This page gives brief summaries of the main areas covered in my research. More details about some of my current projects can be found on this page.
My research interests fall into three main areas: studying the most active phases of galaxy formation and evolution using obscured galaxies at high redshifts, understanding the growth of groups and clusters of galaxies structure through mapping their dark matter with gravitational lensing, and investigating the influence of environment on the evolution of galaxies by contrasting the properties and evolutionary histories of galaxies in high-density regions such as clusters with those in the low-density field.
Vigorously star forming galaxies are characterised by large quantities of dust , this absorbs light from stars and reprocesses it into the far-infrared (50-200um). Thus the most active galaxies in the local Universe have very high far-infrared/optical ratios, compared to more `normal' galaxies such as the Milky Way and are a major constituent of space-based surveys in the far-infrared (these are impossible from the ground as the atmosphere is opaque at these wavelengths). However, it was only with the advent of the SCUBA submm camera on the James Clerk Maxwell Telescope on Hawaii, that we had the capability to search for similar systems at higher redshifts, where the restframe far-infrared emission is redshifted into the submm waveband. Such dusty, luminous galaxies were expected to be a major component of the galaxy population in the early Universe as young galaxies should be actively forming stars.
I was lucky to be a member of a small team of young researchers who had the opportunity to obtain the first deep submm maps with SCUBA  when the detector we were scheduled to use on the JCMT failed. We obtained maps of the core regions of two massive clusters of galaxies and detected a total of five sources, this survey was subsequently expanded to cover seven clusters and yielded a sample of 15 background submm galaxies . The most recent cluster lens field to be observed has yielded a striking giant arc of an intrinsically faint submm galaxy, underlining the usefulness of lensing as a tool for such surveys .
Initial follow-up of these fields using deep, archival HST optical imaging  and Keck spectroscopy  suggested that many of these sources had optically bright counterparts. However, subsequent work use very sensitive radio maps , deep near-infrared imaging [7, 35] and millimeter interferometry  has revised this view to the point where we believe over half of the population are so faint in the optical that they are difficult to detect in even the deepest images, although 25% of these may appear as Extremely Red Objects (EROs) in the near-infrared. The ERO population has long been thought to contain examples of dusty starburst [9,10] and AGN .
While many of the submm galaxies are faint in the optical, prompting suggestions of new techniques to learn more about their properties , a few examples are sufficiently bright that they can be studied using large ground-based telescopes. These detailed studies have yield important insights into the nature of the faint submm population [13,14,15,16,17,18], including the source of the immense luminosities of these systems, their masses and gas fractions [19,20]. These observations suggest that the submm galaxies are massive, gas-rich systems which are forming stars at a rate of 1000's Mo/yr over a region 10-kpc in extent . Although a small fraction may be artificially boosted by foreground galaxy-scale lenses [21,33], or represent less-luminous, but colder galaxies at lower redshifts .
We have has worked to interpret the properties of these galaxies and place them within the framework of models for galaxy formation and evolution [23,24]. This work suggests that the submm population may contain the bulk of the massive star formation at high redshifts, and that this is almost completely hidden in the optical and UV [25,26]. We have also worked on the relation between the submm population and other classes of high-redshift sources such as X-ray selected AGN  or mid-infrared sources [38 ,39 ,40], as well as the observational opportunities of future surveys , with second-generation instruments such as SCUBA-2.
My most recent work on the submm population has concentrated in part on targetted surveys of regions around known high-redshift sources, Quasars or luminous radio galaxies , to search for overdensities of submm sources which may mark the cores of proto-clusters in the process of collapse [29,30,43]. This project has proved successful and we are actively expanding the survey to provide a more representative view of the highest density regions in the early Universe , and the relationship between submm galaxies and other classes of high-redshift galaxy and AGN .
The other focus of my recent work has been to exploit the precise
positions for a large fraction of the brightest SCUBA galaxies
available from deep radio maps , combined with
the massive light-grasp of 10-m class telescopes, to undertake the
first large spectroscopic surveys of this population . This has facilitated the first reliable measurement
of the spatial clustering of these galaxies, confirming that they
are strongly clustered, as expected if they are truly massive
galaxies [41, 36].
