Forming High Mass Stars

Probing the Formation Epoch

Forming HM Stars: Goals

• Probe epoch of stellar assembly for “isolated” HM stars

• Quantify cloud infall and disk accretion rates

• Locate and quantify associated stellar population

• Determine:

• linkage between outcome mass(es) and initial conditions

• relationship between accretion and outflow processes

• IMF for associated stellar population (unusual or not?)

Forming HM Stars: Measurements

• MCAO imaging at H & K bands• CAO imaging at M and N bands• High resolution M-band spectroscopy (R ~ 105)Proposed targetsProposed targets: Compact H II regions• AO imaging can probe:

– morphology of star-disk-envelope region– distribution; N(mass) for associated population– wind morphology

• High resolution spectroscopy can quantify:• envelope infall rates• disk accretion rates (?)• wind momenta and energy

Probing the IMF: Current Status

With current 6-10m class telescopes + HST:

• Extinction (AV > 100 mag) too great to enable imaging

the forming star and its environs

• Angular resolution ~ 90 AU at 2 kpc (too low)

• Sensitivity too low for high resolution spectroscopy

Forming HM Stars: Need for GSMT

With a 30m GSMT, K-band diffraction limit is 0.015”• Disks & envelopes can be probed at 30 AU resolution at 2 kpc

With a 30m GSMT, M-band limiting magnitude ~ 12 (?)• Infall; disk accretion rates can be probed out to 10 kpc

NB: these numbers need checking

Forming HM Stars: Requirements

• MCAO-fed near IR imager with ~1’ FOV

– deliver Strehl ~ 0.6 at H-band

• CAO-fed mid-IR imager with ~ 10” FOV

• CAO-fed mid-IR spectrograph with R ~ 105

Forming HM Stars: Trades

• Ability to probe forming HM stars to larger distances

increases as aperture increases

– Angular resolution to probe at scales < 10 AU

– Increased sample size by extending search volume• Mid- IR performance enhanced by lower emissivity

Forming HM Stars: GSMT v NGST et al

• NGST is limited by

• “low” angular resolution

• no mid-IR high resolution imaging

• ALMA could provide a competitive; complementary tool• provide direct measure of initial conditions in molecular gas

• image envelope and disk regions; quantify gas kinematics

Forming HM Stars: Needed Simulations

• Comparison of ALMA; GSMT capabilities

• Defining optimal probes of envelope; disk and

wind kinematics