Astronomy 249-17, Caltech
Pasadena CA 91125
Position: Visiting Associate:
On September 1st 2015 I moved to a new position in Europe and my contact
details are on my European web page
- However the US communication details below are still functional
Overview of Research:
I am working primarily in observational cosmology addressing issues
related to the nature of the world model, the origin and evolution of galaxies,
the growth of large scale structure and the nature and distribution of
dark matter. My recent focus is on addressing the origin of the earliest
galaxies and understanding their role in cosmic reionisation.I am enthusiastic
about the use of new instruments and observational opportunities when
they further the progress that can be made in these areas.
Recent Outreach Activities:
interview on Searching for the First Stars sponsored by the Kavli Foundation.
Watch the two supernova cosmology
teams present reminiscences and anecdotes at Stockholm University as part of the 2011 Nobel Prize
in Physics celebrations (WMV format)
Read the Scientific
Background on the Accelerating Universe awarded the 2011 Nobel
Physics Prize in part to the Supernova Cosmology Project
(led by Saul Perlmutter )
promotional video about the excitement of the Thirty Meter Telescope
interview about 90 years of gravitational lensing produced for the Royal Society
Listen to an interview
on BBC Radio Wales on how I became an astronomer (light entertainment only!)
Check my scientific output on Google Scholar
Past and Present Students:
Check my proud list of successful graduate students!
My current interests fall under 4 main headings:
Gravitational lensing: I have been interested in the role that gravitational
lensing can play in cosmology and galaxy formation studies since the late 1980's. I remain
hopeful that during my scientific career we can launch an imaging satellite (such as
of tracing the growth of structure from the time-dependent clustering of dark matter
seen from weak lensing signals. On small scales I have used strong lensing to separate dark and baryonic matter
distributions in clusters to understand how baryons influence the dark matter profile.
Strong lensing also enlarges the apparent sizes of background galaxies and I have used this
phenomenon to locate distant galaxies and study their internal properties such as
their abundance gradients and velocity fields.
Distant Supernovae: I took part in one of the earliest successful studies to
locate and characterize cosmologically-distant Type Ia supernovae and later joined
the Supernova Cosmology Project .
The resulting "accelerating Universe", recently awarded the
2011 Nobel Prize in Physics, is a bewildering result which has motivated
a number of more ambitious ongoing and future supernovae surveys. I put most of
my effort into examining the validity of using Type Ia SNe for future studies. My
research included examining the environmental dependence of supernova properties as
well as the question of possible spectral evolution such as might arise from changes in
the progenitor composition. This work was undertaken with spectrographs on Keck and HST.
Large Scale Structure: I have been an enthusiastic promoter of multi-object
spectroscopy since the 1980's, working with colleagues to develop early robotic positioners
for the former Anglo-Australian Telescope and several
multi-slit spectrographs. This work culminated in the
2 degree Field Galaxy Redshift Survey which demonstrated the presence of a baryonic acoustic peak
in the large scale distribution of nearby galaxies whose precise measurement at various
epochs is a very powerful cosmological probe. I am working with an international team to build
the Prime Focus Spectrograph for
the Subaru 8m Telescope.
When constructed this instrument will undertake a survey of millions of faint galaxies to
directly map the cosmic expansion history since a redshift 2 as well
as probe the stellar halo of our Galaxy and M31. Read the
detailed science case for this remarkable instrument. I also recently led a ESO Working
Group that would take the next logical step towards a 10-12 meter class telescope with a
5 square degree field. Read the Working Group Report
that describes the remarkable science potential of such an instrument.