1) ``Submillimeter Imaging of the Luminous Infrared Galaxy Pair VV114'', Frayer et al. (1999)
2) ``A Deep Sub-millimeter Survey of Lensing Clusters: A New Window on Galaxy Formation and Evolution'', Smail, Ivison & Blain (1997)
3) ``Deep Counts of Submillimetre Galaxies'', Blain et al. (1999)
4) ``Faint Sub-mm Galaxies: HST Morphologies and Colors'', Smail et al. (1998)
5) ``Redshift Distribution of the Faint Submillimeter Galaxy Population'', Barger et al. (1999)
6) ``Radio Constraints on the Identifications and Redshifts of Submm Galaxies'', Smail et al. (2000)
7) ``The Discovery of ERO Counterparts to Faint Submm Galaxies'', Smail et al. (1999)
8) ``The Identification of the Sub-millimeter Galaxy SMM J00266+1708'', Frayer et al. (2000)
9) ``Observations of a z=1.44 Dusty, Ultraluminous Galaxy and Implications for Deep Sub-mm Surveys'', Dey et al. (1999)
10) ``The Diversity of Extremely Red Objects'', Smail et al. (2002)
11) ``The Nature of X-ray Selected EROs'', Stevens et al. (2003)
12) ``Gigamasers: The Key to the Dust-obscured Star-formation History of the Universe?'', Townsend et al. (2001)
13) ``A Hyperluminous Galaxy at z=2.8 Found in a Deep Submillimetre Survey'', Ivison et al. (1998)
14) ``The Diversity of SCUBA-selected Galaxies'', Ivison et al. (2000)
15) ``Locating the Starburst in the SCUBA Galaxy SMMJ14011+0252'', Ivison et al. (2001)
16) ``GMOS Spectroscopy of SCUBA galaxies behind A851'', Ledlow et al. (2002)
17) ``A Vigorous Starburst in the SCUBA Galaxy N2 850.4'', Smail et al. (2003)
18) ``The z=2.51 Extremely Red Submillimeter Galaxy SMMJ04431+0210'', Frayer et al. (2003)
19) ``Molecular Gas in the z=2.8 Submillimeter Galaxy SMM02399-0136'', Frayer et al. (1998)
20) ``Molecular Gas in the z=2.565 Submillimeter Galaxy SMMJ14011+0252'', Frayer et al. (1999)
21) ``The Effect of Lensing on the Identification of Bright SCUBA Galaxies'', Chapman et al. (2002)
22) ``Optically Faint Counterparts to the ISO-FIRBACK 170um Population: The Discovery of Cold, Luminous Galaxies at High Redshift'', Chapman et al. (2002)
23) ``The History of Star Formation in Dusty Galaxies'', Blain et al. (1999)
24) ``Dust Obscured Star Formation and AGN Fueling in Hierarchical Models of Galaxy Formation'', Blain et al. (1999)
25) ``The Nature of Faint Submillimetre-selected Galaxies'', Smail et al. (2002)
26) ``Submillimetre Galaxies'', Blain et al. (2002)
27) ``Testing the connection between the X-ray and submillimetre source populations using Chandra'', Fabian et al. (2000)
28) ``Observational Limits to Source Confusion in the Millimetre/Submillimetre Waveband'', Blain, Ivison & Smail (1998)
29) ``An Excess of Submm Sources Near 4C41.17: A Candidate Proto-cluster at z=3.8?'', Ivison et al. (2000)
30) ``A SCUBA galaxy in the Protocluster around 53W002 at z=2.4'', Smail et al. (2003)
31) ``Deep Radio Imaging of the 8-mJy Survey Fields: Submm Source Identifications and Redshift Distribution'', Ivison et al. (2002)
32) ``A Median Redshift of 2.4 for Galaxies Bright at Submillimetre Wavelengths'', Chapman et al. (2003)
33) ``Discovery of the Host Galaxy of HDF850.1, the Brightest Sub-mm Source in the Hubble Deep Field'', Dunlop et al. (2004)
34) ``A Multiply-Imaged, Submillimetre-Selected ULIRG in a Galaxy Group at z=2.51'', Kneib et al. (2004)
35) ``Near-infrared Colors of Submillimeter-selected Galaxies'', Frayer et al. (2004)
36) ``The Restframe Optical Properties of SCUBA Galaxies'', Smail et al. (2004)
37) ``Evidence for Extended, Obscured Starbursts in Submm Galaxies'', Chapman et al. (2004)
38) ``Accurate SEDs and Selection Effects for High-redshift Dusty Galaxies: A New Hot Population to Discover with Spitzer?'', Blain et al. (2004)
39) ``Spitzer Observations of MAMBO Galaxies: Weeding Out Active Nuclei in Starbursting Proto-ellipticals'', Ivison et al. (2004)
40) ``A Population of Hot, Dusty Ultra-luminous Galaxies at z~2'', Chapman et al. (2004)
41) ``Clustering of Submillimeter-Selected Galaxies'', Blain et al. (2004)
42) ``Extended X-ray Emission around 4C41.17 at z=3.8'', Scharf et al. (2003)
43) ``The Formation of Cluster Elliptical Galaxies as Revealed by Extensive Star Formation'', Stevens et al. (2003)
