arXiv subjects

Sarah Brough

Publications and source records attributed to Sarah Brough.

168 records · Page 10Linked to original sources

arXiv2006

Southern GEMS Groups I: Dynamical Properties

Here we present an investigation of the properties of 16 nearby galaxy groups and their constituent galaxies. The groups are selected from the Group Evolution Multi-wavelength Study (GEMS) and all have X-ray as well as wide-field neutral hydrogen (HI) observations. Group membership is determined using a friends-of-friends algorithm on the positions and velocities from the 6-degree Field Galaxy Survey (6dFGS) and NASA/IPAC Extra-galactic Database (NED). For each group we derive their physical properties using this membership, including: velocity dispersions (sigma_v), virial masses (M_V), total K-band luminosities (L_K(Tot)) and early-type fractions (f_early) and present these data for the individual groups. We find that the GEMS X-ray luminosity is proportional to the group velocity dispersions and virial masses: L_X(r_500)\proptoσ_v^{3.11\pm0.59} and L_X(r_500)\propto M_V^{1.13\pm0.27}, consistent with the predictions of self-similarity between group and clusters. We also find that M_V\propto L_K(Tot)^{2.0\pm0.9}, i.e. mass grows faster than light and that the fraction of early-type galaxies in the groups is correlated with the group X-ray luminosities and velocity dispersions. We examine the brightest group galaxies (BGGs), finding that, while the luminosity of the BGG correlates with its total group luminosity, the fraction of group luminosity contained in the BGG decreases with increasing total group luminosity. This suggests that BGGs grow by mergers at early times in group evolution while the group continues to grow by accreting infalling galaxies. (Abridged)

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arXiv2006

Eridanus - A Supergroup in the Local Universe?

We examine a possible supergroup in the direction of the Eridanus constellation using 6dF Galaxy Survey second data release (6dFGS DR2) positions and velocities together with 2MASS and HyperLEDA photometry. We perform a friends-of-friends analysis to determine which galaxies are associated with each substructure before examining the properties of the constituent galaxies. The structure is made up of three individual groups that are likely to merge to form a cluster of mass 7x10^13 Msolar. We conclude that this structure is a supergroup. We also examine the colours, morphologies and luminosities of the galaxies in the region with respect to their local projected surface density. We find that the colours of the galaxies redden with increasing density, the median luminosities are brighter with increasing environmental density and the morphologies of the galaxies show a strong morphology-density relation. The colours and luminosities of the galaxies in the supergroup are already similar to those of galaxies in clusters, however the supergroup contains more late-type galaxies, consistent with its lower projected surface density. Due to the velocity dispersion of the groups in the supergroup, which are lower than those of clusters, we conclude that the properties of the constituent galaxies are likely to be a result of merging or strangulation processes in groups outlying this structure.

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arXiv2006

The Group Evolution Multiwavelength Study (GEMS): the Sample and Datasets

Galaxy groups have been under-studied relative to their richer counterparts -- clusters. The Group Evolution Multiwavelength Study (GEMS) aims to redress some the balance. Here we describe the GEMS sample selection and resulting sample of 60 nearby (distance < 130 Mpc) galaxy groups and our multiwavelength dataset of X-ray, optical and HI imaging. ROSAT X-ray images of each group are presented. GEMS also utilizes near-infrared imaging from the 2MASS survey and optical spectra from the 6dFGS. These observational data are complemented by mock group catalogues generated from the latest LCDM simulations with gas physics included. Existing GEMS publications are briefly highlighted as are future publication plans.

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arXiv2005

Galaxy Groups: Proceedings from a Swinburne University Workshop

We present the proceedings from a 2-day workshop held at Swinburne University on the 24th-25th of May 2005. The workshop participants highlighted current Australian research on both theoretical and observational aspects of galaxy groups. These proceedings include short 1-page summaries of a number of the talks presented at the workshop. The talks presented ranged from reconciling N-body simulations with observations, to the HI content of galaxies in groups and the existence of ``dark galaxies''. The formation and existence of ultra-compact dwarfs in groups, and a new supergroup in Eridanus were also discussed.

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arXiv2001

Evolution of Brightest Cluster Galaxies in X-Ray Clusters

A recent paper (Burke, Collins & Mann 2000) presents the analysis of the K-band Hubble diagram of 76 brightest cluster galaxies (BCGs) in X-ray clusters and shows that the properties of BCGs depend on the X-ray luminosity (Lx) of their host clusters. Unfortunately, the low numbers of nearby clusters in this sample makes it difficult to constrain evolutionary trends. In this letter we extend the Hubble diagram of Burke et al. (2000) to a total of 155 clusters using new data on 79 BCGs at z<0.1 from the 2MASS extended source catalogue. We show that the major division between BCGs in high and low-Lx clusters disappears at z<0.1, with BCGs having similar absolute magnitudes independent of the X-ray luminosity of their host clusters. At larger redshifts the K-band light of BCGs in high-Lx systems is consistent with little or no merging back to z~0.8, whereas BCGs in the low-Lx systems have a different evolutionary history, with many increasing their mass by a factor >4 since z~1. This provides direct evidence of hierarchical merging in a galaxy population.

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arXiv2001

The Properties of Brightest Cluster Galaxies in X-Ray Selected Clusters

We present the K-band Hubble diagram for 162 brightest cluster galaxies (BCGs) in X-ray selected clusters, 0.01<z<0.83. The sample incorporates that of Burke, Collins, & Mann (2000) and includes additional infrared data from the 2MASS extended source catalogue. We show that below z=0.1 the BCGs show no correlation with their environment, however, above z=0.1 BCGs in more X-ray luminous clusters are more uniform in their photometric properties. This suggests that there may be two populations of BCGs which have different evolutionary histories.

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