pointlike

Pointlike (often written point-like or pointlike) is an adjective used across physics and astronomy to describe objects that are treated as having negligible spatial extent compared with the measurement resolution. In theory, pointlike approximations replace extended bodies with mathematical points, simplifying models of interactions, scattering, and fields. In observational contexts, "pointlike" describes sources whose apparent size is smaller than the resolving power of the instrument, so their observed profile is governed by the instrument’s point-spread function.

In astronomy, distinguishing pointlike from extended sources helps in source classification and in modeling the background. A pointlike source is typically modeled as a delta-function flux convolved with the instrument’s PSF, while extended sources require spatially varying brightness distributions.

Pointlike is also the name of a software package used to perform fast likelihood fits of point sources in gamma-ray data, notably with the Fermi Large Area Telescope. It implements unbinned and binning likelihood methods, handles multiple candidate sources, and uses instrument response functions and exposure information to estimate source parameters such as flux and spectral shape. The software is used in producing source catalogs and in testing models of gamma-ray emission, contributing to analyses that distinguish point sources from diffuse or extended emission.

Common related concepts include the point-spread function, point source, and maximum likelihood methods.