Black Hole Mapper

Black Hole Mapper (BHM) is a multi-object spectroscopic survey, that will provide optical spectra for more than 400,000 sources, to probe the growth of supermassive black holes over cosmic time. BHM will make use of the existing BOSS spectrographs, which provide large spectral coverage (3600 – 10000 Å) with a spectral resolution of R ~ 2000. A robotic fiber-positing system will allow BHM to undertake time-domain studies to study variability, delivering multi-epoch spectroscopy. BHM will operate on the 2.5m telescopes at both Apache Point and Las Campanas Observatories.

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 mark and 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 its supermassive BH. BHM will provide measurements of a large sample of quasars, which will include precise mass constraints, multi-wavelength spectral energy distributions (SEDs), and a detailed characterization of variability:

  • BHM will exploit the potential of the quasar’s reverberating maps, sampling hundred of epochs to determine BH masses 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: an increase of about 25x over the samples collected by SDSS-III and SDSS-IV,
  • Optical spectral variability will be characterized, with a more modest number of epochs (a few to a dozen per target), 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, for which it will provide optical spectroscopic measurements, including identifications and redshifts, of over 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.


Schematic overview of the innermost regions around a quasar’s central supermassive black hole (BH), 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, with top left: reverberation mapping (image from <a target="_blank" href="http://adsabs.harvard.edu/abs/2017ApJ...837..131P">Pei et al. 2017</a>), top centre: eROSITA follow-up, and top right: multi-epoch spectroscopy (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 (BH), 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, with top left: reverberation mapping (image from Pei et al. 2017), top centre: eROSITA follow-up, and top right: multi-epoch spectroscopy (image from Liu et al. 2014).

Contact information

For more information on the Black Hole Mapper, contact the SDSS-V Program Head for Black Holes & Galaxy Clusters, Scott Anderson (University of Washington), anderson@astro.washington.edu.