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Galaxies broadly fall into two categories: star-forming (blue) galaxies and quiescent (red) galaxies. In between, one finds the less populated ``green valley". Some of these galaxies are suspected to be in the process of ceasing their star-formation through a gradual exhaustion of gas supply or already dead and are experiencing a rejuvenation of star-formation through fuel injection. We use the Galaxy And Mass Assembly database and the Galaxy Zoo citizen science morphological estimates to compare the morphology of galaxies in the green valley against those in the red sequence and blue cloud. Our goal is to examine the structural differences within galaxies that fall in the green valley, and what brings them there. Previous results found disc features such as rings and lenses are more prominently represented in the green valley population. We revisit this with a similar sized data set of galaxies with morphology labels provided by the Galaxy Zoo for the GAMA fields based on new KiDS images. Our aim is to compare qualitatively the results from expert classification to that of citizen science. We observe that ring structures are indeed found more commonly in green valley galaxies compared to their red and blue counterparts. We suggest that ring structures are a consequence of disc galaxies in the green valley actively exhibiting characteristics of fading discs and evolving disc morphology of galaxies. We note that the progression from blue to red correlates with loosening spiral arm structure., 11 pages, 21 figures, accepted to MNRAS

We present a complete structural analysis of the ellipticals (E), diffuse bulges (dB), compact bulges (cB), and discs (D) within a redshift range 0 < z < 1, and stellar mass log10(M*/M⊙) ≥ 9.5 volume-limited sample drawn from the combined DEVILS and HST-COSMOS region. We use the profit code to profile over ∼35 000 galaxies for which visual classification into single or double component was pre-defined in Paper-I. Over this redshift range, we see a growth in the total stellar mass density (SMD) of a factor of 1.5. At all epochs we find that the dominant structure, contributing to the total SMD, is the disc, and holds a fairly constant share of $\sim 60{{\ \rm per\ cent}}$ of the total SMD from z = 0.8 to z = 0.2, dropping to $\sim 30{{\ \rm per\ cent}}$ at z = 0.0 (representing $\sim 33{{\ \rm per\ cent}}$ decline in the total disc SMD). Other classes (E, dB, and cB) show steady growth in their numbers and integrated stellar mass densities. By number, the most dramatic change across the full mass range is in the growth of diffuse bulges. In terms of total SMD, the biggest gain is an increase in massive elliptical systems, rising from 20 per cent at z = 0.8 to equal that of discs at z = 0.0 (30 per cent) representing an absolute mass growth of a factor of 2.5. Overall, we see a clear picture of the emergence and growth of all three classes of spheroids over the past 8 Gyr, and infer that in the later half of the Universe’s timeline spheroid-forming processes and pathways (secular evolution, mass-accretion, and mergers) appear to dominate mass transformation over quiescent disc growth.

We present catalogues of stellar masses, star formation rates, and ancillary stellar population parameters for galaxies spanning $02.6$, we see evidence of a bend in the relation at low redshifts ($z, Comment: Accepted for publication in MNRAS. 28 pages, 20 figures

We use data from the GAMA and GALEX surveys to demonstrate that the UV upturn, an unexpected excess of ultraviolet flux from a hot stellar component, seen in the spectra of many early-type galaxies, arises from processes internal to individual galaxies with no measurable influence from the galaxies' larger environment. We first define a clean sample of passive galaxies without a significant contribution to their UV flux from low-level star formation. We confirm that galaxies with the optical colours of red sequence galaxies often have signs of residual star formation, which, without other information, would prevent a convincing demonstration of the presence of UV upturns. However, by including (NUV$-u$) and {\it WISE} (W2-W3) colours, and FUV data where it exists, we can convincingly constrain samples to be composed of non-star-forming objects. Using such a sample, we examine GALEX photometry of low redshift GAMA galaxies in a range of low-density environments, from groups to the general field, searching for UV upturns. We find a wide range of (NUV$-r$) colours, entirely consistent with the range seen -- and attributed to the UV upturn -- in low-redshift red sequence cluster galaxies. The range of colours is independent of group multiplicity or velocity dispersion, with isolated passive galaxies just as likely to have blue UV-to-optical colours, implying significant upturn components, as those in richer groups and in the previous data on clusters. This is supported by equivalent results for (FUV$-r$) colours which are clear indicators of upturn components., Accepted by MNRAS

The extent to which dwarf galaxies represent essentially scaled down versions of giant galaxies is an important question with regards the formation and evolution of the galaxy population as a whole. Here we address the specific question of whether dwarf galaxies behave like smaller versions of giants in terms of their X-ray properties. We discuss two samples of around 100 objects each, dwarfs in the Virgo Cluster and dwarfs in a large northern hemisphere area. We find nine dwarfs in each sample with Chanda detections. For the Virgo sample, these are in dwarf elliptical (or dwarf lenticular) galaxies and we assume that these are (mostly) low mass X-ray binaries (some may be nuclear sources). We find a detection rate entirely consistent with scaling down from massive ellipticals, viz. about 1 bright (i.e. $L_X > 10^{38}$ erg~s$^{-1}$) LMXB per $5 \times 10^9 M_{\odot}$ of stars. For the field sample, we find one (known) Seyfert nucleus, in a galaxy which appears to be the lowest mass dwarf with a confirmed X-ray emitting nucleus. The other detections are in star forming dwarf irregular or blue compact dwarf galaxies and are presumably high mass X-ray binaries. This time, we find a very similar detection rate to that in large late type galaxies if we scale down by star formation rate, roughly 1 HMXB for a rate of $0.3 M_{\odot}$ per year. Nevertheless, there does seem to be one clear difference, in that the dwarf late type galaxies with X-ray sources appear strongly biased to very low metallicity systems.

