H. T. MacGillivray

The SuperCOSMOS Sky Survey – I. Introduction and description

In this, the first in a series of three papers concerning the SuperCOSMOS Sky Survey (SSS), we give an introduction and user guide to the survey programme. We briefly describe other wide-field surveys and compare them with our own. We give examples of the data, and make a comparison of the accuracies of the various image parameters available with those from the other surveys providing similar data; we show that the SSS data base and interface offer advantages over these surveys. Some science applications of the data are also described and some limitations discussed. The series of three papers constitutes a comprehensive description and user guide for the SSS.

The AAO/UKST SuperCOSMOS Hα survey

The UK Schmidt Telescope (UKST) of the Anglo-Australian Observatory completed a narrowband Ha plus [N II] 6548, 6584-A survey of the Southern Galactic Plane and Magellanic Clouds in late 2003. The survey, which was the last UKST wide-field photographic survey and the only one undertaken in a narrow-band, is now an online digital data product of the Wide-Field Astronomy Unit of the Royal Observatory Edinburgh (ROE). The survey utilized a high specification, monolithic Hα interference bandpass filter of exceptional quality. In conjunction with the fine-grained Tech-Pan film as a detector it has produced a survey with a powerful combination of area coverage (4000 square degrees), resolution (∼1 arcsec) and sensitivity (≤5 Rayleighs), reaching a depth for continuum point sources of R ≃ 20.5. The main survey consists of 233 individual fields on a grid of centres separated by 4° at declinations below +2° and covers a swathe approximately 20° wide about the Southern Galactic Plane. The original survey films were scanned by the SuperCOSMOS measuring machine at the Royal Observatory, Edinburgh, to provide the online digital atlas called the SuperCOSMOS Ha Survey (SHS). We present the background of the survey, the key survey characteristics, details and examples of the data product, calibration process, comparison with other surveys and a brief description of its potential for scientific exploitation.

The ROSAT-ESO flux limited X-ray (REFLEX) galaxy cluster survey. I. The construction of the cluster sample ?

We discuss the construction of an X-ray flux-limited sample of galaxy clusters, the REFLEX survey catalogue, to be used for cosmological studies. This cluster identication and redshift survey was conducted in the frame of an ESO key programme and is based on candidates selected from the southern part of the ROSAT All-Sky Survey (RASS). For the rst cluster candidate selection from a flux-limited RASS source list, we make use of optical data from the COSMOS digital catalogue produced from the scans of the UK-Schmidt plates. To ensure homogeneity of the sample construction process, this selection is based only on this one well-dened optical data base. The nature of the candidates selected in this process is subsequently checked by a more detailed evaluation of the X-ray and optical source properties and available literature data. The nal identication and the redshift is then based on optical spectroscopic follow-up observations. In this paper we document the process by which the primary cluster candidate catalogue is constructed prior to the optical follow-up observations. We describe the reanalysis of the RASS source catalogue which enables us to impose a proper flux limit cut to the X-ray source list without introducing a severe bias against extended sources. We discuss the correlation of the X-ray and optical (COSMOS) data to nd galaxy density enhancements at the RASS X-ray source positions and the further evaluation of the nature of these cluster candidates. Based also on the results of the follow-up observations we provide a statistical analysis of the completeness and contamination of the nal cluster sample and show results on the cluster number counts. The nal sample of identied X-ray clusters reaches a flux limit of 3 10 12 erg s 1 cm 2 in the 0.1{2.4 keV band and comprises 452 clusters in an area of 4.24 ster. The results imply a completeness of the REFLEX cluster sample well in excess of 90%. We also derive for the rst time an upper limit of less than 9% for the number of clusters which may feature a dominant contribution to the X-ray emission from AGN. This accuracy is sucient for the use of this cluster sample for cosmological tests.

The ROSAT-ESO Flux-Limited X-ray (REFLEX) galaxy cluster survey — II. The spatial correlation function

We report the results of the spatial two-point correlation functioncc(r) for the new X- ray galaxy cluster survey REFLEX, which comprises of 452 X-ray selected clusters (449 with redshifts) detected by the ROSAT satellite during the ROSAT All-Sky-Survey (RASS). The REFLEX cluster sample is flux limited to 3 × 10 12 erg s 1 cm 2 in the ROSAT energy band (0.1 − 2.4 keV) and spans 3 decades in X-ray luminosity (10 42 −10 45 h 2 erg s 1 ), containing galaxy groups and rich clusters out to a redshift z ≤ 0.3. Covering a contiguous area of 4.24 sr REFLEX is the largest X-ray cluster sample to date for which spatial clustering has been analysed. Correlation studies using clusters selected on the basis of their X-ray emission are particularly interesting as they are largely free from the projection biases inherent to optical studies. For the entire flux-limited sample we find that the correlation length (the scale at which the correlation amplitude passes through unity) r0 ≃ 20h 1 Mpc. For example, if a power-law fit is made to �(r) over the range 4 − 40h 1 Mpc then r0 = 18.8 ± 0.9. An indication of the robustness of this result comes from the high degree of isotropy seen in the clustering pattern on scales close to the correlation length. On larger scalescc(r) deviates from a power-law, crossing zero at ≃ 45h 1 Mpc. From an examination of 5 volume-limited cluster sub-samples we find no significant trend of r0 with limiting X-ray luminosity. A comparison with recent model predictions for the clustering properties of X-ray flux-limited samples, indicates that Cold Dark Matter models with the matter density m = 1 fail to produce sufficient clustering to account for the data, while m ≃ 0.3 models provide an excellent fit.

