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Above undated message substituted from Template:Dashboard.wikiedu.org assignment by PrimeBOT (talk) 13:22, 16 January 2022 (UTC)
There was a question in the article from At18; I moved it here:
Certainly better here than nowhere, work in progress ... -- looxix 18:58 Apr 18, 2003 (UTC)
Well, since this doesn't seem to have happened, would anyone object to me setting up a radio galaxy page? There is currently a lot of detail about radio galaxies in this article which obscures the basic point, while most other classes of AGN have their own entries. Mhardcastle 20:43, 1 February 2006 (UTC)
Starburst galaxies aren't active galaxies (as the definition at the top of the article shows; they're just normal galaxies with a large amount of star formation).
Starbursts should really have their own entry, but I don't have time to do it now: I've just removed the misleading comments from the active galaxy page, and tidied it up. -- mjh, some time ago
There were a couple of misleading statements about synchrotron radiation and high temperatures in the accretion disc. I think this was probably a confusion between the properties of the accretion disc and the jet that is sometimes seen; the jet is synchrotron radiation and can have a very high brightness temperature (nothing to do with actual temperature -- the temperature of the accretion disc is quite low). -- mjh May 23 2004.
I'm no expert but should "An active galaxy is a galaxy where a significant fraction of the energy output is not emitted by the normal components of a galaxy: stars, dust and interstellar gas." be clarified to a numerical proportion? Or is this impossible. A comparison, to a regular galaxy if possible, might help non-experts like me understand this better. Grox 10:07, 13 Feb 2005 (UTC)
As this stands it not only is factually wrong in several respects but duplicates (or in some cases contradicts) what's already there under `Optical spectra'. I'm tempted to delete the whole lot unless it gets a lot better before I look at this again Mhardcastle 18:54, 24 October 2006 (UTC)
This article lacks a section on Low-Ionization Nuclear Emission-line Region (LINER)-type galaxies, which are supposedly the most common type of active nuclei galaxy. Any interest? Thanks. — RJH (talk) 20:03, 4 December 2006 (UTC)
Once I started editing this, I couldn't stop. Hope readers approve of the results. It could do with some diagrams and some more references in places. I think it's an improvement on the original, though. I'm afraid it still doesn't mention LINERs, but they should have their own article, which should then be linked here. I'm not enough of an expert on LINERs to write one from scratch. Mhardcastle 22:02, 24 December 2006 (UTC)
Is H II nucleus a type of AGN? I notice it in this paper: [http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1997ApJS..112..315H A SEARCH FOR "DWARF" SEYFERT NUCLEI. III. SPECTROSCOPIC PARAMETERS AND PROPERTIES OF THE HOST GALAXIES] These are not covered in the article presently. WilliamKF 01:59, 26 February 2007 (UTC)
The statement in the article about unknown explanations for accretition disc jet properties should be amended. Reva Kay Williams, University of Florida, has provided an explanation for the immense power and features of relativistic jets. She developed a proof of Roger Penrose's mechanism from gravitomagnetism for extracting energy and momentum from rotating Kerr black holes. Her model shows that the Lense-Thirring effect (frame dragging) produced by a spinning black hole can account for the observed high energies and luminosities of quasars and active galactic nuclei; the collimated jets about the polar axis; and asymmetrical jets (relative to the orbital plane). They are inherent properties of Kerr black holes. Those properties can be derived without resorting to magnetohydrodynamics.
I believe some of the above should be considered for incorporation with this article. Tcisco 06:36, 21 April 2007 (UTC)
The stub content of Galaxy AGN classification is a subset of what is contained in `Types of active galaxy'. No content needs to be merged; I just am not too sure about dealing with pages that link to the redundant stub. 139.169.220.12 (talk) 18:41, 8 September 2008 (UTC)
ㅡㅡ —Preceding unsigned comment added by 203.255.190.41 (talk) 03:04, 20 March 2009 (UTC)
Hi,
I'm working on giving a lecture about the AGN-Star Formation Connection and I was hoping to hunt down some nice images, but I started reading part of this article and couldn't stop since I kept stumbling upon inaccuracies. For instance, the statements with regards to LINERs are totally inaccurate. Whoever wrote this needs to clean it up and read Luis Ho's 2008 review on the subject of low-luminosity AGN (LLAGN).
"(LINERs. . . ) As the name suggests, these systems show only weak nuclear emission-line regions, and no other signatures of AGN emission. It is debatable whether all such systems are true AGN (powered by accretion on to a supermassive black hole). If they are, they constitute the lowest-luminosity class of radio-quiet AGN. Some may be radio-quiet analogues of the low-excitation radio galaxies (see below)."
