The Palomar QUEST Variability Survey

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The Palomar QUEST Variability Survey
Charles Baltay Yale University
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- JPL
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Palomar-QUEST Collaboration
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Large Area CCD Camera for the 48 Palomar Schmidt
Telescope
25.0 cm
4.60
19.3 cm 3.60
14 Window Diameter
5.40 Diameter Clear Field of View Of the Telescope
4 Rows of 28 CCDs each 112 CCDs
total Each CCD 2400 x 600 13 µ x 13 µ
pixels Array 16, 800 x 9,600 pixels 161
Megapixels tot.
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Drift Scanning

• Keep telescope stationary
• Align CCDs 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

Star Image
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CCD
Star Image
Finger (28 CCDs)
Pivot Point
Return Spring
Spiral CAM
Base Plate
Fig. 11 Design for the CCD rotating mechanism
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Camera Body

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

Star Image
UV
Blue
Vis
Red
Shutter
Filter Tray
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Data Rates in Drift Scan Mode
In Point and Track Mode Data/Night Depends
on Exposure Time Data/Night
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Current Observing Pattern

• Allocate 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,?gt
  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

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

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Callibration and Limiting Magnitudes

• Define Limiting Magnitude at Signal/Noise 10/1.
• Estimate Lim Mag from plot of mag
• error vs. calib. mag for each color.

• Calibrate Magnitudes in each color filter using
  Stetson Standard Stars

R
R
Mag Error
No. of Standard Stars
Calibrated Magnitude
M (instrum) m (Standard Star)
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• Using Col 13 from Sept. 1, 2003 data, obtain

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Supernova Studies

• Four Distinct Projects
• Low Red Shift (Z 0.1) Type Ias
• Anchor Hubble Diagram for high Z SNe studies
  (Cosmology)
• Perlmutter, Aldering, Nugent, Woods-Vasey, Yale
  Group (Supernova Factory)
• Type II (Core Collapse) Supernovae
• Can these be used as Standard Candles?
• R. Ellis, Avishay Gal-Yam, Yale Group
• Intermediate Red Shift (0.1 Z 0.3) Type Ias
• Measure of w in Dark Energy
• Equation of state P w?
• Perlmutter, Aldering, Yale Group
• Type Ib,c SNes
• S. Kulkarni, et al.

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Expected Numbers of Supernovae

• Type Ia SNE
• Use Rate from R. Pain, et al. (APJ 577, 120,
  2002)
• Type II SNE
• Typically 2 mags fainter than Ias
• (Hamuy Pinto APJ 566, L63, 2002)
• About twice as numerous per unit volume as Ias
• (Capellaro, et al., AA 351, 459, 1999)
• Estimate numbers of SNes for 1000 square
  degrees, 15 day time window

Type Ia SNes
Type II SNes
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Study of Type Ia Supernovae

• Low Red Shift (Z lt 0.1)
• Need to calibrate Hubble Diagram for high Z SNe
  studies systematic studies of nearby Ias
• Rare, bright events
• m lt 18.5
• 10 SNe/1000 square degrees/15 day window
• Palomar-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-up
• Hawaii 2.2 m (Supernova Factory)

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• 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

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• Palomar-QUEST plan to collect a sample of low red
  shift
• (Z lt 0.1) Type IIs to establish (or otherwise)
  this correlation
• Discovery of Type IIs on QUEST drift scan in
  UBRI colors
• m peak lt 21
• 20 SNes/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 IIs from Type Ias 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
  correction
• Type Ia spread m 0.17

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• Intermediate Red Shift (0.1 lt Z lt 0.4)
• Goal measurement of w in p w?
• w lt -1/3 Dark Energy, w -1 Cosmological Const.
• Fainter, more frequent events
• 19 lt m lt22
• 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 QUEST
• Also good for search for Type II SNEs and Bob
  Zinns RR Lyrae study
• Need follow-up photometry for tails of light
  curves
• (Palomar 60?)
• Need spectroscopic follow-up of faint objects (m
  lt 22!)
• This is a problem - .

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Palomar-QUEST Science Projects

• Quasar Variability Survey ( 15000 sq degrees)
• Yale Group
• Gravitational Lensing of Quasars
• Yale Group
• High Red Shift Quasars Z 6
• G. Djorgovski, et al., and Yale Group
• Type Ia Supernova
• Perlmutter, Aldering, Nugent, Woods-Vasey, et
  al., with Yale Group (Supernova Factory)
• Type II Supernova
• R. Ellis, Avishay Gl-Yam and Yale Group
• GRBs, Tlype Ib,c Supernovae, Unusual Transients
• S. Kulkarni, et al., and G. Djorkovski, et at.
• Variation of with time
• Yale Group with Yale Atomic Physics Group U of
  Connecticut
• Minor Planet/Kuyper Belt Object Survey
• Mike Brown, et al., and D. Rabinowitz, Yale
• RR Lyrae Stars
• Yale (Bob Zin, Kathy Vivas, et al.)
• Near Earth Asteroid Tracking