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18 April 2024 |
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Fading AGN Candidates: AGN Histories and Outflow Signatures | | William C. Keel
; Chris J. Lintott
; W. Peter Maksym
; Vardha N. Bennert
; S. Drew Chojnowski
; Alexei Moiseev
; Aleksandrina Smirnova
; Kevin Schawinski
; Lia F. Sartori
; C. Megan Urry
; Anna Pancoast
; Mischa Schirmer
; Bryan Scott
; Charles Showley
; Kelsi Glatland
; | | Date: |
18 Dec 2016 | | Abstract: | We consider energy budgets and radiative history of 8 fading AGN, identified
from mismatch between the ionizion of very extended (>10 kpc) ionized clouds
and the luminosity of the nucleus viewed directly. All show significant fading
on ~50,000-year timescales. We explore the use of minimum ionizing luminosity Q
derived from photoionization balance in the brightest pixels in H-alpha at each
projected radius. Tests using PG QSOs, and one target with detailed
photoionization modeling, suggest that we can derive useful histories of
individual AGN; the minimum ionizing luminosity is always an underestimate and
subject to fine structure in the ionized material. These tests suggest that the
underestimation from the upper envelope of Q values is roughly constant for a
given object. These AGN show rapid drops and standstills; the common feature is
a rapid drop in the last 20,000 years before our view of the nucleus. E-folding
timescales are mostly thousands of years, with a few episodes as short as 400.
In the limit of largely obscured AGN, we find additional evidence for fading,
comparing lower limits from recombination balance and the maximum luminosities
derived from from infrared fluxes. We compare these long-term light curves to
simulations of AGN accretion; the strongest variations on these timespans are
seen in models with strong and local feedback. Gemini integral-field optical
spectroscopy shows a very limited role for outflows in these structures. While
rings and loops of emission are common, their kinematic structure shows some to
be in regular rotation. UGC 7342 exhibits local signatures of outflows <300
km/s, largely associated with very diffuse emission. Only in the Teacup AGN do
we see outflow signatures of order 1000 km/s. Clouds around these fading AGN
consist largely of tidal debris being externally illuminated but not displaced
by AGN outflows. (Abridged) | | Source: | arXiv, 1612.6006 | | Services: | Forum | Review | PDF | Favorites | |
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