Steven Phillipps looks at the fate of some RAS Fellows in the Great War.

Recently a number of studies have found a similarity between the passive fraction of central and satellite galaxies when controlled for both stellar and halo mass. These results suggest that the quenching processes that affect galaxies are largely agnostic to central/satellite status, which contradicts the traditional picture of increased satellite quenching via environmental processes such as stripping, strangulation and starvation. Here we explore this further using the Galaxy And Mass Assembly (GAMA) survey which extends to ~2dex lower in stellar mass than SDSS, is more complete for closely-separated galaxies (>95% compared to >70%), and identifies lower-halo-mass groups outside of the very local Universe (M$_{\mathrm{halo}}\sim10^{12}$M$_{\odot}$ at $0.1, Comment: 15 pages, 8 figures, MNRAS accepted

Steven Phillipps looks back at the RAS at its centenary through the pages of Monthly Notices.

Compact stellar systems (CSS) range in mass from globular clusters (GCs), through the more recently discovered ultracompact dwarfs (UCDs), to the rare compact elliptical galaxies. Given their intermediate position, the origin of UCDs, and hence whether they should be counted as galaxies or star clusters, remains unclear. In this paper, we compare the population of X-ray point sources (expected to be low-mass X-ray binaries; LMXBs) in UCD candidates, that is, relatively high-luminosity compact systems, with that known to exist in lower mass GCs. Any difference in LMXB populations may then indicate physical differences between GCs and UCDs. We find that, despite their much larger masses and hence numbers of stars, UCDs and UCD candidates are, if anything, less likely to contain bright X-ray point sources than are GCs. The LMXB content per unit stellar mass is therefore much lower for the UCD candidates, intermediate between that for GCs and for elliptical galaxies. This difference between UCDs and GCs can be explained if UCDs have significantly lower central densities than lower mass GCs, as this will reduce the stellar encounter rate and therefore the production of suitable binary systems. This supports the previously proposed idea of structural differences between UCDs and GCs, though not necessarily ruling out a close relationship between these two types of CSS.

Analysing all Galaxy and Mass Assembly (GAMA) galaxies within a factor two (+/- 0.3 dex) of the stellar mass of the Milky Way (MW), there is a 11.9% chance that one of these galaxies will have a close companion (within a projected separation of 70 kpc and radial separation of 400 km/s) that is at least as massive as the Large Magellanic Cloud (LMC). Two close companions at least as massive as the Small Magellanic Cloud (SMC) are rare at the 3.4% level. Two full analogues to the MW- LMC-SMC system were found in GAMA (all galaxies late-type and star forming), suggesting such a combination of close together, late-type, star-forming galaxies is rare: only 0.4% of MW mass galaxies (in the range where we could observe both the LMC and SMC) have such a system. In summary, the MW-LMC-SMC system is a 2.7? event (when recast into Gaussian statistics). Using cross-correlation comparisons we find that there is a preference for SMC- LMC binary pair analogues to be located within 2 Mpc of a range of different lumi- nosity groups. There is a particular preference is for such binaries to be located near LG luminosity systems. When these groups are subdivided into small magnitude gap and large magnitude gap subsets, the binaries prefer to be spatially associated with the small magnitude gap systems. These systems will be dynamically less evolved, but still offer the same amount of gravitational dark matter. This suggests that binaries such as the SMC-LMC might be transient systems, usually destroyed during vigorous merger events. Details of a particularly striking analogue to the MW-SMC-LMC and M31 complex are included.

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. At low redshift, z < 0.1, we find that blue galaxies, defined according to a magnitude-dependent but non-evolving colour cut, are reasonably well fit over a range of more than ten magnitudes by simple Schechter functions in all bands. Red galaxies, and the combined blue-plus-red sample, require double power-law Schechter functions to fit a dip in their LF faintward of the characteristic magnitude M* before a steepening faint end. This upturn is at least partly due to dust-reddened disk galaxies. We measure evolution of the galaxy LF over the redshift range 0.002 < z < 0.5 using both a parametric fit and by measuring binned LFs in redshift slices. The characteristic luminosity L* is found to increase with redshift in all bands, with red galaxies showing stronger luminosity evolution than blue galaxies. The comoving number density of blue galaxies increases with redshift, while that of red galaxies decreases, consistent with prevailing movement from blue cloud to red sequence. As well as being more numerous at higher redshift, blue galaxies also dominate the overall luminosity density beyond redshifts z = 0.2. At lower redshifts, the luminosity density is dominated by red galaxies in the riz bands, by blue galaxies in u and g.

