Surveys of Cosmic Populaons: Overview

Eric Feigelson (Astronomy & Astrophysics, Penn State)

Statistical Modeling of Cosmic Populations Penn State Summer School June 2014 Astronomical Surveys

Astronomers have been conducting all-sky (or at least, wide-field) surveys of the celestial sphere for centuries:

• 2nd c BC: 41 constellations, Hipparchus (Greece) • 2nd c: Almagest, ~1K stars, Ptolemy (Egypt) • 8th c: Dunhuang Star Chart, Tang Dynasty China • 10th c: Book of Fixed Stars, al-Sufi (Persia) • 17th c: Uranometria, Bayer (Germany) • 18th c: Atlas Coelestis, ~3K stars, Flamsteed (England) • 19th c: Bonner , ~300K (Germany) • 19th c: Carte du Ciel, ~5M stars (France) • 20th c: USNO-B1.0, ~1G stars (USA)

• 1770s: 103 nebulae, Messier (France) • 1880s: ~8K nebulae, NGC catalog, Dreyer (Ireland) • 1990s: 20K galaxies, 3rd Ref Cat, de Vaucouleurs (USA) 2nd century Roman statue • 2000s: ~1G, , Gunn et al. (USA) `Farnese Atlas) showing Hipparchus’ star catalog Faint Images of the Radio Sky at Twenty-centimeters (FIRST)

811,000 radio sources 1990s Infrared Astronomical Satellite (IRAS)

Early 1980s 350,000 mid-IR sources in all-sky survey Two-Micron All Sky Survey (2MASS)

Early 2000s 300,000,000 stars and galaxies ROSAT All-Sky Survey (RASS)

100,000 X-ray sources plus diffuse emission

eROSITA survey 2015-19 ~4M sources expected gal clusters, AGN, stars Large Area Telescope Fermi Observatory

20 MeV – 300 GeV

1,873 sources 2011 Star counts: The first flux limited surveys

For a uniform population of objects distributed randomly in transparent space: S = L / 4 π D2 V = 4/3 π D3 Num obj ~ V ~ S-3/2 logN ~ -1.5 logS

William Herschel (1785) used deviations from this prediction to infer that the Universe (now known as our Galaxy) is limited in extent (~1 kpc) and is elongated in shape. Star counts at different Galactic latitudes

halo

disk

The Galaxy has multiple components with different spatial distributions producing strong deviations from the logN~-1.5 logS law.

Bahcall & Soneira 1980 The universe at faint magnitudes. I - Models for the galaxy and the predicted star counts But, near the Galacc plane, space is very opaque due to interstellar dust. Thus, Herschel’s galaxy is ~20 mes too small, which was not appreciated unl the 1930s.

Big effort in 1910-50s to address the “Fundamental equaon of stellar stascs” to simultaneously establish the distribuon of stellar luminosies and their spaal distribuonin the Galacc disk:

A (S,l,b) = [D(r,l,b) F(L,Abs(r,l,b)) r2 dr

A = number of stars/deg-2 in flux interval around S towards direcon (l,b). (Star count data) D = number of stars/pc-3 at distance r from Earth towards (l,b) F = normalized distribuon of stellar luminosies (LF) corrected for spaally-dependent absorpon

Fredholm Type 1 integral equaon solved by Taylor expansion, Fourier transform, numerical integraon. This effort essenally failed in the disk due to the patchy absorpon, but funcons reasonably well towards the Galacc poles (b=90o).

Trumpler & Weaver “Stascal Astronomy” 1953 Stellar populations & kinematics in the Galaxy New catalogs with 4-6 dimensions of phase space: (α,δ) Location in the sky π Parallax giving distance (µα, µδ) Proper motion across the sky Vr Radial velocity

50,000 stars have all 6 values measured, 100,000 have 5 values, 30M have 4 values (Hipparcos, UCAC2, Gen-Cop, RAVE,…). GAIA will revolutionize Galactic (~2017).

Fascinating structure: • Thin disk, thick disk, halo components of Galaxy • Trace star formation around Sun • Halo streams & cannibalized galaxies

Little sophisticated statistical work has been performed on these catalogs (e.g. mixture models, wavelet analysis) Milky Way halo ~ star streams from cannibalized dwarf galaxies

Model results

Observations of the Sagittarius dwarf galaxy streams

Monaco et al 2007 Some contemporary cosmology surveys

Galaxy/ spectroscopic survey (clustering, BAO, gal evoluon, AGN feedback) • WiggleZ: WiggeZ (Australia) • GAMA: Galaxy & Mass Assembly (St Andrews/ESO/… consorum) • DEEP2: DEEP2 Galaxy Redshi Survey (large consorum) • J-PAS: Javalambre-PAU Astrophysical Survey (Mexico) • LAMOST: LArge-sky-area MulObject Spectroscopic Telescope (China) • HETDEX: Hobby-Eberly Telescope Dark Energy Experiment (Univ Texas) • (e)BOSS: Baryon Oscillaon Spectroscopic Survey (SDSS consorum) • VIPERS: VIMOS Public Extragalacc Redshi Survey (ESO)

Mul-epoch photometric surveys (SN Ia, AGNs) • DES: Dark Energy Survey (FNAL/OSU/UPenn/… consorum) • Pan-STARRS: Panoramic Survey Telescope & Rapid Response System (Hawaii) • CRTS: Catalina Real-Time Transient Survey (Caltech) • SkyMapper: SkyMapper (ANU) • DES: Dark Energy Survey (FNAL/OSU/UPenn/… consorum) Cosmic micowave background survey (era of recombinaon, inflaon, cosmological models, Dark Energy, grav waves, nucleosynthesis, …) • BICEP: Robinson Gravitaonal Wave Background Telescope (Caltech/JPL) • Planck: Planck satellite (ESA) • SPT: South Pole Telescope (Chicago/UCB/CWRU consorum)

21-cm surveys (Hi during era of reionizaon) • LOFAR: LOw-Frequency Array (Netherlands) • MeerKAT: Karoo Array Telescope (South Africa) • ASKAP: Australian SKA Pathfinder (Australia)

Mulwavelength pencil-beam surveys (gal formaon & evoluon, AGN, dust) • GOODS: Great Observatories Origins Deep Surveys (HST/Chandra/Spitzer/Herschel/VLA/Keck/VLT • CANDELS: Cosmic Assembly Near-infrared Deep Extragalacc Legacy Survey Astrophysical Simulaons: Surveys without observaon

z=18.3

z=5.7

z=0.0

Millennium Simulation Springel et al. 2005 Common observaonal challenges in surveys

• Data cleaning (cosmic rays, detector noise, bad pixels, …) • Flux calibraon, bright object saturaon • Noise characterizaon • Faint source detecon • Source characterizaon (flux, extent, variability, color/SED, class)

• Survey coverage in RA/Dec • Survey coverage in flux sensivity • Volume limited survey? • Edge effects (RA/Dec, velocity, distance, …) • Astrometry & catalog cross-matching • Data processing & database management • Data release, documentaon & promulgaon (reproducibility)

Summary

Astronomers have been surveying the sky since anquity, cataloguing, classifying & characterizing vast numbers of celesal objects.

In the 21st century, due in part to the spectacular scienfic success of the Sloan Survey, tremendous resources are being placed on the development of new surveys.

Surveys place new demands on the astronomical community to develop high levels of skill in statistical and computational methodology, to complement our existing skills in astronomy and astrophysics.