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Old 01-07-2013, 08:04 PM
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Paddy (Patrick)
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Abell galaxy cluster 3574 and some Ophiuchus GCs

I've been wanting to properly explore Abell cluster 3574 near Messier 83 for quite some time but the transparency has been abysmal for any but the brightest galaxies. Last Friday was my chance.

The sky got more moist as the night went on so after the Abell cluster, I headed to Ophiuchus for some GCs. Did find HP 1, but Ton 2 in Scorpius eluded me.

Thanks for reading.

Telescope 400mm f4.9 tri-dob reflector
Eyepieces 28mm UWAN, 17 Ethos ,13,9 mm Naglers, Paracorr
Navigation: Uranometria

p= preceding
f= following

2100 Seeing good, transparency good

Abell 3574 Galaxy cluster in Hydra

NGC 5292 GX Hydra

175x 2’x1.5’ N-S oval glow with distinct central brightness and a foreground star at the northern edge of the disc.

NGC 5302,5298, M5-33-10 ESO 445-44 & ESO 445-46 GX in Hydra

175x These three form a slightly flattened triangle of faint round luminosities 15’ to the N and slightly preceding of the following pair of a 2 foreground stars separated by 10’ . The southernmost and brightest is NGC 5302, a 2’ glow with perhaps a faint stellar central brightness. NGC 5298 is also about 2’ across and forms the apex of the triangle and I have the impression of a faint galaxy just to its Np, M-5-33-10 being fainter again but about the same size. 2/3 of the way from NGC 5302 to the preceding star of the aforementioned pair is the small, faint glow of ESO 445-44. 5’ Sf to the other star is the 2’x1’ faint glow of ESO 445-46

NGC 5291 & M 5-33-5 GX in Hydra

175x A line from NGC 5302 through M 35-33-10 and extended for 16’ leads to the small 1’ round glow of NGC 5291 with bright centre and 1’ S of it is the faint 1’ glow of M 5-33-5 ( the seashell galaxy, but not visually anyway!)

IC 4329, 4329A & 4327 GX in Hydra

175x 15’ Nf of NGC 5298 is the distinct soft 3’x1.5’ glow of IC 4329 with an obvious 30” brightness at its centre. 4’ f is the smaller but still distinct IC 4329A also with marked central brightness. 4’ p 4329 is the very faint glow of IC 4327

Also visible are the small glow of M 5-33-23 28’ f IC 4329 and 20’ to the N of this ESO 445-54. Larger but also very faint is IC 4328, 20’ to the N of IC 4327, no central brightness observed.

Other faint galaxies were just visible in the field, but I was unable to identify or describe them.

Messier 62 NGC 6266 GC in Ophiuchus

175x Spectacular 12’x7’ GC with countless resolved stars and a distinct core. The halo looks more extended and scattered to the N with a big spray of stars out to the Np

NGC 6293 GC in Ophiuchus

175x much more modest than nearby M 62, this is still a very pleasing 5’ dia GC, quite concentrated and with many resolved stars .

Messier 19/NGC 6273 GC in Ophiuchus

175x A very intriguing GC – a round 3’dia central concentration within a flattened 7’x5’ halo, elongated N-S. A plethora of resolved stars makes this a stunning sight.

NGC 6248 GC in Ophiuchus

175x 3’ dia, round grainy and compact GC with no marked central brightness.

Haute Provence 1 (HP1) GC in Ophiuchus

175x Very faint circular glow just visible, perhaps 1.5-2’ dia, but hard to pick the edges.
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Old 12-07-2013, 09:05 AM
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madbadgalaxyman (Robert)
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Good observation of IC 4329A, Paddy!

It seems to me that you are plainly seeing the stellar-like Active Galactic Nucleus of this galaxy; the edge-on disk galaxy IC 4329A has a very very luminous Seyfert Nucleus; one of the most prominent of these objects which are accessible to the amateur telescope.