We explore the variation in stellar population ages for Coma cluster galaxies as a function of projected cluster-centric distance, using a sample of 362 red-sequence galaxies with high signal-to-noise spectroscopy. The sample spans a wide range in luminosity (0.02-4 L*) and extends from the cluster core to near the virial radius. We find a clear distinction in the observed trends of the giant and dwarf galaxies. The ages of red-sequence giants are primarily determined by galaxy mass, with only weak modulation by environment, in the sense that galaxies at larger cluster-centric distance are slightly younger. For red-sequence dwarfs (with mass

We investigate the ultraviolet and optical properties and environment of low redshift galaxies detected in the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) science demonstration data. We use the Sloan Digital Sky Survey seventh release and the Galaxy And Mass Assembly database to select galaxies with r_Petro < 19.0 mag in the redshift range 0.02 < z < 0.2 and look for their submillimeter counterparts in H-ATLAS. Our results show that at low redshift, H-ATLAS detects mainly blue/star-forming galaxies with a minor contribution from red systems which are highly obscured by dust. In addition we find that the colour of a galaxy rather than the local density of its environment determines whether it is detectable by H-ATLAS. The average dust temperature of galaxies that are simultaneously detected by both PACS and SPIRE is 25K \pm 4K, independent of environment. This analysis provides a glimpse of the potential of the H-ATLAS data to investigate the submillimeter properties of galaxies in the local universe.

We investigate the properties of satellite galaxies that surround isolated hosts within the redshift range 0.01 < z < 0.15, using data taken as part of the Galaxy And Mass Assembly survey. Making use of isolation and satellite criteria that take into account stellar mass estimates, we find 3514 isolated galaxies of which 1426 host a total of 2998 satellites. Separating the red and blue populations of satellites and hosts, using colour-mass diagrams, we investigate the radial distribution of satellite galaxies and determine how the red fraction of satellites varies as a function of satellite mass, host mass and the projected distance from their host. Comparing the red fraction of satellites to a control sample of small neighbours at greater projected radii, we show that the increase in red fraction is primarily a function of host mass. The satellite red fraction is about 0.2 higher than the control sample for hosts with 11.0 < log M_* < 11.5, while the red fractions show no difference for hosts with 10.0 < log M_* < 10.5. For the satellites of more massive hosts the red fraction also increases as a function of decreasing projected distance. Our results suggest that the likely main mechanism for the quenching of star formation in satellites hosted by isolated galaxies is strangulation.

Using the complete GAMA-I survey covering ~142 sq. deg. to r=19.4, of which ~47 sq. deg. is to r=19.8, we create the GAMA-I galaxy group catalogue (G3Cv1), generated using a friends-of-friends (FoF) based grouping algorithm. Our algorithm has been tested extensively on one family of mock GAMA lightcones, constructed from Lambda-CDM N-body simulations populated with semi-analytic galaxies. Recovered group properties are robust to the effects of interlopers and are median unbiased in the most important respects. G3Cv1 contains 14,388 galaxy groups (with multiplicity >= 2$), including 44,186 galaxies out of a possible 110,192 galaxies, implying ~40% of all galaxies are assigned to a group. The similarities of the mock group catalogues and G3Cv1 are multiple: global characteristics are in general well recovered. However, we do find a noticeable deficit in the number of high multiplicity groups in GAMA compared to the mocks. Additionally, despite exceptionally good local spatial completeness, G3Cv1 contains significantly fewer compact groups with 5 or more members, this effect becoming most evident for high multiplicity systems. These two differences are most likely due to limitations in the physics included of the current GAMA lightcone mock. Further studies using a variety of galaxy formation models are required to confirm their exact origin.

We present two newly-discovered compact elliptical (cE) galaxies, exhibiting clear evidence of tidal steams, and found during a search of SDSS DR7 for cE candidates. The structural parameters of the cEs are derived using GALFIT, giving effective radii, Re, of 388 and 263 parsecs, and B-band mean surface brightnesses within Re of 19.4 and 19.2 magnitudes per arcsec squared. We have re-analysed the SDSS spectra, which indicate that they possess young to intermediate-age stellar populations. These two cEs provide direct evidence, a "smoking gun", for the process of tidal stripping that is believed to be the origin of M32-type galaxies. Both are in small groups with a large spiral fraction, suggesting that we may be seeing the formation of such cE galaxies in dynamically young environments. The more compact of the galaxies is found in a small group not unlike the Local Group, and thus provides an additional model for understanding M32.

The Galaxy And Mass Assembly (GAMA) survey has been operating since February 2008 on the 3.9-m Anglo-Australian Telescope using the AAOmega fibre-fed spectrograph facility to acquire spectra with a resolution of R~1300 for 120,862 SDSS selected galaxies. The target catalogue constitutes three contiguous equatorial regions centred at 9h (G09), 12h (G12) and 14.5h (G15) each of 12 x 4 sq.deg to limiting fluxes of r < 19.4, r < 19.8, and r < 19.4 mag respectively (and additional limits at other wavelengths). Spectra and reliable redshifts have been acquired for over 98 per cent of the galaxies within these limits. Here we present the survey footprint, progression, data reduction, redshifting, re-redshifting, an assessment of data quality after 3 years, additional image analysis products (including ugrizYJHK photometry, Sersic profiles and photometric redshifts), observing mask, and construction of our core survey catalogue (GamaCore). From this we create three science ready catalogues: GamaCoreDR1 for public release, which includes data acquired during year 1 of operations within specified magnitude limits (February 2008 to April 2008); GamaCoreMainSurvey containing all data above our survey limits for use by the GAMA team and collaborators; and GamaCoreAtlasSv containing year 1, 2 and 3 data matched to Herschel-ATLAS Science Demonstration data. These catalogues along with the associated spectra, stamps and profiles can be accessed via the GAMA website: http://www.gama-survey.org/, Submitted to MNRAS. MySQL database and data downloads available now from http://www.gama-survey.org/

