PISCO Progress. Carnegie A. Szentgyorgyi for A. Stark 20 March 2008. P arallel I mager for S outhern C osmology O bservations (PISCO): A Multiband Imager for Magellan. Antony Stark Smithsonian PI Christopher Stubbs Harvard PI Matt Holman Smithsonian — Planets, exoplanets
A. Szentgyorgyi for A. Stark
20 March 2008
Revised Optical Design of PISCO. Steve Schectman contributed to this design. The dichroics are embedded into cubes of fused silica, so that there is no difference in dielectric constant on either side of the dichroic. This allows the dichroics to be used at 45º. The dichroics are placed in the telecentric beam from the focal reducer, so all field positions have identical ranges of angle of incidence at the dichroics. The overall length of the instrument is reduced to 1.6 meters, and all CCDs are in a single, medium-sized dewar.
Design is 1.42 meters (56 inches) from focus to focus
Design uses S-FPL51 glass
Small Guider Housing
Dichroics & CCDs
Electronics mounted here
Tested 2 3K x 6K 10 micron high-rho devices in Univ of Hawaii test system.
Dark current vs. temperature
CTE via Fe55 xrays
Gain via Fe55 xrays
Battle tested over past 6 years at CTIO for SM and ESSENCE surveys.
Flatten with dome flats, fringe flat and sky flats
Astrometric WCS registration, warp to fixed plate scale
Photometry to 1%
CVS code management, easy to add new modules
Parallel implementation, Condor on Linux boxes
Robust and self-tracking
Honed on crowded fields
Need to add (1) cluster photo-z module, and (2) SQL database
Armin Rest, pipemeister, coming to CfA in Spring 2007.
We expect that within 30 seconds of acquiring the first image, we will have produce an appraisal of whether the second 30 image will add enough integration time to obtain a cluster photometric redshift at the requisite SNR. We have in hand the middleware and pipeline structure for this, from the ESSENCE and SuperMacho surveys. We are missing only the final segment, namely the redshift estimator, which we will develop in parallel with the construction of the hardware.
Take Image 1
flatten, WCS, sextractor
Galactic reddening corr.
Produce z, sz
Take Image 2
Offset if appropriate
Slew to next target
Magnitudes in the four filter bands (shaded) for L*/2 early type galaxies, and exposure times (in seconds, unshaded) to achieve SNR=10, as a function of redshift. The table assumes galaxy flux integrated in a 2.2 arcsec diameter aperture, in seeing of 0.8 arcsec at an airmass of 1.2 in dark time. The numbers assume deep depletion detectors in the z and i bands, like those for the SMI. The exposure time needed to achieve SNR=10 is reasonably well matched across the bands. A minimum exposure time is 5 sec.
The time needed to obtain 115 cluster redshifts, in good conditions, is 8.2 hours. It will not be possible to obtain redshifts for the ~10% of clusters with redshift z > 1.5; these will be flagged to obtain redshifts using other instruments.
LDSS3 multi-color photometry of SPT-selected region nr01
and observed with PISCO
8 bright red galaxies detected first (green circles)
Black-circled detected next
Blue dots are cluster galaxies
Black dots are foreground
Histogram of photo-z of the first 18 galaxies and photo-z of the color-magnitude selected galaxies.
The plots show how the observer-frame spectrum of a Luminous Red Galaxy (LRG) depends upon its redshift. The redshifts are indicated in the upper left corner of each panel. The flux ratios between the g, r, i, and z bands is a good indicator of galaxy redshift, as the 4000 Å break moves across the spectrum. We will develop real-time analysis code that will produce an initial cluster redshift result within 30 seconds of the acquisition of an image.
From M. Blanton’s web page
error-weighted distance to prediction, for each color
4. Using distances for all 3 colors, calculate composite color distance vs. z
5. Pick z with minimum normalized color distance
6. Estimate redshift uncertainty by finding dz that produces color distance = 2
m(z)=m(0.1) + DM + D K_corr(z)
detections in optical m=0.27
(LRG’s)Change in apparent magnitude due to passband redshift and luminosity distance
Note: this ignores potential age effects in stellar population
Luminosity function work suggests we normalize to
r = 17 at redshift of 0.1
SDSS reg. galaxies
Fudged LRG cut:
r_cut = (predicted r(z)) - 2.5*redshift - offset
Introduce an empirical correction vs. redshift to correct for evolutionary effects
The dashed lines correspond to loci of constant mean density. The symbols indicate the nine known transiting planets, along with Jupiter and Saturn. Two symbols are shown for OGLE-TR-10b. In green is the result based on a fit to the OGLE photometry and available radial velocities (Konacki et al. 2005). In blue is the Holman et al. (2005) result, based on a simultaneous fit to Magellan photometry and the same radial velocity measurements.