Here is a picture of IC4329 and IC 4329A:

Click image for larger version

Name:	I4329_I band___(with CTIO 0.9m)_(6.5 mins field)__[2000__ApJS__128_479]_______log scale).jpg
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(this is an I band (800nm) image, displayed at a log scale so as to show both the central parts and the outer parts of these galaxies)

Here is a closeup of IC 4329A:

Click image for larger version

Name:	I4329A__B+V+R+I___(B_BESS)(V_BESS)(R_SPECIAL)(I_BESS)__(with FORS2)__[by Manuel Mejias (flickr u.jpg
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__________________________________

The central feature in IC 4329(a big elliptical galaxy), is also very bright;
as you perceptively remarked in your observing notes.
This is not a star-like central feature; so one wonders if it might be distinct from the rest of its host galaxy..... in terms of its structure, the ages of its stars, its rotational properties, and the orbital structures of its constituent stars.

The Hubble Classification of IC 4329 is 'probably an elliptical galaxy', but the vast distended envelope visible in photographs looks a bit like it might have disky characteristics; so if IC 4329 were a two-component "disk+bulge" system, it would be classified as Hubble type S0.

Of late, I have been leaning towards assigning IC 4329 to the S0 morphological class, albeit a "very mild S0 morphology"

P.S.
"The Seashell" must be one of the toughest challenges for visual observers.
Attached Thumbnails
Click for full-size image (I4329A_(1)_F606W_(HST&WFPC2)(2006_AJ_132_321)(www.chara.gsu.edu(slash)~deo(slash)research(slash).gif)
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Last edited by madbadgalaxyman; 12-07-2013 at 03:23 PM.
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Old 17-07-2013, 11:14 AM
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Paddy (Patrick)
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Thanks Robert for another of your very illuminating posts. They really add something to the whole process of observing.
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Old 17-07-2013, 07:06 PM
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Hi Paddy,

It is impressive to be able to visually detect a single star-like source at such an enormous distance. Some papers give the distance of this cluster of galaxies as 190 million light years.

You are a very careful observer, often picking up interesting features, even within challenging objects. That is why I find it valuable to inform you about the range of phenomena which are potentially visible in galaxies, even without the use of CCDs etc.

N5292 is an interesting and luminous outlier of the cluster; in this Galex ultraviolet image, there is a very large ring structure in its central regions that might accord with what you have observed:

Click image for larger version

Name:	N5292_FUV+NUV__(with GALEX)(GalexView virtual telescope)___(2)__interesting Luminous outlier of .jpg
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ID:	143835

[ Could look like a large diffuse annulus or ring, visually]

This must be one of the least known members of the population of (relatively) bright galaxies!

Blue 13th magnitude might not seem too bright for a galaxy, but considering the large distance of this galaxy, NGC 5292 is a most impressively luminous spiral.(at least comparable to M100 and M99 and M61, which are the first ranked spirals in the Virgo Cluster)

Actually, NGC 5292 might be as bright as B= 12.5 (large discrepancy between various catalog magnitudes)

cheers,
Robert

Some thoughts Regarding the distance of Abell 3574

The distance of this cluster of galaxies is usually given as 58 Megaparsecs (= 189 million light years), but mostly this distance has been derived using not-very-accurate methods of distance determination;
such as the Tully-Fisher relation and Velocity Distances.

This distance estimate could very easily be wrong by as much as 15 -20 percent (if not a little more).

In fact, the galaxies of Abell 3574 (= the IC 4329 group of galaxies) seem of remarkably large angular sizes compared to the angular sizes of the galaxies of the Centaurus Cluster of Galaxies (N4696, N4709, etc., etc., etc.) despite the fact that the Centaurus Cluster (= Abell 3526) is supposed to be significantly closer than Abell 3574.

At face value, it seems to me that Centaurus Cluster could be further away than is usually thought and/or Abell 3574 could be closer than usually thought.

The degree of resolution of the galaxies in Abell 3574 would be remarkable if it is nearly 200 million light years away. These galaxies seem to be too large and too easy to observe to be this far away!
(as a comparison, the Virgo Cluster is 50 million light years away)

The recession velocity of this cluster is often given as about 4870 km/s in the CMB reference frame, a velocity which also yields a very large distance, for plausible values of the Hubble Constant. However, I note that Richter in 1984, A&AS, 58, 131 gives only 4253 km/s as a mean velocity of this cluster (corrected to the centroid of the Local Group).
So there can be a lot of error in estimating the true cosmological velocity of a cluster of galaxies. (not forgetting that there is a 1500 km/s peculiar velocity in the line-of-sight of one of the subclusters of the Centaurus Cluster!)

