forming high mass stars probing the formation epoch
Post on 19-Jan-2016
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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
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