<i>Herschel</i> and SCUBA-2 observations of dust emission in a sample of <i>Planck</i> cold clumps

Juvela, Mika,He, Jinhua,Pattle, Katherine,Liu, Tie,Bendo, George,Eden, David J.,Fehé,r, Orsolya,Michel, Fich,Fuller, Gary,Hirano, Naomi,Kim, Kee-Tae,Li, Di,Liu, Sheng-Yuan,Malinen, Johanna,Marsh Springer-Verlag 2018 Astronomy and astrophysics Vol.612 No.-

<P><I>Context.</I> Analysis of all-sky <I>Planck</I> submillimetre observations and the IRAS 100 <I>μ</I>m 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.</P><P><I>Aims.</I> Our aim is to measure dust spectral energy distribution (SED) variations as a function of the spatial scale and the wavelength.</P><P><I>Methods.</I> We examined the SEDs at large scales using IRAS, <I>Planck</I>, and <I>Herschel</I> data. At smaller scales, we compared JCMT/SCUBA-2 850 <I>μ</I>m maps with <I>Herschel</I> data that were filtered using the SCUBA-2 pipeline. Clumps were extracted using the Fellwalker method, and their spectra were modelled as modified blackbody functions.</P><P><I>Results.</I> According to IRAS and <I>Planck</I> data, most fields have dust colour temperatures <I>T</I>C ~ 14-18 K and opacity spectral index values of <I>β</I> = 1.5-1.9. The clumps and cores identified in SCUBA-2 maps have <I>T</I> ~ 13 K and similar <I>β</I> values. There are some indications of the dust emission spectrum becoming flatter at wavelengths longer than 500 <I>μ</I>m. In fits involving <I>Planck</I> data, the significance is limited by the uncertainty of the corrections for CO line contamination. The fits to the SPIRE data give a median <I>β</I> value that is slightly above 1.8. In the joint SPIRE and SCUBA-2 850 <I>μ</I>m fits, the value decreases to <I>β</I> ~ 1.6. Most of the observed <I>T</I>-<I>β</I> anticorrelation can be explained by noise.</P><P><I>Conclusions.</I> The typical submillimetre opacity spectral index <I>β</I> 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 a <I>T</I>-<I>β</I> anticorrelation and <I>β</I> decreasing at millimetre wavelengths.</P>

A Holistic Perspective on the Dynamics of G035.39-00.33: The Interplay between Gas and Magnetic Fields

Liu, Tie,Li, Pak Shing,Juvela, Mika,Kim, Kee-Tae,Evans II, Neal J.,Francesco, James Di,Liu, Sheng-Yuan,Yuan, Jinghua,Tatematsu, Ken’ichi,Zhang, Qizhou,Ward-Thompson, Derek,Fuller, Gary,Goldsmith, Paul American Astronomical Society 2018 The Astrophysical journal Vol.859 No.2

<P>Magnetic field plays a crucial role in shaping molecular clouds and regulating star formation, yet the complete information on the magnetic field is not well constrained owing to the limitations in observations. We study the magnetic field in the massive infrared dark cloud G035.39-00.33 from dust continuum polarization observations at 850 mu m with SCUBA-2/POL-2 at JCMT for the first time. The magnetic field tends to be perpendicular to the densest part of the main filament (F-M), whereas it has a less defined relative orientation in the rest of the structure, where it tends to be parallel to some diffuse regions. A mean plane-of-the-sky magnetic field strength of similar to 50 mu G for F-M is obtained using the Davis-Chandrasekhar-Fermi method. Based on (CO)-C-13 (1-0) line observations, we suggest a formation scenario of F-M due to large-scale (similar to 10 pc) cloud-cloud collision. Using additional NH3 line data, we estimate that F-M will be gravitationally unstable if it is only supported by thermal pressure and turbulence. The northern part of F-M, however, can be stabilized by a modest additional support from the local magnetic field. The middle and southern parts of F-M are likely unstable even if the magnetic field support is taken into account. We claim that the clumps in F-M may be supported by turbulence and magnetic fields against gravitational collapse. Finally, we identified for the first time a massive (similar to 200 M-circle dot, collapsing starless clump candidate, 'c8,' in G035.39-00.33. The magnetic field surrounding 'c8' is likely pinched, hinting at an accretion flow along the filament.</P>

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

Liu, Tie,Kim, Kee-Tae,Juvela, Mika,Wang, Ke,Tatematsu, Ken’ichi,Francesco, James Di,Liu, Sheng-Yuan,Wu, Yuefang,Thompson, Mark,Fuller, Gary,Eden, David,Li, Di,Ristorcelli, I.,Kang, Sung-ju,Lin, Yuxin Published by the University of Chicago Press for t 2018 The Astrophysical journal Supplement series Vol.234 No.2

