Medium Deep Survey Research Articles

The Top 10 List of Gravitational Lens Candidates from the [ITAL]HUBBLE SPACE TELESCOPE[/ITAL] Medium Deep Survey

A total of 10 good candidates for gravitational lensing have been discovered in the WFPC2 images from the Hubble Space Telescope (HST) Medium Deep Survey (MDS) and archival primary observations. These candidate lenses are unique HST discoveries, i.e., they are faint systems with subarcsecond separations between the lensing objects and the lensed source images. Most of them are difficult objects for ground-based spectroscopic confirmation or for measurement of the and source redshifts. Seven are strong lens candidates that appear to have multiple images of the source. Three are cases in which the single image of the source galaxy has been significantly distorted into an arc. The first two quadruply lensed candidates were reported by Ratnatunga et al. We report on the subsequent eight candidates and describe them with simple models based on the assumption of singular isothermal potentials. Residuals from the simple models for some of the candidates indicate that a more complex model for the potential will probably be required to explain the full structural detail of the observations once they are confirmed to be lenses. We also discuss the effective survey area that was searched for these candidate objects.

The properties of field elliptical galaxies at intermediate redshift -- I. Empirical scaling laws

We present measurements of the Fundamental Plane (FP) parameters (the effective radius, the mean effective surface brightness, and the central velocity dispersion) of six field elliptical galaxies at intermediate redshift. The imaging is taken from the Medium Deep Survey of the Hubble Space Telescope, while the kinematical data are obtained from long-slit spectroscopy using the 3.6-m ESO telescope. The Fundamental Plane appears well defined in the field even at redshift $\approx$ 0.3. The data show a shift in the FP zero point with respect to the local relation, possibly indicating modest evolution, consistent with the result found for intermediate redshift cluster samples. The FP slopes derived for our field data, plus other cluster ellipticals at intermediate redshift taken from the literature, differ from the local ones, but are still consistent with the interpretation of the FP as a result of homology, of the virial theorem and of the existence of a relation between luminosity and mass, $L \propto M^{\eta}$. We also derive the surface brightness vs. effective radius relation for nine galaxies with redshift up to $z \approx0.6$, and data from the literature; the evolution that can be inferred is consistent with what is found using the FP.

Compact Nuclei in Galaxies at Moderate Redshift. II. Their Nature and Implications for the Active Galactic Nucleus Luminosity Function

This study explores the space density and properties of active galaxies to z0.8. We have investigated the frequency and nature of unresolved nuclei in galaxies at moderate redshift as indicators of nuclear activity such as active galactic nuclei (AGNs) or starbursts. Candidates are selected by fitting imaged galaxies with multicomponent models using maximum-likelihood estimate techniques to determine the best model fit. We select those galaxies requiring unresolved point-source components in the galaxy nuclei, in addition to disk and/or bulge components, to adequately model the galaxies' light. We have searched 70 WFPC2 images, primarily from the Medium Deep Survey, for galaxies containing compact nuclei. In our survey of 1033 galaxies, the fraction containing unresolved nuclear components contributing ≥5% of the total galaxy light is 9%±1% corrected for incompleteness. In this second of two papers in this series, we discuss the nature of the compact nuclei and their hosts. We present the upper limit luminosity function (LF) for low-luminosity AGNs (LLAGNs) in two redshift bins to z=0.8. Mild number-density evolution of the form ∝(1+z)1.9 is detected for nuclei at -18MB-14. The LFs appear to flatten at MB≥-16 and this flatness, combined with the increase in number density, is inconsistent with pure luminosity evolution. Based on the amount of density evolution observed for these objects, we find that almost all present-day spiral galaxies could have hosted LLAGNs at some point in their lives. We also comment on the likely contribution of these compact nuclei to the soft X-ray background.

