I'm an Assistant Professor at the University of
Michigan Department of Astronomy.
My research focuses on observational study of strong lensing galaxy clusters, determining their
mass distributions, and using them as cosmic telescopes to study the background Universe.
Traci Johnson - graduate student
Recent paper: Lens models and magnification maps of the six Hubble Frontier Fields clusters, Johnson et al. (2014) arXiv:1405.0222
Katherine Murray - undergraduate UMich Astronomy major
Sam Dunham - undergraduate UMich Physics major
Postdoc position AAS Job Register
A supernova was discovered on Nov 11 2014 in a lensed galaxy at z=1.491, behind MACS1149. The SN
went off in a spiral arm of this galaxy, that happens to be going through secondary lensing by
a cluster galaxy. As a result, the SN is multiply-imaged and excitingly, 4 images of the SN
are detected in HST images.
The discovery paper from GLASS is available here -- Kelly et al. (2004).
This exciting lensed SN is not my discovery, but we do provide a lens model for this cluster.
The new lens model is based on Traci's FF model, with more constraints and fee parameters to describe the
area around the lensed SN better.
The revised lens model will be posted on MAST soon. In the meanwhile, the best-fit
magnification, time, and deflection matrices can be downloaded from here:
Sharon & Johnson (2014)
In the News:
Hubble Sees Spiral Bridge
of Young Stars Between Two Ancient Galaxies
(click to go to http://hubblesite.org)
Hubble Zooms in on a
Magnified Galaxy (click to go to http://hubblesite.org)
Giant Arc Surveys in SDSS and RCS1-2|
I am leading the SL modeling of cluster lenses from SDSS-GAS and RCS-GA.
In recent years our group at UofC has discovered hundreds of new cluster- and
lenses, in a thorough and statistically-meaningful survey. Some of these are
homes for truly spectacular
We aim to study the population of SL clusters via mass measurements using proxies
different wavelengths (from
Xray through the SZ effect); measure their mass distribution and abundance for
cosmological studies; and
analyze background galaxies that have been magnified by these clusters, providing
the opportunity to study
them in an unprecedented detail.
[Limited access wiki
Koester et al. (2010);
Bayliss et al. (2010);
SGAS 143845.1+145407: A Big, Cool Starburst at Redshift 0.816, Gladders et al. (2012)
Mass-concentration relation, Gralla et al. (2010);
Spectroscopy paper: Bayliss et al. (2011)
Arcs statistics: Bayliss et al. (2011)
Mass-metallicity relation in lensed galaxies, Wuyts et al. (2012)
Line-of-sight Structure toward Strong Lensing Galaxy Clusters, Bayliss et al. (2014)
Searching for Cooling Signatures in Strong Lensing Galaxy Clusters: Evidence Against Baryons Shaping the Matter Distribution in Cluster Cores, Blanchard et al. (2013)
SDSS-GAS survey paper, Gladders et al. in prep
RCS-GA survey paper, Bayliss et al. in prep
Our 107 orbit program
to image 37 lensing clusters with HST was approved for Cycle 20!
"Resolving the Star
Formation in Distant Galaxies"; PI:Gladders
A giant arc at z~1.7,one of the brightest known at this high redshift, was discovered as part
RCS. Since its discovery it has been the subject of detailed study by our group,
including multi-band photometry and spatially-resolved spectra.
A Bright, Spatially Extended Lensed Galaxy at z = 1.7 Behind the Cluster RCS2
032727-132623, Wuyts et al. (2010);
The Physical Conditions of a Lensed Star-forming Galaxy at z=1.7, Rigby et al. (2011);
Source Plane Reconstruction of The Bright Lensed Galaxy RCSGA
032727-132609, Sharon et al. (2012)
Resolved Star Formation on Sub-galactic Scales in a Merger at z=1.7, Whitekar et al. (2014)
A Magnified View of the Kinematics and Morphology of RCSGA 032727-132609: Zooming in on a Merger at z = 1.7, Wuyts et al. (2014)
Hubble Frontier Fields|
Our research group was chosen as one of five research groups to provide the community with
preliminary detailed lensing magnification maps of the six Frontier Fields clusters.
These public lensing magnification maps will enable the use of the Frontier Fields clusters
as powerful cosmic telescopes.
Frontier Fields @STScI
Johnson, Sharon, Bayliss, Gladders, Coe & Ebeling (2014)
SN rates in clusters
The lensing cluster Abell 1689.
Links to the paper and full resolution images
can be found here
Chapters from my PhD thesis, titled: "Evolution of Supernova Rates and
Dark Matter In Clusters of Galaxies"
published as the following papers:
Sharon et al. (2007)
Sharon et al. (2010)
Maoz, Sharon & Gal-Yam (2010)
Sharon et al. (2005)
My MSc thesis: "SN Counts in Deep HST fields" [ps]
Publications [ ADS
311 West Hall (mailing)
301 D West Hall (office)
1085 S. University Ave.
Ann Arbor, MI 48109-1107
(734) 936 2079
E-Mail: kerens @ umich.edu
University of Michigan
UChicago Astro Department
Tel Aviv University
TAU Astronomy Club