Quentin Parker AAOMQ

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SkyMapper and prospects for narrow-band Imaging
surveys of the Southern Galactic plane

• Quentin Parker (AAO/MQ)
• on behalf of
• Stefan Keller, Brian Schmidt and Mike Bessell
  (ANU)

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What is SkyMapper?

• 1.35m robotic telescope with a 5.7 sq. degree
  field
• Sited at Siding Spring Observatory, NSW
• Will conduct a multi colour, multi epoch Stromlo
  Southern Sky Survey
• Is a replacement for the 50inch Great Melbourne
  Telescope that was destroyed ?

Rest in Peace
SkyMapper will measure the brightness and
positions of around a billion stars across the
southern sky to unprecedented accuracy.
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Skymapper!
early 2009
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Why a SkyMapper?

• There is currently no deep digital optical map of
  the southern sky
• no instrument is planned that can map the entire
  southern sky in multiple colours and epochs
• SkyMapper will provide an automated large-scale
  imaging capability that is well matched to
• Australian science strengths
• Instrumentation (AAOmega, Gemini access etc.),
  and
• Conditions poor seeing a benefit ? cover the
  sky faster!

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Overview

• SkyMapper designed and led by the ANU in
  Australia
• It is a 12.5M investment by the ANU
• It will be amongst the first of a new generation
  of rapid survey telescopes with high cadence
• We are entering a new age where survey telescopes
  such as VST, VISTA and SKymapper will lead to the
  generation of wide-field hemispheric multi-epoch
  digital surveys ? of massive size! (Peta byte)
• SkyMapper will give us the ability to dissect the
  Galaxy and understand its structure and formation

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The coming data deluge
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Skymapper Collaboration Policy

• Is a set procedure for non-ANU parties to gain
  access to general survey data during data
  characterisation period of approx. 18 months
  before First Data Release including establishing
  an MoU and authorship policy
• Access to non-survey observing time (25) is
  restricted to ANU applicants and agreed
  collaborators.
• External parties will require a primary
  investigator PI within the ANU and the PI
  should devote a substantial amount of time to the
  program.
•  Both Stefan Keller/Mike Bessell will lead the
  H-alpha programme inititally scope for MQ,
  VPHAS team involvement

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The installed Skymapper
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The SkyMapper instrument

• Designed by RSAA
• 32 4x2k CCDs
• Off-Axis Guider
• Shack-Hartmann feed
• Cooled with closed cycle cryogenic system
• 6 filter slots (note narrow-band surveys will
  require a manual filter wheel change not
  automatic)
• StarGrasp controller for CCD readout

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CCD performance

• 15s readout time
• 5e- readnoise
• 125000e- full well capacity
• linearity to 0.5
• QE gt 60 (400-850nm), QE gt 20 (300-950nm)
• Shutter Accuracy 1 on 1second exposure
• 0.5arcsecond pixels

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The Skymapper CCDs
0.5 arcsec pixels
UKST could cover maximum of 11x40sq.deg/night
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The Stromlo Southern Sky Survey Basic
characteristics

• Multi-colour, multi-epoch of all 20,000 sq.
  degrees south of equator (ugriz filter
  stromgren-like v)
• Data supplied to the community via Virtual
  Observatory
• Star and Galaxy photometry (3 absolute
  calibration)
• Astrometry to better than 50 mas
• Digital images available for download
  photometrically calibrated
• Accurate World Coordinate Systems for single
  images and combined images.
• Cadence 0, 4 hours, 2-3 days, 1-2 weeks and
  1-2 years
• Five years to complete
• Is thus complementary to the SDSS but with
  improvements ?

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Cadence and Coverage

• SkyMapper will be the fastest imaging survey
  telescope (to similar sky depth) in the world
• Comes on line in early 2009.
• Will allow astronomers to perform massive studies
  requiring large sky coverage quickly and
  efficiently.
• SkyMapper is the only survey telescope of this
  calibre in the southern hemisphere, providing a
  unique advantage.

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Skymapper Data Products

• Deliverables to the Outside User
• Data (epoch, RA, DEC, mags, galaxy shape info,)
  to be available through a web-served interface
  which provides catalogs over a user defined area
• Images to be available through a web-served
  interface which provides images over a user
  defined area (maximum size will be limited)
• Narrow bad survey data access may be different

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Skymapper Data Products

• How Much Data???
• 6 epochs x 6 colours x 4000 x 268,000,000 pixel
  images 150 Terabytes
• 25 Terabytes of calibration images ?
• 1 Billion Objects observed 36 times to provide a
  database that is 2 Terabytes in size (1 billion
  rows x 500 columns)
• We intend to supplement these data in selected
  regions such as the Galactic Plane with H-alpha
  images and later other narrow-band images making
  use of the 30 of Skymapper time not dedicated to
  the prime surveys

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Survey data will

• Provide a Galactic census of temperature
  gravity, metallicity and variability for 5
  billion stars
• ? the assembly and chemical enrichment history of
  the bulge, thin/thick disk and halo
• Provide a digital reference for radio, X-ray and
  GRB instruments
• Uncover extremely metal poor stars
• Uncover new dwarf galaxy members of the local
  group
• Discover large numbers of SNe
• Provide accurate photometric calibration of
  galaxy redshift surveys 2dF/6dF.
• Discover bright QSOs including those with Zgt6
• ? probes of the ionization history of the
  Universe.
• ? variability and evolution

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Non survey science identified

• Planet Transit studies
• Microlensing Studies
• Mapping Supernovae
• Widefield surveys in non-survey filters with the
  initial priority being H-alpha
• Narrow-band survey would start shortly after main
  surveys

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Main SkyMapper filter set

• A specially designed set of optical filters are
  placed in front of the camera to select the
  colour of light recorded.
• The innovative filter set provides unparalleled
  determination of the fundamental stellar
  parameters
• temperature, density and heavy element
  abundance.

