Research School of Astronomy & Astrophysics Slide 1

SkyMapper

SkyMapper andthe Stromlo Southern Sky Survey

Stefan Keller, Brian Schmidt, Paul Francis and Mike Bessell

Research School of Astronomy & Astrophysics Slide 2

SkyMapper

What is SkyMapper?

• 1.35m with a 5.7 sq. degree fov

• To reside at Siding Spring Observatory

• First light in Dec 2006• To conduct a multi

colour/epoch Stromlo Southern Sky Survey

• Replacement for the 50” Great Melbourne Telescope

Research School of Astronomy & Astrophysics Slide 3

SkyMapper

Why a SkyMapper?

• There is 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 matched to Australian:– Science strengths;– Instrumentation (AAOmega, Gemini etc.), and;– Conditions – poor seeing a benefit cover the sky faster!

Research School of Astronomy & Astrophysics Slide 4

SkyMapper

The Stromlo Southern Sky Survey = S4

• Major component of SkyMapper telescope will be providing a survey of the southern sky– Multi-colour, multi-epoch of southerly 2 steradian – Star and Galaxy photometry (3% global accuracy) – Astrometry (better than 50 mas )– Cadence: hours, days, months and years. – Five years to complete– Data supplied to the community without

proprietary period as part of Virtual Observatory work

• Complementary to SDSS but w. improvements!

Research School of Astronomy & Astrophysics Slide 5

SkyMapper

Survey Science

The survey science goals are broad but some of the areas where I think SkyMapper stands to have largest impact are:

• 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?• Gravity and metallicity for on order of 100 million stars the assembly

and chemical enrichment history of the bulge, thin/thick disk and halo? • Extremely metal poor stars.• Undiscovered members of the local group• accurate photometric calibration of galaxy redshift surveys: 2dF/6dF.• bright z>6 QSOs probes of the ionization history of the Universe.

Research School of Astronomy & Astrophysics Slide 6

SkyMapper

SkyMapper Filter Set

Ex-atmosphere

Research School of Astronomy & Astrophysics Slide 7

SkyMapper

Expected S4 limits

  u vs g r i z

1 epoch 21.9 21.9 21.8 21.8 20.9 20.2

expt. time 55 35 25 25 15 15

6 epochs 22.9 22.9 22.8 22.8 21.9 21.2

Sloan Digital Sky

Survey comparison

22.0 n/a 22.2 22.2 21.3 20.5

Research School of Astronomy & Astrophysics Slide 8

SkyMapper

z – coverageSpectroscopic redshiftsr’<18 for SDSS

BJ<19.5 ( r’<18.5) for 2dFGRS

Photometric redshiftsSDSS to r’=20.5From SDSS EDR Csabai 2003

SDSS (EDR)

2dFGRS

S4 to provide:

Spirals to z~0.3-0.4

E0 to z~0.7

Research School of Astronomy & Astrophysics Slide 9

SkyMapper

• around 1.5% SUMSS detections are galaxies in the 2dFGRS (B<19.5)

• 30% are bright enough to appear in the DSS (B<22) [Sadler + Hunstead 2001]

The Stromlo Southern Sky Survey will go around a magnitude fainter than the DSS

photometric z ±0.06 for 30% of SUMSS

SkyMapper and SUMSS/SKAMPBy cross-comparison of radio and optical

sources we can ask:Which members of known classes of optical

objects are detected as radio sources? …and with redshifts we can ask:• How does the radio luminosity function

evolve with redshift?• Quantify 3D clustering of radio sources

SUMSS+DSSFrom Sadler & Hunstead 1999

Research School of Astronomy & Astrophysics Slide 10

SkyMapper

S4 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)

Research School of Astronomy & Astrophysics Slide 11

SkyMapper

S4 Data Products

How Much Data???

6 epochs x 6 colours x 4000 268,000,000 pixel images 150 Terabytes

+ 25 Terabytes of calibration images

1 Billion Objects observed 36 times with

Database is ~2 Terabytes (1 billion rows x 500 columns)

Research School of Astronomy & Astrophysics Slide 12

SkyMapper

A Concluding Timeline

• Funding Decision, Jun 2004• Optical elements ordered• Conceptual Design Review, Oct 2004• CCDs ordered, Feb 2004• Critical Design Review, August 2005• Pipeline development,

mirror Blank Failures, Sep-Oct 2005• Site Works begin Dec 2005• First Light, Dec 2006• Regular Operations, Apr 2007

Research School of Astronomy & Astrophysics Slide 13

SkyMapper

A Concluding Timeline

• Funding Decision, Jun 2004• Optical elements ordered• Conceptual Design Review, Oct 2004• CCDs ordered, Feb 2004• Critical Design Review, August 2005• Data reduction pipeline development,

mirror Blank Failures, Sep-Oct 2005• Site Works begin Dec 2005• First Light, Dec 2006• Regular Operations, Apr 2007