In this paper we study the stellar populations of 356 bright, $M_{r}$ $\leq$ -19, Coma cluster members located in a 2 degree field centred on the cluster core using SDSS DR7 spectroscopy. For the quiescent galaxies we find strong correlations between absorption line index strength and velocity dispersion ($\sigma$) for CN2, C4668, Mgb and H$\beta$. We find significant cluster-centric radial gradients in H$\beta$, Mgb and C4668 for the passive galaxies. We use state-of-the-art stellar population models \citep{schiavon07} and the measured absorption line indices to infer the single-stellar-population-equivalent (SSP-equivalent) age and [Fe/H] for each galaxy, as well as their abundance patterns in terms of [Mg/Fe], [C/Fe], [N/Fe] and [Ca/Fe]. For the passive galaxy subsample we find strong evidence for "archaeological downsizing", with age $\propto \sigma^{0.90 \pm 0.06}$. We recover significant cluster-centric radial stellar population gradients for the passive sample in SSP-equivalent age, [Mg/Fe], [C/Fe] and [N/Fe]. These trends are in the sense that, at fixed velocity dispersion, passive galaxies on the outskirts of the cluster are 24% $\pm$ 9% younger with lower [Mg/Fe] and [N/Fe] but higher [C/Fe] than those in the cluster core. We find no significant increase in cluster-centric radial stellar population gradients when fitting to a passive galaxy subset selected to cover the cluster core and South-West region, which contains the NGC 4839 subgroup. Thus we conclude that the NGC 4839 in-fall region is not unique, at least in terms of the stellar populations of bright galaxies. We speculate that the more pronounced cluster-centric radial gradients seen by other recent studies may be attributed to the luminosity range spanned by their samples, rather than to limited azimuthal coverage of the cluster.(abridged)

We have obtained spectroscopic redshifts of colour-selected point sources in four wide area VLT-FLAMES fields around the Fornax Cluster giant elliptical galaxy NGC 1399, identifying as cluster members 30 previously unknown faint (-10.5, Comment: 13 pages (including supplementary table), 13 figures, 5 tables. Accepted for publication in MNRAS

We present the Macquarie/AAO/Strasbourg Hα Planetary Nebula Catalogue (MASH) of over 900 true, likely and possible new Galactic planetary nebulae (PNe) discovered from the AAO/UKST Hα survey of the southern Galactic plane. The combination of depth, resolution, uniformity and areal coverage of the Hα survey has opened up a hitherto unexplored region of parameter space permitting the detection of this significant new PN sample. Away from the Galactic bulge the new PNe are typically more evolved, of larger angular extent, of lower surface brightness and more obscured (i.e. extinguished) than those in most previous surveys. We have also doubled the number of PNe in the Galactic bulge itself and although most are compact, we have also found more evolved examples. The MASH catalogue represents the culmination of a seven-year programme of identification and confirmatory spectroscopy. A key strength is that the entire sample has been derived from the same, uniform observational data. The 60 per cent increase in known Galactic PNe represents the largest ever incremental sample of such discoveries and will have a significant impact on many aspects of PN research. This is especially important for studies at the faint end of the PN luminosity function which was previously poorly represented.

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. All subdivisions extract highly correlated sub-sets of the galaxy population which consistently point towards two overlapping distributions. A clear bimodality in the observed distribution is seen in both the rest-(u-r) colour and log(n) distributions. 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 is into bulges and discs 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. [Abridged], Accepted for publication in MNRAS, 23 pages, 17 figures. Comments welcome. MGC website is at: http://www.eso.org/~jliske/mgc/

The proximity effect evident in the spectra of quasars, that is the deficit of Lyman a forest lines at redshifts close to that of the quasar, is attributed to the ionizing radiation of the quasar itself. The physical extent of the deficient (i.e. more ionized) region will clearly depend on the absolute luminosity of the quasar. However, what we observe will be a relationship involving a redshift range (the clearing in the forest) and the apparent quasar luminosity. The translations from redshift interval to physical scale in the radial direction and from apparent to absolute luminosity depend on the chosen cosmological model, and moreover depend on the model (specifically the density parameter and cosmological constant) in different ways. Analysis of the proximity effect therefore provides a potential test of cosmological parameters. In practice, though moderately large, the effects turn out to be difficult to disentangle from other factors, in particular the value of the intergalactic ionizing flux. Reversing this argument, though, means that the effects can be important (at the 40 per cent level of uncertainty) when attempting to deduce the ionizing background flux and its variation with redshift.

