The Millennium Galaxy Catalogue: the photometric accuracy, completeness and contamination of the 2dFGRS and SDSS-EDR/DR1 data sets (original) (raw)
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Monthly Notices of the Royal Astronomical Society, 2005
We recover the joint and individual space density and surface brightness distribution(s) of galaxies from the Millennium Galaxy Catalogue. The MGC is a local survey spanning 30.9 deg 2 and probing approximately one-two mag arcsec −2 deeper than either the Two-Degree Field Galaxy Redshift Survey (2dFGRS) or the Sloan Digital Sky Survey (SDSS). The MGC contains 10 095 galaxies to B MGC < 20 mag with 96 per cent spectroscopic completeness. For each galaxy we derive individual K-corrections and seeing-corrected sizes. We implement a joint luminosity-surface brightness step-wise maximum likelihood method to recover the bivariate brightness distribution (BBD) inclusive of most selection effects. Integrating the BBD over surface brightness we recover the following Schechter function parameters: φ * = (0.0177 ± 0.0015)h 3 Mpc −3 , M * BMGC − 5 log h = (−19.60 ± 0.04) mag and α = −1.13 ± 0.02. Compared to the 2dFGRS (Norberg et al. 2002) we find a consistent M * value but a slightly flatter faint-end slope and a higher normalisation, resulting in a final luminosity density j bJ = (1.99 ± 0.17) × 10 8 h L ⊙ Mpc −3 -marginally higher than, but consistent with, the earlier 2dFGRS (Norberg et al. 2002), ESP (Zucca et al. 1997), and SDSS z = 0.1 (Blanton et al. 2003a) results. The MGC is inconsistent with the SDSS z = 0 result (+3σ) if one adopts the derived SDSS evolution (Blanton et al. 2003a).
Nature and completeness of galaxies detected in the Two Micron All Sky Survey
Monthly Notices of the Royal Astronomical Society, 2006
The Two Micron All Sky Survey (2MASS) provides the most comprehensive dataset of nearinfrared galaxy properties. We cross correlate the well-defined and highly complete spectroscopic selection of over 156,000 bright (r ≤ 17.5 mag) galaxies in the Sloan Digital Sky Survey (SDSS) Main Galaxy Sample (MGS) with 2MASS sources to explore the nature and completeness of the 2MASS (K-band) selection of nearby galaxies. Using estimates of total galaxy brightness direct from the 2MASS and SDSS public catalogues, corrected only for Galactic extinction, we find that 2MASS detects 90 percent of the MGS brighter than r = 17 mag. We quantify the completeness of 2MASS galaxies in terms of optical properties from SDSS. For r ≤ 16 mag, 93.1% of the MGS is found in the 2MASS Extended Source Catalog (XSC). These detections span the representative range of optical and near-infrared galaxy properties, but with a surface brightness-dependent bias to preferentially miss sources at the extreme blue and low-concentration end of parameter space, which are consistent with the most morphologically late-type galaxy population. An XSC completeness of 97.5% is achievable at bright magnitudes, with blue low-surface-brightness galaxies being the only major source of incompleteness, if one follows our careful matching criteria and weeds out spurious SDSS sources. We conclude that the rapid drop in XSC completeness at r > 16 mag reflects the sharp surface-brightness limit of the extended source detection algorithm in 2MASS. As a result, the r > 16 galaxies found in the XSC are over-representative in red early types and under-representative in blue late types. At r > 16 mag the XSC suffers an additional selection effect from the 2 − 3 ′′ spatial resolution limit of 2MASS. Therefore, in the range 16 < r ≤ 17 mag, 2MASS continues to detect 90% of the MGS, but with a growing fraction found in the Point Source Catalog (PSC) only. Overall, one third of the MGS is detected in the 2MASS PSC but not the XSC. A combined K ≤ 13.57 and r ≤ 16 magnitude-limited selection provides the most representative inventory of galaxies in the local cosmos with near-infrared and optical measurements, and 90.8% completeness. Using data from the SDSS Second Data Release, this sample contains nearly 20,000 galaxies with a median redshift of 0.052.
