Hubble Tension and Cosmic Voids W DArcy Kenworthy

Hubble Tension and Cosmic Voids W. D’Arcy † Kenworthy , Dan Scolnic ‡, Adam † Riess † Department of Physics and Astronomy, Johns Hopkins University ‡ Department of Physics, Duke University Based on work published in Ap. J DOI: 10. 3847/1538 -4357/ab 0 ebf ar. Xiv: 1901. 08681 W. D’Arcy Kenworthy, wkenwor 1@jhu. edu, (704) 497 -7230 1 Johns Hopkins University

What is the Hubble Constant? W. D’Arcy Kenworthy, wkenwor 1@jhu. edu, (704) 497 -7230 2 Johns Hopkins University

Measuring the Hubble Constant Mpc SN 1994 D, a type Ia supernova. Type Ia supernovae serve as standardizable candles, thereby measuring distance to distant galaxies W. D’Arcy Kenworthy, wkenwor 1@jhu. edu, (704) 497 -7230 Hubble Diagram: Logarithmic plot of distance against redshift. 3 Johns Hopkins University

What is the Hubble Tension? Measurements of the Hubble constant over time, expanded from Freedman 2017 W. D’Arcy Kenworthy, wkenwor 1@jhu. edu, (704) 497 -7230 4 Johns Hopkins University

Hubble Tension Today Modern measurements of the Hubble constant. Proposed theoretical solutions are shown at top, measurements at the bottom W. D’Arcy Kenworthy, wkenwor 1@jhu. edu, (704) 497 -7230 5 Johns Hopkins University

Can a Cosmic Void solve the Hubble Tension? • Void: under-dense region of space • Underdensity increases local Hubble constant • Keenan, Barger, and Cowie 2013 found 30% underdensity within 300 Mpc of Milky Way • Whitbourn and Shanks 2014 found 20% underdensity within 220 Mpc • These studies cover minority of the sky Grey, underdense region will expand more quickly than black background W. D’Arcy Kenworthy, wkenwor 1@jhu. edu, (704) 497 -7230 6 Johns Hopkins University

How Can We Test this with SNe Ia? • Are SNe at low ( • Largest sample of spectroscopic SNe Ia used to date • 1054 total at redshifts • Measure ) redshift too bright? for each SN Ia, look for a step Figure 5: Mockup Hubble diagram. Blue line shows exaggerated effect of a local void distance-redshift relation W. D’Arcy Kenworthy, wkenwor 1@jhu. edu, (704) 497 -7230 7 Johns Hopkins University

How Can We Test this with SNe Ia? • Are SNe at low ( • Largest sample of spectroscopic SNe Ia used to date • 1054 total at redshifts • Measure ) redshift too bright? for each SN Ia, look for a step Figure 5: Mockup Hubble diagram. Blue line shows exaggerated effect of a local void on the distance-redshift relation W. D’Arcy Kenworthy, wkenwor 1@jhu. edu, (704) 497 -7230 8 Johns Hopkins University

Variation in the Hubble Constant Figure 8: Hubble constant relative to background against redshift. Each point represents ~80 SNe. Blue shading shows expected variance in the Hubble constant at low redshift due to local structure W. D’Arcy Kenworthy, wkenwor 1@jhu. edu, (704) 497 -7230 9 Johns Hopkins University

Voids at Arbitrary Distances? Figure 11: Difference in when measured above and below. At no redshift is there evidence for a void biasing the local measurement of the Hubble constant. W. D’Arcy Kenworthy, wkenwor 1@jhu. edu, (704) 497 -7230 10 Johns Hopkins University

State of the Hubble Tension • Our precision is 0. 61%, compared to 1. 91% from SH 0 ES • Theoretically disfavored at 20σ • Local structure cannot resolve Hubble tension • Independent direct measurement of • New physics in early universe W. D’Arcy Kenworthy, wkenwor 1@jhu. edu, (704) 497 -7230 from H 0 li. COW 11 Johns Hopkins University

Questions? W. D’Arcy Kenworthy, wkenwor 1@jhu. edu, (704) 497 -7230 Johns Hopkins University