THE STRUCTURE OF CLASSICAL BULGES AND PSEUDOBULGES: THE LINK BETWEEN PSEUDOBULGES AND SÉRSIC INDEX

By D. Fisher, N. Drory. 2008

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In this paper, we study the properties of pseudobulges (bulges that appear similar to disk galaxies) and classical bulges (bulges which appear similar to E-type galaxies) in bulge-disk decompositions. We show that the distribution of bulge Sérsic indices, nb, is bimodal, and this bimodality correlates with the morphology of the bulge. Pseudobulges have nb ≲ 2 and classical bulges have nb ≳ 2 with little to no overlap. Also, pseudobulges do not follow the correlations of Sérsic index with structural parameters or the photometric projections of the fundamental plane in the same way that classical bulges and elliptical galaxies do. We find that pseudobulges are systematically flatter than classical bulges and thus more disk-like in both their morphology and shape. We do not find significant differences between different bulge morphologies which we are collectively calling pseudobulges (nuclear spirals, nuclear rings, nuclear bars, and nuclear patchiness); they appear to behave similarly in all parameter correlations. In the Sérsic index, flattening, and bulge-to-total ratio, the distinction appears to be between classical bulges and pseudobulges, not between different pseudobulge morphologies. The Sérsic index of the pseudobulges does not correlate with B/T, in contrast to classical bulges. Also, the half-light radius of the pseudobulge correlates with the scale length of the disk; this is not the case for classical bulges. The correlation of Sérsic index and scale lengths with bulge morphology suggests that secular evolution is creating pseudobulges with low-Sérsic index and that other processes (e.g., major mergers) are responsible for the higher Sérsic index in classical bulges and elliptical galaxies.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/de5ef7b6ff28b14e4870030ed850fb3ddd464537

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Citations in the corpus

THE DEPENDENCE OF QUENCHING UPON THE INNER STRUCTURE OF GALAXIES AT 0.5 ⩽ z < 0.8 IN THE DEEP2/AEGIS SURVEY (2012, unknown): “34 Naab & Trujillo (2006) conducted a collisionless simulation that does works produce spheroids with Sérsic indices in the range of our red sequence spheroids and of other observations (e.g., Kormendy & Kennicutt 2004; Drory & Fisher 2007; Fisher & Drory 2008).”
Physical properties and environments of nearby galaxies (2009, background): “More generally, as §3.3 discusses, there are at least three classes of central galaxy components — classical bulges (usually n > 2), pseudobulges (usually n < 2; Fisher & Drory 2008), and bars (usually n ∼ 0.5–1; Gadotti 2009).”
BULGES OF NEARBY GALAXIES WITH SPITZER: SCALING RELATIONS IN PSEUDOBULGES AND CLASSICAL BULGES (2010, methodology): “Fisher & Drory (2008) also find that the Sérsic index of pseudobulges does not correlate with bulge luminosity, halflight radius, or bulge-to-total ratio as it does for classical bulges and elliptical galaxies.”
The Spitzer/IRAC view of black hole–bulge scaling relations (2010, background): “9 in Fisher & Drory 2008 and FD10).”
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).”
BULGE n AND B/T IN HIGH-MASS GALAXIES: CONSTRAINTS ON THE ORIGIN OF BULGES IN HIERARCHICAL MODELS (2008, background): “Pseudobulges tend to have a bulge n < 2.5 (Kormendy & Fisher 2005; Fisher & Drory 2008).”
PRECISE BLACK HOLE MASSES FROM MEGAMASER DISKS: BLACK HOLE–BULGE RELATIONS AT LOW MASS (2010, background): “Fisher & Drory (2008) start with a sample of morphologically selected pseudobulges, meaning that a nuclear bar, spiral, or ring is detected within the bulge region (see also Kormendy & Kennicutt 2004).”
THE MBH–LSPHEROID RELATION AT HIGH AND LOW MASSES, THE QUADRATIC GROWTH OF BLACK HOLES, AND INTERMEDIATE-MASS BLACK HOLE CANDIDATES (2012, methodology): “McAlpine et al. (2011) also studied the Sbc galaxy NGC 4536, reported to have a bulge Sérsic index of 1.88± 0.35 by Fisher & Drory (2008), and an absolute V -band magnitude of -18.4 mag assuming a distance of 25.3 Mpc.”
The population of barred galaxies in the local universe - I. Detection and characterisation of bars (2009, background): “…Courteau et al. 1996; de Jong 1996; Carollo et al. 2001; Prieto et al. 2001; MacArthur et al. 2003; Aguerri et al. 2005; Méndez-Abreu et al. 2008a; Fisher & Drory 2008), a correlation between bulge and disc scale length (MacArthur et al. 2003; Aguerri et al. 2005; Méndez-Abreu et al. 2008a), the…”
A REVISED PARALLEL-SEQUENCE MORPHOLOGICAL CLASSIFICATION OF GALAXIES: STRUCTURE AND FORMATION OF S0 AND SPHEROIDAL GALAXIES (2011, background): “Ellipticals from Bender et al. (1992) and classical bulges from Fisher & Drory (2008) are added to increase the sample size further.”
Structural properties of pseudo-bulges, classical bulges and elliptical galaxies: a Sloan Digital Sky Survey perspective (2008, background): “Note that Fisher & Drory (2008) argue that classical bulges resemble low-luminosity ellipticals.”