Speaker
Description
The primary two methods for measuring the Hubble constant – forward modeling of CMB fluctuations and distance ladder measurements – disagree at a level that is statistically significant. A third method, known as the bright standard siren method, could add another competitive measurement to the fray, potentially pointing to a resolution of the aforementioned tension. This direct method calibrates a value of the Hubble constant by measuring distances to neutron star mergers via their gravitational wave emission and their corresponding recessional velocity from their bright electromagnetic emission. Yet, these recessional velocities include peculiar components that stem from local dynamics rather than the expansion of the universe. When this peculiar component is not well-constrained, its uncertainty can dominate the standard siren uncertainty. In this context, we propose a procedure for dedicated, post-factum measurement of merger peculiar velocities via the Dark Energy Spectroscopic Instrument (DESI). We then demonstrate this procedure with a number of galaxies in the vicinity of NGC 4993, the host of the only observed bright standard siren event, as a test case. Implementing this procedure on future standard siren events will serve a significant role in making the standard siren measurement of the Hubble constant more competitive.