44) ``A Filamentary Structure of Massive, Star-Forming Galaxies Associated with an X-ray Absorbed QSO at z=1.8'', Stevens et al. (2004)
45) ``Chandra Detections of SCUBA Galaxies around High-z Radio Sources'', Smail et al. (2003)
Gravitational LensingMy PhD thesis covered various aspects of gravitational lensing by massive clusters of galaxies. The first project involved spectroscopic observations of a giant arc in Abell 963, these confirmed that the arc represented a highly distorted (and magnified) image of a background star-forming galaxy at z=0.77 . I followed that up with an analysis of archival images of distant clusters from the Danish 1.5-m telescope at La Silla (taken for an early high-redshift supernova survey) to search for gravitationally-lensed arcs and arclets . This turned out to be only moderately successful, in part because the clusters surveyed were not particularly massive and X-ray luminous, but mostly because of the limited spatial resolution available from ground-based imaging - which makes identification of lensed features difficult, although that isn't to say I've given up trying .
However, it is the high-resolution imaging available from Hubble Space Telescope which is essential for successful lens surveys [4,10,15]. HST is also invaluable for studying the properties of the arcs, such as their morphologies, internal structure, colours and most recently dynamics, in much more detail [5,6,24] than is possible from the ground . HST also provides unique opportunities to exploit gravitational lensing to undertake sensitive surveys for high-redshift sources, such as supernova .
My thesis dealt with two aspects of gravitational lensing: i) the use of lenses to estimate the redshift distribution of distant field galaxies and ii) weak shear reconstructions of the mass distributions in cluster lenses.
Lenses can be used to estimate the redshift distribution of the background field population by comparing the strength of the distortion imprinted on the galaxy shapes by cluster lenses with similar masses at different redshifts. At its simplest, if a lens at redshift z and is beyond the bulk of the faint field population then the average distortion induced in the field population will be lower than for an equivalent mass lens at lower z, . Unfortunately, the strength of the lensing signal will also appear lower if the more distant cluster is less massive than the lower redshift one - a not unreasonable expectation given that clusters are believed to grow significantly over the redshift range populated by faint field galaxies, z=0-1.
This technique has also benefited from the use of HST, which along with detailed mass models of cluster lenses (constrained by the geometry of multiply-imaged arcs identified in the core of the clusters), allow us to not only estimate the statistical redshift distribution for the field population, a factor of 10× fainter than is possible from classical spectroscopy with even 10-m telescope , but also predict the redshifts for individual arclets to 10-30% precision . We subsequently confirmed the accuracy of this new technique for the brighter arclets which are within the reach of classical spectroscopy [12,13].
The other field which I have tackled with lensing is measuring the mass of clusters and mapping the distribution of dark matter within them . Again HST has been a great benefit for this work, allowing me to study a wider range of cluster masses , across a wider field of view  at higher redshifts [17,18] and with better resolution than is possible from the ground [16,26]. The mass distributions derived in this way can be compared and contrasted to those assumed for X-ray analyses of cluster mass distributions [26,27]. Testing the assumptions used by the X-ray analyses is particularly important when these are used to infer constraints on cosmological parameters 
Finally, weak lensing studies can be extended beyond rich clusters
to study the mass distribution on the largest scales in the Universe
, as well as providing unique insights into the
nature of dark matter  as well as the
properties of the
dark matter halos of galaxies and their variation with environment,
epoch and morphology [21,22,23].
