Subarcsecond Seeing Research Articles

The Next Generation Virgo Cluster Survey (NGVS). III. A Catalog of Surface Brightness Fluctuation Distances and the Three-dimensional Distribution of Galaxies in the Virgo Cluster

The surface brightness fluctuation (SBF) method is a robust and efficient way of measuring distances to galaxies containing evolved stellar populations. Although many recent applications of the method have used space-based imaging, SBF remains a powerful technique for ground-based telescopes. Deep, wide-field imaging surveys with subarcsecond seeing enable SBF measurements for numerous nearby galaxies. Using a preliminary calibration, Cantiello et al. presented SBF distances for 89 bright, mainly early-type galaxies observed in the Next Generation Virgo Cluster Survey. Here we present a refined calibration and SBF distances for 278 galaxies extending several magnitudes fainter than in previous work. The derived distances have uncertainties of 5%–12% depending on the properties of the individual galaxies, and our sample is more than 3 times larger than any previous SBF study of this region. Virgo has a famously complex structure with numerous subclusters, clouds, and groups; we associate individual galaxies with the various substructures and map their three-dimensional spatial distribution. Curiously, subcluster A, centered around M87, appears to have two peaks in distance: the main peak at ∼16.5 Mpc, and a smaller one at ∼19.4 Mpc. Subclusters B and C have distances of ∼15.8 Mpc. The W and W ′ groups form a filament-like structure, extending more than 15 Mpc behind the cluster with a commensurate velocity increase of ∼1000 km s−1 along its length. These measurements are a valuable resource for future studies of the relationship between galaxy properties and local environment within a dynamic and evolving region.

A Survey for High-redshift Gravitationally Lensed Quasars and Close Quasar Pairs. I. The Discoveries of an Intermediately Lensed Quasar and a Kiloparsec-scale Quasar Pair at z ∼ 5

We present the first results from a new survey for high-redshift (z ≳ 5) gravitationally lensed quasars and close quasar pairs. We carry out candidate selection based on the colors and shapes of objects in public imaging surveys, then conduct follow-up observations to confirm the nature of high-priority candidates. In this paper, we report the discoveries of J0025–0145 (z = 5.07), which we identify as an intermediately lensed quasar, and J2329–0522 (z = 4.85), which is a kiloparsec-scale close quasar pair. The Hubble Space Telescope (HST) image of J0025–0145 shows a foreground lensing galaxy located 0.″6 away from the quasar. However, J0025–0145 does not exhibit multiple lensed images of the quasar, and we identify J0025–0145 as an intermediate lensing system (a lensing system that is not multiply imaged but has a significant magnification). The spectrum of J0025–0145 implies an extreme Eddington ratio if the quasar luminosity is intrinsic, which could be explained by a large lensing magnification. The HST image of J0025–0145 also indicates a tentative detection of the quasar host galaxy in the rest-frame UV, illustrating the power of lensing magnification and distortion in studies of high-redshift quasar host galaxies. Object J2329–0522 consists of two resolved components with significantly different spectral properties and a lack of lensing galaxy detection under subarcsecond seeing. We identify it as a close quasar pair, which is the highest confirmed kiloparsec-scale quasar pair to date. We also report four lensed quasars and quasar pairs at 2 < z < 4 and discuss possible improvements to our survey strategy.

RCSLenS: The Red Cluster Sequence Lensing Survey

We present the Red-sequence Cluster Lensing Survey (RCSLenS), an application of the methods developed for the Canada France Hawaii Telescope Lensing Survey (CFHTLenS) to the ~785deg$^2$, multi-band imaging data of the Red-sequence Cluster Survey 2 (RCS2). This project represents the largest public, sub-arcsecond seeing, multi-band survey to date that is suited for weak gravitational lensing measurements. With a careful assessment of systematic errors in shape measurements and photometric redshifts we extend the use of this data set to allow cross-correlation analyses between weak lensing observables and other data sets. We describe the imaging data, the data reduction, masking, multi-colour photometry, photometric redshifts, shape measurements, tests for systematic errors, and a blinding scheme to allow for more objective measurements. In total we analyse 761 pointings with r-band coverage, which constitutes our lensing sample. Residual large-scale B-mode systematics prevent the use of this shear catalogue for cosmic shear science. The effective number density of lensing sources over an unmasked area of 571.7deg$^2$ and down to a magnitude limit of r~24.5 is 8.1 galaxies per arcmin$^2$ (weighted: 5.5 arcmin$^{-2}$) distributed over 14 patches on the sky. Photometric redshifts based on 4-band griz data are available for 513 pointings covering an unmasked area of 383.5 deg$^2$ We present weak lensing mass reconstructions of some example clusters as well as the full survey representing the largest areas that have been mapped in this way. All our data products are publicly available through CADC at http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/en/community/rcslens/query.html in a format very similar to the CFHTLenS data release.

