AGN jet project

Bob Fosbury, December 2003, Updated, July 2005
As you will remember, we submitted a P74 proposal to ESO to do imaging and spectroscopy of this object. We only received time for the WFI imaging part ([OIII] and continuum imaging) and, in the end, we only obtained about one third of the requested exposure time. However, these data are not without interest and Gijs, Clive and Bob have been discussing them following Gijs' preliminary reduction. The new aspect of the data is the detection of both the northern and southern radio hotspots in the V-band. These sources have also recently been detected with Chandra in the X-ray band. See the papers by Ly et al. (2005) and by Young et al. (2005). Our recent discussions are reported below - following the notes written at the end of 2003.

Participants

Purpose

The aim of this project is to understand the radiation field emitted by the jets emerging along the spin axes of AGN. In particular, we propose to make an observational study of the ionizing radiation produced by the jets by examining its effects on material within and near the host galaxy.

Notes

Radiation mechanisms

Flows

Previous observational results

The story of PKS2152-699

This is just a brief, illustrated summary of unfinished work that adds to the existing literature. In addition to the HST imaging in F606W and F300W, there is some FOS spectroscopy of the nucleus and HIC that, unfortunately, suffered from a failed target acquisition and had slightly displaced apertures (GO 6696). See the aperture design overlay on the HST NUV image.

These are the four papers that describe our previous work on this object. 


\bibitem[Tadhunter et al.(1987)]{1987Natur.325..504T} Tadhunter, C.~N., 
Fosbury, R.~A.~E., Binette, L., Danziger, I.~J., \& Robinson, A.\ 1987, 
\nat, 325, 504 

\bibitem[di Serego Alighieri et al.(1988)]{1988Natur.334..591D} di Serego 
Alighieri, S., Courvoisier, T.~J.-L., Fosbury, R.~A.~E., Tadhunter, C.~N., 
\& Binette, L.\ 1988, \nat, 334, 591

\bibitem[Tadhunter et al.(1988)]{1988MNRAS.235..403T} Tadhunter, C.~N., 
Fosbury, R.~A.~E., di Serego Alighieri, S., Bland, J., Danziger, I.~J., 
Goss, W.~M., McAdam, W.~B., \& Snijders, M.~A.~J.\ 1988, \mnras, 235, 403

\bibitem[Fosbury et al.(1998)]{1998MNRAS.296..701F} Fosbury, R.~A.~E., 
Morganti, R., Wilson, W., Ekers, R.~D., di Serego Alighieri, S., \& 
Tadhunter, C.~N.\ 1998, \mnras, 296, 701

The overall SED of PKS2152-699 from radio to X-ray shows that the HIC almost 'mirrors' that of the nucleus of the galaxy. However, the very blue optical/NUV continuum in the HIC is reminiscent of Rayleigh scattering and there is evidence for this in the optical polarization measurement by di Serego et al. (1988) - see above. You can see that, around 300nm, the HIC is nearly as bright as the AGN.

In the visible, the HST (F606W) image of the HIC shows a complex set of blobs/filaments with the ATCA radio source displaced to the eastern side. Another version of the image with two different cuts gives a clearer picture if the HIC and other structures. The ROSAT HRI X-ray source (unpublished - but work done by Tim Bedding), however, is significantly removed from the radio and is apparently coincident with the optical/UV source. The HST image also shows structures in the direction of the counter-jet. This is all rather reminiscent of the behaviour in Cen A.

In the UV, the HST F300W image shows the similar brightness of the HIC and the galaxy AGN and reveals a 'helical' downstream trail. The relationship between the optical and NUV images can best be seen in this little animated gif where we start with the F606W image (only cr-cleanded in the central regions!) and then overlay the F300W contours. Incidentally, the HST NUV images are taken using the polarizers but have yet to be properly analysed (another job to do!)

There is a cartoon that shows the various positions and position angles (with the exception of the X-ray that needs to be added). This includes the VLBI jet which points directly to the centre of the HIC. The ATCA radio images (from the Fosbury et al. paper above) are shown here:

The other interesting discovery we made, but have not yet followed up in detail, is the existence of distant [OIII] emission clouds that appear to be confined to the radio axis - though our imaging field with the NTT is not really large enough to do a proper count. Raffaella and Tom Osterloo have been working on this and they would be, I'm sure, delighted if we all could take this further! An NTT [OIII] image is overlayed with the radio map. There are also three representative optical spectra showing that one of the distant clouds (top) has a high ionization state.