In general, the IC 4329 group is remarkably poorly known and studied compared to similar clusters in the Northern sky!!
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Last edited by madbadgalaxyman; 21-07-2013 at 10:35 PM.
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Old 17-07-2013, 07:37 PM
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Oh, one more thing, here is the image of N5292 from the Carnegie-Irvine survey;

Click image for larger version

Name:	NGC5292_color.jpg
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ID:	143836
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Old 17-07-2013, 09:35 PM
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Quote:
Originally Posted by madbadgalaxyman View Post
Oh, one more thing, here is the image of N5292 from the Carnegie-Irvine survey;

Attachment 143836
Robert, there is a star in UCAC4 right on top of IC4329

Code:
Cat    RA              Dec           Type    Name                Magn.       Field:Value ...
PGC    13h49m53.02s    -30°21'53.9"    Gx    IC4329              m:12.24     PGC:49025    Dim: 4.7 x 2.7 '    pa: 67    rv: 4515    
4UC    13h49m53.03s    -30°21'54.2"    *     UCAC4-299-072996    mV:13.56    b-v: 1.08    pmRA: -3 [mas/y]    pmDE: -6 [mas/y]    flags: 8
Is this the "star like structure" you referred to earlier?
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Old 17-07-2013, 11:01 PM
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Originally Posted by mithrandir View Post
Robert, there is a star in UCAC4 right on top of IC4329

Is this the "star like structure" you referred to earlier?
Hi Mithrandir,

No, I am referring to the star-like nucleus of the edge-on spiral galaxy IC 4329A (this galaxy is near to the big elliptical IC 4329.)

The 'star' at the centre of IC 4329A appears to be a bona fide Active Galactic Nucleus located within its host galaxy. (Dr William Keel says so, and he is an AGN expert.)

I therefore assume that it has been spectroscopically identified as such (same redshift as its host galaxy, very very Strongly Broadened spectral lines, etc.)

IC 4329 itself seems to have some sort of very-bright central feature, but this feature is diffuse in appearance; the central profile (at small galactocentric radii) of increasing surface brightness vs. decreasing galactocentric radius..... is very steep in this galaxy.

Cheers,
Robert

"A Catalog of Quasars and Active Nuclei" by Veron-Cetty and Veron, classifies the nucleus of IC 4329A as being a Seyfert 1 nucleus.
___________________________


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Do you practise magic, like your famous namesake(Olorin)(Tharkun)(Incanus) ?
___________________________________
Attached Thumbnails
Click for full-size image (I4329__g' band__(with Gemini-South & GMOS camera)__(5.5 mins field)__(2009__AJ___138__758).jpg)
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Click for full-size image (I4329__g' band__(with Gemini-South & GMOS camera)__(5.5 mins field)__attempted isophotes..jpg)
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Last edited by madbadgalaxyman; 18-07-2013 at 05:56 PM.
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Old 21-07-2013, 08:02 AM
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Weltevreden SA (Dana)
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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
Attached Thumbnails
Click for full-size image (IC 4329 & 4329A interacting Eg:Sg w x-ray bridge.gif)
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Old 21-07-2013, 06:09 PM
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Quote:
Originally Posted by Weltevreden SA View Post

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-
The "D" simply refers to an elliptical which has a very extended and extremely-faint envelope around it.
(but real "D" galaxies, however, have outermost halos so faint that they can be invisible in standard imaging. These halos have a tendency to merge eventually with the intracluster light (which is composed of stars that float in between the cluster galaxies)

The old definition of an S0 galaxy is simply that the apparent two-dimensional image of a galaxy (necessarily it is a galaxy with very-smooth light) has two components; the central component which has a fast falloff of surface brightness with increasing radius , and the outer component which has a shallow falloff of surface brightness with increasing radius.
Thus, this traditional definition of an S0 galaxy says nothing at all about what an actual galaxy is, in three dimensions.
In other words, we might assume that the central component is a spheroidal bulge and we might assume that the outer component is a rotationally-flattened & planar disk; but this does not have to be the case.