Compact Nuclei in Galaxies at Moderate Redshift. I. Imaging and Spectroscopy

This study explores the space density and properties of active galaxies to z=0.8. We have investigated the frequency and nature of unresolved nuclei in galaxies at moderate redshift as indicators of nuclear activity such as Active Galactic Nuclei (AGN) or starbursts. Candidates are selected by fitting imaged galaxies with multi-component models using maximum likelihood estimate techniques to determine the best model fit. We select those galaxies requiring an unresolved, point source component in the galaxy nucleus, in addition to a disk and/or bulge component, to adequately model the galaxy light. We have searched 70 WFPC2 images primarily from the Medium Deep Survey for galaxies containing compact nuclei. In our survey of 1033 galaxies, the fraction containing an unresolved nuclear component greater than 3% of the total galaxy light is 16+/-3% corrected for incompleteness and 9+/-1% for nuclei greater than 5% of the galaxy light. Spectroscopic redshifts have been obtained for 35 of our AGN/starburst candidates and photometric redshifts are estimated to an accuracy of sigma_z=0.1 for the remaining sample. In this paper, the first of two in this series, we present the selected HST imaged galaxies having unresolved nuclei and discuss the selection procedure. We also present the ground-based spectroscopy for these galaxies as well as the photometric redshifts estimated for those galaxies without spectra.

Hubble Sequence as a Temporal Evolution Sequence

The results from Hubble Space Telescope's Medium Deep Survey and Deep Fields indicate that there exists far more blue spiral galaxies at the intermediate and high redshifts than at the present epoch. A natural question therefore is: what have become of these excess late type galaxies as the Universe aged?

The [ITAL]Hubble[/ITAL] [ITAL]Space[/ITAL] [ITAL]Telescope[/ITAL] Medium Deep Survey Cluster Sample: Methodology and Data

We present a new, objectively selected, sample of galaxy overdensities detected in the Hubble Space Telescope Medium Deep Survey (MDS). These clusters/groups were found using an automated procedure that involved searching for statistically significant galaxy overdensities. The contrast of the clusters against the field galaxy population is increased when morphological data are used to search around bulge-dominated galaxies. In total, we present 92 overdensities above a probability threshold of 99.5%. We show, via extensive Monte Carlo simulations, that at least 60% of these overdensities are likely to be real clusters and groups and not random line-of-sight superpositions of galaxies. For each overdensity in the MDS cluster sample, we provide a richness and the average of the bulge-to-total ratio of galaxies within each system. This MDS cluster sample potentially contains some of the most distant clusters/groups ever detected, with about 25% of the overdensities having estimated redshifts z > ~0.9. We have made this sample publicly available to facilitate spectroscopic confirmation of these clusters and help more detailed studies of cluster and galaxy evolution. We also report the serendipitous discovery of a new cluster close on the sky to the rich optical cluster Cl l0016+16 at z = 0.546. This new overdensity, HST 001831+16208, may be coincident with both an X-ray source and a radio source. HST 001831+16208 is the third cluster/group discovered near to Cl 0016+16 and appears to strengthen the claims of Connolly et al. of superclustering at high redshift.

Segregated optical--near-infrared colour distributions of Medium Deep Survey galaxies

We present a K survey of 29 fields covering approximately 90 arcmin2 from the Medium Deep Survey (MDS) catalogue down to a completeness magnitude of K=18.0 (limiting magnitude K=19.0). The morphology obtained by the MDS team using high-resolution images from HST/WFPC2 along with our near-infrared (NIR) observations allows colour–magnitude and colour–colour analysis that agrees in general with spectral evolution models, especially if a reasonable range of metallicities for the simple stellar populations used (0.2 < Z/Z⊙ < 2.5) is considered. However, a significant population of spheroids was found, which appears bluer than expected, confirming previous observations. This blueness might possibly signal the existence of non-negligible star formation in ellipticals and bulges at medium redshift. A number counts calculation for different morphological types shows that discs become the dominant population at faint magnitudes. The median redshift of the sample is z ∼ 0.2, from a photometric redshift estimation using V-K and I-K. A search for Extremely Red Objects (EROs) in the survey field was also performed, with no detection of objects having I-K>4.5, setting an upper limit to the number density of EROs dnEROs/dΩ < 0.011 arcmin−2 (K ≤ 18.0).

