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The study of galaxy morphology is fundamental to understand the physical processes driving the structural evolution of galaxies. It has long been known that dense environments host high fractions of early-type galaxies and low fractions of late-type galaxies, indicating that the environment affects the structural evolution of galaxies. In this paper, we present an analysis of the morphological composition of red sequence galaxies in a sample of nine galaxy clusters at 0.8

We analyse the evolution of the red sequence in a sample of galaxy clusters at redshifts 0.8 < z < 1.5 taken from the HAWK-I Cluster Survey (HCS). The comparison with the low-redshift (0.04 < z < 0.08) sample of the WIde-field Nearby Galaxy-cluster Survey (WINGS) and other literature results shows that the slope and intrinsic scatter of the cluster red sequence have undergone little evolution since z = 1.5. We find that the luminous-to-faint ratio and the slope of the faint end of the luminosity distribution of the HCS red sequence are consistent with those measured in WINGS, implying that there is no deficit of red galaxies at magnitudes fainter than M*VM at high redshifts. We find that the most massive HCS clusters host a population of bright red sequence galaxies at MV < -22.0 mag, which are not observed in low-mass clusters. Interestingly, we also note the presence of a population of very bright (MV < -23.0 mag) and massive (log (M*/M⊙) > 11.5) red sequence galaxies in the WINGS clusters, which do not include only the brightest cluster galaxies and which are not present in the HCS clusters, suggesting that they formed at epochs later than z = 0.8. The comparison with the luminosity distribution of a sample of passive red sequence galaxies drawn from the COSMOS/UltraVISTA field in the photometric redshift range 0.8 < zphot < 1.5 shows that the red sequence in clusters is more developed at the faint end, suggesting that halo mass plays an important role in setting the time-scales for the build-up of the red sequence. [ABSTRACT FROM AUTHOR]

The radial differential equations associated with separable perturbations of Kerr-Newman black holes are known to admit Liouvillian (closed-form) solutions for constrained frequencies and black hole parameters. In this paper, we show that the parameter constraints are satisfied exactly in the case of no rotation and thereby obtain a countable infinity of exact purely damped quasi-normal modes of fields on a Reissner-Nordstrom background at special values of the black hole charge-mass ratio. We show that with rotation the parameter constraints for Liouvillian quasi-normal modes are satisfied approximately in two distinct physical scenarios, where analytical approximations for angular eigenvalues are known. We arrive at functional expressions for quasi-normal frequencies and wave-functions in the case of near-extremal slow rotation and in a particular case of highly damped scalar modes of Kerr and Kerr-Newman. In the near-extremal case, our formulas extend a recent result of Hod to electromagnetic and gravitational perturbations. [ABSTRACT FROM AUTHOR]

We identify a countable infinity of new exact, closed-form, quasinormal mode perturbations of Reissner–Nordstrom black holes. We obtain a finite number of these modes explicitly, together with the values of the quasinormal frequency and the black hole charge for which the modes are valid. These modes are contained in the Liouvillian perturbations obtained from the application of Kovacic’s well-known algorithm to Chandrasekhar’s radial equations. Our results suggest that the set of quasinormal modes found in this paper, plus the known algebraically special perturbations, are the only Liouvillian quasinormal modes of Reissner–Nordstrom. [ABSTRACT FROM AUTHOR]

We examine the central galaxy luminosity–host halo mass relation for 54 brightest group galaxies (BGGs) and 92 brightest cluster galaxies (BCGs) at and present the first measurement of this relation for a sample of known BCGs at . At we find for the BCGs and the early-type BGGs in groups with extended X-ray emission and for the BCGs alone. At we find . We conclude that there is no evidence for evolution in this relationship between and : BCG growth appears to still be limited by the time-scale for dynamical friction at these earlier times, not proceeding according to the predictions of present semi-analytic models. [ABSTRACT FROM AUTHOR]

We apply the well-known Kovacic algorithm to find closed form, i.e., Liouvillian solutions, to the differential equations governing perturbations of black holes. Our analysis includes the full gravitational perturbations of Schwarzschild and Kerr, the full gravitational and electromagnetic perturbations of Reissner-Nordstrom, and specialized perturbations of the Kerr-Newman geometry. We also include the extreme geometries. We find all frequencies ω, in terms of black hole parameters and an integer n, which allow Liouvillian perturbations. We display many classes of black hole parameter values and their corresponding Liouvillian perturbations, including new closed-form perturbations of Kerr and Reissner-Nordstrom. We also prove that the only type 1 Liouvillian perturbations of Schwarzschild are the known algebraically special ones and that type 2 Liouvillian solutions do not exist for extreme geometries. In cases where we do not prove the existence or nonexistence of Liouvillian perturbations we obtain sequences of Diophantine equations on which decidability rests. [ABSTRACT FROM AUTHOR]

