Dark Energy & Weak Lensing Science with Roman

Ami Choi NASA Roman Information Sessions July 6, 2021

Simulated image: M. Troxel What drives the accelerated expansion of the Universe?

Cosmological constant? Time-varying equation of state parameter?

GSFC/SVS

Departure from on cosmological scales?

NASA/WMAP 2 Complementary Measurements of and

redshift space cosmic shear distortions galaxy clustering galaxy clusters Roman Space “late-time structure” Telescope measurements, cosmic microwave background “Stage IV dark baryon acoustic oscillations energy supernovae experiment”

“expansion history”

sensitive to growth of structure of growth to sensitive sensitive to expansion

adapted from D. Gruen 3 Complementary Constraints on Dark Energy and Dark Matter DES Collaboration 2021 (Stage III DE Experiment) density of dark energy dark densityof equation of state parameter state of equation

density of dark matter 4 ~6 mo. over 2 years Roman’s Dark Energy Roadmap ~2 years

wide, medium, & deep imaging + slitless spectroscopy

adapted from Spergel+2015 SDT Report 5 Roman High Latitude Survey Team • Anahita Alavi (Caltech/IPAC) • Elisabeth Krause (U. Arizona) • Charles Shapiro (JPL/Caltech) • Rachel Bean (Cornell) • Chris Hirata (OSU, Weak lensing lead) • David Spergel (Princeton, CCA, Flatiron • Andrew Benson (Carnegie) • Alexie Leauthaud (UCSC) Institute) • Ami Choi (OSU) • Robert Lupton (Princeton) • Tomomi Sunayama (Nagoya U.) • James Colbert (Caltech/IPAC) • Chien-Hao Lin (Duke) • Masahiro Takada (U. Tokyo, IPMU) • Olivier Doré (JPL/Caltech, PI) • Makana Silva (OSU) • Peter Taylor (JPL) • Cyrille Doux (Penn) • Rachel Mandelbaum (CMU) • Harry Teplitz (Caltech/IPAC) • Tim Eifler (U. Arizona) • Dida Markovic (JPL) • Michael Troxel (Duke) • Xiao Fang (U. Arizona) • Elena Massara (U Waterloo) • Francisco Antonio Villaescusa-Navarro (Princeton) • Henry Gebhardt (JPL) • Dan Masters (Caltech/IPAC) • • Chen He Heinrich (JPL/Caltech) • Vivian Miranda (U. Arizona) Anja von der Linden (Stony Brook University) • Katrin Heitmann (ANL) • Hironao Miyatake (Nagoya U.) • Yun Wang (Caltech/IPAC, Galaxy redshift • George Helou (Caltech/IPAC) • Nikhil Padmanabhan (Yale) survey lead) • Shoubaneh Hemmati (Caltech/IPAC) • Kris Pardo (JPL) • David Weinberg (OSU, Galaxy clusters • Eric Huff (JPL) • Anna Porredon (OSU) lead) • Shirley Ho (CCA, Flatiron Institute) • Alice Pisani (Princeton) • Lukas Wenzl (Cornell) • Bhuvnesh Jain (Penn) • Eduardo Rozo (U. Arizona) • Hao-Yi Wu (Boise State) • Mike Jarvis (Penn) • Lado Samushia (U. Kansas) • Zhongxu Zhai (Caltech/IPAC) • Alina Kiessling (JPL/Caltech) • Mike Seiffert (JPL/Caltech)

6 High Latitude Spectroscopic Survey

HLSS Measurements: • Large-scale anisotropy (Alcock-Paczynzki) • Baryon acoustic oscillations (BAO) • Galaxy clustering/power spectrum shape • Beyond 2-point statistics of the galaxy field: • Redshift space distortions (RSD) higher-order stats, small-scale clustering, voids

Dark Energy & Weak Lensing with Roman — Ami Choi (OSU) 7 High Latitude Spectroscopic Survey • Development of simulation framework including galaxy • Enables optimization of survey strategy, validation, mocks and grism simulation predictions, forecasts including how systematics • Galacticus semi-analytic model (Benson 2012) tuned to high-z propagate to cosmology constraints observations • Paper describing reference survey in prep • Grism sims adapted from HST slitless spectroscopy tools

