The Millennium Galaxy Catalogue: Science highlights (original) (raw)
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Monthly Notices of the Royal Astronomical Society, 2005
We recover the joint and individual space density and surface brightness distribution(s) of galaxies from the Millennium Galaxy Catalogue. The MGC is a local survey spanning 30.9 deg 2 and probing approximately one-two mag arcsec −2 deeper than either the Two-Degree Field Galaxy Redshift Survey (2dFGRS) or the Sloan Digital Sky Survey (SDSS). The MGC contains 10 095 galaxies to B MGC < 20 mag with 96 per cent spectroscopic completeness. For each galaxy we derive individual K-corrections and seeing-corrected sizes. We implement a joint luminosity-surface brightness step-wise maximum likelihood method to recover the bivariate brightness distribution (BBD) inclusive of most selection effects. Integrating the BBD over surface brightness we recover the following Schechter function parameters: φ * = (0.0177 ± 0.0015)h 3 Mpc −3 , M * BMGC − 5 log h = (−19.60 ± 0.04) mag and α = −1.13 ± 0.02. Compared to the 2dFGRS (Norberg et al. 2002) we find a consistent M * value but a slightly flatter faint-end slope and a higher normalisation, resulting in a final luminosity density j bJ = (1.99 ± 0.17) × 10 8 h L ⊙ Mpc −3 -marginally higher than, but consistent with, the earlier 2dFGRS (Norberg et al. 2002), ESP (Zucca et al. 1997), and SDSS z = 0.1 (Blanton et al. 2003a) results. The MGC is inconsistent with the SDSS z = 0 result (+3σ) if one adopts the derived SDSS evolution (Blanton et al. 2003a).
Monthly Notices of the Royal Astronomical Society, 2003
The Millennium Galaxy Catalogue (MGC) is a 37.5 deg 2 , medium-deep, B-band imaging survey along the celestial equator, taken with the Wide Field Camera on the Isaac Newton Telescope. The survey region is contained within the regions of both the Two Degree Field Galaxy Redshift Survey (2dFGRS) and the Sloan Digital Sky Survey Early Data Release (SDSS-EDR). The survey has a uniform isophotal detection limit of 26 mag arcsec −2 and it provides a robust, well-defined catalogue of stars and galaxies in the range 16 ≤ B MGC < 24 mag.
The Astrophysical Journal, 2007
We derive the luminosity functions of elliptical galaxies, galaxy bulges, galaxy pseudo-bulges and galaxy discs from our structural catalogue of 10,095 galaxies. In addition we compute their associated luminosity and stellar mass densities. We show that spheroidal systems (elliptical galaxies and the bulges of disc galaxies) exhibit a strong color bimodality indicating two distinct types of spheroid which are separated by a core color of (u − r) ∼ 2 mag. We argue that the similarity of the red elliptical and the red bulge luminosity functions supports our previous arguments that they share a common origin and surprisingly find that the same follows for the blue ellipticals and blue bulges, the latter of which we refer to as pseudo-bulges. In terms of the stellar mass budget we find that 58 ± 6 per cent is currently in the form of discs, 39 ± 6 per cent in the form of red spheroids (13 ± 4 per cent ellipticals, 26±4 per cent bulges) and the remainder is in the form of blue spheroidal systems (∼ 1.5 per cent blue ellipticals and ∼ 1.5 per cent pseudo-bulges). In terms of galaxy formation we argue that our data on galaxy components strongly supports the notion of a two-stage formation process (spheroid first, disc later) but with the additional complexity of secular evolution occurring in quiescent discs giving rise to two distinct bulge types: genuine 'classical' bulges and pseudo-bulges. We therefore advocate that there are three significant structures underpinning galaxy evolution: classical spheroids (old); pseudobulges (young) and discs (intermediate). The luminous nearby galaxy population is a mixture of these three structural types. The nature of the blue elliptical galaxies remains unclear but one possibility is that these constitute recently collapsed structures supporting the notion of mass-dependent spheroid formation with redshift.
The Millennium Galaxy Catalogue: on the natural subdivision of galaxies
Monthly Notices of the Royal Astronomical Society, 2005
The distribution of global photometric, spectroscopic, structural and morphological parameters for a well defined sample of 350 nearby galaxies has been examined. The usual trends were recovered demonstrating that E/S0 galaxies are redder, more quiescent, more centrally concentrated and possess larger Sérsic indices than later type galaxies.
