IAN SMAIL

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PREVIOUS RESEARCH PROJECTS

This page contains a description of some of the previous research programmes which I have undertaken. A selection of older images used in two Astronomy Magazine articles are shown here. Any recent press release information will be found here. This page also includes links to a few other pictures I've made along the way. A few useful rules for operating in this field are given on this page.



SCUBA and Star-formation in Distant Galaxies

This project was a collaboration between myself, Rob Ivison, Andrew Blain and Jean-Paul Kneib. We used SCUBA, the new sub-mm bolometer array on the 15-m JCMT on Mauna Kea to make the first sub-mm maps of the distant Universe. These have been used to study the star-formation properties of distant galaxies seen through the cores of rich clusters. These galaxies are seen in the sub-mm because the dust within them is reprocessing UV and optical star-light and emitting large quantities of radiation in the sub-mm. Thus sub-mm maps allow us to estimate the typical star-formation rate in the distant Universe and hence search for the epoch of galaxy formation. The first observations for this were taken in the late summer of 1997 and the results from those are discussed in this paper. The final survey covered a total area of 0.01 sq. degrees and we published papers on the brightest source in our sample, the constraints on the star-formation history of the Universe from our sub-mm counts (see also here), the implications of our counts for observations with the next generation of sub-mm and CMB experiments (here), and the optical morphologies and colors of the faint sub-mm population using HST data. Further papers in this series deal with the sub-mm counts from our complete survey, the detection in CO of the brightest sub-mm galaxy we have identified, the sub-mm emission from central cluster galaxies, the redshift distribution of galaxies selected in the sub-mm (from the optical and radio) and the discovery of extremely red counterparts to a modest number of sub-mm sources. A complete list of the publications arising from this project is given on this page.



Lensing and the Nature of Distant Galaxies

These projects rely on the dependence of the shear induced in all background galaxies seen through a rich cluster on both the mass in the lensing cluster and the galaxy's distance. Using deep HST imaging we can construct a detailed model of the mass distribution within the cluster and hence use this to predict the redshifts of large samples of background field galaxies. The method is purely geometrical and only requires that we can measure the shape of the distant galaxy, it thus can be successfully applied to galaxies > 10× fainter than conventional techniques. We have applied this technique to the rich cluster A2218 and confirmed our predicted redshifts using spectroscopic observations of the brighter arclets. Jean-Paul Kneib, Harald Ebeling, Graham Smith and I expanded this analysis with Cycle 8 time to provide the first statistically reliable sample of around a dozen luminous X-ray clusters at z~0.2 all imaged with WFPC2 (based on the Magic-24 sample). This project became the basis of Graham Smith's thesis and his subsequent LoCUSS project.

In addition to the HST observations, this sample was also observed in the X-ray with XMM and imaged in the optical over 0.5 degree fields with the CFH12k camera on CFHT. We also obtained spectroscopic observations of the brighter lensed features and the cluster galaxies. These can be used to compare and contrast the properties of these clusters and their galaxy populations with those of the substantially lower-richness clusters also being studied with HST (see here).



The Evolution of Galaxies as a Function of Environment

The first part of this program relates to the fundamental plane of galaxies at z=0.2. This was a Durham-led project with Richard Bower and Michael Balogh. We upgraded the capabilities of the LDSS-2 spectrograph on the 4.2-m WHT, La Palma (now moved to the Magellan 6.5-m in Chile), to enable us to use it to obtain intermediate resolution spectroscopy of large samples of galaxies in z~0.2 clusters. This project also used the charge-shuffling mode of the newly refurbished LDSS++ on the 3.9-m AAT to observe a small sample of galaxies in a cluster at z=0.31 and was published here. We hope to expand these observations to compile a sample of galaxies at z=0.3 similar to our z~0.2 catalog.

The second aspect of this program is a similarly detailed study of galaxies in low-density environments at z~0.2 using X-ray selected poor clusters and groups. The core science is based on a sample of nine clusters for which deep imaging with HST obtained during Cycle 8. This compliments the second phase of the MORPHS project which is also using HST to look at the properties of galaxies in the low-density outskirts of very rich clusters. We hope to use the variation of galaxy properties, both star-forming and passive, between the low-density groups and the higher-density clusters to search for the physical mechanisms responsible for the rapid evolution of the galaxy populations within clusters. An extension of this project to a sample at z=0.5 is underway.



MORPHS

This project aimed at understanding the evolution of galaxies in high density environments (rich clusters) over the last 5-8 Gyrs. We combine deep Hubble Space Telescope WFPC2 pointings of the clusters to determine galaxy morphology with multi-object spectroscopy of the same galaxies taken with the 5.1-m Hale, 4.2-m WHT, 3.9-m AAT and 3.6-m NTT telescopes. A spectroscopic catalog of roughly 700 galaxies in the 10 clusters is also available. The project has now moved to its second phase where we are extending our study into the outskirts of the clusters to tie the evolution in the cluster and field populations together. We are also using narrow-band imaging to investigate the distribution of emission-line galaxies within the clusters, medium resolution spectroscopy of the early-type galaxies to search for traces of past star-formation and deep radio maps to uncover evidence for dusty starburst galaxies. The main collaborators involved in this work are: Warrick Couch, Alan Dressler, Richard Ellis, Gus Oemler, Bianca Poggianti and myself. The complete catalogs of objects detected in our WFPC2 images, as well as information on the morphologies of a brighter subset are available from here, while the spectral catalog for these clusters is on this page Images of a few of the clusters are shown here. A number of the papers produced by this group are already published.



CIRCuS and the LCO/2dF Rich Cluster Study

Moving to even lower redshifts, this was a long term project to study a statistically reliable sample of the richest clusters in the southern hemisphere in a redshift slice between z=0.07-0.15. The project included wide-field (2×2 degree) B and R imaging from the 40" telescope at Las Campanas Observatory (Chile) of over 20 clusters, totalling over 70 square degrees of sky. These images were used to select galaxies for subsequent spectroscopic follow-up with the 400-fibre 2dF multi-object spectrograph on the 3.9m AAT in Australia. The aim was to obtain spectra for significant samples of galaxies in a subset of the clusters to provide an unprecedented view of the dynamics of rich clusters and their galaxy populations (see here). The collaborators in this program are Warrick Couch, Alastair Edge, Eileen O'Hely, Kevin Pimbblet, Ann Zabludoff and me. A true color image of the central regions of one of our clusters is shown here.



Bits-n-Bobs

A few spin-off projects (some using data taken for other purposes by other people and some using data taken by other people for the same purpose). To save trees my to-do list is here.

  • Several projects to study the formation and evolution of elliptical and S0 galaxies in distant clusters. These include a detailed spectroscopic analysis of morphologically-classified E/S0 galaxies in clusters at z=0.3-0.6 and a gravitational lensing survey to investigate possible differences between the dark matter halos of elliptical and S0 galaxies within clusters at z=0.2-0.3.

  • Maybe when I get around to it - something to see how weird the Universe is, even locally (see here):
    ``A Catalogue of Morphologies for Dwarf Galaxies in the Coma Cluster'', Smail, I., Lucey, J.R., Davies, R.L., de Jong, R., Smith, R.J., 20xx, in imagination.

  • Yet more galaxy-galaxy lensing to study the extended dark matter halos of galaxies, with Tereasa Brainerd. This time we're using Hubble Space Telescope images to improve the signal-to-noise of the test.

    And I hope you've noticed that I'm quite definitely not doing anything on intra-cluster light... although I can advise on this topic.