The relationship of CO abundance to extinction and<i>N</i>(H$\mathsf{_{2}}$):

Harjunpaa, P.; Lehtinen, K.; Haikala, L. K.

doi:10.1051/0004-6361:20035752

Cited by 31 publications

(28 citation statements)

References 32 publications

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“…N H 2 is the molecular hydrogen column density obtained using the relation N H 2 ¼ 1:1 ; 10 4 N 12 by Frerking et al (1982) for the Taurus cloud; this result is consistent with more recent determinations, summarized by Harjunpää et al (2004), for other nearby dark clouds. Table 1 summarizes our results for the mass of the outflowing gas in the various regions previously defined, tabulated .…”

Section: Outflow Mass and Energysupporting

confidence: 90%

Entrainment Mechanisms for Outflows in the L1551 Star‐forming Region

Stojimirović

Narayanan

Snell

et al. 2006

ApJ

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We present high sensitivity 12 CO and 13 CO J ¼ 1 ! 0 maps covering the full extent of the parsec-scale L1551 molecular outflow, including the redshifted east-west (EW) flow. We also present 12 CO J ¼ 3 ! 2 data obtained over a good fraction of the L1551 outflow. We compare the molecular data to wide-field, narrowband optical emission in H . While there are multiple outflows in the L1551 cloud, the main outflow is oriented at 50 position angle and appears to be driven by an embedded source(s) in the central IRS 5 region. The J ¼ 3 ! 2 data indicate that there may be molecular emission associated with the L1551 NE jet, within the redshifted lobe of the main outflow. We have also better defined the EW flow and believe we have identified its blueshifted counterpart. We speculate that the origin of the EW outflow lies near HH 102. Velocity-dependent opacity correction is used to estimate the mass and energy of the outflow. The resulting mass spectral indices from our analysis are systematically lower (less steep) than the power-law indices obtained toward other outflows in several recent studies that use a similar opacity correction method. We show that systematic errors and biases in the mass analysis procedures could result in errors in the determination of the power-law indices. The mass spectral indices, the morphological appearance of the positionvelocity plots, and integrated intensity maps of molecular data, compared with the optical, suggest that jet-driven bow shock entrainment is the best explanation for the driving mechanism of outflows in L1551. The kinetic energy of the outflows is found to be comparable to the binding energy of the cloud and sufficient to maintain the turbulence in the L1551 cloud.

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Section: Outflow Mass and Energysupporting

confidence: 90%

Entrainment Mechanisms for Outflows in the L1551 Star‐forming Region

Stojimirović

Narayanan

Snell

et al. 2006

ApJ

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“…We assume a maximum fractional abundance of 1.5 × 10 −6 for 13 CO (Frerking et al 1982;Harjunpää et al 2004 are further scaled by a factor k = 16n 2 5 × 10 5 + 16n 2 , (A.2) which depends on the local H 2 density, n (in units cm −3 ). With this scaling, the maximum abundance is reached only at densities above n = 10 3 cm −3 .…”

Section: Discussionmentioning

confidence: 99%

“…Most studies find values close to 2 × 10 −6 , like 1.5 × 10 −6 in Taurus and 2.9 × 10 −6 in Ophiuchus (Frerking et al 1982), 2.3 × 10 −6 in IC5146 (Lada et al 1994) or 2.5 × 10 −6 in Perseus (Pineda et al 2008). Harjunpää et al (2004) found values between 0.9−3.5 × 10 −6 in their survey of the three globules B 133, B 335 and L 466. We use an abundance of 10 −6 in our calculations of N(H 2 ) gas that results in a good agreement seen on Fig.…”

Section: The Temperatures and Column Densities Of The Clumpsmentioning

confidence: 96%

A CO survey on a sample ofHerschelcold clumps

Fehér

Juvela

Lunttila

et al. 2017

A&A

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Context. The physical state of cold cloud clumps has a great impact on the process and efficiency of star formation and the masses of the forming stars inside these objects. The sub-millimetre survey of the Planck space observatory and the far-infrared follow-up mapping of the Herschel space telescope provide an unbiased, large sample of these cold objects. Aims. We have observed 12 CO(1−0) and 13 CO(1−0) emission in 35 high-density clumps in 26 Herschel fields sampling different environments in the Galaxy. We derive the physical properties of the objects and estimate their gravitational stability. Methods. The densities and temperatures of the clumps were calculated from both the dust continuum and the molecular line data. Kinematic distances were derived using 13 CO(1−0) line velocities to verify previous distance estimates and the sizes and masses of the objects were calculated by fitting 2D Gaussian functions to their optical depth distribution maps on 250 µm. The masses and virial masses were estimated assuming an upper and lower limit on the kinetic temperatures and considering uncertainties due to distance limitations. Results. The derived excitation temperatures are between 8.5−19.5 K, and for most clumps between 10−15 K, while the Herschel-derived dust colour temperatures are more uniform, between 12−16 K. The sizes (0.1−3 pc), 13 CO column densities (0.5−44 × 10 15 cm −2 ) and masses (from less than 0.1 M to more than 1500 M ) of the objects all span broad ranges. We provide new kinematic distance estimates, identify gravitationally bound or unbound structures and discuss their nature. Conclusions. The sample contains objects on a wide scale of temperatures, densities and sizes. Eleven gravitationally unbound clumps were found, many of them smaller than 0.3 pc, but large, parsec-scale clouds with a few hundred solar masses appear as well. Colder clumps have generally high column densities but warmer objects appear at both low and higher column densities. The clump column densities derived from the line and dust observations correlate well, but are heavily affected by uncertainties of the dust properties, varying molecular abundances and optical depth effects.

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“…Since then, the ratio has been examined by Frerking et al (1982) in Taurus and ρ Ophiuchi, Harjunpää et al (1996) in Chamaeleon I, R Corona Australis and Coalsack, Hayakawa et al (1999Hayakawa et al ( , 2001 in the Chamaeleon complex, and by Lada et al (1994), Alves et al (1999), Juvela et al (1997Juvela et al ( , 2002 and Harjunpää et al (2004) in several small globules. These data, reviewed and compared in more detail by Harjunpää et al (2004), show some evidence supporting the correlation of N(C 18 O)/A V with star forming activity. We present the derivation of the N(C 18 O)/A V ratio in Chamaeleon I, and in selected region of Chamaeleon III, with emphasis on the possible difference between star forming and non-star forming regions.…”

Section: Introductionmentioning

confidence: 99%

The ratio ofN(C$\mathsf{^{18}}$O) andA$\mathsf{_{V}}$ in Chamaeleon I and III-B

Kainulainen¹,

Lehtinen²,

Harju³

2006

A&A

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The shallow proportionality suggests that C 18 O is heavily depleted in these regions. As the degree of depletion is proportional to the gas density, these regions probably contain very dense, cold cores, which do not stand out in CO mappings. A comparison with the dust temperature map derived from the ISO data shows that the most prominent of the potentially depleted cores indeed coincides with a dust temperature minimum. It seems therefore feasible to use N(C 18 O) and A V data together for identifying cold, dense cores in large scale mappings.

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The relationship of CO abundance to extinction andN(H$\mathsf{_{2}}$):

Cited by 31 publications

References 32 publications

Entrainment Mechanisms for Outflows in the L1551 Star‐forming Region

Entrainment Mechanisms for Outflows in the L1551 Star‐forming Region

A CO survey on a sample ofHerschelcold clumps

The ratio ofN(C$\mathsf{^{18}}$O) andA$\mathsf{_{V}}$ in Chamaeleon I and III-B

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