---
res:
  bibo_abstract:
  - We explore the possibility of resolving an image of a damped Lyα (DLA) system
    in absorption against an extended, diffuse, background X-ray source. Typical columns
    of neutral hydrogen in DLA systems are high enough to block out up to ~30% of
    the soft X-ray flux at an observed photon energy of 0.5 keV, and we find that
    ~1% of the area of extended X-ray sources at z ≳ 1 have their 0.5 keV flux reduced
    by at least 20% because of intervening DLA systems. We discuss the observability
    of such absorption and find that ≳300 photons per angular resolution element are
    required in the 0.3-8 keV band for its detection and in order to distinguish it
    from intrinsic surface brightness fluctuations. For the surface brightness of
    the currently known high-redshift extended X-ray sources, this requires an integration
    time of a few megaseconds on Chandra, if the maps are smoothed spatially to ≈2''
    resolution. The exact required integration time depends on the DLA system's column
    density, metallicity, and, most strongly, its redshift. Current X-ray telescopes
    are likely to detect DLA systems with N < 10^22 cm^-2 only out to z ≈ 2.3. The
    availability of DLA systems with a suitably high column density for a silhouette
    detection is currently poorly known. We suggest that at low redshifts archival
    data of bright X-ray point sources may be useful in constraining the high-N end
    of the column density distribution. We briefly discuss an alternative strategy
    of searching for extended X-ray sources behind known DLA systems. Although with
    current X-ray telescopes the detections are challenging, they will be within the
    reach of a routine observation with a next generation X-ray telescope, such as
    the X-Ray Evolving Universe Spectrometer (XEUS) or Generation-X, and will deliver
    novel constraints on the nature of protogalaxies.@eng
  bibo_authorlist:
  - foaf_Person:
      foaf_givenName: Mark
      foaf_name: Dijkstra, Mark
      foaf_surname: Dijkstra
  - foaf_Person:
      foaf_givenName: Zoltán
      foaf_name: Haiman, Zoltán
      foaf_surname: Haiman
      foaf_workInfoHomepage: http://www.librecat.org/personId=7c006e8c-cc0d-11ee-8322-cb904ef76f36
  - foaf_Person:
      foaf_givenName: Caleb
      foaf_name: Scharf, Caleb
      foaf_surname: Scharf
  bibo_doi: 10.1086/428766
  bibo_issue: '1'
  bibo_volume: 624
  dct_date: 2005^xs_gYear
  dct_isPartOf:
  - http://id.crossref.org/issn/0004-637X
  - http://id.crossref.org/issn/1538-4357
  dct_language: eng
  dct_publisher: American Astronomical Society@
  dct_title: On detecting the X‐ray silhouette of a damped Lyα system@
...