What is IFU spectroscopy?

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IFU spectroscopy is an observing technique that provides spectral information over a 2D field of view using instruments known as IFUs (Integral Field Units). This technique is distinct from previous spectroscopic surveys in SDSS which obtained spectra at only a single point, or longslit spectroscopy which provides some spatial information but only along a single slice through an object. Although IFU spectroscopy provides spatially resolved information, it is distinct from traditional broadband imaging which blends the light over a wide range of wavelengths (although you can actually think of broadband imaging as integral field spectroscopy with very poor spectral resolution).

IFUs come in many forms. MaNGA’s IFUs are collections of fibers known as “bundles”, where each individual fiber yields a spectrum at a different position (for more information about MaNGA instrumentation, see the instrument page). Since there are gaps between the bundles, MaNGA takes data at slightly different positions to fill in all the spaces, a process known as “dithering”. The data files created from MaNGA observations provide the flux of an object as a function of position (Ra/Dec) and wavelength. From this data, we can make spatially resolved maps of important spectral features which tell us about galaxy properties such as velocity, age, elemental abundances, and star formation.

A MaNGA target galaxy, 500 Myr away.  The circles represent individual fibers in a bundle

A MaNGA target galaxy, 500 Myr away. The circles represent individual fibers in a bundle

For a more detailed description of IFU spectroscopy and different types of IFUs, check out this website