THE LARGE SYNOPTIC SURVEY TELESCOPE Ian Shipsey Purdue University Purdue University (for the LSST Collaboration) DPF2009, July 27, 2009 I. Shipsey DPF 2009 1
Progress in Astronomy Progress in Astronomy • Bigger Telescopes: Keck to GSMT • Angular resolution: Hubble to JWST • All Sky Survey: SDSS to LSST All Sky Survey: SDSS to LSST I. Shipsey DPF 2009 2
8 meter wide-field ground-based telescope ground based telescope providing time-lapse digital imaging of faint astronomical objects across the bj t th entire visible sky every few nights for 10 years. y I. Shipsey DPF 2009 3
Comparison of LSST To Keck Comparison of LSST To Keck Primary mirror Field of view diameter (full moon is 0.5 degrees) 0 2 d 0.2 degrees 10 m Keck Telescope 3.5 degrees LSST I. Shipsey DPF 2009 4
100 billion billi over entire sky I. Shipsey DPF 2009 5
Image sizes LSST, Moon, HST g , , I. Shipsey DPF 2009 6
LSST LSST survey of 20,000 sq LSST survey of 20,000 sq deg LSST f 20 000 f 20 000 d deg (half the sky) (half the sky) (half the sky) (half the sky) • 4 billion galaxies with 4 billion galaxies with redshifts g redshifts • Time domain: Time domain: 5 million asteroids 5 million asteroids 5 million asteroids 5 million asteroids 10 10 million supernovae million supernovae 1 million gravitational 1 million gravitational lenses lenses 100 million variable stars 100 million variable stars 100 million variable stars 100 million variable stars + new + new phenomena phenomena I. Shipsey DPF 2009 7
LSST 4 Science Missions Dark Energy-Dark Matter Inventory of the Solar System Multiple p Find 90% of investigations into hazardous NEOs the nature of the down to 140 m dominant over 10 yrs & test components of the components of the theories of solar theories of solar universe system formation “Movie” of the Universe: time domain Mapping the Milky Way Discovering the Map the rich and transient & complex p unknown on structure of the time scales galaxy in days to years unprecedented detail and extent detail and extent All missions conducted in parallel I. Shipsey DPF 2009 8
LSST Science Drivers 1 The Fate of the Universe Flat universe Ω total = 1.02+/-0.02 Pie chart of universe WMAP 25 Λ cosmological constant O pen no cosmo. constant S tandard 24 standard model 23 d e m a gni t ud A cce l e r a t ing 22 U ni ve r se D ece l e r a t ing 21 U ni ve r se Dark Energy “the essence of space” 20 0.2 0.4 0.6 1.0 r e d s hi ft r e d s hi ft Dark Matter “most of the matter” Together they govern the evolution & fate of the universe fate of the universe. Their nature ranks as one of the greatest questions in the physical sciences I. Shipsey DPF 2009 9
Probing Dark Energy = P ρ P ρ = − Is the accelerated expansion a cosmological constant ? Is the accelerated expansion a cosmological constant ? w w / / 1 1 Or does w vary with time, now evolution − ± � w 1 0.2, ⎛ ⎞ equivalently red shift, z? z 0 = + ⎜ ⎟ w w w status: ± � 0 1 w + + 0 a ⎝ ⎝ ⎠ ⎠ 1 1 z z a a • The probe of dark energy is the expansion history of the universe, = � a parameterized by the Hubble parameter H(z) ( ) H z a a Cosmic distances are proportional to integrals of H(z) -1 over redshift. • • H(z) can be constrained by measuring: Angular diameter Angular diameter Luminosity distances distances of of standard candles standard rulers (Type 1a SNe) (baryon acoustic (baryon acoustic oscillations). Weak Lensing Surveys & Galaxy Cluster Surveys probe growth of structure & angular diameter distances LSST uses all techniques in synergy I. Shipsey ICHEP 08 8/1/08 Abs.#931 10
Gravitational Lensing & Shear Red galaxy on axis strongly lensed. other galaxies weakly lensed: sheared images l i kl l d h d i Circular bkgd what is galaxies observed Weak ea Lensing shear pattern less obvious less obvious variable shape but bkgd galaxies detectable statistically y • Cosmic Shear is the systematic and correlated distortion of the C i Sh appearance of background galaxies due to weak gravitational lensing by the clustering of dark matter in the intervening universe. The shearing of neighboring galaxies is correlated because their light The shearing of neighboring galaxies is correlated, because their light follows similar paths on the way to earth. Cosmic shear: ~ 0.01 e.g. circular galaxy → ellipse with a/b ~ 1.01 I. Shipsey ICHEP 08 8/1/08 Abs.#931 11