THE COMPACT STAR-FORMING COMPLEX AT THE HEART OF NGC 253* † ‡

ABSTRACT We discuss integral field spectra of the compact star-forming complex that is the brightest near-infrared (NIR) source in the central regions of the starburst galaxy NGC 253. The spectra cover the H and K passbands and were recorded with the Gemini NIR Spectrograph during subarcsecond seeing conditions. Absorption features in the spectrum of the star-forming complex are weaker than in the surroundings. An absorption feature is found near 1.78 μm that coincides with the location of a C2 bandhead. If this feature is due to C2 then the star-forming complex has been in place for at least a few hundred Myr. Emission lines of Brγ, [Fe ii], and He i 2.06 μm do not track the NIR continuum light. Pockets of star-forming activity that do not have associated concentrations of red supergiants, and so likely have ages &lt;8 Myr, are found along the western edge of the complex, and there is evidence that one such pocket contains a rich population of Wolf–Rayet stars. Unless the star-forming complex is significantly more metal-poor than the surroundings, then a significant fraction of its total mass is in stars with ages &lt;8 Myr. If the present-day star formation rate is maintained then the timescale to double its stellar mass ranges from a few Myr to a few tens of Myr, depending on the contribution made by stars older than ∼8 Myr. If—as suggested by some studies—the star-forming complex is centered on the galaxy’s nucleus, which presumably contains a large population of old and intermediate-age stars, then the nucleus of NGC 253 is currently experiencing a phase of rapid growth in its stellar mass.

ULASJ1234+0907: the reddest type 1 quasar at z = 2.5 revealed in the X-ray and far-infrared

Abstract We present Herschel and XMM–Newton observations of ULASJ1234+0907 (z = 2.503), the reddest broad-line type 1 quasar currently known with (i − K)AB &amp;gt; 7.1. Herschel observations indicate that the quasar host is a hyperluminous infrared galaxy with a total infrared luminosity of log10(LIR/L⊙) = 13.90 ± 0.02. A greybody fit gives a dust temperature of Td = 60 ± 3 K assuming an emissivity index of β = 1.5, considerably higher than in submillimeter bright galaxies observed at similar redshifts. The star formation rate is estimated to be &amp;gt;2000 M⊙ yr−1 even accounting for a significant contribution from an active galactic nucleus (AGN) component to the total infrared luminosity or requiring that only the far-infrared luminosity is powered by a starburst. XMM–Newton observations constrain the hard X-ray luminosity to be L2-10 keV = 1.3 × 1045 erg s−1, putting ULASJ1234+0907 among the brightest X-ray quasars known. Through very deep optical and near-infrared imaging of the field at subarcsecond seeing, we demonstrate that despite its extreme luminosity, it is highly unlikely that ULASJ1234+0907 is being lensed. We measure a neutral hydrogen column density of NH = 9.0 × 1021 cm−2 corresponding to AV ∼ 6. The observed properties of ULASJ1234+0907 – high luminosity and Eddington ratio, broad lines, moderate column densities and significant infrared emission from reprocessed dust – are similar to those predicted by galaxy formation simulations for the AGN blowout phase. The high Eddington ratio, combined with the presence of significant amounts of dust, is expected to drive strong outflows due to the effects of radiation pressure on dust.

