The Xray properties of Spitzerselected type2 quasars

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The X-ray properties of Spitzer-selected type-2
quasars

• Mark Lacy (SSC),
• Nick Seymour, Anna Sajina, Lisa Storrie-Lombardi,
  Lee Armus (SSC)
• Andreea Petric (Columbia), Gabriela Canalizo
  (Riverside), Susan Ridgway (NOAO), Elinor Gates
  (Lick Obs)

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Surveys for dust-obscured AGN

• Chandra surveys vs Spitzer surveys
• Spitzer finds objects on basis of hot dust
  emission.
• Finds preferentially high accretion-rate objects
  (dirty accretors).
• Chandra misses the most heavily obscured objects,
  but can find low accretion rate objects that
  Spitzer misses (e.g. some LINERS/XBONGs/low-lumino
  sity radio galaxies - the clean accretors).

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Spitzer selection of AGN

• Use wedge in IRAC color-color plot to select
  objects with hot dust continua, or require red
  power-law in mid-IR.
• At bright (24mu flux 5mJy) levels, 0.6,
• median (bolometric) luminosity about x10
  QSO/Seyfert divide.
• Optically, our IR-wedge selected AGN sample is
  33 normal type-1, 44 type-2, 14 reddened
  type-1 and 9 low-ionization in the optical (Lacy
  et al. 2006).

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What about the X-ray?

• Some of our type-2 quasars overlap 20-50ks XMM
  pointings.
• Most fluxes from 2XMM.
• About half the type-2s are detected.
• All the detected type-2 objects have high
  hardness ratios where available.

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X-ray survey strategies

• Areal density of bright AGN low 6/deg2 to
  5mJy at 24mu.
• Shallow X-ray survey will find the 1/3
  unobscured objects.
• Deep pointed observations (30ks) required for
  the obscured objects.
• Contrast with GOODS-type surveys - finds these
  objects, but only at z1.

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ADIOS (Richards et al)

• Wide area (200deg2) survey in SDSS equatorial
  field
• Field is repeated when northern fields are
  unavailable
• Limit 25 mag
• Applying for Spitzer/IRAC time, principally for
  quasar survey.

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Summary

• Making sense of the AGN population requires both
  Spitzer and Chandra.
• Host galaxy absorption/extinction probably plays
  an important role at the highest columns, but
  more study of heavily absorbed objects required.
• May have to abandon the pyramid scheme to study
  luminous heavily absorbed quasars at zother rare objects).

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The Compton thick elephant
(with apologies to Banksy (and the elephant))