We combine magnitude and photometric redshift data on galaxies in the Hubble Deep Fields with morphological classifications in order to separate out the distributions for early type galaxies. The updated morphological galaxy number counts down to I = 25 and the corresponding redshift distributions are used as joint constraints on cosmological models, in particular on the values of the density parameter Omega_{0} and normalised cosmological constant Lambda_{0}. We find that an Einstein - de Sitter universe with simple passive evolution gives an excellent fit to the counts and redshift data at all magnitudes. An open, low Omega_{0}, model with no net evolution (and conservation of the number of ellipticals), which fits the counts equally well, is somewhat less successful, predicting slightly lower mean redshifts and, more significantly, the lack of a high--z tail. A number conserving model with a dominant contribution from Lambda_{0}, on the other hand, is far less successful, predicting a much narrower distribution than seen. More complex models are obviously possible, but we conclude that if large scale transmutation between types does {\it not} occur, then the lambda-dominated models provide a very poor fit to the current data.

With the advent of multi-fibre spectrographs such as the 'Two-Degree Field' (2dF) instrument at the Angle-Australian Telescope, quasar surveys that are free of any preselection of candidates and any biases this implies have become possible for the first time. The first of these is that which is being undertaken as part of the Fornax Spectroscopic Survey, a survey of the area around the Fornax Cluster of galaxies, and aims to obtain the spectra of all objects in the magnitude range 16.5 2.2. Using this complete quasar sample, a new determination of quasar number counts is made, enabling an independent check of existing quasars surveys. Cumulative counts per square degree at a magnitude limit of b(j) 2.2 and 13.7 +/- 3.1 for z > 0.3. Given the likely detection of extra quasars in the Fornax survey, we make a more detailed examination of existing quasar selection techniques. First, looking at the use of a stellar criterion, four of the 71 quasars are 'non-stellar' on the basis of the automated plate measuring facility (APM) b(j) classification, however inspection shows all are consistent with stellar, but misclassified due to image confusion. Examining the ultraviolet excess and multicolour selection techniques, for the selection criteria investigated, ultraviolet excess would find 69 +/- 6 per cent of our 0.3 2.2 quasars, while the completeness level for multicolour selection is found to be 90(-4)(+3) per cent for 0.3 2.2 quasars. The extra quasars detected by our all-object survey thus have unusually red star-like colours, and this appears to be a result of the continuum shape rather than any emission features. An intrinsic dust extinction model may, at least partly, account for the red colours.

ABSTRA C T It is evident that considerable information exists in astronomical data below the threshold for the detection of individual sources (perhaps set for a ‘5s ’ total detection, or for isophotal detection thresholds of ‘2s ’ above the sky background), and that such information, if descriptive of an underlying population of objects characterized by a relatively small parameter set, could in principle be used to set constraints on these parameters. We therefore derive a general theoretical framework for fluctuation analysis (after the radio astronomers’ ‘P(D)’ analysis) of optical imaging data on faint galaxy fields, in particular; on fields containing rich clusters of galaxies, in an attempt to determine the Schechter luminosity function of the dwarf galaxies that dominate the statistics at this magnitude range.

We recover the luminosity distributions over a wide range of absolute magnitude (-24.5 < M_{R} < -16.5) for a sample of seven rich southern galaxy clusters. We find a large variation in the ratio of dwarf to giant galaxies, DGR: 0.8\le $ DGR $\le 3.1. This variation is shown to be inconsistent with a ubiquitous cluster luminosity function. The DGR shows a smaller variation from cluster to cluster in the inner regions (r \ls 0.56 Mpc). Outside these regions we find the DGR to be strongly anti-correlated with the mean local projected galaxy density with the DGR increasing towards lower densities. In addition the DGR in the outer regions shows some correlation with Bautz-Morgan type. Radial analysis of the clusters indicate that the dwarf galaxies are less centrally clustered than the giants and form a significant halo around clusters. We conclude that measurements of the total cluster luminosity distribution based on the inner core alone are likely to be severe underestimates of the dwarf component, the integrated cluster luminosity and the contribution of galaxy masses to the cluster's total mass. Further work is required to quantify this. The observational evidence that the unrelaxed, lower density outer regions of clusters are dwarf-rich, adds credence to the recent evidence and conjecture that the field is a predominantly dwarf rich environment and that the dwarf galaxies are under-represented in measures of the local field luminosity function., 31 pages including 11 figures. Also available from http://star-www.st-and.ac.uk/~spd3/bib.html

We present detailed simulations of long exposure CCD images. The simulations are used to explore the validity of the statistical method for reconstructing the luminosity distribution of galaxies within a rich cluster i.e. by the subtraction of field number-counts from those of a sight-line through the cluster. In particular we use the simulations to establish the reliability of our observational data presented in Paper 3. Based on our intended CCD field-of-view (6.5 by 6.5 arcmins) and a 1-sigma detection limit of 26 mags per sq arcsecond, we conclude that the luminosity distribution can be robustly determined over a wide range of absolute magnitude (-23 < M_{R} < -16) provided: (a) the cluster has an Abell richness 1.5 or greater, (b) the cluster's redshift lies in the range 0.1 < z < 0.3, (c) the seeing is better than FWHM 1.25'' and (d) the photometric zero points are accurate to within Delta m = \pm 0.12. If these conditions are not met then the recovered luminosity distribution is unreliable and potentially grossly miss-leading. Finally although the method clearly has limitations, within these limitations the technique represents an extremely promising probe of galaxy evolution and environmental dependencies., 24 pages, 8 figures accepted for publication in MNRAS also available from http://star-www.st-and.ac.uk/~spd3/bib.html