1 st Detections of Cosmic Shear The simplest measure of cosmic shear is the Whitman 2000 2-pt correlation function of the ellipticities 145,000 galaxies measured with respect to ~1 degree ~1 degree angular scale angular scale. < + θ > i ( ) ( ) e r e r Log ellipticity correlation No dark energy Ω (DE) =0.67 10 100 More recent survey θ arcminutes CFHT (2006) 1.6 million galaxies ~20 sq degree ~20 sq degree I. Shipsey DPF 2009 12
LSST and Cosmic Shear 20° 2° 10’ 1’ CFHT LSST 1.6 million galaxies 3 billion galaxies ~20 sq degree 20,000 sq. degrees • Same 2-pt correlation function • Fourier transform � power spectrum as a function of multi-pole moment (similar to QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. are needed to see this picture. CMB t CMB temperature maps). t ) • The growth in the shear power spectrum with the red shift of spectrum with the red shift of linear non-linear the background galaxies is very sensitive to H(z) . This provides the constraints on dark energy. the constraints on dark energy. • 3-point correlations will also be possible I. Shipsey DPF 2009 13
Baryon Acoustic Oscillations • Prior to the formation of atoms (recombination) the baryons are tightly coupled to the radiation in the universe. WMAP WMAP • An overdensity perturbation gives rise to an acoustic wave in this tightly coupled fluid, which propagates p p p g outward at the speed of sound • After recombination, the matter and radiation decouple. The sound speed radiation decouple The sound speed drops to zero, and the propagating acoustic wave stops. • This gives rise to a characteristic scale in the universe: 150 Mpc, the distance the sound waves have traveled at the These acoustic waves are time of recombination. time of recombination. visible as the peaks in the CMB i ibl th k i th CMB power spectrum. I. Shipsey DPF 2009 14
Baryon Acoustic Oscillations • Following recombination, gravitational instability causes the birth of stars and galaxies and galaxies. • Gravitational coupling between dark matter and between dark matter and baryons creates an imprint of the acoustic oscillations in the galaxy distribution. • This persists as the universe More data this time expands, although it gets as a power spectrum 1 st observation 1 observation weaker with time. k ith ti SDSS Eisenstein Same physics as CMB (Z~1100) et al (2005) Compilation Compilation but at a time when Dark but at a time when Dark 40,000 galaxies Percival(2007) Energy is becoming important (z<3) 0.16<z<0.47 I. Shipsey DPF 2009 15
Baryon Acoustic Oscillations • Following recombination, gravitational instability causes the birth of stars and galaxies and galaxies. • Gravitational coupling between dark matter and between dark matter and baryons creates an imprint of the acoustic oscillations in the galaxy distribution. • This persists as the universe More data this time expands, although it gets as a power spectrum weaker with time. k ith ti Same physics as CMB (Z~1100) Compilation Compilation but at a time when Dark but at a time when Dark Percival(2007) Energy is becoming important (z<3) I. Shipsey DPF 2009 16
Baryon Acoustic Oscillations and LSST • How the length scale • How the length scale evolves with redshift is dependent on the Hubble parameter Hubble parameter and therefore sensitive to dark energy • Measure the galaxy angular power g p spectrum at different red shifts. Require high statistics over the redshift range. f SDSS LSST 40 000 galaxies 40,000 galaxies 3 billion galaxies 3 billion galaxies 0.15 <z<0.6 0.15 <z<3 Simulations of LSST measured galaxy power spectrum divided by a featureless reference power spectrum, shifted vertically for clarity I. Shipsey DPF 2009 17
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