of Arcs in the Rich Cluster Abell 963'', Ellis, Allington-Smith & Smail (1991)
2) ``A Statistically-Complete Survey for Arc-like Features in Images of Distant Rich Clusters of Galaxies'', Smail et al. (1991)
3) ``The Discovery of Two Giant Arcs in the Rich Cluster A2219 with the Keck Telescope'', Smail et al. (1995)
4) ``HST Observations of Gravitationally Lensed Features in the Rich Cluster AC114'', Smail et al. (1995)
5) ``HST Observations of Giant Arcs: High Resolution Imaging of Distant Field Galaxies'', Smail et al. (1996)
6) ``Two Multiply-imaged z=4.05 galaxies in the cluster-lens Abell 2390'', Pello et al. (1999)
7) ``The Nature of Star Formation in Lensed Galaxies at High Redshift'', Smail et al. (1993)
8) ``A Strategy for Finding Gravitationally Lensed Distant Supernovae'', Sullivan et al. (2000)
9) ``Gravitational Lensing of Distant Field Galaxies by Rich Clusters: I. Faint Galaxy Redshifts'', Smail, Ellis & Fitchett (1994)
10) ``VLT Spectroscopy of Galaxies Lensed by AC114: Implication for the Mass Model and the Study of Low-Luminosity Galaxies at High Redshift'', Campusano et al. (2001)
11) ``Hubble Space Telescope Observations of the Rich Cluster of Galaxies Abell 2218'', Kneib et al. (1996)
12) ``Identification of a Gravitationally Lensed z=2.515 Star-Forming Galaxy'', Ebbels et al. (1996)
13) ``Spectroscopic Confirmation of Redshifts Predicted by Gravitational Lensing'', Ebbels et al. (1998)
14) ``Gravitational Lensing of Distant Field Galaxies by Rich Clusters: II. Cluster Mass Distributions'', Smail et al. (1995)
15) ``A Comparison of Direct and Indirect Mass Estimates for Distant Clusters of Galaxies'', Smail et al. (1997)
16) ``An HST Lensing Survey of X-ray Luminous Clusters: I. A383'', Smith et al. (2001)
17) ``Lensing by Distant Clusters: HST Observations of Weak Shear in the Field of 3C324'', Smail & Dickinson (1995)
18) ``A Weak Lensing Survey in the Fields of z~1 Luminous Radio Sources'', Bower & Smail (1997)
19) ``A Search for Weak Distortion of Distant Galaxy Images by Large Scale Structure'', Mould et al. (1994)
20) ``Constraints on the Collisional Nature of the Dark Matter from Gravitational Lensing in the Cluster A2218'', Natarajan et al. (2002)
21) ``Weak Gravitational Lensing by Galaxies'', Brainerd, Blandford & Smail (1996)
22) ``The Mass/Light Ratio of Early-type Galaxies: Constraints from Gravitational Lensing in the Rich Cluster AC114'', Natarajan et al. (1998)
23) ``Evidence for Tidal Stripping of Dark Matter Halos in Massive Cluster-Lenses'', Natarajan, Kneib & Smail (2002)
24) ``Galaxies Under the Cosmic Microscope: A GMOS Study of the Lensed Galaxy #289 in A2218'', Swinbank et al. (2003)
25) ``A Wide Field Hubble Space Telescope Survey of the Cluster Cl0024+16 at z=0.4. II: The Cluster Mass Distribution'', Kneib et al. (2003)
26) ``A Hubble Space Telescope Lensing Survey of X-ray Luminous Galaxy Clusters: IV. Mass, Structure and Thermodynamics of Cluster Cores at z=0.2'', Smith et al. (2004)
27) ``An XMM-Newton Survey of X-ray Luminous Galaxy Clusters: I. Spectro-Imaging Analysis of Abell 209'', Marty et al. (2004)
28) ``Measuring Sigma-8 with Cluster Lensing: Biases from Unrelaxed Clusters'', Smith et al. (2003)
of Arcs in the Rich Cluster Abell 963'', Ellis, Allington-Smith & Smail (1991)
Deep lensing surveys through massive clusters also yield high-quality information on the galaxies residing within the clusters [1,2]. This makes surveys of rich clusters a particularly fruitful area of research, especially when HST imaging is obtained as part of the programme [3,4]. These data, combined with spectroscopic information, can be analysed to investigate the effects of environment on galaxy characteristics and their evolution [6,7,28].
