Software and Sociology in UK Astronomy

I discuss the remit of Starlink's software strategy groups and a particular item on the agenda of a meeting of the image processing software strategy group held on 26th January 2001: `Why don't people use Starlink software?'. The answer to this question was speculated to be primarily a sociological effect: those people supervising UK astronomy Ph.D. students are largely people who had learnt their trade at a time when Starlink had a less than perfect reputation. I report on the recommendations made to Starlink to counter this effect.Comment: 3 pages. Accepted for publication in Astronomy & Geophysics (formerly QJRAS

Pulling out Threads from the Cosmic Tapestry: Defining Filaments of Galaxies

Filaments of galaxies are the dominant feature of modern large scale redshift surveys. They can account for up to perhaps half of the baryonic mass budget of the Universe and their distribution and abundance can help constrain cosmological models. However, there remains no single, definitive way in which to detect, describe and define what filaments are and their extent. This work examines a number of physically motivated, as well as statistical, methods that can be used to define filaments and examines their relative merits.Comment: 12 pages, 6 figures, accepted for publication in PAS

Stellar populations of X-Ray luminous clusters at z = 0.1

This thesis presents new and unique wide-field imaging and spectroscopic observations of 21 X-ray selected rich clusters of galaxies in the redshift range 0.07 < z < 0.16 from the Las Campanas Observatory (LCO) / Anglo-Australian Telescope (AAT) Rich Cluster Survey (LARCS). Mosaic two colour broad-band CCD imaging extending to 10 Mpc at the mean redshift of the survey have been taken at LCO; comprising over 50Gb of raw data. A reduction pipeline is developed for these data and catalogues are constructed for these clusters. Four of these fields are compared to the APM catalogue (Maddox et al. 1990) to confirm their photometric accuracy. In making the comparison several populations of galaxies are discovered to be absent from the APM.A statistical background correction technique is developed to examine the photometric properties of cluster members. Eleven clusters are combined together to investigate environmental trends in the stellar populations of the combined sample. It is found that the modal colours of galaxies lying on the colour-magnitude relation in the clusters become bluer by d (B - R)/dr(_p) = -0.022 ±0.004 with radius or d (B - R)/dlog(_10) (Σ) = -0.076 ± 0.009 with local galaxy density. The 2dF spectroscope at the A AT is used to make spectroscopic follow-up observations of three clusters. A reduction pipeline for these data is developed and redshifts for the galaxies are determined. The spectral catalogues are used to define cluster membership and confirm the photometric environmental trends. Spectral line strengths are used to classify the galaxy population and examine environmental trends across the clusters. The cluster cores are found to be predominantly passive compared to the field. A comparison of the two cluster membership assignment techniques underscores the need for spectroscopy to define the cluster population

The h-index in Australian Astronomy

The Hirsch (2005) h-index is now widely used as a metric to compare individual researchers. To evaluate it in the context of Australian Astronomy, the h-index for every member of the Astronomical Society of Australia (ASA) is found using NASA's Astrophysics Data System Bibliographic Services (ADS). Percentiles of the h-index distribution are detailed for a variety of categories of ASA members, including students. This enables a list of the top ten Australian researchers by h-index to be produced. These top researchers have h-index values in the range 53<h<77, which is less than that recently reported for the American Astronomical Society Membership. We suggest that membership of extremely large consortia such as SDSS may partially explain the difference. We further suggest that many student ASA members with large h-index values have probably already received their Ph.D.'s and need to upgrade their ASA membership status. To attempt to specify the h-index distribution relative to opportunity, we also detail the percentiles of its distribution by years since Ph.D. award date. This shows a steady increase in h-index with seniority, as can be expected.Comment: Accepted for publication in the Publications of the Astronomical Society of Australi

