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Search Results: 1 - 10 of 10620 matches for " Matthew Colless "
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THE ABELL CLUSTER INERTIAL FRAME
Matthew Colless
Physics , 1995, DOI: 10.1086/117419
Abstract: A re-analysis of Lauer \& Postman's (1994; LP) finding that the Abell cluster inertial frame (ACIF), defined by the 119 Abell clusters within 15,000 km/s, is moving at almost 700 km/s with respect to the cosmic microwave background. Such a motion is inconsistent with most cosmological models at a confidence level of 95% or higher. We obtain an exact expression for a cluster's peculiar velocity in terms of the residual magnitude about the mean relation between the metric luminosity of brightest cluster galaxies and the slope of their luminosity profiles. We compare this to the approximation used by LP. We develop a maximum likelihood procedure for recovering the Local Group motion from the scatter in this relation which yields an unbiased estimate for the motion with significantly smaller uncertainties than LP's method. We re-analyse LP's data and find that the Local Group is moving relative to the ACIF at 626 (+/-242) km/s towards l=216, b=-28 (+/-20). This implies that the ACIF is itself moving relative to the cosmic microwave background at 764 (+/-160) km/s towards l=341, b=49 (+/-20). This motion is consistent with that derived by LP but has a 10% larger amplitude and 20% smaller errors, making it even harder to reconcile with cosmological models.
A New Vision of the Coma Cluster: Conference Summary
Matthew Colless
Physics , 1997,
Abstract: Summary of the highlights and main themes of a conference on the Coma cluster, "A New Vision of an Old Cluster: Untangling Coma Berenices".
First results from the 2dF galaxy redshift survey
Matthew Colless
Physics , 1998, DOI: 10.1098/rsta.1999.0317
Abstract: The 2dF Galaxy Redshift Survey is a major new initiative to map a representative volume of the universe. The survey makes use of the 2dF multi-fibre spectrograph at the Anglo-Australian Telescope to measure redshifts for over 250,000 galaxies brighter than B=19.5 and a further 10,000 galaxies brighter than R=21. The main goals of the survey are to characterise the large-scale structure of the universe and quantify the properties of the galaxy population at low redshifts. This paper describes the design of the survey and presents some preliminary results from the first 8000 galaxy redshifts to be measured.
The Evolution of the Optical Galaxy Luminosity Function -
Matthew Colless
Physics , 1994,
Abstract: The optical luminosity function is a fundamental characterization of the galaxy population. A combination of earlier redshift surveys with two new surveys allows the first accurate determination of the evolution of the luminosity function with redshift, and reveals a marked steepening of the faint end slope. This effect is more profound for star-forming galaxies - there are 5-10 times as many star-forming galaxies at z~0.5 as there are locally. These results, together with high-resolution imaging and linewidth velocity measurements, support the view that the excess of star-forming galaxies at moderate redshift represents a general increase in the star-formation rate of normal galaxies rather than a distinct new population. This increase in star-formation appears in lower-L galaxies at lower redshift and only appears in L* galaxies at z>0.5. Imaging studies provide indirect evidence which suggests that interactions are responsible for a large part of this increased activity.
Wide Field Spectroscopy and the Universe
Matthew Colless
Physics , 1996,
Abstract: In this short survey of the applications of wide-field, multi-object spectroscopy to galaxy evolution, large-scale structure and cosmology, I interleave summaries of the general goals and state of play in these fields with specific examples based on my own recent work. I first briefly review the goals and figures of merit for current and future redshift surveys, before examining some recent results from deep surveys in the field, cluster redshift surveys and surveys of large scale structure. I take a look beyond redshift surveys to other probes of galaxy evolution before concluding with a discussion of the future prospects for such studies using the next generation of wide-field, multi-object spectrographs on large telescopes.