Galaxy Formation and Evolution: I have been interested in studying the properties
of distant galaxies since I was a postdoc in the late 1970's. I use the combination of HST images,
Spitzer photometry, ground-based K-band imaging and, most of all, Keck spectroscopy to
better understand the origin of the wide diversity of galaxy morphologies. Key questions
I am working on include the mass-dependent assembly of galaxies over the redshift range 0
to 7, tracing cosmic reionization through deep Hubble imaging and statistical measures of line emission in
distant galaxies. Read about the Hubble Ultra Deep Field
2012 program to study galaxies deep in the reionization epoch. Closer to home I also study
the onset of ordered rotation and surprisingly compact nature in distant spiral and elliptical
galaxies respectively. I am a recent convert to the phenomenal advances being made in these
areas through the use of adaptive optics.
Recent Review Articles and Talks:
`Gravitational Lensing: Einstein's Unfinished Symphony'
(Invited Review: United Nations `Year of Light' Series, Contemporary Physics in press)
`Cosmic Dawn: Studies of the Earliest Galaxies and
their Role in Cosmic Reionization' (Invited Review: 26th Solvay Conference, Brussels October 2014)
`A Century of Redshift Surveys' (Invited
Talk: Origins of the Expanding Universe)
`The Global Impact of ESO' (Invited Review),
ESO's 50th Anniversary, Garching 2012
`First Light and the Faintest Dwarfs'
(Conference Summary), KITP, Santa Barbara 2012
`New Horizons at High Redshift' (Conference
Summary), Cambridge 2011
`Gravitational Lensing: Einstein's Unfinished
Symphony' (popular talk)
`Cosmic Dawn: The Search for the First Galaxies'
`Early Star-Forming Galaxies and
the Reionisation of the Universe' (review published in Nature November 4th 2010)
for 30 Meter Class Optical Telescopes' (invited talk (doc) at New Visions 400, Beijing 2008)
`The Origin of Galaxies' (Conference Summary (ppt), Obergurgl, Austria Dec 2009)
`The UKIRT Success Story' (opening
talk at `UKIRT at 30' (doc), Edinburgh Sep 2009)
`Gravitational Lensing: An Unique Probe
of Dark Matter and Dark Energy' (invited popular review to celebrate 350 years of Royal Society (doc), Aug 2009)
`The Quest for Giant Telescopes: Four Centuries
of Challenge and Scientific Discovery' (Keynote Talk (ppt) at 2009 APS Meeting Denver, May 2009
`Panoramic Views of
Galaxy Formation and Evolution' (Conference Summary (pdf), Hayama, Japan, Dec 2007)
`Observations of the
High Redshift Universe in `First Light' (Saas-Fee Lectures (pdf), Apr 2007)
Latest Refereed Papers (2017 submissions)
Dust in the Reionization Era: ALMA observations of a z=8.38 galaxy
Refereed Papers (2016 submissions)
The z=6 Luminosity Function Fainter than -15 mag from the
Hubble Frontier Fields: New Insights into the Impact of Magnification Uncertainties
A Hard Ionizing Spectrum in z=3-4 Ly-alpha Emitters with Intense [O III] Emission:
Analogs of Galaxies in the Reionization Era?
Prime Focus Spectrograph (PFS) for the Subaru Telescope:
Overview, recent progress and future perspectives
MOSFIRE Spectroscopy of Quiescent Galaxies at z=1.5 to 2.5.
I - Evolution of Structural and Dynamical Processes
New Telescope Designs Suitable for Massively-Multiplexed
Absorption Line Spectroscopy of Gravitationally-Lensed Galaxies:
Further Evidence of an Increased Escape Fraction of Ionizing Photons at High Redshift
Lyman-alpha and CIII] emission in z=7-9 Galaxies:
Accelerated Reionization Around Luminous Star-Forming Systems?
A deep ALMA image of the Hubble Ultra Deep Field
Cosmology and Gravity Program, Canadian Institute of Advanced Research
Munich Institute for Astro- and Particle Physics
Scientific Advisory Committee
Kavli Institute for Astronomy and Astrophysics, Beijing
Ay 123 Structure and Evolution of Stars
Ay 211 Extragalactic Astronomy
Ay 124 Structure and Dynamics of Galaxies
Page maintained by Richard Ellis firstname.lastname@example.org
Last modified : 1st June 2017