The Palomar QUEST Variability Survey

Charles BaltayYale University

- JPL

Palomar-QUEST Collaboration

Yale Peter Andrews, Charles Baltay, Anne Bauer, Nan Ellman, Will Emmet, Nick Morgan, David Rabinowitz, Jeff Snyder, Kathy Vivas, Bob Zinn

Indiana Bryce Adams, Mark Gebhard, Kent Honeycutt, Jim Musser

Cal Tech Richard Ellis, George Djorgovski, Shri Kulkarni, Ashish Mahabal, Mike Brown, Lynn Hillenbrand, John Carpenter, Avishay Gal-Yam, Matthew Graham, Roy Williams

JPL Ray Bradbury, Steve Pravdo

Berkeley Saul Perlmutter, Greg Aldering, Peter Nugent, Michael Woods-Vasey, et al.

Large Area CCD Camera for the 48” Palomar Schmidt Telescope

25.0 cm4.60

19.3 cm3.60

5.40 DiameterClear Field of ViewOf the Telescope

14” Window Diameter

4 Rows of 28 CCD’s each 112 CCD’s totalEach CCD – 2400 x 600 13 μ x 13 μ pixelsArray 16, 800 x 9,600 pixels 161 Megapixels tot.

Drift Scanning• Keep telescope stationary• Align CCD’s with columns along line of motion of star images• Synchronize clock rate to motion of star

Issues to worry about:

• Clock rate– Precision– Variability

• Exposure time fixed by star image motion• Resolution broadening due to curvature of star tracks on CCD

– Sagitta– Clock rate variation across CCD

These considerations limit CCD array size to ~ 4000 x 1000, 7.5 to 25 µ pixels

Star Image

CCDFinger (28 CCD’s)Return Spring

Spiral CAM

Base Plate

Pivot Point

StarImage

Fig. 11 Design for the CCD rotating mechanism

CameraBody

Shutter

Filter Tray

UVBlueVisRed

• Up to 4 colors per Drift Scan Pass• Easily Changeable

Star Image

Data Rates in Drift Scan ModePixels/CCD 1.44 x 106

CCD’s in Camera 112

Total Pixels 161 x 106

Total Bytes at 2 bytes/pixel 322 x 106

Megabytes/139 seconds 322

Data Rate 2.3 Megabytes/sec

Data Per Night 66 Gigabytes/night

In Point and Track Mode

Data/Night Depends on Exposure Time

Data/Night = GigabytesxTimeExp

66

sec 140

Current Observing PatternAllocate nights about evenly between Drift Scanning and Point and

Track

Drift Scan Nights• We do a strip 4.6o wide (in N-S direction) by 8 hours x 15o/hour =

120o in RA• ~ 550 square degrees/night

in 4 colors “simultaneously” using one of two filter sets: Johnson UBRI, or Gunn rizz

• Effective exposure time ~ 140 seconds on each CCD

Point and Track Nights• Use single broad Red Filter on whole array,λ> 6000 Å

• Typically take one minute exposures, ~ 30/hour, 9.4 square degrees each

• Take 3 shots of the same area of sky at ~ ½ hour spacing• So in a clear 8 hour night cover ~ 750 square degrees, 3 times

each, one color

~

Palomar/QUEST Data – Fall 2003Region C – RA from ~ 20 hrs to ~ 5 hrs

Declination UBRI rizz

22½o Nov. 6Nov. 7

Dec. 29

18 Sept. 27Nov. 26

Oct. 2Oct. 3

13½ Aug. 31Dec. 2

Aug. 8Sept. 3

9 Aug. 2Sept. 5

Sept. 2Sept. 28

4½ Aug. 30Sept. 4

Aug. 10Sept. 29

0 Sept. 1Sept. 6Sept. 7

Sept. 30Oct. 1

-4½ Sept. 8Dec. 3

Oct. 4Oct. 5

-9 Oct. 6

-13½ Jan. 1

-18 Jan 4

-22½ Jan. 5

Variability Time Scales

Repeated observations on time scales from minutes to years:

• In drift scan mode, 4 repeated observations (in different colors) on the 4 rows of CCD’s spaced by ~ 4 minutes

• In point and track mode repeat same area of sky (in the same color) at ~ ½ hour spacing then repeat again in ~ a month

• In any given lunation repeat drift scan of same area of sky 4 times (2 with UBRI, 2 with rizz) at interval of a few days to weeks or a month

• In both point and track and in drift scan plan to cover 10,000 to 15,000 square degrees each year, repeat same area year after year for yearly variability up to ~ 5 years

Callibration and Limiting Magnitudes

1. Calibrate Magnitudes in each color filter using Stetson Standard Stars

2. Define Limiting Magnitude at Signal/Noise = 10/1. Estimate Lim Mag from plot of

mag error vs. calib. mag for each

color.

