Title Unbiased survey of submm galaxies: continuum survey at 1 mm Pi S.Guilloteau Time 80 hrs 1.1.1: Name -- Unbiased survey of submm galaxies -- -- Part 1 -- Authors: S.Guilloteau 2. Science goal: -- (Generic Science Scope from C.Carilli) -- The discovery of the IR background, and the SCUBA/MAMBO population of dusty, star forming galaxies at high redshift, has transformed our understanding of galaxy formation. It is now clear that a significant fraction (of order 50%) of star formation in the cosmos occurs in galaxies that are heavily obscured by dust, and that this fraction may rise with redshift, possibly corresponding to the formation of spheroidal galaxies in active starbursts. One highly uncertain aspect of the study of submm galaxies is their redshift distribution. Optical redshifts remain problematic for the majority of such sources, and can be misleading due to possible mis-identifications. -- (specific part) An important way to study the history of galaxy formation is to perform an unbiased redshift survey. We propose a unbiased, high sensitivity survey over a 4x4' area of the sky. This survey consists in a 4 main parts, and 2 or 3 complementary observations which are discussed in separate proposals: - Part 1) Continuum survey at 1 mm to reach 0.1 mJy point source sensitivity at the 5 sigma level. - Part 2) Combined line and continuum survey at 3 mm, down to 7.5 microJy at the 5 sigma level. - Part 3) Pointed continuum survey at 650 GHz towards sources detected in Part 1), down to 0.4 mJy at the 5 sigma level - Part 4) Line survey of the 210-275 GHz frequency band, down to 50 microJy for the 8 GHz bandwidth, with some angular resolution (0.4") in order to provide dynamical masses and lens corrections for the detectable sources. The fraction of sources found in Part 1 to be detected in Part 4 is unknown, but should be high (perhaps 50 -- 80 %). The complementary observations include: high resolution imaging to identify lenses and derive dynamical masses, and observations of other lines such as HCN or CI. This proposal covers Part 1). Continuum surveys made by large bolometer cameras will cover much wider fields of view, but will most likely be sensitivity limited to a level at least 5 to 10 times above the proposed ALMA survey. ALMA will explore a range of star formation rates much lower than those of currently detected sub-mm sources. With a proposed sensitivity level of 0.1 mJy, the survey should be able to find between 100 and 300 continuum sources, depending on the applicable cosmological model. 30 to 90 sources are expected to be brighter than 0.4 mJy. 3. Number of sources: 1 field of 4x4' 4. Coordinates: 4.1. Any 4.2. Moving target: no 4.3. Time critical: no 5. Spatial scales: 5.1. Angular resolution: 1" 5.2. Range of spatial scales/FOV: 5.3. Single dish: no 5.4. ACA: no 5.5. Subarrays: no 6. Frequencies: 6.1. Receiver band: Band 7 -- 290 GHz 6.2. Lines and Frequencies Continuum only 6.3. Spectral Resolution (km/s) (coarse) 6.4. Bandwidth or spectral coverage: 8 GHz (for search) 7. Continuum flux density: 7.1. Typical value: 0.1 - 1 mJy 7.2. Continuum peak value: 2-5 mJy 7.3. Required continuum rms: 20 microJy 7.4. Dynamic range in image: < 100:1 8. Line intensity: 8.1. Typical value: 8.2. Required rms per channel: 8.3. Spectral dynamic range: 9. Polarization: no 10. Integration time per setting: Mosaic of 140 pointings, 30 minutes per pointing center. 11. Total integration time for program: Part 1): 80 hours ********************************************************************** Review Pierre Cox: this programme in four parts proposes to explore a 4x4 arcmin^2 field in order to study the submm galaxy population in both the dust and line emission. A few 100-300 sources will be detected providing a census of the population together with first indications on their properties (redshifts, infrared luminosities, gas excitation, and dynamical masses). The time estimates are correct and the overall strategy is robust. Note that in 1.1.2, the current CO detections of submm galaxies indicate that the CO fluxes are about 1-2 Jy km/s for 1.3 mm continuum flux densities of 1-3 mJy rather than the 5-10 mJy which are indicated and which correspond to the 850 microns flux densities. Also at the expected sensitivities, one could perhaps start to detect species other than CO such as HCN which is typically 10 times weaker than CO. -------------------------------------------------- Review v2.0: 1.1.1 We may have to require about 43 min integration per pointing center in order to achieve 20 microJy rms if we assume the number of antenna is 50. The total integration time for this program (1.1.1) will be 100 hours or so. Note that the selection of target 4'x4' field is a very essential issue for this program, considering the effect of ``cosmic variance''.