Direct Probes of H0 Jim Braatz (NRAO)

Precision Cosmology with the CMB Planck CMB sets framework for modern cosmological models, but it needs external constraint from the local universe to break fundamental degeneracies. In the base ΛCDM cosmology with a cosmological constant in a geometrically flat universe, Planck predicts H0 = 67.8 +/- 0.9 km s-1 Mpc-1 (Ade et al. 2015)

WMAP and Planck Map the CMB In the base ΛCDM cosmology, Planck predicts H0 = 67.8 +/- 0.9 km s-1 Mpc-1 (Ade et al. 2015; Planck paper XIII) Best current measurements based on standard candles: H0 = 73.8 +/- 2.5 km s-1 Mpc-1 (Riess et al. 2011) H0 = 74.3 +/- 2.6 km s-1 Mpc-1 (Freedman et al. 2012) Updated from Ade et al. 2013; 2015

Measuring an Accurate, High-precision H0 Short-term goal (~2 years): A robust ~3% measurement that reaches general agreement from multiple, independent direct methods Longer-term goal: A direct ~1% measurement to complement future CMB observations. Independent H0 measurement can place strong constraints on basic physics models, especially neutrino mass (Σmν), and DE equation of state (e.g. Sekiguchi et al. 2010, Di Valentino et al. 2015). Di Valentino et al. 2015

Constraints on Neutrino Mass Oscillation experiments demonstrate Σmν > 50 meV Without priors, the CMB-S4 detection of Σmν may be significant at only ~2σ For a CMB-S4 experiment, a prior on H0 at the ~percent level provides the best additional constraint on neutrino mass Manzotti, Dodelson & Park (2015)

Constraints on DE Equation of State To complement Stage 4 CMB experiments, an external measurement of H0 provides the best constraint on the DE Equation of State A 1% measurement of H0 will reduce the error on w by a factor of 2 Manzotti, Dodelson & Park (2015)

A 1% Goal for H0 with Standard Candles To approach 1%, must simplify the distance ladder and improve anchor calibration. Two approaches: Geometry => Cepheids => SNIa (Only ~9 SNIa with Cepheid calibration) Use RR Lyrae and TRGB rather than Cepheids (CHP II) Gaia parallaxes will improve calibration of Cepheids, RR Lyrae zero point, and TRGB method

Gravitational Lens Time Delays (with apprecation to Sherry Suyu, Chris Fassnacht, Leon Koopmans) RXJ1131 Time delay: Obtain from lens mass model Cosmography requires: Identifying the best lenses Time delays Lens mass model Mass along line of sight Suyu et al. 2013

Current Focus of Lensing Studies (H0LiCOW) B1608+656 RXJ 1131-1231 Individual distances have ~5-8% uncertainties in best cases.

Current Constraints from CMB+RXJ1131 Lens data also show tension with Planck CMB w = -1.53 ± 0.2 “phantom” range Most physical models of DE have w > -1 Suyu et al. (2014)

Optical Lensing Studies Sensitive, high-res imaging required for lens mass model. So, HST. Ground-based AO imaging also under investigation. Challenge: modeling the PSF Current projects such as Hyper Suprime-Cam Survey (HSCS) and the Dark Energy Survey (DES) will discover ~103 lenses Future telescopes and surveys, especially Euclid and LSST, will identify ~104 lensed QSOs

Radio Lensing Studies Optical lensing surveys and monitoring will dominate the field until SKA turns on. Radio discovery and monitoring would then lead; SKA expected to discover ~104 lensed QSOs. The large sample will permit selectivity to minimize systematics in measuring distances. SKA (radio) + Euclid (NIR) are well-matched in coverage, sensitivity, and resolution, making them complementary for studying both the lens and the background QSO. B0631+519 with HST and MERLIN 1.7 GHz From these large samples, detailed studies of ~50 lensed QSOs would enable percent-level determination of H0

Measuring H0 with H2O Megamasers The MCP is an NRAO “Key Project” with the goal of determining H0 precisely by measuring geometric distances to galaxies in the Hubble flow. Mark Reid Jim Condon Fred Lo Christian Henkel Cheng-Yu Kuo Feng Gao Wei Zhao Violetta Impellizzeri Eugenia Litzinger Jenny Greene Anca Constantin Lei Hao Dom Pesce

Steps to Measuring H0 with the MCP The MCP is an NRAO “Key Project” with the goal of determining H0 precisely by measuring geometric distances to galaxies in the Hubble flow. Survey with the GBT to identify maser disk galaxies Image the sub-pc disks with the High Sensitivity Array (VLBA+GBT+EB+VLA) Measure accelerations in the disk with GBT monitoring Model the maser disk dynamics and determine distance to the host galaxy