One project which has exploited deep HST of rich clusters to investigate the properties of the cluster galaxies is the MORPHS project [5,6]. The MORPHS group obtained HST imaging of 10 clusters at z > 0.37 and analysed these to provide morphological information on roughly 2000 galaxies in these fields. This influential project has produced unique constraints on a variety of cluster-related issues, including the photometric, spectroscopic and morphological evolution of cluster galaxies [7,8].
The most striking discovery from the MORPHS project deal with the evolution of the early-type galaxies which dominate the cluster population. Morphologically classified samples show a steep decline in the proportion of lenticular (S0, galaxies with a large bulge component and a weak disk) to elliptical galaxies (systems consisting almost entirely of bulge stars) out to z=0.5 . Taken together with the expectation that elliptical galaxies are old, high-evolved systems [7,8,27], this suggests that the lenticular galaxies were formed relatively recently (or more likely transformed from a different morphological class). This suggestion has provoked a lively debate [12,13,14], and various interpretations . The existence of morphological evolution in rich clusters is in little doubt, however the nature of the processes which drives it is still an open question.
My most recent work on the properties and evolution of galaxies in high density environments has focused on testing the evolution of galaxies outside the highest density (core) regions probed by HST surveys [16,17]. By following the changing properties of galaxies (colour, star-formation rate or morphology) from the core out to the edge of the cluster (where it blends into the overall large-scale structure) we can test different environmental processes which have been proposed [18,19,20,21,26]. To undertake these tests however we require spectroscopic confirmation of membership, which can be observationally demanding to obtain [22,23].
Finally, I have started to investigate the role that dust plays
in altering our perception of the nature of cluster galaxies at
high redshifts. Dust is a by-product of massive star formation and
at the same time obscures it from sight. Thus it is possible to
hide relatively large amounts of star formation in otherwise
quiescent looking cluster galaxies [24,25].
1) ``A Statistical Analysis of the Galaxy Populations of Distant Luminous X-ray Clusters'', Smail et al. (1998)
2) ``The Faint End of the Luminosity Function in Intermediate Redshift Clusters'', Wilson et al. (1997)
3) ``Morphological Studies of the Galaxy Populations in Distant `Butcher-Oemler' Clusters with HST: I. AC114 at z=0.31 and Abell 370 at z=0.37'', Couch et al. (1994)
4) ``Morphological Studies of the Galaxy Populations in Distant `Butcher-Oemler' Clusters with HST: II. AC103, AC118 and AC114 at z=0.31'', Couch et al. (1998)
5) ``A Catalog of Morphological Types in 10 Distant Rich Clusters of Galaxies'', Smail et al. (1997)
6) ``A Catalog of Spectral Observations of 10 Distant Rich Clusters of Galaxies'', Dressler et al. (1999)
7) ``The Star Formation Histories of Galaxies in Distant Clusters'', Poggianti et al. (1999)
8) ``The Life-cycle of Star Formation in Distant Clusters'', Barger et al. (1996)
9) ``Evolution Since z = 0.5 of the Morphology-Density Relation for Clusters of Galaxies'', Dressler et al. (1997)
10) ``The Homogeneity of Spheroidal Populations in Distant Clusters'', Ellis et al. (1997)
11) ``Evolution in the Elliptical Populations of Distant Clusters'', Barger et al. (1998)
12) ``Constraints on the Evolution of S0 Galaxies in Rich Clusters'', Jones, Smail & Couch (2000)
13) ``A Photometric Study of the Ages and Metallicities of Early-Type Galaxies in A2218'', Smail et al. (2001)
14) ``The Early Type Galaxy Population in Abell 2218'', Zeigler et al. (2001)
15) ``Testing the Hypothesis of the Morphological Transformation from Field Spiral to Cluster S0'', Kodama & Smail (2001)
16) ``Distinguishing Local and Global Influences on Galaxy Morphology: An HST Comparison of High and Low X-ray Luminosity Clusters'', Balogh et al. (2002)
