2019/05/10 by David Wittman, Matthew W. Self, Wittman, David +1
Physics and Astronomy · #Adaptive optics and wavefront sensing #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Instrumentation and Methods for Astrophysics (astro-ph.IM) #Pulsars and Gravitational Waves Research
paper · pdf · doi:10.48550/arxiv.1905.04404
openalex publication_date 2019/05/10 · openalex created_date 2022/07/29 · openalex updated_date 2026/07/28
Weak gravitational lensing measurements based on photometry are limited by\nshape noise, the variance in the unknown unlensed orientations of the source\ngalaxies. If the source is a disk galaxy with a well-ordered velocity field,\nhowever, velocity field data can support simultaneous inference of the shear,\ninclination, and position angle, virtually eliminating shape noise. We use the\nFisher Information Matrix formalism to forecast the precision of this method in\nthe idealized case of a perfectly ordered velocity field defined on an\ninfinitesimally thin disk. For nearly face-on targets one shear component,\n\γ_\×, can be constrained to 0.003\(90)/(I0) frac25n rm\npix where I0 is the S/N of the central intensity pixel and n rm pix\nis the number of pixels across a diameter enclosing 80 % of the light. This\nprecision degrades with inclination angle, by a factor of three by\ni=50^\∘. Uncertainty on the other shear component, \γ+, is about\n1.5 (7) times larger than the \γ_\× uncertainty for targets at\ni=10^\∘ (50^\∘). For arbitrary galaxy position angle on the sky,\nthese forecasts apply not to \γ+ and \γ_\× as defined on the\nsky, but to two eigenvectors in (\γ+, \γ_\×,\μ) space where\n\μ is the magnification. We also forecast the potential of less expensive\npartial observations of the velocity field such as slit spectroscopy. We\nconclude by outlining some ways in which real galaxies depart from our\nidealized model and thus create random or systematic uncertainties not captured\nhere. In particular, our forecast \γ_\× precision is currently\nlimited only by the data quality rather than scatter in galaxy properties\nbecause the relevant type of scatter has yet to be measured.\n