Sloan Digital Sky Survey Catalog Research Articles

Properties of Nuclear Star Clusters in Low Surface Brightness Galaxies

Using the Systematically Measuring Ultra-Diffuse Galaxies and Sloan Digital Sky Survey catalogs and our own reprocessing of the Legacy Survey imaging, we investigate the properties of nuclear star clusters (NSCs) in galaxies having central surface brightnesses as low as 27 mag arcsec−2. We identify 273 (123 with known redshift) and 32 NSC-bearing galaxies in the two samples, respectively, where we require candidate NSCs to have a separation of less than 0.10r e from the galaxy center. We find that galaxies with low central surface brightness (μ 0,g > 24 mag arcsec−2) are more likely to contain an NSC if they (1) have a higher stellar mass, (2) have a higher stellar-to-total mass ratio, (3) have a brighter central surface brightness, (4) have a larger axis ratio, or (5) lie in a denser environment. Because of the correlations among these various quantities, it is likely that only one or two are true physical drivers. We also find scaling relations for the NSC mass with stellar mass (M NSC/ M⊙=106.02±0.03(M*,gal/108 M⊙)0.77±0.04 ) and halo mass (M NSC/ M⊙=106.11±0.05(Mh,gal/1010 M⊙)0.92±0.05 ), although it is the scaling with halo mass that is consistent with a direct proportionality. In galaxies with an NSC, M NSC ≈ 10−4 M h,gal. This proportionality echoes the finding of a direct proportionality between the mass (or number) of globular clusters (GCs) in galaxies and the galaxy’s total mass. These findings favor a related origin for GCs and NSCs.

106 New Emission-line Galaxies and 29 New Galactic H ii Regions are Identified with Spectra in the Unknown Data Set of LAMOST DR7

This work is to retrieve emission-line spectra from the “Unknown” data set in LAMOST DR7 V1.2, most of which are low signal-to-noise ratios spectra. In the work, we perform emission line search and redshift calculations on the Unknown data set to get possible emission line galaxy spectra. Taking the galaxy spectra released by LAMOST as templates, the Product Quantization (PQ) based approximate nearest neighbor (ANN) search is used to retrieve the nearest neighbors of each spectrum. We keep the spectra for which the calculated redshift and the published redshift of the template meet the threshold, and 16,188 spectra with emission lines are obtained from the LAMOST DR7 Unknown data set. After visual inspection of spectra 10,266 spectra are left, in which 5828 spectra are identified as emission-line galaxies, 1782 spectra show ionization nebula features, and other 2656 are not clearly classified. Among 5828 spectra, 5720 can be found in Strasbourg astronomical Data Center catalog, Sloan Digital Sky Survey catalog, or NASA/IPAC Extragalactic Database catalog. The 108 spectra (corresponding to 106 unique coordinates of R.A. and decl.) which have no record in these three databases are new discoveries; for the 1782 spectra showing ionization nebula features, most of them have radial velocities less than 150 kilometers per second. We check them with the latest version of WISE H ii catalog V2.0 (short for HIICat V2) and 985 out of the 1782 spectra belong to 72 H ii regions. Of these H ii regions, 43 were previously identified while the other 29 are newly identified in this work including 797 newly observed spectra. Besides, there are still 2656 spectra that cannot be clearly classified although they have obvious emission lines and with small redshift. Finally, 106 new emission-line galaxies and 29 new Galactic H ii regions are identified, and we conclude that the ANN method sped up by the PQ algorithm is efficient in solving the problem of pairing spectra with massive data set to figure out their classes. We present our result at the link http://paperdata.china-vo.org/LY_paper/Work2/pressWork2_last.zip.

The disk–torus system in active galactic nuclei: possible evidence of highly spinning black holes

We study the ratio R between the luminosity of the torus and that of the accretion disk, inferred from the relativistic model KERRBB for a sample of approximately 2000 luminosity-selected radio-quiet Type I active galactic nuclei from the Sloan Digital Sky Survey catalog. We find a mean ratio R ≈ 0.8 and a considerable number of sources with R ≳ 1. Our statistical analysis regarding the distribution of the observed ratios suggests that the largest values might be linked to strong relativistic effects due to a large black hole spin (a > 0.8), despite the radio-quiet nature of the sources. The mean value of R sets a constraint on the average torus aperture angle (in the range 30° < θT < 70°) and, for about one-third of the sources, the spin must be a > 0.7. Moreover, our results suggest that the strength of the disk radiation (i.e., the Eddington ratio) could shape the torus geometry and the relative luminosity ratio R. Given the importance of the involved uncertainties on this statistical investigation, an extensive analysis and discussion have been made to assess the robustness of our results.

