1. CCAT Performance Terry Herter (Cornell University) 10 Oct 05 From Princeton Mtg

2. 2 Outline Very brief science motivation Site performance/requirements –Atmospheric transmission –Band observability (time available for different bands) Confusion Continuum Sensitivity Scalings, technical assumptions/requirements Science topic leads Appendices –More tabulations and system trades

3. 3 Galaxies peak in FIR/sub-mm Flux density vs. wavelength for an interacting galaxy system (Arp220) for redshifts of 1, 2, 4, and 8. Note the strong “negative K-correction” from about 500  m. Interacting Galaxies – Top: CO contours overlaid over optical image. Bottom: Spitzer multi-color infrared image.

4. 4 Sub-mm is rich in spectral lines Spectrum Orion KL region in the 350  m window showing a few of the molecular species accessible in the sub-mm (Comito et al. 2005). This is a very small portion (~1%) of the available window The spectral resolution is 2 MHz resolution (R ~ 410,000). Orion Molecular Cloud – Top: Optical image. Bottom: 350  m map. The arrow points to the location where the spectrum was taken.

5. 5 Sub-mm Atmospheric Transmission Atmospheric transmission for different amounts of precipitable water vapor. The horizontal red bars represent the adopted bandpasses and the average transmission for 0.25 mm PWV.

6. 6 Image from Google Maps 10 km Cerro Sairecabur 5500 m Cerro Toco 5600 m Cerro Chajnantor 5600 m Cerro Chascon 5675 m ALMA, CBI, APEX 5050 m (+ sign) Cerro Negro 5050 m Cordon Honar 5400 m San Pedro de Atacama 2400 m Chajnantor Region

7. 7 Time Available to Observe Ref.SairecaburChajnantor Time to CLPWVavailable# CLavailable# CL (  m) (GHz)(hr)(mm)hrs/yr fieldshrs/yr fields 200150012480.2628184 3508570.860.471936224410841257 6204841.140.64716629723634 7404050.430.7563914886901607 8653470.280.861223441312054348 14002140.301.001517509312994361 Total Time63125084 4506670.630.471936308210841725 11002730.071.00151723136129919809 20001500.961.001517157912991352 3300918.551.0015171771299152 Number of hours/year (round the clock) available for observing at a given (PWV) for Sairecabur (~5500 m) vs. the Chajnantor plateau (~5000 m). “# CL fields” is the number of fields that can be observed to the confusion limit over a year. The “Total Time” is the sum of available hours and represents all time (day or night) with PWV < 1.1 mm. The last four rows are possible alternate uses of time.

8. 8 Sub-mm Number Counts & Confusion Limits Sub-mm galaxy counts vs. flux density (number of sources with flux greater than S vs. S) for different wavelengths (after Blain et al.). Crossing lines show 30 (lower) and 10 (upper) beams/source confusion limits for D = 25 m.

9. 9 CCAT Sensitivity 5 , 1-hour CCAT and ALMA sensitivities. CCAT sensitivities computed for precipitable water vapor appropriate to that band. Confusion limits shown are 30 beams/source except for 10 beams/src case shown for CCAT.

10. 10 CCAT Baseline Continuum Sensitivity Sensitivity selected on the basis of appropriate PWV for that wavelength. NEFD is 1-sigma in 1 second. Confusion limit (CL) is for 30 beams/source. Time to CL is for S/N = 5. Source density is for all sources  CL flux. For an array size of 150x150 sampled at 2 pixels across the diffraction disk there are 240 sources/field at the confusion limit. PWVNEFDConf. LimitTime to CLDensity at CL (  m) (GHz)(mm)(mJy) (sec)(#/sq-deg) 20015000.3150.960.356 115935 22813170.3116.670.529 89409 29110300.3114.170.926 54677 3508570.414.411.293310637856 4506670.513.801.450226222901 6204840.516.351.277410012064 7404050.78.741.11215458469 8653471.05.830.9229986198 11032731.02.060.6702363833 11812541.01.740.6102043325 14002141.52.930.44710722366 20001501.52.300.19634581159 330090.91.52.820.08030773426

11. 11 Figure 6: CCAT Survey Speed Point-source survey speed (for a 1  detection) for CCAT and ALMA vs. ). CCAT assumes a 150  150 focal plane array sampling two pixels/beam (max 20’ FoV). For equal sensitivities, CCAT/ALMA = 5100.

