We present an 8 s detection of cosmic magnification measured by the variation of quasar density due to gravitational lensing by foreground large-scale structure. To make this measurement we used 3800 ...deg super(2) of photometric observations from the Sloan Digital Sky Survey (SDSS) containing 6200,000 quasars and 13 million galaxies. Our measurement of the galaxy-quasar cross-correlation function exhibits the amplitude, angular dependence, and change in sign as a function of the slope of the observed quasar number counts that is expected from magnification bias due to weak gravitational lensing. We show that observational uncertainties (stellar contamination, Galactic dust extinction, seeing variations, and errors in the photometric redshifts) are well controlled and do not significantly affect the lensing signal. By weighting the quasars with the number count slope, we combine the cross-correlation of quasars for our full magnitude range and detect the lensing signal at >4 s in all five SDSS filters. Our measurements of cosmic magnification probe scales ranging from 60 h super(-1) kpc to 10 h super(-1) Mpc and are in good agreement with theoretical predictions based on the WMAP concordance cosmology. As with galaxy-galaxy lensing, future measurements of cosmic magnification will provide useful constraints on the galaxy-mass power spectrum.
We present a spectroscopic survey of almost 15 000 candidate intermediate-redshift luminous red galaxies (LRGs) brighter than i= 19.8, observed with 2dF on the Anglo-Australian Telescope. The targets ...were selected photometrically from the Sloan Digital Sky Survey (SDSS) and lie along two narrow equatorial strips covering 180 deg2. Reliable redshifts were obtained for 92 per cent of the targets and the selection is very efficient: over 90 per cent have 0.45 < z < 0.8. More than 80 per cent of the ∼11 000 red galaxies have pure absorption-line spectra consistent with a passively evolving old stellar population. The redshift, photometric and spatial distributions of the LRGs are described. The 2SLAQ data will be released publicly from mid-2006, providing a powerful resource for observational cosmology and the study of galaxy evolution.
We present a measurement of the K-band luminosity function (LF) of field galaxies obtained from near-infrared imaging of a sample of 345 galaxies selected from the Stromlo-APM Redshift Survey. The LF ...is reasonably well fitted over the 10-mag range −26⩽MK⩽−16 by a Schechter function with parameters α = −1.16±0.19, M* = −23.58±0.42 and φ* = 0.012±0.008 Mpc−3, assuming a Hubble constant of H0 = 100 km s−1 Mpc−1. We have also estimated the LF for two subsets of galaxies subdivided by the equivalent width of the Hα emission line at EW(Hα) = 10 Å. There is no significant difference in LF shape between the two samples, although there is a hint (∼1σ significance) that emission-line galaxies (ELGs) have M* roughly 1 mag fainter than non-ELGs. Contrary to the optical LF, there is no difference in faint-end slope α between the two samples.
We derive the close pair fractions and volume merger rates for galaxies in the Galaxy and Mass Assembly (GAMA) survey with -23 < Mr < ...17 (... = 0.27, ... = 0.73, H... = 100 km s... Mpc...) at 0.01 ...< z < 0.22 (look-back time of <2 Gyr). The merger fraction is approximately 1.5 per cent Gyr... at all luminosities (assuming 50 per cent of pairs merge) and the volume merger rate is ...3.5 x 10... Mpc... Gyr... We examine how the merger rate varies by luminosity and morphology. Dry mergers (between red/spheroidal galaxies) are found to be uncommon and to decrease with decreasing luminosity. Fainter mergers are wet, between blue/discy galaxies. Damp mergers (one of each type) follow the average of dry and wet mergers. In the brighter luminosity bin (-23 < M... < -20), the merger rate evolution is flat, irrespective of colour or morphology, out to z ~ 0.2. The makeup of the merging population does not appear to change over this redshift range. Galaxy growth by major mergers appears comparatively unimportant and dry mergers are unlikely to be significant in the buildup of the red sequence over the past 2 Gyr. We compare the colour, morphology, environmental density and degree of activity (BPT class, Baldwin, Phillips & Terlevich) of galaxies in pairs to those of more isolated objects in the same volume. Galaxies in close pairs tend to be both redder and slightly more spheroid dominated than the comparison sample. We suggest that this may be due to 'harassment' in multiple previous passes prior to the current close interaction. Galaxy pairs do not appear to prefer significantly denser environments. There is no evidence of an enhancement in the AGN fraction in pairs, compared to other galaxies in the same volume. (ProQuest: ... denotes formulae/symbols omitted.)
We present the third edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog. The catalog consists of the 46,420 objects in the SDSS Third Data Release that have luminosities larger than Mi = ...-22 (in a cosmology with H0 = 70 km s-1 Mpc-1, M = 0.3, and = 0.7), have at least one emission line with FWHM larger than 1000 km s-1 or are unambiguously broad absorption line quasars, are fainter than i = 15.0, and have highly reliable redshifts. The area covered by the catalog is 4188 deg2. The quasar redshifts range from 0.08 to 5.41, with a median value of 1.47; the high-redshift sample includes 520 quasars at redshifts greater than 4, of which 17 are at redshifts greater than 5. For each object the catalog presents positions accurate to better than 02 rms per coordinate, five-band (ugriz) CCD-based photometry with typical accuracy of 0.03 mag, and information on the morphology and selection method. The catalog also contains radio, near-infrared, and X-ray emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra cover the wavelength region 3800-9200 A at a spectral resolution of 2000; the spectra can be retrieved from the public database using the information provided in the catalog. A total of 44,221 objects in the catalog were discovered by the SDSS; 28,400 of the SDSS discoveries are reported here for the first time.