Modelling the number counts of early-type galaxies by pure luminosity evolution

In this paper, we explore the plausible luminosity evolution of early-type galaxies in different cosmological models by constructing a set of pure luminosity evolution (PLE) models via the choices of the star formation rate (SFR) parameters and formation redshift $z_f$ of galaxies, with the observational constraints derived from the Hubble Space Telescope (HST) morphological number counts for elliptical and S0 galaxies of the Medium Deep Survey (MDS) and the Hubble Deep Field (HDF). We find that the number counts of early-type galaxies can be explained by the pure luminosity evolution models, without invoking exotic scenarios such as merging or introducing an additional population. But the evolution should be nearly passive, with a high $z_f$ assumed. The conclusion is valid in all of the three cosmological models we adopted in this paper. We also present the redshift distributions for three bins of observed magnitudes in F814w pass-band, to show at which redshift are the objects that dominate the counts at a given magnitude. The predictions of the redshift distribution of $22.5<b_j<24.0$ are also presented for comparison with future data.

Compact Nuclei in Galaxies at Moderate Redshift

The purpose of this study is to understand the space density and properties of active galaxies to . We have invesz 0.8 tigated the frequency and nature of unresolved nuclei in galaxies at moderate redshift as indicators of nuclear activity such as active galactic nuclei (AGNs) or starbursts. Candidates are selected by fitting imaged galaxies with multicomponent models using maximum likelihood estimate techniques to determine the best model fit. We select those galaxies requiring an unresolved, point source component in the galaxy nucleus, in addition to a disk and/or bulge component, to adequately model the galaxy light. We have searched 70 WFPC2 images primarily from the Medium Deep Survey for galaxies containing compact nuclei. In our survey of 1033 galaxies, the fraction containing an unresolved nuclear component ≥3% of the total galaxy light is corrected for incompleteness. Most of the nuclei 16% 3% comprise less than 20% of the total galaxy light. The majority of the host galaxies are spirals with little or no bulge component having a distribution of Hubble types comparable to that for “dwarf” Seyfert nuclei in nearby galaxies (L. C. Ho, A. Fillipenko, & W. L. W. Sargent, ApJS, 112, 315 [1997]) and local starburst nuclei (V. Balzano, ApJ, 268, 602 [1983]). The colors of the nuclei are compared with synthetic colors V I for Seyferts and starburst nuclei to help differentiate between AGNs and starbursts in our sample. Spectroscopic redshifts have been obtained for 35 of our AGN/starburst candidates and photometric redshifts are estimated to an accuracy of for the remaining sample. j 0.1 z Figure 1 is the luminosity function for compact nuclei in our sample having colors consistent with those of Seyfert nuclei. This represents an upper limit LF for low-luminosity AGNs (LLAGNs) in two redshift bins to . We detect z 0.8 mild number density evolution of the form for 1.9 f ∝ (1 z) nuclei at . Our LF shows a smooth transition 18 M 14 B from the brighter Seyfert LF of J. Huchra and R. Burg (ApJ, 393, 90 [1992]) and flattens at . This flattening of M ≥ 16 B the LF at fainter magnitudes is inconsistent with models using pure luminosity or density evolution fitted to quasar LFs at similar redshifts. Based on the observed number density of compact nuclei in this study, we find that almost all presentday spiral galaxies may host an active LLAGN at some point in their lives.

