The Astrophysical Journal, 708:171–187, 2010 January 1 doi:10.1088/0004-637X/708/1/171 C 2010. The American Astronomical Society. All rights reserved. Printed in the U.S.A. A MULTI-WAVELENGTH SPECTRAL AND POLARIMETRIC STUDY OF THE JET OF 3C 264 E. S. Perlman1,2, C. A. Padgett2,3, M. Georganopoulos2,3, D. M. Worrall4, J. H. Kastner5, G. Franz5,M.Birkinshaw4, F. Dulwich4,C.P.O’Dea5,S.A.Baum6, W. B. Sparks7, J. A. Biretta7,L.Lara8,10, S. Jester9, and A. Martel7 1 Physics and Space Sciences Department, Florida Institute of Technology, 150 West University Boulevard, Melbourne, FL 32901, USA; eperlman@fit.edu 2 Department of Physics, University of Maryland-Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA 3 NASA’s Goddard Space Flight Center, Mail Code 660, Greenbelt, MD 20771, USA 4 Department of Physics, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, UK 5 Physics Department, Rochester Institute of Technology, 84 Lomb Memorial Drive, Rochester, NY 14623-5603, USA 6 Center for Imaging Science, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623-5603, USA 7 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA 8 Dpto. Fis´ıca Teorica´ y del Cosmos, Universidad de Granada, Avenida Fuentenueva s/n, 18071 Granada, Spain 9 Max Planck Institut fur Astronomie, Konigstuhl¨ 17, D-69117 Heidelberg, Germany Received 2009 August 14; accepted 2009 November 5; published 2009 December 9 ABSTRACT We present a comprehensive multi-band spectral and polarimetric study of the jet of 3C 264 (NGC 3862). Included in this study are three Hubble Space Telescope (HST) optical and ultraviolet polarimetry data sets, along with new and archival Very Large Array radio imaging and polarimetry, a re-analysis of numerous HST broadband data sets from the near infrared to the far ultraviolet, and a Chandra ACIS-S observation. We investigate similarities and differences between optical and radio polarimetry, in both degree of polarization and projected magnetic field direction. We also examine the broadband spectral energy distribution of both the nucleus and jet of 3C 264, from the radio through the X-rays. From this, we place constraints on the physics of the 3C 264 system, the jet and its dynamics. We find significant curvature of the spectrum from the near-IR to ultraviolet, and synchrotron breaks steeper than 0.5, a situation also encountered in the jet of M87. This likely indicates velocity and/or magnetic field gradients and more efficient particle acceleration localized in the faster/higher magnetic field parts of the flow. The magnetic field structure of the 3C 264 jet is remarkably smooth; however, we do find complex magnetic field structure that is correlated with changes in the optical spectrum. We find that the X-ray emission is due to the synchrotron process; we model the jet spectrum and discuss mechanisms for accelerating particles to the needed energies, together with implications for the orientation of the jet under a possible spine-sheath model. Key words: galaxies: active – galaxies: elliptical and lenticular, cD – galaxies: jets – polarization – radiation mechanisms: non-thermal Online-only material: color figures 1. INTRODUCTION PKS 1136–135—M. Cara et al. 2010, in preparation). This is in comparison to the ∼34 detected optical extragalactic The characterization of jet polarization properties provides jets.11 Given this dearth of polarimetry observations, it is not a powerful diagnostic of jet physics, particularly with respect surprising that there are few constraints on the configuration of to magnetic field configuration and particle acceleration. Ex- the magnetic fields in optically emitting regions of extragalactic tragalactic jets generally emit a continuum of radiation from jets. Here, we present a comprehensive study of the jet of 3C radio through optical, and often into the X-ray regime. Through 264 that includes radio and optical polarimetry, as well as X-ray matched resolution comparisons of flux density measurements observations of the jet. at various frequencies, we can glean morphological information At a redshift of 0.0217 (Baum et al. 1990), and hence a about particle acceleration regions and jet energetic structure. distance of 94 Mpc, 3C 264 is among the closest known The closest kiloparsec-scale radio–optical jet is that of M87 at bright radio galaxies with an optical jet. Also detected at a distance of 16 Mpc (Tonry 1991). By using matched resolution X-ray energies, its relative proximity makes the 3C 264 jet a polarimetry at different wavelengths and combining this with prime candidate for deep