Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://www.naic.edu/~astro/chicago2/talks/Myers-Next_Generation_Radio_Arrays.pdf Äàòà èçìåíåíèÿ: Tue Aug 22 00:15:31 2006 Äàòà èíäåêñèðîâàíèÿ: Sun Dec 23 00:56:13 2007 Êîäèðîâêà: Ïîèñêîâûå ñëîâà: 2df survey

Next Generation Radio Arrays:
CMB and Early Universe Astrophysics
Steven T. Myers
National Radio Astronomy Observatory Socorro, NM
U.S. m/cm Community Workshop ­ 03 Aug 2006

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Cosmology Questions
· How was the Universe born, how did it evolve, and what is its future? · What is the dark sector ­ "dark energy" and "dark matter" ­ made of? · What happened during the cosmic "Dark Ages"?
from Report of the Radio,Millimeter, and Submillimeter Planning Group (RMSPG), Oct 2005

also see Connecting Quarks to the Cosmos

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Key Events in the Early Universe
· Planck era ­ 10
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GeV

­ string gas era? extra dimensions?

· Inflation - 1015 GeV?
­ Reheating ­ create matter and radiation

· Baryogenesis ­ establish matter-antimatter asymmetry
­ coupled to phase transition? (GUT, EW)

· Nucleosynthesis ­ create light nuclei (H,He,Li,...) ~ 3min · Matter-Radiation Equality (z~10000) · CMB decoupling ­ recombination (z~1000) ~ 400,000yrs · Relics: cosmic paleontology
­ radiation (CMB), neutrinos, gravity waves, scalar gravitational potential fluctuations, dark matter, dark energy, spacetime structure, exotica (defects, primordial black holes)
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Where we are: 2006

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2006 : The Big Mysteries
· Cosmography
­ ­ ­ ­ CMB nearly isotropic, Universe nearly homogeneous nearly flat geometry Universe expanding, currently accelerating 3 macroscopic accessible spatial dimensions

· Standard Cosmological Model ­ ingredients
­ 24% matter, 20% dark (higher in past?) ­ 76% "dark energy" (lower in past? or tracking?) ­ baryons subdominant, negligible anti-baryons

· Particle Physics
­ many candidates for Dark Matter! (WIMPs, axions) ­ neutrino oscillations (possible sterile species) ­ vacua poorly understood (why is Dark Energy so small!)
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2006 ­ the players
· CMB
­ WMAP plus balloon and ground-based (Boomerang, ACBAR, CBI) ­ snapshot of Universe at z=1000, in linear regime

· Large Scale Structure
­ SDSS and 2DF and Ly- surveys
· combine with CMB (e.g. ISW correlation)

­ weak lensing surveys (e.g. CFHT) ­ Xray and O/IR cluster surveys
· allow measurement of "growth factor" cosmology

· Other
­ SNe-Ia measure current acceleration of Universe ­ dark matter searches, neutrino observatories ­ study dark matter in galaxies through lensing, velocities

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State of the Art: WMAP 3-yr (2006)
· · · · Hinshaw et al. (2006) released March 2006 TT & TE spectrum (right) ILC vs. 61GHz foreground model
WMAP limitation: poor 3rd peak determination

Reionization ~0.1 "bump" at low

Courtesy WMAP Science Team http://lambda.gsfc.nasa.gov
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Danger Ahead - polarized foreground

Courtesy WMAP Science Team

WMAP 3-yr 22 GHz polarization map (galaxy)
- linear scale 0 to 50 K
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Beyond WMAP: high- TT spectrum
· CMB angular power spectrum to high
­ detected past 6th peak ­ well into damping tail ­ consistent with Standard or Concordance Models ­ agreement of ACBAR, Boomerang, CBI, DASI, VSA and WMAP3 at < 1000 is excellent

·

At 2000 < <3500, ACBAR, CBI & BIMA find power ~ 3 above the standard models
­ Not consistent with any likely model of discrete source contamination ­ Suggestive of secondary anisotropies, especially the SZ effect
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Note: sensitivity poor at 3rd peak and beyond ­ not yet precision cosmology!

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CMB Pol EE: CBI + WMAP3

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CMB Pol EE: + others

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Uncanny Agreement
· CMB Polarization
­ E-modes: pol at 0°,90° to wave vector
· from density perturbations and GW

­ B-modes: pol at ±45° to wave vector
· only from Gravity Waves

·

EE Predictable from TT oscillations
­ from velocity, EE 90° out-of-phase vs. TT [sin(ks) vs. cos(ks)]

·

Primarily controlled by curvature
­ comoving distance to recombination ­ WMAP TT spectrum consistent with flat Universe (k=0) ­ check whether EE pattern is at predicted position

EE spectrum shifted as expected
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Where we will be: 2010

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CMB Task Force Report
· Rai Weiss (MIT) chair
http://www.nsf.gov/mps/ast/tfcr_final_report.pdf

· Science 1 ­ large angle polarization from inflation
­ phased program of ground + ballon space (2018)

· Science 2 ­ small-scale anisotropy & SZ effect
­ coherent ground-based program ­ within scope of general-use radio instruments

· Science 3 ­ intensity & polarization foregrounds
­ focus is above 20 GHz, but clear connections to cm/m wave

