Named after
Carl K. Seyfert who first described
galaxies of this type in
1943. They are galaxies
with emission lines from gas in their centre
which is not asscociated with
stars.
The nuclei are called
Active Galactic Nuclei due to ths emission, or
AGN for short.
These galaxies have been subdivided into two
classes, type I and type II. Type I have
broad emisison lines while both have narrow emisison
lines. The broad line indicate higher density clouds
with a lot of thermal broadening.
A unified model has been developed which states that
all of these objects are formed by accretion in the centre
of the galxy onto supermassive black holes.
The spectrum we see is a function of our
angle of observation of the object.
Seyferts original list:
Galaxy NGC/IC Type Con RA Dec. Hubble Type m_v Dim Dist
M 77 NGC 1068 Sy 2 Cet 02:42.7 -00:01 Sb 8.9 8.2x7.3 60
Per A NGC 1275 Sy 2 Per 03:19.8 +41:31 Pec 11.9 3.2x2.3 230
NGC 2782 -- Lyn 09:14.1 +40:07 SAB(rs)a p 11.6 3.8x2.9
NGC 3077 -- UMa 10:03.3 +68:44 I0 pec 9.8 5.5x4.1 12
NGC 3227 Sy 1.5 Leo 10:23.5 +19:52 SAB(s)a p 10.3 6.9x5.4
NGC 3516 Sy 1.5 UMa 11:06.8 +72:34 (R)SB(s)0: 11.7 2.1x1.8
NGC 4051 Sy 1.5 UMa 12:03.2 +44:32 SAB(rs)bc 10.2 5.5x4.6
NGC 4151 Sy 1.5 CVn 12:10.5 +39:24 SAB(rs)ab: 10.8 6.4x5.5
M 106 NGC 4258 Sy 1.9 CVn 12:19.0 +47:18 Sbp 8.9 20.0x8.4 25
NGC 5548 Sy 1.5 Boo 14:18.0 +25:08 SA(s)0/a 12.6 1.6x1.4
NGC 6814 Sy 1.5 Aql 19:42.7 -10:19 SAB(s)bc 11.2 3.0x3.0
NGC 7469 Sy 1.2 Peg 23:03.3 +08:52 SAB(rs)a 12.3 1.5x1.0
Some more bright Seyfert galaxies:
NGC 566 Sy 1 Psc 01:29.0 +32:21 S0 13.5 1.5x0.4
NGC 985 Sy 1 Cet 02:34.6 -08:47 Pec 13.5 1.3
NGC 1566 Sy 1 Dor 04:20.0 -54:56 S(s)bc? 9.4 7.1x4.8
NGC 7742 Peg 23:44.3 +10:46 S 11.5 2.0x2.0
Mrk 335 Sy 1 Peg 00:06.3 +20:12 S0/a 13.8 0.3x0.3
Mrk 1155 Sy 2 01:26.2 +33:24 S0 15.0 0.5x0.3
Mrk 3 Sy 2 06:15.6 +71:02 S0: 14.0 1.8x1.6
Mrk 509 Sy 1.2 20:44.2 -10:43 Compact 13.0 0.5
Key:
Galaxy, NGC/IC
Identification of the galaxy with other identification and NGC/IC number
Type
Seyfert type (1, 2); "--" indicates that these are no more classified as Seyfert galaxies
RA, Dec
Right Ascension and Declination (J 2000.0)
Hubble Type
Hubble Type
m_v
Apparent visual brightness in magnitudes
Dim
Apparent dimension in arc minutes
Dist
Distance in million light-years
from -- http://www.seds.org/~spider/spider/ScholarX/seyferts.html
Grzcyrgba says: you might add that Seyferts are spiral galaxies only. The broad line is due to revolution around the black hole. In narrow-line galaxies, the broad line region is probably obscured by dust.