Richard Ellis
Astronomy 249-17, Caltech
Pasadena CA 91125
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Position: Steele Professor of Astronomy
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Office: (626)-395-2598
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Cell: (626)-676-5530
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Secretary: (626)-395-4970
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Fax: (626)-568-9352
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Email: rse@astro.caltech.edu
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. I am enthusiastic about the use of new instruments and observational
opportunities when they further the progress that can be made in these
areas. In particular I am involved in promoting and managing the science partnership
for the Thirty Meter Telescope.
Recent Outreach Activities:
Read the
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 )
Watch the
promotional video about the excitement of the Thirty Meter Telescope
Watch an
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!)
Scientific Publications:
Check my scientific output on Google Scholar
Past and Present Students:
Check my proud list of successful graduate students!
Research Programs:
My current interests at Caltech 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
Euclid) capable
of tracing the growth of structure from the time-dependent clustering of dark matter
seen from weak lensing signals. On small scales I am using 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 am putting most of
my effort into examining the validity of using Type Ia SNe for future studies. My
research includes 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 is of a long term nature and is being 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.
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 Lyman alpha emission in
distant galaxies. Read about our latest 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:
`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'
(popular talk)
`Early Star-Forming Galaxies and
the Reionisation of the Universe' (review published in Nature November 4th 2010)
`Scientific Opportunities
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 (2013 submissions)
Hubble Space Telescope spectra of the type Ia supernova SN 2011fe: A
low-energy delayed detonation of a sub-solar composition white dwarf
Keck Spectroscopy of Gravitationally Lensed z=4 Galaxies:
Improved Constraints on the Escape Fraction of Ionizing Photons
Testing the Universality of the Fundamental Metallicity Relation at High
Redshift Using Low-Mass Gravitationally Lensed Galaxies
The CASSOWARY spectroscopy survey: A new sample of
gravitationally lensed galaxies in SDSS
New Constraints on Cosmic Reionization from the 2012
Hubble Ultradeep Field Campaign
Earlier Refereed Papers (2012 submissions)
A new multi-field determination of the galaxy luminosity function at z=7-9
incorporating the 2012 Hubble Ultra Deep Field imaging
The UV Luminosity Function of star-forming galaxies via dropout selection at redshifts
z ~ 7 and 8 from the 2012 Ultra Deep Field campaign
Evolution of the Sizes of Galaxies over z~7 to 12 Revealed
by the 2012 Hubble Ultra Deep Field Campaign
The 2012 Hubble Ultra Deep Field (UDF12): Observational Overview
The UV continua and inferred stellar populations of galaxies at z ~ 7 - 9
revealed by the Hubble Ultra Deep Field 2012 campaign
The Abundance of Star-Forming Galaxies in the Redshift Range 8.5 to 12:
New Results from the 2012 Hubble Ultra Deep Field Campaign
Uncovering Drivers of Disk Assembly: Bulgeless Galaxies and
the Stellar Mass Tully-Fisher Relation
Hubble Space Telescope H-alpha imaging of star-forming galaxies at z = 1-1.5:
evolution in the size and luminosity of giant HII regions
The Density Profiles of Massive, Relaxed Galaxy Clusters: II. Separating
Luminous and Dark Matter in Cluster Cores
The Density Profiles of Massive, Relaxed Galaxy Clusters: I. The Total
Density Over 3 Decades in Radius
Studying the Diversity of Type Ia Supernovae in the Ultraviolet:
Comparing Models with Observations
Keck Spectroscopy of 3 < z < 7 Faint Lyman Break Galaxies:
The Importance of Nebular Emission in Understanding the Specific Star Formation Rate and
Stellar Mass Density
The UV/optical spectra of the type Ia supernova SN 2010jn:
A bright supernova with outer layers rich in iron-group elements
The Origin and Evolution of Metallicity Gradients:
Probing the Mode of Mass Assembly at z=2
The ages, masses and star-formation rates of spectroscopically
confirmed z~6 galaxies in CANDELS
Newborn spheroids at high redshift:
when and how did the dominant, old stars in today's massive galaxies form?
Hubble Space Telescope studies of low-redshift Type Ia
supernovae: Evolution with redshift and ultraviolet spectral trends
Space-quality data from
balloon-borne telescopes: the High Altitude Lensing Observatory (HALO)
The Assembly History of Disk Galaxies: II - Probing the Emerging Tully-Fisher
Relation during 1 < z < 1.7
Current Committees
Thirty Meter Telescope Board of Directors
Thirty Meter Telescope Science Advisory Committee
Science Steering Committee for
Keck Observatory
Scientific Advisory Board,
Dark Cosmology Centre, University of Copenhagen
Advisory Committee,
Cosmology and Gravity Program, Canadian Institute of Advanced Research
Teaching
Ay 123 Structure and Evolution of Stars
Ay 211 Extragalactic Astronomy
Ay 124 Structure and Dynamics of Galaxies
Other Information:
Page maintained by Richard Ellis rse@astro.caltech.edu
Last modified : 6th January 2013