SciServer: A science platform for astronomy and beyond

We present SciServer, a science platform built and supported by the Institute for Data Intensive Engineering and Science at the Johns Hopkins University. SciServer builds upon and extends the SkyServer system of server-side tools that introduced the astronomical community to SQL (Structured Query Language) and has been serving the Sloan Digital Sky Survey catalog data to the public. SciServer uses a Docker/VM based architecture to provide interactive and batch mode server-side analysis with scripting languages like Python and R in various environments including Jupyter (notebooks), RStudio and command-line in addition to traditional SQL-based data analysis. Users have access to private file storage as well as personal SQL database space. A flexible resource access control system allows users to share their resources with collaborators, a feature that has also been very useful in classroom environments. All these services, wrapped in a layer of REST APIs, constitute a scalable collaborative data-driven science platform that is attractive to science disciplines beyond astronomy.

A catalogue of Locus Algorithm pointings for optimal differential photometry for 23 779 quasars

ABSTRACT This paper presents a catalogue of optimized pointings for differential photometry of 23 779 quasars extracted from the Sloan Digital Sky Survey (SDSS) Catalogue and a Score for each indicating the quality of the Field of View (FoV) associated with that pointing. Observation of millimagnitude variability on a time-scale of minutes typically requires differential observations with reference to an ensemble of reference stars. For optimal performance, these reference stars should have similar colour and magnitude to the target quasar. In addition, the greatest quantity and quality of suitable reference stars may be found by using a telescope pointing which offsets the target object from the centre of the FoV. By comparing each quasar with the stars which appear close to it on the sky in the SDSS Catalogue, an optimum pointing can be calculated, and a figure of merit, referred to as the ‘Score’ is calculated for that pointing. Highly flexible software has been developed to enable this process to be automated and implemented in a distributed computing paradigm, which enables the creation of catalogues of pointings given a set of input targets. Applying this technique to a sample of 40 000 targets from the fourth SDSS quasar catalogue resulted in the production of pointings and Scores for 23 779 quasars based on their magnitudes in the SDSS r-band. This catalogue is a useful resource for observers planning differential photometry studies and surveys of quasars to select those which have many suitable celestial neighbours for differential photometry.

Doppler Factor Estimation for Fermi Blazars

Abstract In this work, we exploit the luminosity of the broad-line region (BLR) for 50 Fermi blazars through matching the coordinates between the Sloan Digital Sky Survey catalog, Fermi Large Area Telescope Third Source Catalog, and the Fermi Large Area Telescope Fourth Source Catalog and fitting their emission lines. In total, we collected a sample of 350 blazars with broad-line emissions including 50 new objects and 300 blazars from published works to revisit the correlation between the γ-ray luminosity and the broad-line luminosity, and proposed a new method to estimate the Doppler factors based on the correlation between the radiative power of the jet and luminosity of the BLR. We come to following conclusions. (1) For the 50 Fermi blazars, their broad-line luminosity (log L BLR) ranges from 41.82–45.2 erg s−1 with a mean value of 44.39 erg s−1. (2) The Doppler factor (δ) ranges from δ = 0.35 to δ = 85.66 with a mean value of 12.54, which is consistent with the results in the literature. (3) There are positive correlations between γ-ray luminosity and broad-line luminosity, and between γ-ray luminosity and the Doppler factor.

Multiband Probabilistic Cataloging: A Joint Fitting Approach to Point-source Detection and Deblending

Abstract Probabilistic cataloging (PCAT) outperforms traditional cataloging methods on single-band optical data in crowded fields. We extend our work to multiple bands, achieving greater sensitivity (∼0.4 mag) and greater speed (500×) compared to previous single-band results. We demonstrate the effectiveness of multiband PCAT on mock data, in terms of both recovering accurate posteriors in the catalog space and directly deblending sources. When applied to Sloan Digital Sky Survey (SDSS) observations of M2, taking Hubble Space Telescope data as truth, our joint fit on r- and i-band data goes ∼0.4 mag deeper than single-band probabilistic cataloging and has a false discovery rate less than 20% for F606W ≤ 20. Compared to DAOPHOT, the two-band SDSS catalog fit goes nearly 1.5 mag deeper using the same data and maintains a lower false discovery rate down to F606W ∼ 20.5. Given recent improvements in computational speed, multiband PCAT shows promise in application to large-scale surveys and is a plausible framework for joint analysis of multi-instrument observational data. https://github.com/RichardFeder/multiband_pcat.

