An Investigation into the Prominence of Spiral Galaxy Bulges

By Alister W. Graham. 2000

190 citations recorded by the source corpus.

From a diameter-limited sample of 86 low-inclination (face-on) spiral galaxies, the bulge-to-disk size and luminosity ratios and other quantitative measurements for the prominence of the bulge are derived. The bulge and disk parameters have been estimated using a seeing-convolved Sérsic r1/n bulge and a seeing-convolved exponential disk that were fitted to the optical (B, R, and I) and near-infrared (K) galaxy light profiles. In general, early-type spiral galaxy bulges have Sérsic values of n > 1, and late-type spiral galaxy bulges have values of n < 1. In the B band, only eight galaxies have a bulge shape parameter n consistent with the exponential value 1, and only five galaxies do in the K band. Use of the exponential bulge model is shown to restrict the range of re/h and B/D values by more than a factor of 2. Application of the r1/n bulge models, unlike exponential bulge models, results in a larger mean re/h ratio for the early-type spiral galaxies than for the late-type spiral galaxies, although this result is shown not to be statistically significant. The mean B/D luminosity ratio is, however, significantly larger (>3 σ) for the early-type spirals than for the late-type spirals. Two new parameters are introduced to measure the prominence of the bulge. The first is the difference between the central surface brightness of the galaxy and the surface brightness level at which the bulge and disk contribute equally. The other test uses the radius at which the contribution from the disk and bulge light are equal, normalized for the effect of intrinsically different galaxy sizes. Both of these parameters reveal that the early-type spiral galaxies "appear" to have significantly (more than 2 σ in all passbands) bigger and brighter bulges than late-type spiral galaxies. This apparent contradiction with the re/h values can be explained with an iceberg-like scenario, in which the bulges in late-type spiral galaxies are relatively submerged in their disk. This can be achieved by varying the relative stellar density while maintaining the same effective bulge-to-disk ratio. The B/D luminosity ratio and the concentration index C31, in agreement with past studies, are positively correlated and decrease as one moves along the spiral Hubble sequence toward later spiral galaxy types, although for galaxies with large extended bulges the concentration index no longer traces the B/D luminosity ratio in a one-to-one fashion. A strong (Spearman's rank-order correlation coefficient, rs = 0.80) and highly significant positive correlation exists between the shape, n, of the bulge light profile and the bulge-to-disk luminosity ratio. The absolute bulge magnitude–log n diagram is used as a diagnostic tool for comparative studies with dwarf elliptical and ordinary elliptical galaxies. At least in the B band these objects occupy distinctly different regions of this parameter space. While the dwarf elliptical galaxies appear to be the faint extension to the brighter elliptical galaxies, the bulges of spiral galaxies do not; for a given luminosity they have a noticeably smaller shape parameter and hence a more dramatic decline of stellar density at large radii.