Cosmological results from the 2dF Galaxy Redshift Survey
Matthew Colless
Physics , 2003,
Abstract: The 2dF Galaxy Redshift Survey (2dFGRS) has produced a three-dimensional map of the distribution of 221,000 galaxies covering 5% of the sky and reaching out to a redshift z=0.3. This is first map of the large-scale structure in the local Universe to probe a statistically representative volume, and provides direct evidence that the large-scale structure of the Universe grew through gravitational instability. Measurements of the correlation function and power spectrum of the galaxy distribution have provided precise measurements of the mean mass density of the Universe and the relative contributions of cold dark matter, baryons, and neutrinos. The survey has produced the first measurements of the galaxy bias parameter and its variation with galaxy luminosity and type. Joint analysis of the 2dFGRS and cosmic microwave background power spectra gives independent new estimates for the Hubble constant and the vacuum energy density, and constrains the equation of state of the vacuum.
Redshift Surveys and Cosmology
Matthew Colless
Physics , 1999,
Abstract: Redshift surveys are one of the prime tools of observational cosmology. Imaging surveys of the whole sky are now available at a wide range of wavelengths, and provide a basis for the new generation of massive redshift surveys currently in progress. The very large datasets produced by these surveys call for new and sophisticated approaches to the analysis of large-scale structure and the galaxy population. These issues, and some preliminary results from the new redshift surveys, were discussed at the second Coral Sea Cosmology Conference, held at Dunk Island on 24-28 August 1999. This is a summary of the conference; the full conference proceedings are on the WWW at http://www.mso.anu.edu.au/DunkIsland/Proceedings .
Some Effects of Galaxy Structure and Dynamics on the Fundamental Plane
Alister Graham,Matthew Colless
Physics , 1997, DOI: 10.1093/mnras/287.1.221
Abstract: We examine the effects on the Fundamental Plane (FP) of structural departures from an R^{1/4} galaxy light profile. We also explore the use of volumetric as well as projected galaxy parameters. We fit the Sersic R^{1/n} law to the V-band light profiles of 26 Virgo ellipticals, where `n' is a shape parameter that allows for structural differences amongst the profiles. The galaxy light profiles show a trend of systematic departures from a de Vaucouleurs R^{1/4} law, in the sense that `n' increases with increasing effective half-light radius R_{e}. Adjustments to the measured velocity dispersion are also made, based upon the theoretical velocity dispersion profile shapes of the different R^{1/n} light profiles. We find that allowing for broken structural homology through fitting R^{1/n} profiles, but still using central velocity dispersions, actually increases the departure of the observed FP from the virial plane - the increase in effective radius with galaxy luminosity (and `n') is over-balanced by an associated decrease in the mean surface brightness. In examining the use of volumetric quantities and allowing for the different velocity dispersion profiles corresponding to the observed light profiles, we find that use of the volumetric velocity dispersion at the volumetric half-light radius decreases the departure of the FP from the virial plane. Through use of the Jeans hydrodynamical equation, we further convert the projected central aperture velocity dispersion, sigma_{0}, into the infinite aperture velocity dispersion, sigma_{tot,n} (which is equal to one-third of the virial velocity dispersion). Using both the R^{1/n} fit parameters and sigma_{tot,n} we obtain for the FP, R_{e,n}~sigma_{tot,n}^{1.44+/-0.11}Sigma_{e,n}^{-0.93+/-0.08}, where R_{e,n} and Sigma_{e,n} are the radius and surface brightness terms.
Redshift Surveys with 2dF
Matthew Colless,Brian Boyle
Physics , 1997,
Abstract: We report on the 2dF Galaxy and QSO Redshift Surveys now in progress with the Two Degree Field facility at the Anglo-Australian Observatory. We describe the 2dF instrumentation, outline the scientific aims of the surveys and their current status, and present some initial results.
MAXIMUS: Exploiting the Full Power of OzPoz
Matthew Colless,Keith Taylor
Physics , 2001, DOI: 10.1007/10857019_15
Abstract: We propose a new multi-object spectrograph for the VLT. MAXIMUS (MAXimum MUltiplex Spectrograph) will fully exploit the multiplexing capabilities of the OzPoz fibre positioner in order to extend and complement FLAMES and VIMOS in covering observational parameter space, and to meet the increasing demand for multi-object spectroscopy by ESO users in the next decade.
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