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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

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Pisco progress

PISCO Progress


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
Parallel Imager for Southern Cosmology Observations (PISCO):A Multiband Imager for Magellan

  • Antony Stark Smithsonian PI

  • Christopher Stubbs Harvard PI

  • Matt Holman Smithsonian — Planets, exoplanets

  • John Geary CCD electronics

  • Andy Szentgyorgyi Design consultant

  • Steve Amato CCD electronics

  • Michael Wood-Vasey Astronomer— Observing

  • Will High Thesis project, Harvard Physics

  • Andrea Loehr Astronomer — Observing algorithm

  • Brian StalderPostDoc, Harvard Physics

  • James Battat grad student, SAO

  • Armin Rest PostDoc— Photo-z Software

  • Steve Sansone LPPC machine shop

Dichroic in cube optical layout
Dichroic in Cube Optical Layout

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.

Current best desgin
Current best desgin

Design is 1.42 meters (56 inches) from focus to focus

Design uses S-FPL51 glass

Adc operation
ADC Operation

  • Can use PISCO on Clay telescope

  • Consists of two rotating cylindrical prisms,

    • 1 cm thick

    • airspaced, multi-coated

  • Initial scientific mission can be achieved without ADC

  • ADC can be removed with re-focus

Pisco design concept
PISCO Design Concept

Small Guider Housing

Cable Wrap


Dewar Wall


Dichroics & CCDs


Electronics mounted here

Some optics have been ordered
Some Optics Have Been Ordered

  • Contract in place with Barr Associates for fabrication of Dichroic Cubes

  • This has a long lead time (8 months) and will drive the project timetable

Electronics are done
Electronics are done…

  • We have already taken images in the lab with full control-to-image software.

  • Readout noise is OK (3 electrons).

  • Readout speed is OK ( < 8 seconds).

Initial detector tests look favorable

Initial detector tests look favorable

Tested 2 3K x 6K 10 micron high-rho devices in Univ of Hawaii test system.

Read noise

Dark current vs. temperature

CTE via Fe55 xrays

Gain via Fe55 xrays

Analysis software we ll build upon supermacho essence image analysis pipeline

Analysis Software: We’ll build upon SuperMacho/ESSENCE image analysis pipeline

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.

Flow diagram for real time cluster redshift analysis pipeline
Flow diagram for real-time cluster redshift analysis pipeline

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.

Tightly coupled software observing
Tightly coupled software/observing pipeline

Take Image 1

30 sec

Analyze Image:

flatten, WCS, sextractor

Galactic reddening corr.

Produce z, sz



Take Image 2

30 sec

Offset if appropriate

More images

Slew to next target

Photometric redshift for clusters
Photometric Redshift for Clusters pipeline

  • Photo-z’s for individual galaxies tend to have scatter of sz/(1+z)~0.03, but with a few “catastrophic” outliers.

  • Combination of morphology, magnitude, color and location can be used to establish cluster’s redshift.

  • Robust statistics can be used to eliminate “outliers”.

Uniform exposure times for clusters
Uniform exposure times for clusters pipeline

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.

One night to obtain 115 cluster redshifts at z 1 5
One night to obtain 115 cluster redshifts at z < 1.5 pipeline

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.

South pole telescope 2007 first look data
South Pole Telescope pipeline2007 First-Look Data

  • SPT data, Feb-April 2007

  • 4 square degrees shown

  • red circles are known quasars

  • green regions are significant

  • negative regions in CMB: possible clusters

  • Current, upgraded SPT detector system shows two order of magnitude improvement in observing speed.

Magellan observations of spt cluster candidates
Magellan Observations of SPT Cluster Candidates pipeline

LDSS3 multi-color photometry of SPT-selected region nr01

Abell 267, extrapolated to various redshifts pipeline

and observed with PISCO

Order of detection by pisco
Order of detection by PISCO pipeline

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.

We are building the capability to efficiently chase sz detections in optical
We are building the capability to efficiently chase SZ detections in optical

  • Blanco Cluster Survey (with Mohr et al)

  • Imaging with existing Magellan instruments

  • Spectroscopy with existing magellan instruments

  • Custom simultaneous multiband imager, PISCO

Ask a restricted set of questions
Ask a restricted set of questions detections in optical

  • At a known position on the sky, is there a cluster of galaxies?

  • What is the redshift of the cluster?

    • We initially assume all galaxies are LRG’s

    • We make a redshift estimate based on this assumption

    • We use magnitude consistency to select the LRGs.

    • We then use a clustering algorithm to search for clustering in redshift space.

  • This is not the general problem of finding a photo-z for some random galaxy.

  • We are focusing on “luminous red galaxies”, LRG’s.

Why lrg s
Why LRG’s? detections in optical

  • These elliptical galaxies are preferentially found in custers, so they exhibit “clustering” more than, say, spirals.

  • They suffer minimal extinction/reddening due to dust in the galaxy, which can distort colors and therefore photo-z’s

  • They’re bright, and are crude standard candles, which helps in photo-z determination.