· Technology development
­ ­ ­ ­ big bolometer cameras and coherent focal-plane arrays alternative approaches development towards CMBpol satellite mission also theory, modeling, analysis algorithm development
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Dark Energy Task Force
· NSF / DOE / NASA joint, reviewed white papers
­ not yet released (but some people have copies)

· set down clear metrics for performance
­ figure of merit ~ area in w ­ dw/dz plane ­ relative to Stage II (current ongoing projects) ­ near-term Stage III (DES, Pan-STARRS, CCAT)

· towards big-ticket Stage IV (JDEM,LSST,SKA,other)
­ SNe1a surveys, weak lensing, BAO, cluster surveys ­ SKA prominent (HI structure/BAO, weak lensing, maser H0)

· my impressions
­ ­ ­ ­ big winner: weak lensing (O/IR) not-so-good: SNe-Ia (only factor 2 gain after Stage 3) best combo: WL plus BAO jury out on: SKA contributions
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Next big thing: Planck!

·

Planck sensitivity, frequency & sky coverage critical:
­ ­ ­ ­ TT: 3rd and higher peaks! reach lensing BB modes push towards tensor BB modes determine foregrounds
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Figures courtesy Martin White
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B-modes: Planck Projections
Planck "error boxes"

Hu & Dodelson ARAA 2002

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Current & Future "CMB" Experiments
· Beyond Planck (a sampling):
­ ­ ­ ­ ­ ­ ­ ACT [6m] (Chile) ­ high- CMB SZA [8x3.5m] (OVRO) ­ clusters, high- CMB South Pole Telescope [8m] (SP) ­ cluster counts QUaD [2.6m] (SP) ­ CMB polarization QUIET [2m,7m] (Chile) ­ B-modes from ground Atacama 25-meter (Chile) ­ FIR/sub-mm SPIDER [2m] (Balloon) ­ B-modes from LDB

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CMB Power Spectrum Goals
· EE and BB (lensing, inflation)
Current BB rms WMAP3 ~ 0.02K2 Current CBI+DASI BB limits ~ 1K2

1 nK! Gravity-wave B-modes: for T/S=0.001

B-modes from Lensing: reachable from ground.

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The Next Generation: beyond 2010

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Beyond 2010 ­ the players??
· CMB ­ still the cleanest probe
­ working towards CMBpol (r<0.01 territory) ­ how well will we know the foregrounds? ­ are big bolometer cameras the answer?

· Large Scale Structure
­ DETF Stage IV surveys ­ cluster (SZ and O/IR, maybe Xray) census to z=3? ­ what about radio?

· Other
­ ­ ­ ­ ­ the era of Gravity Wave Observatories (LISA, pulsars)! will we know H0 to 1%? will we know the density profile of galaxies in inner core? particle physics beyond LHC? will string theory make better sense?
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The CMB Foreground Challenge
· Further progress in CMB astronomy will require the understanding and removal of foreground emission (solar system, galactic, extra-galactic) to unprecedented levels (10-100 nK) · Note ­ at 1cm in one square arcmin : 1K ~ 1Jy · To image the CMB at these levels one images the entire Universe between z=0 and z=1000! = Whole Universe Imaging · This is in full polarization... · Frequencies from 20 GHz ­ 900 GHz! · Looking at continuum, but beware of line contamination at these levels.
Plot from Barth Netterfield's talk at Irvine, March 2006 http://www.physics.uci.edu/CMB/
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Aside: a CMB Mega-Array?
· CBI, DASI, & VSA have demonstrated the utility of interferometry for CMB (particularly for polarization) · sensitivity limited by number of elements
­ detectors near quantum limit, need more throughput ­ would need 100-1000 elements 104 ­ 106 "pixels" (10-110x DASI)

· would require massive wide-band correlators
­ development of "inexpensive" large-scale correlators ­ already being explored for other next generation big arrays (ATA,SKA)

· would be competing against bolometer & MMIC arrays
­ but systematics cleaner complementary!

· risky & expensive, but worth exploring...
­ detailed cost analysis: will NOT be a ~ $10M experiment ­ leverage off other next generation radio array development...
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Towards the next Decadal Review
· What will radio astronomy be doing for cosmology?
­ CMB studies are cm and mm-wave radio astronomy!
· CMB & foreground studes are large multi-band sky surveys

­ Fundamental distance scale work still important ­ Growth of structure in universe probes cosmology

· How do we tie our facilities into the Big Questions?
­ What observations can we do for CMB foregrounds? (surveys)
· sub-mJy source pops, 1-20 GHz sky surveys (we are behind SDSS)

­ Will SKA fulfill DETF needs? (is HI the focus?) ­ Will we have sensitive VLBI capability beyond 2010? (underrated)
· how far can we push astrometry? VLBI is a truly unique capability

· What do we do besides our big facilities?
­ radio instrumentalists being trained in small CMB & URO groups ­ technology crossover (FPAs, correlators) ­ support for theory, analysis, algorithm work
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If we do nothing else...
· provide complete Sky Surveys
­ NVSS & FIRST a good start, but 10 years old now ­ these are used all the time by wide range of astronomers! ­ but reliability is an issue

· we want
­ 1-20 GHz at 1" or better, good fidelity, sub-mJy ­ especially low-surface brightness sensitivity, to 5'
· can combine with "CMB" images at larger scales

­ 30MHz-1 GHz in key bands, e.g. HI to ???Mpc ­ a grand radio atlas: radio part of a "Google Sky"

shame on us if we don't provide this basic service

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