Monthly Notices of the Royal Astronomical Society, 2007
Based on our sample of 10 095 galaxies with bulge-disc decompositions we derive the empirical B MGC -band internal attenuation-inclination relation for galaxy discs and their associated central bulges. Our results agree well with the independently derived dust models of Tuffs et al., leading to a direct constraint on the mean opacity of spiral discs of τ f B = 3.8 ± 0.7 (central face-on B MGC -band opacity). Depending on inclination, the B MGC -band attenuation correction varies from 0.2 to 1.1 mag for discs and from 0.8 to 2.6 mag for bulges. We find that, overall, 37 per cent of all B MGC -band photons produced in discs in the nearby Universe are absorbed by dust, a figure that rises to 71 per cent for bulge photons. The severity of internal dust extinction is such that one must incorporate internal dust corrections in all optical studies of large galaxy samples. This is particularly pertinent for optical Hubble Space Telescope comparative evolutionary studies as the dust properties will also be evolving. We use the new results to revise our recent estimates of the spheroid and disc luminosity functions. The implied stellar mass densities at redshift zero are somewhat higher than our earlier estimates: ρ discs = (3.8 ± 0.6) → (4.4 ± 0.6) × 10 8 h M Mpc −3 and ρ bulges = (1.6 ± 0.4) → (2.2 ± 0.4) × 10 8 h M Mpc −3 . From our best-fitting dust models we derive a redshift zero cosmic dust density of ρ dust ≈ (5.3 ± 1.7) × 10 5 h M Mpc −3 . This implies that (0.0083 ± 0.0027) h per cent of the baryons in the Universe are in the form of dust and (11.9 ± 1.7) h per cent (Salpeter-'lite' initial mass function) are in the form of stars (∼58 per cent reside in galaxy discs, ∼10 per cent in red elliptical galaxies, ∼29 per cent in classical galaxy bulges and the remainder in low-luminosity blue spheroid systems/components).
Monthly Notices of the Royal Astronomical Society, 2006
Using 10 095 galaxies (B < 20 mag) from the Millennium Galaxy Catalogue, we derive B-band luminosity distributions and selected bivariate brightness distributions for the galaxy population subdivided by: eyeball morphology; Sérsic index (n); 2dFGRS η-parameter; rest-(u − r) colour (global and core); MGC continuum shape; half-light radius; (extrapolated) central surface brightness; and inferred stellar mass-to-light ratio. All subdivisions extract highly correlated sub-sets of the galaxy population which consistently point towards two overlapping distributions: an old, red, inert, predominantly luminous, high central-surface brightness subset; and a young, blue, star-forming, intermediate surface brightness subset. A clear bimodality in the observed distribution is seen in both the rest-(u − r) colour and log(n) distributions. Whilst the former bimodality was well established from SDSS data , we show here that the rest-(u − r) colour bimodality becomes more pronounced when using the core colour as opposed to global colour. The two populations are extremely well separated in the colour-log(n) plane. Using our sample of 3 314 (B < 19 mag) eyeball classified galaxies, we show that the bulge-dominated, early-type galaxies populate one peak and the bulge-less, late-type galaxies occupy the second. The early-and mid-type spirals sprawl across and between the peaks. This constitutes extremely strong evidence that the fundamental way to divide the luminous galaxy population (M BMGC − 5 log h < −16 mag, i.e., dwarfs not included) is into bulges (old red, inert, high concentration) and discs (young, blue, star-forming, low concentration) and that the galaxy bimodality reflects the two component nature of galaxies and not two distinct galaxy classes. We argue that these two-components require two independent formation mechanisms/processes and advocate early bulge formation through initial collapse and ongoing disc formation through splashback, infall and merging/accretion. We calculate the B-band luminosity-densities and stellar-mass densities within each subdivision and estimate that the z ≈ 0 stellar mass content in spheroids, bulges and discs is 35 ± 2 per cent, 18 ± 7 and 47 ± 7 per cent respectively.
Monthly Notices of the Royal Astronomical Society, 2004
The Millennium Galaxy Catalogue (MGC) is a deep (µ B,lim = 26 mag arcsec −2 ), wide field CCD imaging survey, covering 37.5deg 2 . The MGC survey region is completely contained within the Two-degree Field Galaxy Redshift Survey (2dFGRS) and the Sloan Digital Sky Survey Early Data Release (SDSS-EDR). We compare the photometry and completeness of the 2dFGRS and the SDSS-EDR with the MGC over the range 16 < B < 20 mag. We have also undertaken a photometric comparison to SuperCosmos and the SDSS First Data Release.
Galaxy and Mass Assembly (GAMA): ugriz galaxy luminosity functions
2011
Galaxy and Mass Assembly (GAMA) is a project to study galaxy formation and evolution, combining imaging data from ultraviolet to radio with spectroscopic data from the AAOmega spectrograph on the Anglo-Australian Telescope. Using data from phase 1 of GAMA, taken over three observing seasons, and correcting for various minor sources of incompleteness, we calculate galaxy luminosity functions (LFs) and their evolution in the ugriz passbands.
The Millennium Galaxy Catalogue: The nearby supermassive black hole mass function
2005
We highlight the correlation between a galaxy's supermassive black hole mass and the Sersic-index of the host spheroid or bulge component. From our bulge-disk decompositions of 10 095 galaxies, drawn from the Millennium Galaxy Catalogue, we construct the local (z < 0.18) mass function of supermassive black holes. We compare our results to those of McLure & Dunlop (2004) and conclude that the mass density of supermassive black holes may be marginally higher than previously supposed. This increase is predominantly due to the inclusion of low mass and later-type bulges. More details will be presented in a forthcoming paper.