Title A ultradeep galaxy survey through clusters using ALMA Pi A. Blain Time 1740 hrs 1. Name of program and authors A ultradeep galaxy survey through clusters using ALMA Andrew Blain 2. One short paragraph with science goal(s) Clusters of galaxies are the most massive gravitationally relaxed systems in the Universe, and the most powerful gravitational lenses. Depending on the brightness distribution of faint background galaxies, the surface density of their lensed images to a chosen flux density limit can be increased by several times by a foreground cluster. Furthermore, the magnification, by up to several 10's, allows galaxies to be probed in more detail than possible without the magnification. In order to determine the properties of the population of galaxies at fainter levels than currently possible, benefiting from the gravitational lensing, the typically ring-like 1-arcmin radius `critical line' structures along which the greatest magnifications will be found will be mapped, involving of order 20 pointings per cluster. An additional speculative investigation could image the central core of the clusters to the same deep depth. If the potential of the cluster is sufficiently is sufficienty steep at the center: corresponding to a volume density of mass that depends on radius as the -1.5 power or steeper, then de-magnified images of all the background galaxies within the = approx. 1 arcmin radius of the critical lines can be imaged within a few arcsec of the core of the cluster. ALMA's exquisite resolution can be used to detect all of these objects in a single additional pointing per cluster (Blain 2002 MNRAS 330 219). Hence, the cluster images would have a `bullseye' structure. The location of the fields within the clusters will be chosen carefully based on the best models of the potential of the clusters available in 2012 from optical, X-ray and Sunyaev-Zeldovich (SZ) effect observations. It is likely that it would be productive to include the same targets in a 90-GHz band-3 line survey, which could produce SZ effect images alongside. 3. Number of sources (e.g., 1 deep field of 4'x4', 50 YSO's, 300 T Tauri stars with disks, ...; do NOT list individual sources or your "pet object", except in special cases like LMC, Cen A, HDFS) 4. Coordinates: 4.1. Rough RA and DEC (e.g., 30 sources in Taurus, 30 in Oph, 20 in Cha, 30 in Lupus) Indicate if there is significant clustering in a particular RA/DEC range (e.g., if objects in one particular RA range take 90% of the time) Up to 20 rich clusters at approximately z=0.2-1.2. Spread around the sky, but mainly equatorial (based on the most complete cluster surveys having been followed up by large telescopes in the North). 4.2. Moving target: yes/no (e.g. comet, planet, ...) No 4.3. Time critical: yes/no (e.g. SN, GRB, ...) No 4.4. Scheduling constraints: (optional) None 5. Spatial scales: 5.1. Angular resolution (arcsec): 0.1" 5.2. Range of spatial scales/FOV (arcsec): 0.1-5" (optional: indicate whether single-field, small mosaic, wide-field mosaic...) Small mosaic. 20 fields at 280 GHz round critical lines in band-6/7 7 fields at 90GHz in a hexagonal pack to cover whole region. 5.3. Required pointing accuracy: (arcsec) 1" 6. Observational setup 6.1. Single dish total power data: no/beneficial/required No Observing modes for single dish total power: (e.g., nutator switch; frequency switch; position switch; on-the-fly mapping; and combinations of the above) 6.2. Stand-alone ACA: no/beneficial/required Yes, if SZ sought. 6.3. Cross-correlation of 7m ACA and 12m baseline-ALMA antennas: no/beneficial/required Yes, as coherent spatial emission from lensed arcs could extend over most of the primary beam, and can see atmospheric effects on SZ/lensing signal in real time. 6.4. Subarrays of 12m baseline-ALMA antennas: yes/no No. 7. Frequencies: 7.1. Receiver band: Band 3, 4, 5, 6, 7, 8, or 9 Edge of band 6/7: faint continuum surveys most promising at these frequencies. Band-3: line surveys most promising here, and SZ effect 7.2. Lines and Frequencies (GHz): (approximate; do _not_ go into detail of correlator set-up but indicate whether multi-line or single line; apply redshift correction yourself; for multi-line observations in a single band requiring different frequency settings, indicate e.g. "3 frequency settings in Band 7" without specifying each frequency (or give dummies: 340., 350., 360. GHz). For projects of high-z sources with a range of redshifts, specify, e.g., "6 frequency settings in Band 3". Apply redshift correction yourself.) Continuum in band 6/7 single tuning. 3 line tunings in band 3. 7.3. Spectral resolution (km/s): 50-300 km/s 7.4. Bandwidth or spectral coverage (km/s or GHz): 8GHz 8. Continuum flux density: 8.1. Typical value (Jy): (take average value of set of objects) (optional: provide range of fluxes for set of objects) Typical optical galaxies at 0.1mJy or less. Deep survey, so unknown. SZ effect a few 100 mJy integrated over the cluster. 8.2. Required continuum rms (Jy or K): 0.01 mJy - band 6/7 - to reach much deeper than any current survey: detection limit is about 40 times deeper than current record. 8.3. Dynamic range within image: (from 7.1 and 7.2, but also indicate whether, e.g., weak objects next to bright objects) Brightest continuum sources 20mJy. 8.4. Calibration requirements: absolute ( 1-3% / 5% / 10% / n/a ) repeatability ( 1-3% / 5% / 10% / n/a ) relative ( 1-3% / 5% / 10% / n/a ) 10% 9. Line intensity: 9.1. Typical value (K or Jy): Set by continuum conditions above (take average value of set of objects) (optional: provide range of values for set of objects) 9.2. Required rms per channel (K or Jy): 9.3. Spectral dynamic range: 9.4. Calibration requirements: absolute ( 1-3% / 5% / 10% / n/a ) repeatability ( 1-3% / 5% / 10% / n/a ) relative ( 1-3% / 5% / 10% / n/a ) 10. Polarization: yes/no (optional) No 10.1. Required Stokes parameters: 10.2. Total polarized flux density (Jy): 10.3. Required polarization rms and/or dynamic range: 10.4. Polarization fidelity: 10.5. Required calibration accuracy: 11. Integration time for each observing mode/receiver setting (hr): Continuum rms at 280GHz is 0.02 mJy per hour => > 4 hour per pointing, 80 hours per cluster. For SZ at 90GHz, rms is 0.97mK per hour, so need about 1 hour per pointing, 7 hours per cluster 12. Total integration time for program (hr): 20 clusters (x87hr)= 1740 hours. Note that there are of order 20 suitable clusters, but that the time available could be cut to fit the available resource. The 1740 hour total gives the maximum amount of time that could be spent on this type of deep field observation. 13. Comments on observing strategy : (optional) (e.g. line surveys, Target of Opportunity, Sun, ...): Could be reduced in length, going for fewer objects. Otherwise, can be a long-term survey spread over 5 years or more. In DRSP1, a total of 500 hours was considered reasonable. Herschel & JWST will certainly cover ~30 clusters in a reasonable time (5 years). Hence, a reasonable number of targets for DSRP2 could be 5-6, for a similar total time. There is a potential long-term market for about 30 targets.