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

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 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 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 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 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 Time Available to Observe Ref.SairecaburChajnantor Time to CLPWVavailable# CLavailable# CL (  m) (GHz)(hr)(mm)hrs/yr fieldshrs/yr fields Total Time 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 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 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 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)

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 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 per hour –Lifetime detection of order galaxies: ~1% of ALL galaxies! –`1/3 sky survey’: ~1000 deg -2 for 3 deg 2 hr -1 gives 5000 hr

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 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 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 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)

17 Table 2: CCAT Sensitivity vs. PWV NEFD (mJy) - 1-sigma, 1-second (  m) (GHz) 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 to 2.0 mm.

18 Table 3: CCAT Confusion Limits Flux (mJy) lam(  m) 10 beam/src30 beams/src From Andrew Blain, 3/28/05. Updated to be consistent with beam size definition used in sensitivity calculation.

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

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 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 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.