fits the value decreases to β ∼1.6. Most of the observed T -β anticorrelation can be explained by noise. Conclusions. The typical submillimetre opacity spectral index β of cold clumps is found to be ∼1.7. This is above the values of diffuse clouds but lower than in some previous studies of dense clumps. There is only tentative evidence of T -β anticorrelation and β decreasing at millimetre wavelengths.

“…Those sources are prime candidates for probing how prestellar cores form and evolve, as well as the initial stages of star formation across a wide variety of Galactic environments. The detection of gravitationally bound CO gas clumps (Liu et al 2012a;Meng et al 2013;Zhang et al 2016) and dense molecular line tracers (Yuan et al 2016;Tatematsu et al 2017) inside PGCCs strongly suggests that many PGCCs have the ability to form stars. Moreover, their low level of CO gas depletion indicates that the natal clouds of PGCCs are still in the early stages of molecular cloud evolution (Liu et al 2013b).…”

Section: Planck Galactic Cold Clumpsmentioning

confidence: 99%

“…The JCMT data reduction methods are similar to those used in the JCMT Gould Belt survey and JCMT transient survey (Ward-Thompson et al 2007;Mairs et al 2015Mairs et al , 2017Herczeg et al, submitted). The data reduction procedure was performed using the iterative mapmaking technique makemap in the SMURF package of the Starlink software Currie et al 2014).…”

Section: A2 Jcmt/scuba-2 Data Reductionmentioning

confidence: 99%

“…Generally, the largest recoverable scales are~ 600 before atmospheric signal becomes significant. The details of JCMT data reduction can be found in Mairs et al (2015Mairs et al ( , 2017. In this paper, we performed four individual data reductions labeled R1, R2, R3, and R4with different external masks and spatial filters for comparison.…”

Section: A2 Jcmt/scuba-2 Data Reductionmentioning

confidence: 99%

See 1 more Smart Citation

The TOP-SCOPE Survey of Planck Galactic Cold Clumps: Survey Overview and Results of an Exemplar Source, PGCC G26.53+0.17

Liu

Kim

et al. 2018

ApJS

Self Cite

The low dust temperatures (<14 K) of Planck Galactic cold clumps (PGCCs) make them ideal targets to probe the initial conditions and very early phase of star formation. "TOP-SCOPE" is a joint survey program targeting ∼2000 PGCCs in J=1-0 transitions of CO isotopologues and ∼1000 PGCCs in 850 μm continuum emission. The objective of the "TOP-SCOPE" survey and the joint surveys (SMT 10 m, KVN 21 m, and NRO 45 m) is to statistically study the initial conditions occurring during star formation and the evolution of molecular clouds, across a wide range of environments. The observations, data analysis, and example science cases for these surveys are introduced with an exemplar source, PGCC G26.53+0.17 (G26), which is a filamentary infrared dark cloud (IRDC). The total mass, length, and mean line mass (M/L) of the G26 filament are ∼6200 M ☉ , ∼12 pc, and ∼500 M ☉ pc −1 , respectively. Ten massive clumps, including eight starless ones, are found along the filament. The most massive clump as a whole may still be in global collapse, while its denser part seems to be undergoing expansion owing to outflow feedback. The fragmentation in the G26 filament from cloud scale to clump scale is in agreement with gravitational fragmentation of an isothermal, nonmagnetized, and turbulent supported cylinder. A bimodal behavior in dust emissivity spectral index (β) distribution is found in G26, suggesting grain growth along the filament. The G26 filament may be formed owing to large-scale compression flows evidenced by the temperature and velocity gradients across its natal cloud.