A Study of Nine High-Redshift Clusters of Galaxies. III. [ITAL]Hubble[/ITAL] [ITAL]Space[/ITAL] [ITAL]T[/ITAL][ITAL]elescope[/ITAL] Morphology of Clusters 0023+0423 and 1604+4304

We present a detailed morphological analysis of the galaxy populations in the first two clusters to be completed in an extensive observational study of nine high-redshift clusters of galaxies. These two clusters, Cl 0023+0423 and Cl 1604+4304, are at redshifts of z = 0.84 and z = 0.90, respectively. The morphological studies are based on high angular resolution imagery taken with Wide Field Planetary Camera 2 aboard the Hubble Space Telescope. These data are combined with deep, ground-based BVRI photometry and spectra taken with the Keck 10 m telescopes. The morphological classifications presented in this paper consist of two parts. First, we provide a quantitative description of the structural properties of ~600 galaxies per cluster field using the Medium Deep Survey automated data reduction and object classification software. This analysis includes the galaxy position, photometry, and best-fit bulge+disk model. Second, for the brightest subsample of ~200 galaxies per cluster field, we provide a more detailed morphological description through a visual classification based on the revised Hubble classification scheme. Based on these classifications, we have examined the general relation between galaxy morphology and other photometric and spectral properties. We find that, as expected, the elliptical and S0 galaxies are redder, on average, than are the spiral and irregular galaxies. In addition, there is a strong correlation between morphology and spectral type. Of the galaxies that are visually classified as ellipticals, the majority show K star absorption spectra that are typical of nearby, red early-type galaxies; however, a few are actually blue compact galaxies with spectra characterized by fairly strong, narrow emission lines. Normal late-type galaxies typically have spectra with blue colors and [O II] emission, while the presence of strong star formation features, such as extremely high equivalent width [O II], Hβ, and/or [O III] emission, is always accompanied by peculiar morphologies that suggest recent mergers or interactions. We have used the statistical distributions of cluster galaxy morphologies to probe the overall morphological composition of these two systems. This analysis reveals that the two clusters contain very different galaxy populations. Cl 0023+0423 has a galaxy population that is more similar to groups of galaxies and the field. This system is almost completely dominated by spiral galaxies. Cl 1604+4304, however, has a morphological composition that is more typical of a normal, present-day cluster; early-type galaxies make up ~76% of all galaxies brighter than MV = -19.0 + 5 log h in the central ~0.5 h-1 Mpc. The ratio of S0 galaxies to elliptical galaxies in this cluster is 1.7 ± 0.9, consistent with local cluster populations. The morphological results support the conclusions of the dynamical analysis presented in the second paper of this series. Cl 0023+0423 consists of two galaxy groups that are separated by ~2900 km s-1 in radial velocity. Cl 1604+4304, on the other hand, has a velocity distribution indicating that it is already well formed and relaxed. The morphological composition, velocity dispersion, and implied mass of the Cl 1604+4304 system are consistent with an Abell richness class 2 or 3 cluster.

The physical parameters of the evolving population of faint galaxies

The excess numbers of blue galaxies at faint magnitudes is a subject of much controversy. Recent Hubble Space Telescope results has revealed a plethora of galaxies with peculiar morphologies tentatively identified as the evolving population. We report the results of optical spectroscopy and near-infrared photometry of a sample of faint \HST galaxies from the Medium Deep Survey to ascertain the physical properties of the faint morphological populations. We find four principal results: Firstly that the population of objects classified as `peculiar' are intrinsically luminous in the optical ($M_B\sim -19$). Secondly these systems tend to be strong sources of [OII] line luminosity. Thirdly the optical-infrared colours of the faint population (a) confirm the presence of a population of compact blue galaxies and (b) show the stellar populations of Irregular/Peculiar galaxies encompass a wide range in age. Finally a surface-brightness comparison with the local galaxy sample of Frei et al shows that these objects are not of anomalously low surface brightness, rather we find that all morphological classes have evolved to a higher surface brightness at higher-redshifts ($z>0.3$).

