Star and Planet Formation

1. Star and Planet Formation Neal Evans The University of Texas at Austin

2. Star Formation in Galaxies Antennae: galaxy merger. Visible (HST) showscopious star formation, but misses the main show. Most intense star formation in obscured region traced by CO. CO(1-0): OVRO Whitmore et al. (1999) Wilson et al. (2000)

3. New Views are Coming The Archive is open: http://ssc.spitzer.caltech.edu/

4. Star Formation/Galaxy Formation • Key part of galaxy formation • Properties of molecular clouds in other galaxies • Connect studies of distant galaxies to MW • Collective, clustered, massive SF • Molecular line probes of high density • Dust continuum emission • Insights into high-z starbursts

5. Star Formation traced by HCN Relation between LIR and LCO becomes non-linear for very high LIR. Stays linear for LHCN. J. Wu et al. Data from Gao and Solomon 2003.

6. Relation Same for Cores in MW LHCN or LCS for cores in MW also linear with LIR. (For LIR > 104 Lsun) These points are for HCN 3-2 and CS 5-4. Same line as HCN 3-2 in galaxies. Parallel to HCN 1-0 relation for starbursts. Checking HCN 1-0 in MW. J Wu et al. In prep.

7. What probes can we use? • Dust • Extinction of background stars • Probe Nd(b), Bperp • Emission in infrared to millimeter • Probe Td( r), Nd(b), Bperp • Problem: need to know dust properties • Molecules • Emission or absorption (infrared to radio) • Probe TK( r), n( r), v( r), Bpar • Problem: chemistry

8. Studies of High Mass Regions • Many Detailed Studies • Ho, Zhang, … • Surveys • van der Tak et al. (2000) (14 sources) • Beuther et al. (2002) (69 sources) • Survey of water masers for CS • CS survey Plume et al. (1991, 1997) • Dense: <log n> = 5.9 • Maps of 51 in 350 micron dust emission • Mueller et al. 2002 • Maps of 63 in CS J = 5–4 emission • Shirley et al. 2003

9. Luminosity versus Mass Log Luminosity vs. Log M red line: masses of dense cores from dust Log L = 1.9 + log M blue line: masses of GMCs from CO Log L = 0.6 + log M L/M much higher for dense cores than for whole GMCs. Mueller et al. (2002)

10. Linewidth versus Size Correlation is weak. Linewidths are 4-5 times larger than in samples of lower mass cores. Massive clusters form in regions of high turbulence, pressure. Shirley et al. 2003

11. Cumulative Mass Function Incomplete below 103 Msun. Fit to higher mass bins gives slope of about –0.93. Steeper than that of CO clouds or clumps (–0.5 on this plot). Similar to that of clusters, associations (Massey et al. 1995) in our Galaxy and in Antennae (Fall et al. 2004). Shirley et al. 2003

12. Massive Cores: Gross Properties • Massive, Dense, Turbulent • Mass distribution closer to clusters, stars than GMC • Much more turbulent than low mass cores • A model for starbursts? • Luminosity correlates well with core mass • Less scatter than for GMCs as a whole • L/M much higher than for GMCs as a whole • L/Mdust ~ 1.4 x 104 Lsun/Msun ~ high-z starbursts • L/L(HCN) similar to starbursts • Starburst: all gas like dense cores?

13. Hints of Dynamics A significant fraction of the massive core sample show self-reversed, blue-skewed line profiles in lines of HCN 3-2. Of 18 double-peaked profiles, 11 are blue, 3 are red. Suggests inflow motions of overall core. Vin ~ 1 to 4 km/s over radii of 0.3 to 1.5 pc. J. Wu et al. (2003)

14. Open Questions for ALMA • Studies of gas, dust, high n tracers in galaxies • Detailed structure of massive cores • Can we separate into fragments/clusters? • Simulations predicting properties • Understand IMF? • See SMA early results as preview for ALMA • Can we study dynamics? • Test inward motion hints in single-dish spectra • Separate dynamics of fragments • Evolution of dust, ice, gas-phase chemistry • Combine ALMA with Spitzer, SOFIA, Herschel, …