A study of the core of the Shapley Concentration – I. The sample

We report the first results of a spectroscopic survey of galaxies in the core of the Shapley Concentration, the richest nearby supercluster of clusters of galaxies. We have measured 311 new galaxy redshifts in an area of ∼4.5 deg 2 centred on the Abell cluster A3558. When the data already available in the literature are also considered, the total number of galaxy redshifts in this area amounts to more than 500. On the basis of these data, we estimate the mean velocities and the velocity dispersions of the Abell clusters A3556 and A3558 and the poor cluster SC 1329-314

The DA+dMe eclipsing binary EC13471–1258: its cup runneth over … just

The optical spectrum and light curve of EC13471-1258 show that it is an eclipsing binary with an orbital period of 3 h 37 m comprising a DA white dwarf and a dMe dwarf. Total eclipses of the white dwarf are observed lasting 14 min, with the partial phases lasting 54 s. On one occasion, two pre-eclipse dips were seen. Timings of the eclipses over 10 yr show jitter of up to 12 s. Flares from the M dwarf are regularly observed. The M dwarf also shows a large-amplitude ellipsoidal modulation in the V-band light curve. The component stars emit almost equal amounts of light at 5500 A. Hubble Space Telescope (HST) STIS spectra show strong Lyman-a absorption with weak metal lines of C I,II and Si II superimposed. Model atmosphere analysis yielded an effective temperature of 14 220 ′ 300 K and log g of 8.34 ′ 0.20 for the white dwarf with these errors being strongly correlated. Its metal abundance is 1/30th solar with an uncertainty of 0.5 dex, and it is rapidly rotating with V 1 sin i = 400 ′ 100 km s - 1 . The white dwarf also shows radial velocity variations with a semi-amplitude of 138 ′ 10 km s - 1 . The gravitational redshift of the white dwarf was measured as 62 km s - 1 . From optical spectroscopy the spectral type of the M dwarf was found to be M3.5-M4, its temperature 3100 ′ 75 K, its rotational velocity 140 ′ 10 km s - 1 , its radial velocity semi-amplitude 266 ′ 5 km s - 1 , its mean V - I colour 2.86 and its absolute V magnitude 11.82. Intriguingly, its metal abundance is normal solar. The Ha emission line shows at least two distinct components, one of which is uniformly distributed around the centre of mass of the M dwarf and provided the estimate of the rotational velocity of the M dwarf. The other arises from the other side of the binary centre of mass, well within the white dwarf Roche lobe. This behaviour is confirmed by Doppler tomography, which shows the presence of two distinct velocity components within the primary Roche lobe. The interpretation of these features is uncertain. Variations in strength of the components with binary phase can be attributed to optical thickness in the Balmer lines. Similar behaviour is seen in the observations of the other Balmer emission lines, although with a poorer signal-to-noise ratio. Flares in Ha were observed and are consistent with arising from the vicinity of the M dwarf. Dynamical solutions for the binary are discussed and yield an inclination of 75.5° ′ 2.0°, a white dwarf mass and radius of 0.78 ′ 0.04 M O . and 0.011 ′ 0.01 R O ., and an M dwarf mass and radius of 0.43 ′ 0.04 M O . and 0.42 ′ 0.02 R O .. These parameters are consistent with the Wood mass-radius relation for white dwarfs and the Clemens et al. mass-radius relation for M dwarfs; we argue that the M dwarf just fills its Roche lobe. The radius of the white dwarf and the model fit imply a distance of 48 ′ 5 pc and an absolute V magnitude of 11.74. The rapid rotation of the white dwarf strongly suggests that the system has undergone mass transfer in the past, and implies that it is a hibernating cataclysmic variable. The M dwarf shows the properties expected of secondaries in cataclysmic variables: chromospheric activity and angular momentum loss.

The ROSAT All-Sky Survey: a Catalog of Clusters of Galaxies in a Region of 1 steradian around the South Galactic Pole

