ROSAT Guest Observer Facility


Martin Elvis
Harvard-Smithsonian Center for Astrophysics,

The following is the text from viewgraphs presented at the San Diego HEAD session on the ROSAT long-term observing plan.

Nearby AGN

Extended emission around Seyfert 1, 2s

  • About a dozen nearby AGN have deep ( tex2html_wrap_inline60 10 ks) HRI observations.
  • At least 1/2 of these show extended X-ray emission around the compact source.
  • For those which show extended emission, it is a major component: 20%-30% of HRI total count rate.
  • The extended X-ray emission appears related to extended optical/radio emission - but there are no clear correlations yet.
  • The extended emission may be aligned with jet axes.
  • The observations also show an excess of point-like sources near Seyferts.
  • OBSERVE: 50 nearby Seyferts at 25 ks each for 1.25 Ms.


  • ``Activity'' may be ubiquitous in galaxy nuclei.

    • 1/3 of m<12.5 Shapley-Ames galaxies have LINER nuclei.
    • 14% of same have Low Luminosity AGN (LLAGN, e.g., M 81) [Palomar survey].
  • Half of the LLAGN/LINERs in the Shapley-Ames catalog may have been missed (e.g., edge-on orientation).
  • No continuum flux is observed for these LLAGN/LINERS.
  • LLAGN are important to understanding the X-ray background and nature of the faintest X-ray sources.
  • The luminosity function of these objects is highly uncertain.
  • The HRI can separate the nucleus from bulge.
  • The Palomar sample has 486 galaxies. A well defined sub-set can be used for a ROSAT HRI survey.
  • 10 ks is required to detect L tex2html_wrap_inline66  erg s tex2html_wrap_inline68 at 20 Mpc.
  • OBSERVE: 200 galaxies at 10 ks each for 2 Ms.

Dwarf Galaxies

  • Can dwarf galaxies harbor AGN? I.e., is there a lower limit to the galaxy mass in which a massive black hole can be found?
  • Are dwarf galaxies related to both quasar and galaxy formation processes?
  • Problems: a bright AGN would swamp a dwarf galaxy; a faint AGN ( tex2html_wrap_inline70  erg s tex2html_wrap_inline68 ) is hard to see optically.
  • Targeted survey of nearby, nucleated dwarfs: from Kraan-Kortweg & Tamman (1986)
  • OBSERVE: 50 dwarfs at 20 ks each for 1 Ms.

Rare and Distant AGN

  • Extreme examples of a class can illuminate their physics.
  • Extreme examples are ipso facto, rare.
  • Need survey volume to find them.
  • BUT: The ROSAT all-sky survey is wide angle, but shallow; pointed PSPC archive is deep, but narrow angle.
  • Therefore, we must target known examples from the radio and optical.

High Redshift Quasars

  • Aim: Study the evolution of emission mechanism and environment via tex2html_wrap_inline74 , tex2html_wrap_inline76 , and cut-offs.
  • Almost no radio-quiet z>2 quasars known in X-rays; none bright enough to get X-ray spectra.
  • OBSERVE: all tex2html_wrap_inline60 50 z>2 .AND. tex2html_wrap_inline84 17 QSOs at 20 ks each for 1 Ms.

High CSS and GPS Quasars

  • Compact (10-100 pc), lobe-dominated (non-blazar) quasars.
  • Are they confined by medium? X-ray cut-off; X-ray extent.
  • Approximately 10 cut-off examples.
  • Approximately 1 extended example. (out of approximately 3).
  • Approximately 75 CSS in 3CR (no GPS because of low frequency selection).
  • OBSERVE: tex2html_wrap_inline86 at 5-10 ks each for 0.5 Ms.

Red Quasars

  • Mix of synchrotron cut-off, reddening, and quasars with no ``blue bump''?
  • Peculiar geometry? Nearly edge-on?
  • OBSERVE: 15% of 3CR, tex2html_wrap_inline88 objects at 25 ks each (faint) for 1.25 Ms.

Damped L tex2html_wrap_inline90 Absorbers

  • Lyman- tex2html_wrap_inline90 absorption in quasars ( tex2html_wrap_inline94  cm tex2html_wrap_inline96 .)
  • Probable protogalaxies (e.g., Art Wolfe et al.) ( tex2html_wrap_inline98 )
  • X-ray measurement of abundances (e.g., G. Madejski - A0235+164)
  • Few detections. Typically m=17-18.
  • OBSERVE: 20 DLA objects at 25 ks each for 0.5 Ms.


Extended emission around Seyfert 1, 2s:
1.25 Ms
Mini-AGN & LINERS: 2 Ms
Dwarf galaxies: 1 Ms
High Redshift Quasars: 1 Ms
CSS & GPS Quasars: 0.5 Ms
Red Quasars: 1.25 Ms
Damped Lyman tex2html_wrap_inline90 Systems: 0.5 Ms

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