The Millennium Galaxy Catalogue: Science highlights
2007
The Millennium Galaxy Catalogue (MGC) provides a structural database comprising 10,095 well resolved galaxies drawn from a 37.5 sq degree region of sky, with B_{MGC} < 20.0 mag and 96.1 per cent spectroscopic completeness. The data are being used to investigate a number of diverse topics including: the nearby galaxy merger rate (via close pairs and asymmetry); dust attenuation; bulge and disc luminosity functions; the luminosity size relations; the supermassive black hole mass function; galaxy bimodality; the space-density of high and low surface brightness galaxies; blue spheroids; and the B-band luminosity function. Plans to extend the MGC in area (200 sq deg), depth (K_{Vega}=16.5 mag), resolution (0.5'') and wavelength (u-K) are underway.
NYU-VAGC: a galaxy catalog based on new public surveys
2004
Here we present the New York University Value-Added Galaxy Catalog (NYU-VAGC), a catalog of local galaxies (mostly below a redshift of about 0.3) based on a set of publicly-released surveys (including the 2dFGRS, 2MASS, PSCz, FIRST, and RC3) matched to the Sloan Digital Sky Survey (SDSS) Data Release 2. Excluding areas masked by bright stars, the photometric sample covers 3514 square degrees and the spectroscopic sample covers 2627 square degrees (with about 85% completeness). Earlier, proprietary versions of this catalog have formed the basis of many SDSS investigations of the power spectrum, correlation function, and luminosity function of galaxies. We calculate and compile derived quantities (for example, K-corrections and structural parameters for galaxies). The SDSS catalog presented here is photometrically recalibrated, reducing systematic calibration errors across the sky from about 2% to about 1%. We include an explicit description of the geometry of the catalog, including all imaging and targeting information as a function of sky position. Finally, we have performed eyeball quality checks on a large number of objects in the catalog in order to flag deblending and other errors. This catalog is complementary to the SDSS Archive Servers, in that NYU-VAGC's calibration, geometrical description, and conveniently small size are specifically designed for studying galaxy properties and large-scale structure statistics using the SDSS spectroscopic catalog.
Monthly Notices of the Royal Astronomical Society, 2006
We discuss the panchromatic properties of 99,088 galaxies selected from the Sloan Digital Sky Survey Data Release 1 "main" spectroscopic sample (a flux-limited sample for 1360 deg 2 ). These galaxies are positionally matched to sources detected by ROSAT, GALEX, 2MASS, IRAS, GB6, FIRST, NVSS and WENSS. The matching fraction varies from < 1% for ROSAT and GB6 to ∼40% for GALEX and 2MASS. In addition to its size, the advantages of this sample are well controlled selection effects, faint flux limits and the wealth of measured parameters, including accurate X-ray to radio photometry, angular sizes, and optical spectra. We find strong correlations between the detection fraction at other wavelengths and optical properties such as flux, colors, and emission-line strengths. For example, ∼2/3 of SDSS "main" galaxies classified as AGN using emission-line strengths are detected by 2MASS, while the corresponding fraction for star-forming galaxies is only ∼1/10. Similarly, over 90% of galaxies detected by IRAS display strong emission lines in their optical spectra, compared to ∼50% for the whole SDSS sample. Using GALEX, SDSS, and 2MASS data, we construct the UV-IR broad-band spectral energy distributions for various types of galaxies, and find that they form a nearly one-parameter family. For example, the SDSS u-and r-band data, supplemented with redshift, can be used to "predict" K-band magnitudes measured by 2MASS with an rms scatter of only 0.2 mag. When a dust content estimate determined from SDSS spectra with the aid of models is also utilized, this scatter decreases to 0.1 mag and can be fully accounted for by measurement uncertainties. We demonstrate that this interstellar dust content, inferred from optical SDSS spectra by , is indeed higher for galaxies detected by IRAS and that it can be used to "predict" measured IRAS 60 µm flux density within a factor of two using only SDSS data. We also show that the position of a galaxy in the emission-line-based Baldwin-Phillips-Terlevich diagram is correlated with the optical light concentration index and u−r color determined from the SDSS broad-band imaging data, and discuss changes in the morphology of this diagram induced by requiring detections at other wavelengths. Notably, we find that SDSS "main" galaxies detected by GALEX include a non-negligible fraction (10-30%) of AGNs, and hence do not represent a clean sample of starburst galaxies. We study the IR-radio correlation and find evidence that its slope may be different for AGN and star-forming galaxies and related to the H α /H β line strength ratio.
