1. The Evolution of Massive Dense Cores Gary Fuller Holly Thomas Nicolas Peretto University of Manchester

2. Sources 850  m sources  Luminous, radio quiet IRAS sources (Sridharan et al. 2002)  Typical mass of core few x 100 M o, d~0.5 pc, n~10 5 cm -3 (Beuther etal 2002, Williams et al. 2004)  Forming range of objects IRAS20126, IRAS18182 IRAS05338, IRAS19410  But probably not forming IMF worth of stars Modelled to get n(r) and T(r) (Williams et al. 2005) Observations of CH 3 OH, CH 3 CN, CH 3 CCH, C 18 O & C 17 O J=2-1 (84 sources)

3. Line widths MC1 MCn Few sources dv(C 17 O)>3 km/s C 17 O and N 2 H + trace material kinematically distinct from CS  dv(CS) > dv(C 17 O)  Origin of CS line width? Turbulent core or effect of the source? CS J=3-2 Beuther etal (2002), N 2 H + Fuller et al (2005)

4. Modelling the C 17 O Spherical model  Adopt T(r), n(r), dv Match  m flux  Vary f(C 17 O) to match C 17 O line profile  Vary f(C 18 O)/f(C 17 O) to match C 18 O Simple model produces very reasonable fits C 17 O lines optically thin Constant C 17 O abundance  Range of f(C 17 O): (0.6-10)x10 -8  Well constrained (+/-10%)

5. C 17 O No models for most sources  Calculate beam averaged column densities  Match models within factor of 2 Factor 15 scatter in f(C 17 O) Can not change dust properties to reduce spread f(C 17 O) correlated with mass weighted temperature (van der Tak et al. 2000)  Freeze-out (Also Fontani et al. 2006)

6. Line width & Abundance All sources Extreme Sources MC1 MCn Large line width sources have lower abundances Top and bottom 30% of sources differ even more

7. MC1 Sources Broad CS lines Low C 17 O abundance Evidence for central heating  dust  hot cores species Maser No IR Nebulae Steep density profiles High M/L MCn Sources Narrow CS lines High C 17 O abundance No evidence of central heating  dust  hot core species rare Few masers IR Nebulae Shallow density profiles Low M/L

8. Central Heating Spectral index 850  m-450  m:  MC1: Mean spectral index 1.2  MCn: Mean spectral index 1.0 K-S test: differ at >99% Hot Core species:

9. MC1 Sources Broad CS lines Low C 17 O abundance Evidence for central heating  dust  hot cores species Maser No IR Nebulae Steep density profiles High M/L MCn Sources Narrow CS lines High C 17 O abundance No evidence of central heating  dust  hot core species rare Few masers IR Nebulae Shallow density profiles Low M/L

10. Masers & Nebulae Masers: NIR Nebulae:  MC1: 1 nebula (just, dv=3.1 km/s)  MCn: 7 nebulae Not due to differences in distances

11. MC1 Sources Broad CS lines Low C 17 O abundance Evidence for central heating  dust  hot cores species Maser No IR Nebulae Steep density profiles High M/L MCn Sources Narrow CS lines High C 17 O abundance No evidence of central heating  dust  hot core species rare Few masers IR Nebulae Shallow density profiles Low M/L

12. Density Profile Density power law index K-S Test: >99%

13. Mass and Luminosity MC1 sources tend to be higher mass and luminosity  But 12 MCn have L>10 3.5 L ⊙ But most significant difference is in the mass to luminosity ratio M/L(MC1) ~ 10 M/L (MCn)

14. MC1 Sources Broad CS lines Low C 17 O abundance Evidence for central heating  dust  hot cores species Maser No IR Nebulae Steep density profiles High M/L MCn Sources Narrow CS lines High C 17 O abundance No evidence of central heating  dust  hot core species rare Few masers IR Nebulae Shallow density profiles Low M/L Outflows: MC1:10 outflows, MCn : 7 outflows Not mass or luminosity difference

15. Evolution? MC1: Broad CS lines, low C 17 O abundance, central heating, steep density profiles MCn: Narrow CS lines, higher C 17 O abundance, no central heating, shallower density profiles  MC2: f(C 17 O)<4x10 -8, dv=2.4 km/s – 10 sources  MC3: f(C 17 O)>4x10 -8, dv=1.9 km/s – 9 sources All sources with IR nebulae in group MC2  Cleared central regions? Hot cores turned off, IR can escape. MC1: Lowest f(C 17 O) – core undisturbed. Larger M/L.  MC1 sources younger than MC2/3 sources  Evolution from steep to shallow density profile, hot core turn off, CS tracing interaction  Freeze-out/depletion: age of 2x10 5 years (Charnley et al 2001)

16. Future Directions Higher angular resolution Chemical tracers of freeze out Model more of the sources Larger and better matched samples  SCUBA-2 GPS survey  Methanol Multibeam survey Less evolved sources  Spitzer Dark Clouds

17. Rathborne et al. 2006: MSX 8 micron (colour) +1.2mm contour GLIMPSE Spitzer IRAC 8micron image, same source (MJy/sr) Column density map: cont 2 to 5x10 22 by 0.5x10 22 cm -2 Note: Star associated with densest core was not seen with MSX Younger Sources, High Resolution: Spitzer Dark Cloud