A field of 1.013 sr in the ROSAT All-Sky Survey (RASS), centered on the south Galactic pole (SGP), has been searched in a systematic, objective manner for clusters of galaxies. The procedure relied on a correlation of the X-ray positions and properties of ROSAT sources in the field with the distribution of galaxies in the COSMOS digitized database, which was obtained from scanning the plates of the UK Schmidt IIIa-J optical survey of the southern sky. The study used the second ROSAT survey database (RASS-2) and included several optical observing campaigns to measure cluster redshifts. The search, which is a precursor to the larger REFLEX survey encompassing the whole southern sky, reached the detection limits of both the RASS and the COSMOS data and yielded a catalog of 186 clusters in which the lowest flux is 1:5 � 10 � 12 ergs cm � 2 s � 1 in the 0.1–2.4 keV band. Of these 157 have measured redshifts. Using a flux limit of 3:0 � 10 � 12 ergs cm � 2 s � 1 a complete subset of 112 clusters was obtained, of which 110 have measured redshifts. The spatial distribution of the X-ray clusters out to a redshift of 0.15 shows an extension of the Local Supercluster to the Pisces-Cetus supercluster ðz <� 0:07Þ, and an orthogonal structure at higher redshift ð0:07 < z < 0:15Þ. This result is consistent with large-scale structure suggested by optical surveys. Subject headings: catalogs — galaxies: clusters: general — X-rays: galaxies: clusters On-line material: machine-readable table

The ESO Slice Project (ESP) galaxy redshift survey - III. The sample

The ESO Slice Project (ESP) is a galaxy redshift survey we have recently completed as an ESO Key-Project. The ESP covers 23.3 square degrees in a region close to the South Galactic Pole. The survey is nearly complete (85%) to the limiting magnitude b_J=19.4 and consists of 3342 galaxies with reliable redshift determination. In this paper, the first in a series that will present the results of the ESP survey, we describe the main characteristics of the survey and briefly discuss the properties of the galaxy sample. From a preliminary spectral analysis of a large sub-sample of 2550 galaxies we find that the fraction of actively star-forming galaxies increases from a few percent for the brightest galaxies up to about 40% for the galaxies fainter than M= -16.5. The most outstanding feature in the ESP redshift distribution is a very significant peak at z ~ 0.1. The detection of similar peaks, at the same distance, in other surveys in the same region of the sky, suggests the presence of a large bidimensional structure perpendicular to the line of sight. The minimum size of this structure would be of the order of 100 x 50 Mpc, comparable with the size of the Great Wall.The ESO Slice Project (ESP) is a galaxy redshift survey extending over about 23 square degrees, in a region near the South Galactic Pole. The survey is ~85% complete to the limiting magnitude b_J=19.4 and consists of 3342 galaxies with redshift determination. The ESP survey is intermediate between shallow, wide angle samples and very deep, one-dimensional pencil beams; the spanned volume is ~ 5 x 10^4 Mpc^3 at the sensitivity peak (z ~ 0.1). In this paper we present the description of the observations and of the data reduction, the ESP redshift catalogue and the analysis of the quality of the velocity determinations.

The SuperCOSMOS all-sky galaxy catalogue

We describe the construction of an all-sky galaxy catalogue, using SuperCOSMOS scans of Schmidt photographic plates from theUKSchmidt Telescope and Second Palomar Observatory Sky Survey. The photographic photometry is calibrated using Sloan Digital Sky Survey data, with results that are linear to 2 per cent or better. All-sky photometric uniformity is achieved by matching plate overlaps and also by requiring homogeneity in optical-to-2MASS colours, yielding zero-points that are uniform to 0.03 mag or better. The typical AB depths achieved are BJ < 21, RF < 19.5 and IN < 18.5, with little difference between hemispheres. In practice, the IN plates are shallower than the BJ and RF plates, so for most purposes we advocate the use of a catalogue selected in these two latter bands. At high Galactic latitudes, this catalogue is approximately 90 per cent complete with 5 per cent stellar contamination; we quantify how the quality degrades towards the Galactic plane. At low latitudes, there are many spurious galaxy candidates resulting from stellar blends: these approximately match the surface density of true galaxies at |b| = 30°. Above this latitude, the catalogue limited in BJ and RF contains in total about 20 million galaxy candidates, of which 75 per cent are real. This contamination can be removed, and the sky coverage extended, by matching with additional data sets. This SuperCOSMOS catalogue has been matched with 2MASS and with WISE, yielding quasiall- sky samples of respectively 1.5 million and 18.5 million galaxies, to median redshifts of 0.08 and 0.20. This legacy data set thus continues to offer a valuable resource for large-angle cosmological investigations.

Erratum: ``The ROSAT All-Sky Survey: A Catalog of Clusters of Galaxies in a Region of 1 Steradian around the South Galactic Pole'' (ApJS, 140, 239 [2002])

There are errors in the count rates for 17 of the 186 clusters in the catalog (Table 3). The cause of the error, detected recently during comparison of the catalog with other data sources, was an infrequent software error not revealed during testing. We have reexamined all the data in Table 3 and verified that only the count rates of 17 clusters, and the derived values of temperature, energy flux, and luminosity, were affected. Further, we have recreated all the relevant figures and concluded that these errors had no significant effect on the findings and conclusions of the paper. The number of clusters in the complete sample with a flux limit of 3:0 10 12 ergs cm 2 s 1 in the 0.1–2.4 keV band is reduced from 112 to 110, of which 108 have redshifts. The table presented below is an extract from the print version of the catalog table (Table 3), in which we have corrected the X-ray count rate (col. [4]), temperature (col. [8]), energy flux (col. [9]), and luminosity (col. [10]) for these 17 clusters.