1. Atacama Large Millimeter/submillimeter Array Expanded Very Large Array Robert C. Byrd Green Bank Telescope Very Long Baseline Array Radio Sky Surveys for Cosmology for Future-Generation Radio Facilities Steven T. Myers National Radio Astronomy Observatory Socorro NM

2. Launchpoint With new observational facilities, instruments and surveys coming online this decade and next, we will observe galaxies & environments near and far – galaxies are full of incendiary gas, abrasive dust grains, noxious chemicals, and nuclear waste… But, we want to use them as a force for good – COSMOLOGY!!! I will describe opportunities in the radio to sub-mm part of the spectrum Radio Futures, Dec 20152

3. Astro2010: A Game of Questions The Themes – Cosmic Dawn – Physics of the Universe – Discovery, Origins, Cosmic Order, Frontiers of Knowledge The Questions – How do cosmic structures form and evolve? – Why is the universe accelerating? – What is the fossil record of galaxy assembly and evolution from the first stars to the present? – How do baryons cycle in and out of galaxies and what do they do while they are there? Radio Surveys can play a role in all these key problems Many of these are cosmological in nature Most of these have barely started this decade… Astro2010 Decadal Survey: One of the worst Massively Multiplayer Online (MMO) games ever! Co$ting = World of Spreadsheets! Radio Futures, Dec 20153

4. Disclaimer (the fine print) This will not be a review talk, I will leave stuff out There will be little detail of the physics behind the effects and techniques What I will not talk about … – Cosmic Microwave Background – Sunyaev-Zeldovich Effect – Pulsars as probes of long-wavelength Gravity Waves – Tomography of the Hydrogen Epoch of Reionization e.g. the stuff cosmologists are usually keen on (others will discuss these during workshop) I steal stuff from others, like – SKA Science Book https://www.skatelescope.org/books/https://www.skatelescope.org/books/ – NGVLA Science White Papers https://science.nrao.edu/futures/ngvla/documents- publicationshttps://science.nrao.edu/futures/ngvla/documents- publications – my brain (highly biased with information retrieval issues) … side effects may include: brain fog, Bayesian fever, stringy theory, cosmic variance, mid-scale enervation Radio Futures, Dec 20154

5. I. Radio Sky Surveys from a radio survey of the sky… … to a survey of the Universe Radio Futures, Dec 20155

6. Radio Sky Surveys: What are they? Imaging the sky (continuum, spectral cube, polarimetry) detecting and measuring properties of objects or emission Classic Sky Survey – cover an area of sky to some depth and angular resolution finding and measuring objects. Useful for multiple astrophysical studies, large discovery space! “Intensity Mapping” – a low-resolution deeply confused Direct Imaging Survey unable to distinguish objects but able to detect and measure statistics of aggregate emission, usually in a spectral cube Targeted Survey – observations of a specific set of targets, usually a statistical sample, probably defined and selected in a different waveband or at a different angular resolution Radio Futures, Dec 20156

7. Classic Radio Sky Surveys 56 years since 3C and 32 years since 3CRR 20 years since NVSS and FIRST! Science based on surveys comprise a steadily increasing fraction of VLA publications New capabilities New capabilities – OTF mosaics, wide fractional bandwidths for increased continuum sensitivity, instantaneous spectral index determination, polarization New scientific opportunities New scientific opportunities – reach cosmic (z>1) depths and source densities (comparable to O/IR) – multi-messenger surveys can approach cosmology with different systematic errors Pan-STARRS 7

8. Tiered Survey Constructon: Deep and Wide From a survey of the Sky to a survey of the Universe! Survey representative volumes of the Universe – Local Universe: ALL-SKY Includes Galaxy & Zone of Avoidance – Distant Universe:  Deep Fields Reach key sensitivity levels – Example: Deep Fields 1.5  Jy = L * radio continuum at z=2 Metric: Survey Speed – SS = Area/Time at some defined depth (e.g. 0.1 mJy/beam) – scaling: 8Radio Futures, Dec 2015

9. 1I. Radio Sky Survey Science Examples Radio Futures, Dec 20159 Charting the Cosmos

