Quasars and Visibility of Their Host Galaxies
Scott Harrington
Akarsh Simha
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Vishal Kasliwal
Robin Hegenbarth
Hi Scott et al.,
This is my first mail in this group, so I hope it works right away. :-) Scott, we seem to have very similar observing projects!
Indeed, the definition of a quasar seems to be subjective. Physically, they are very luminous examples of Seyfert galaxies, but the question is where to draw the limit between a quasar and an "ordinary" Seyfert galaxy.
In this catalog there is a list of quasars: https://ui.adsabs.harvard.edu/abs/2010A&A...518A..10V/abstract
They define a quasar as a starlike object or object with a starlike nucleus with broad emission lines that is brighter than -22.25 Mag absolute blue magnitude.
Interestingly, many objects listed in this catalog don't fulfill their magnitude criterion based on Simbad data, although they referenced Simbad data in their catalog.
Within the last couple of years I observed some of those objects. At least I Zw 1 (PGC 3151) and VII Zw 118 = PGC 20174 fulfill their criterion. With my 20" Dobsonian I was able to discern non-stellar galaxy bodies from their stellar cores when observing them.
At Deep Sky Meting in March 2026 in southern Germany I will give
a presentation on this topic. So for readers who will attend
(there certainly are a few...) I will discuss this quasar catalog
and observations I did based on this source.
Clear skies,
Robin
Scott Harrington
Steve Gottlieb
00 53 34.9 +12 41 36; Psc
V = 13.9-14.5; Size 0.5'x0.5'; Surf Br = 12.3
17.5" (9/7/96): at 100x appears as a mag 13.5-14 "star" using a GSC finder chart to identify. At 220x, the completely stellar core is surrounded by a much fainter 15" halo with averted vision. The halo was easier to view at 415x.
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VII Zw 118 = PGC 20174
V = 15.3; Size 0.4'x0.3'
24" (1/4/14): at 260x, appears as a faint mag 15-15.5 "star", though it was difficult to determine if it was quasi-stellar in soft seeing. Easy to identify as it is located 1.4' WSW of mag 9.4 HD 52882 and there are no nearby stars of similar magnitude.
The V mag derived using SDSS photometry is 15.3, but the Veron 2010 catalogue of "Quasars and Active Galactic Nuclei" lists V = 14.6 and B = 15.3 with a classification of Quasar.
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Mrk 421 = UGC 6132 = CGCG 184-050 = QSO 1104+384 = PGC 33452
11 04 27.3 +38 12 32; UMa
V = 12.8; Size 0.8'x0.6'; Surf Br = 11.8
48" (4/23/25): at 610x and 813x; Mrk 421 appeared as an extremely bright 13th magnitude "star" (stellar nucleus) with a small, faint halo. I tried to keep the intense glare of 6th mag 51 UMa outside the field. Mrk 421-5 = PGC 33453, just 14" ENE, appeared fairly faint, small, slightly elongated, ~12" diameter, low surface brightness. UGC 6140, a diffuse edge-on was also visible to the S of a mag 7.5 star, as well as two fainter galaxies, PGC 33475 and LEDA 3765478.
18" (4/10/04): appears as a mag 12.7 "star" at 220x, though this is the core of a compact BL Lac object with a variable active nucleus (z = .03). A small, extremely faint halo was highly suspected at 220x (more secure at 300x) and the nucleus seems slightly softer than similar stars. Located just 2' SSW of 6th mag star 51 UMa and 4' SW of a 7.5 mag star.
18" (5/31/03): at 350x, this compact galaxy appeared at an estimated mag 12.5-13.0 just 2' SSW of naked-eye mag 6.0 51 UMa and 4' SW of a mag 7.5 star! Seeing too soft in breezy conditions to confirm a halo, though it was highly suspected.
17.5" (4/13/96): at 100x, appears as a nearly stellar 13 object situated just 2' SSW of 6th magnitude 51 UMa. In comparison to similar foreground stars, this compact Markarian galaxy has a "soft" appearance with a very small and extremely faint halo. Using a comparison sequence, this variable active nucleus appeared ~mag 13.3.
17.5" (5/22/93): appears as a mag 13.5 stellar object located just 2.1' SSW of 51 Ursa Majoris (V = 6.0) and 4' SW of mag 7.4 SAO 62392! No halo seen at 220x. This extremely compact galaxy has the most variable active galactic nucleus! (V = 12.4-14.0).
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Mrk 231 = UGC 8058 = MCG +10-19-004 = CGCG 293-045 = CGCG 294-004 = A1254+57 = VII Zw 490 = PGC 44117
12 56 14.2 +56 52 25; UMa
V = 13.6; Size 1.3'x1.0'; Surf Br = 13.7; PA = 10°
24" (5/30/16): at 322x; this remarkable object (astrophysically) contains a bright quasi-stellar nucleus (mag ~13.5) surrounded by a small, very low surface brightness halo. The appearance was very unusual as there was no core - just a bare bright nucleus that required a close look to verify it was slightly non-stellar (perhaps 3"-4" diameter). The nucleus was surrounded by a small, dim halo.
