The initial conditions of clustered star formation. i. nh3 observations of dense cores in ophiuchus

R. K. Friesen, J. Di Francesco, Yancy L Shirley, P. C. Myers

Research output: Contribution to journalArticle

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Abstract

We present combined interferometer and single dish telescope data of NH3 (J, K) = (1,1) and (2,2) emission toward the clustered star forming Ophiuchus B, C, and F Cores at high spatial resolution (1200AU) using the Australia Telescope Compact Array, the Very Large Array, and the Green Bank Telescope. While the large-scale features of the NH3 (1,1) integrated intensity appear similar to 850μm continuum emission maps of the Cores, on 15″ (1800AU) scales we find significant discrepancies between the dense gas tracers in Oph B, but good correspondence in Oph C and F. Using the CLUMPFIND structure identifying algorithm, we identify 15 NH3 clumps in Oph B, and three each in Oph C and F. Only five of the Oph B NH3 clumps are coincident within 30″ (3600AU) of a submillimeter clump. We find v LSR varies little across any of the cores, and additionally varies by only 1.5km s-1 between them. The observed NH3 line widths within the Oph B and F Cores are generally large and often mildly supersonic, while Oph C is characterized by narrow line widths which decrease to nearly thermal values. We find several regions of localized narrow line emission (Δv ≲ 0.4 km s-1), some of which are associated with NH3 clumps. We derive the kinetic temperatures of the gas, and find they are remarkably constant across Oph B and F, with a warmer mean value (TK = 15 K) than typically found in isolated regions and consistent with previous results in clustered regions. Oph C, however, has a mean T K = 12 K, decreasing to a minimum TK = 9.4 K toward the submillimeter continuum peak, similar to previous studies of isolated starless clumps. There is no significant difference in temperature toward protostars embedded in the Cores. NH3 column densities, N(NH3), and abundances, X(NH3), are similar to previous work in other nearby molecular clouds. We find evidence for a decrease in X(NH3) with increasing N(H2) in Oph B2 and C, suggesting the NH3 emission may not be tracing well the densest core gas.

Original languageEnglish (US)
Pages (from-to)1457-1480
Number of pages24
JournalAstrophysical Journal
Volume697
Issue number2
DOIs
StatePublished - 2009

Fingerprint

clumps
star formation
gas
telescopes
interferometer
gases
continuums
spatial resolution
Very Large Array (VLA)
protostars
parabolic reflectors
temperature
tracer
tracing
molecular clouds
kinetics
tracers
interferometers
stars
high resolution

Keywords

  • ISM: kinematics and dynamics
  • ISM: molecules
  • ISM: structure
  • Radio lines: ISM
  • Stars: formation

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

The initial conditions of clustered star formation. i. nh3 observations of dense cores in ophiuchus. / Friesen, R. K.; Di Francesco, J.; Shirley, Yancy L; Myers, P. C.

In: Astrophysical Journal, Vol. 697, No. 2, 2009, p. 1457-1480.

Research output: Contribution to journalArticle

Friesen, R. K. ; Di Francesco, J. ; Shirley, Yancy L ; Myers, P. C. / The initial conditions of clustered star formation. i. nh3 observations of dense cores in ophiuchus. In: Astrophysical Journal. 2009 ; Vol. 697, No. 2. pp. 1457-1480.
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N2 - We present combined interferometer and single dish telescope data of NH3 (J, K) = (1,1) and (2,2) emission toward the clustered star forming Ophiuchus B, C, and F Cores at high spatial resolution (1200AU) using the Australia Telescope Compact Array, the Very Large Array, and the Green Bank Telescope. While the large-scale features of the NH3 (1,1) integrated intensity appear similar to 850μm continuum emission maps of the Cores, on 15″ (1800AU) scales we find significant discrepancies between the dense gas tracers in Oph B, but good correspondence in Oph C and F. Using the CLUMPFIND structure identifying algorithm, we identify 15 NH3 clumps in Oph B, and three each in Oph C and F. Only five of the Oph B NH3 clumps are coincident within 30″ (3600AU) of a submillimeter clump. We find v LSR varies little across any of the cores, and additionally varies by only 1.5km s-1 between them. The observed NH3 line widths within the Oph B and F Cores are generally large and often mildly supersonic, while Oph C is characterized by narrow line widths which decrease to nearly thermal values. We find several regions of localized narrow line emission (Δv ≲ 0.4 km s-1), some of which are associated with NH3 clumps. We derive the kinetic temperatures of the gas, and find they are remarkably constant across Oph B and F, with a warmer mean value (TK = 15 K) than typically found in isolated regions and consistent with previous results in clustered regions. Oph C, however, has a mean T K = 12 K, decreasing to a minimum TK = 9.4 K toward the submillimeter continuum peak, similar to previous studies of isolated starless clumps. There is no significant difference in temperature toward protostars embedded in the Cores. NH3 column densities, N(NH3), and abundances, X(NH3), are similar to previous work in other nearby molecular clouds. We find evidence for a decrease in X(NH3) with increasing N(H2) in Oph B2 and C, suggesting the NH3 emission may not be tracing well the densest core gas.

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