Image decomposition of barred galaxies and AGN hosts

By D. Gadotti. 2007

154 citations recorded by the source corpus.

I present the results of multicomponent decomposition of V and R broad-band images of a sample of 17 nearby galaxies, most of them hosting bars and active galactic nuclei (AGN). I use BUDDA v2.1 to produce the fits, allowing the inclusion of bars and AGN in the models. A comparison with previous results from the literature shows a fairly good agreement. It is found that the axial ratio of bars, as measured from ellipse fits, can be severely underestimated if the galaxy axisymmetric component is relatively luminous. Thus, reliable bar axial ratios can only be determined by taking into account the contributions of bulge and disc to the light distribution in the galaxy image. Through a number of tests, I show that neglecting bars when modelling barred galaxies can result in an overestimation of the bulge-to-total luminosity ratio of a factor of 2. Similar effects result when bright, type 1 AGN are not considered in the models. By artificially redshifting the images, I show that the structural parameters of more distant galaxies can in general be reliably retrieved through image fitting, at least up to the point where the physical spatial resolution is ≈1.5 kpc. This corresponds, for instance, to images of galaxies at z = 0.05 with a seeing full width at half-maximum (FWHM) of 1.5 arcsec, typical of the Sloan Digital Sky Survey (SDSS). In addition, such a resolution is also similar to what can be achieved with the Hubble Space Telescope (HST), and ground-based telescopes with adaptive optics, at z ∼ 1‐2. Thus, these results also concern deeper studies such as COSMOS and SINS. This exercise shows that disc parameters are particularly robust, but bulge parameters are prone to errors if its effective radius is small compared to the seeing radius, and might suffer from systematic effects. For instance, the bulge-to-total luminosity ratio is systematically overestimated, on average, by 0.05 (i.e. 5 per cent of the galaxy total luminosity). In this low-resolution regime, the effects of ignoring bars are still present, but AGN light is smeared out. I briefly discuss the consequences of these results to studies of the structural properties of galaxies, in particular on the stellar mass budget in the local Universe. With reasonable assumptions, it is possible to show that the stellar content in bars can be similar to that in classical bulges and elliptical galaxies. Finally, I revisit the cases of NGC 4608 and 5701 and show that the lack of stars in the disc region inside the bar radius is significant. Accordingly, the best-fitting model for the former uses a Freeman type II disc.

Subfields: Astronomy and Astrophysics, Instrumentation, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/d55a6dd142cf49ed74094f8b1072a0eaaa7bfffe

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Citations in the corpus

Inclination- and dust-corrected galaxy parameters: bulge-to-disc ratios and size–luminosity relations (2008, result): “Laurikainen et al. (2005) also obtained a similar result from their K-band data, reporting a mean value of 0.24 (±0.11) from a sample of 14 S0 galaxies while the data in Gadotti (2008) yields an R-band value of 0.28 from their 7 lenticular galaxies.”
Photometric scaling relations of lenticular and spiral galaxies (2010, methodology): “…et al. (2005a) and Laurikainen et al. (2009), the scaling relations for the disk galaxies have not yet been studied using a 2D multi-component approach, which is important in accounting for structure, particularly in barred disk galaxies (Peng 2002; Laurikainen et al. 2004, 2006; Gadotti 2008).”
The black hole mass–stellar velocity dispersion correlation: bulges versus pseudo-bulges (2008, background): “NGC 3227 has a asymmetric molecular nuclear ring with a diameter of ∼ 3′′ (Schinnerer, Eckart, & Tacconi 2000), the Sérsic index (n = 1.1) of the bulge is also disk-like (Gadotti 2008).”
Physical properties and environments of nearby galaxies (2009, background): “Bars are elongated stellar structures located in the central regions of disk galaxies (Kormendy & Kennicutt 2004; Gadotti 2008a).”
Effects of supernova feedback on the formation of galaxy discs (2008, background): “…low with respect to observational estimates for Milky-Way type galaxies, particularly in view of the fact that we neglect the effects of dust (e.g. Gadotti 2008). c© 0000 RAS, MNRAS 000, 000–000 how SN feedback affects the distributions of specific angular momentum, stellar age and chemical…”
DETAILED DECOMPOSITION OF GALAXY IMAGES. II. BEYOND AXISYMMETRIC MODELS (2009, background): “D) images (e.g., Shaw & Gilmore 1989; McLeod & Rieke 1994; Byun & Freeman 1995; de Jong 1996; Moriondo et al. 1998; Simard 1998; Ratnatunga et al. 1999; Wadadekar et al. 1999; Simard et al. 2002; de Souza et al. 2004; Gadotti 2008).”
BULGES OF NEARBY GALAXIES WITH SPITZER: SCALING RELATIONS IN PSEUDOBULGES AND CLASSICAL BULGES (2010, background): “Indeed, Balcells et al. (2003) and Gadotti (2008) show that high spatial resolution is necessary to accurately determine fit parameters when using the Sérsic function.”
Structural properties of pseudo-bulges, classical bulges and elliptical galaxies: a Sloan Digital Sky Survey perspective (2008, methodology): “Gadotti (2008) showed that the structural properties of bulges can be reliably retrieved provided that re is larger than ∼80 per cent of the PSF HWHM.”
AINUR: Atlas of Images of NUclear Rings (2009, background): “Gadotti (2008) prefers to fit a Sérsic profile to the bar with a truncation radius that corresponds to the bar length.”
THE SINFONI BLACK HOLE SURVEY: THE BLACK HOLE FUNDAMENTAL PLANE REVISITED AND THE PATHS OF (CO)EVOLUTION OF SUPERMASSIVE BLACK HOLES AND BULGES (2016, methodology): “Bulge-disk decompositions, when necessary, are taken from Fisher & Drory (2008), Gadotti (2008), Sani et al. (2011), Beifiori et al. (2012), Vika et al. (2012) or are performed by us (in 16 cases), using the program of Erwin (2015) or the procedures of Fisher & Drory (2008).”
A catalogue of 2D photometric decompositions in the SDSS-DR7 spectroscopic main galaxy sample: preferred models and systematics (2014, methodology): “Gadotti (2008) examined the effects of low resolution on galaxy parameters by performing detailed fitting of 17 nearby (z ∼ 0.005) nearly face-on (b/a > 0.9) SDSS disc galaxies.”