We investigate the structural, kinematical and spectrophotometric properties of‘E+A’ galaxies– those with strong Balmer absorption lines but no significant[O ii] emission– using numerical simulations combined with stellar population synthesis codes. We particularly focus on the two-dimensional (2D) distributions of line-of-sight velocity, velocity dispersion, colour and line index in E+A galaxies formed via the interaction and merging of two gas-rich spirals. Our numerical simulations demonstrate that E+A elliptical galaxies formed by major galaxy merging have positive radial colour gradients and negative radial Hδ gradients by virtue of their central post-starburst populations. Furthermore, we show that the projected kinematical and spectroscopic properties of the simulated E+A galaxies can be remarkably different for different major merger models. For example, the simulated E+A ellipticals with kinematically decoupled cores clearly show regions of strong Hδ absorption which are very flattened, with differences in rotation and velocity dispersion between the old and young stars. E+A ellipticals are highly likely to show more rapid rotation and a smaller central velocity dispersion in young stars than in old ones. E+A galaxies formed from the strong tidal interaction between gas-rich spirals have discy morphologies with thick discs and are highly likely to be morphologically classified as barred S0 galaxies. We also provide specific predictions on the structural, kinematical and spectrophotometric properties of young globular cluster systems in E+A galaxies. Based on these results, we discuss the importance of spatially resolved, integral field unit spectroscopy on large (8–10 m) ground-based telescopes in confirming the formation of kinematically distinct cores in elliptical galaxies produced via dissipative merging and determining the most probable physical mechanism(s) for E+A formation with discy and spheroidal morphologies. [ABSTRACT FROM AUTHOR]

Methods from the author’s previous work and the classes of solutions which they produce are extended to the wave equations which govern the massive scalar field and the massless spin- 1/2 field on the Kerr–Newman geometry and the massless fields of spin 1 and 2 on the Kerr geometry. The solutions found are exact and expressed in simple closed forms in terms of elementary functions, but they only exist when appropriate constraints hold on some of the black hole parameters and on the frequency of the field in some cases. The behavior on the horizon, at null infinity, and with respect to the angular variables is analyzed for some example solutions. For the examples studied, it is found that the ones having radial behavior of a normal mode are not free of angular singularities. An exact relation is established between the scalar wave equation on the extreme Kerr–Newman geometry and the Whittaker–Hill equation. [ABSTRACT FROM AUTHOR]

A recent paper by Gottlieb [J. Math. Phys. 29, 2434 (1988)] provides examples of acoustic wave equations, in various dimensions, that have nontrivial families of solutions that are progressing waves of order 1, and relates this to whether or not these equations satisfy Huygens’ principle. A statement made in that paper related to Huygens’ principle in one space dimension is clarified, and it is shown in this connection that, in general, the relationship between the possession of progressing wave solutions and the satisfaction of Huygens’ principle is more complex than the situation described by Gottlieb. In addition, the attractive properties of progressing waves of order 1 are retained by progressing waves of any finite order, and we use this to generalize in several ways Gottlieb’s results on ‘‘wake-free’’ solutions of the acoustic equation in three dimensions. [ABSTRACT FROM AUTHOR]

Introduction:Given the considerable time and research cost of analyzing biomedical images to quantify adipose tissue volumes, automated image analysis methods are highly desirable. Hippo Fat™ is a new software program designed to automatically quantify adipose tissue areas from magnetic resonance images without user inputs. Hippo Fat™ has yet to be independently validated against commonly used image analysis software programs.Objective:Our aim was to compare estimates of VAT (visceral adipose tissue) and SAT (subcutaneous adipose tissue) using the new Hippo Fat™ software against those from a widely used, validated, computer-assisted manual method (slice-O-matic version 4.2, Tomovision, Montreal, CA, USA) to assess its potential utility for large-scale studies.Methods:A Siemens Magnetom Vision 1.5-T whole-body scanner and a T1-weighted fast-spin echo pulse sequence were used to collect multiple, contiguous axial images of the abdomen from a sample of 40 healthy adults (20 men) aged 18–77 years of age, with mean body mass index of 29 kg/m2 (range=19–43 kg/m2).Results:Hippo Fat™ provided estimates of VAT and SAT that were highly correlated with estimates using slice-O-matic (R 2>0.9). Average VAT was 9.4% lower and average SAT was 3.7% higher using Hippo Fat™ compared to slice-O-matic; the overestimation of SAT tended to be greater among individuals with greater adiposity. Individual-level differences for VAT were also substantial; Hippo Fat™ gave estimates of VAT ranging from 1184 cm3 less to 566 cm3 more than estimates for the same person using slice-O-matic.Conclusion:Hippo Fat™ provides a rapid method of quantifying total VAT, although the method does not provide estimates that are interchangeable with slice-O-matic at either the group (mean) or individual level.International Journal of Obesity (2007) 31, 285–291. doi:10.1038/sj.ijo.0803409; published online 13 June 2006 [ABSTRACT FROM AUTHOR]

We present the bivariate brightness distribution (BBD) for the 2dF Galaxy Redshift Survey (2dFGRS) based on a preliminary subsample of 45 000 galaxies. The BBD is an extension of the galaxy luminosity function, incorporating surface brightness information. It allows the measurement of the local luminosity density, jB, and of the galaxy luminosity and surface brightness distributions, while accounting for surface brightness selection biases. The recovered 2dFGRS BBD shows a strong luminosity–surface brightness relation MB∝(2.4±0.51.5)μe], providing a new constraint for galaxy formation models. In terms of the number density, we find that the peak of the galaxy population lies at MB≥-16.0 mag. Within the well-defined selection limits (-24

