How do massive stars form ? A comparison of model tracks with Herschel data

1. How do massive stars form?Acomparison of model tracks with Herschel data Michael D Smith CAPS University of Kent Available at: http://astro.kent.ac.uk/mds/capsule.pdf September 2013

2. Late stage: Rosette in optical AFGL 2591 Rosette Nebula, Travis Rector, KPNO

3. Early emerging: near-infrared, with outflows Li et al 2008 ApJL679, L101

4. Near-Infrared Interferometry: Preibisch, Weigelt et al. S140 IRS 3 S140 IRS 1 R Mon IRAS 23151+5912 AFGL 2591 K3-50 A Mon R2

5. Numerical telescope: K-band imaging reflected shock AFGL 2591 total

6. Approach 1: HMCs to UCHii to Hii AdaptedfromGorti & Hollenbach 2002

7. Approach 2: IRDCs, ALMA, to Herschel cool cores IRDCs: initial states imprinted - SDC335 Accelerated accretion Peretto et al 2013, 555, A112 a) Mid-infrared Spitzer composite image (red: 8 μm; green: 4.5 μm; blue: 3.6 μm) b) ALMA-only image of the N2H+(1−0) integrated intensity, c) ALMA N2H+(1−0) velocity field

8. Approach 3: two stage stitch-up Molinari et al 2008 noted: lack of diagnostic tools. Stage 1: Accretion phase Stage 2: Clean up, cluster forms + sweep out Early protostar: Accelerated accretion model (Mckee & Tan 2003) Clump mass and final star mass simply related): Accelerated accretion

9. Approach 3: two stage stitch-up Molinari et al 2008 tracks from SED to mm dust masses Diagnostic tools: Accelerated accretion Lbol-Mclump-Tbol Lbol/Lsolar Mclump/Msolar

10. Alternative evolutions Dark cloud fragments into cores/envelopes. Envelope accretion: from fixed bound envelope, bursts etc Global collapse. Accretion evolutions: from clumps, competitive, turbulent. Cores and protostars grow simultaneously Mergers, harrassment, cannabolism, disintegration

11. Issues for Massive Stars Most massive? Radiation feedback problem Environment? Cluster-star evolutions? Efficiency problem. Global collapse or fragmentation? IMF: Feedback- radiation and outflow phases? EUV problem Separate accretion luminosity from Interior luminosity? Bursts? Luminosity problem Two phases; accretion followed by clean-up? Dual evolution?

12. Recent Simulations Krumholz et al. 2007 , 2009 ; Peters et al. 2010a , 2011 ; Kuiper et al. 2010a , 2011 , 2012 ; Cunningham et al. 2011 ; Dale & Bonnell2011 Kuiper & Yorke 2013: 2D RHD, core only: spherical solid-body rotation + protostellar structure. Conclusion: diverse, depends on disk formation, bloating and feedback coordination.

13. Objective: Model for Massive Stars Piece together evolutionary algorithms for the protostellar structure, the environment, the inflow and the radiation feedback. The framework requires the accretion rate from the clump to be specified. We investigate constant, decelerating and accelerating accretion rate scenarios. We consider both hot and cold accretion, identified with spherical free-fall and disk accretion, respectively.

14. Objective: Model for Massive Stars Piece together evolutionary algorithms for the protostellar structure, the environment, the inflow and the radiation feedback. The framework requires the accretion rate from the clump to be specified. We investigate constant, decelerating and accelerating accretion rate scenarios. We consider both hot and cold accretion, identified with spherical free-fall and disk accretion, respectively.

