BUDDI (Bulge-Disc Decomposition of IFU data cubes) is a new approach to fit the two-dimensional light profiles of galaxies as a function of wavelength to extract the spectral properties of these galaxies’ discs and bulges. Our approach is to model the 2-dimensional light profile of the galaxy in every image slice of the datacube, creating a wavelength dependent model of each component included in the fit from which their spectra can be extracted:
The fit is carried out using GALFITM, a modified form of GALFIT which can fit multiwaveband images simultaneously, and can be used to model any components within the galaxy that can be modelled by GALFIT. The benefit of this technique over traditional multiwaveband fits is that the structural parameters are derived using information from the entire data set as opposed to each individual image, thus boosting the signal-to-noise ratio (SNR) and allowing a reliable fit to images with lower SNR. By extending this idea to IFU datacubes we can derive clean spectra and stellar populations for each component included in the fit with minimal contamination from other structures present in the field of view.
The decomposition has been developed using commissioning data from the Sloan Digital Sky Survey-IV Mapping Nearby Galaxies at APO (MaNGA) survey, but can be applied to any IFU data of a nearby galaxy with similar or better spatial resolution and coverage. For example, it has been used to extract the spectra of an extended stellar halo around the cD galaxy NGC3311, the nuclear star clusters at the cores of dwarf galaxies in Fornax, and the bulges, discs and lenses within S0s using MUSE data.
We are now using BUDDI to study the properties of the bulges and discs in a larger sample of galaxies from the MaNGA Survey in a project called BUDDI-MaNGA. We are currently working on the analysis of the galaxies included in the SDSS DR15 (~5000 galaxies), and will soon start the fits to the full sample of MaNGA galaxies from SDSS DR17.