10. Radio Continuum Surveys sensitive to AGN (dominant >> 1mJy) and star-forming galaxies (<1mJy) example surveys: – radio galaxy continuum surveys (& ISW) – polarimetric surveys and cosmic magnetism – radio weak lensing – radio strong lensing – cluster plasma physics Radio Futures, Dec 201510

11. Cosmic Lab: Late Integrated Sachs-Wolfe Radio Futures, Dec 201511 Decay of potentials in LCDM cause signature in CMB – Cross correlate CMB with large-scale structure tracers – WMAP and Planck (2013 Paper 19) used NVSS (3-5  ) – radio N(z) is broad, probe to high redshift

12. Headline Science: Faraday Tomography Science: – map our Galactic B – B through the cosmic web – evolution with z NVSS+: Taylor, Stil, Sundstrom 2009 – 3x10 4 sources, ~1/deg 2 VLASS (2016-2024): – conservative estimate – 2x10 5 sources, ~ 6/deg 2 Future surveys (SKA) – 1000/deg 2 for cosmic web – sky area limited (10deg 2 10nJy rms) Radio Futures, Dec 201512

13. Radio Gravitational Lensing Measure gravitational potentials through lensing distortion – strong lensing  multiple images and high magnification – weak lensing  distortions of shapes of sources Weak Lensing – Dark Energy evolution – cluster DM halos – need high source density Strong Lensing – galaxy & group DM halos – microlensing – very model dependent Radio Futures, Dec 201513

14. Radio Weak Lensing Tangential shear (stretch) in outer weakly lensed regions Core of mass profile produces strong lensing arcs (Einstein radius) Look for presence of coherent shear signal above (random?) intrinsic shapes From Williamson et al. 2007   Forecasted constrains on cosmic shear power spectrum with a 3GHz 1.5  Jy 10deg 2 DEEP survey   first deep radio data set that can obtain a statistically significant weak-lensing signal. ~3 sources / arcmin 2 c/o M. Brown High enough source density of galaxies for weak lensing studies – Probe higher z than optical lensing surveys. – Different systematics than optical (PSF known) – direct measurement of shapes in uv plane – Polarization can help identify intrinsic position angles Radio Futures, Dec 201514

15. Radio Weak Lensing Tangential shear (stretch) in outer weakly lensed regions Core of mass profile produces strong lensing arcs (Einstein radius) Look for presence of coherent shear signal above (random?) intrinsic shapes From Williamson et al. 2007   Forecasted constrains on cosmic shear power spectrum with a 3GHz 1.5  Jy 10deg 2 DEEP survey   first deep radio data set that can obtain a statistically significant weak-lensing signal. ~3 sources / arcmin 2 c/o M. Brown High enough source density of galaxies for weak lensing studies – Probe higher z than optical lensing surveys. – Different systematics than optical (PSF known) – direct measurement of shapes in uv plane – Polarization can help identify intrinsic position angles Radio Futures, Dec 201515 Early steps! This year on ArXiv:1507.05977 Cross-correlation cosmic shear with the SDSS and VLA FIRST surveys Constantinos Demetroullas, Michael L. Brown

16. Radio Strong Lensing Find, measure, monitor multiple image (or arc) systems – in cm wavelength for radio continuum emission – in mm/sub-mm for dust continuum (U/LIRGS) What you can measure – lens model: DM halo shape and profile (cuspy?) – time delays: can extract H 0 measurement, model dep. What you need – large samples, go deep mm/sub-mm is very promising due to LF – accurate imaging and monitoring Radio Futures, Dec 201516 Credit: ALMA (NRAO/ESO/NAOJ)/Y. Tamura (The University of Tokyo)/Mark Swinbank (Durham University).

17. Deep ignorance on origin and evolution of cosmic B fields – Affects cosmic ray transport – Role in cluster gas heating? – Trace galaxy/cluster interactions The AGN ICM connection – feedback on galaxy formation – affects use of SZE for cosmology? Cluster Lab: Role of B fields in the ICM X-ray cavities correspond to radio lobes = feedback? Radio Futures, Dec 201517 Baum et al., NASA, ESA, HHT Hercules-A