Validating Planck SZ2 clusters with optical counterparts

We perform an extensive analysis of optical counterparts of Planck PSZ2 clusters, considering matches with three recent catalogs built from Sloan Digital Sky Survey (SDSS) data: AMF DR9, redMaPPer (v6.3) and Wen et al (WHL). We significantly extend the number of optical counterparts of detected Planck clusters, and characterize the optical properties when multiple identifications in different catalogs exist. For Planck clusters which already possess an external validation, we analyze the redshift assignment from both optical and X–ray observations. We then analyze the Planck Cosmology Sample and comment on redshift and potential mass mis-determinations due to alignment issues. Finally, we inspect the reconstructed y-map from Planck and comment on the possibility of detecting further optical clusters. Overall, using the AMF DR9 main (extended) catalog, we find 485 (511) optical matches, with 45 (55) previously unmatched PSZ2 clusters, to be compared with the 374 optical matches already present in PSZ2. 29 of the 55 previously unmatched clusters do not yet have a follow-up observation in the literature. 18 of these are found in more than one SDSS catalog with consistent redshifts. We provide redshift and mass estimates for the newly matched clusters, and discuss the comparison with the follow-ups, when present. We find good agreement between the redMaPPer and AMF DR9 redshift determinations. AMF DR9 tends to predict lower redshifts for a few PSZ2 high–redshift clusters which were previously validated by an optical counterpart. From the Planck Cosmology Sample, optical matches are found for 204 of the 278 objects in the observed area. We find 14 clusters which merit further investigation and discuss possible alignment issues for 9 of them. After inspecting the y-map, we provide a list of 229 optical clusters not included in the Planck PSZ2 catalog, yet showing a prominent y signal. We have further investigated the clusters with the most prominent y signal using a proper MMF technique and we find 20 (12) clusters with a S/N > 4.5 ( > 6) which are not included in the PSZ2 (cosmology sample) catalog. We discuss point source contamination for these objects.

Separating stars from quasars: Machine learning investigation using photometric data

Abstract A problem that lends itself to the application of machine learning is classifying matched sources in the GALEX (Galaxy Evolution Explorer) and SDSS (Sloan Digital Sky Survey) catalogs into stars and quasars based on color-color plots. The problem is daunting because stars and quasars are still inextricably mixed elsewhere in the color-color plots and no clear linear/non-linear boundary separates the two entities. Diversity and volume of samples add to the complexity of the problem. We explore the efficacy of neural network based classification techniques in discriminating between stars and quasars using GALEX and SDSS photometric data. Both sources have compact optical morphology but are very different in nature and are at very different distances. We have used those objects with associated spectroscopic information as our training-set and built neural network and ensemble classifiers that appropriately classify photometric samples without associated spectroscopic labels. Catalogs comprising of samples labeled using our classifiers can be further used in studies of photometric sources. The design of a novel Generative Adversarial Network (GAN) based classifier is proposed in the paper to tackle the classification problem. To evaluate the correctness of the classifiers, we report the accuracy and other performance metrics and find reasonably satisfactory range of 91%–100%.

Exploring the Age-dependent Properties of M and L Dwarfs Using Gaia and SDSS

Abstract We present a sample of 74,216 M and L dwarfs constructed from two existing catalogs of cool dwarfs spectroscopically identified in the Sloan Digital Sky Survey (SDSS). We cross-matched the SDSS catalog with Gaia DR2 to obtain parallaxes and proper motions and modified the quality cuts suggested by the Gaia Collaboration to make them suitable for late-M and L dwarfs. We also provide relations between Gaia colors and absolute magnitudes with spectral type and conclude that (G − ) has the tightest relation to spectral type for M and L dwarfs. In addition, we study magnetic activity as a function of position on the color–magnitude diagram, finding that Hα magnetically active stars have, on average, redder colors and/or brighter magnitudes than inactive stars. This effect cannot be explained by youth alone and might indicate that active stars are magnetically inflated, binaries, and/or high metallicity. Moreover, we find that vertical velocity and vertical action dispersion are correlated with Hα emission, confirming that these two parameters are age indicators. We also find that stars below the main sequence have high tangential velocity, which is consistent with a low metallicity and old population of stars that belong to the halo or thick disk.

