The time history and duty cycle of individual AGN is an important part of their evolution and the growth history of massive black holes, but almost unconstrained on scales between galaxy-interaction timescales (hundreds of Myr) and the scales of years probed by variability measurements. We propose a detailed study of an object which seems to be a large-scale light echo from a QSO-level episode in a nearby galaxy. The Galaxy Zoo morphological survey of SDSS objects has uncovered a peculiar emission-line structure whose spectrum matches the narrow-line region of AGN, despite lying at least 20 kpc from a galaxy whose activity is currently very weak. This is best explained if the nucleus has faded dramatically on time scales of several tens of thousands of years. We propose a suite of imaging and spectroscopic observations to probe its properties, and the time history of this episode of nuclear activity, measuring time scales hitherto unavailable.

We examine the nature and energy source of a newly-found cloud near the galaxy IC 2497 ("Hanny's Voorwerp") in several ways. STIS spectroscopy of the IC 2497 nucleus will seek highly-ionized AGN gas, and measure the stellar velocity dispersion. ACS ramp-filter exposures will map [O III] and H-alpha, comparison of which might show past fluctuations in the ionizing luminosity of the AGN, and include the central part of IC 2497 to seek highly ionized structures near the core. Finally, WFC3 exposures in the UV, I, and F160W bands will be used to look for star clusters in the cloud itself, to see whether it was originally a dwarf galaxy which was later disrupted. AGN/QUASARS 12 false 0.0 0.0 false false false false false SUPPORTED GALAXY EMISSION LINE NEBULA g=18.3 J2000 09 41 3.8000 +34 43 34.20 J2000 GALAXY NUCLEUS g(nucleus)=16.9 J2000 09 41 4.1500 +34 43 58.30 J2000 ACS/WFC RampFilter No No FR505N ACS/WFC RampFilter No No FR716N WFC3/IR Imaging No No F160W WFC3/UVIS Imaging No No F814W WFC3/UVIS Imaging No No F225W STIS/CCD Spectroscopic No No G430L 4300 STIS/CCD Spectroscopic No No G750L 7751 POS-TARG DITHER 0.145 LINE false false 2 47.23 LINE 1 false POS-TARG DITHER 0.145 LINE false false 2 46.84 WFC3-UVIS-DITHER-LINE 2 false POS-TARG DITHER 0.636 LINE false false 3 41.788 WFC3-IR-DITHER-LINE 3 false The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. STIS spectroscopy of the nucleus of IC 2497, seeking evidence of ongoing (even if obscured) nuclear actvity. The 0.2" slit is a compromise between rejection of the surounding starlight and throughput (plus speed of acquisition). Setups in blue and red (with fring flats) are used for one orbit each. (Tic-Visit :proposal-id 11620 :visit-id "01" :proposal-version -1 :trans-version "20080609" :date "01-Jul-2008 15:23:35.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 166112 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11620 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11620 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2928 :al-overhead-at-end 0 :internal-dur-at-end 201 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3283 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11620 :visit-id "01" :orbit-number 2 :pcs-time 195 :si-vis-utilization 2844 :al-overhead-at-end 75 :internal-dur-at-end 362 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3283 :pcs-gap 0 ) true 2 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. Narrowband images in [O III] and H-alpha at z=0.05. 2-point dither pattern, 2x2 pixels to reject hot pixels and keep the whole ramp-filter field. To keep two targets in monochromatic fields, orientation is restricted to two ranges and center point is offset from target cordinates (to maximize rangle of usable angles). (Tic-Visit :proposal-id 11620 :visit-id "02" :proposal-version -1 :trans-version "20090130" :date "30-Jun-2009 14:39:47.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 1136896 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11620 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11620 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2948 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3283 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11620 :visit-id "02" :orbit-number 2 :pcs-time 195 :si-vis-utilization 3083 :al-overhead-at-end 0 :internal-dur-at-end 349 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3283 :pcs-gap 0 ) true 2 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. Broadband continuum images (UVIS and IR) of the cloud known as Hanny's Voorwerp are used to seek underlying stelar populations, to tell whether it was originally a dwarf galaxy later disrupted and illuminated by IC 2497. Simple 2- and 3-pont linear dithers are used for hot-pixel rejection. (Tic-Visit :proposal-id 11620 :visit-id "03" :proposal-version -1 :trans-version "20080609" :date "01-Jul-2008 15:28:40.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 1990592 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11620 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11620 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2863 :al-overhead-at-end 0 :internal-dur-at-end 90 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3283 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11620 :visit-id "03" :orbit-number 2 :pcs-time 195 :si-vis-utilization 3088 :al-overhead-at-end 116 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3283 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11620 :visit-id "03" :orbit-number 3 :pcs-time 195 :si-vis-utilization 3088 :al-overhead-at-end 116 :internal-dur-at-end 670 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3283 :pcs-gap 0 ) true 3 0