Submillimetre Observations of Star-Forming Regions: Answers & Questions from Large-Area Mapping Surveys Doug Johnstone – NRC/HIA & U.Victoria 11/18/2018 SMA Conf 2005

Dust Emission vs. Starlight Submillimetre optical light 11/18/2018 SMA Conf 2005

Recipe for Dust Continuum Analysis Map submillimetre continuum Assume optically thin dust emission Estimate a temperature for the dust Deduce the column of dust and gas Identify structures (clumps, filaments) Compare with physical models Measure statistical quantities Reach conclusions (Just So stories?) 11/18/2018 SMA Conf 2005

The Ophiuchus Cloud in Visual Light 11/18/2018 SMA Conf 2005

The Ophiuchus Cloud in Extinction Cambresy et al. 1999 11/18/2018 SMA Conf 2005

The Ophiuchus Cloud in Millimetre Emission IRAM - 1.3 mm 0.13 Sq. Degree Map (~1 pc2) Significant Structure resolved cores Coherent regions Coincident with dense gas tracers (un)resolved clumps Located around cores Motte, Andre, & Neri 1998 11/18/2018 SMA Conf 2005

The Ophiuchus Cloud in Millimetre Emission Found 60 Clumps Clump Mass F’n Similar to Stellar MF Steeper than cloud MF Possible turn-over near 0.3 Msun Motte, Andre, & Neri 1998 11/18/2018 SMA Conf 2005

The Ophiuchus Cloud in SubMillimetre JCMT 850 m 0.25 Sq. Degree Map (~2 pc2) Filter long spatial scales in data to search for 55 clumps Separate clumps along minima (Williams et al.) Measure flux, size, and degree of concentration Identify with equilibrium structures Johnstone et al. 2000 11/18/2018 SMA Conf 2005

Clump Mass Vs. Radius Relation Clumps span typical mass range for stars Most clumps resolved Sensitivity limited Survey Most clumps appear stable Unstable to Collapse Comparison with CO (Kramer et al. 96) CO clumps are less dense, require non-thermal support CO clumps lie below our sensitivity threshold CO may `freeze-out’ in the dense submillimetre sources (green lines: resolution & sensitivity limits) (black lines: isobaric equilibria - unstable only above turn-over) 11/18/2018 SMA Conf 2005

Bonnor-Ebert Spheres Static isothermal clouds in equilibrium: pressure gradients balance gravity One-dimensional family of models: Physically - importance of self-gravity Clump mass versus clump temp. Observationally – degree of conc. Peak flux versus mean flux Three observables (area, flux, conc) yield three physical quantities (mass, temp., external pressure) Assumes dust temp similar to gas temp Requires knowledge of opacity ( = 0.01 cm2/gm) 11/18/2018 SMA Conf 2005

Physical Conditions in Clumps (Assuming hydrostatic equilibrium) Pressure at centre of the mol. cloud ~ 107 P/k Increasing  by 2 lowers T by ~ 2 Adding 50% turbulent pressure lowers T by ~ 2 11/18/2018 SMA Conf 2005

Cumulative Mass Spectrum Warning: Incomplete at low mass!! m = -1.5 Steep line: ~IMF Shallow line: ~ mol. Clouds 11/18/2018 SMA Conf 2005

Thoughts on the Mass Spectrum Good agreement between sub-mm surveys Similar results found for Orion B North and South Motte et al. (Ophiuchus, Orion B), Testi & Sargent (Serpens) Shape of clump mass function mimics that of stellar IMF low-mass turn-over may be due to sensitivity High-mass slope may be somewhat steeper than IMF Satisfying fits to static, stable, pressure-confined clumps Low temperatures and stellar-like masses required High external pressures consistent with depth in mol. Cloud 11/18/2018 SMA Conf 2005

Comments on the Stability of Clumps Are these clumps quasi-static or dynamic? The clumps may be modeled as hydrostatic entities Reasonable fit to the physical parameters Likely end result if the cloud loses support slowly In a few cases there exist complimentary line data (Friesen, Poster) Ambi-polar diffusion models predict smallscale clumping Central region where magnetic support removed Objects on their way to collapse Models of turbulent clouds also predict small-scale clumping Interfaces between waves, not long-lived! May approximate BE conditions (Ballesteros-Paredes et al 2003) 11/18/2018 SMA Conf 2005

Ophiuchus - 3.6, 4.5, 8.0 mm (IRAC) Johnstone et al. (2000) 11/18/2018 SMA Conf 2005 Allen et al. (2005)

COMPLETE -> Extinction Maps (Goodman, Poster) Extinction derived from 2Mass reddening data (Alves et al.) reveals both the diffuse envelope of the cloud and the dense core regions. Black contour denotes an Av ~ 5. 11/18/2018 SMA Conf 2005

