Black Hole Mapper

The Black Hole Mapper (BHM) in SDSS-V is a multi-object spectroscopic survey that will emphasize optical spectra (often also with multiple epochs of spectrosopy) for well more than 300,000 quasars to jointly understand the masses, accretion physics, and growth and evolution over cosmic time of supermassive black holes. BHM will make use of the existing BOSS spectrographs, which provide wide optical 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 adopt several parallel approaches to explore the physics of supermassive black holes, including reverberation mapping to measure BH masses (top left; image from <a target="_blank" href="http://adsabs.harvard.edu/abs/2017ApJ...837..131P" rel="noopener noreferrer">Pei et al. 2017</a>), <em>eROSITA</em> follow-up (top center) for cosmic demographics and evolution, and multi-epoch spectroscopy to understand dynamics and physics of accretion and outflows (top right; image from <a target="_blank" href="http://adsabs.harvard.edu/abs/2014ApJ...789..140L" rel="noopener noreferrer">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 adopt several parallel approaches to explore the physics of supermassive black holes, including reverberation mapping to measure BH masses (top left; image from Pei et al. 2017), eROSITA follow-up (top center) for cosmic demographics and evolution, and multi-epoch spectroscopy to understand dynamics and physics of accretion and outflows (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 BHs 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. The BHM will provide mass measures, multi-wavelength spectral energy distributions (SEDs), and a detailed characterization of variability for a large sample of quasars:

  • BHM will observe with hundred of epochs of time-domain spectra to determine BH masses (via reverberation mapping) of over 1,000 quasars spanning a very wide 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 next-generation eROSITA X-ray survey (part of the recently launched SRG mission) to provide optical spectroscopic measurements, including identifications of the nature of and redshifts for, ~300,000 X-ray sources that will be discovered early by eROSITA. Most will be confirmed to be quasars via their SDSS-V/BHM follow-up spectra, e.g., providing an order of magnitude advance in X-ray/optical studies of the growth and evolution of quasars (unobscured and obscured) over cosmic time.

More details on the Black Hole Mapper and an extended description of its science goals can be found on the Science of SDSS-V page and 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).