12. 12 Mapping speed comparing other facilities CCAT is an ultrafast mapper Assumptions –10000 pixel detector, Nyquist sampled at all bands 0.2, 0.35, 0.45, 0.67, 0.85,1.1mm (in order from violet-red) –Observationally verified counts (good to factor 2) –Confusion and all sky limits 1.2/0.85/0.35mm imaging speeds are compatible –To reach confusion at 0.35mm go several times deeper at 0.85mm Detection rates are –~150  SCUBA-2; ~300  ALMA –About 100-6000 per hour –Lifetime detection of order 10 7-8 galaxies: ~1% of ALL galaxies! –`1/3 sky survey’: ~1000 deg -2 for 3 deg 2 hr -1 gives 5000 hr

13. 13 Selected (Key) Facility Drivers Aperture –Sensitivity improves as  D 2 (hence time to a given S/N  D -4 ) –Confusion limit  D -  (   2 and 1.2 at 350 and 850  m respectively) Field-of-view (5’ x 5’ initially, up to 20’ across eventually) –The major role of CCAT will be its unchallenged speed for moderate-resolution wide-field surveys –CCAT strongly complements ALMA (which will do follow-up) Chopping/Scanning –Bolometer arrays require modulating the signal through chopping and/or scanning the telescope –For chopping, this must be done at the secondary (~ 1’ at ~ 1Hz) –Scanning requires moderately large accelerations for reasonable efficiency (~ 1 deg/sec 2 ) Pointing –For spectrographs require placing to a fraction of slit width –And guiding to maintain spectrophotometric accuracy –=> 0.57”/0.71” [R] and 0.33/0.41” [G] arcsec pointing/guiding (1D rms)

14. 14 Science Leads Distant Galaxies –Andrew Blain (CIT) Sunyaev-Zeldovich Effect –Sunil Gowala (CIT) Local galaxies –Shardha Jogee (UT) + Gordon Stacey (Cornell) Cold Cloud Cores Survey –Paul Goldsmith (Cornell) + Neal Evans (UT) Circumstellar Disks –Darren Dowell (JPL/CIT) Kuiper Belt Objects –Jean-Luc Margot (Cornell)

15. 15 Appendices Tables: –1: CCAT Baseline Sensitivity (also slide 11) –2: CCAT Sensitivity vs. PWV –3: CCAT Confusion Limits –4: CCAT Line Sensitivity Figures: –1: NEFD vs. PWV –2: Performance vs. Surface RMS –3: Confusion Limit vs. Aperture –4: Time to CL vs. Aperture –5: Performance vs. Aperture –6: CCAT Survey Speed

16. 16 Table 1: CCAT Baseline Sensitivity Sensitivity selected on the basis of appropriate PWV for that wavelength. NEFD is 1-sigma in 1 second. Confusion limit (CL) is for 30 beams/source. Time to CL is for S/N = 5. Source density is for all sources  CL flux. For an array size of 150x150 sampled at 2 pixels across the diffraction disk there are 240 sources/field at the confusion limit. PWVNEFDConf. LimitTime to CLDensity at CL (  m) (GHz)(mm)(mJy) (sec)(#/sq-deg) 20015000.3150.960.356 115935 22813170.3116.670.529 89409 29110300.3114.170.926 54677 3508570.414.411.293310637856 4506670.513.801.450226222901 6204840.516.351.277410012064 7404050.78.741.11215458469 8653471.05.830.9229986198 11032731.02.060.6702363833 11812541.01.740.6102043325 14002141.52.930.44710722366 20001501.52.300.19634581159 330090.91.52.820.08030773426