Preliminary look at CHANDRA image

Diana extracted the 15ks observation from the archive: see the following email. 

From: Diana Worrall 
Date: Mon Dec 15, 2003  7:35:44  pm Europe/Rome
To: rfosbury@eso.org
Cc: d.worrall@bris.ac.uk
Subject: quick look at the Chandra data.....
Attachments: There is 1 attachment



Dear Bob,

   See attached PostScript file with quickest of quick looks at
the Chandra data.

  The image on the left is almost raw (i.e., just counts and first
pass at their coordinates, with no background subtraction or vignetting
or exposure corrections).  That on the right is the same with a 1 arcsec
Gaussian smoothing.

   On first look, the core, radio knot/HIC, and probably
the radio hotspots in each of the N and S lobes, are showing up
in the X-ray.  I'll need to check the registration of the X-ray image and
then we could do some careful overlays to see how the
emission close to the radio knot/HIC lines up.  Since it looks like
the lobe hotspots are detected (in addition to the core), the
final image registration should be quite reliable, which is terrific.

There are of order 2700 X-ray counts in the core which will give a
reasonable spectrum (I need to check it's not too piled up), and probably
over a couple of hundred in the NE
feature, which will give some indication of spectral shape, at least.
Of course fluxes will be reasonably well measured.
It looks to me like there may possibly be some resolved jet emission
between them.
Also, it looks like diffuse X-ray-emission associated with the host galaxy
is beeing detected.

What a nice observation!

-Diana


+------------------------------------------------------------------+
| Dr. Diana M. Worrall    | Dept. Physics, University of Bristol,  |
| Reader in Physics       | Tyndall Avenue, Bristol BS8 1TL, U.K.  |
| D.Worrall@bristol.ac.uk | Tel 44 (0)117 928 8787  Fax...925 5624 |
+------------------------------------------------------------------+

I have done two rough overlays on the optical and radio data:

This appears, at first sight, to be consistent with the ROSAT HIC position (displaced from the radio). If the raw Chandra image is to be believed, there seem to be X-ray components located on both the head of the HIC and at the position of the radio source. It would be most interesting to observe the optical/IR spectra of both these regions! We may see quite different physics operating...

Jobs

  1. Collect and reduce all HST imaging
  2. Look again at FOS spectroscopy
  3. Do F300W polarimetry (ECF web info.)
  4. Reduce and overlay the Chandra data. Do what spectroscopy we can

July 2005 discussion

During a visit to Sheffield on 20-22 July, Bob, Clive and Gijs (by telecon) discussed the following points and reached preliminary conclusions (italics).

1. The optical detection of the NE and SW radio hot-spots from our WFI data. These are also seen by Chandra. We need good astrometry and flux cal. to compare with the radio and X-ray images.

Gijs will work on the calibration of our own WFI data during his visit to ESO in August. The aim is to calibrate the line and continuum image and extract the hot spot fluxes. We reserve the possibility to examine the deep WFI R-band image from Jarvis et al when the data become public in October. Given the relatively small number of sources which have radio-to-X-ray hot spot SED, we can use our data do investigate inverse Compton vs. synchrotron models (Diana?). Here is a rough-and-ready overlay of our old [OIII] and radio data on the new WFI V-band image.

2. Confirmation of the distant line-emitting clouds over a wide FOV - admittedly to a higher flux limit than we wanted. We get limits on their azimuthal distribution.

We will use the line and continuum images to survey for line-emitting clouds.

3. A presentation of the UV morphology of the HIC from our own HST observations (do we try to extract polarimetry - interesting given the possibility of the scattering model discussed by Young?)

We create an intensity image from the HST UV data - don't try to get polarimetry from it now. The morphology is interesting in the context of the interaction, shocks etc.

In addition, we can estimate the coronal emission line flux from the thermal X-ray model (as we did years ago for the ROSAT proposal but now using the X-ray-deduced temperature...

Compute the expected [FeX] flux from the X-ray model. Also look at the predictions for other observable coronal lines (Luc?). These can be used to justify more spectroscopy.

The Jarvis et al. data will become available from the ESO archive in October 2005. See this list of relevant images.