We measure the projected correlation function w sub(p) image from the Sloan Digital Sky Survey for a flux-limited sample of 118,000 galaxies and a volume-limited subset of 22,000 galaxies with ...absolute magnitude M sub(r) <-21. Both correlation functions show subtle but systematic departures from the best-fit power law, in particular a change in slope at r sub(p) approx 1-2 h super(-1) Mpc. These departures are stronger for the volume-limited sample, which is restricted to relatively luminous galaxies. We show that the inflection point in w sub(p) image can be naturally explained by contemporary models of galaxy clustering, according to which it marks the transition from a large-scale regime dominated by galaxy pairs in separate dark matter halos to a small-scale regime dominated by galaxy pairs in the same dark matter halo. For example, given the dark halo population predicted by an inflationary cold dark matter scenario, the projected correlation function of the volume-limited sample can be well reproduced by a model in which the mean number of M sub(r) <-21 galaxies in a halo of mass M > M sub(1) = 4.74 x 10 super(13) h super(-1) M sub(o) is image sub(M) = image super(0.89), with 75% of the galaxies residing in less massive, single-galaxy halos and simple auxiliary assumptions about the spatial distribution of galaxies within halos and the fluctuations about the mean occupation. This physically motivated model has the same number of free parameters as a power law, and it fits the w sub(p) image data better, with a Chi super(2)/dof = 0.93, compared to 6.12 (for 10 degrees of freedom, incorporating the covariance of the correlation function errors). Departures from a power-law correlation function encode information about the relation between galaxies and dark matter halos. Higher precision measurements of these departures for multiple classes of galaxies will constrain galaxy bias and provide new tests of the theory of galaxy formation.
The APM Bright Galaxy Catalogue Loveday, Jon
Monthly notices of the Royal Astronomical Society,
02/1996, Letnik:
278, Številka:
4
Journal Article
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The APM Bright Galaxy Catalogue lists positions, magnitudes, shapes and morphological types for 14681 galaxies brighter than bj magnitude 16.44, over a 4180 deg2 area of the southern sky. Galaxy and ...stellar images have been located from glass copy plates of the United Kingdom Schmidt Telescope (UKST) IIIaJ sky survey using the automated photographic measuring (APM) facility in Cambridge, England. The majority of stellar images are rejected by the regularity of their image surface brightness profiles. Remaining images are inspected by eye on film copies of the survey material and classed as stellar, multiple stellar, galaxy, merger or noise. Galaxies are further classified as elliptical, lenticular, spiral, irregular or uncertain. The 180 survey fields are put on to a uniform photometric system by comparing the magnitudes of galaxies in the overlap regions between neighbouring plates. The magnitude zero-point, photometric uniformity and photographic saturation are checked with CCD photometry. Finally, the completeness and reliability of the catalogue are assessed by using various internal tests and by comparison with several independently constructed galaxy catalogues.
We describe the construction of MegaZ-LRG, a photometric redshift catalogue of over one million luminous red galaxies (LRGs) in the redshift range 0.4 < z < 0.7 with limiting magnitude i < 20. The ...catalogue is selected from the imaging data of the Sloan Digital Sky Survey (SDSS) Data Release 4. The 2dF-SDSS LRG and Quasar (2SLAQ) spectroscopic redshift catalogue of 13 000 intermediate-redshift LRGs provides a photometric redshift training set, allowing use of annz, a neural network-based photometric-redshift estimator. The rms photometric redshift accuracy obtained for an evaluation set selected from the 2SLAQ sample is σz= 0.049 averaged over all galaxies, and σz= 0.040 for a brighter subsample (i < 19.0). The catalogue is expected to contain ∼5 per cent stellar contamination. The annz code is used to compute a refined star/galaxy probability based on a range of photometric parameters; this allows the contamination fraction to be reduced to 2 per cent with negligible loss of genuine galaxies. The MegaZ-LRG catalogue is publicly available on the World Wide Web from http://www.2slaq.info.
We measure the redshift-dependent luminosity function and the comoving radial density of galaxies in the Sloan Digital Sky Survey Data Release 1 (SDSS DR1). Both measurements indicate that the ...apparent number density of bright galaxies increases by a factor ≈ 3 as redshift increases from z= 0 to z= 0.3. This result is robust to the assumed cosmology, to the details of the K-correction and to direction on the sky. These observations are most naturally explained by significant evolution in the luminosity and/or number density of galaxies at redshifts z < 0.3. Such evolution is also consistent with the steep number-magnitude counts seen in the Automatic Plate Measuring (APM) Galaxy Survey, without the need to invoke a local underdensity in the galaxy distribution or magnitude scale errors.
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