15

10

5

0-2.2 -2.4 -2.6 -2.8

Mag

Err

or

No.

of

Sta

nd

ard

Sta

rs

Calibrated Magnitude

R

R

M (instrum) – m (Standard Star)

3. Using Col 13 from Sept. 1, 2003 data, obtain

Color Seeing

FWHM

Sky Level

e/pixel

Limiting Magnitude

U 2.3” 20 19.9

B 2.2” 300 21.7

R 2.0” 1500 20.9

I 1.7” 2300 20.2

Supernova StudiesFour Distinct Projects:

1. Low Red Shift (Z ≤ 0.1) Type Ia’sAnchor Hubble Diagram for high Z SNe studies (Cosmology)Perlmutter, Aldering, Nugent, Woods-Vasey, Yale Group (Supernova

Factory)

2. Type II (Core Collapse) SupernovaeCan these be used as Standard Candles?R. Ellis, Avishay Gal-Yam, Yale Group

3. Intermediate Red Shift (0.1 ≤ Z ≤ 0.3) Type Ia’sMeasure of w in Dark Energy Equation of state P = wρPerlmutter, Aldering, Yale Group

4. Type Ib,c SNe’sS. Kulkarni, et al.

Expected Numbers of Supernovae

Type Ia SNEUse Rate from R. Pain, et al. (APJ 577, 120, 2002)

Type II SNE• Typically 2 mags fainter than Ia’s

(Hamuy & Pinto APJ 566, L63, 2002)

• About twice as numerous per unit volume as Ia’s(Capellaro, et al., AA 351, 459, 1999)

Estimate numbers of SNe’s for 1000 square degrees, 15 day time window

Up to Z Peak m No/1000 sq deg

Peak m No/1000 sq deg

0.05 17.5 2 19.5 6

0.10 19.0 12 21.0 24

0.20 20.5 100 22.5 200

0.30 21.5 300 23.5 600

0.40 22.0 650 24.0 1300

Type Ia SNe’s Type II SNe’s

Study of Type Ia Supernovae

1. Low Red Shift (Z < 0.1)• Need to calibrate Hubble Diagram for high Z

SNe studies; systematic studies of nearby Ia’s• Rare, bright events

m < 18.5~ 10 SNe/1000 square degrees/15 day windowPalomar-QUEST is an ideal instrument for this(Supernova Factory)

• Need to look all year, both in drift scan and point and track *Discovery with 3 repeated QUEST scans*Photometric follow-up to get light curves

McDonald lm, SMART

• Spectroscopic Follow-upHawaii 2.2 m (Supernova Factory)

2. Study of Type II Supernovae

• Question – Can Type II supernovae be used as Standard Candles?

• Indication by Hamuy & Pinto (ApJ 566, L63 (2002) of a correlation between SNe absolute magnitude and expansion velocity of photosphere at mid plateau

• Palomar-QUEST plan to collect a sample of low red shift (Z < 0.1) Type II’s to establish (or otherwise) this

correlation

– Discovery of Type II’s on QUEST drift scan in UBRI colors*m peak < 21*~ 20 SNe’s/1000 square degrees/15 day window

– Devote one lunation per year Scan 1000 square degrees 5 times each on 2 day

intervals– Use colors to separate Type II’s from Type Ia’s a la Peter

Nugent– Photometric follow-up on Palomar 60” to get light curve– Spectroscopic follow-up on Palomar 200” or KECK to

measure Photosphere expansion velocity (using Fe 5169 Å line?)

– Measure magnitude spread after correlation correctionType Ia spread m ~ 0.17

~

3. Intermediate Red Shift (0.1 < Z < 0.4)

• Goal – measurement of w in p = wρ

w < -1/3 Dark Energy, w = -1 Cosmological Const.

• Fainter, more frequent events19 < m <22~ 1 SNe/square degree/15 day window

• Dedicated 1 month search on QUEST ~ 5 repeated scans of ~ 1000 sq. degrees get light curves near peak from QUESTAlso good for search for Type II SNE’s and Bob Zinn’s RR

Lyrae study

• Need follow-up photometry for tails of light curves (Palomar 60”?)

• Need spectroscopic follow-up of faint objects (m < 22!)This is a problem - ….

*Suggested by Spergel & Starkman astro-ph/0204089

Palomar-QUEST Science Projects1. Quasar Variability Survey (~ 15000 sq degrees)

Yale Group2. Gravitational Lensing of Quasars

Yale Group3. High Red Shift Quasars Z ≥ 6

G. Djorgovski, et al., and Yale Group4. Type Ia Supernova

Perlmutter, Aldering, Nugent, Woods-Vasey, et al., with Yale Group (Supernova Factory)

5. Type II SupernovaR. Ellis, Avishay Gl-Yam and Yale Group

6. GRB’s, Tlype Ib,c Supernovae, Unusual TransientsS. Kulkarni, et al., and G. Djorkovski, et at.

7. Variation of with timeYale Group with Yale Atomic Physics Group & U of Connecticut

8. Minor Planet/Kuyper Belt Object SurveyMike Brown, et al., and D. Rabinowitz, Yale

9. RR Lyrae StarsYale (Bob Zin, Kathy Vivas, et al.)

10. Near Earth Asteroid TrackingJPL NEAT Project

11. T-Tauri StarsLynn Hillenbrand, John Carpenter, et al.

12. Young Star FormationKent Honeycutt, et al.