Other
Scientific paper
Mar 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008sptz.prop50591s&link_type=abstract
Spitzer Proposal ID #50591
Other
Scientific paper
We propose to obtain mid-IR spectra with the IRS to search for highly obscured (a.k.a. 'buried') AGN in an unusual type of powerful radio galaxies called 'Compact Symmetric Objects' (CSOs) and to determine whether they show any evidence for accreting gas. Evidence from VLBI proper motion studies finds that CSOs are very young AGN (500-3000 years old) which will eventually become large-scale powerful radio galaxies (similar to 'mini-Cygnus As'). Thus, we are viewing the nuclear regions of these galaxies at the time of the 'birth' of these AGN. While there is substantial multi-wavelength evidence for modest amounts of nuclear gas and dust in CSOs, near-IR HST images and ground-based spectra show no evidence for extremely large dust extinction, on-going mergers, or reprocessed line and continuum emission indicative of an accretion disk. Rather, the nuclear regions of CSOs show normal elliptical galaxy profiles at H-band with no evidence for an AGN point source. It is thus probable that either CSOs are 'naked AGN' with no nuclear non-thermal continuum or reprocessed line emission, or that the AGN are so heavily extincted that the accreting gas is visible only in the mid-infrared. Our Cycle 3 IRS observations of a small subsample of CSOs show considerable diversity in their mid-infrared spectra; some resemble modestly starbursting galaxies, while others are akin to PG quasars. Tellingly, NONE of the five low-redshift CSOs previously observed with the IRS show confirmed [NeV] detections, suggesting that CSOs as a class lack accreting nuclear gas (a 2.5 sigma result based upon 5 objects), despite their recent launch of luminous, non-thermal radio jets. We propose to observe the remaining four z < 0.1 CSOs to determine whether they are powered by gas accretion or whether CSOs (and by extension, all radio-loud AGN) require a different type of energy source such as black hole spin.
Darling Jeremy
Perlman Eric
Stocke John
Willett Kyle
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