We determine the companion galaxy luminosity function (LF) for regions around isolated spiral galaxies. If we assume that any excess in the galaxy number counts in the vicinity of a spiral galaxy is due to galaxies at the same distance, then a system LF can be determined from the variation of excess numbers with apparent magnitude. By studying the excess over many field ‘centre’ galaxies, a good statistical accuracy can be obtained for the companion galaxy LF. Since redshift information is not required for the faint galaxies, it is possible to sample further down the LF as compared with redshift surveys. For 23 primary galaxies of known redshift, we find a dwarf satellite Schechter LF with a characteristic magnitude MV*(D)≃−19 and a faint-end slope α=−1.7, down to MV=−14 (H0=50 km s−1 Mpc−1).

We examine the metallicity distribution within and between galaxies and hence determine their present -day mean abundance. Adding in components for intergalactic gas, we arrive at an estimate of the mean metal abundance of the Universe. We find the pleasantly Copernican result that the overall mean abundance is close to solar. We then discuss the evolution with time of this quantity, using simplified, but general, models of galactic chemical evolution. The variation of the total metal content of the Universe with epoch turns out to be constrained within fairly well-defined limits for plausible variations in the global mean star formation rate. However, what would be observed at any given redshift depends critically on which regions of galaxies are being sampled and on the formation histories of these particular regions. Finally, we investigate the joint constraints provided by current observations of the evolution of the metallicity and gas content of the Universe, as measured by QSO damped Lyman IX absorbers. We note a generic inconsistency in global models and introduce a more realistic model, with different evolution for different galaxy types, which can overcome this difficulty. Current chemical evidence does not require that the global average star formation rate in the Universe should have decreased by a large factor since galaxy formation began.

From deep CCD observations of the cluster Abell 2554 we have recovered the cluster's luminosity distribution over a wide range of magnitude (-24 < M(R) < -16). We compare the derived A2554 cluster luminosity function (at redshift 0.1) with that of the local Coma Cluster (A1656) and the more distant (z = 0.2) cluster A963. The distribution is remarkably similar for these three clusters of comparable richness and morphology. All show a flat (��= -1.0) luminosity function for the giant galaxies (-24 < M(R) < -19.5) which exhibits a sharp upturn (��= -1.7) at some intermediate magnitude (M(R) = -19) and continues to rise to the limits of existing data. We suggest that such a luminosity function may be ubiquitous among rich clusters and that a similar form may apply for poorer clusters and possibly the field as well. The three cluster dwarf LFs are seen over a range of lookback times covering a quarter of the age of the universe. Therefore the similarity between the three measured LFs seems to rule out strong evolution of the dwarf populations in rich cluster environments, at least out to z = 0.2, unless richness effects conspire to conceal evolutionary changes., Accepted for publication in Monthly Notices of the Royal Astronomical Society

Despite its utility in exploring possible spatial variations in the stellar populations in galaxies, infrared surface photometry of low-luminosity dwarf elliptical (dE) galaxies is generally lacking, due to the technical difficulties in observing low surface brightness objects against the bright infrared sky. Here we attempt to remedy this shortfall to some extent by presenting K-band photometry at arcsecond resolution, including radial profiles, 1D and 2D model fits and the quantification of nuclear components, for a small sample of dE galaxies, with absolute magnitudes MB?-15 to -13, in the Fornax Cluster. In the second part of the paper, we explore the comparison of these data with corresponding optical observations and attempt to interpret this in terms of stellar population models and their radial trends. A significant range of global opticalinfrared colours is present in our sample, but radial colour gradients in the galaxies are usually small. However, while the nuclear regions tend to be bluer in optical colours, they are systematically redder than the surrounding galaxy in (R-K). The stellar population modelling suggests that these colour differences are probably an effect of both higher metallicity and younger age in the nuclei. Excluding the nuclear regions, the global colour profiles typically change in the same direction, again indicating older, more metal-poor stellar populations in the outskirts of the galaxies.

In this paper, we describe a search for very low-surface-brightness features in deep CCD frames. We show how cross-correlation with templates can be used to detect low-surface-brightness features, which would not be detected using more typical connected-pixel algorithms. The search technique is specifically designed to search for large, low-surface- brightness galaxies like Malin 1. Although we identify 19 potentially interesting, extended, low-surface-brightness objects, we conclude that Malin 1 type objects per se are less prolific than `normal' L^*^ galaxies, and that galaxies with -22 < M_v_ < 19 and μ_0_ ~26 Vmu are at least an order of magnitude less common than their normal-surface- brightness counterparts.

It is difficult to understand why disc galaxies should all form with about the same central surface brightness (central mass density?). A possible explanation is that the data are in fact heavily biased by observational selection. In a number of papers we have shown how this might arise. In this paper we take a new look at van der Kruit's assertion that the observational selection effects are unimportant. We show that his data are incomplete on the low-surface-brightness side and that they are probably constrained by a hidden magnitude constraint that he did not consider. We go on to test the selection hypothesis by analysing a set of observational data for which redshifts are available. The volume occupied by galaxies of different surface brightnesses in this sample are in good agreement with those predicted by observational selection. We conclude that the selection hypothesis has not been disproved and that there is still good reason to expect it to be true.

