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The Very Extended Ionized Nebula around the Quasar MR2251-178

P. L. Shopbell, S. Veilleux ¹
Department of Astronomy, University of Maryland, College Park, MD 20742; pls,veilleux@astro.umd.edu

J. Bland-Hawthorn
Anglo-Australian Observatory, P.O. Box 296, Epping, NSW 2121, Australia; jbh@aaoepp2.aao.gov.au

Abstract:

We report the results of deep H imaging of the ionized gas surrounding the low-redshift (z=0.0638) quasar MR 2251-178 using the TAURUS Tunable Filter (TTF) on the Anglo-Australian Telescope. Our observations reach a 2- detection level of 5 10^-18 erg s^-1 cm^-2 arcsec^-2, more than an order of magnitude deeper than conventional narrowband images previously published on this object. Our data reveal a spiral complex that extends more or less symmetrically over  kpc, making it the largest known quasar nebula. The total mass of ionized gas is  M (upper limit), a large fraction of which is in a very faint, diffuse component. The large and symmetric extent of the gaseous envelope favors a model in which the filamentary and diffuse emission arises from a large cloud complex, photoionized by the bright quasar. A crude kinematic analysis reveals relatively smooth rotation, suggesting that the envelope did not originate with a cooling flow, a past merger event, or an interaction with the nearby galaxy G1.

Keywords: quasars: individual (MR 2251-178); galaxies: halos; quasars: general; intergalactic medium; instrumentation: spectrographs

A Postscript version of this document is also available.

• Introduction
• Observations and Reductions
• Discussion
  • Morphology
  • Kinematics
  • The Origin of the HII Envelope
  • The Ionization of the HII Envelope
• Summary and Future Directions
• Bibliography
• About this document ...