Zhai+2019, also see Merson+ 2018

Chuang+2015

e.g., WISP, HiZELS

aXeSIM (Kuemmel+2007) Fig 1 of Zhai+2021 8 High Latitude Spectroscopic Survey

Zhai+2019, also see Merson+ 2018 • Complicated selection function depends on, e.g., • Galaxy size and luminosity, line equivalent width • Redshift errors from line blending and misidentification • Example on left is prediction of H⍺ number counts based on galaxy mocks

Dark Energy & Weak Lensing with Roman — Ami Choi (OSU) 9 High Latitude Spectroscopic Survey

• Example of how line misidentification can shift and broaden the BAO peak

Massara+2020, also see Martens+2019

Mean of 50 Mean of 50 realizations in realizations in real space redshift space

Dark Energy & Weak Lensing with Roman — Ami Choi (OSU) 10 High Latitude Imaging Survey

HLIS Measurements: • Lensing by large-scale structure (cosmic shear) • Lensing around the positions of foreground galaxies (galaxy-galaxy lensing) • number counts (true mass • Foreground galaxy clustering (angular) can be weighed using lensing) true number

true mass

dark energy APS/Stonebraker Dark Energy & Weak Lensing with Roman — Ami Choi (OSU) 11 High Latitude Imaging Survey • HLIS was designed for systematics control (galaxy shapes in multiple Hemmati+2019 filters, multiple passes and dithers) • Can we accurately measure galaxy redshift distributions given the HLIS depth and specs? • Hemmati+2019 created a Roman analog sample based on CANDELS and used the self-organizing maps to investigate necessary spectroscopic calibration sample • Complete Calibration of the Color-Redshift Relation (C3R2) collecting spectra (e.g., Masters+2019, Stanford+2021)

Dark Energy & Weak Lensing with Roman — Ami Choi (OSU) 12 High Latitude Imaging Survey • Can we accurately measure galaxy shapes on our H4RG detectors? • Supplement extensive work by GSFC, Roman Detector, and Calibration WGs (e.g., Mosby+2020) to characterize non-linear effects like the brighter- fatter effect with: • cross-correlation analyses (Hirata & Choi 2020, Choi & Hirata 2020, Freudenburg, Givans+2020) • spot projection (Plazas+2017, Plazas+2018, Shapiro+2019) • Implement detector properties and survey specs to image simulations (Kannawadi+2016, Plazas+2016, Troxel+2021 Troxel+2021, Lin+2021) Dark Energy & Weak Lensing with Roman — Ami Choi (OSU) 13 Example of detector characterization for a single flight detector for various effects measured in super- pixels of 128 x 128 pixels from Freudenburg, Givans+2020

These maps are being integrated into the lensing simulations to understand impact on galaxy shape measurement

14 Roman Multi-Probe Forecasts

Eifler+2021

Dark Energy & Weak Lensing with Roman — Ami Choi (OSU) 15 Summary & Ongoing Work • In addition to systematics control, forecasts for the main probes, our team has also explored higher-order stats, how voids can constrain massive neutrinos, small scales, dwarf galaxy samples, modified gravity scenarios, and more (see link on next slide for full publication list) • Reference survey designs for 2000 deg2 High Latitude Wide Area Survey (imaging + spectroscopic, papers in prep) • uses simulation tools described earlier • illustrate strategy choice that meet scientific requirements • not necessarily what we will execute • Continued development of simulation framework (goal: end-to-end) • Continued forecasting, theory/measurement pipeline development • synergies with cosmic microwave background (e.g., Simons Observatory) • synergies with Euclid, Rubin LSST, SPHEREx, and more • leverage these to design pilot studies and Roman time later in the mission, plenty of trade space (depth vs area, spectroscopy vs imaging, number of filters vs area)

Dark Energy & Weak Lensing with Roman — Ami Choi (OSU) 16 References https://www.roman-hls-cosmology.space/ has a link to all publications with participation from our science investigation team • Hirata+2012 (arxiv:1204.5151) Exposure Time Calculator https://wfirst.ipac.caltech.edu/sims/tools/wfDepc/wfDepc.html • 2015 Science Definition Team Report https://roman.gsfc.nasa.gov/science/sdt_public/WFIRST-AFTA_SDT_Report_150310_Final.pdf • 2017 Annual Report for the cosmology SIT (arxiv:1804.03628) • Astro2020 Science White Paper (arxiv:1904.01174) • Stay tuned for upcoming papers describing the spectroscopic and imaging reference surveys

Dark Energy & Weak Lensing with Roman — Ami Choi (OSU) 17