UltraVISTA: a new ultra-deep near-infrared survey in COSMOS

In this paper we describe the first data release of the UltraVISTA near-infrared imaging survey of the COSMOS field. We summarise the key goals and design of the survey and provide a detailed description of our data reduction techniques . We provide stacked, sky-subtracted images in $YJHK_{\rm s}$ and narrow-band filters constructed from data collected during the first year of UltraVISTA observations. Our stacked images reach $5\sigma$ $AB$ depths in an aperture of $2\arcsec$ diameter of $\sim 25$ in $Y$ and $\sim 24$ in $JHK_{\rm s}$ bands and all have sub-arcsecond seeing. To this $5\sigma$ limit, our $K_{\rm s}$ catalogue contains 216,268 sources. We carry out a series of quality assessment tests on our images and catalogues, comparing our stacks with existing catalogues. The $1\sigma$ astrometric RMS in both directions for stars selected with $17.0<K_{\rm s}\rm {(AB)} <19.5$ is $\sim 0.08\arcsec$ in comparison to the publicly-available COSMOS ACS catalogues. Our images are resampled to the same pixel scale and tangent point as the publicly available COSMOS data and so may be easily used to generate multi-colour catalogues using this data. All images and catalogues presented in this paper are publicly available through ESO's "phase 3" archiving and distribution system and from the UltraVISTA web site.

Atmospheric scintillation at Dome C, Antarctica

Dome C, Antarctica is one of the most promising astronomical sites in the world (Fossat &amp; Candidi 2003, and references therein). Dome C boasts low wind speeds, very cold temperatures and little precipitation. The atmospheric turbulence is very weak compared to temperate sites, leading to sub-arcsecond seeing conditions (Lawrence et al. 2004; Agabi et al. 2006).

Observing Conditions at Mount Graham: Vatican Advanced Technology Telescope UBVR Sky Surface Brightness and Seeing Measurements from 1999 through 2003

ABSTRACTWe present measurements of sky surface brightness and seeing on Mount Graham, obtained at the Vatican Advanced Technology Telescope (VATT) during 16 observing runs between 1999 April and 2003 December. We show that the sky surface brightness is significantly darker during photometric conditions and can be highly variable over the course of a single observing run, as well as from one run to the next, regardless of photometricity. In our photometric observations, we find an average low air mass (sec z<1.2) sky surface brightness of 22.00, 22.53, 21.49, and 20.88 mag arcsec−2 in U, B, V, and R, respectively. The darkest run (2000 February in U and 2001 February in BVR) had an average sky surface brightness of 22.38, 22.86, 21.72, and 21.19 mag arcsec−2 in U, B, V, and R, respectively. With these results, we show that under the best conditions, Mount Graham can compete with the darkest sites in Hawaii and Chile, thanks in part to the strict dark‐sky ordinances in place in Tucson and Safford. We expect the sky over Mount Graham to be even darker than our 1999–2003 results during solar minimum (2006–2007). We find a significant improvement of about 0 .″45 in our measured stellar FWHM after improvements to the telescope were made in summer and fall 2001. Stellar FWHM values are highly variable, with median R‐band focus FWHM values in each observing run ranging from 0 .″97 to 2 .″15. Significant subarcsecond seeing was occasionally achieved, with values as low as 0 .″65 FWHM in R. There may still be a significant telescope contribution to the seeing at the VATT, but nearby trees as high as the dome are currently the dominant factor.

GaBoDS: The Garching-Bonn Deep Survey

The Garching-Bonn Deep Survey (GaBoDS) is a virtual 12 square degree cosmic shear and cluster lensing survey, conducted with the WFI@2.2m MPG/ESO telescope at La Silla. It consists of shallow, medium and deep random fields taken in R-band in subarcsecond seeing conditions at high galactic latitude. A substantial amount of the data was taken from the ESO archive, by means of a dedicated ASTROVIRTEL program. In the present work we describe the main characteristics and scientific goals of GaBoDS. Our strategy for mining the ESO data archive is introduced, and we comment on the Wide Field Imager data reduction as well. In the second half of the paper we report on clusters of galaxies found in the background of NGC 300, a random archival field. We use weak gravitational lensing and the red cluster sequence method for the selection of these objects. Two of the clusters found were previously known and already confirmed by spectroscopy. Based on the available data we show that there is significant evidence for substructure in one of the clusters, and an increasing fraction of blue galaxies towards larger cluster radii. Two other mass peaks detected by our weak lensing technique coincide with red clumps of galaxies. We estimate their redshifts and masses.

