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.

Research Group

Rachel Paterno-Mahler - Postdoctoral Researcher
Recent papers:
  • Merger Signatures in the Galaxy Cluster A98, Paterno-Mahler et al. (2014)
  • The High-Redshift Clusters Occupied by Bent Radio AGN (COBRA) Survey (2017)
    Traci Johnson - graduate student
    Recent papers:
  • Lens models and magnification maps of the six Hubble Frontier Fields clusters, Johnson et al. (2014)
  • The systematics of strong lens modeling quantified Johnson et al. (2016)
    Juan David Remolina G. - graduate student

    Catherine Cerny - undergraduate UMich Astronomy major [poster]--> Boston University
    Avery Peterson - undergraduate UMich Astronomy major
    Matt Past - undergraduate Astronomy major --> Toledo
    Brendan Reed - undergraduate UMich Astronomy major

    Former students:
    Katherine Murray - undergraduate UMich Astronomy major -- now at STScI
    Sam Dunham - undergraduate UMich Astronomy major -- now at Vanderbilt

    In the news:

    SDSS1110 We used a clusters of galaxies as a cosmic telescope, for a closer than ever look into a z=2.5 star forming galaxy. The beads of star formation can only be resolved with the power of gravitational lensing, and are the smallest that have ever been measured beyond the local Universe.
    [click on image for press release] papers are available here:
    Papar I Johnson et al. 2017
    Papar II Rigby et al. 2017
    Papar III Johnson et al. 2017

    SN Refsdal 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.
    Sharon & Johnson (2014)

    Is refsdal going to reappear soon? Five lens modeling teams predict the next appearance of Refsdal: Treu et al. (2015)

    Hubble Sees Spiral Bridge of Young Stars Between Two Ancient Galaxies (click to go to http://hubblesite.org)

    Videos and more!
    Read the papers:
  • Tremblay et al. (2014) arXiv:1407.2251
  • Sharon et al. (2014) arXiv:1407.2266

  • Hubble Zooms in on a Magnified Galaxy (click to go to http://hubblesite.org)

    Read the paper: [PDF | arXiv:1202.0539 | ApJ 746 161]

    Also picked up by: NASA | Science Daily | PHYSORG.com | Space Fellowship | hayadan (hebrew) | KICP homepage (full story) | U-M The Record

    Current Projects

    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 group-size gravitational lenses, in a thorough and statistically-meaningful survey. Some of these are homes for truly spectacular arcs. 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 page]

    Single sources:
  • Koester et al. (2010);
  • Bayliss et al. (2010);
  • SGAS 143845.1+145407: A Big, Cool Starburst at Redshift 0.816, Gladders et al. (2012)

    Cluster/lens properties
  • 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)

  • Poster presented at Monsters, Inc., SB conference;

    In preparation:
  • SDSS-GAS survey paper, Gladders et al. in prep
  • RCS-GA survey paper, Bayliss et al. in prep

  • SGAS-HST project:
    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

    Internal website
    RCS2 0327
    A giant arc at z~1.7,one of the brightest known at this high redshift, was discovered as part of 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
    Internal website

    Johnson, Sharon, Bayliss, Gladders, Coe & Ebeling (2014)

    Past Projects

  • Lensing
    Multiply imaged galaxies
    behind the cluster and lensed quasar
    SDSS J1004+4112

    The lensing cluster Abell 1689.
    Links to the paper and full resolution images
    can be found here
  • SN rates in clusters
    A Survey for Supernovae
    in Massive High-Redshift Clusters

    [project page]

  • Rates paper: Sharon et al. (2010)
    [full-res | arXiv:1006.3757]
  • DTD paper [arXiv:1006.3376]
  • WOOTS - Wise Observatory Optical Transient Search
  • Rates paper: Supernovae in Low-Redshift Galaxy Clusters: the Type-Ia Supernova Rate, Sharon et al. (2007)
  • WOOTS SNe paper: Gal-Yam et al. (2008)

  • Theses --

    Chapters from my PhD thesis, titled: "Evolution of Supernova Rates and Dark Matter In Clusters of Galaxies" are 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]

  • Short CV | full CV [pdf]
    Publications [ ADS | astro-ph ]

    Contact --
    U-M Astronomy
    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

    Links --

  • University of Michigan Astronomy
  • PPFP
  • LCO
  • KICP
  • UChicago Astro Department
  • Tel Aviv University
  • Wise Observatory

    Outreach --
  • Astronomy on Tap Ann Arbor
  • TAU Astronomy Club