Ground-based near-infrared (NIR) astronomy is severely hampered by the forest of atmospheric emission lines resulting from the rovibrational decay of OH molecules in the upper atmosphere. The extreme brightness of these lines, as well as their spatial and temporal variability, makes accurate sky subtraction difficult. Selectively filtering these lines with OH suppression instruments has been a long standing goal for NIR spectroscopy. We have shown previously the efficacy of fibre Bragg gratings (FBGs) combined with photonic lanterns for achieving OH suppression. Here we report on PRAXIS, a unique NIR spectrograph that is optimized for OH suppression with FBGs. We show for the first time that OH suppression (of any kind) is possible with high overall throughput (18 per cent end-to-end), and provide examples of the relative benefits of OH suppression. [ABSTRACT FROM AUTHOR]

Misalignment of gas and stellar rotation in galaxies can give clues to the origin and processing of accreted gas. Integral field spectroscopic observations of 1213 galaxies from the Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey show that 11 per cent of galaxies with fitted gas and stellar rotation are misaligned by more than 30° in both field/group and cluster environments. Using SAMI morphological classifications and Sérsic indices, the misalignment fraction is 45 ± 6 per cent in early-type galaxies (ETGs), but only 5 ± 1 per cent in late-type galaxies (LTGs). The distribution of position angle offsets is used to test the physical drivers of this difference. Slower dynamical settling time of the gas in elliptical stellar mass distributions accounts for a small increase in misalignment in early-type galaxies. However, gravitational dynamical settling time is insufficient to fully explain the observed differences between ETGs and LTGs in the distributions of the gas/stellar position angle offsets. LTGs have primarily accreted gas close to aligned rather than settled from misaligned based on analysis of the skewed distribution of PA offsets compared to a dynamical settling model. Local environment density is less important in setting the misalignment fractions than morphology, suggesting that mergers are not the main source of accreted gas in these discs. Cluster environments are found to have gas misalignment driven primarily by cluster processes not by gas accretion. [ABSTRACT FROM AUTHOR]

Recently, large samples of visually classified early-type galaxies (ETGs) containing dust have been identified using space-based infrared observations with the Herschel Space Telescope. The presence of large quantities of dust in massive ETGs is peculiar as X-ray haloes of these galaxies are expected to destroy dust in ~107 yr (or less). This has sparked a debate regarding the origin of the dust: Is it internally produced by asymptotic giant branch stars, or is it accreted externally through mergers? We examine the 2D stellar and ionized gas kinematics of dusty ETGs using integral field spectroscopy observations from the SAMI Galaxy Survey, and integrated star formation rates, stellar masses and dust masses from the GAMA survey. Only 8 per cent (4/49) of visually classified ETGs are kinematically consistent with being dispersion-supported systems. These 'dispersion-dominated galaxies' exhibit discrepancies between stellar and ionized gas kinematics, either offsets in the kinematic position angle or large differences in the rotational velocity, and are outliers in star formation rate at a fixed dust mass compared to normal star-forming galaxies. These properties are suggestive of recent merger activity. The remaining ~90 per cent of dusty ETGs have low velocity dispersions and/or large circular velocities, typical of 'rotation-dominated galaxies'. These results, along with the general evidence of published works on X-ray emission in ETGs, suggest that they are unlikely to host hot, X-ray gas consistent with their low M* when compared to dispersion-dominated galaxies. This means that dust will be long-lived and thus these galaxies do not require external scenarios for the origin of their dust content. [ABSTRACT FROM AUTHOR]

We investigate the relationship between stellar and gas specific angular momentum j, stellar mass M* and optical morphology for a sample of 488 galaxies extracted from the Sydney-AAO Multi-object Integral field Galaxy Survey. We find that j, measured within one effective radius, monotonically increases with M* and that, for M* > 109.5 M⊙, the scatter in this relation strongly correlates with optical morphology (i.e. visual classification and Sérsic index). These findings confirm that massive galaxies of all types lie on a plane relating mass, angular momentum and stellar-light distribution, and suggest that the large-scale morphology of a galaxy is regulated by its mass and dynamical state. We show that the significant scatter in the M*-j relation is accounted for by the fact that, at fixed stellar mass, the contribution of ordered motions to the dynamical support of galaxies varies by at least a factor of 3. Indeed, the stellar spin parameter (quantified via λR) correlates strongly with Sérsic and concentration indices. This correlation is particularly strong once slow rotators are removed from the sample, showing that late-type galaxies and early-type fast rotators form a continuous class of objects in terms of their kinematic properties. [ABSTRACT FROM AUTHOR]

Aims. Using V band photometry of the WINGS survey, we derive galaxy luminosity functions (LF) in nearby clusters. This sample is complete down to MV = -15.15, and it is homogeneous, thus facilitating the study of an unbiased sample of clusters with different characteristics. Methods. We constructed the photometric LF for 72 out of the original 76 WINGS clusters, excluding only those without a velocity dispersion estimate. For each cluster we obtained the LF for galaxies in a region of radius = 0.5 x r200, and fitted them with single and double Schechter's functions. We also derive the composite LF for the entire sample, and those pertaining to different morphological classes. Finally, we derive the spectroscopic cumulative LF for 2009 galaxies that are cluster members. Results. The double Schechter fit parameters are correlated neither with the cluster velocity dispersion nor with the X-ray luminosity. Our median values of the Schechter's fit slope are, on average, in agreement with measurements of nearby clusters, but are less steep that those derived from large surveys, such as the SDSS. Early-type galaxies out number late-types at all magnitudes, but both early and late types contribute equally to the faint end of the LF. Finally, the spectroscopic LF is in excellent agreement with the one derived for A2199, A85 and Virgo, and with the photometric LF at the bright magnitudes (where both are available). Conclusions. There is a large spread in the LF of different clusters, however, this spread is not caused by correlation of the LF shape with cluster characteristics such as X-ray luminosity or velocity dispersions. The faint end is flatter than previously derived (αf = -1.7), which is at odds with that predicted from numerical simulations. [ABSTRACT FROM AUTHOR]