15. Cold or Hot Accretion? Kuiper & Yorke 2013 ApJ 772 Hosokawa, Omukai, Yorke 2009, 2010

16. The protostar: radius Stellar radius as mass accumulates (I) adiabatic, (II) swelling/bloating, (III) Kelvin–Helmholtz contraction, and (IV) main sequence Hot accretion Cold accretion

17. The protostar: luminosity Origin Luminosity as mass accumulates (cold)

18. The protostar: adaption Assumed mass accretion rates + interpolation scheme

19. The Low-Mass Scheme: Construction Clump Envelope Accretion Disk Protostars • mass conservation • prescribed accretion rate • bifurcation coefficient • jet speed ~ escape speed Bipolar Outflow Jets • Evolution: • systematic and simultaneous • ProtostarL(Bolometric) • Jet L(Shock) • Outflow Momentum (Thrust) • Clump/Envelope Mass • Class Temperature • Disk Infrared excess

20. The Capsule Scheme: Construction Lyman Flux Radio: H II region Radiative Flux Clump Envelope Accretion Disc Protostar Bipolar Outflow Jets thermal radio jets H2 shocks

21. Capsule Flow Chart

22. The clump mass, isotherms + Herschel data Origin Luminosity as clump mass declines Constant slow accretion Accelerated accretion ( Data: Elia et al 2010), Hi-GAL Accelerated accretion Power Law deceleration (Data: Molinari et al 2008)

23. Bolometric Temperature Origin Distance dotted line = accelerated accretion Herschel: <20K: 0.463 <30K: 0.832 <50K: 0.950

24. Bolometric Temperature Clump = cluster x 2 Clump = cluster x 6

25. Lbol-Mclump-Tbol results We find that accelerated accretion is not favoured on the basis of the often-used diagnostic diagram which correlates the bolometric luminosity and clump mass. Instead, source counts as a function of the bolometric temperature can distinguish the accretion mode. Specifically, accelerated accretion yields a relatively high number of low-temperature objects. On this basis, we demonstrate that evolutionary tracks to fit Herschel Space Telescope data require the generated stars to be three to four times less massive than in previous interpretations. This is consistent with star formation efficiencies of 10-20%

26. The clump mass, isotherms + Herschel data Or Luminosity as clump mass declines: massive clumps

27. The Lyman Flux (ATCA 18 GHz data) N(Ly), Lyman Continuum photons/s Sanchez-Monge et al., 2013, A&A 550, A21 Orig Accelerated accretion Lbol/LsunBolometric Luminosity

28. The Lyman Flux Origin D COLD accretion + Hot Spots (75%, 5% area) Distributed accretion Accretion hotspots Orig Constant accretion rate

29. The Lyman Flux: summary Neither spherical nor disk accretion can explain the high radio luminosities of many protostars. Nevertheless, we discover a solution in which the extreme ultraviolet flux needed to explain the radio emission is produced if the accretion flow is via free-fall on to hot spots covering less than 20% of the surface area. Moreover, the protostar must be compact, and so has formed through cold accretion. This suggest that massive stars form via gas accretion through disks which, in the phase before the star bloats, download their mass via magnetic flux tubes on to the protostar.

30. Jet speed = keplerian speed Or Different constant accretion rates………..

31. Michael D. Smith - Accretion Discs What next? • Disk – planet formation • Binary formation, mass transfer etc • Mass outflows v. radiation feedback • Feedback routes • Outbursts • Thermal radio jets • ???

32. Thanks For Listening! ANY QUESTIONS?

33. Low-Mass ProtostellarTracks • X-Axis: Luminosity • Y-Axis: Jet Power • Tracks/Arrows: the scheme • Diagonalline: • Class 0/I border • Data: ISO FIR + NIR (Stanke) • Above: Class 0 • Under: Class 1

34. Michael D. Smith - Accretion Discs Disk evolution • Column density as function of radius and time: (r,t) • Assume accretion rate from envelope • Assume entire star (+ jets) is supplied through disc • Angular momentum transport: • - turbulent viscosity: `alpha’ prescription • - tidal torques: Toomre Q parameterisation • Class 0 stage: very abrupt evolution?? Test…… • …to create a One Solar Mass star

35. Michael D. Smith - Accretion Discs The envelope-disc connection; slow inflow 50,000 yr: blue 500,000 yr: green 2,000,000 yr: red Peak accretion at 100,000 yr Accrate 3.5 x 10-6Msun/yr Viscosity alpha = 0.1

36. Michael D. Smith - Accretion Discs The envelope-disc connection; slow inflow; low alpha Peak accretion at 200,000 yr Accrate 3.5 x 10-6Msun/yr Viscosity alpha = 0.01 50,000 yr: blue 500,000 yr: green 2,000,000 yr: red