Ok - the first sentence actually gives no information about what a LINER actually is. You should explain which emission lines/emission line ratios are examined in order to classify the nucleus of a galaxy as such. The statement that there are "no other signatures of AGN emission" is totally wrong! LLAGN (including LINERs) are almost never silent in the radio and can be readily detected with sufficiently deep and high resolution observations (the recently upgraded VLA - now called the EVLA - can now reach down to rms noises of 10s of micro-Janskys for continuum observations in relatively short times due to expanded bandwidths, for instance . . . I have GBs of data of LINER detections!). In the X-ray regime, Chandra can pick out the compact, hard X-ray point sources which are also indicative of LLAGN (again, including LINERs). There are also other wavelengths which are promising which I am not an expert in (though I know that Luis Ho explains them thoroughly in his 2008 review) as well as methods such as determining the q-value from the radio-FIR relation or correlating the 5 GHz data, hard X-ray data and dynamical SMBH mass in log space (the fundamental plane of black hole activity). Are LINERs really the lowest-luminosity class of radio-quiet AGN? Where did you read that (unsupported claim - or if you did reference one I would suspect it was never actually read)? Radio-loudness is kind of a fuzzy parameter anyways - some people define it relative to optical luminosity and others chose to define it against X-ray luminosity and still others may use a different point of comparison. You have to define your convention when doing astronomy - even coordinates are not consistent from one observer's project to that of another observer!
Also, you have not considered the intriguing class of LLAGN known as "Transition Objects" - these are galaxies with nuclear optical emission line characteristics intermediate between (star-forming) HII regions and LINERs. And what about Type I versus Type II (you mention the distinction for Seyferts but not LINERs)? And LIERS (low-ionization emission regions that are not coincident with the nucleus)?
The summary table is pretty much useless, there are so many mistakes and things left out (and you have totally unsubstantiated claims in there!). Really - Quasars only have "some" jets (um, no - ask any radio astronomer and they will be sort of horrified)? What does "some" even mean? What fraction? And Seyfert galaxies most certainly can have jets! I have data sitting on my laptop of a very bright, beautiful Seyfert galaxy (NGC 3665) that I have just re-imaged with the EVLA at 1.4 GHz that is JET-DOMINATED in the radio! You have to define an observing regime, and really, if you're thinking optically then you're not getting the most bang for your buck (radio observations are critical for AGN studies).
Also, how can you say that a starburst isn't variable? You didn't state a TIMESCALE. If a starburst has depleted the cold gas in a Gyr, that could be considered "variable" - why not. Yes, timescales are important when you start to talk about variability. Different types of AGN display variability on different timescales (another cute little tip-off to what you're dealing with). Why can't a Seyfert be radio-loud? I'm pretty sure there are radio-lound Seyferts (especially with the definition of radio-loud being so loose). You can't just put "yes" and "no" in columns when you are doing astronomy - everything is a percentage and there are ALWAYS some oddball outliers no matter what the norm is. I suggest completely removing that table since it is only spreading false information.
I would like to eventually help fix up this article and create something accurate from someone in the field with a graduate degree, but I don't have time to delve into the full scope of the subject of AGN at this time (I specialize in LLAGN - so my knowledge of FRI/FRII objects, quasars, blazars, etc. isn't so detailed . . . it was the inaccurate statements about LINERs that caught my eye at first).
I don't know how this got a B rating - this needs to be reclassified as a stub with the "needs attention from an expert" notice at the top. Hopefully I'll have time to fix this up soon.
Kris1284x (talk) 09:52, 2 September 2011 (UTC)
Wouldn't be useful an image like this? I was planning on creating something like that myself, but it won't be fantastic. Does anyone know a good free image? In case not, what should I highlight in the image apart from the obvious (accretion disk and jets)? I was thinking about removing the whole viewing angle story, since it already has its section and image. What do you all think? Heinerj (talk) 22:51, 15 May 2015 (UTC)
The following Wikimedia Commons file used on this page or its Wikidata item has been nominated for deletion:
Participate in the deletion discussion at the nomination page. —Community Tech bot (talk) 03:45, 26 February 2021 (UTC)
This article does not mention the N galaxy, which was a frequently used classification for objects between a Seyfert an a QSO. For example:
This historical term is mentioned in other encyclopedias, so I think it would make sense to cover that here. Praemonitus (talk) 21:40, 25 January 2022 (UTC)
I added a new section "New development" after the publishing in AphJ in 2022, https://iopscience.iop.org/article/10.3847/1538-4365/ac5b64 of a new discovery about SBMH that requires a change in the unified model of AGNs (cf. Padonani and Urry, 1995 and its updates) -- Luxorion
This goes with the discussion at Wikipedia talk:WikiProject Astronomy#Quasar tsunami (red link). Can we add a possible section in here explaining AGN outbursts? There is a lot of discussion about this in astrophysics circles over the last decade, detailing bubbles, gas sloshing, and cavities (reminiscent of Ophiuchus). SkyFlubbler (talk) 19:06, 11 November 2022 (UTC)
The section "Observational characteristics" has no references and is almost exclusively model results. I will replace it with a sourced section. Johnjbarton (talk) 02:41, 10 March 2024 (UTC)
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