Abstract
We derive the low-redshift galaxy stellar mass function (GSMF), inclusive of dust corrections, for the equatorial Galaxy And Mass Assembly (GAMA) data set covering 180 deg2. We construct the ...mass function using a density-corrected maximum volume method, using masses corrected for the impact of optically thick and thin dust. We explore the galactic bivariate brightness plane (M
⋆–μ), demonstrating that surface brightness effects do not systematically bias our mass function measurement above 107.5 M⊙. The galaxy distribution in the M–μ plane appears well bounded, indicating that no substantial population of massive but diffuse or highly compact galaxies are systematically missed due to the GAMA selection criteria. The GSMF is fitted with a double Schechter function, with
$\mathcal {M}^\star =10^{10.78\pm 0.01\pm 0.20}\,\mathrm{M}_{\odot }$
,
$\phi ^\star _1=(2.93\pm 0.40)\times 10^{-3}\,h_{70}^3$
Mpc−3, α1 = −0.62 ± 0.03 ± 0.15,
$\phi ^\star _2=(0.63\pm 0.10)\times 10^{-3}\,h_{70}^3$
Mpc−3 and α2 = −1.50 ± 0.01 ± 0.15. We find the equivalent faint end slope as previously estimated using the GAMA-I sample, although we find a higher value of
$\mathcal {M}^\star$
. Using the full GAMA-II sample, we are able to fit the mass function to masses as low as 107.5 M⊙, and assess limits to 106.5 M⊙. Combining GAMA-II with data from G10-COSMOS, we are able to comment qualitatively on the shape of the GSMF down to masses as low as 106 M⊙. Beyond the well-known upturn seen in the GSMF at 109.5, the distribution appears to maintain a single power-law slope from 109 to 106.5. We calculate the stellar mass density parameter given our best-estimate GSMF, finding
$\Omega _\star = 1.66^{+0.24}_{-0.23}\pm 0.97 \,h^{-1}_{70} \times 10^{-3}$
, inclusive of random and systematic uncertainties.
Abstract
We explore constraints on the joint photometric and morphological evolution of typical low redshift galaxies as they move from the blue cloud through the green valley and on to the red ...sequence. We select Galaxy And Mass Assembly (GAMA) survey galaxies with 10.25 < log(M*/M⊙) < 10.75 and z < 0.2 classified according to their intrinsic u* − r* colour. From single component Sérsic fits, we find that the stellar mass-sensitive K-band profiles of red and green galaxy populations are very similar while g-band profiles indicate more disc-like morphologies for the green galaxies: apparent (optical) morphological differences arise primarily from radial mass-to-light ratio variations. Two-component fits show that most green galaxies have significant bulge and disc components and that the blue to red evolution is driven by colour change in the disc. Together, these strongly suggest that galaxies evolve from blue to red through secular disc fading and that a strong bulge is present prior to any decline in star formation. The relative abundance of the green population implies a typical time-scale for traversing the green valley ∼1–2 Gyr and is independent of environment, unlike that of the red and blue populations. While environment likely plays a rôle in triggering the passage across the green valley, it appears to have little effect on time taken. These results are consistent with a green valley population dominated by (early type) disc galaxies that are insufficiently supplied with gas to maintain previous levels of disc star formation, eventually attaining passive colours. No single event is needed to quench their star formation.
We derive deep I-band luminosity functions and colour-magnitude diagrams from Hubble Space Telescope imaging for eleven 0.2 < z < 0.6 clusters observed at various stages of merging, and a comparison ...sample of five more relaxed clusters at similar redshifts. The characteristic magnitude M* evolves passively out to z = 0.6, while the faint-end slope of the luminosity function is α ∼ −1 at all redshifts. Cluster galaxies must have been completely assembled down to M
I
∼ −18 out to z = 0.6. We observe tight colour-magnitude relations over a luminosity range of up to 8 mag., consistent with the passive evolution of ancient stellar populations. This is found in all clusters, irrespective of their dynamical status (involved in a collision or not, or even within subclusters for the same object), and suggests that environment does not have a strong influence on galaxy properties. A red sequence luminosity function can be followed to the limits of our photometry: we see no evidence of a weakening of the red sequence to z = 0.6. The blue galaxy fraction rises with redshift, especially at fainter absolute magnitudes. We observe bright blue galaxies in clusters at z > 0.4 that are not encountered locally. Surface brightness selection effects preferentially influence the detectability of faint red galaxies, accounting for claims of evolution at the faint end.
ABSTRACT
We present the dust mass function (DMF) of 15 750 galaxies with redshift $z$ < 0.1, drawn from the overlapping area of the GAMA and H-ATLAS surveys. The DMF is derived using the density ...corrected Vmax method, where we estimate Vmax using: (i) the normal photometric selection limit (pVmax) and (ii) a bivariate brightness distribution (BBD) technique, which accounts for two selection effects. We fit the data with a Schechter function, and find $M^{*}=(4.65 \pm 0.18)\times 10^{7}\,h^2_{70}\, \mathrm{ M}_{\odot }$, α = (−1.22 ± 0.01), $\phi ^{*}=(6.26 \pm 0.28)\times 10^{-3}\,h^3_{70}\,\rm Mpc^{-3}\,dex^{-1}$. The resulting dust mass density parameter integrated down to 104 M⊙ is Ωd = (1.11 ± 0.02) × 10−6 which implies the mass fraction of baryons in dust is $f_{m_\mathrm{ b}}=(2.40\pm 0.04)\times 10^{-5}$; cosmic variance adds an extra 7–17 per cent uncertainty to the quoted statistical errors. Our measurements have fewer galaxies with high dust mass than predicted by semi-analytic models. This is because the models include too much dust in high stellar mass galaxies. Conversely, our measurements find more galaxies with high dust mass than predicted by hydrodynamical cosmological simulations. This is likely to be from the long time-scales for grain growth assumed in the models. We calculate DMFs split by galaxy type and find dust mass densities of Ωd = (0.88 ± 0.03) × 10−6 and Ωd = (0.060 ± 0.005) × 10−6 for late types and early types, respectively. Comparing to the equivalent galaxy stellar mass functions (GSMF) we find that the DMF for late types is well matched by the GSMF scaled by (8.07 ± 0.35) × 10−4.
We present a meta-analysis of star formation rate (SFR) indicators in the Galaxy And Mass Assembly (GAMA) survey, producing 12 different SFR metrics and determining the SFR-M... relation for each. We ...compare and contrast published methods to extract the SFR from each indicator, using a well-defined local sample of morphologically selected spiral galaxies, which excludes sources which potentially have large recent changes to their SFR. The different methods are found to yield SFR-M... relations with inconsistent slopes and normalizations, suggesting differences between calibration methods. The recovered SFR-M... relations also have a large range in scatter which, as SFRs of the targets may be considered constant over the different time-scales, suggests differences in the accuracy by which methods correct for attenuation in individual targets. We then recalibrate all SFR indicators to provide new, robust and consistent luminosity-to-SFR calibrations, finding that the most consistent slopes and normalizations of the SFR-M... relations are obtained when recalibrated using the radiation transfer method of Popescu et al. These new calibrations can be used to directly compare SFRs across different observations, epochs and galaxy populations. We then apply our calibrations to the GAMA II equatorial data set and explore the evolution of star formation in the local Universe. We determine the evolution of the normalization to the SFR-M... relation from 0 < z < 0.35 -- finding consistent trends with previous estimates at 0.3 < z < 1.2. We then provide the definitive z < 0.35 cosmic star formation history, SFR-M... relation and its evolution over the last 3 billion years. (ProQuest: ... denotes formulae/symbols omitted.)
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