Rob Simcoe

Scientific Research

   My research concentrates on the chemical link between star-forming galaxies and the intergalactic medium at high redshift (z > 2).  Together with Wal Sargent and Michael Rauch, I studied the distribution of heavy element abundances in the IGM at 2 < z < 3, using QSO absorption line spectra taken with Keck/HIRES.  In addition we characterized the frequency of high redshift intergalactic OVI absorbers, and in the process discovered a class of shock heated systems with properties suggesting an origin in galactic winds.

   More recently, we have studied a subset of these shock-heated absorbers in more detail, including comparisons with nearby, spectroscopically conformed z ~ 2.5 galaxies.  A thorough ionization modeling analysis of the QSO absorbers revealed near-solar level heavy-element abundances in the IGM surrounding the most massive star forming galaxies.   Moreover these systems exhibit signs of shock heating, and sheets or shells of material such as one might expect near radiative shock fronts.   These results suggest that galaxy formation can affect the physical properties of the nearby IGM directly over distances of >100 proper kpc.  Further observations for this program are ongoing at the Magellan telescopes.

   While much is known about the chemical composition of the IGM at 2 < z < 4, the constraints become weaker at high redshift because of the obvious observational challenges.  At z > 5, CIV absorption is redshifted into the J band, becoming inaccessible to high resolution optical spectrographs and increasingly prone to contamination from atmospheric OH foregrounds.  I have been engaged in a pilot program with Gemini/GNIRS to observe several high redshift QSOs for signatures of CIV absorption.  Also, in collaboration with Adam Burgasser and Paul Schechter at MIT, and Rebecca Bernstein, Mario Mateo, and Bruce Bigelow at the University of Michigan, I am working to develop an infrared spectrometer for Magellan that is particularly suited for QSO absorption line observations at the highest possible redshifts.  This instrument (named FIRE, for the Folded-port InfraRed Echellette) will cover the full 0.8-2.5 micron X/J/H/K bands at 50 km/s resolution in a single exposure, enabling sensitive absorption line measurements with large redshift pathlength in a single observational setup.

  For more information on any of these topics, I encourage you to visit my Publications page, or the FIRE project website.