Hi all . . . I’m visiting Civilization At Last after a long spell out at the farm. It’s nice to hear from something else besides 300 sheep. Based on what Patrick observed and Robert wrote, you have chanced on a very interesting galaxy pair that the professionals have analyzed only perfunctorily. IC 4329A has such a bright core that as recently as 1979 it was identified as a quasar. (There is a nearby quasar, but adjacent to 4329A and far more remote.) Today, as Robert says, it’s known as a highly luminous Seyfert (Lx=6×10^43 erg s-1). Only one recent paper (2012) barely mentions IC 4329 itself in passing, and a 2009 Harris paper is devoted to the not particularly remarkable C-M properties of 4329’s globular system. All the rest of the 15 papers about this pair trail backwards from 1998 back to the 1970s.
I wonder if Patrick might have another look at both these galaxies’ cores again to see if 4329 has a softer stellar appearance compared with 4329A. His original observation of July 1 said as much; I’m wondering if a second look would reveal any more.
As for its neighbour 4329A, its hot AGN core and has two powerful magnetic fields parallel to the disc.
This 1995 paper says: ‘The edge-on dust lane of IC 4329A shows significant levels of polarization oriented parallel to the lane, which suggests that there is a magnetic field in the plane of this galaxy which is uniform on kpc scalelengths. Although the Seyfert 1 nucleus is seen through the polarizing dust lane, it appears to have an additional, intrinsically polarized component with a position angle approximately parallel to the galactic plane. We suggest that the intrinsic nuclear polarization arises from dust scattering in an asymmetric geometry, possibly involving an inner torus, surrounding the central AGN. The relative orientations of the axes of the AGN and the disc of the host galaxy may have been influenced by a recent interaction between IC 4329A and its massive neighbour IC 4329.’
http://heasarc.gsfc.nasa.gov/images/...ies/ic4329.gif
Above is an image to show what they mean about the xray corona and intragroup shock-front bubble.
I see that 4329 is variously identified as a lenticular (S0) and an elliptical (SIMBAD merely IDs it s ‘Es D’. I’m not sure what ‘Es D’ means, either.) Robert has been writing quite a bit about S0 lenticulars lately and I think he’s right in two ways about this pair: (a) 4329 looks like a small-bulge, large-disc S0 and not an E, and (b) the pair are closer than their stated 59 Mpc. It’s interesting than a hobbyist looking through an eyepiece can spot a likely misidentification the pros do not. The few relevant IC 4329 distance studies are old (1995-98) and based on CCD photometry rather than enhanced hi-rez .01 mag-capable spectrography. Spectrographic signal-to-noise capability back in those days were 30- to 40-to-1 where now they are 120-to-1. These galaxies are so xray bright that IR and radio studies have not much dwelt on them.
A 1998 paper
says as much without following through: ‘ The soft component of the residual emission may be a larger version of the superwinds seen around some ultraluminous far-infrared galaxies, or may even represent a stripped wake of intragroup gas.’ The ‘stripped wake’ was right but they dropped the follow-through on ‘infrared’. If our eyes could see in the H, J, & K bands of the IR, these two would be as bright as Cen A!
In short, these two need a re-look with up-to-date equipment. Good on you, Patrick, for bringing this orphan pair back into the limelight!
=Dana in SA