An SDSS Survey For Resolved Milky Way Satellite Galaxies. I. Detection Limits
Astronomical Journal, 2002
We present the detection limits of a new survey for resolved low surface brightness satellite galaxies to the Milky Way, based on the Sloan Digital Sky Survey (SDSS). Our survey exploits SDSS's major strengths (multi-color photometry, depth, large-scale, and uniformity) by combining filter smoothing with limits in both magnitude and color space to search for low surface brightness galaxies and stellar counterparts to the Compact High Velocity Clouds out to the Milky Way's virial radius (350 kpc). Our calculated detection limits for a purely old stellar population vary with galaxy size and distance between mu_{V,0} = 26.7 and 30.1 mag/sq ''. These limits will allow us to detect systems whose surface brightnesses are .5-3.9 mag/sq '' fainter than Sextans, the lowest surface brightness Local Group member known. Our survey not only is sensitive to lower surface brightness stellar populations than possible with previous Local Group surveys, but will also allow us to make an unbiased and well defined assessment of the completeness of the observed Local Group galaxy luminosity function, so that we may compare the results with the predictions of various structure formation scenarios.
NIBLES: an H I census of stellar mass selected SDSS galaxies
Astronomy & Astrophysics, 2016
To investigate galaxy properties as a function of their total stellar mass, we obtained 21 cm H i line observations at the 100-m class Nançay Radio Telescope of 2839 galaxies from the Sloan Digital Sky Survey (SDSS) in the Local Volume (900 < cz < 12 000 km s −1), dubbed the Nançay Interstellar Baryons Legacy Extragalactic Survey (NIBLES) sample. They were selected evenly over their entire range of absolute SDSS z-band magnitudes (M z ∼ −13.5 to −24 mag), which were used as a proxy for their stellar masses. In this paper, a first, global presentation of the observations and basic results is given; their further analysis will be presented in other papers in this series. The galaxies were originally selected based on their properties, as listed in SDSS DR5. Comparing this photometry to their total H i masses, we noted that, for a few percent, the SDSS magnitudes appeared severely misunderestimated, as confirmed by our re-measurements for selected objects. Although using the later DR9 results eliminated this problem in most cases, 384 still required manual photometric source selection. Usable H i spectra were obtained for 2600 of the galaxies, of which 1733 (67%) were clearly detected and 174 (7%) marginally. The spectra for 241 other observed galaxies could not be used for further analysis owing to problems with either the H i or the SDSS data. We reached the target number of about 150 sources per half-magnitude bin over the M z range −16.5 to −23 mag. Down to −21 mag the overall detection rate is rather constant at the ∼75% level but it starts to decline steadily towards the 30% level at −23 mag. Making regression fits by comparing total H i and stellar masses for our sample, including our conservatively estimated H i upper limits for non-detections, we find the relationship log(M H I /M) = −0.59 log(M) + 5.05, which lies significantly below the relationship found in the M H I /M-M plane when only using H i detections.
Monthly Notices of the Royal Astronomical Society, 2003
The Millennium Galaxy Catalogue (MGC) is a 37.5 deg 2 , medium-deep, B-band imaging survey along the celestial equator, taken with the Wide Field Camera on the Isaac Newton Telescope. The survey region is contained within the regions of both the Two Degree Field Galaxy Redshift Survey (2dFGRS) and the Sloan Digital Sky Survey Early Data Release (SDSS-EDR). The survey has a uniform isophotal detection limit of 26 mag arcsec −2 and it provides a robust, well-defined catalogue of stars and galaxies in the range 16 ≤ B MGC < 24 mag.