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Scott Harrington
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Steve Gottlieb
The complete list of targets — Mrk 421, W Comae Berenices, AP Librae, Mrk 501, 3C 371, BL Lacertae, 3C 66A, and BW Tauri.
If anyone would like a copy of the article, send me a note.
Steve
Scott Harrington
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JayLEads
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owen...@gmail.com
Wolfgang wrote a booklet for the Webb Soc on extra galactic objects discovered as variable stars many years ago.
Alvin Huey
22” at 383, 460, and 639x – This object appears slightly diffused with a stellar center. Diffuse part is about 0.2' across. Fainter than the mag 15.1 star that lies 0.9’ south and about the same as the mag 15.8 star.
22” at 306 and 383x – NGC 7720 is a bright, round glow with a much brighter center. Very high surface brightness for a galaxy. 0.5’ across. 5 other galaxies are seen on the same 6.6’ field. Starting with the closest, MAC 2338+2702B, is an extremely faint very small, round glow, detected 50% of the time using averted vision (AV). MAC 2338+2701A is a considerably bright 2:1 elongated glow with a slightly brighter round center. PA = 0 and 0.3’ long. IC 5342 is a bright, small round glow with a brighter center. 0.3’ across. IC 5341 and its western neighbor, CGCG 476-90, are equal in brightness and appearance. Both are considerably faint round patches with brighter centers. 0.4’ across.
owen...@gmail.com
After some internal discussions we decided we could release Wolfgangs guide as a free PDF so others could see the work.
Owen
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Alvin H
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owen...@gmail.com
Hopefully we will have the full version with cover up on the web site soon for download.
Alvin H
Uwe Glahn
Interesting topic. I have to visit some more objects from the lists.
Thanks for the .pdf Owen
From the four objects Steve mentioned, I can contribute two sketches:
http://www.deepsky-visuell.de/Zeichnungen/UGC6132_UGC6140.htm
http://www.deepsky-visuell.de/Zeichnungen/UGC8058.htm
uwe
Muriel Dulieu
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Scott Harrington
Steve Gottlieb
Thanks for sharing your notes, Alvin. My research shows that despite how they were first discovered, V395 Her and UX Psc don't show up in any recent works as containing an AGN.
Alvin H
Date: Sunday, March 1, 2026 at 12:03 PM
To: adventures...@googlegroups.com <adventures...@googlegroups.com>
Subject: Re: [ADS] Quasars and Visibility of Their Host Galaxies
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Robin Hegenbarth
Hi everyone,
After my presentation regarding quasar host galaxies at the Deep Sky Meeting 2026 in Germany last weekend, I will summarize my findings in this post as promised back in January. It seems that there is no uniform distinction between Seyfert I galaxies and quasars in scientific literature.
There is the „Catalogue of quasars and active nuclei: 13th edition“ my M.P. Véron-Cetty and P. Veron: https://www.aanda.org/articles/aa/pdf/2010/10/aa14188-10.pdf and
https://cdsarc.cds.unistra.fr/viz-bin/cat/VII/258
In this paper a quasar is defined as follows:
Stellar object or object with stellar nucleus, with broad emission lines, and with a blue luminosity larger than -22.25 Mag.
But there is another definition by E.P. Smith et al., „On the nature of QSO host galaxies“, https://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1986ApJ...306...64S&defaultprint=YES&filetype=.pdf
According to that paper a quasar is an active galactic nucleus with a blue luminosity larger than -22.25 Mag, which is more luminous than the surrounding host galaxy.
So I examined the catalog mentioned above and observed quite a few objects listed there with my 20“ Dobsonian.
Among them were the following objects:
NGC 6166: An elliptical galaxy, whose nucleus appeared mottled and sometimes stellar (20“, 419x). However, the luminosity of its nucleus is only -21.5 blue Mag according to M. Lachièze-Rey et al.:
https://articles.adsabs.harvard.edu/pdf/1985A%26A...150...62L
PGC 100408: Elongated blob with stellar nucleus (20“, 419x). I did not find a paper analyzing this object, but Gaia DR3 lists its nucleus as a 15.8 mag stellar object, yielding -21.5 blue Mag (and this may even include part of the host), thus falling short of the definition above.
PGC 20174 (VII Zw 18): Stellar center with a diffuse hue. Field stars of similar magnitude had a stellar appearance (20“, 419x). This object was listed by Fu-zhen Chen:
https://academic.oup.com/mnras/article/212/4/857/1086083
having -22.0 blue Mag luminosity, falling short of the definition above.
PGC 3151 (I Zw 1): At direct vision, a stellar nucleus was visible. At averted vision, the stellar nucleus was surrounded by a diffuse hue. Field stars of similar magnitude appeared stellar (20“, 419x). The blue luminosity of this galaxy is -22.9 Mag, the blue luminosity of its nucleus -22.5 Mag according to J. Scharwächter et al., thus the AGN is more luminous than its -22.0 blue Mag host galaxy, Thus, the quasar criteria are fulfilled for this object.
https://www.aanda.org/articles/aa/pdf/2003/27/aah4270.pdf
Summarizing, with my 20“ at 419x magnification, according to the definition mentioned above, I Zw 1 was the only quasar whose host galaxy I was able to observe visually. More of such objects may be visible with larger aperture.
Clear skies,
Robin
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