arXiv subjects

Matthew Colless

Publications and source records attributed to Matthew Colless.

201 records · Page 12Linked to original sources

arXiv1995

THE ABELL CLUSTER INERTIAL FRAME

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.

astro-ph↗

arXiv1994

The Evolution of the Optical Galaxy Luminosity Function -

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.

astro-ph↗

arXiv1994

High-Resolution Imaging of Faint Blue Galaxies

We have used HRCam on the CFHT to obtain subarcsecond images of 26 galaxies with z=0.1--0.7. The primary sample of 17 galaxies have enhanced star formation indicated by [OII] equivalent widths greater than 20Å, while the comparison sample of 9 galaxies have equivalent widths less than 10Å. By fitting disks or bulges to BVI images we derive scalelengths for the blue and red stellar populations and locate the star-formation in each galaxy. These moderate-redshift galaxies generally have straightforward low-redshift analogues, in that their colours, sizes and luminosities are consistent with those of various types of z$\approx$0 galaxies. The star-forming objects have structures consistent with the full range of present-day disk galaxies, and absolute magnitudes M$^\ast$$-$1 to M$^\ast$+5. Some have star-formation concentrated in their nuclei but in most it occurs across the entire disk. We find companions at projected distances closer than 10 kpc for 30% of the star-forming galaxies, whereas none of the comparison sample have such close companions. This provides the first direct evidence linking interactions or mergers to the increased fraction of star-forming field galaxies at moderate redshifts.

astro-ph↗