Most models devised to account for the excess galaxies seen in number magnitude counts invoke a large population of low-luminosity galaxies at moderate redshifts (or look-back times). Here we directly investigate the faint end of the luminosity function at moderate z (~0.2) via deep R-band observations of the distant Abell cluster A963 made with the Hitchhiker parallel CCD camera on the WHT. By subtracting a `mean field' component from the observed galaxy counts in the cluster area, we deduce the existence of a large dwarf population in the cluster, which gives rise to a significant excess over the mean, right down to the sample limit at m_R_~24.5(M_R_~ -16.5). The implied dwarf-galaxy luminosity function has a steep slope, α~ -1.8, in line with recent work on nearby clusters.

We present the first deep observations with the new Hitchhiker parallel CCD camera. In parallel with scheduled observations, we have observed a field near the North Galactic Pole in four wavebands, with an equivalent total exposure time of 5 h, and obtained galaxy number counts to limiting magnitudes of m B =26.4, m V =24.9, m R =26.3 and m I =22.5. The data should be complete to about 0.5 mag above these faint limits. We also present B−V, B−R, B−I, V−R and R−I colour histograms for the faint galaxies as a function of B, V or R magnitude. The observations are in good agreement with previous deep CCD data, showing a steep number-count slope in the blue, which gradually decreases for longer wavelength observations, and a gradual blueing (in terms of B−R) of the mean galaxy population at fainter magnitudes

Recent tests at the UKST with large-format Kodak Technical Pan 4415 film on a thick estar base have proved to be extremely successful. Deep, sky-limited photographs with excellent image quality and resolution have been obtained. In good seeing these reach a magnitude or more fainter than equivalent IIIa-F plates, and have considerably lower grain noise and greater photometric accuracy. Here we demonstrate quantitatively for the first time the effectiveness of this film for galaxy photometry. In particular, we find that the limiting isophote for surface photometry on an R-band, deep Tech-Pan 4415 film is about 27 Rμ or about 0.2 per cent of the measured sky background. This is over a magnitude lower than normally attained with equivalent R-band IIIa-F plates

Galaxy number counts at faint magnitudes exceed the expectations from non-evolving models, based on the present-day galaxy population, by a large margin. Despite this, redshift surveys show that the redshift distribution is as expected in the non-evolving case, lacking in particular the tail of evolved bright galaxies at high z predicted by the standard evolutionary models. We consider here the effect of using a broadly peaked, rather than steadily rising, luminosity evolution model. Evolution of this form has as its physical basis current infall models for the history of star formation in our galaxy

A significant area (about 0.5 sq deg) of the cluster A3574 was surveyed using the large-format Thomson CCD, operating at f/1 on the AAT. The candidate cluster low-surface brightness galaxies (LSBG) were selected in terms of their position in isophotal magnitude-isophotal area plot, and 300 candidates with exponential sale-sizes greater than 2 arcsec. The largest objects have scale-sizes of 12-14 arcsec, which correspond to about 3 h/kpc if they are genuine cluster members. The lowest surface brightness objects found have central values around 26.5 Vmu. It is concluded that A 3574 has a particularly large LSBG content both in terms of the surface density and the LSBG-to-giant-galaxy ratio. A catolog of the 300 candidate objects is presented and compared with the LSBG population of this cluster.

In a recent much-quoted paper, Valentijn (1990) has used the ESO-Uppsala galaxy catalog to carry out the classical surface brightness against inclination test to try to measure the opacity of spiral galaxies. From his results he infers, contrary to previous work, that galaxies are optically thick out to large radii. In this paper we show that the methods and selection criteria used by Valentijn will constrain his galaxies to have a constant surface brightness independent of their inclination, whatever their actual optical depth. We demonstrate, first, the practical efficacy of such selection biases by showing that the observed ranges of surface brightness for ESO galaxies at high and low Galactic latitude are the same, despite the obvious foreground extinction of each individual galaxy in the latter group. We then show, from simulations, that galaxies of a particular preferred observed surface brightness are always more likely to be included in the sample regardless of their inclination.

We re-examine the case for numerous invisible low surface brightness galaxies (LSBGs), rather than rare but huge galactic haloes, as the absorbers responsible for a large fraction of the metal-line systems in the spectra of distant QSOs. In particular we find that the supposed best evidence for huge haloes, i.e. the direct observation of giant galaxies at projected distances of a few Holmberg radii from the QSO line of sight, can be explained by the normal clustering of galaxies near an (invisible) LSBG absorber directly in the line of sight to the QSO. We further point out that the most recent observations of the LSBG population indicate that we should expect a very high total cross-section for this population compared to the conventional population of 'normal' galaxies. In addition, adoption of the LSBG hypothesis removes several difficulties which occur in the 'conventional' picture, such as the unaccountably high average luminosity of the giant absorbers, the enormous size of the haloes required and the lack of correlation of the metal-line equivalent width and the QSO-giant galaxy separation. Perhaps most compelling of all, though, is the fact that the LSBG hypothesis simply explains the fact that searches for bright galaxies near QSOs with metal-line systems usually succeed (there is usually a bright galaxy somewhere near the absorbing LSBG), while searches for metal-line systems in QSOs projected a few Holmberg radii from a giant galaxy usually fail (no neighbouring LSBG happens to be in precisely the right place).