Hubble Space TelescopeImaging of the CFRS and LDSS Redshift Surveys. I. Morphological Properties

We analyze Hubble Space Telescope images of a complete sample of 341 galaxies drawn from the CFRS and LDSS ground-based redshift surveys. In this, the first paper in the series, each galaxy has been morphologically classified according to a scheme similar to that developed for the Medium Deep Survey. We discuss the reproducibility of these classifications and quantify possible biases that may arise from various redshift-dependent effects. We then discuss automated classifications of the sample and conclude, from several tests, that we can expect an apparent migration with redshift to later Hubble types that corresponds to a misclassification in our adopted machine classification system of ~24% ± 11 of the true spirals as peculiars at a redshift z 0.9. After allowing for such biases, the redshift distribution for normal spirals, together with their luminosity function derived as a function of redshift, indicates approximately 1 mag of luminosity evolution in BAB by z 1. The elliptical sample is too small for precise evolutionary constraints. However, we find a substantial increase in the proportion of galaxies with irregular morphology at large redshift from 9% ± 3% for 0.3 ≤ z ≤ 0.5 to 32% ± 12% for 0.7 ≤ z ≤ 0.9. These galaxies also appear to be the dominant cause of the rapid rise with redshift in the blue luminosity density identified in the redshift surveys. Although galaxies with irregular morphology may well comprise a mixture of different physical systems and might not correspond to present-day irregulars, it is clear that the apparently declining abundance and luminosities of our distant irregulars holds an important key to understanding recent evolution in the star formation history of normal galaxies.

Two serendipitous low-mass LMC clusters discovered with HST

We present V and I photometry of two open clusters in the LMC down to V∼26. The clusters were imaged with the Wide Field and Planetary Camera 2 (WFPC2) on board the Hubble Space Telescope (HST), as part of the Medium Deep Survey Key Project. Both are low-luminosity (MV∼−3.5), low-mass (M∼103 M⊙) systems. The chance discovery of these two clusters in two parallel WFPC2 fields suggests a significant incompleteness in the LMC cluster census near the bar. One of the clusters is roughly elliptical and compact, with a steep light profile, a central surface brightness μV(0)∼20.2 mag arcsec−2, a half-light radius rhl∼0.9 pc (total visual major diameter D∼3 pc) and an estimated mass M∼1500 M⊙. From the colour–magnitude diagram and isochrone fits we estimate its age as τ∼(2–5)×108 yr. Its mass function has a fitted slope of Γ=Δlogφ(M)/ΔlogM=−1.8±0.7 in the range probed (0.9≲M/M⊙≲4.5). The other cluster is more irregular and sparse, having shallower density and surface brightness profiles. We obtain Γ=−1.2±0.4, and estimate its mass as M∼400 M⊙. A derived upper limit for its age is τ≲5×108 yr. Both clusters have mass functions with slopes similar to that of R136, a massive LMC cluster, for which HST results indicate Γ∼−1.2. They also seem to be relaxed in their cores and well contained in their tidal radii.