17. 17 Table 2: CCAT Sensitivity vs. PWV NEFD (mJy) - 1-sigma, 1-second (  m) (GHz) 0.1250.250.300.400.500.701.002.00 200150048.45111.10150.96272.50483.171481.21 228131732.7882.86116.67225.86429.391516.22 291103034.2482.86114.17210.79380.751205.74 3508577.5410.3611.6314.4117.5925.3241.45175.66 4506675.988.249.2311.3913.8019.5130.89113.70 6204845.328.349.7112.7816.3525.3244.99234.54 7404054.285.175.546.307.088.7411.4623.07 8653472.903.293.453.774.104.775.839.82 11032731.331.431.471.561.641.802.062.95 11812541.091.181.221.291.371.521.742.55 14002141.721.821.871.952.042.212.483.39 20001501.481.551.581.641.701.822.002.62 330090.91.771.871.901.982.052.202.433.22 Bold numbers are the baseline sensitivity for CCAT. Assumptions: 30 deg from zenith, 12  m surface rms, chopping/difference loss of 1.414, 5000m altitude for transmission calculations (but consistent with tau(222  m) measurements from Sairecabur). PWV varies from 0.125 to 2.0 mm.

18. 18 Table 3: CCAT Confusion Limits Flux (mJy) lam(  m) 10 beam/src30 beams/src 2000.0420.356 2500.1030.529 3500.2420.926 4500.3721.293 6510.5301.450 7410.5591.277 8720.5291.112 10990.4610.922 14000.3590.670 21000.3290.610 33000.2480.447 From Andrew Blain, 3/28/05. Updated to be consistent with beam size definition used in sensitivity calculation.

19. 19 Table 4: CCAT Line Sensitivity R = 1000 spectroscopic sensitivity for CCAT. Numbers are for 1-sigma in 1- second. Sensitivity selected on the basis of appropriate PWV for that wavelength. Note: these numbers are for a non-heterodyne spectrograph. lamFreqPWVNEFDLine Flux (  m) (GHz)(mm)(mJy)(W/m 2 ) 20015000.31627.02.44E-17 22813170.31760.32.32E-17 29110300.31182.51.22E-17 3508570.4253.42.17E-18 4506670.5231.71.54E-18 6204840.5272.41.32E-18 7404060.7111.14.50E-19 8653471.091.13.16E-19 11032721.061.41.67E-19 11812541.062.11.58E-19 14002141.562.31.33E-19 20001501.558.48.34E-20 3300911.564.65.87E-20

20. 20 Figure 1: NEFD vs. PWV Changing in CCAT sensitivity vs. precipitable water vapor for different operating wavelengths. NEFD is the flux density for 1-sigma in 1 second.

21. 21 Figure 2: Performance vs. Surface RMS Changing in CCAT sensitivity vs. total rms surface accuracy for different operating wavelengths. NEFD is the flux density for 1-sigma in 1 second.

22. 22 Figure 3: Confusion Limit vs. Aperture CCAT confusion limit vs. aperture based on source counts model of Blain et al.

23. 23 Figure 4: Time to CL vs. Aperture Time to reach confusion limit vs. aperture. All other parameters the same as specified in Table 1.

24. 24 Figure 5: Performance vs. Aperture Changing in CCAT sensitivity vs. aperture for different operating wavelengths (all scale at D -2 ). NEFD is the flux density for 1- sigma in 1 second.

25. 25 Figure 6: Weighted Differential PWV Distribution Differential precipitable water vapor (PWV) distribution divided by NEFD 2 for three different wavebands for the Chajnantor plateau (dashed) and Sairecabur (solid). Each site is normalized at PWV = 0.5 mm so that the integral is the effective time available assuming the PWV is a constant at 0.5 mm. The horizontal bars represent the rough PWV range over which it is optimal to observe at different wavelengths. From left to right these are 200, 350/450, 620, 740, 865, > 1000  m.