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Dust obscured radio-quiet quasars at high redshifts

Dust obscured radio-quiet quasars at high redshifts. Mark Lacy, NAASC/NRAO Andreea Petric (SSC), Susan Ridgway (CTIO), Tanya Urrutia (SSC), Anna Sajina (Haverford), Alejo Martinez-Sansigre (Oxford/Portsmouth). The co-evolution of black holes and massive galaxies. Tremaine et al 2002.

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Dust obscured radio-quiet quasars at high redshifts

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  1. Dust obscured radio-quiet quasars at high redshifts Mark Lacy, NAASC/NRAO Andreea Petric (SSC), Susan Ridgway (CTIO), Tanya Urrutia (SSC), Anna Sajina (Haverford), Alejo Martinez-Sansigre (Oxford/Portsmouth)

  2. The co-evolution of black holes and massive galaxies Tremaine et al 2002 • Models can reproduce observed relation if galaxy mergers trigger quasar activity, and subsequent AGN feedback stops star formation. • But only about 1/3 quasar hosts show signs of mergers. • Different timescales? • Star formation quickly suppressed in quasars? • Selection effects?

  3. IR-selected quasars • We have used Spitzer to select samples of quasars based on their mid-infrared dust continua. Continuum+PAH Red continuum Blue continuum

  4. Spectroscopy • Follow up with optical/IR spectroscopy. • Classify optical spectra as: • type-1 (normal quasar) • type-2 (high-ionization narrow lines only) • red type-1 (1R) • starburst/LINER • Based on broad lines, BPT diagrams, [NeV] emission, high-ionization UV emission lines.

  5. Evolution of obscured quasars

  6. Host galaxies of dust obscured quasars • Hosts out to z~1 easy to image with HST/ACS. • All show some signs of interaction/merger.

  7. Stacking at 160mu • Stack all z>2 type-1s (17) and obscured quasars (37). Type-1s have lower SFRs. • Mean luminosity ~LIRG/ULIRG transition

  8. SEDs • Two z>2 obscured quasars detected with MAMBO (1.3mm), corresponding to HLIRG luminosities. • z=4.27 object also detected in CO.

  9. Summary • A population of radio-quiet, luminous, dust obscured quasars exists out to at least z~4, whose numbers exceed those of normal quasars. • Tentative evidence that the true peak of luminous quasar activity occurred at higher redshifts than currently believed. • Dust obscured quasars seem to show higher star formation rates than their unobscured counterparts. All good news for ALMA/EVLA

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