A CS J = 5 → 4 mapping survey toward high-mass star-forming cores associated with water masers

Yancy L Shirley, Neal J. Evans, Kaisa E. Young, Claudia Knez, Daniel T. Jaffe

Research output: Contribution to journalArticle

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Abstract

We have mapped 63 regions forming high-mass stars in CS J = 5 → 4 using the CSO. The CS peak position was observed in C 34S J = 5 → 4 toward 57 cores and in 13CS J = 5 → 4 toward the nine brightest cores. The sample is a subset of a sample originally selected toward water masers; the selection on maser sources should favor sources in an early stage of evolution. The cores are located in the first and second Galactic quadrants with an average distance of 5.3 ± 3.7 kpc and were well detected with a median peak signal-to-noise ratio in the integrated intensity of 40. The integrated intensity of CS J = 5 → 4 correlates very well with the dust continuum emission at 350 μm. For 57 sufficiently isolated cores, a well-defined angular size (FWHM) was determined. The core radius (R CS), aspect ratio [(a/b) obs], virial mass (M vir), surface density (∑), and the luminosity in the CS J = 5 → 4 line (L(CS54)) are calculated. The distributions of size, virial mass, surface density, and luminosity are all peaked with a few cores skewed toward much larger values than the mean. The median values, μ 1/2, are as follows: μ 1/2 (R CS) = 0.32 pc, μ 1/2 ((a/b) obs) = 1.20, μ 1/2 (M vir) = 920 M , μ 1/2 (∑) = 0.60 g cm -2, μ 1/2 (L(CS54)) = 1.9 × 10 -2 L and μ 1/2 (L bol/M vir) = 165 (L/M) . We find a weak correlation between C 34S line width and size, consistent with Δv ∼ R 0.3. The line widths are much higher than would be predicted by the usual relations between line width and size determined from regions of lower mass. These regions are very turbulent. The derived virial mass agrees within a factor of 2-3 with mass estimates from dust emission at 350 μm after corrections for the density structure are accounted for. The resulting cumulative mass spectrum of cores above 1000 M can be approximated by a power law with a slope of about -0.9, steeper than that of clouds measured with tracers of lower density gas and close to that for the total masses of stars in OB associations. The median turbulent pressures are comparable to those in UCH II regions, and the pressures at small radii are similar to those in hypercompact H II regions (P/k ∼ 10 10 K cm -3). The filling factors for dense gas are substantial, and the median abundance of CS is about 10 -9. The ratio of bolometric luminosity to virial mass is much higher than the value found for molecular clouds as a whole, and the correlation of luminosity with mass is tighter.

Original languageEnglish (US)
Pages (from-to)375-403
Number of pages29
JournalAstrophysical Journal, Supplement Series
Volume149
Issue number2
DOIs
StatePublished - Dec 2003
Externally publishedYes

Fingerprint

water masers
stars
luminosity
water
dust
radii
rarefied gases
quadrants
H II regions
masers
molecular clouds
mass spectra
set theory
tracers
gas
aspect ratio
signal-to-noise ratio
signal to noise ratios
power law
slopes

Keywords

  • Dust, extinction
  • ISM: clouds
  • ISM: molecules
  • Stars: formation

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

A CS J = 5 → 4 mapping survey toward high-mass star-forming cores associated with water masers. / Shirley, Yancy L; Evans, Neal J.; Young, Kaisa E.; Knez, Claudia; Jaffe, Daniel T.

In: Astrophysical Journal, Supplement Series, Vol. 149, No. 2, 12.2003, p. 375-403.

Research output: Contribution to journalArticle

Shirley, Yancy L ; Evans, Neal J. ; Young, Kaisa E. ; Knez, Claudia ; Jaffe, Daniel T. / A CS J = 5 → 4 mapping survey toward high-mass star-forming cores associated with water masers. In: Astrophysical Journal, Supplement Series. 2003 ; Vol. 149, No. 2. pp. 375-403.
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abstract = "We have mapped 63 regions forming high-mass stars in CS J = 5 → 4 using the CSO. The CS peak position was observed in C 34S J = 5 → 4 toward 57 cores and in 13CS J = 5 → 4 toward the nine brightest cores. The sample is a subset of a sample originally selected toward water masers; the selection on maser sources should favor sources in an early stage of evolution. The cores are located in the first and second Galactic quadrants with an average distance of 5.3 ± 3.7 kpc and were well detected with a median peak signal-to-noise ratio in the integrated intensity of 40. The integrated intensity of CS J = 5 → 4 correlates very well with the dust continuum emission at 350 μm. For 57 sufficiently isolated cores, a well-defined angular size (FWHM) was determined. The core radius (R CS), aspect ratio [(a/b) obs], virial mass (M vir), surface density (∑), and the luminosity in the CS J = 5 → 4 line (L(CS54)) are calculated. The distributions of size, virial mass, surface density, and luminosity are all peaked with a few cores skewed toward much larger values than the mean. The median values, μ 1/2, are as follows: μ 1/2 (R CS) = 0.32 pc, μ 1/2 ((a/b) obs) = 1.20, μ 1/2 (M vir) = 920 M ⊙, μ 1/2 (∑) = 0.60 g cm -2, μ 1/2 (L(CS54)) = 1.9 × 10 -2 L ⊙ and μ 1/2 (L bol/M vir) = 165 (L/M) ⊙. We find a weak correlation between C 34S line width and size, consistent with Δv ∼ R 0.3. The line widths are much higher than would be predicted by the usual relations between line width and size determined from regions of lower mass. These regions are very turbulent. The derived virial mass agrees within a factor of 2-3 with mass estimates from dust emission at 350 μm after corrections for the density structure are accounted for. The resulting cumulative mass spectrum of cores above 1000 M ⊙ can be approximated by a power law with a slope of about -0.9, steeper than that of clouds measured with tracers of lower density gas and close to that for the total masses of stars in OB associations. The median turbulent pressures are comparable to those in UCH II regions, and the pressures at small radii are similar to those in hypercompact H II regions (P/k ∼ 10 10 K cm -3). The filling factors for dense gas are substantial, and the median abundance of CS is about 10 -9. The ratio of bolometric luminosity to virial mass is much higher than the value found for molecular clouds as a whole, and the correlation of luminosity with mass is tighter.",
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T1 - A CS J = 5 → 4 mapping survey toward high-mass star-forming cores associated with water masers

AU - Shirley, Yancy L

AU - Evans, Neal J.