Photometric redshift principle
Photometric Redshift Principle detections in optical

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

Status of observations
Status of Observations detections in optical

  • Reduction of BCS data under way

    • Flatfielding to better than 1%

    • Astrometric registration

    • Source Extractor photometry

    • Photo-z determination under development

  • Deep multiband images of initial SZ 2 degree region at (RA,DEC), plus similar region at arbitrary location for statistics

  • Long slit and muli-slit spectroscopy of selected galaxies in NR1 region

  • Additional nights both allocated & requested

  • Source extractor photometry
    Source Extractor Photometry detections in optical

    • Used mag_auto fluxes from SE

    • Determine galaxy colors and uncertainties

    A cluster photo z estimator
    A cluster photo-z estimator detections in optical

    • Use Blanton’s K-correct code to predict SDSS colors for LRG vs. redshift.

    • Assume all galaxies are LRG’s

    • For each galaxy, for each trial redshift, compute

      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

    Forward modeling of lrg spectra
    Forward modeling of LRG spectra detections in optical





    3 d color evolution with redshift
    3-d color evolution with redshift detections in optical

    Example of color distances vs redshift
    Example of color distances vs. redshift detections in optical

    Overall distance

    Photo-z estimate

    What about r band magnitude
    What about r band magnitude? detections in optical

    • We can use the apparent magnitude to select out likely LRG’s.

    • They’re bright, r ~ 17th at redshift = 0.1

    • At other redshifts the r band magnitude has two contributions,

      m(z)=m(0.1) +  DM + D K_corr(z)

      cosmology filter/SED

    Change in apparent magnitude due to passband redshift and luminosity distance

    detections in optical m=0.27





    K correction


    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

    Compare this with observations
    Compare this with observations detections in optical

    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

    SDSS LRG’s

    Demand lrg consistency
    Demand LRG consistency detections in optical

    • Use colors and assumption of LRG spectrum to estimate the redshift

    • Use lookup table to find typical LRG magnitude at this redshift

    • Compute magnitude difference.

    • Allow for galaxies to be up to Mcut magnitudes fainter than the LRG line.

    Compare photoz and spectroz s
    Compare photoz and spectroz’s detections in optical

    Cut to require lrg magnitude
    Cut to require LRG magnitude detections in optical

    Lrgs only
    LRGs only detections in optical

    Lrg catalog is produced
    LRG catalog is produced detections in optical

    • RA, DEC, photoz, photoz error, magnitudes and colors with uncertainties, color distance vectors and statistics.

    • Next task is to ask if there is a statistical overdensity in redshift within SPT angular footprint

    Cluster finding
    Cluster finding detections in optical

    • Visual inspection of BCS and Magellan followup images suggest a cluster of galaxies that coincides with NR1 region.

    • Cluster detection is multiparameter search

      • Position

      • Size

      • LRG cutoff magnitude

      • Redshift histogram binning width

    Cluster finding1
    Cluster finding detections in optical

    • We have multiple cluster detection algorithms under development.

    • One example:

      • Map out redshift distribution in an area A

      • Determine background redshift distribution in 8 surrounding regions. Use this as background estimate.

      • Compute histogram of excess or deficit relative to this local background redshift distribution.

    A cluster at z 0 3 in nr01
    A Cluster at z = 0.3 in nr01 detections in optical

    Recommendations detections in optical

    • We are close to being able to write a paper on SZ detection of clusters (author list?)

    • It would help a lot to have a radio color discriminant for clusters (i.e. non-detection at 220 GHz, stronger detection at 90 GHz)

    Australia telescope compact array atca observations of spt clusters
    Australia Telescope Compact Array detections in optical (ATCA) observations of SPT clusters

    • Antony Stark Smithsonian Astro Obs

    • Wilfred Walsh U. New South Wales Asia

    • Joe Mohr U. Illinois

    • Tom Crawford U. Chicago

    Relevance to spt cluster survey
    Relevance to SPT Cluster Survey detections in optical

    • SPT system is around 100 Jy/K

    • SPT-SZ survey will be 10 μK rms per beam

    • Point continuum sources that are 1 mJy or brighter will make a significant contribution to the data, and possibly affect the detection of clusters and their derived parameters.

    • The number of such sources in SPT bands is poorly known.

    • With the ATCA, we can actually search for and detect such sources in SPT clusters.

    Pilot study completed
    Pilot Study Completed detections in optical

    • We were actually awarded a significant amount of observing time on ATCA

    • “Extragalactic” time slot is undersubscribed, and not too hard to get observing time

    • We observed 24 X-ray selected moderate redshift clusters (Mullis et al. 2003) in redshift range 0.05 < z < 0.65

    • Observe at 18 GHz, because of ATCA sensitivity and map area; possible follow-up at 90 GHz

    • Detected one source at ~ 2 mJy at 18 GHz

    • Our sensitivity was primarily limited by phase stability—we will need good weather

    Current status
    Current Status detections in optical

    • Funded through Smithsonian Institution for expenses related to these observations.

    The end

    THE END detections in optical


    Science opportunities
    Science Opportunities detections in optical

    • Supernova followup observations

      • Type Ia and type II Sne as cosmological probes

      • Requires multiband images, multiple epochs

  • Photometric redshifts of clusters

    • 4 band imaging over 5 arcmin field

  • Transient followup

    • Evolution of SED for GRBs

    • Microlensing light curves

  • Planetary occultations

    • Multiband data useful for discrimination

  • Followup camera for PanSTARRS/LSST

  • Masses and radii of transiting extrasolar planets
    Masses and radii of transiting extrasolar planets detections in optical

    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.