1. STAR FORMATION STUDIES with the CORNELL-CALTECH ATACAMA TELESCOPE Star Formation/ISM Working Group Paul F. Goldsmith (Cornell) & Neal. J. Evans II (Univ. Texas)

2. 2 WHY CCAT? Understanding key aspects of star formation requires submm observations with few arcsec resolution, high sensitivity, and ability to observe –Continuum emission from dust –Spectral line emission from molecules Essential to study fragmentation and collapse of cloud cores to form protostars (including disks), and also star clusters

3. 3 MOLECULAR CLOUDS AND STAR FORMATION Stars form in molecular clouds: cold -- 10 < T < 100 K, modest density -- 10 3 <n(H 2 ) < 10 6 cm -3 Large visual extinction of these regions precludes optical study of dense condensations, or CLOUD CORES, where star formation occurs We can use continuum emission from dust and spectral line emission from trace molecules CO, 13 CO, C 18 O as complementary tracers of cloud material Core sizes are ~ 0.1pc (2’ @ 140 pc) and have masses between a fraction and a few solar masses Need large unbiased sample to determine how low end of stellar IMF is determined, and we also must define physical parameters and internal structure to determine collapse timescale and evolution

4. 4 13 CO J = 1-0 map obtained with FCRAO 14m antenna and 32- element SEQUOIA focal plane array 45” res. 3.2x10 6 pixels HIGHLY STRUCTURED! CLOUD CORE

5. 5 COLD CLOUD CORES Embedded within larger molecular clouds & cloud complexes Specific sites marking earliest phase of gravitational contraction and star formation Low temperatures (T < 12 K) make submm data essential CCAT & 1mm to 200 micron cameras will be an extremely fast survey instrument Also capable of studying structure of nearly cloud cores Complements Herschel, LMT, and leads to detailed ALMA studies Figure: 850 micron and 200 micron maps of 6 cores (J. Kirk et al. MNRAS 2005)

6. 6 COLD CLOUD CORE (CCC) SURVEY Utilize CCAT + large-format camera in 1200 to 200 micron wavelength range On-the-fly mapping Nyquist-sampled (1.4”) maps at 350 micron wavelenth Can detect 0.1 solar mass core with S/N ratio 1 – 10 (depending on wavelength and temperature) in 1 s. integration Need ~1000 hr per wavelength if not multiplexed for nearby cloud complexes Figure: Emssion from 1 solar mass core at temperatures 6, 8, & 10 K and emissivity power law indices 1 (broken) and 2 (solid) Want to recover structure from arcsecond to degee scale

7. 7 IMPORTANCE OF 200 MICRON OBSERVATIONS Compared to longer wavelengths, 200 micron emission is extremely sensitive to WARM dust Vital for separating “warm” & “cool” components

8. 8 STAR FORMATION SCIENCE WITH HETERODYNE SYSTEMS Require arrays (>16 elements to achieve satisfactory mapping speed) Cold Core Survey studying formation of low mass stars in very quiescent cores of modest density CO and isotopologues Require high frequency resolution (fractional resolution > 10 6 ) Galactic Plane and Individual Giant Molecular Cloud Surveys High densities and temperatures enable a vast arsenal of probes of physical conditions and chemistry J = 3-2, 4-3, 6-5 transitions of CO, 13 CO, C 18 O High-J transitions of species including CS, HCN, N 2 H +,… Dust continuum emission and spectral lines Match to and precursor for many LMT, Herschel, and ALMA projects

9. 9 CCAT GALACTIC PLANE SURVEYS Star formation in Giant Molecular Clouds linked to warmer, denser, larger, and more massive aggregates of dust and gas High density (high dipole moment) spectral lines throughout submm range offer unique probes of physical conditions, especially kinematics of highest density gas and regions of highest excitation (shocks) Employ multiple Spectral lines and short- wavelength dust continuum Complementary to GLIMPSE, Herschel, and many other Galactic Plane surveys

10. 10 THE MAGNETIC FIELD Plays potentially vital but essentially unverified role in evolution of molecular clouds, cores, protostars, and disks Polarized SUBMM dust emission is an incredibly powerful but so far unexploited tool for studying the B-field Directly measure B-field orientation in dense regions Need to have good sensitivity and low (stable) systematics CCAT with large-format submm camera and POLARIMETER will be ideal tool for this work Figure: OMC3 Filament (B. Matthews & C. Wilson ApJ 2000)

11. 11 12 CO emission and B - field vectors from optical polarization B follows low density filaments Will polarized dust emission from within filaments (see 13 CO) show continuity of field? MAGNETIC FIELD STUDIES NEED LARGE-SCALE MAPS