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Broad-band SkyMapper Filter Set
Ex-atmosphere
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Expected Skymapper limits (1.5" seeing) for
signal-to-noise of 5 in AB mags
The Stromlo Southern Sky Survey will go around a
0.5-1 magnitude fainter than the DSS
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Rapid Survey era is emerging
2.4
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Possible H-alpha survey(s)

• Approximately 75 of the time on SkyMapper will
  be initially dedicated to the Southern Sky
  Survey.
• This leaves 25 for other projects including a
  H-alpha survey that can make effective use of
  BoM.
• Proposed 120sec H-alpha exposures with 25sec
  readout and 5.7sq.deg/exposure ? 1296
  sq/deg/night.
• SkyMapper has 1.174 LGP of UKST.
• Entire 4000sq.deg of SHS covered in 3.1 nights
  but 1mag shallower or 24 nights to same depth
  with 15min exposures
• SkyMapper pixel size 0.5arcsec (cf SCOS
  0.67arcsec)

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SuperCosmos H-alpha Survey (SHS)http//www-wfau.
roe.ac.uk/sss/halpha
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We are in the South!
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Narrow band SkyMapper filters

• Originally planned to re-use the AAO/UKST
  monolithic H-alpha filter (worth 46K in todays
  money)
• Unfortunately re-designs to filter wheel meant
  that the AAO/UKST filter would no longer fit into
  the required enclosure
• New H-alpha filter will be required and various
  options have been discussed (Mike Bessell)
• Decision made in March 2009 but will come from
  ANU funds with possible addition from MQ
• Additional narrow-band filters such as OIII and
  SII will be the subject of a LIEF bid led in
  May 2009 by ANU but with MQ/VPHAS participation
  (and possibly others)

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Proposed H-alpha filter
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Building on the main Skymapper surveys

• As with IPHAS, but with the added advantage of
  multi-epoch observations, the r and I band images
  can be combined with the H-alpha (and possibly
  other narrow-band images later) to provide
  powerful discrimination for point-source
  emitters.
• Multi-epoch observations permit elimination of
  variables

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Tangible community benefits

• The H-alpha filter will be available to any user
  of the SkyMapper telescope.
• This will allow a wider range of science to be
  conducted by the telescope, thereby increasing
  its user-base and scientific impact.
• The analysis of H-alpha data will be incorporated
  into a program to provide research experience for
  undergraduates.
• This program will assist in the retention of
  students to higher degree programs by engaging
  them in cutting edge science.
• The H-alpha filter will expedite the PhD thesis
  of Mr. Simon Murphy and form the basis of
  numerous theses in the future. It will facilitate
  Australian (Prof. Q. Parker, Macquarie
  University, Dr. M. Filopovic, Univ. Wollongong,
  Prof. A. Green, Univ. Sydney) and international
  (Prof. J. Drew, Imperial UK) collaborations with
  RSAA academics.

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H-alpha survey cost effectiveness leverage on
SkyMapper investment

• The proposed filter enables us to probe a
  specific region of the stellar spectrum for
  hundreds of thousands of stars in a single
  exposure.
• The alternative, obtaining a spectrum for each
  star, is simply not feasible.
• The H-alpha filter will turn SkyMapper into an
  efficient tool for locating these extremely rare
  glimpses into stellar birth and death across the
  southern sky.

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Skymapper H-alpha data

• The SkyMapper H-alpha filter will adds an
  additional dimension to the current SkyMapper
  program
• it opens up the study of the gas phase building
  on the success of the AAO/UKST H-alpha survey in
  the South
• The H-alpha data obtained together with the
  SkyMapper survey data
• It is intended to make the H-alpha data available
  to the world via the web after data validation
  and perhaps some preliminary exploitation (TBC)
• This develops an additional powerful data
  resource of benefit to the national and
  international communities

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Conclusions
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Possible H-alpha survey(s)

• Approximately 75 of the time on SkyMapper will
  be initially dedicated to the Southern Sky
  Survey.
• This leaves 25 for other projects including a
  H-alpha survey that can make effective use of
  BoM.
• Proposed 120sec H-alpha exposures with 25sec
  readout and 5.7sq.deg/exposure ? 1296
  sq/deg/night.
• SkyMapper has 1.174 LGP of UKST.
• Assume CCD 10xDQE of tech-pan film and filter of
  same quality and throughput ? x7.67 slower
  ?1.1mag less deep
• Entire 4000sq.deg of SHS covered in 3.1 nights
  but 1mag shallower or 24 nights to same depth
  with 15min exposures
• SkyMapper pixel size 0.5arcsec (cf SCOS
  0.67arcsec)

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Additional short 5-second survey

• Will be undertaken in photometric conditions
• Used for calibration of stars from 9-16th
  magnitude in all bands
• Will provide the calibration of the survey and
  will allow the survey to be tied to the
  Hipparchos and Tycho catalogs (and other
  photometric standard systems that are established
  in the southern hemisphere)
• Will ensure uniformity across the sky.

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Survey Science

• The survey science questions are broad and
  include
• What is the distribution of large Solar-System
  objects beyond Neptune?
• What is the history of the youngest stars in the
  Solar neighbourhood?
• How far does the dark matter halo of our galaxy
  extend and what is its shape?
• What is the detailed structure of our Galaxy and
  Magellanic clouds?