Optical Seeing at Sierra Negra

ABSTRACTOptical seeing measurements carried out at Sierra Negra, the site of the Large Millimeter Telescope, are reported. The site, one of the highest peaks in central Mexico, offers good coverage of the northern and southern hemispheres, and we have undertaken several campaigns to investigate the astronomical potential of the site in the optical. Here we report on our campaign to establish the seeing quality of the site. We present data from the first three campaigns of optical seeing monitoring covering 2000 February to 2002 May, carried out with a Differential Image Motion Monitor. The results clearly indicate subarcsecond seeing, better statistics during the dry season, and no dependence on the time of night. We find no dependence of our results on the integration time used.

The CFHT Open Star Cluster Survey. I. Cluster Selection and Data Reduction

We present this paper in conjuction with the following as the first results in the CFHT Open Star Cluster Survey. This survey is a large BVR imaging data set of 19 open star clusters in our Galaxy. This data set was taken with the CFH12K mosaic CCD (42' X 28') and the majority of the clusters were imaged under excellent photometric, sub-arcsecond seeing conditions. The combination of multiple exposures extending to deep (V ~ 25) magnitudes with short (< 10 second) frames allows for many different studies. The primary aim of this survey is to catalogue the white dwarf stars in these clusters and establish observational constraints on the initial-final mass relationship for these stars and the upper mass limit to white dwarf production. Additionally, we hope to better determine the properties of the clusters, such as age and distance, and also test evolution and dynamical theories by analyzing luminosity and mass functions. In order to more easily incorporate this data in further studies, we have produced a catalogue of positions, magnitudes, colors, and stellarity confidence for all stars in each cluster of the survey. This paper is intended both as a source for the astronomical community to obtain information on the clusters in the survey and as a detailed reference of reduction procedures for further publications of individual clusters. We discuss the methods employed to reduce the data and compute the photometric catalogue. The scientific results for each individual cluster and global results from the study of the entire survey will be presented in further publications (results for the rich old open cluster NGC 6819 immediately follow this paper).

High‐Ionization Clouds in the Circumnuclear Region of M31

We present two-dimensional spectroscopy of the 125 × 125 pc2 circumnuclear region of M31, obtained using two optical fiber systems, INTEGRAL and 2D-FIS, installed at the 4.2 m William Herschel Telescope at the Roque de los Muchachos Observatory on the island of La Palma, Spain. We present continuum and emission-line maps, emission-line quotients, and stellar and ionized gas velocity fields obtained under subarcsecond seeing conditions. We have discovered Hβ, [O III] λλ4959, 5007, Hα, and [N II] λλ6548, 6584 emission in the inner 40 × 40 pc2 circumnuclear region. The intensity maps obtained from the emission lines show several isolated systems of ionized gas (clouds) a few parsecs in size. The kinematics of the clouds is decoupled from the stellar rotation, and strong radial motions are likely to be present. We have also discussed the ionization mechanisms present in the clouds. Although the emission-line quotients are compatible with ionization produced by post-asymptotic giant branch stars, the estimated ionization fluxes exceed what is expected according to the distribution of planetary nebulae in the bulge of M31. Comparison of the line quotients and spectra found in M31 with those found in the extended narrow-line region of the Seyfert galaxy NGC 4151 indicates that we could be in presence of ultralow-intensity nuclear activity. These results would be compatible with the existence of a dead quasar in the nucleus of M31 and underline the hybrid character of the LINER phenomenon.

CTQ 414: A New Gravitational Lens

We report the discovery and ground-based observations of the new gravitational lens CTQ 414. The source quasar lies at a redshift of z = 1.29 with a B magnitude of 17.6. Ground-based optical imaging reveals two point sources separated by 12 with a magnitude difference of roughly 1 mag. Subtraction of two stellar point-spread functions from images obtained in subarcsecond seeing consistently leaves behind a faint, residual object. Fits for two point sources plus an extended object places the fainter object collinear with the two brighter components. Subsequent Hubble Space Telescope Near Infrared Camera and Multi-Object Spectrometer (NICMOS) observations have confirmed the identification of the fainter object as the lensing galaxy. Very Large Array observations at 8.46 GHz reveal that all components of the lensing system are radio-quiet down to the 0.2 mJy flux level.

