Probing the IMF Star Formation in Massive Clusters

Probing the IMF: Goals Quantify the IMF in rich, dense star-forming regions Understand the relationship between IMF; initial conditions locate the stellar birthline/region link to mass accretion rate explore linkage to thermal + turbulent pressure Critical to modeling star-formation in the early universe

Probing the IMF: Measurements JHK photometry MCAO images at high Strehl (~0.5 at J-band) IFU spectroscopy at R ~ 1000 MCAO photometry can probe 0.3 to 100 Msun in Arches cluster; R 136 define birthline location + IMF 5 to 100 Msun in clusters out to ~1 Mpc quantify slope of upper IMF IFU spectroscopy can probe brightest stars

Probing the IMF: Measurements Galactic Center Superclusters: d = 10 kpc = 7” Stellar density ~ 100x Orion Nebula Cluster

Probing the IMF: Measurements LMC Massive Cluster: d = 200 kpc R 136 20” Stellar density ~ 10x Orion Nebula Cluster

Probing the IMF: Measurements M82 Superclusters: d = 4 Mpc

Probing the IMF: Measurements Stellar Birthlines for Differing dMacc/dt High dMacc/dt Low dMacc/dt How is dMacc/dt related to [Fe/H]; stellar density?

Probing the IMF: Ancillary Science Quantify the spatial distribution for stars of different masses & ages Do massive stars form preferentially near the cluster center? If so, does this imply a different formation mechanism? Quantify stellar multiplicity in dense clusters What role do dynamical interactions play in influencing multiplicity? What are the relevant timescales and environmental conditions?

Probing the IMF: Current Status With current 6-10m class telescopes + HST: Crowding limits IMF probe to M > 2 Msun in Arches; R 136 IMF probes in regions more distant than ~1 Mpc is precluded by crowding

Probing the IMF: Need for GSMT Key issue is crowding (not photon collection) With a 30m GSMT, K-band diffraction limit is 0.015” Arches clusters can be studied throughout the M33 disk Probe birthlines; IMF for wide range of metallicities R 136 clusters can be studied out to M82 (upper end of IMF)

Probing the IMF: Requirements MCAO-fed near IR imager with ~1’ FOV Deliver Strehl ~ 0.5 at J-band MCAO-fed IFU spectrograph with R ~ 3000

Probing the IMF: Trades Ability to probe IMF to larger distances; lower masses increases dramatically as aperture increases Directly linked to reduced crowding Adequate sampling of IMF may not require MCAO correction over maximum achievable field (~2’)

Effects of Crowding on Photometry 20” M 32 (Gemini/Hokupaa) NGST GSMT with MCAO

Probing the IMF: GSMT v NGST et al NGST is limited by crowding (see previous slide) ALMA could probe initial conditions in Galactic regions

Probing the IMF: Needed Simulations Quantify crowding vs aperture trade Simulate variable extinction & nebular background Understand Strehl vs photometric precision trade Understand optimum field of view Model time variations of Strehl during exposure