The Luminosity Function of Galaxies In SDSS Commissioning Data
The Astronomical …, 2001
In the course of its commissioning observations, the Sloan Digital Sky Survey (SDSS) has produced one of the largest redshift samples of galaxies selected from CCD images. Using 11,275 galaxies complete to r * = 17.6 over 140 square degrees, we compute the luminosity function of galaxies in the r * band over a range −23 < M r * < −16 (for h = 1). The result is well-described by a Schechter function with parameters φ * = (1.46±0.12)×10 −2 h 3 Mpc −3 , M * = −20.83±0.03, and α = −1.20 ± 0.03. The implied luminosity density in r * is j ≈ (2.6 ± 0.3) × 10 8 hL Mpc −3 . We find that the surface brightness selection threshold has a negligible impact for M r * < −18. Using subsets of the data, we measure the luminosity function in the u * , g * , i * , and z * bands as well; the slope at low luminosities ranges from α = −1.35 to α = −1.2. We measure the bivariate distribution of r * luminosity with half-light surface brightness, intrinsic g * − r * color, and morphology. In agreement with previous studies, we find that high surface brightness, red, highly concentrated galaxies are on average more luminous than low surface brightness, blue, less concentrated galaxies. An important feature of the SDSS luminosity function is the use of Petrosian magnitudes, which measure a constant fraction of a galaxy's total light regardless of the amplitude of its surface brightness profile. If we synthesize results for R GKC -band or b j -band using these Petrosian magnitudes, we obtain luminosity densities 2 times that found by the Las Campanas Redshift Survey in R GKC and 1.4 times that found by the Two-degree Field Galaxy Redshift Survey in b j . However, we are able to reproduce the luminosity functions obtained by these surveys if we also mimic their isophotal limits for defining galaxy magnitudes, which are shallower and more redshift dependent than the Petrosian magnitudes used by the SDSS.
The Luminosity Function of Galaxies from SDSS Commissioning Data
2000
In the course of its commissioning observations, the Sloan Digital Sky Survey (SDSS) has produced one of the largest redshift samples of galaxies selected from CCD images. Using 11,275 galaxies complete to r * = 17.6 over 140 square degrees, we compute the luminosity function of galaxies in the r * band over a range −23 < M r * < −16 (for h = 1). The result is well-described by a Schechter function with parameters φ * = (1.46±0.12)×10 −2 h 3 Mpc −3 , M * = −20.83±0.03, and α = −1.20 ± 0.03. The implied luminosity density in r * is j ≈ (2.6 ± 0.3) × 10 8 hL ⊙ Mpc −3. We find that the surface brightness selection threshold has a negligible impact for M r * < −18. Using subsets of the data, we measure the luminosity function in the u * , g * , i * , and z * bands as well; the slope at low luminosities ranges from α = −1.35 to α = −1.2. We measure the bivariate distribution of r * luminosity with half-light surface brightness, intrinsic g * − r * color, and morphology. In agreement with previous studies, we find that high surface brightness, red, highly concentrated galaxies are on average more luminous than low surface brightness, blue, less concentrated galaxies. An important feature of the SDSS luminosity function is the use of Petrosian magnitudes, which measure a constant fraction of a galaxy's total light regardless of the amplitude of its surface brightness profile. If we synthesize results for R GKC-band or b j-band using these Petrosian magnitudes, we obtain luminosity densities 2 times that found by the Las Campanas Redshift Survey in R GKC and 1.4 times that found by the Two-degree Field Galaxy Redshift Survey in b j. However, we are able to reproduce the luminosity functions obtained by these surveys if we also mimic their isophotal limits for defining galaxy magnitudes, which are shallower and more redshift dependent than the Petrosian magnitudes used by the SDSS.