THE HISTORY AND ENVIRONMENT OF A FADED QUASAR: HUBBLE SPACE TELESCOPE OBSERVATIONS OF HANNY'S VOORWERP AND IC 2497

We present Hubble Space Telescope imaging and spectroscopy, along with supporting Galaxy Evolution Explorer and ground-based data, for the extended high-ionization cloud known as Hanny's Voorwerp, near the spiral galaxy IC 2497. We find no high-ionization gas near the nucleus, adding to the evi...

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Bibliographic Details
Published inThe Astronomical journal Vol. 144; no. 2; pp. 1 - 16
Main Authors Keel, William C, Lintott, Chris J, Schawinski, Kevin, BENNERT, VARDHA N, Thomas, Daniel, Manning, Anna, CHOJNOWKI, DREW, Van Arkel, Hanny, Lynn, Stuart
Format Journal Article
LanguageEnglish
Published United States 01.08.2012
Subjects
ASTRONOMY
ASTROPHYSICS
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
BLACK HOLES
BRIGHTNESS
CAMERAS
Clouds
COSMIC DUST
EMISSION SPECTRA
FINE STRUCTURE
GALAXY NUCLEI
Hubble Space Telescope
Imaging
Integrated circuits
IONIZATION
LUMINOSITY
PHOTON EMISSION
QUASARS
SEYFERT GALAXIES
STARS
TELESCOPES
VISIBLE SPECTRA
X-RAY SPECTRA
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Summary:We present Hubble Space Telescope imaging and spectroscopy, along with supporting Galaxy Evolution Explorer and ground-based data, for the extended high-ionization cloud known as Hanny's Voorwerp, near the spiral galaxy IC 2497. We find no high-ionization gas near the nucleus, adding to the evidence that the AGN is currently at a low radiative output (perhaps with the central black hole having switched to a mode dominated by kinetic energy). Narrowband [OIII] and H alpha +[NII] Advanced Camera for Surveys images show fine structure in Hanny's Voorwerp, including limb-brightened sections suggesting modest interaction with a galactic outflow and small areas where H alpha is strong. These results fit with our picture of an ionization echo from an AGN whose ionizing luminosity has dropped by a factor > 100 within the last (1-2) x 10 super(5) years; we suggest a tentative sequence of events in IC 2497 and discuss implications of such rapid fluctuations in luminosity for our understanding of AGN demographics.
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ISSN:0004-6256
1538-3881
1538-3881
DOI:10.1088/0004-6256/144/2/66