Quasars and Visibility of Their Host Galaxies

[Scott Harrington]

Hi All,

I've recently been trying to find a list of quasars that have their host galaxy also visible. Four that I know of are Mrk 231 in Ursa Major (HST image and 20-inch observation by Christian Busch), Mrk 421 in Ursa Major (14-inch observation by van Wulfen), Mrk 1502 in Pisces, and LEDA 33514 in Ursa Major. At the moment, I've only seen Mrk 1502 with my 16-inch.

This kind of research isn't easy since you tend to run across a lot of images like this (https://esahubble.org/images/opo9416b/). Also what's tricky is weeding out the Seyfert galaxies from the quasars. In Zadorozhna et al (2021), they state that "Historically, galaxies with active nuclei, where the luminosity of the nucleus does not exceed the luminosity of the host galaxy, are called Seyfert galaxies. If the luminosity of the active nucleus is much greater than the luminosity of [the] parent galaxy, such object is called a quasar." So, ones like Mrk 817 in Draco don't technically count even though the host galaxy is visible (20-inch observation by Christian Busch). Still, I'd be interested in a few of them, too. 

Scott

[Akarsh Simha]

Pardon me for an unresearched question: what counts as a quasar? Would a bright stellar Seyfert AGN count? If so check out NGC2681

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[Vishal Kasliwal]

Quasars vs Seyferts is a historical nomenclature thing. The text on AGN by Peterson might be a good starting point for understanding the AGN naming zoo. Also look up the Unified AGN model - Meg Urry's works night be of interest...

Vishal

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[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

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