Milgromian dynamics and dwarf galaxies in galactic voids

We use kinematic data of 103 dwarf galaxies, obtained from the Sloan Digital Sky Survey catalog, to test the Milgromian dynamics (MOND) inside a galactic void. From this data, we compute the line-of-sight velocity dispersions of the dwarf galaxies in the frameworks of MOND and Newtonian dynamics without invoking any dark matter. The prediction for the line-of-sight velocity dispersions from MOND of 53 selected dwarf galaxies is compared with their measured values. For appropriate mass-to-light ratios in the range 1 to 5 for each individual dwarf galaxy, our results for the line-of-sight velocity dispersions predicted by MOND are more compatible with observations than those predicted by Newtonian dynamics.

Robust covariance estimation of galaxy–galaxy weak lensing: validation and limitation of jackknife covariance

We develop a method to simulate galaxy-galaxy weak lensing by utilizing all-sky, light-cone simulations and their inherent halo catalogs. Using the mock catalog to study the error covariance matrix of galaxy-galaxy weak lensing, we compare the full covariance with the "jackknife" (JK) covariance, the method often used in the literature that estimates the covariance from the resamples of the data itself. We show that there exists the variation of JK covariance over realizations of mock lensing measurements, while the average JK covariance over mocks can give a reasonably accurate estimation of the true covariance up to separations comparable with the size of JK subregion. The scatter in JK covariances is found to be $\sim10\%$ after we subtract the lensing measurement around random points. However, the JK method tends to underestimate the covariance at the larger separations, more increasingly for a survey with a higher number density of source galaxies. We apply our method to the the Sloan Digital Sky Survey (SDSS) data, and show that the 48 mock SDSS catalogs nicely reproduce the signals and the JK covariance measured from the real data. We then argue that the use of the accurate covariance, compared to the JK covariance, allows us to use the lensing signals at large scales beyond a size of the JK subregion, which contains cleaner cosmological information in the linear regime.

Quantitative Comparison of Two-point Correlation Functions from Real and Mock SDSS Galaxy Catalogs

We present a simple closed-form bandwidth selection method to obtain the optimal bin size for estimating the two-point correlation function (2PCF). To demonstrate its effectiveness, we apply this procedure in a numerical study using a theoretical point process model to 10 mock Sloan Digital Sky Survey (SDSS) catalogs with the same cosmology, and to a real SDSS catalog. With a point process model, the real 2PCF is known and ratios of the mean square errors of estimates can be computed. The standard deviation of 2PCF estimates, obtained from the 10 mock catalogs, provides information about the uncertainty of estimates. With the SDSS catalog, we use subsampling to assess uncertainty. In each case, we find that our procedure performs better than the commonly used procedure of equal bandwidths on the log-scale.

Catalog of candidates for quasars at 3 < z < 5.5 selected among X-Ray sources from the 3XMM-DR4 survey of the XMM-Newton observatory

We have compiled a catalog of 903 candidates for type 1 quasars at redshifts 3<z<5.5 selected among the X-ray sources of the serendipitous XMM-Newton survey presented in the 3XMM-DR4 catalog (the median X-ray flux is 5x10^{-15} erg/s/cm^2 the 0.5-2 keV energy band) and located at high Galactic latitudes >20 deg in Sloan Digital Sky Survey (SDSS) fields with a total area of about 300 deg^2. Photometric SDSS data as well infrared 2MASS and WISE data were used to select the objects. We selected the point sources from the photometric SDSS catalog with a magnitude error Delta z<0.2 and a color i-z<0.6 (to first eliminate the M-type stars). For the selected sources, we have calculated the dependences chi^2(z) for various spectral templates from the library that we compiled for these purposes using the EAZY software. Based on these data, we have rejected the objects whose spectral energy distributions are better described by the templates of stars at z=0 and obtained a sample of quasars with photometric redshift estimates 2.75<zphot<5.5. The selection completeness of known quasars at z>3 in the investigated fields is shown to be about 80%. The normalized median absolute deviation is 0.07, while the outlier fraction is eta= 9. The number of objects per unit area in our sample exceeds the number of quasars in the spectroscopic SDSS sample at the same redshifts approximately by a factor of 1.5. The subsequent spectroscopic testing of the redshifts of our selected candidates for quasars at 3<z<5.5 will allow the purity of this sample to be estimated more accurately.

