“Worst-Case” Micro-Lensing in the Identification and Modeling of Lensed Quasars. (arXiv:2105.08690v2 [astro-ph.GA] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Weisenbach_L/0/1/0/all/0/1">Luke Weisenbach</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schechter_P/0/1/0/all/0/1">Paul Schechter</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pontula_S/0/1/0/all/0/1">Sahil Pontula</a>
Although micro-lensing of macro-lensed quasars and supernovae provides unique
opportunities for several kinds of investigations, it can add unwanted and
sometimes substantial noise. While micro-lensing flux anomalies may be safely
ignored for some observations, they severely limit others. “Worst-case”
estimates can inform the decision whether or not to undertake an extensive
examination of micro-lensing scenarios. Here, we report “worst-case”
micro-lensing uncertainties for point sources lensed by singular isothermal
potentials, parameterized by a convergence equal to the shear and by the
stellar fraction. The results can be straightforwardly applied to
non-isothermal potentials utilizing the mass sheet degeneracy. We use
micro-lensing maps to compute fluctuations in image micro-magnifications and
estimate the stellar fraction at which the fluctuations are greatest for a
given convergence. We find that the worst-case fluctuations happen at a stellar
fraction $kappa_star=frac{1}{|mu_{macro}|}$. For macro-minima, fluctuations
in both magnification and demagnification appear to be bounded ($1.5>Delta
m>-1.3$, where $Delta m$ is magnitude relative to the average
macro-magnification). Magnifications for macro-saddles are bounded as well
($Delta m > -1.7$). In contrast, demagnifications for macro-saddles appear to
have unbounded fluctuations as $1/mu_{macro}rightarrow0$ and
$kappa_starrightarrow0$.
Although micro-lensing of macro-lensed quasars and supernovae provides unique
opportunities for several kinds of investigations, it can add unwanted and
sometimes substantial noise. While micro-lensing flux anomalies may be safely
ignored for some observations, they severely limit others. “Worst-case”
estimates can inform the decision whether or not to undertake an extensive
examination of micro-lensing scenarios. Here, we report “worst-case”
micro-lensing uncertainties for point sources lensed by singular isothermal
potentials, parameterized by a convergence equal to the shear and by the
stellar fraction. The results can be straightforwardly applied to
non-isothermal potentials utilizing the mass sheet degeneracy. We use
micro-lensing maps to compute fluctuations in image micro-magnifications and
estimate the stellar fraction at which the fluctuations are greatest for a
given convergence. We find that the worst-case fluctuations happen at a stellar
fraction $kappa_star=frac{1}{|mu_{macro}|}$. For macro-minima, fluctuations
in both magnification and demagnification appear to be bounded ($1.5>Delta
m>-1.3$, where $Delta m$ is magnitude relative to the average
macro-magnification). Magnifications for macro-saddles are bounded as well
($Delta m > -1.7$). In contrast, demagnifications for macro-saddles appear to
have unbounded fluctuations as $1/mu_{macro}rightarrow0$ and
$kappa_starrightarrow0$.
http://arxiv.org/icons/sfx.gif