Context. Wide-field observations targeting galaxy clusters at low redshift are complementary to field surveys and provide the local benchmark for detailed studies of the most massive haloes in the local Universe. The Wide-field Nearby Galaxy-cluster Survey (WINGS) is a wide-field multi-wavelength survey of X-ray selected clusters at z = 0.04-0.07. The original 34' x 34' WINGS field of view has now been extended to cover a 1 deg² field with both photometry and spectroscopy. Aims. We present the Johnson B- and V-band OmegaCAM at the VST observations of 46 WINGS clusters together with the data reduction, data quality, and Sextractor photometric catalogues. Methods. The data reduction was carried out with a modified version of the ESO-MVM (also known as ALAMBIC) reduction package, adding a cross-talk correction, the gain harmonisation, and a control procedure for problematic CCDs. The stray-light component was corrected for by employing our own observations of populated stellar fields. Results. With a median seeing of 1" in both bands, our 25-min exposures in each band typically reach the 50% completeness level at V = 23.1 mag. The quality of the astrometric and photometric accuracy has been verified by comparison with the 2MASS and SDSS astrometry, and SDSS and previous WINGS imaging. Star-to-galaxy separation and sky-subtraction procedure were tested comparing them with previous WINGS data. Conclusions. The Sextractor photometric catalogues are publicly available at the CDS and will be included in the next release of the WINGS database on the Virtual Observatory together with the OmegaCAM reduced images. These data form the basis for a large ongoing spectroscopic campaign with AAOmega at the AAT and are being employed for a variety of studies. [ABSTRACT FROM AUTHOR]

We present the morphology-density and morphology-radius relations (T-∑ and T-R, respectively) obtained from the WIde-field Nearby Galaxy-cluster Survey (WINGS) data base of galaxies in nearby clusters. Aiming to achieve the best statistics, we exploit the whole sample of galaxies brighter than MV=-19.5 (5504 objects), stacking up the 76 clusters of the WINGS survey altogether. Using this global cluster sample, we find that the T-∑ relation holds only in the inner cluster regions (R < 1/3 R200), while the T-R relation keeps almost unchanged over the whole range of local density. A couple of tests and two sets of numerical simulations support the robustness of these results against the effects of the limited cluster area coverage of the WINGS imaging. The above mentioned results hold for all cluster masses (X-ray luminosity and velocity dispersion) and all galaxy stellar masses (M*). The strength of the T-∑ relation (where present) increases with increasing M*, while this effect is not found for the T-R relation. Noticeably, the absence/presence of subclustering determines the presence/absence of the T-∑ relation outside the inner cluster regions, leading us to the general conclusion that the link between morphology and local density is preserved just in dynamically evolved regions. We hypothesize that some mechanism of morphological broadening/redistribution operates in the intermediate/outer regions of substructured ('non-relaxed') clusters, producing a strong weakening of the T-∑ relation. [ABSTRACT FROM AUTHOR]

We present a methodology for the regularization and combination of sparse sampled and irregularly gridded observations from fibre-optic multiobject integral field spectroscopy. The approach minimizes interpolation and retains image resolution on combining subpixel dithered data. We discuss the methodology in the context of the Sydney-AAO multiobject integral field spectrograph (SAMI) Galaxy Survey underway at the Anglo-Australian Telescope. The SAMI instrument uses 13 fibre bundles to perform high-multiplex integral field spectroscopy across a 1엯 diameter field of view. The SAMI Galaxy Survey is targeting 3000 galaxies drawn from the full range of galaxy environments. We demonstrate the subcritical sampling of the seeing and incomplete fill factor for the integral field bundles results in only a 10 per cent degradation in the final image resolution recovered. We also implement a new methodology for tracking covariance between elements of the resulting data cubes which retains 90 per cent of the covariance information while incurring only a modest increase in the survey data volume. [ABSTRACT FROM AUTHOR]

Context. Cluster galaxies are the ideal sites to look at when studying the influence of the environment on the various aspects of the evolution of galaxies, such as the changes in their stellar content and morphological transformations. In the framework ofwings, the WIde-field Nearby Galaxy-cluster Survey, we have obtained optical spectra for ~6000 galaxies selected in fields centred on 48 local (0.04 < z < 0.07) X-ray selected clusters to tackle these issues. Aims. By classifying the spectra based on given spectral lines, we investigate the frequency of the various spectral types as a function of both the clusters' properties and the galaxies' characteristics. In this way, using the same classification criteria adopted for studies at higher redshift, we can consistently compare the properties of the local cluster population to those of their more distant counterparts. Methods. We describe a method that we have developed to automatically measure the equivalent width of spectral lines in a robust way, even in spectra with a non optimal signal-to-noise ratio. This way, we can derive a spectral classification reflecting the stellar content, based on the presence and strength of the [Oii] and Hd lines. Results. After a quality check, we are able to measure 4381 of the ~6000 originally observed spectra in the fields of 48 clusters, of which 2744 are spectroscopically confirmed cluster members. The spectral classification is then analysed as a function of galaxies' luminosity, stellar mass, morphology, local density, and host cluster's global properties and compared to higher redshift samples (MORPHS and EDisCS). The vast majority of galaxies in the local clusters population are passive objects, being also the most luminous and massive. At a magnitude limit of MV < -18, galaxies in a post-starburst phase represent only ~11% of the cluster population, and this fraction is reduced to ~5% at MV < -19.5, which compares to the 18% at the same magnitude limit for high-z clusters. "Normal" star-forming galaxies (e(c)) are proportionally more common in local clusters. Conclusions. The relative occurrence of post-starbursts suggests a very similar quenching efficiency in clusters at redshifts in the0 to ~1 range. Furthermore, more important than the global environment, the local density seems to be the main driver of galaxy evolution in local clusters at least with respect to their stellar populations content. [ABSTRACT FROM AUTHOR]

