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A Search For Fragmentation in Starless Cores with ALMA

Explore evidence for turbulent fragmentation in starless cores using mm interferometers for high spatial resolution. Observations provide insights into core properties, mass, density, and potential protostars.

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A Search For Fragmentation in Starless Cores with ALMA

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  1. A Search For Fragmentation in Starless Cores with ALMA Scott Schnee (NRAO) Hector Arce, Tyler Bourke, Xuepeng Chen, James Di Francesco, Michael Dunham, Doug Johnstone, Stella Offner, Jaime Pineda, Daniel Price, Sarah Sadavoy 28-July-2014

  2. Turbulence Scales With Size Log line width (km/s) (Larson 1981) Log size of cloud (pc)

  3. Line Width is Constant on Small Scales Core properties d ≈ 0.1 pc n ≈ 104-6 cm-3 T ≈ 10 K M ≈ 1-10 M cs≈ 0.2 km/s σ ≈ 0.1-0.2 km/s Does fragmentation continue down to smaller scales? (Pineda et al. 2011)

  4. Project Idea • Choose a promising sample of starless cores • Look for evidence for fragmentation • Yes: support for turbulent fragmentation • No: support for disk fragmentation? • Observe cores with mm interferometers • Provides high spatial resolution • Dust continuum provides unambiguous mass tracer

  5. CARMA – Big Pine, California Antenna numbers, sizes 6 x 10.4m, 9 x 6.1m, 8 x 3.5m

  6. Sample 1 • 3mm continuum survey of 11 starless cores • Chosen from Enoch et al. (2006; 2008) Bolocam 1.1mm survey of Perseus • Starless status based on Spitzer NIR-MIR data • Peak fluxes >200 mJy beam-1 in Bolocam data • Median mass of 1.47 M⊙ • Median density of 3.2×105 cm−3

  7. Sample 1 • Observed with CARMA • 3mm continuum • 5” resolution • 40” largest angular scale • Follow-up observations with • CARMA (3mm spectral lines) • SMA (1.3mm continuum, CO J=2-1) • Spitzer (70 μm continuum)

  8. CARMA & SZA 3mm Continuum 0.01 pc (Schnee et al. 2010)

  9. Perbo58 and Perbo 45 as Protostars Greyscale and Green contours: 1.3mm continuum emission Red and blue contours: Red and blue-shifted CO (2-1) emission (0.3-7.3 & 7.3-14.3 km/s) (Dunham, Chen, Arce, Bourke, Schnee, & Enoch 2011) (also: Schnee, Di Francesco, Enoch, Friesen, Johnstone, & Sadavoy 2012)

  10. SMA – Mauna Kea, Hawaii Antenna numbers, sizes 8 x 6m

  11. Sample 2 • 1.3mm continuum and CO (2-1) survey of 5 starless cores • Chosen from Sadavoy et al. (2010) SCUBA 850 μm survey of nearby molecular clouds • Starless status based on Spitzer NIR-MIR data • Observed with SMA in compact configuration • 1.3mm continuum • 12CO (2-1), 13CO (2-1), C18O (2-1), N2D+ (3-2) • 3” resolution • 8” largest angular scale

  12. Per 8 as a Protostar 12CO and continuum C18O and continuum Black: 1.3mm continuum (0.1 – 0.5 Jy/beam) Red: 12CO (2-1) Tint 9 km/s ≤ v ≤ 18 km/s Blue: 12CO (2-1) Tint -2 km/s ≤ v ≤ 5 km/s Color contours at 3, 6, …, 21 K km/s Black: C18O Tint in intervals of 2 K km/s Color: C18O VLSR (Schnee, Sadavoy, Di Francesco, Johnstone & Wei 2012)

  13. ALMA – Atacama Desert, Chile Antenna numbers, sizes 32 x 12m, 9 x 7m (Cycle 1) 54 x 12m, 12 x 7m (Full Science)

  14. Sample 3 • 3mm continuum and CO (1-0) survey of 72 starless and protostellar cores • Chosen from Belloche et al. (2011) LABOCA 1mm survey of Chamaeleon I • Starless / protostellar status based on NIR data • Observed with ALMA in Cycle 1 • 3” resolution • 25” largest angular scale

  15. CARMA, SMA, and ALMA Projects

  16. ALMA 3mm Continuum Every Starless Core 0.01 pc (Schnee et al. in prep.)

  17. ALMA 3mm Continuum Double source Single source 0.01 pc (Schnee et al. in prep.)

  18. ALMA Results • Starless Cores • No continuum detection • FHSC candidate Chamaeleon-MMS1 • Extended 3mm continuum detected • Protostars • 19 cores with 3mm continuum (point-like) • 25 total protostellar candidates detected • new YSO candidates • 7 not found in Dunham et al. (2013) • 2 not found in Winston et al. (2012) (Schnee et al. in prep.)

  19. Simulations of Turbulent Fragmentation in Starless Cores Simulated ALMA Full Science + ACA observations (Offner, Capodilupo, Schnee, & Goodman 2011)

  20. Summary • Observational evidence for fragmentation in starless cores? – Not yet. • Low levels of turbulence in starless cores leads to low levels of fragmentation • Multiplicity set at protostellar stage? Disk fragmentation? • More sensitive observations needed? • Interferometric observations in the millimeter or submillimeter can find hidden protostars • Up to 20% of “starless” cores are actually protostars

  21. L1451-mm: Another Hidden Protostar (Pineda, Arce, Schnee et al. 2011)

  22. L1451-mm: Another Hidden Protostar Black Contours: SMA 1.3mm continuum Blue Contours: Blue-shifted CO (2-1) 1.9-3.7 km/s Red Contours: Red-shifted CO (2-1) 5.3 – 6.9 km/s (Pineda, Arce, Schnee et al. 2011)

  23. Starless Cores Are Not Detected by CARMA Offset from (0,0) position given in Enoch et al. (2006) Derived from Gaussian fit to flux distribution Deconvolved using the synthesized beam For non-detections, 3σ upper limits to a point source are given Does not include SZA data, so some 3mm emission is resolved out (Schnee et al. 2010)

  24. Sample 2 • 3.2 M⊙ ≤ M ≤ 8.1 M⊙ • 2.1 ≤ M/MJ ≤ 4.9

  25. Starless Cores Are Not Detected by SMA • 3σ upper limits for non-detections < 0.02 M⊙ (Schnee, Sadavoy, Di Francesco, Johnstone & Wei 2012)

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