GAS EMISSIONS IN PLANCK COLD DUST CLUMPS—A SURVEY OF THEJ= 1-0 TRANSITIONS OF¹²CO,¹³CO, AND C¹⁸O

Abstract

A survey toward 674 Planck cold clumps of the Early Cold Core Catalogue (ECC) in the J=1-0 transitions of 12 CO, 13 CO and C 18 O has been carried out using the PMO 13.7 m telescope. 673 clumps were detected with the 12 CO and 13 CO, and 68% of the samples have C 18 O emission. Additional velocity components were also identified. A close consistency of the three line peak velocities was revealed for the first time. Kinematic distances are given out for all the velocity components and half of the clumps are located within 0.5 and 1.5 kpc. Excitation temperatures range from 4 to 27 K, slightly larger than those of T d . Line width analysis shows that the majority of ECC clumps are low mass clumps. Column densities N H 2 span from 10 20 to 4.5×10 22 cm −2 with an average value of (4.4±3.6)×10 21 cm −2 . N H 2 cumulative fraction distribution deviates from the lognormal distribution, which is attributed to optical depth. The average abundance ratio of the 13 CO to C 18 O in these clumps is 7.0±3.8, higher than the terrestrial value. Dust and gas are well coupled in 95% of the clumps. Blue profile, red profile and line asymmetry in total was found in less than 10% of the clumps, generally indicating star formation is not developed yet. Ten clumps were mapped. Twelve velocity components and 22 cores were obtained. Their morphologies include extended diffuse, dense isolated, cometary and filament, of which the last is the majority. 20 cores are starless. Only 7 cores seem to be in gravitationally bound state. Planck cold clumps are the most quiescent among the samples of weak-red IRAS, infrared dark clouds, UC Hii region candidates, EGOs and methanol maser sources, suggesting that Planck cold clumps have expanded the horizon of cold Astronomy.

Galactic cold cores

“…These observations by Wu et al (2012) are a good opportunity to check whether the data from the survey of Dame et al (2001) can be associated with our higher resolution Herschel data, despite the low spatial resolution (∼7 arcmin) and the poor spatial sampling of the survey. Figure 2 shows that the agreement between the two sets of observations is generally within the error bars.…”

“…Among our fields, 38 are covered by the fully sampled part of the survey, 57 by the partially sampled part, and 21 are not covered at all. Wu et al (2012) observed the J = 1−0 CO line towards 674 Planck clumps using the Purple Mountain Observatory 13.7 m telescope. Only 44 of our fields host sources observed by these authors.…”

“…For some (43) fields, dedicated observations of 12 CO were reported by Wu et al (2012). The authors provide the values of velocity from Gaussian fitting of CO lines, as well as kinematic distance estimates.…”

“…In Table D.1, we gather all the distance estimates obtained for all the methods. We provide the radial velocities extracted from the CO data of Dame et al (2001) and compare them with the radial velocities from Wu et al (2012). For the extinction method, we provide the most important parameters:…”

The Young Stellar Population of Lynds 1340. An Infrared View

“…The effects of young intermediate-mass stars on the environment are conspicuous in L1340 B. The wispy structure of the 8 μm emission, the bowshock-like structure associated with an A2-type star, and the double-peaked CO lines at the positions of the Planck Cold Clumps (Wu et al 2012) associated with L1340 suggest violent swirling of the gas in this region. The low surface density of YSOs, compared to the other clumps of the cloud, indicates that the prestellar gas in L1340 B had higher temperature and lower density than in L1340 A and L1340 C, owing to the heating from the ambient B-type stars.…”