Context. To effectively investigate galaxy formation and evolution, it is of paramount importance to exploit homogeneous data for large samples of galaxies in different environments. Aims. The WIde-field Nearby Galaxy-cluster Survey (WINGS) project aim is to evaluate physical properties of galaxies in a complete sample of low redshift clusters to be used as reference sample for evolutionary studies. The WINGS survey is still ongoing and the original dataset will be enlarged with new observations. This paper presents the entire collection of WINGS measurements obtained so far. Methods. We decided to make use of the Virtual Observatory (VO) tools to share the WINGS database (that will be updated regularly) with the community. In the database each object has one unique identification (WINGSID). Each subset of estimated properties is accessible using a cone search (including wide-field images). Results. We provide the scientific community with the entire set of wide-field images. Furthermore, the published database contains photometry of 759 024 objects and surface brightness analysis for 42 275 and 41 463 galaxies in the V and B band, respectively. The completeness depends on the image quality, and on the cluster redshift, reaching on average 90% at V ⩽ 21.7. Near-infrared photometric catalogs for 26 (in K) and 19 (in J) clusters are part of the database and the number of sources is 962 344 in K and 628 813 in J. Here again the completeness depends on the data quality, but it is on average higher than 90% for J ⩽ 20.5 and K ⩽ 19.4. The IR subsample with a Sersic fit comprises 71 687 objects. A morphological classification is available for 39 923 galaxies. We publish spectroscopic data, including 6132 redshifts, 5299 star formation histories, and 4381 equivalent widths. Finally, a calculation of local density is presented and implemented in the VO catalogs for 66 164 galaxies. The latter is presented here for the first time. [ABSTRACT FROM AUTHOR]

ABSTRACT The background noise between 1 and 1.8 μm in ground-based instruments is dominated by atmospheric emission from hydroxyl molecules. We have built and commissioned a new instrument, the Gemini Near-infrared OH Suppression Integral Field Unit (IFU) System (GNOSIS), which suppresses 103 OH doublets between 1.47 and 1.7 μm by a factor of ≈1000 with a resolving power of ≈10 000. We present the first results from the commissioning of GNOSIS using the IRIS2 spectrograph at the Anglo-Australian Telescope. We present measurements of sensitivity, background and throughput. The combined throughput of the GNOSIS fore-optics, grating unit and relay optics is ≈36 per cent, but this could be improved to ≈46 per cent with a more optimal design. We measure strong suppression of the OH lines, confirming that OH suppression with fibre Bragg gratings will be a powerful technology for low-resolution spectroscopy. The integrated OH suppressed background between 1.5 and 1.7 μm is reduced by a factor of 9 compared to a control spectrum using the same system without suppression. The potential of low-resolution OH-suppressed spectroscopy is illustrated with example observations of Seyfert galaxies and a low-mass star. The GNOSIS background is dominated by detector dark current below 1.67 μm and by thermal emission above 1.67 μm. After subtracting these, we detect an unidentified residual interline component of ≈860 ± 210 photons s−1 m−2 arcsec−2 μm−1, comparable to previous measurements. This component is equally bright in the suppressed and control spectra. We have investigated the possible source of the interline component, but were unable to discriminate between a possible instrumental artefact and intrinsic atmospheric emission. Resolving the source of this emission is crucial for the design of fully optimized OH suppression spectrographs. The next-generation OH suppression spectrograph will be focused on resolving the source of the interline component, taking advantage of better optimization for a fibre Bragg grating feed incorporating refinements of design based on our findings from GNOSIS. We quantify the necessary improvements for an optimal OH suppressing fibre spectrograph design. [ABSTRACT FROM AUTHOR]