15. What do we need? • High resolution • High dynamic range, image fidelity • Bright, but complex, sources • Flexible correlator • Very rich spectrum, need many diagnostics • Full complement of receivers • For exgal clouds, excellent sensitivity

16. Low Mass vs. High Mass • Low Mass star formation • “Isolated” (time to form < time to interact) • Low turbulence (less than thermal support) • Nearby (~ 100 pc) • High Mass star formation • “Clustered” • Time to form may exceed time to interact • Turbulence >> thermal • More distant (>400 pc)

17. High vs. Low Early Conditions n( r) = nf (r/rf)–p ; rf = 1000 AU

18. Even “Isolated” SF Clusters Taurus Molecular Cloud Prototypical region of “Isolated” star formation Myers 1987

19. But Not Nearly as Much Orion Nebula Cluster >1000 stars 2MASS image Taurus Cloud at same scale 4 dense cores, 4 obscured stars ~15 T Tauri stars 1 pc

20. The Basic Features Envelope Disk Protostar Jet/wind/outflow T. Greene

21. Studies of the Envelope • All quantities vary along line of sight • Dust temperature, Td( r) • Heating from outside, later inside • Gas temperature, TK( r) • Gas-dust collisions, CRs, PE heating • Density, n(r), predicted to vary • Velocity, v(r), connected to density • Abundance, X(r), varies • Photodissociation, freeze-out, desorption

23. An Evolutionary Model • A physical model from theory • Sequence of Bonnor-Ebert spheres of increasing nc • e.g., Shu (1977) “Inside-out collapse” • Calculate luminosity of central star+disk • Dust temperature through envelope • Gas temperature • Chemical abundances • Follow gas as it falls, using evolving conditions • Line Profiles including all effects

24. Theory gives n(r,t), v(r,t) t<0: Series of Bonnor-Ebert spheres t>0: Inside-out collapse model (Shu 1977) C. Young

25. L(t) from Accretion, Contraction L(t) calculated. First accretion. First onto large (5 AU) surface (first hydrostatic core). Then onto PMS star with R = 3 Rsun, after 20,000 to 50,000 yr. And onto disk. Prescriptions from Adams and Shu. Contraction luminosity and deuterium burning dominates after t ~100,000 yr. C. Young and Evans, in prep.

26. Evolution of Dust Tracers Assumes distance of 140 pc and typical telescope properties. C. Young and Evans, in prep.

27. Calculate Gas Temperature Use gas energetics code (Doty) with gas-dust collisions, cosmic rays, photoelectric heating, gas cooling. Calculate TK( r, t). C. Young and J. Lee et al.

28. Calculate Abundances Chemical code by E. Bergin 198 time steps of varying length, depending on need. Medium sized network with 80 species, 800 reactions. Follows 512 gas parcels. Includes freeze-out onto grains and desorption due to thermal, CR, photo effects. No reactions on grains. Assume binding energy on silicates for this case. J. Lee et al. In prep

29. Calculate Line Profiles Line profiles calculated from Monte Carlo plus virtual telescope codes. Includes collisional excitation, trapping. Variations in density, temperature, abundance, velocity are included. Assumes distance of 140 pc and typical telescope properties. J. Lee et al. In prep J. Lee et al. In prep

30. A Closer Look Lines of HCN (J = 1–0). Shown for four times. Top plot with 50” resolution. Bottom plot with 5” resolution. ALMA will probe the desorption wave. J. Lee et al. In prep

31. Evidence for Infall Good evidence in a few. (e.g., Zhou et al. 1993) Surveys indicate infall is common at early stages. Gregersen et al. 1997, 2000 Mardones et al. 1997

32. Observing Infall with ALMA • A key observation is to observe the infalling gas in redshiftedabsorption against the background protostar • Very high spectral resolution (<0.1 km/s) is required • High sensitivity to observe in absorption against disk.

