Black Hole Mapper

The Black Hole Mapper (BHM) is a multi-object spectroscopic survey that will provide multi-epoch optical spectra for more than 400,000 X-ray sources to probe the growth of supermassive black holes over cosmic time. BHM will make use of the existing BOSS spectrographs, which provide wide spectral coverage with a spectral resolution of R~2000. BHM will operate on the 2.5m telescopes at both Apache Point and Las Campanas Observatories.


Schematic overview of the innermost regions around a quasar’s central supermassive black hole, showing the X-ray corona, accretion disk, and broad line region. BHM will take three parallel approaches to explore the physics of supermassive black hole accretion and dynamics, including reverberation mapping (top left; image from <a target="_blank" href="http://adsabs.harvard.edu/abs/2017ApJ...837..131P">Pei et al. 2017</a>), eROSITA follow-up (top center), and multi-epoch spectroscopy (top right; image from <a target="_blank" href="http://adsabs.harvard.edu/abs/2014ApJ...789..140L">Liu et al. 2014</a>).
Schematic overview of the innermost regions around a quasar’s central supermassive black hole, showing the X-ray corona, accretion disk, and broad line region. BHM will take three parallel approaches to explore the physics of supermassive black hole accretion and dynamics, including reverberation mapping (top left; image from Pei et al. 2017), eROSITA follow-up (top center), and multi-epoch spectroscopy (top right; image from Liu et al. 2014).

Science Goals

Quasars are among the most luminous objects in the Universe. Powered by accretion onto supermassive black holes (BHs) at the centers of galaxies, quasars can be used as beacons to trace the growth of black holes over cosmic time. There is a tight correlation between the masses of the supermassive BHs and the galaxies that host them, which shows that there is a connection between the formation of the stellar component in a galaxy and of its supermassive BH. BHM will provide precise mass constraints, multi-wavelength spectral energy distributions (SEDs), and a detailed characterization of variability for a large sample of quasars:

  • BHM will observe hundred of epochs to determine BH masses (via reverberation mapping) of over 1,200 quasars within a range of redshifts from 0.1 to 4.5 and luminosities from Lbol ~ 1045 to 1047 erg s-1.
  • With a more modest number of epochs (a few to a dozen per target), optical spectral variability will be characterized for approximately 25,000 quasars, which will add to the knowledge of the astrophysics of supermassive BH accretion disks, dynamical changes in broad emission line region, signatures of binary BHs, and the properties of quasar outflows.
  • BHM will work closely with the results of the upcoming eROSITA satellite to provide optical spectroscopic measurements, including object identifications and redshifts, for the >400,000 X-ray sources predicted to be detected.

More details on the Black Hole Mapper and an extended description of its science goals can be found in the SDSS-V White Paper SDSS-V: Pioneering Panoptic Spectroscopy.

Contact information

For more information on the Black Hole Mapper, contact the SDSS-V/BHM Program Head, Scott Anderson (University of Washington).