ABSTRACT We present the morphological catalogue of galaxies in nearby clusters of the WIde-field Nearby Galaxy-clusters Survey (WINGS). The catalogue contains a total number of 39 923 galaxies, for which we provide the automated estimates of the morphological type, applying the purposely devised tool MORPHOT to the V-band WINGS imaging. For ∼3000 galaxies we also provide visual estimates of the morphological type. A substantial part of the paper is devoted to the description of the MORPHOT tool, whose application is limited, at least for the moment, to the WINGS imaging only. The approach of the tool to the automation of morphological classification is a non-parametric and fully empirical one. In particular, MORPHOT exploits 21 morphological diagnostics, directly and easily computable from the galaxy image, to provide two independent classifications: one based on a maximum likelihood (ML), semi-analytical technique and the other one on a neural network (NN) machine. A suitably selected sample of ∼1000 visually classified WINGS galaxies is used to calibrate the diagnostics for the ML estimator and as a training set in the NN machine. The final morphological estimator combines the two techniques and proves to be effective both when applied to an additional test sample of ∼1000 visually classified WINGS galaxies and when compared with small samples of Sloan Digital Sky Survey (SDSS) galaxies visually classified by Fukugita et al. and Nair et al. Finally, besides the galaxy morphology distribution (corrected for field contamination) in the WINGS clusters, we present the ellipticity (ɛ), colour ( B− V) and Sersic index ( n) distributions for different morphological types, as well as the morphological fractions as a function of the clustercentric distance (in units of R200). [ABSTRACT FROM AUTHOR]

We compare the apparent axial ratio distributions of the brightest cluster galaxies (BCGs) and normal ellipticals (Es) in our sample of 75 galaxy clusters from the WIde-field Nearby Galaxy-cluster Survey (WINGS). Most BCGs in our clusters (69 per cent) are classified as cD galaxies. The sample of cDs has been completed by 14 additional cDs (non-BCGs) we found in our clusters. We deproject the apparent axial ratio distributions of Es, BCGs and cDs using a bivariate version of the Lucy rectification algorithm, whose results are supported by an independent Monte Carlo technique. Finally, we compare the intrinsic shape distribution of BCGs to the corresponding shape distribution of the central part of cluster-sized dark matter haloes extracted from the GIF2 Lambda cold dark matter (ΛCDM) N-body simulations (Gao et al.). We find that (i) Es have triaxial shape, the triaxiality sharing almost evenly the intrinsic axial ratio parameter space, with a weak preference for prolateness and (ii) the BCGs have triaxial shape as well. However, their tendency towards prolateness is much stronger than in the case of Es. Such a strong prolateness appears entirely due to the sizeable (dominant) component of cDs inside the WINGS sample of BCGs. In fact, while the ‘normal’ (non-cD) BCGs do not differ from Es, as far as the shape distribution is concerned, the axial ratio distribution of BCG_cD galaxies is found to support quite prolate shapes; (iii) our result turns out to be strongly at variance with the only similar previous analysis by Ryden, Lauer & Postman (RLP93), where BCGs and Es were found to share the same axial ratio distribution; (iv) our data suggest that the above discrepancy is mainly caused by the different criteria that RLP93 and ourselves use to select the cluster samples, coupled with a preference of cDs to reside in powerful X-ray-emitting clusters; (v) the -body results suggest that the prolateness of the BCGs (in particular the cDs) could reflect the shape of the associated dark matter haloes. [ABSTRACT FROM AUTHOR]

We combine the quasi-stellar object (QSO) samples from the 2dF QSO Redshift Survey (2QZ) and the 2dF-Sloan Digital Sky Survey luminous red galaxy (LRG) and QSO Survey (2dF-SDSS LRG and QSO, hereafter 2SLAQ) in order to investigate the clustering of z∼ 1.5 QSOs and measure the correlation function (ξ). The clustering signal in redshift-space and projected along the sky direction is similar to that previously obtained from the 2QZ sample alone. By fitting functional forms for ξ(σ, π), the correlation function measured along and across the line of sight, we find, as expected, that β, the dynamical infall parameter and , the cosmological density parameter, are degenerate. However, this degeneracy can be lifted by using linear theory predictions under different cosmological scenarios. Using the combination of the 2QZ and 2SLAQ QSO data, we obtain: which imply a value for the QSO bias, . The combination of the 2QZ with the fainter 2SLAQ QSO sample further reveals that QSO clustering does not depend strongly on luminosity at fixed redshift. This result is inconsistent with the expectation of simple ‘high peaks’ biasing models where more luminous, rare QSOs are assumed to inhabit higher mass haloes. The data are more consistent with models which predict that QSOs of different luminosities reside in haloes of similar mass. By assuming ellipsoidal models for the collapse of density perturbations, we estimate the mass of the dark matter haloes which the QSOs inhabit as . We find that this halo mass does not evolve strongly with redshift nor depend on QSO luminosity. Assuming a range of relations which relate halo to black hole mass, we investigate how black hole mass correlates with luminosity and redshift, and ascertain the relation between Eddington efficiency and black hole mass. Our results suggest that QSOs of different luminosities may contain black holes of similar mass. [ABSTRACT FROM AUTHOR]

Using 10 095 galaxies 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); two-degree Field Galaxy Redshift Survey (2dFGRS) η parameter; rest- 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 subsets 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- colour and log ( n) distributions. Whilst the former bimodality was well established from Sloan Digital Sky Survey data, we show here that the rest- 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 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 ( , 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 stellar mass content in spheroids, bulges and discs is and per cent, respectively. [ABSTRACT FROM AUTHOR]

