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

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

New Views are Coming The Archive is open:

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

Star Formation traced by HCN Relation between L IR and L CO becomes non-linear for very high L IR. Stays linear for L HCN. J. Wu et al. Data from Gao and Solomon 2003.

Relation Same for Cores in MW J Wu et al. In prep. L HCN or L CS for cores in MW also linear with L IR. (For L IR > 10 4 L sun ) 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.

What probes can we use?  Dust Extinction of background stars Extinction of background stars Probe N d (b), B perpProbe N d (b), B perp Emission in infrared to millimeter Emission in infrared to millimeter Probe T d ( r), N d (b), B perpProbe T d ( r), N d (b), B perp Problem: need to know dust properties Problem: need to know dust properties  Molecules Emission or absorption (infrared to radio) Emission or absorption (infrared to radio) Probe T K ( r), n( r), v( r), B parProbe T K ( r), n( r), v( r), B par Problem: chemistry Problem: chemistry

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

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

Linewidth versus Size Shirley et al 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.

Cumulative Mass Function Shirley et al Incomplete below 10 3 M sun. 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).

Massive Cores: Gross Properties  Massive, Dense, Turbulent Mass distribution closer to clusters, stars than GMC Mass distribution closer to clusters, stars than GMC Much more turbulent than low mass cores Much more turbulent than low mass cores  A model for starbursts? Luminosity correlates well with core mass Luminosity correlates well with core mass Less scatter than for GMCs as a whole Less scatter than for GMCs as a whole L/M much higher than for GMCs as a whole L/M much higher than for GMCs as a whole L/M dust ~ 1.4 x 10 4 L sun /M sun ~ high-z starbursts L/M dust ~ 1.4 x 10 4 L sun /M sun ~ high-z starbursts L/L(HCN) similar to starbursts L/L(HCN) similar to starbursts Starburst: all gas like dense cores? Starburst: all gas like dense cores?

Hints of Dynamics J. Wu et al. (2003) 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. V in ~ 1 to 4 km/s over radii of 0.3 to 1.5 pc.

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

Links to DRSP  Gas fraction/Star formation in Galaxies CO maps w High Res. (e.g., 1.7.6) CO maps w High Res. (e.g., 1.7.6) CO–gas conversion (e.g., 1.7.3, ) CO–gas conversion (e.g., 1.7.3, ) High n c tracers (e.g., 1.7.1, 1.7.9) High n c tracers (e.g., 1.7.1, 1.7.9) Dust (e.g., and others with lines) Dust (e.g., and others with lines)  Need more on tracers of dense gas?

Links to DRSP  Structure of massive cores Tracers of n, T (e.g., 2.1.4) Tracers of n, T (e.g., 2.1.4) Dynamics Dynamics Chemistry (e.g., 2.3.1–5) Chemistry (e.g., 2.3.1–5)  More thought on resolving fragmentation?

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

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

High vs. Low Early Conditions PropertyLowHigh p~1.8~1.8 n f (median) 2 x x 10 7 Linewidth n( r) = n f (r/r f ) –p ; r f = 1000 AU

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

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

The Basic Features T. Greene EnvelopeDiskProtostarJet/wind/outflow

Studies of the Envelope  All quantities vary along line of sight Dust temperature, T d ( r) Dust temperature, T d ( r) Heating from outside, later insideHeating from outside, later inside Gas temperature, T K ( r) Gas temperature, T K ( r) Gas-dust collisions, CRs, PE heatingGas-dust collisions, CRs, PE heating Density, n(r), predicted to vary Density, n(r), predicted to vary Velocity, v(r), connected to density Velocity, v(r), connected to density Abundance, X(r), varies Abundance, X(r), varies Photodissociation, freeze-out, desorptionPhotodissociation, freeze-out, desorption

An Evolutionary Model  A physical model from theory Sequence of Bonnor-Ebert spheres of increasing n c Sequence of Bonnor-Ebert spheres of increasing n c e.g., Shu (1977) “Inside-out collapse” 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 Follow gas as it falls, using evolving conditions  Line Profiles including all effects

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

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 R sun, 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.

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

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

Calculate Abundances J. Lee et al. In prep 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.

Calculate Line Profiles J. Lee et al. In prep 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

A Closer Look J. Lee et al. In prep 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.