AU - Young, Kaisa E.

AU - Knez, Claudia

AU - Jaffe, Daniel T.

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N2 - We have mapped 63 regions forming high-mass stars in CS J = 5 → 4 using the CSO. The CS peak position was observed in C 34S J = 5 → 4 toward 57 cores and in 13CS J = 5 → 4 toward the nine brightest cores. The sample is a subset of a sample originally selected toward water masers; the selection on maser sources should favor sources in an early stage of evolution. The cores are located in the first and second Galactic quadrants with an average distance of 5.3 ± 3.7 kpc and were well detected with a median peak signal-to-noise ratio in the integrated intensity of 40. The integrated intensity of CS J = 5 → 4 correlates very well with the dust continuum emission at 350 μm. For 57 sufficiently isolated cores, a well-defined angular size (FWHM) was determined. The core radius (R CS), aspect ratio [(a/b) obs], virial mass (M vir), surface density (∑), and the luminosity in the CS J = 5 → 4 line (L(CS54)) are calculated. The distributions of size, virial mass, surface density, and luminosity are all peaked with a few cores skewed toward much larger values than the mean. The median values, μ 1/2, are as follows: μ 1/2 (R CS) = 0.32 pc, μ 1/2 ((a/b) obs) = 1.20, μ 1/2 (M vir) = 920 M ⊙, μ 1/2 (∑) = 0.60 g cm -2, μ 1/2 (L(CS54)) = 1.9 × 10 -2 L ⊙ and μ 1/2 (L bol/M vir) = 165 (L/M) ⊙. We find a weak correlation between C 34S line width and size, consistent with Δv ∼ R 0.3. The line widths are much higher than would be predicted by the usual relations between line width and size determined from regions of lower mass. These regions are very turbulent. The derived virial mass agrees within a factor of 2-3 with mass estimates from dust emission at 350 μm after corrections for the density structure are accounted for. The resulting cumulative mass spectrum of cores above 1000 M ⊙ can be approximated by a power law with a slope of about -0.9, steeper than that of clouds measured with tracers of lower density gas and close to that for the total masses of stars in OB associations. The median turbulent pressures are comparable to those in UCH II regions, and the pressures at small radii are similar to those in hypercompact H II regions (P/k ∼ 10 10 K cm -3). The filling factors for dense gas are substantial, and the median abundance of CS is about 10 -9. The ratio of bolometric luminosity to virial mass is much higher than the value found for molecular clouds as a whole, and the correlation of luminosity with mass is tighter.

AB - We have mapped 63 regions forming high-mass stars in CS J = 5 → 4 using the CSO. The CS peak position was observed in C 34S J = 5 → 4 toward 57 cores and in 13CS J = 5 → 4 toward the nine brightest cores. The sample is a subset of a sample originally selected toward water masers; the selection on maser sources should favor sources in an early stage of evolution. The cores are located in the first and second Galactic quadrants with an average distance of 5.3 ± 3.7 kpc and were well detected with a median peak signal-to-noise ratio in the integrated intensity of 40. The integrated intensity of CS J = 5 → 4 correlates very well with the dust continuum emission at 350 μm. For 57 sufficiently isolated cores, a well-defined angular size (FWHM) was determined. The core radius (R CS), aspect ratio [(a/b) obs], virial mass (M vir), surface density (∑), and the luminosity in the CS J = 5 → 4 line (L(CS54)) are calculated. The distributions of size, virial mass, surface density, and luminosity are all peaked with a few cores skewed toward much larger values than the mean. The median values, μ 1/2, are as follows: μ 1/2 (R CS) = 0.32 pc, μ 1/2 ((a/b) obs) = 1.20, μ 1/2 (M vir) = 920 M ⊙, μ 1/2 (∑) = 0.60 g cm -2, μ 1/2 (L(CS54)) = 1.9 × 10 -2 L ⊙ and μ 1/2 (L bol/M vir) = 165 (L/M) ⊙. We find a weak correlation between C 34S line width and size, consistent with Δv ∼ R 0.3. The line widths are much higher than would be predicted by the usual relations between line width and size determined from regions of lower mass. These regions are very turbulent. The derived virial mass agrees within a factor of 2-3 with mass estimates from dust emission at 350 μm after corrections for the density structure are accounted for. The resulting cumulative mass spectrum of cores above 1000 M ⊙ can be approximated by a power law with a slope of about -0.9, steeper than that of clouds measured with tracers of lower density gas and close to that for the total masses of stars in OB associations. The median turbulent pressures are comparable to those in UCH II regions, and the pressures at small radii are similar to those in hypercompact H II regions (P/k ∼ 10 10 K cm -3). The filling factors for dense gas are substantial, and the median abundance of CS is about 10 -9. The ratio of bolometric luminosity to virial mass is much higher than the value found for molecular clouds as a whole, and the correlation of luminosity with mass is tighter.

KW - Dust, extinction

KW - ISM: clouds

KW - ISM: molecules

KW - Stars: formation

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