18. Cluster Lab: Relics and jets in Abell 2256 Owen et al. 2014 (arXiv:1408.5931) High-resolution (A- configuration) radio X-ray ICM emission in red Filamentary shock region outside core of cluster. Merger? Plasma Weather – connection to ICM and DM halo “climate” evolution? CAUTION: clusters and plasma physics more complicated than we think and are prepared to model! 10 18 Radio Futures, Dec 201518 arXiv:1408.5931 Radio surveys can provide important indicators on astrophysics of cosmological test objects

19. Radio Line Surveys Detect and measure galaxies in line emission – bulk atomic and molecular gas: HI, CO, CII – masers as signposts Lines  Redshifts – if independent distance indicator  peculiar velocities can probe cosmic flows & large-scale grav. potentials – if can get 2D astrometry, can reconstruct 3D velocities Example surveys – HI galaxy surveys – CO galaxy surveys – (mega)maser surveys for H 0 and astrometry Radio Futures, Dec 201519

20. Radio Line Probes 1 - Atomic Hydrogen (weak transition) – HI line (rest 1.42 GHz, z=1.5 at 568 MHz) – single line in “ clean ” part of spectrum single line redshift determination almost assured 2 - Molecular CO (strong transition) – CO ladder (1-0 rest 115.27 GHz, z=1.5 at 46.11 GHz) – whole J ladder of lines (115,230,345,460…) no ambiguity in redshift if multiple transition seen – congested area of spectrum danger: many weaker lines could contribute to correlated signal 3 - C+ (158  m, 1.9THz) – CII line very bright, redshifted from THz into sub-mm Radio Futures, Dec 201520

21. Radio Line Cosmology Approaches Large HI spectroscopic surveys – intensity mapping – “Billion Galaxy Survey” – non-Gaussianity from HI bi-spectrum – weak lensing of velocity profile (Morales) – peculiar velocities Large CO spectroscopic surveys – intensity mapping – CO galaxy surveys can combine with Continuum surveys – weak lensing (& strong) – other continuum probes (ISW) Radio Futures, Dec 201521 From Bower et al. arXiv:1510.06432

22. Radio Dark Energy (BAO) Overview Maartens etal. (arXiv:1501.04076) EoR for Low-band array HI spectroscopic survey – intensity mapping for SKA-1 – Billion Galaxy Survey for SKA-2 Continuum survey – weak lensing (& strong) Radio Futures, Dec 201522

23. 23 Final Fantasy MMXXX: SKA-2+ Billion Galaxy HI spectroscopic survey to z > 1.5 Astro2010 white paper: Myers et al. arXiv:0903.0615 Radio Futures, Dec 2015

24. Ultimate Radio Cosmology Combine a large HI galaxy survey with a radio weak lensing survey – different systematics to O/IR equivalents (DETF) Radio Futures, Dec 201524 A w-machine – 10 9 galaxy BAO survey – also weak lensing (continuum) – target 0.01 in w Design Driver – target precision requires survey speed of 4 x 10 9 m 4 K -2 deg 2 – a km 2 area w/ 10 deg 2 FOV – would also like to identify individual galaxies (need arcsecond resolution) – survey database for other science Rawlings et al. SKA Science Book

25. Other Radio Cosmology Surveys Astrometric Surveys – long baseline techniques have unsurpassed accuracy  as accuracy or better goals – continuum: AGN proper motions (Darling et al. 2013) see the Hubble expansion??? – line: megamaser surveys for H 0 and proper motions And wait, there’s more – absorption line surveys, fundamental constants – Supermassive Black Holes & cosmology? there must be a connection (beyond galaxy growth) can we find first SMBH in and beyond the EOR? Radio Futures, Dec 201525

26. IV. Final Thoughts one step beyond … Radio Futures, Dec 201526

27. Upshot Extremely high discovery potential for radio cosmology surveys – line and continuum surveys complementary (& w/OIR) – tremendous ancillary multi-use survey science – key Dark Energy and Dark Matter cosmology – crosses m/cm/mm/sub-mm wavebands in different tracers – pushes technology to maximize survey speeds (incl.  ) Soapbox: If we want >$1G facilities in 2020+ or 2030+, we should use our new & existing facilities now (and in the future including modest upgrades or retooling) to their practical limits in demonstrating the potential of these key projects, especially for high-risk high-reward approaches Radio Futures, Dec 201527

28. Radio Futures, Dec 2015 The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. www.nrao.edu science.nrao.edu 28