Mid-infrared Spectral Properties of Post-Starburst Quasars

Abstract

We present Spitzer InfraRed Spectrograph (IRS) low-resolution spectra of 16 spectroscopically selected post-starburst quasars (PSQs) at z ~ 0.3. The optical spectra of these broad-lined active galactic nuclei (AGNs) simultaneously show spectral signatures of massive intermediate-aged stellar populations making them good candidates for studying the connections between AGNs and their hosts. The resulting spectra show relatively strong polycyclic aromatic hydrocarbon (PAH) emission features at 6.2 and 11.3\micron and a very weak silicate feature, indicative of ongoing star formation and low dust obscuration levels for the AGNs. We find that the mid-infrared composite spectrum of PSQs has spectral properties between ULIRGs and QSOs, suggesting that PSQs are hybrid AGN and starburst systems as also seen in their optical spectra. We also find that PSQs in early-type host galaxies tend to have relatively strong AGN activities, while those in spiral hosts have stronger PAH emission, indicating more star formation.

18 pages, 7 figures, 2 tables; Accepted for publication in ApJ: May 24, 2013

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Cited by in corpus (5)

• Theoretical Challenges in Galaxy Formation
• Extremely Red Quasars from SDSS, BOSS and WISE: Classification of Optical Spectra
• 2D stellar population and gas kinematics of the inner kiloparsec of the post-starburst quasar SDSS J0330-0532
• A Systematic Analysis of Stellar Populations in the Host Galaxies of SDSS Type I QSOs
• A Catalog of Post-starburst Quasars from Sloan Digital Sky Survey Data Release 7