A photometric selection of white dwarf candidates in Sloan Digital Sky Survey Data Release 10

We present a method which uses cuts in colour–colour and reduced proper motion–colour space to select white dwarfs without the recourse to spectroscopy while allowing an adjustable compromise between completeness and efficiency. Rather than just producing a list of white dwarf candidates, our method calculates a probability of being a white dwarf (PWD) for any object with available multiband photometry and proper motion. We applied this method to all objects in the Sloan Digital Sky Survey (SDSS) Data Release 10 (DR10) photometric footprint and to a few selected sources in DR7 which did not have reliable photometry in DR9 or DR10. This application results in a sample of 61 969 DR10 and 3799 DR7 photometric sources with calculated PWD from which it is possible to select a sample of ∼23 000 high-fidelity white dwarf candidates with Teff ≳ 7000 K and g ≤ 19. This sample contains over 14 000 high confidence white dwarfs candidates which have not yet received spectroscopic follow-up. These numbers show that, to date, the spectroscopic coverage of white dwarfs in the SDSS photometric footprint is, on average, only ∼40 per cent complete. While we describe here in detail the application of our selection to the SDSS catalogue, the same method could easily be applied to other multicolour, large area surveys. We also publish a list of 8701 bright (g ≤ 19) white dwarfs with SDSS spectroscopy, of which 1781 are new identifications in DR9/DR10.

Weighing the Giants – II. Improved calibration of photometry from stellar colours and accurate photometric redshifts

We present improved methods for using stars found in astronomical exposures to calibrate both star and galaxy colours as well as to adjust the instrument flat-field. By developing a spectroscopic model for the Sloan Digital Sky Survey (SDSS) stellar locus in colour–colour space, synthesizing an expected stellar locus, and simultaneously solving for all unknown zero-points when fitting to the instrumental locus, we increase the calibration accuracy of stellar locus matching. We also use a new combined technique to estimate improved flat-field models for the Subaru SuprimeCam camera, forming ‘star flats’ based on the magnitudes of stars observed in multiple positions or through comparison with available measurements in the SDSS catalogue. These techniques yield galaxy magnitudes with reliable colour calibration (≲0.01–0.02 mag accuracy) that enable us to estimate photometric redshift probability distributions without spectroscopic training samples. We test the accuracy of our photometric redshifts using spectroscopic redshifts zs for ∼5000 galaxies in 27cluster fields with at least five bands of photometry, as well as galaxies in the Cosmic Evolution Survey (COSMOS) field, finding σ((zp − zs)/(1 + zs)) ≈ 0.03 for the most probable redshift zp. We show that the full posterior probability distributions for the redshifts of galaxies with five-band photometry exhibit good agreement with redshifts estimated from thirty-band photometry in the COSMOS field. The growth of shear with increasing distance behind each galaxy cluster shows the expected redshift–distance relation for a flat Λ cold dark matter (Λ-CDM) cosmology. Photometric redshifts and calibrated colours are used in subsequent papers to measure the masses of 51 galaxy clusters from their weak gravitational shear and determine improved cosmological constraints. We make our python code for stellar locus matching publicly available at http://big-macs-calibrate.googlecode.com; the code requires only input catalogues and filter transmission functions.

Quasars with Anomalous Hβ Profiles. I. Demographics

Abstract The H$\beta$ emission line in a typical Type I quasar is composed of a broad base and a narrow core, with the core velocity characteristic of narrow-line region emission, and line-fitting routines typically assume this picture. We test the effects of removing this constraint, and find a substantial group of Type I quasars in the Sloan Digital Sky Survey catalog with H$\beta$ emission line cores broader than 1200 km s$^{-1}$, above the velocity believed possible for gas in the quasar narrow-line region. We identify this group of “anomalous H$\beta$ quasars” (AHQs) as a distinct population because of a variety of spectral and photometric signatures common to these AHQs but atypical of other quasars. These features are similar to some aspects of narrow-line Seyfert 1s and correlations identified by Eigenvector 1, but also contain distinct features that make it difficult to classify AHQs. We demonstrate that AHQs comprise at least 11% and most likely approximately one quarter of the SDSS Type I quasar population at 0.2 $&amp;lt;$z$&amp;lt;$ 0.8. For AHQs, the [O iii]$\lambda$ 4959, 5007 profile is often better fit by de-linking it from the H$\beta$ core, while a more standard linked fit produces a tight correlation between narrow- and broad-line velocities. We find that [O iii] in AHQs sometimes has a standard narrow-line profile and other times matches the H$\beta$ core, but is rarely in between the two, implying that the broadened core emission arises from a distinct physical region. Another feature of AHQs is a diminished [O ii] line, which might indicate a connection between AHQs and the interstellar mediums of their host galaxies, through reduced photoionization or star formation. We find that it is difficult to produce AHQs using the current quasar standard model.