Found only 2! Ophiuchus – JCMT 2004 Johnstone, Di Francesco, & Kirk 2004 In 2003 observed 4 sq. degrees (~30 pc2) 40 hours! Largest SCUBA map to date (independent pixels) Expect 100’s of new compact sources Found only 2! 11/18/2018 SMA Conf 2005

Is there a threshold Effect? Where do the clumps reside? 11/18/2018 SMA Conf 2005

Is there a threshold Effect? Where is the bulk mass of SCUBA sources? Does this Av threshold signify the importance of UV photons in maintaining the cloud ionization fraction, coupling the magnetic field to the gas, and preventing collapse (McKee 1989)? 11/18/2018 SMA Conf 2005

Significance of these Clumps Clumps represent ~2% mass of cloud Clumps represent ~20% mass of core Clumps live primarily at high (>10) Av Clumps have stellar IMF-like mass f’n Embedded stellar clusters have these same properties! (Lada and Lada 2003) 11/18/2018 SMA Conf 2005

Thermal Emission: Perseus Data from Hatchell et al. (2005) B5 IC348SW NGC 1333 B1 SCUBA observations of Ophiuchus containing new data IRAS 03282 L1448 57 objects Per 6 3.8 sq. degrees; 30 mJy/beam rms L1455 11/18/2018 SMA Conf 2005 Kirk, Johnstone, & Di Francesco (2005, in prep.)

Kirk, Johnstone, & Di Francesco (2005, in prep.) Thermal Emission + Extinction: Perseus SCUBA observations of Ophiuchus containing new data 11/18/2018 SMA Conf 2005 Kirk, Johnstone, & Di Francesco (2005, in prep.)

Is there a threshold Effect? Where is the bulk mass of SCUBA sources? Does this Av threshold signify the importance of UV photons in maintaining the cloud ionization fraction, coupling the magnetic field to the gas, and preventing collapse (McKee 1989)? 11/18/2018 SMA Conf 2005 Kirk, Johnstone, & Di Francesco (2005, in prep.)

Kirk, Johnstone, & Di Francesco (2005, in prep.) Triggering by 40 Persei? : Perseus SCUBA observations of Ophiuchus containing new data 11/18/2018 SMA Conf 2005 Kirk, Johnstone, & Di Francesco (2005, in prep.)

Kirk, Johnstone, & Di Francesco (2005, in prep.) Thermal Emission: Ophiuchus 5.5 sq. degrees; 40 mJy/beam rms L1709 L1688 L1689N SCUBA observations of Ophiuchus containing new data L1712 L1689S 11/18/2018 SMA Conf 2005 Kirk, Johnstone, & Di Francesco (2005, in prep.)

Kirk, Johnstone, & Di Francesco (2005, in prep.) Thermal Emission + Extinction: Ophiuchus SCUBA observations of Ophiuchus containing new data 11/18/2018 SMA Conf 2005 Kirk, Johnstone, & Di Francesco (2005, in prep.)

And the Cosmology Angle? Large Data Sets Provide Statistical Info Cloud mass and size distribution - large scales Clump mass and size distribution - small scales Clump locations - environment and clustering Structure - filamentary, ellipticity, direction Frequency of protostellar stages - Class -I, 0, I, II, III Polarization Angle - Magnetic Field Orientation Kinematic Information - CO line shapes. Spatial variation Any reasonable theory must reproduce these conditions! (Mac Low & Klessen 2004, Shu 1983, Basu & Ciolek 2004) 11/18/2018 SMA Conf 2005

Thermal Emission (2006++) CO clouds Imaging at 850 and 450 microns (>100 faster than SCUBA) Covering 10 sq. deg. to 2mJy (CO clouds) in <100 hrs Deep, unbiased, structure surveys within molecular clouds COMPLETE Revisited - COMPLETER 11/18/2018 SMA Conf 2005

Gould’s Belt - Nearby Star Formation Sites SCUBA2 Legacy Project: Mapping all star formation in Gould’s Belt, covering 700 square degrees, and sensitive to every Class O & I protostar and every L1544-like pre-stellar core within 0.5 kpc! 11/18/2018 SMA Conf 2005

Thermal Emission (2006++) Polarimetry (>1000 faster than SCUBA) Should detect magnetic geometry over much of cloud Important observational constraint for theories/simulations Further exploration of dust properties 11/18/2018 SMA Conf 2005

Thermal Emission (2006++) Fourier Transform Spectroscopy (>1000 faster than SCUBA) High spectral resolution - survey strong molecular lines Low spectral resolution - model SED through submillimetre Determine dust properties (ß± 0.1) (Friesen et al. 2005) 11/18/2018 SMA Conf 2005

The most significant problem for star formation is not forming stars, but rather not forming stars! http://cfa-www.harvard.edu/COMPLETE/ http://www.jach.hawaii.edu/JCMT/surveys 11/18/2018 SMA Conf 2005

11/18/2018 SMA Conf 2005