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Myers, L.; Lambert, J.M.; Treado, P.A.; Šlaus, I.; Harper, E. P.; Devins, D.W.; Allas, R.G.

doi:10.1103/physrevc.28.29

Cited by 7 publications

(8 citation statements)

References 52 publications

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“…Line center velocity difference of various molecular species may origin from molecular layers with different temperature or trace different kinematical gas layers (Bergin et al 1997;Muller et al 2011). The deviation between V 13 and V 18 of the Planck clumps also tends to be smaller than those of Myers, Linke & Benson (1983). All these suggest that the cold clumps are the quietest molecular regions found so far as a whole.…”

Section: The Line Center Velocitiesmentioning

confidence: 69%

“…where B, µ, J are the rotational constant, permanent dipole moment, and the rotational quantum number of the lower state of the molecular transition. Column densities of the 13 CO and C 18 O molecules were calculated and given in Column 8 and 10 of (Myers, Linke & Benson 1983) which are from 3×10 14 to 2.7×10 15 cm −2 . The different column density ranges between our sample and the nearby dark clouds may be attributed to the larger space distribution of Planck cold clumps than the nearby dark clouds.…”

Section: Derived Physical Parametersmentioning

confidence: 99%

“…1980;Clark & Johnson 1981). After visual inspection, 70 small opaque spots were chosen for the surveys of low-mass cores with the 13 CO, C 18 O and NH 3 respectively (Myers, Linke & Benson 1983;. A number of sources resulted in these earliest observations are still primary examples in low mass star formation so far.…”

Section: Introductionmentioning

confidence: 99%

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

Liu

Meng

et al. 2012

ApJ

118

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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.

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Section: The Line Center Velocitiesmentioning

confidence: 69%

Section: Derived Physical Parametersmentioning

confidence: 99%

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

Liu

Meng

et al. 2012

ApJ

118

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“…For both samples, the coupling is "marginal," i.e. strong enough to allow propagation of MHD waves, but weak enough for some wave damping to occur (Martin, Heyvaerts, & Priest 1997, Nakano 1998, Myers & Lazarian 1998. This suggests that both low mass and massive cores are more vulnerable to fragmentation and dissipation of their turbulence than are their lower-density, better-coupled environs (Myers 1997).…”

Section: Ion-neutral Coupling In Massive Coresmentioning

confidence: 99%

The Ionization Fraction in Dense Molecular Gas. II. Massive Cores

Bergin

Plume

Williams

et al. 1999

ApJ

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We present an observational and theoretical study of the ionization fraction in several massive cores located in regions that are currently forming stellar clusters. Maps of the emission from the J = 1 → 0 transitions of C 18 O, DCO + , N 2 H + , and H 13 CO + , as well as the J = 2 → 1 and J = 3 → 2 transitions of CS, were obtained for each core. Core densities are determined via a large velocity gradient analysis with values typically ∼ 10 5 cm −3 . With the use of observations to constrain variables in the chemical calculations we derive electron fractions for our overall sample of 5 cores directly associated with star formation and 2 apparently starless cores. The electron abundances are found to lie within a small range, −6.9 < log 10 (x e ) < −7.3, and are consistent with previous work. We find no difference in the amount of ionization fraction between cores with and without associated star formation activity, nor is any difference found in electron abundances between the edge and center of the emission region. Thus our models are in agreement with the standard picture of cosmic rays as the primary source of ionization for molecular ions. With the addition of previously determined electron abundances for low mass cores, and even more massive cores associated with O and B clusters, we systematically examine the ionization fraction as a function of star formation activity. This analysis demonstrates that the most massive sources stand out as having the lowest electron abundances (x e < 10 −8 ).

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“…The filamentary and clumpy distribution of the molecular gas has been revealed through large-scale CO surveys (de Geus et al 1990;Loren 1989a,b). Embedded in the filaments are dense clumps, recognised by mapping in emission lines of NH 3 , DCO + and C 18 O, with properties similar to the cores in Taurus (Myers & Benson 1983;Benson & Myers 1989;Loren et al 1990;Tachihara et al 2000). Typically, clump masses are in the range 10−30 M .…”

Section: Introductionmentioning

confidence: 99%

An unbiased search for the signatures of protostars in the ρ Ophiuchi A molecular cloud

Khanzadyan¹,

Gredel²,

Smith³

et al. 2004

A&A

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Abstract. We present an unbiased search for molecular hydrogen emission in the L1688 cloud within the ρ Ophiuchi molecular cloud complex. Our near-infrared survey covers a connected region of extent 35 × 35 . We detect several new H 2 flows but the total number of detected outflows is low and is consistent with the paucity of Class 0 and Class 1 sources in the molecular cloud. From the spatial distribution, their collimation and the individual shapes of the bow shocks, we suggest possible candidates for the outflow sources. Most of the candidate driving sources are deeply embedded in dense cores of the molecular cloud. A very young outflow arises from the newly discovered Class 0 source MMS 126. Two major outflows in the NE-SW direction arise from the YLW 15 and YLW 16 Class I sources. Three additional outflows, which both extend over several arcminutes, arise from the Class I sources YLW 31 and YLW 52. Flow directions are generally NE-SW, perpendicular to the elongation directions of the cloud filaments. The apparent extents of molecular flows are related to either the widths of cloud filaments or to the separation between filaments. The estimated jet power needed to continuously drive and excite the detected portions of the shocked H 2 outflows lies in the range 0.02−0.2 L . Given the critical dependence on the environment, however, the total sizes and powers of the outflows may be considerably larger.

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He3(p,
L. Myers
¹
,
J.M. Lambert
²
,
P.A. Treado
³

et al.

Cited by 7 publications

References 52 publications

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

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

The Ionization Fraction in Dense Molecular Gas. II. Massive Cores

An unbiased search for the signatures of protostars in the ρ Ophiuchi A molecular cloud

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He3(p,L. Myers1, J.M. Lambert2, P.A. Treado3 et al.

Cited by 7 publications

References 52 publications

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

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

The Ionization Fraction in Dense Molecular Gas. II. Massive Cores

An unbiased search for the signatures of protostars in the ρ Ophiuchi A molecular cloud

Contact Info

Product

Resources

About

He3(p,
L. Myers
¹
,
J.M. Lambert
²
,
P.A. Treado
³

et al.

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

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