Re-Calibration of SDF/SXDS Photometric Catalogs of Suprime-Cam with SDSS Data Release 8

We present photometric recalibrations of the Subaru Deep Field (SDF) and Subaru/XMM-Newton Deep Survey (SXDS). Recently, Yamanoi et al. (2012, AJ, 144, 40) suggested the existence of a discrepancy between the SDF and SXDS catalogs. We have used the Sloan Digital Sky Survey (SDSS) Data Release 8 (DR8) catalog and compared stars in common between SDF/SXDS and SDSS. We confirmed that there exists a 0.12 mag offset in the $ B$-band between the SDF and SXDS catalogs. Moreover, we found that significant zero-point offsets in the $ i$-band ($ \sim$ 0.10 mag) and the $ z$-band ($ \sim$ 0.14 mag) need to be introduced to the SDF/SXDS catalogs to make it consistent with the SDSS catalog. We report the measured zero point offsets of five filter bands of SDF/SXDS catalogs. We studied the potential cause of these offsets, but the origins are yet to be understood.

SYSTEMATIC SEARCH FOR EXTREMELY METAL-POOR GALAXIES IN THE SLOAN DIGITAL SKY SURVEY

We carry out a systematic search for extremely metal poor (XMP) galaxies in the spectroscopic sample of Sloan Digital Sky Survey (SDSS) data release 7 (DR7). The XMP candidates are found by classifying all the galaxies according to the form of their spectra in a region 80AA wide around Halpha. Due to the data size, the method requires an automatic classification algorithm. We use k-means. Our systematic search renders 32 galaxies having negligible [NII] lines, as expected in XMP galaxy spectra. Twenty one of them have been previously identified as XMP galaxies in the literature -- the remaining eleven are new. This was established after a thorough bibliographic search that yielded only some 130 galaxies known to have an oxygen metallicity ten times smaller than the Sun (explicitly, with 12+log(O/H) <= 7.65). XMP galaxies are rare; they represent 0.01% of the galaxies with emission lines in SDSS/DR7. Although the final metallicity estimate of all candidates remains pending, strong-line empirical calibrations indicate a metallicity about one-tenth solar, with the oxygen metallicity of the twenty one known targets being 12+log(O/H)= 7.61 +- 0.19. Since the SDSS catalog is limited in apparent magnitude, we have been able to estimate the volume number density of XMP galaxies in the local universe, which turns out to be (1.32 +- 0.23) x 10^-4 Mpc^-3. The XMP galaxies constitute 0.1% of the galaxies in the local volume, or some 0.2% considering only emission line galaxies. All but four of our candidates are blue compact dwarf galaxies (BCDs), and 24 of them have either cometary shape or are formed by chained knots.

GALAXY CLUSTER ENVIRONMENTS OF RADIO SOURCES

Using the Sloan Digital Sky Survey (SDSS) and the FIRST (Faint Images of the Radio Sky at Twenty Centimeters) catalogs, we examined the optical environments around double-lobed radio sources. Previous studies have shown that multi-component radio sources exhibiting some degree of bending between components are likely to be found in galaxy clusters. Often this radio emission is associated with a cD-type galaxy at the center of a cluster. We cross-correlated the SDSS and FIRST catalogs and measured the richness of the cluster environments surrounding both bent and straight multi-component radio sources. This led to the discovery and classification of a large number of galaxy clusters out to a redshift of z ~ 0.5. We divided our sample into smaller subgroups based on their optical and radio properties. We find that FR I radio sources are more likely to be found in galaxy clusters than FR II sources. Further, we find that bent radio sources are more often found in galaxy clusters than non-bent radio sources. We also examined the environments around single-component radio sources and find that single-component radio sources are less likely to be associated with galaxy clusters than extended, multi-component radio sources. Bent, visually-selected sources are found in clusters or rich groups ~78% of the time. Those without optical hosts in SDSS are likely associated with clusters at even higher redshifts, most with redshifts of z > 0.7.