The Large Peculiar Velocity of the cD Galaxy in Abell 3653

We present a catalogue of galaxies in Abell 3653 from observations made with the 2dF spectrograph at the Anglo-Australian Telescope. Of the 391 objects observed, we find 111 are bone-fide members of Abell 3653. We show that the cluster has a velocity of cz = 32214 +/- 83 km/s (z=0.10738 +/- 0.00027), with a velocity dispersion typical of rich, massive clusters of sigma_{cz} = 880^{+66}_{-54}. We find that the cD galaxy has a peculiar velocity of 683 +/- 96 km/s in the cluster restframe - some 7sigma away from the mean cluster velocity, making it one of the largest and most significant peculiar velocities found for a cD galaxy to date. We investigate the cluster for signs of substructure, but do not find any significant groupings on any length scale. We consider the implications of our findings on cD formation theories.Comment: 16 pages, including 7 figures and a long table. Accepted for publication in MNRA

The Rarity of Star Formation in Brightest Cluster Galaxies as Measured by WISE

We present the mid-infrared (IR) star formation rates of 245 X-ray selected, nearby (z<0.1) brightest cluster galaxies (BCGs). A homogeneous and volume limited sample of BCGs was created by X-ray selecting clusters with L_x > 1x10^44 erg/s. The Wide-Field Infrared Survey Explorer (WISE) AllWISE Data Release provides the first measurement of the 12 micron star formation indicator for all BCGs in the nearby Universe. Perseus A and Cygnus A are the only galaxies in our sample to have star formation rates of > 40 M_sol/yr, indicating that these two galaxies are highly unusual at current times. Stellar populations of 99 +/- 0.6 % of local BCGs are (approximately) passively evolving, with star formation rates of <10 M_sol/yr. We find that in general, star formation produces only modest BCG growth at the current epoch.Comment: 5 pages, 3 figures, accepted for publication in MNRA

An accurate new method of calculating absolute magnitudes and K-corrections applied to the Sloan filter set

We describe an accurate new method for determining absolute magnitudes, and hence also K-corrections, which is simpler than most previous methods, being based on a quadratic function of just one suitably chosen observed color. The method relies on the extensive and accurate new set of 129 empirical galaxy template SEDs from Brown et al. (2014). A key advantage of our method is that we can reliably estimate random errors in computed absolute magnitudes due to galaxy diversity, photometric error and redshift error. We derive K-corrections for the five Sloan Digital Sky Survey filters and provide parameter tables for use by the astronomical community. Using the New York Value-Added Galaxy Catalog we compare our K-corrections with those from kcorrect. Our K-corrections produce absolute magnitudes that are generally in good agreement with kcorrect. Absolute g, r, i, z-band magnitudes differ by less than 0.02 mag, and those in the u-band by ~0.04 mag. The evolution of rest-frame colors as a function of redshift is better behaved using our method, with relatively few galaxies being assigned anomalously red colors and a tight red sequence being observed across the whole 0.0 < z < 0.5 redshift range.Comment: 23 pages, 16 figure

Multiscale probability mapping: groups, clusters and an algorithmic search for filaments in SDSS

We have developed a multiscale structure identification algorithm for the detection of overdensities in galaxy data that identifies structures having radii within a user-defined range. Our "multiscale probability mapping" technique combines density estimation with a shape statistic to identify local peaks in the density field. This technique takes advantage of a user-defined range of scale sizes, which are used in constructing a coarse-grained map of the underlying fine-grained galaxy distribution, from which overdense structures are then identified. In this study we have compiled a catalogue of groups and clusters at 0.025 < z < 0.24 based on the Sloan Digital Sky Survey, Data Release 7, quantifying their significance and comparing with other catalogues. Most measured velocity dispersions for these structures lie between 50 and 400 km/s. A clear trend of increasing velocity dispersion with radius from 0.2 to 1 Mpc/h is detected, confirming the lack of a sharp division between groups and clusters. A method for quantifying elongation is also developed to measure the elongation of group and cluster environments. By using our group and cluster catalogue as a coarse-grained representation of the galaxy distribution for structure sizes of <~ 1 Mpc/h, we identify 53 filaments (from an algorithmically-derived set of 100 candidates) as elongated unions of groups and clusters at 0.025 < z < 0.13. These filaments have morphologies that are consistent with previous samples studied.Comment: 22 pages, 14 figures and 6 tables. Accepted for publication in MNRAS. Data products, three-dimensional visualisations and further information about MSPM can be found at http://www.physics.usyd.edu.au/sifa/Main/MSPM/ . v2 contains two additional references. v3 has a slightly altered title and updated reference