H2O Megamaser Disks NGC 6323 Mrk 1419 NGC 2273 IC 2560 J0437+2456 NGC 5765b UGC 3789 NGC 6264 NGC 1194

UGC 3789

UGC 3789 dynamic spectra Pesce et al. 2015

Bayesian Estimation of the H0 PDF from Megamasers We use a custom MCMC code by Mark Reid Inputs: (x, y, vLOS, aLOS) for each maser spot Global parameters: D (or H0 directly) MBH (x0, y0, V0) of dynamical center PA, inclination Up to 4 parameters to describe the position angle & inclination warping [eccentricity] For UGC 3789: D = 49.6 ± 5.1 Mpc H0 = 68.9 ± 7.1 km s-1 Mpc-1 (Reid et al. 2013)

NGC 5765b

Estimation of H0 from Geometric Distances H0 = 67.6 ± 4.0 km s-1 Mpc-1 (6%) UGC 3789 49.6 ± 5.1 Mpc H0 = 69 ± 7 (Reid et al. 2013) NGC 6264 137 ± 19 Mpc H0 = 68 ± 9 (Kuo et al. 2013) NGC 6323 107 ± 42 Mpc H0 = 73 ± 26 (Kuo et al. 2015) NGC 5765b 126 ± 11 Mpc H0 = 66 ± 6 (Gao et al. 2015)

Estimation of H0 from Geometric Distances H0 = 67.6 ± 4.0 km s-1 Mpc-1 (6%) UGC 3789 49.6 ± 5.1 Mpc H0 = 69 ± 7 (Reid et al. 2013) NGC 6264 137 ± 19 Mpc H0 = 68 ± 9 (Kuo et al. 2013) NGC 6323 107 ± 42 Mpc H0 = 73 ± 26 (Kuo et al. 2015) NGC 5765b 126 ± 11 Mpc H0 = 66 ± 6 (Gao et al. 2015) In ~2 years the MCP will finalize observations and analysis for 5 additional galaxies, and should achieve < 4% total uncertainty. Along with other members of the H0 community, we are now adopting “blind” analysis strategies to eliminate personal bias

Most Recent Disk Maser Discovery New megamaser in CGCG 074-064 will be the focus of MCP observations in the coming year.

Toward a 1% H0 with Megamasers Current suite of GBT+VLA+EB+VLBA, enables a ~4% H0 measurement. With ~10X the VLA collecting area and continental baselines, we could set the goal to measure ~100 galaxies at ~10% each, to achieve 1% H0. A 5+ year project. With ngVLA sensitivity, we would be able to measure galaxies out to ~300 Mpc, which would alleviate concerns over systematics induced by a local void (e.g. Bohringer et al. 2015).

Summary Independent measurement of H0 will continue to be a powerful complement to analyses of the CMB, and enable accurate cosmology. Current measurements of H0 at the ~3% level are in tension with Planck predictions based on ΛCDM. A robust determination of H0 requires agreement from multiple, independent methods to counter unknown systematics. Future 1% measurement of H0 will complement a CMB-S4 experiment to determine neutrino mass and constrain DE models. Measurements from lensing and megamasers may be able to approach 1% solutions beyond the next decade.

The End

By Measuring SMBHs We Learn How Galaxies Evolve M-σ Relation M-σ Relation (Maser masses only) McConnell & Ma (2013) Updated from Greene et al. 2010

Multiple Methods for Measurement of H0 Update to Fig. 16 Ade et al. 2013 (Planck paper XVI)

CMB-S4 sensitivity

NGC 4258, “The Maser Galaxy” Miyoshi et al. 1995

Measuring Distances to H2O Megamasers: A Geometric Measurement D = r/ a = Vr2/r D = Vr2/a

Progress with Megamaser Surveys 162 galaxies detected out of > 3000 observed ~ 37 show spectra indicative of a disk and are suitable for MBH measurement ~ 10 suitable for distance measurement Primary sample for surveys: Type 2 AGNs at z < 0.05

Ultra-high resolution mapping with the HSA: It’s all about the signal-to-noise Should have mentioned that two of the key advocates for VLBA sitting in the audience: Marshall Cohen and Tony Readhead For sensitivity, the MCP adds the GBT, EB, and phased VLA to the VLBA The GBT enables self-cal on the maser line, greatly improving efficiency /D ~ 0.33 mas

UGC 3789: Systemic Features

UGC 3789: Blue Features

Constraints on DE Equation of State In the context of Stage 4 CMB experiments, an external measurement of H0 at the percent level provides the best additional constraint on the DE Equation of State Manzotti, Dodelson & Park (2015)

A Sample of GBT Spectra of Disk Masers