We present a new scenario in which massive intragroup H i clouds are the high-density parts of large H i rings/arcs formed by dynamical interaction between galaxy groups and gas-rich, low surface brightness (LSB) galaxies with extended gas discs. Our hydrodynamical simulations demonstrate that the group tidal field is very efficient at stripping the outer H i gas of the disc if the gaseous disc of the LSB galaxy extends 2–5 times further than the stellar disc. We find that a massive, extended ‘leading stream’ orbiting the centre of the group can form out of the stripped outer H i envelope, while the severely shrunken LSB galaxy, whose stellar disc remains unaffected, continues on its path. The result is a relatively isolated, massive H i cloud with a ring- or arc-like shape, a very inhomogeneous density distribution , and, initially, no stellar content. Only the high-density peaks of the simulated intragroup H i ring/arc can be detected in many current H i observations. These will appear as relatively isolated ‘H i islands’ near the group centre. We also find that star formation can occur within the ring/arc, if the total gas mass within the intragroup ring/arc is very large . We discuss these results in terms of existing observations of intragroup gas (e.g. the Leo Ring and HIPASS J0731–69) and intergalactic H ii regions. [ABSTRACT FROM AUTHOR]

We use the 2dF Galaxy Redshift Survey to measure the dependence of thebJ-band galaxy luminosity function on large-scale environment, defined by density contrast in spheres of radius, and on spectral type, determined from principal component analysis. We find that the galaxy populations at both extremes of density differ significantly from that at the mean density. The population in voids is dominated by late types and shows, relative to the mean, a deficit of galaxies that becomes increasingly pronounced at magnitudes brighter than. In contrast, cluster regions have a relative excess of very bright early-type galaxies with. Differences in the mid- to faint-end population between environments are significant: atearly- and late-type cluster galaxies show comparable abundances, whereas in voids the late types dominate by almost an order of magnitude. We find that the luminosity functions measured in all density environments, from voids to clusters, can be approximated by Schechter functions with parameters that vary smoothly with local density, but in a fashion that differs strikingly for early- and late-type galaxies. These observed variations, combined with our finding that the faint-end slope of the overall luminosity function depends at most weakly on density environment, may prove to be a significant challenge for models of galaxy formation. [ABSTRACT FROM AUTHOR]

We measure moments of the galaxy count probability distribution function in the Two-degree Field Galaxy Redshift Survey (2dFGRS). The survey is divided into volume-limited subsamples in order to examine the dependence of the higher-order clustering on galaxy luminosity. We demonstrate the hierarchical scaling of the averaged p-point galaxy correlation functions, [This equation cannot be represented into ASCII Text] up to p = 6. The hierarchical amplitudes, [This equation cannot be represented into ASCII Text] are approximately independent of the cell radius used to smooth the galaxy distribution on small to medium scales. On larger scales we find that the higher-order moments can be strongly affected by the presence of rare, massive superstructures in the galaxy distribution. The skewness S3 has a weak dependence on luminosity, approximated by a linear dependence on log luminosity. We discuss the implications of our results for simple models of linear and non-linear bias that relate the galaxy distribution to the underlying mass. [ABSTRACT FROM AUTHOR]

We measure the redshift-space reduced void probability function (VPF) for 2dFGRS volume-limited galaxy samples covering the absolute magnitude range to −22. Theoretically, the VPF connects the distribution of voids to the moments of galaxy clustering of all orders, and can be used to discriminate clustering models in the weakly non-linear regime. The reduced VPF measured from the 2dFGRS is in excellent agreement with the paradigm of hierarchical scaling of the galaxy clustering moments. The accuracy of our measurement is such that we can rule out, at a very high significance, popular models for galaxy clustering, including the lognormal distribution. We demonstrate that the negative binomial model gives a very good approximation to the 2dFGRS data over a wide range of scales, out to at least 20 h−1 Mpc. Conversely, the reduced VPF for dark matter in a Λ cold dark matter (ΛCDM) universe does appear to be lognormal on small scales but deviates significantly beyond . We find little dependence of the 2dFGRS reduced VPF on galaxy luminosity. Our results hold independently in both the North and South Galactic Pole survey regions. [ABSTRACT FROM AUTHOR]

Abstract We investigate the spatial, kinematic and chemical properties of globular cluster systems formed in merging and interacting galaxies using N-body–smoothed particle hydrodynamics (SPH) simulations. Although we cannot resolve individual clusters in our simulation, we assume that they form in collapsing molecular clouds when the local external gas pressure exceeds 10[sup 5]k[sub B] (where k[sub B] is the Boltzmann constant). Several simulations are carried out for a range of initial conditions and galaxy mass ratios. The input model spirals are given a halo globular cluster system similar to those observed for the Milky Way and M31. Gravitational tidal effects during galaxy merging and interaction lead to a dramatic increase in gas pressure, which exceeds our threshold and hence triggers new globular cluster formation. We investigate the properties of the globular cluster system in the remnant galaxy, such as the number density, the specific frequency, kinematic properties and the metallicity distribution. Different orbital conditions and mass ratios give rise to a range in globular cluster properties, particularly for the interaction models. Our key results are the following: the newly formed metal-rich clusters are concentrated at the centre of the merger remnant elliptical, whereas the metal-poor ones are distributed to the outer parts because of strong angular momentum transfer. The dissipative merging of present-day spirals, including chemical evolution, results in metal-rich clusters with a mean metallicity that is super-solar, i.e. much higher than is observed in elliptical galaxies. If elliptical galaxies form by dissipative major mergers, then they must do so at very early epochs when their discs contained low-metallicity gas. Our simulations show that the specific frequency can be increased in a dissipative major merger. However, when this occurs it results in a ratio of metal-poor to metal-rich clusters that is less than one, contrary to the ratio observed in many elliptical galaxies. [ABSTRACT FROM AUTHOR]