Evidence for Galaxy Interactions/Mergers from Medium Deep Survey WFPC2 Data

We examine the morphological and statistical properties of close galaxy pairs from two sets of 28 WFPC2 fields, acquired for the Medium Deep Survey (MDS) and the Groth-Westphal Survey (GWS) in F606W (V) and F814W (I) passbands. In the GWS sample all fields have uniform 95% completeness down to I 24.3 mag, whereas in the MDS sample, fields have varying 95% completeness limits in the range I 23.6-24.8 mag. In each field ~400 galaxies per 5 square arcmin field are detected. We exploit high-resolution WFPC2 images to systematically determine morphological classifications of galaxies as disk or bulge dominated down to I ≤ 23 mag (V 24 mag) and to differentiate galaxies from stars 1 magnitude fainter. Down to I ≤ 25 mag the number of galaxy pairs with separations θ ≤ 30 is consistent with a shortward extrapolation of the angular two-point correlation function ω(θ) θ-0.8 observed from the same data; the fraction of such pairs showing morphological evidence for physical association accounts for a third of the total numbers suggested by a shortward extrapolation of ω(θ). The latter result may not be too surprising given the low surface brightness of the tidal tails resulting from galaxy interactions; i.e., much of the evidence for interactions may fall below our detection limit. Moreover, we find no trend between apparent physical association (on the basis of morphology) and (V - I) color or I-magnitude difference between pair members of the θ 30 pair sample. We use recent galaxy redshift surveys to estimate the rate of galaxy merging occurring in the MDS and GWS galaxy pair samples. From this work we find that merging has a moderate dependence on redshift: we derive an estimate for the galaxy pair fraction Pf (1 + z)m, with m = 1.2 ± 0.4 for galaxies with I ≤ 25 mag (zmed 1-2). Two scenarios are consistent both with this low value of m and for the low correlation amplitude: (a) a low-density universe with strong clustering evolution parameterized by a clustering exponent e 1.0 such that galaxy cluster-scale structures shrink relative to the proper coordinate frame; and/or (b) a weakly clustered galaxy population, the majority of which fade or dissipate below zmed 0.5 (I 20 mag), thus mimicking the apparently strong evolution in the correlation amplitude, Aω. Although not directly observed using our data, the possible flattening of the slope of ω(θ) with increasing survey depth can explain the strong decline in Aω and allow for greater pair fraction evolution limited to m ≤ 1.6.

High-Resolution V, I, and K-Band Imaging of Faint Field Galaxies from the HST Medium-Deep Survey

High-Resolution V, I, and K-Band Imaging of Faint Field Galaxies from the HST Medium-Deep Survey

Quantitative Morphology of Moderate‐Redshift Galaxies: How Many Peculiar Galaxies Are There?

The advent of the Hubble Space Telescope (HST) has provided images of galaxies at moderate and high redshifts and changed the scope of galaxy morphologies considerably. It is evident that the Hubble Sequence requires modifications in order to incorporate all the various morphologies one encounters at such redshifts. We investigate and compare different approaches to quantifying peculiar galaxy morphologies on images obtained from the Medium Deep Survey (MDS) and other surveys using the Wide Field Planetary Camera 2 (WFPC2) on board the HST, in the I band (filter F814W). We define criteria for peculiarity and put them to use on a sample of 978 galaxies, classifying them by eye as either normal or peculiar. Based on our criteria and on concepts borrowed from digital image processing we design a set of four purely morphological parameters, which comprise the overall texture (or ``blobbiness'') of the image; the distortion of isophotes; the filling-factor of isophotes; and the skeleta of detected structures. We also examine the parameters suggested by Abraham et al. (1995). An artificial neural network (ANN) is trained to distinguish between normal and peculiar galaxies. While the majority of peculiar galaxies are disk-dominated, we also find evidence for a significant population of bulge-dominated peculiars. Consequently, peculiar galaxies do not all form a ``natural'' continuation of the Hubble sequence beyond the late spirals and the irregulars. The trained neural network is applied to a second, larger sample of 1999 WFPC2 images and its probabilistic capabilities are used to estimate the frequency of peculiar galaxies at moderate redshifts as $35 \pm 15 %$.

Compact Nuclei in Moderately Redshifted Galaxies

The Hubble Space Telescope (HST) Wide Field Planetary Camera 2 is being used to obtain high-resolution images (≤015 FWHM) in the V (F606W) and I (F814W) bands for several thousand distant galaxies as part of the Medium Deep Survey (MDS). An important scientific aim of the MDS is to identify possible active galactic nucleus (AGN) candidates from these images in order to measure the faint end of the AGN luminosity function, as well as to study the host galaxies of AGNs and nuclear starburst systems. We are able to identify candidate objects based on morphology. Candidates are selected by fitting bulge + disk models and bulge + disk + point-source nuclei models to HST-imaged galaxies and determining the best model fit to the galaxy light profile.

