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Identification of Super-Jeans Cores

Identification of Super-Jeans Cores. James Di Francesco (thanks to S. Sadavoy , S. Chitsazzadeh , S. Mairs , S. Schnee , M. Chen, R. Friesen, H. Kirk, and the Herschel & JCMT GBS Teams). The Jeans Mass. maximum mass M J in radius R J that is stable spherical, non-rotating,

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Identification of Super-Jeans Cores

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  1. Identification of Super-Jeans Cores James Di Francesco (thanks to S. Sadavoy, S. Chitsazzadeh, S. Mairs, S. Schnee, M. Chen, R. Friesen, H. Kirk, and the Herschel & JCMT GBS Teams)

  2. The Jeans Mass • maximum mass MJ in • radius RJ that is stable • spherical, non-rotating, • non-magnetic, etc. • serves as a benchmark RJ MJ (MJ /M) =2.9(T /10 K)1.5 (n /104 cm-3)-0.5 = 1.9 (T / 10 K) (RJ / 0.07 pc) & COLD COMPACT

  3. Detecting Super-Jeans Cores Ophiuchus (L1689-S) • Starless super-Jeans cores • are very promising sites to • study the onset of collapse • Wide-field continuum • surveys still the best way • to locate such cores • SCUBA Legacy Catalogues • at 850 μm, Herschel, etc. ~0.1 pc SCUBA 850 μm Nutter, Ward-Thompson & André (2006); Di Francesco et al. (2008)

  4. Observed Super-Jeans Cores Contours: 850 μm (SCUBA) Greyscale: 8 μm (IRAC) • starless • starless • “undetermined” Sadavoy, Di Francesco, & Johnstone (2010) • Sadavoy et al. (2010) examined 729 SCUBA cores • found in Ophiuchus, Perseus, Taurus, & Orion

  5. “Starless” Super-Jeans Cores • only 3 starless and • 11 “undetermined” 2 4.5 Sadavoy, Di Francesco, & Johnstone (2010)

  6. “Starless” Super-Jeans Cores Sadavoy, Di Francesco, & Johnstone (2010)

  7. “Starless” SJ Cores are Rare • red = 50% tff • green = 80% tff • blue = 100 % tff • once sink forms, • envelope accretes • very rapidly Offner et al. (2013): Rm6 simulation at 0.8 tff ; no feedback or magnetic fields Mairs et al. (2014)

  8. “Starless” SJ Cores are Not Fragmented? • Schnee et al. (2012) • SMA/CARMA study • of 5 starless SJ cores • 4 non-detections • consistent with • starless core models • no fragments seen • either: ALMA?  Models + CASA Schnee et al. (2012); Crapsi et al. (2007)

  9. SJ Cores need better characterization JCMT We need: • More examples • Better mass estimates • (Tdust + κν) • Gas temperatures • Kinematic studies • Insights into other • support mechanisms • (turbulence + B) GBT Herschel

  10. More Examples: JCMT GBS • SCUBA-2 mapping • of nearby SF clouds: • Gould Belt Survey • covers 24 deg2 of high • AV areas at 850 μm to • 1 σ ≈ 3 mJy beam-1 • due to spatial filtering, • maps reveal compact • structures (100’s of • cores and filaments) Aquila Rift W40 Serpens South SCUBA-2 850 μm Image by R. Friesen; Hatchell et al. (2014, in prep)

  11. More Examples: JCMT GBS Ophiuchus L1689 L1688 SCUBA-2 850 μm Image by R. Friesen; Pattle et al. (2014, in prep)

  12. More Examples: JCMT GBS Orion A South • 5 sigma contour • “islands” SCUBA-2 850 μm S. Mairs et al. (2014, in prep)

  13. More Examples: JCMT GBS • “fragments” • “islands” Zoom-in of Orion A South at 850 μm S. Mairs et al. (2014, in prep)

  14. More Examples: JCMT GBS S. Mairs et al. (2014, in prep)

  15. Better Mass Estimates: JCMT Perseus-NGC 1333 DSS2-infrared SCUBA-2 850 μm Image by R. Friesen; Chen et al. (2014, in prep)

  16. Better Mass Estimates: JCMT Better Tdust & κν: JCMT + Herschel κν = κo(ν/νo)β; κo= 0.1 cm2 g-1 at 1000 GHz (Hillenbrand 1983) β = 1.5, 2.0, 2.5 SCUBA-2 850 μm band Herschel Bands Sadavoy et al. (2013) • Different values of β can fit Herschel data well • SCUBA-2 data can be used to constrain β(+ Tdust)

  17. Better Tdust & κν: JCMT + Herschel • Combine spatially filtered Herschel data + SCUBA-2 • data to determine β+ Tdust of compact structures Filtered 250 μm data Residual 250 μm data Perseus – B1 Sadavoy et al. (2013)

  18. Better Tdust & κν: JCMT + Herschel Perseus - NGC 1333 Chen et al. (2014, in prep)

  19. Better Tdust & κν: JCMT + Herschel Perseus - NGC 1333 • what about κo?? Chen et al. (2014, in prep)

  20. Line Studies of SJ Cores • NH3 : • ncr ~ 104 cm-3 • traces continuum • hyperfine structure • -> low optical depth • gas temperatures • σNT/cs -> coherence? • kinematics KFPA + VEGAS now available at GBT! Oph B clumps NH3 (1,1) GBT+ VLA Friesen et al. (2019)

  21. Gas Temperatures (line-of-sight) • Chitsazzadeh et al. : • examining isolated • cores on the verge • of collapse with GBT • <Tk>los ~ 9.5 ± 0.6 K • σNT/cs ~ 0.25 – 0.9 ; • internal velocities • dominated by thermal • motions L694-2 L1521F L429 L429-E L1517B Chitsazzadeh et al. (2014, in prep)

  22. Gas Temperatures (3D models) L694-2 L1521F Chitsazzadeh et al. (2014, in prep) • combined GBT + JVLA data of L694-2 & L1521F • used NH3-derived (los) Tk and continuum data to • fit column density structure and with B-E sphere • used MOLLIE (Keto & Rybicki 2010) to model NH3

  23. Gas Temperatures (3D models) Chitsazzadeh et al. (2014, in prep)

  24. Gas Kinematics: L1689-SMM16 Ophiuchus (L1689-S) SMM16 Chitsazzadeh et al. (2014, in press) • NH3-derived (los) temperatures, • continuum data + BE sphere fit: • (M/MJ) = 4.7/1.6 M = 3.4 • no Spitzer or Herschel 70 μm SCUBA 850 μm

  25. Gas Kinematics: L1689-SMM16 • asymmetrically • red HNC and • HCN profiles: • expansion of • outer layers Hill5 fits • evenly spaced • maxima and minima • of δV(thick−thin): • oscillations? • collapse not uniform? Chitsazzadeh et al. (2014, in press)

  26. Summary • The Jeans Mass provides a benchmark for • identifying starless cores on the verge of collapse • [Filtered?] continuum surveys are best way for • locating more super-Jeans core candidates • JCMT + Herschel data yield better core mass • estimates, improving super-Jeans identification • NH3 line observations reveal internal support, • temperature profiles • Other lines (HCN) can probe contraction: • super-Jeans ≠ core contraction -> oscillations? • New instruments = new probes of internal super- • Jeans core structure and evolution

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