<P>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 similar to 2000 PGCCs in J = 1-0 transitions of CO isotopologues and similar to 1000 PGCCs in 850 mu m 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 similar to 6200 M-circle dot, similar to 12 pc, and similar to 500 M-circle dot 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 (beta) 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.</P>

Astrochemical Properties of Planck Cold Clumps

Tatematsu, Ken’ichi,Liu, Tie,Ohashi, Satoshi,Sanhueza, Patricio,Nguyê,̃,n Lu’o’, Quang,Hirota, Tomoya,Liu, Sheng-Yuan,Hirano, Naomi,Choi, Minho,Kang, Miju,A.Thompson, Mark,Fuller, Gary,Wu, Y Published by the University of Chicago Press for t 2017 The Astrophysical journal Supplement series Vol.228 No.2

<P>We observed 13 Planck cold clumps with the James Clerk Maxwell Telescope/SCUBA-2 and with the Nobeyama 45 m radio telescope. The N2H+ distribution obtained with the Nobeyama telescope is quite similar to SCUBA-2 dust distribution. The 82 GHz HC3N, 82 GHz CCS, and 94 GHz CCS emission are often distributed differently with respect to the N2H+ emission. The CCS emission, which is known to be abundant in starless molecular cloud cores, is often very clumpy in the observed targets. We made deep single-pointing observations in DNC, (HNC)-C-13, N2D+, and cyclic-C3H2 toward nine clumps. The detection rate of N2D+ is 50%. Furthermore, we observed the NH3 emission toward 15 Planck cold clumps to estimate the kinetic temperature, and confirmed that most targets are cold (less than or similar to 20 K). In two of the starless clumps we observed, the CCS emission is distributed as it surrounds the N2H+ core (chemically evolved gas), which resembles the case of L1544, a prestellar core showing collapse. In addition, we detected both DNC and N2D+. These two clumps are most likely on the verge of star formation. We introduce the chemical evolution factor (CEF) for starless cores to describe the chemical evolutionary stage, and analyze the observed Planck cold clumps.</P>

Planck Cold Clumps in the <i>λ</i> Orionis Complex. II. Environmental Effects on Core Formation

Yi, Hee-Weon,Lee, Jeong-Eun,Liu, Tie,Kim, Kee-Tae,Choi, Minho,Eden, David,II, Neal J. Evans,Francesco, James Di,Fuller, Gary,Hirano, N.,Juvela, Mika,Kang, Sung-ju,Kim, Gwanjeong,M. Koch, Patrick,Lee, American Astronomical Society 2018 The Astrophysical journal, Supplement series Vol.236 No.2

<P>Based on the 850 mu m dust continuum data from SCUBA-2 at James Clerk Maxwell Telescope (JCMT), we compare overall properties of Planck Galactic Cold Clumps (PGCCs) in the lambda Orionis cloud to those of PGCCs in the Orion A and B clouds. The Orion A and B clouds are well-known active star-forming regions, while the A Orionis cloud has a different environment as a consequence of the interaction with a prominent OB association and a giant H-II region. PGCCs in the lambda Orionis cloud have higher dust temperatures (T-d = 16.13 +/- 0.15 K) and lower values of dust emissivity spectral index (beta = 1.65 +/- 0.02) than PGCCs in the Orion A (T-d = 13.79 +/- 0.21 K, beta = 2.07 +/- 0.03) and Orion B (T-d = 13.82 +/- 0.19 K, beta =1.96 +/- 0.02) clouds. We find 119 substructures within the 40 detected PGCCs and identify them as cores. Out of a total of 119 cores, 15 cores are discovered in the lambda Orionis cloud, while 74 and 30 cores are found in the Orion A and B clouds, respectively. The cores in the lambda Orionis cloud show much lower mean values of size R = 0.08 pc, column density N(H-2) (9.5 +/- 1.2) x 10(22)cm(-2) , number density n(H-2) - (2.9 +/- 0.4) x 10 5 CM -3 , and mass M-core = 1.0 +/- 0.3 M(circle dot)compared to the cores in the Orion A [R = 0.11 pc, N(H-2) = (2.3 +/- 0.3) x 10(23) cm(-2), n(H-2) = (3.8 +/- 0.5) x 10(5)cm(-3) , and M-core = 2.4 +/- 0.3 M-circle dot] and Orion B [R = 0.16 pc, N(H-2) (3.8 +/- 0.4) x 10(23) cm(-2), n(H-2) = (15.6 +/- 1.8) x 10(5) cm(-3) , and M-core = 2.7 +/- 0.3 M-circle dot] clouds. These core properties in the A Orionis cloud can be attributed to the photodissociation and external heating by the nearby H rr region, which may prevent the PGCCs from forming gravitationally bound structures and eventually disperse them. These results support the idea of negative stellar feedback on core formation.</P>