optical, radio and X-ray studies, as we multi-wavelength imaging and X-ray imaging and spectroscopy, present here. It is hosted by NGC 3862, a large elliptical galaxy much information about jet energetics and magnetic fields, offset to the south–east from the center of the cluster Abell three-dimensional structure and particle acceleration can be 1367, and is classified as a Fanaroff–Riley type I radio source constrained (Perlman & Wilson 2005 and references therein). (Fanaroff & Riley 1974). On large scales, it exhibits a twin- There are relatively few jets for which there exists Hubble Space tail radio structure extending to the north–east (Bridle & Vallee Telescope (HST) optical polarimetry compared to the number 1981). On arcsec scales, it consists of a compact core, with that have been detected. As of this writing, a total of 10 optical a one-sided, nearly knot-free jet extending also to the north– jets have HST polarimetry observations (M87—e.g., Perlman east and a weak counter jet (Lara et al. 1997). The optical jet et al. 1999; 3C 273—Thomson et al. 1993; 3C 293—Floyd counterpart extends for only roughly 2 beyond the galaxy core, et al. 2006; 3C 15—Perlman et al. 2006 and Dulwich et al. the latter arcsecond of which is considerably fainter than the 2007; 3C 346—Perlman et al. 2006 and Dulwich et al. 2009; inner jet (Perlman et al. 2006). This short length combined with 3C 66B, 3C 78, 3C 264, and 3C 371—Perlman et al. 2006; the “smoothness” of the jet makes studying this object difficult. 10 Deceased 11 See http://home.fnal.gov/∼jester/optjets/ maintained by S. Jester. 171 172 PERLMAN ET AL. Vol. 708 Table 1 HST Observations a b c d Instrument Filter/Polarizer λ0 FWHM Num Exp Obs Date Time (s) WFPC2/PC F702W 6919 1382 2 1994 Dec 24 280 WFPC2/PC F606W 5997 1502 1 1995 Apr 16 500 WFPC2/PC F791W 7881 1224 2 1996 May 19 750 WFPC2/PC F547M 5483 484 2 1996 May 19 900 NICMOS/NIC2 F110W 11285 3844 4 1998 May 12 448 NICMOS/NIC2 F160W 16030 2772 4 1998 May 12 448 NICMOS/NIC2 F205W 20714 4314 4 1998 May 12 896 STIS/NUV-MAMA F25QTZ 2354 995 1 2000 Feb 12 1800 STIS/FUV-MAMA 25MAMA 1374 318 1 2000 Feb 12 1705 STIS/FUV-MAMA F25SRF2 1469 281 1 2000 Feb 12 1700 WFPC2/PC F702W 6919 1382 9 2002 Mar 30 1400 ACS/HRC F606W/POL0V 5895 1588 2 2002 Dec 05 300 ACS/HRC F606W/POL60V 5895 1588 2 2002 Dec 05 300 ACS/HRC F606W/POL120V 5895 1588 2 2002 Dec 05 300 ACS/HRC F330W/POL0UV 3372 410 2 2002 Dec 05 300 ACS/HRC F330W/POL60UV 3372 410 2 2002 Dec 05 300 ACS/HRC F330W/POL120UV 3372 410 2 2002 Dec 05 300 WFPC2/PC F555W/POLQe 5439 1232 8 2003 Mar 06 6500 WFPC2/PC F555W/POLQe 5439 1232 8 2003 Apr 25 6500 WFPC2/PC F555W/POLQe 5439 1232 8 2003 Jun 01 6500 Notes. a Pivot wavelength of filter in Å. b Approximate FWHM of filter bandpass in Å. c Number of images in raw data set (including CR-SPLITs). d Total integration time of all images in seconds. e Due to non-rotatability of the WFPC2 polarizer (POLQ), HST was allowed to precess between observations over a ∼2 month time period, simulating the nominal polarizer angles of 0◦,60◦, and 120◦. See the text for details. In particular, in the optical and near-IR useful observations are (corresponding to the latest WMAP cosmology, see Dunkley really only possible with HST, as most adaptive-optics systems et al. 2009), giving a projected linear scale of 0.42 kpc arcsec−1. require a nearby, bright point source. 3C 264 was part of the original Third Cambridge Catalog 2. OBSERVATIONS AND DATA REDUCTION with S159 MHz = 37 Jy (Edge et al. 1959) and the optical jet counterpart was discovered by Crane et al. (1993) with the pre- We obtained polarimetric observations of 3C 264 with the COSTAR Faint Object Camera (FOC) instrument on HST. Since WFPC2 instrument aboard HST as part of the Cycle 10 ob- this initial optical discovery, over 50 ks of HST observing time serving program GO-9142. As part of this same proposal, we has been dedicated to this source alone (e.g., Crane et al. 1993; obtained 38.3 ks of Chandra observations of this source. We Baum et al. 1997, 1998; Hutchings et al. 1998; Martel et al. also observed this object with the VLA in both A and B configu- 1999, 2000; Noel-Storr et al. 2003). More recent observations rations at 8.5 GHz and 22.5 GHz as part of observing program have concentrated on deep optical polarimetry with WFPC2 AP0439. Further observations in many wave bands and instru- (Perlman et al. 2006) and optical and UV polarimetry with the ment configurations with HST have been taken from the online HST Advanced Camera for Surveys (ACS) (Capetti et al. 2007). data archives (Table 1).