33. Low Mass Cores: Gross Properties • Molecular cloud necessary, not sufficient • High density (n>104 cm–3) • Low turbulence • Centrally peaked density distribution • Power law slope ~ high mass • Fiducial density ~ 100 times lower • Complex chemistry, dynamics even in 1D • Evidence for infall seen, but hard to study • Outflow starts early, strong effect on lines • Rotation on small scales

34. Open Questions • Initial conditions • Cloud/core interaction • Trace conditions in core closer to center • Inward motions before point source? • Timescales for stages • Establish existence and nature of infall • Inverse P-Cygni profiles against disks • Chemo-dynamical studies • Envelope-Disk transition • Inner flow in envelope • Outflow dynamics • Nature of interaction with ambient medium

35. Sub-stellar Objects • Brown dwarfs, free-floating planets, … • BDs clearly exist, clearly have disks, accretion,… • How do these form? • Ejection from multiples, clusters • Formation like stars • Properties of disks • Do they form in low-mass, dense envelopes? • Low end of core mass function

36. Planet Formation • Best studied around isolated stars • Origin and evolution of disk • Gaps, rings, … • Debris disks as tracers of planet formation • Chemistry in disks • Evolution of dust, ices, gas

37. Planet Formation SMM image of Vega shows dust peaks off center from star (*). Fits a model with a Neptune like planet clearing a gap. This is with 15-m at 850 microns and 15” resolution. ALMA can do at higher resolution. SMM image of Vega JACH, Holland et al. Model by Wyatt (2003), ApJ, 598, 1321

38. With higher resolution Vega also observed by Wilner et al. (2003). Model of resonance with planet.

39. Predicts motion of dust Model and Animation by Marc Kuchner

40. ALMA Resolution Simulation Contains: * 140 AU disk * inner hole (3 AU) * gap 6-8 AU * forming giant planets at: 9, 22, 46 AU with local over-densities * ALMA with 2x over-density * ALMA with 20% under-density * Each letter 4 AU wide, 35 AU high Observed with 10 km array At 140 pc, 1.3 mm Observed Model L. G. Mundy

41. Chemistry of Planet-forming Disks LkCa15 with OVRO. Trace the composition changes with evolution. ALMA will have resolution and sensitivity to do this kind of study in many disks. Qi et al. 2004

42. The Icy Component Rich spectrum of ices: CO2, H2O, CH3OH, OCN– and others. Can study ice evolution in regions forming sun-like stars. Little processing at T>50 K, some evidence for lower temperature processing. Spitzer IRS plus Keck/NIRSPEC or VLT/ISAAC Boogert et al. ApJS, submitted

43. Open Questions • How the disk initially forms • Timescales for disk evolution • How planets form in the disk • Core accretion or Gravitational Instability • How unusual the solar system is • Systems with giant planets out where ours are • Evolution of dust, ice, gas in disk • Building blocks for planets

44. Requirements • Maximum Spatial resolution • Image fidelity (gaps will be hard to see) • Best sensitivity • Especially for debris disks • Flexible correlator, receiver bands • Chemistry

45. In the ALMA era… SOFIA 2005 SMA, CARMA, eVLA, LMT, GBT, APEX, ASTE, JCMT, CSO, … Spitzer 2003 Herschel 2007 SAFIR ~2015 JWST 2011 AT-25 2012

46. Making the most of ALMA • Complementary Observatories • User-friendly system • Low barriers to those from other wavelengths • Proposals, planning tools, reduction, analysis • Scientific support staff • Broad wavelength experience • Financial support tied to time

47. A Closer Look A few abundance profiles at t=100,000 yr. Vertical offset for convenience (except CO and HCN). Big effect is CO desorption, which affects most other species. Secondary peaks related to evaporation of other species. J. Lee et al. In prep

48. Bolocam map of Ophiuchus Bolocam map (1.2 mm) of region in Spitzer survey. Covers very large area (> 10 sq. deg.) compared to any previous map. Rms noise ~ 50 mJy, with about half the data. K. Young et al. In prep

49. Early Results from Spitzer • Based on validation data (about 1%) • Observed two small cores (IRAC/MIPS) • One (L1228) with a known infrared source • One (L1014) without • Observed a few IRS targets • B5 IRS • HH46/47 IRS (with ERO team)

50. A Typical Starless Core L1014 distance ~ 200 pc, but somewhat uncertain. R-band image from DSS