17) ``Galaxy Properties in Low X-ray Luminosity Clusters at z=0.25'', Balogh et al. (2002)
18) ``The Las Campanas/AAT Rich Cluster Survey: I. Precision and Reliability of the Photometric Catalogue'', Pimbblet et al. (2001)
19) ``The Transformation of Galaxies within the Large Scale Structure around a z=0.41 Cluster'', Kodama et al. (2001)
20) ``The Las Campanas/AAT Rich Cluster Survey: II. The Environmental Dependence of Galaxy Colours in Clusters at z~0.1'', Pimbblet et al. (2002)
21) ``A Wide Field Hubble Space Telescope Survey of the Cluster Cl0024+16 at z=0.4. I: Morphological Distributions to 5 Mpc'', Treu et al. (2003)
22) ``A Low Global Star Formation Rate in the Rich Galaxy Cluster AC114 at z=0.31'', Couch et al. (2001)
23) ``An H-alpha Survey of the Rich Cluster A1689'', Balogh, et al. (2002)
24) ``HST Near-infrared and Optical Imaging of Faint Radio Sources in the Distant Cluster Cl0939+4713'', Smail et al. (1999)
25) ``The Detection of Dust in the Central Galaxies of Distant Cooling-Flow Clusters'', Edge et al. (1999)
26) ``The Morphology-Density Relation in the Sloan Digital Sky Survey'', Goto et al. (2003)
27) ``The Early-Type Galaxy Population in Distant Clusters at z~0.2 - I. The Fundamental Plane'', Fritz et al. (2004)
28) ``Studying Star Formation Histories of Galaxies in Clusters from Composite Spectra'', Dressler et al. (2004)
My work on the properties of lensed galaxies sparked an interest in
the (unlensed) field galaxy population - as studied through the
deepest imaging in optical [1,2]
and near-infrared passbands . I have also
studied the clustering properties of the faint galaxies detected in
these deep images [4,5], which has
illustrated the ambiguities inherent in such approaches. My more
recent work on the faint field population has concentrated on a small
subset of galaxies which exhibit extremely red optical-near-infrared
colors, these Extremely Red Objects (EROs) comprise passive, evolved
galaxies at high redshifts whose colors are dominated by old, red
stars [6,7], and more actively
star-forming galaxies which are reddened by the presence of large
amounts of interstellar dust . The morphologies of
the different population can also provide a useful guide to their
relative abundances . Once again,
the magnifying power of gravitational lenses has proved a very
useful tool for studying these faint galaxies in great detail
1) ``Deep Optical Galaxy Counts with the Keck Telescope'', Smail et al. (1995).
2) ``Counts and Colors of Faint Galaxies in the U and R Bands'', Hogg et al. (1997)
3) ``Deep Galaxy Counts in the K-band with the Keck Telescope'', Djorgovski et al. (1995)
4) ``Evolution in the Clustering of Galaxies to r=26'', Brainerd, Smail & Mould (1995)
5) ``A Constant Clustering Amplitude for Faint Galaxies?'', Brainerd & Smail (1998)
6) ``Near Infrared Observations of the Extremely Red Object Cl0939+4713B: An Old Galaxy at z~1.58?'', Soifer et al. (1999)
7) ``An HST Lensing Survey of X-ray Luminous Clusters: III. A Multiply-imaged Extremely Red Galaxy at z=1.6'', Smith et al. (2002)
8) ``Near-infrared Spectroscopy and Hubble Space Telescope Imaging of a Dusty Starburst ERO'', Smith et al. (2001)
9) ``An HST Morphological Survey of Faint EROs'', Gilbank et al. (2004)
10) ``An HST Lensing Survey of X-ray Luminous Clusters: II. A Search for Gravitationally Lensed EROs'', Smith et al. (2002)
And then we are left with the research which doesn't fit into the
tidy categories described above. These are many random things which
you accrete as you go through life - due to being at telescope at wrong time
[1,2] or too often ,
listening to wrong seminars 
or just being on vacation .
1) ``The X-ray, Optical and Infrared Counterpart to GRB980703'', Vreewijk et al. (1999)
2) ``The Optical Afterglow and Host Galaxy of GRB000926'', Fynbo, et al. (2001)
3) ``INGRID: A Near-Infrared Camera for the WHT'', Packham et al. (2003)
4) ``Star Counts Redivivus II: Deep Star Counts with the Keck and HST and the Luminosity Function of the Galactic Halo'', Reid et al. (1996)
5) ``The Identification of Two z~3.8 QSOs in a Deep CCD Survey'', Smail, Edge & Ellis (1998)