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

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

Low Mass Cores: Gross Properties  Molecular cloud necessary, not sufficient High density (n>10 4 cm –3 ) High density (n>10 4 cm –3 ) Low turbulence Low turbulence  Centrally peaked density distribution Power law slope ~ high mass Power law slope ~ high mass Fiducial density ~ 100 times lower Fiducial density ~ 100 times lower  Complex chemistry, dynamics even in 1D Evidence for infall seen, but hard to study Evidence for infall seen, but hard to study Outflow starts early, strong effect on lines Outflow starts early, strong effect on lines Rotation on small scales Rotation on small scales

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

Links to DRSP  Initial Conditions Cloud/core relation (e.g., 2.1.6, 2.2.1) Cloud/core relation (e.g., 2.1.6, 2.2.1) Conditions in cores (e.g., 2.1.2, 2.1.7, 2.2.2–4) Conditions in cores (e.g., 2.1.2, 2.1.7, 2.2.2–4) Inward motions (e.g., 2.1.8, 2.2.3) Inward motions (e.g., 2.1.8, 2.2.3)  Timescales (need big sample)  Infall Inverse P-Cygni (2.2.4) Inverse P-Cygni (2.2.4) Chemo-dynamical (2.3.2, 2.3.8) Chemo-dynamical (2.3.2, 2.3.8)  Envelope-disk interaction (e.g., 2.1.7)  Outflow dynamics (e.g., , 2.3.8)

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

Links to DRSP  Evidence for envelopes/disks Surveys for cores to low levels (e.g., 2.1.1, 2.1.6) Surveys for cores to low levels (e.g., 2.1.1, 2.1.6) Study of disks around known substellar objects (e.g., 2.4.4) Study of disks around known substellar objects (e.g., 2.4.4)  Some more thought needed?

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 Evolution of dust, ices, gas

Planet Formation SMM image of Vega JACH, Holland et al. 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. Model by Wyatt (2003), ApJ, 598, 1321

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

Predicts motion of dust Model and Animation by Marc Kuchner

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 9, 22, 46 AU with local over-densities over-densities * ALMA with 2x over-density * ALMA with 20% under-density under-density * Each letter 4 AU wide, 35 AU high 35 AU high Observed with 10 km array At 140 pc, 1.3 mm Observed Model Observed Model L. G. Mundy

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

The Icy Component Boogert et al. ApJS, submitted Spitzer IRS plus Keck/NIRSPEC or VLT/ISAAC Rich spectrum of ices: CO 2, H 2 O, CH 3 OH, 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.

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

Links to DRSP  Formation of disk (e.g., 2.1.7)  Timescales (e.g., 2.4.6, 2.4.7)  Planet formation (e.g., 2.4.3, 2.4.5)  Planetary systems like ours?  Chemistry in disks (e.g., 2.4.2)

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

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

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

A Closer Look J. Lee et al. In prep 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.

Bolocam map of Ophiuchus K. Young et al. In prep 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.

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

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

A Surprise from Spitzer Three Color Composite: Blue = 3.6 microns Green = 8.0 microns Red = 24 microns R-band image from DSS at Lower left. We see many stars through the cloud not seen in R. The central source is NOT a background star. L1014 is not “source-less”. Larger size in red is PSF. C. Young et al. ApJS, submitted

Source Peaks on mm Emission Left: 8 micron on 1.2 mm MAMBO dust continuum emission (Kauffmann & Bertoldi) Right: 24 micron on 850 micron SCUBA data (Visser et al. 2002) Both long-wave maps are 3-sigma contours. C. Young et al. ApJS, submitted

Models C. Young et al. ApJS, submitted Model of SED for d = 200 pc. Central object has very low luminosity: 0.09 L sun. Requires BB plus disk (red line) in an envelope. M(envelope) about 2 M sun. Cannot be a stellar-mass object with significant accretion. Probably sub- stellar at this point. Alternative model: more distant (2.6 kpc) object lined up by chance with peak of a foreground core (dashed line)

Lessons from L1014  “Starless” cores may not be Or may have substellar objects Or may have substellar objects 1 out of 1 has a source (will soon have more) 1 out of 1 has a source (will soon have more)  Very low luminosity sources may exist Must be low mass and low accretion Must be low mass and low accretion Caveat: possible background source Caveat: possible background source

HH46/H47 Cloud NASA/JPL-Caltech