Optical morphology of distant RATAN-600 radio galaxies from subarcsecond resolution NOT images

We present direct imaging data of 22 ultra steep spectrum radio sources obtained at (or near) a subarcsecond seeing. The basic sample of 40 double ra- dio sources was selected from the RATAN-600 catalogue. The FRII-structure has been conrmed with VLA and preliminary optical identications which come from the 6 m-telescope. As the RATAN-600 flux limit at 3.9 GHz ( 10 mJy) is fainter than that of major surveys, the sam- ple may have high-z contents. This is also suggested by the faint magnitudes in the Hubble diagram. The nal aim is to create a homogeneous sample of high-z radio galaxies in a well dened strip around the sky, with faint radio limit and subarcsecond morphology down to mR = 24. We could conrm 16 identications down to mR 24. Most of the extended objects have multicomponent struc- tures as expected from other surveys of high-redshift ra- dio galaxies. We found ve unresolved objects even with a subarcsecond seeing. Of the remaining six objects, three are extremely faint and the other three have such a com- plex environment that further observations are needed to conrm the optical identication.

Two-dimensional Spectroscopy Reveals an Arc of Extended Emission in the Gravitational Lens System Q2237+0305

We present two-dimensional spectroscopy of the gravitational lens system Q2237+0305 (Einstein Cross) obtained with the INTEGRAL fiber system in subarcsecond seeing conditions. The four components of the system appear clearly separated in the continuum intensity maps. However, the intensity map of the C III] λ1909 line exhibits an arc of extended emission connecting the A, D, and B components. This result can be explained if, as is usually assumed, the continuum arises from a compact source ≲0.05 pc in extent in the nucleus of the object while the line emission comes from a much larger region. A lens model fitted to the positions of the four compact images also accounts for the arc morphology. In the framework of this model, the region generating the C III] λ1909 emission would have dimensions of about 400 h-1 pc across. We interpret the observed arc as a gravitational lens image of the extended narrow line region of the source.

The First FIRST Gravitationally Lensed Quasar: FBQ 0951+2635

The V=16.9 quasar FBQ 0951+2635 at redshift z=1.24 appears double on CCD exposures taken in subarcsecond seeing. The two objects are separated by 1.1 and differ in brightness by 0.9 mag. VLA observations show the radio source to be double with the same separation and position angle. Spectra taken with the Keck II telescope show the two components to have nearly identical emission line spectra, but with somewhat different absorption line systems. Subtraction of two stellar point spread functions from the pair of components consistently leaves a residual object. Depending upon whether this third object is extended or a point source it may be as much as 1/10 or as little as 1/100 as bright as the brighter QSO component. The observations leave no doubt that the 2 brighter objects are gravitationally lensed images of the same quasar. The third object might be either the lensing galaxy or a third image of the quasar, but both interpretations have serious shortcomings.

Measuring the Angular Correlation Function for Faint Galaxies in High Galactic Latitude Fields

The angular correlation function (ω(θ)) for faint, magnitude-limited samples is an important test of large scale structure formation scenarios, as well as being a valuable probe of galaxy evolution. By measuring ω(θ) one hopes to better understand the mechanism or galaxy species responsible for the number counts excess (relative to “no-evolution” models of galaxies) typically observed at blue wavelengths. Images of three ‘blank’ fields were obtained at the prime focus of the CFHT with sub-arcsecond seeing in V, R and I, to magnitude limits of 25, 24.5 and 24, respectively. The angular correlation functions calculated for one field, NF1, in V is shown in Figure 1. Clearly the amplitude of ω(θ) is decreasing at fainter magnitude limits. Note the number of objects detected are not sufficient to accurately measure ω(θ) for an individual field, in a given colour, to significantly small angular separations. In order to do this we must combine the data from our three fields and perform a multi-field fit. A full summary of this analysis will be presented in Woods et al. (1995, in prep.) including determinations of ω(θ) using galaxy samples culled from all our fields and selected by magnitude, colour and surface brightness.

The Close Environment of OJ 287: Underlying Nebulosity and a Possible Optical Jet?

We present a deep V-band image of the BL Lac object OJ 287 and its close environment. Twenty-nine V images taken on 1994 January 18-21, when OJ 287 was at a low brightness level, were combined to obtain an image with a total integration time of 4.83 hr. The final image was processed using nonlinear restoration techniques (Lucy). The presence of a nebulosity surrounding OJ 287 can be distinctly seen for the first time in the deep image presented here. Comparing this image with radio maps obtained by Kollgaard et al. and Perlman & Stocke, we found that there is a coincidence between a faint optical elongation in the underlying nebulosity to the west of OJ 287 and the radio tail. Within 30'' of OJ 287, we can see several other interesting nearby features, such as three nearby companions at 34, 6'', and 10'' projected distance, with colors of distant galaxies, and another elongation which seems to emerge from OJ 287 followed by an alignment of at least four features along a position angle of 220°. We discuss the possibility of this structure (or part of it) consisting of knots that form an optical jet. We also have B, R, I, and K images taken a posteriori at other sites, some obtained under subarcsecond seeing, which were used to determine the magnitudes and colors of some of the most relevant features surrounding OJ 287.