Subfields: Astronomy and Astrophysics, Instrumentation

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Citations in the corpus

Surface brightness profile of the Milky Way’s nuclear star cluster (2014, unknown): “(3) For the Sérsic profile we adopted bn = 1.9992 ∗ n − 0.3271 (Graham 2001) and used I(x, y) = Ie exp −bn ( pRe )1/n − 1 .”
The Secular Evolution of Disk Structural Parameters (2005, methodology): “As our systems often exhibited transient type II phases, we also used the decompositions of Graham (2001, 2003).”
Evidence for a New Elliptical-Galaxy Paradigm: Sérsic and Core Galaxies (2004, background): “…1994; Young & Currie 1994; Durrell 1997; Binggeli & Jerjen 1998; Graham & Guzmán 2003) and for the bulges of disk galaxies (Andredakis, Peletier, & Balcells 1995; Seigar & James 1998; Khosroshahi, Wadadekar, & Kembhavi 2000; Graham 2001; Balcells et al. 2003; MacArthur, Courteau, & Holtzman 2003).”
A New Empirical Model for the Structural Analysis of Early-Type Galaxies, and A Critical Review of the Nuker Model (2003, background): “The quantity bn is a function of the shape parameter n and is defined so that re is the radius enclosing half of the light of the galaxy model; it can be approximated by bn 1.9992n 0.3271, for 1 d n d 10 (see, e.g., Caon et al. 1993; Graham 2001).”
THE DISKMASS SURVEY. I. OVERVIEW (2010, methodology): “…NASA/IPAC Extragalactic Database (NED), corrected to total magnitudes as described in Appendix A, corrected for Galactic extinction (but not internal extinction), and then transformed to disk colors based on bulge-to-disk ratios in the B and K bands measured as a function of type by Graham (2001).”
The formation of disc galaxies in high-resolution moving-mesh cosmological simulations (2013, background): “5, are: Möllenhoff (2004); MacArthur et al. (2003); Graham (2001, 2002). c© 2013 RAS, MNRAS 000, 1–27 lenghts and at lower luminosities with respect to the bestfitting relation, although well within the observed scatter of the data.”
THE STRUCTURE OF CLASSICAL BULGES AND PSEUDOBULGES: THE LINK BETWEEN PSEUDOBULGES AND SÉRSIC INDEX (2008, background): “Expanding a sample to later types might reveal a weak correlation (Graham 2001).”
The Evolution of Disk Galaxies in the GOODS-South Field: Number Densities and Size Distribution (2004, background): “The simulated galaxies have bulge-todisk (B/D) ratios covering the range−0.6 log(B/D) −1.8 typical of Hubble types Sa to Sdm (Graham 2001), disk magnitudes 18≤ z850 ≤ 24, disk half-light radii 0′′.1 ≤ re ≤3′′.0, and various ellipticities and position angles.”
Physical properties and environments of nearby galaxies (2009, background): “At minimum they must include a general Sérsic profile bulge (they are only rarely exactly de Vaucouleurs profiles; Graham 2001; de Jong et al. 2004; Laurikainen et al. 2007).”
Fundamental Planes and the Barless MBH-σ Relation for Supermassive Black Holes (2008, background): “Because most bulges have a Sérsic (1963) R1/n light profile (Graham & Driver 2005) with n < 4 (e.g., Graham 2001; Balcells et al. 2003; MacArthur et al. 2003), it is well known that such an approach overestimates the flux (e.g., Brown et al. 2003).”
BULGE n AND B/T IN HIGH-MASS GALAXIES: CONSTRAINTS ON THE ORIGIN OF BULGES IN HIERARCHICAL MODELS (2008, background): “Graham (2001) and Trujillo et al. (2002) find bulge indices are widely variable within a Hubble type, but they are in general > 1 for early types and < 1 for late types.”
Structure and Kinematics of Early-Type Galaxies from Integral Field Spectroscopy (2016, background): “In this picture one would expect spiral galaxies, which on average have smaller bulge fractions than S0s (e.g. Simien & de Vaucouleurs 1986; de Jong 1996; Graham 2001; Graham & Worley 2008), to overlap with the fast rotators ETGs with the largest λRe values.”
Structure of Disk-dominated Galaxies. I. Bulge/Disk Parameters, Simulations, and Secular Evolution (2002, methodology): “A broader analysis suggests a range of bulge shapes from early- to late-type spirals (Andredakis, Peletier, & Balcells 1995; de Jong 1996c; Courteau et al. 1996; Graham 2001).”
Photometric scaling relations of lenticular and spiral galaxies (2010, background): “6a), which confirms the previous result for spirals (Graham 2001b; Möllenhoff & Heidt 2001; Noordermeer & van der Hulst 2007).”
Dissipation and Extra Light in Galactic Nuclei. I. Gas-Rich Merger Remnants (2008, result): “This appears contrary to the conclusions of Prugniel & Simien (1997), Graham (2001), and Ferrarese et al. (2006); however, we emphasize that we are fitting only gas-rich major merger remnants.”
A Universal Density Profile for Dark and Luminous Matter? (2005, unknown): “In a recent series of papers, A. Graham and co-workers have shown that the Sérsic law provides a remarkably good fit to the luminosity profiles of stellar spheroids, from dE galaxies to the most luminous ellipticals (Graham 2001, 2002; Graham & Guzman 2003; Graham et al. 2003; Trujillo et al. 2004).”
Effects of feedback on the morphology of galaxy discs (2005, unknown): “TheB-band disc-to-total luminosity ratio of the shock-burst galaxy isD/T = 0.84, which is sufficiently large to be identified conventionally as a disc galaxy, while the relation between theD/Ts and the Hubble T-types has a large scatter (Baugh, Cole, & Frenk 1996; Graham 2001).”