Applications are invited for as many as two postdoctoral appointments at the University of Minnesota to interpret extremely deep Hubble Space Telescope imaging of galaxy-cluster fields as part of an upcoming Cycle 27 & 28 campaign. The 192-orbit program, entitled “Flashlights: Many Extremely Magnified Individual Stars as Probes of Dark Matter and Stellar Populations to Redshift z~2” (GO-15936), will acquire two epochs of unfiltered ultraviolet through optical imaging of the six Hubble Frontier Field galaxy clusters. The expected single-visit five-sigma limiting magnitude of 31 AB should yield detections of up to twenty-five individual luminous stars at z=1–2 through microlensing due to stars in the foreground clusters. Primordial black holes accounting for 1–2% of galaxy-cluster dark matter would be detectable through a substantial increase in the number of detected microlensing events.
The rates of microlensing events in background galaxies will also probe the upper end of the initial mass function at z=1–2. Moreover, pairs of highly magnified images of stars should trace the astrometric distortions of the cluster critical curve and yield insights into the population of dark-matter subhalos. The observations, with an optical depth matching that of planned JWST near-infrared observations, will also enable a number of other science analyses.
The successful candidate(s) will work with principal investigator of the Flashlights program Prof. Patrick Kelly as well as co-investigators Prof. Liliya Williams and Prof. Claudia Scarlata at the University of Minnesota and collaborators at other institutions. Challenges include development of simulation codes for the microlensing events. Effort will be needed to develop detailed models of the populations of microlenses in the cluster and within the lensed background galaxies using photometry and spectroscopy, including planned follow up using the Keck telescopes. The successful candidate may also acquire additional observations, and will prepare papers and potentially proposals. Available observing facilities include the twin 8.4-m Large Binocular Telescope, the 6.5-m MMT, the 2.3-m Bok Telescope, as well as the 1.5-m Mount Lemmon Observing Facility.
The appointments will begin on or before September 1, 2020 and be for two years with the possibility of renewal for a third year given available funding and progress. Complementary research efforts at the Minnesota Institute for Astrophysics include programs in gravitational lensing, massive stellar populations, cosmology, galaxy clusters, galaxy evolution, and transient astronomy. Applicants should email Patrick Kelly at email@example.com with a statement of research interests (up to two pages), a resume, and a publication list. Please also arrange for three references to send letters of recommendation to the same email address. Full consideration will be given to applications that are received by December 15, 2019.