We compute the bispectrum of the 2dF Galaxy Redshift Survey (2dFGRS) and use it to measure the bias parameter of the galaxies. This parameter quantifies the strength of clustering of the galaxies relative to the mass in the Universe. By analysing 80 × 10[sup 6] triangle configurations in the wavenumber range 0.1 < k < 0.5 h Mpc[sup -1] (i.e. on scales roughly between 5 and 30 h[sup -1] Mpc) we find that the linear bias parameter is consistent with unity: b[sub 1]= 1.04 ± 0.11, and the quadratic (non-linear) bias is consistent with zero: b[sub 2]=-0.054 ± 0.08. Thus, at least on large scales, optically selected galaxies do indeed trace the underlying mass distribution. The bias parameter can be combined with the 2dFGRS measurement of the redshift distortion parameter β≃Ω[sub m][sup 0.6]/b[sub 1], to yield Ω[sub m]= 0.27 ± 0.06 for the matter density of the Universe, a result that is determined entirely from this survey, independent of other data sets. Our measurement of the matter density of the Universe should be interpreted as Ω[sub m] at the effective redshift of the survey (z= 0.17). [ABSTRACT FROM AUTHOR]

We have cross-matched the 1.4-GHz NRAO VLA Sky Survey (NVSS) with the first 210 fields observed in the 2dF Galaxy Redshift Survey (2dFGRS), covering an effective area of 325 deg[sup 2] (about 20 per cent of the final 2dFGRS area). This yields a set of optical spectra of 912 candidate NVSS counterparts, of which we identify 757 as genuine radio identifications – the largest and most homogeneous set of radio source spectra ever obtained. The 2dFGRS radio sources span the redshift range z=0.005 to 0.438, and are a mixture of active galaxies (60 per cent) and star-forming galaxies (40 per cent). About 25 per cent of the 2dFGRS radio sources are spatially resolved by NVSS, and the sample includes three giant radio galaxies with projected linear size greater than 1 Mpc. The high quality of the 2dF spectra means we can usually distinguish unambiguously between AGN and star-forming galaxies. We make a new determination of the local radio luminosity function at 1.4 GHz for both active and star-forming galaxies, and derive a local star formation density of 0.022±0.004 M[sub ⊙] yr[sup -1] Mpc[sup -3] (H[sub 0]=50 km s[sup -1] Mpc[sup -1]). [ABSTRACT FROM AUTHOR]

We describe the 2dF Galaxy Redshift Survey (2dFGRS) and the current status of the observations. In this exploratory paper, we apply a principal component analysis to a preliminary sample of 5869 galaxy spectra and use the two most significant components to split the sample into five spectral classes. These classes are defined by considering visual classifications of a subset of the 2dF spectra, and also by comparison with high-quality spectra of local galaxies. We calculate a luminosity function for each of the different classes and find that later-type galaxies have a fainter characteristic magnitude, and a steeper faint-end slope. For the whole sample we find M*=-19.7 (for Ω=1, H[sub 0]=100 km s[sup -1] Mpc[sup -1]), α=-1.3, φ*=0.017. For class 1 (‘early-type’) we find M*=-19.6, α=-0.7, while for class 5 (‘late-type’) we find M*=-19.0, α=-1.7. The derived 2dF luminosity functions agree well with other recent luminosity function estimates. [ABSTRACT FROM AUTHOR]

Dwarf galaxies have attracted increased attention in recent years, because of their susceptibility to galaxy transformation processes within rich galaxy clusters. Direct evidence for these processes, however, has been difficult to obtain, with a small number of diffuse light trails and intra-cluster stars being the only signs of galaxy disruption. Furthermore, our current knowledge of dwarf galaxy populations may be very incomplete, because traditional galaxy surveys are insensitive to extremely diffuse or compact galaxies. Aware of these concerns, we recently undertook an all-object survey of the Fornax galaxy cluster. This revealed a new population of compact members, overlooked in previous conventional surveys. Here we demonstrate that these 'ultra-compact' dwarf galaxies are structurally and dynamically distinct from both globular star dusters and known types of dwarf galaxy, and thus represent a new class of dwarf galaxy. Our data are consistent with the interpretation that these are the remnant nuclei of disrupted dwarf galaxies, making them an easily observed tracer of galaxy disruption. [ABSTRACT FROM AUTHOR]

We use the Two-Degree Field Galaxy Redshift Survey (2dFGRS) to test the hierarchical scaling hypothesis: namely, that the p-point galaxy correlation functions can be written in terms of the two-point correlation function or variance. This scaling is expected if an initially Gaussian distribution of density fluctuations evolves under the action of gravitational instability. We measure the volume-averaged p-point correlation functions using a counts-in-cells technique applied to a volume-limited sample of 44 931 L* galaxies. We demonstrate that L* galaxies display hierarchical clustering up to order in redshift space. The variance measured for L* galaxies is in excellent agreement with the predictions from a Λ-cold dark matter N-body simulation. This applies to all cell radii considered, . However, the higher order correlation functions of L* galaxies have a significantly smaller amplitude than is predicted for the dark matter for . This disagreement implies that a non-linear bias exists between the dark matter and L* galaxies on these scales. We also show that the presence of two rare, massive superclusters in the 2dFGRS has an impact on the higher-order clustering moments measured on large scales. [ABSTRACT FROM AUTHOR]