Weak gravitational lensing around field galaxies in Hubble Space Telescope survey images

Using data from the HST Medium Deep Survey, a long-term Key Project, together with generically similar archived data, we have discovered evidence for weak gravitational `shear' of background field galaxies (I = 22 -- 26) in the vicinity of isolated, foreground galaxies ( I = 15 -- 22), especially those of early type. The statistical lensing is demonstrated by the slight preferential orientation of the major axes of the background galaxies in directions at right angles to the lines joining them to the foreground ones. The detected shear is at the level of $\delta\phi = 2.5^{o}\pm 1.2^{o}$ averaged over the background galaxies at about ~10 half-light radii from 400 foreground ellipticals, corresponding to a polarization of about 0.04. A positive but less significant result is also reported for foreground spirals. This result excludes the de Vaucouleurs model for the mass distribution of ellipticals, but is consistent with elliptical galaxies having total M/L ~ 100 and extensive dark halos.

Faint galaxy counts as a function of morphological type in a hierarchical merger model

The unprecedented resolution of the refurbished Wide Field and Planetary Camera 2 (WFPC2) on the Hubble Space Telescope (HST) has led to major advances in our understanding of galaxy formation. The high image quality in the Medium Deep Survey and Hubble Deep Field has made it possible, for the first time, to classify faint distant galaxies according to morphological type. These observations have revealed a large population of galaxies classed as irregulars or which show signs of recent merger activity. Their abundance rises steeply with apparent magnitude, providing a likely explanation for the large number of blue galaxies seen at faint magnitudes. We demonstrate that such a population arises naturally in a model in which structure forms hierarchically and which is dynamically dominated by cold dark matter. The number counts of irregular, spiral and elliptical galaxies as a function of magnitude seen in the HST data are well reproduced in this model.We present detailed predictions for the outcome of spectroscopic follow-up observations of the HST surveys. By measuring the redshift distributions of faint galaxies of different morphological types, these programmes will provide a test of the hierarchical galaxy formation paradigm and might distinguish between models with different cosmological parameters.

A Medium-deep Survey of a Minislice at the North Galactic Pole. II. The Data

view Abstract Citations (11) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Medium-deep Survey of a Minislice at the North Galactic Pole. II. The Data Willmer, C. N. A. ; Koo, David C. ; Ellman, Nancy ; Kurtz, Michael J. ; Szalay, Alex S. Abstract We report 328 redshifts, b_J_ magnitudes, and b_J_ - r_F_ colors of galaxies measured in a redshift survey of a 4^deg^ x 0.67^deg^ slice close to the north Galactic pole. The faintest galaxies in this survey have a magnitude of b_j_ ~ 20.5. The redshifts present external errors of the order of 70 km s^-1^ and we estimate that the mean photometry errors are ~0.2 for magnitudes and ~0.3 for colors. The redshift completeness level of the sample is of the order of ~35% at b_J_ = 20, and part of this rather low completeness is the result of the combination of limitations imposed by the multifiber system with the clustering of galaxies, and an insufficient number of configurations. At the nominal magnitude limit of the survey, we were able to measure redshifts for ~70% of the galaxies we observed. From the correlation between observed properties of the galaxies in this sample, we demonstrate that the mean surface brightness is a major limiting factor in our ability to measure redshifts of faint objects. Publication: The Astrophysical Journal Supplement Series Pub Date: June 1996 DOI: 10.1086/192298 arXiv: arXiv:astro-ph/9606076 Bibcode: 1996ApJS..104..199W Keywords: COSMOLOGY: OBSERVATIONS; GALAXIES: DISTANCES AND REDSHIFTS; GALAXIES: PHOTOMETRY; SURVEYS; Astrophysics E-Print: 39 pages, uses AAS LaTeX v4.0 macros. Includes 10 Postscript figures. Table 3 is corrected for systematic error in published version of the paper. ApJS 1996 June issue full text sources arXiv | ADS | data products SIMBAD (353) NED (329) CDS (2) Related Materials (2) Catalog: 1997yCat.7200....0W Erratum: 1996ApJS..107..823W