Deep Infrared Array Imaging of Globular Clusters. IV. M22 (NGC 6656)

view Abstract Citations (13) References (49) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Deep Infrared Array Imaging of Globular Clusters. IV. M22 (NGC 6656) Davidge, T. J. ; Harris, W. E. Abstract Moderately deep J and K' images, recorded during subarcsecond seeing conditions, are used to investigate the near-infrared color-magnitude diagram (CMD) of the heavily reddened metal-poor globular cluster M22 (NGC 6656). The CMD constructed from these data extends from K = 7 to K = 18, and includes the upper portions of the main sequence. The main-sequence turnoff (MSTO) occurs at K = 15.1 and J - K = 0.41 values that are well matched by metal-poor 12 Gyr isochrones from Bergbusch & VandenBerg and Straniero & Chieffi after adopting canonical values for the cluster distance and reddening. For comparison, 16 Gyr isochrones are unable to match the brightness and color of the MSTO, although we emphasize that uncertainties in our current knowledge of stellar structure and evolution make any estimate of absolute ages tentative. We also compare the M22 CMD with that obtained for M13 by Davidge & Harris. After correcting for differences in distance, reddening, and [Fe/H], we find that the brightnesses of the subgiant branch (SGB) and MSTO in M22 and M13 are not significantly different. However, the M22 giant branch is steeper than that in M13, a finding contrary to the relative metallicities of these clusters, but consistent with earlier optical observations by Hesser, Hart- wick, & McClure. In particular, the lower giant branch of M22 falls blueward of M13, although the upper giant branches coincide. We suggest that the overall giant branch slope at near-infrared wavelengths may be sensitive to parameters other than age and [Fe/H]. Finally, we investigate the mass function of stars with masses between 0.5 and 0.8 Msun. The data are consistent with a relatively flat mass function above 0.6 Msun, a result broadly consistent with what would be predicted based on the mean metallicity and location of M22 in the Galaxy. Publication: The Astrophysical Journal Pub Date: May 1996 DOI: 10.1086/177146 Bibcode: 1996ApJ...462..255D Keywords: GALAXY: GLOBULAR CLUSTERS: INDIVIDUAL MESSIER NUMBER: M22; INFRARED: STARS; STARS: EVOLUTION; STARS: LUMINOSITY FUNCTION; MASS FUNCTION full text sources ADS | data products SIMBAD (2) Related Materials (6) Part 1: 1994ApJ...423..640D Part 2: 1994ApJ...435..207D Part 3: 1995ApJ...445..211D Part 4: 1995ApJ...454..545D Part 6: 1996ApJ...468..641D Part 7: 1997ApJ...475..584D

Measuring the Angular Correlation Function for Faint Galaxies at High Galactic Latitudes

The angular correlation function (ω(θ)) for faint, magnitude-limited samples is an important test of large scale structure formation scenarios, as well as being a valuable probe of galaxy evolution. By measuring ω(θ) one hopes to better understand the mechanism or galaxy species responsible for the number counts excess (relative to “no-evolution” models of galaxies) typically observed at blue wavelengths. Images of three ‘blank’ fields were obtained at the prime focus of the CFHT with sub-arcsecond seeing in V, R and I, to magnitude limits of 25, 24.5 and 24, respectively. The angular correlation functions calculated for one field, NF1, in V is shown in Figure 1. Clearly the amplitude of ω(θ) is decreasing at fainter magnitude limits. Note the number of objects detected are not sufficient to accurately measure ω(θ) for an individual field, in a given colour, to significantly small angular separations. In order to do this we must combine the data from our three fields and perform a multi-field fit. A full summary of this analysis will be presented in Woods et al. (1995, in prep.) including determinations of ω(θ) using galaxy samples culled from all our fields and selected by magnitude, colour and surface brightness.