In the new systems of physical galaxy classification, we focus more on what is actually going on within the three-dimensional 'real' space of each galaxy;
so an S0 Galaxy is today redefined as a galaxy having a bulge component plus a disk component, plus it must also have a Star Formation Rate and a Cold Gas Content intermediate between what we find in elliptical galaxies and what we find in Sa galaxies.
In any galaxy with two apparent components, the radial falloff of surface brightness and the shapes of the isophotes of both the apparent "bulge component" and the apparent "disk component" are amenable to numerical measurement; so by making these measurements we can better assess whether or not a galaxy with two apparent components really does have a genuine disk component and a genuine bulge component.
(Disks and bulges are today very strictly defined in terms of shape, surface brightness falloff, stellar orbits, etc.)

IC 4329 is an "apparent" S0, as are good numbers of galaxies often classified as ellipticals. But whether or not the outer component is a real disk is something that cannot be decided from mere inspection of a two-dimensional image.

Isophotes (= the elliptical lines of equal surface brightness) within an elliptical galaxy can change their shapes in a complex way, with progressively changing (increasing or decreasing) galactocentric radius;
sometimes the isophotal ellipses get a bit pointy, which is often a sign of a low-surface-brightness disk component, while at other times the isophotal ellipses look markedly "blocky" (somewhat rectilinear) which is more likely to be the sign of a slowly-rotating component with little angular momentum and with stellar orbits in many different orientations.

cheers,
The V.Bad Galaxy Man

I have plenty of imaging material about IC 4329 so I may present an analysis of this, at some time.

Last edited by madbadgalaxyman; 21-07-2013 at 10:52 PM.
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Old 24-07-2013, 11:37 AM
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Thanks so much for such an interesting discussion! I am going to have to reread everything a few times to wrap my head around the wonderful information you've provided, Robert and Dana. When the skies permit, I'll go back for another look to compare 4329 and 4329A.

What you say about the distance makes sense to me Robert, as the galaxies do seem to easily observed for nearly 200 mly.
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Old 24-07-2013, 11:53 AM
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Originally Posted by Paddy View Post
Thanks so much for such an interesting discussion! I am going to have to reread everything a few times to wrap my head around the wonderful information you've provided, Robert and Dana. When the skies permit, I'll go back for another look to compare 4329 and 4329A.

What you say about the distance makes sense to me Robert, as the galaxies do seem to easily observed for nearly 200 mly.
Paddy,Robert and Dana, I will try to observe these two galaxies,too see if I can add anything too this very interesting conversation.
Cheers
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Old 26-07-2013, 09:04 AM
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Paddy,Robert and Dana, I will try to observe these two galaxies,too see if I can add anything too this very interesting conversation.
Cheers
Hi there, Mr Ron,

I have moved the technical side of this discussion to the science forum, as I am getting into faint details that only photography can reveal.

What does interest me, is how the centres of IC 4329 and IC 4329A look visually. IC 4329A nucleus should look stellar.

But the centre of IC 4329 may be more amenable to visual observation than photography; I am interested to know how the very centre of this galaxy looks;
- Is it diffuse, how diffuse, and how big would the central feature be?
- does it look like a discrete feature, distinct from the rest of the galaxy?

The surface brightness really spikes, as one approaches the centre of IC 4329, according to some extant surface photometry.

Best Regards,
Robert Lang
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Old 26-07-2013, 09:08 AM
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Originally Posted by Paddy View Post

What you say about the distance makes sense to me Robert, as the galaxies do seem to easily observed for nearly 200 mly.
Indeed, this does seem to be a case where several "heavyweight" astrophysicists have determined the distance to this cluster, indeed there were two recent redeterminations of the distance using the Tully-Fisher method,
yet the results of all this "heavy number crunching" are greatly at odds with the (admittedly subjective) evidence of our own eyes!!!

Best Regards
Roberty
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