In order to generate credible 0.1-2 {\mu}m SEDs, the GAMA project requires many Gigabytes of imaging data from a number of instruments to be re-processed into a standard format. In this paper we discuss the software infrastructure we use, and create self-consistent ugrizYJHK photometry for all sources within the GAMA sample. Using UKIDSS and SDSS archive data, we outline the pre-processing necessary to standardise all images to a common zeropoint, the steps taken to correct for seeing bias across the dataset, and the creation of Gigapixel-scale mosaics of the three 4x12 deg GAMA regions in each filter. From these mosaics, we extract source catalogues for the GAMA regions using elliptical Kron and Petrosian matched apertures. We also calculate S\'ersic magnitudes for all galaxies within the GAMA sample using SIGMA, a galaxy component modelling wrapper for GALFIT 3. We compare the resultant photometry directly, and also calculate the r band galaxy LF for all photometric datasets to highlight the uncertainty introduced by the photometric method. We find that (1) Changing the object detection threshold has a minor effect on the best-fitting Schechter parameters of the overall population (M* +/- 0.055mag, {\alpha} +/- 0.014, {\Phi}* +/- 0.0005 h^3 Mpc^{-3}). (2) An offset between datasets that use Kron or Petrosian photometry regardless of the filter. (3) The decision to use circular or elliptical apertures causes an offset in M* of 0.20mag. (4) The best-fitting Schechter parameters from total-magnitude photometric systems (such as SDSS modelmag or S\'ersic magnitudes) have a steeper faint-end slope than photometry dependent on Kron or Petrosian magnitudes. (5) Our Universe's total luminosity density, when calculated using Kron or Petrosian r-band photometry, is underestimated by at least 15%.

The expected optical depths of the central regions of optically thick galaxies are determined as a function of radius for five galaxies with well-observed radial gas distributions in order to gain an insight into the dramatic optical depth effects on luminosity profiles. It is found that in all cases examined, which include galaxies with a wide range of ISM densities, the extrapolated central surface brightnesses of the disks are brightened by about 0.8 mag. Galaxies with Type II luminosity profiles, i.e., those with a dip or shoulder near the center, relative to the inward extrapolation of the outer disk component, have 'normal' bulge plus disk profiles after the absorption corrections are applied. As a check on this 'missing light', a comparison with profiles obtained from IRAS data is presented. In all cases there is an excellent correspondence between the light lost from the B band, as predicted by the present optically thick disk models, and that reemitted in the far infrared.

The cross-correlation technique familiar in spectral matching to the two-dimensional case of surface photometry of galaxies with low surface brightness, i.e., to a problem of surface photometry with low signal-to-noise ratio is applied. Comparison with normal profiling methods shows a considerable improvement in the accuracy with which photometric parameters can be obtained. In particular, for simulated images representing objects like GP 1444a which are fairly large but have extremely low surface brightness, errors of only about 2 and 3 per cent in the scalelength and central intensity, smaller by a factor about 6 than the errors obtained from intensity profiles are found.

The most visible galaxies (those which have the largest apparent sizes and isophotal luminosities when seen at a given distance) are those with a particular observed surface brightness. Extending this argument to high-redshift galaxies, it is clear that this optimum surface brightness moves progressively to brighter intrinsic surface brightnesses, so as to counteract the effect of K-corrections and cosmological dimming. Thus, the galaxies appearing in faint surveys will be from a population distinctly different from those 'normal' galaxies observed nearby. Galaxies in deep surveys are more likely to be spirals and to be of high surface brightness. This has very important implications for observational studies of galaxy evolution, such as galaxy number counts, redshift surveys and the direct comparison of local and distant samples (e.g., the Butcher-Oemler effect). In particular, these distance-dependent selection biases can mimic evolutionary changes where none exist (or can help to hide real evolution), and can distort the observed luminosity function at high z.

Deep CCD frames of apparently blank regions of sky have been obtained in the hope of detecting very low surface brightness (LSB) objects in the cluster A1367. The data reduction, and image detection, and selection techniques are discussed. If the galaxies detected are actually cluster members then they are dwarfs and the conclusions of a previous paper on the Fornax cluster are essentially confirmed. One area of variance is that the lowest surface brightness galaxies do not appear to be preferentially concentrated towards the cluster center. This can be explained by there being a much larger density of dwarf galaxies over this bright galaxy-rich region of the universe. Approximately four times as many LSB galaxies are found in this small area as would be expected from the Fornax data. The possible origin and likely intensity of intergalactic light within clusters are discussed.

Lorsque les deux quasars d'une paire sont proches, des raies d'absorption peuvent etre observees dans le spectre de l'objet le plus eloigne, a un deplacement vers le rouge qui correspond a celui de l'objet le plus proche. Cela indique la presence d'une galaxie dans le meme amas (et contenant) le quasar proche. On etudie la probabilite de ce phenomene