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Spitzer IRS spectra
PKS1932-46
Spitzer IRS spectra
Dicken et al. (in preperation)
PK1932-46
Spitzer MIPS infrared photometric observations. Left to right: 24 microns, 70 microns and 160 microns (when available). FOV are 5x5 arcmins for 24 microns, 5x2.5 arcmins for 70 microns and 0.5x5 arcmins for 160 microns.
PKS1932-46
Top-left: Radio contours of the total intensity at 8.6 GHz with superposed vectors whose length is proportional to the fractional polarization
and whose position angle is that of the electric field. The contour levels are -1, 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024 × 4 mJy beam
−1 .
Top-right: Radio contours of the total intensity at 2.3 GHz with superposed electric field vectors. The contour levels are -1, 1, 2, 4, 8, 16, 32,
64, 128, 256, 512, 1024 × 4 mJy beam
−1 . Middle-left: depolarization between 5.8 and 8.6 GHz. Smaller squares represent smaller D values
(stronger depolarization). Square sizes range between D =0.19 (small squares) and 2.4 (large squares). Middle-right: depolarization between
2.3 and 5.8 GHz. Square sizes range between D =0.06 (small squares) and 1.6 (large squares) Bottom: Faraday rotation between 5.8 and 8.6
GHz. Filled squares are positive value of the rotation, open squares negative values.
![Wavelength/
Frequency Flux Units Reference
5GHz 3.47 Jy Morganti et al. (1993)
[OIII] λ5007 -13.88 Log erg/cm2/s Tadhunter et al. (1993)
15GHz core 16.4 mJy Dicken et al. (2008)
22 GHz core 21.5 mJy Dicken et al. (2008)
24 microns 2.5 mJy Dicken et al. (2008)
70 microns 17.6 mJy Dicken et al. (2008)
160 microns <36.5 mJy Dicken et al. (2008)
X-ray - - -](PKS1932-46_files/shapeimage_19.png)
Other name:
Redshift:
RA (j2000):
Dec (j2000):
Optical class:
Radio Class:
0.231
19 35 56.56
-46 20 40.7
BLRG
FRII
-
N
E
Gemini/GMOS-S: median filtered image
XMM
Notes
This galaxy has been the subject of three detailed studies by the 2Jy collaboration (Villar-Martin 1998, 2005; Inskip et al. 2007). Inskip et al. (2007) present a summary of the results of the most recent multi-wavelength study of this z = 0.23 radio source. Integral field unit spectroscopy using the Visible Multi-object Spectrograph (VIMOS) on the Very Large Telescope (VLT) was used to study the morphology, kinematics and ionization state of the extended emission-line region (EELR) surrounding this source, and also a companion galaxy at a similar redshift. Near- and far-infrared imaging observations obtained using the NTT telescope and Spitzer were also used to analyse the underlying galaxy morphologies and the nature of the active galactic nucleus (AGN).
The host galaxy is identified as an ∼M★ elliptical. Combining Spitzer mid-infrared (mid-IR) with X-ray, optical and near-IR imaging observations of this source, we conclude that its AGN is under-luminous for a radio source of this type, despite its status as a broad-line object. However, given its relatively large [OIII] luminosity it is likely that the AGN was substantially more luminous in the recent past (≲10^4 yr ago). The EELR is remarkably extensive and complex, reminiscent of the systems observed around sources at higher redshifts/radio powers, and the gas is predominantly ionized by a mixture of AGN photoionization and emission from young stars. We confirm the presence of a series of star-forming knots extending north–south from the host galaxy, with more prodigious star formation occurring in the merging companion galaxy to the north-east, which has sufficient luminosity at mid- to far-IR (MFIR) wavelengths to be classified as a luminous infrared galaxy (LIRG). The most plausible explanation of our observations is that PKS1932−46 is a member of an interacting galaxy group, and that the impressive EELR is populated by star-forming, tidal debris. We suggest that the AGN itself may currently be fuelled by material associated either with the current interaction or with a previous merger event. Surprisingly, it is the companion object, rather than the radio source host galaxy, which is undergoing the bulk of the star formation activity within the group (Inskip et al. 2007).
The BLRG PKS1932-46 shows an FRII morphology at radio wavelengths Villar-Martin et al. (1998). The deep r′ image for this source presented in Ramos Almeida et al. (2011a) shows an amorphous structure in the envelope of the elliptical host galaxy, as a well as an extraordinary series of interlinked arc structures to the N of the galaxy, that point to, but do not quite connect with, a tail/arm feature emanating from the NE companion galaxy. Spectral synthesis modelling of the nuclear spectrum of the host galaxy does not provide unambiguous evidence for a YSP, in part because of the contamination by strong AGN continuum emission associated with the BLRG nucleus (Holt et al. 2007). However, deep VLT spectra reveal a highly extended emission line nebula extended in an N–S direction with line ratios consistent with photoionization by hot stars, rather than by the AGN. This provides direct evidence for an extended population of very young (<10 Myr) stars in the halo of the galaxy (Villar-Martin et al. 2005).
PKS1932-46 is significantly polarized in the UV, with the polarization E-vector close to perpendicular to the radio axis. No broad permitted lines are detected in our optical spectra. It is likely that scattered AGN light makes a significant, but not dominant, contribution to the UV excess in this source. The BLRG classification of this source is based on multiple-Gaussian modelling of the Ha+[NII] blend by Villar-Martin et al. (2005)
Based on the extrapolation of the high frequency radio core component towards the infrared region of the spectral energy distribution, it is possible that the non-thermal core synchrotron emission may contaminate the MFIR flux in this radio galaxy (Dicken et al. 2008).
PKS1932-46
Spectral energy distribution. The blue solid line is fitted to the data from 109 to 1010 Hz. Extrapolating this line from the radio to the infrared SED tests whether non-thermal synchrotron emission from the lobes can contaminate the Spitzer mid-infrared flux. In this case the lobes emission lies out of the Spitzer beam so cannot contaminate the Spitzer data. However, extrapolating the, flat spectrum, radio core SED into the infrared, shows that the core synchrotron emission could be a possible source of non-thermal contamination to the thermal infrared flux.
