Markarian 231

[Robin]

Hi everyone,

A few evenings ago I observed UGC 8058 (also known as Markarian 231), a galaxy in Ursa Major. It was easy to find only 1° north of epsilon UMa. With my 20" Dobsonian at 419x it looked very interesting with a bright stellar core and a diffuse, low surface brightness rest of the galaxy. On its northeast side, there was a "bay" that looked fainter than the main part. Please find attached my sketch.

This seems to be a very special galaxy, as some sources claim Markarian 231 is the closest quasar. But other sources claim it is a Seyfert galaxy. It makes me wonder what the exact difference is, because physically quasars and Seyfert galaxies are similar objects.

This paper describes it as a Seyfert galaxy, but also mentions that "Even without allowing for reddening the absolute visual magnitude of the Seyfert galaxy is Mv = -23.0 mag. If Av = 2.1 then M = -25.1 and Markarian 231 would have the optical luminosity of many quasars”:

http://adsabs.harvard.edu/pdf/1977MNRAS.178..451B

While in this article it is called a quasar:
https://astronomynow.com/2015/08/28/...ry-black-hole/

So what exactly is the difference? According to this source “The distinction made in the literature between a quasar and a Seyfert 1 nucleus is largely morphological: in the latter a galactic envelope is seen whereas a quasar is generally star-like, without a nebulosity.”

https://ned.ipac.caltech.edu/level5/...vi/Kem1_5.html

But Brian Cudnik "Faint Objects and How to Observe Them", page 94, cites a table from Wikipedia (in the middle of the article under "Types of active galaxy"):
https://en.wikipedia.org/wiki/Active_galactic_nucleus

So it seems that there is no definite distinction between Seyfert galaxies and quasars. There are many Seyfert galaxies easy to observe with smaller aperture (even Messier objects), but as far as I know other quasars than Markarian 231 can only be seen visually as point sources.

Is my latter statement correct? To those of you who use very large apertures, can you see host galaxies of any other quasars than Markarian 231? Or wouldn't you classify Markarian 231 as a quasar for that reason?


Clear skies,

Robin

Edit: Link was missing.

[Uwe Glahn]

Interesting question Robin. Maybe the astrophysicist here can answer that.

But for real UGC 8058 is a unique object. When I remember right, I had the observing idea from here?
What interest me is the question, if they are similar object out there with a very bright Seyfert nucleus and the faint halo around?

sketch: 27", 419x, Seeing II, NELM 6m5+
UGC8058.jpg

[Jimi Lowrey]

This is also interesting to me. This is a link to Professor Bill Keel page on quasar host galaxies. His web site is full of useful information on AGN’s.

https://pages.astronomy.ua.edu/keel/agn/qsohosts.html

[wvreeven]

According to this page:

https://www.sciencedirect.com/topics...yfert-galaxies

the difference between Seyfert galaxies and QSOs is that the former have an absolute brightness up to B = -23 mag and QSOs are brighter than that. That limit is stated to be "somewhat arbitrary".


Wouter

[Robin]

Hi everyone,

Thank you for your replies! So according to the -23 mag limit UGC 8058 could really be called a quasar.

Wow thank you for the link, Jimi! I started to dig a bit deeper into literature and searched for these objects on Simbad and Cartes du Ciel (including Hyperleda and Gaia catalogs).

Professor Keel's website cites a very interesting paper. Take a look at table 3, where they state magnitudes of the host galaxies obtained by aperture photometry excluding the galactic nuclei:

https://iopscience.iop.org/article/10.1086/303926/pdf

By the way, there seems to be a typo in the figure caption on Prof. Keel's website. The upper right one seems to be PKS 2349-014.

I tried to summarize all this information in a table, which I attached here as a pdf file. Simbad categorizes most of them as Seyfert I galaxies, but there also are BL Lac and QSO objects. The distant and luminous 3C 351 is categorized as Seyfert I. :-)

Their nuclei seem to be within reach for 10"-14" aperture visually. It makes me wonder, if some of these host galaxies are visible for those of you who use 27"-48" aperture?
In some cases the difference between the nuclei magnitude and host galaxy magnitude is relatively small. Markarian 231 definitely is easier than all other galaxies mentioned there. :-)

How about PKS 2349-014 with a 17.1 V mag host galaxy and a not too bright nucleus? It's a BL Lac object, so it ought to be variable.

I was surprised to read about the 17.0 V mag host galaxy of 3C 273. But of course its nucleus is way brighter and supposedly outshines its host galaxy.


Clear skies,

Robin

[Robin]

In the mean time I took another look at literature and databases to find out whether or not there are objects similar to Markarian 231.
Maybe some of you with big scopes might see something similar around quasars that are further away. But probably closer objects are easier?

When Simbad categorizes an object as a quasar, they cite the following paper:
https://www.aanda.org/articles/aa/fu...a14188-10.html


In this paper they define a quasar as follows:
-starlike object or object with starlike nucleus
-with broad emission lines
-that is brighter than absolute magnitude Mblue = -22.25 mag

Wouter mentioned -23 Mblue as a limit. In a previous publication and database the authors used -23 Mblue as limit, but assumed a 50 km/s/Mpc Hubble constant to calculate distances and thus absolute magnitudes.
In the paper cited above, they used 71 km/s/Mpc, which leads to closer distances, but then they adjusted the Magnitude limit accordingly to -22.25.

But they state that there is some uncertainty in the classification, because B magnitudes might not be accurate or objects might be variable.

They also published this database:
http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/518/A10

I took a look at the closest objects from that database using DSS and PanSTARRS (which shows fainter objects of course).

The closest one is 3C 278 = NGC 4782, which fulfills the criteria above. The same with 3C 338 = NGC 6166, an easy to observe elliptical galaxy in the constellation of Hercules. Not quite what someone might imagine when thinking about quasars. But a search for NGC 6166 in Simbad directly leads to 3C 338, which Simbad calls a quasar:
http://simbad.u-strasbg.fr/simbad/si...=SIMBAD+search

But there are some objects, whose magnitude I can't comprehend. In some cases they marked magnitudes as red magnitudes in the database, but blue magnitudes in Hyperleda are way fainter (they might be variable, though):

For example HXMM J110.53+3814 = PGC 33514 (a few arc minutes from the BL Lac object Markarian 421, by the way). 11.3 R mag according to the list (thus -23.5 absolute B mag), but with 15.47 mag from Hyperleda it would actually not qualify. Its host galaxy is bright on DSS, maybe it is observable?

Or NPM1G+41.0135 = PGC 19853, at 9.37 R mag, 14.7 bmag, but that one is almost behind the milky way and may be seriously reddened for that reason, so R magnitude may be more useful when categorizing the object. It has a nice halo on DSS.

I have no idea if any of these host galaxies are visible for amateurs, except for the NGC examples.


Clear skies,

Robin