BUDDA: A New Two‐dimensional Bulge/Disk Decomposition Code for Detailed Structural Analysis of Galaxies

Abstract

We present BUDDA (Bulge/ Disk Decomposition Analysis), a new code devoted to perform a two-dimensional bulge/disk decomposition directly from the images of galaxies. The bulge component is fitted with a generalized Sérsic profile, whereas disks have an exponential profile. No other components are included. Bars and other substructures, like lenses, rings, inner bars, and inner disks, are studied with the residual images obtained through the subtraction of bulges and disks from the original images. This means that a detailed structural analysis of galaxies may be performed with a small number of parameters, and substructures may be directly studied with no a priori assumptions. As has been already shown by several studies, two-dimensional fitting is much more reliable than one-dimensional profile fitting. Moreover, our code has been thoroughly tested with artificial data, and we demonstrate it to be an accurate tool for determining structural parameters of galaxies. We also show that our code is useful in various kinds of studies, including galaxies of, e.g., different morphological types, and inclinations, which also may be observed at different spatial resolutions. Thus, the code has a broader range of potential applications than most of the previous codes, which are developed to tackle specific problems. To illustrate its usefulness, we present the results obtained with a sample of 51 mostly early-type galaxies (but covering the whole Hubble sequence). These results show some of the applications in which the code may be used: the determination of parameters for fundamental plane and structural studies, quantitative morphological classification of galaxies, and the identification and study of hidden substructures. We have determined the structural parameters of the galaxies in our sample and found many examples of hidden inner disks in ellipticals, secondary bars, nuclear rings and dust lanes in lenticulars and spirals, and also wrong morphological classification cases. We now make BUDDA generally available to the astronomical community.

A low-luminosity type-1 QSO sample

“…In our recent study (Busch et al 2014), we have probed the M BH −L bulge relation of low-luminosity type-1 quasi-stellar objects (LLQSOs). We performed a careful decomposition of K-band images with the B-code (de Souza et al 2004;Gadotti 2008) and find that the bulges do not follow the published M BH −L bulge relations for inactive galaxies of Marconi & Hunt (2003), Vika et al (2012), , and Kormendy & Ho (2013). A deviation of type-1 active galactic nuclei (AGN) from the SMBH-bulge relations is in agreement with previous studies in the optical (Nelson et al 2004;Kim et al 2008;Bennert et al 2011).…”

MUSE tells the story of NGC 4371: The dawning of secular evolution

“…3 show the radial surface brightness profile derived from the S 4 G image with ellipse fits to the isophotes, using the ellipse task in IRAF. The bottom panels show the result of an image decomposition with BUDDA (de Souza et al 2004;Gadotti 2008). The fit includes models for a photometric bulge, a bar and a type II disc (see e.g.…”

Structural properties of disk galaxies

“…The galaxy light is usually modeled as the sum of the contributions of the different galactic components, i.e., bulge and disk, and eventually lenses, bars, spiral arms, and rings (Prieto et al 2001;Aguerri et al 2005). A number of two-dimensional parametric decomposition techniques have been developed to achieve this aim (e.g., Simard 1998;Khosroshahi et al 2000;Peng et al 2002;de Souza et al 2004;Laurikainen et al 2005;Pignatelli et al 2006;Méndez-Abreu et al 2008). On the other hand, the presence of the galactic disk allows us to accurately constrain the inclination of the bulge based on the assumption that the two components share the same polar axis (i.e., the equatorial plane of the disk coincides with that of the bulge).…”