Frankfurt Quasar Monitoring

I Zw 1
Object data

  Cross-Identifications  Z0051+12, PHL 3072, MRK 1502, UGC 545, PGC 3151
  1ES 0050+124, RX J0053.5+1241, IRAS 00509+1225
  2MASSi J0053349+124135, NVSS J005334+124133
  1AXG J005334+1241, 2E 0050.9+1225, 0050+124
  2XMM J005334.9+124136, 1WGA J0053.5+1241
  QSO B0050+124, 1 Zw 0051+12, PG 0050+124

  Equat. coordinates   RA  00 53 34.9     DE  +12 41 36     (J2000)
  Constellation   Pisces
  Type (1)   QSO
  Redshift (1)   z=0.061
  Distance (2) (3)   234 Mpc
  Total mag range (mv) (4)   13.89 - 14.51
  Catalog Magnitude (1)   14.03
  Absolute Magnitude (1)   -23.4 MB
  Light Travel-Time (2)   0.744 × 109 yrs
(1) Véron-Cetty & Véron 2006, A&A 455, 776
(2) NASA/IPAC Extragalactic Database
(3) Co-Moving Radial Distanc
(4) Literature

Finding chart


Comparison stars

star  B V
B 14.42 13.72
D 15.02 14.40
E 15.78 14.56
comparison stars from Penston et al. 1971, PASP, 83, 783

Light curve


I Zw 1
This high resolution image shows quasar I Zw 1 and its host galaxy.
Credit: ESO/ST-ECF Science Archive Facility, NASA, Hubble Space Telescope (STScI)

Quasar I Zw 1 is located in the central part of Pisces, about 1.7° NE of 5.5-mag star 58 Psc. The designation I:Zw:1 refers to swiss-born astronomer Fritz Zwicky (Zw) who recognized this object as a compact galaxy ("variable blue spherical, very compact, with a patchy halo“) and listed it in his first catalog in 1964. The spectrum of I Zw 1 was classified a type Seyfert 1, with exceptionally "narrow“ emission lines (NLS1).
Due to its high a
bsolute magnitude of -23.2 MB (given at that time), this compact Seyfert galaxy was classified as a quasar. Considering its high optical luminosity and the small cosmological distance, I:Zw:1 is often claimed "the nearest QSO".
I Zw 1 is a face-on spiral galaxy that harbours an AGN at its centre. The host galaxy has two asymmetric spiral arms, both of which show knots of star formation (see image above). The galaxy disk spans 30 kpc in diameter. Furthermore, I Zw 1 is undergoing a strong phase of starburst in a ring-like area around the centre. From there most of the emitted radiation is produced. As a result, most of the total (near-) nuclear light is emitted in the blue- and ultraviolet-part of the spectrum (PG, PHL, MRK).
Therefore, the most remarkable property of I Zw 1 is the optical emission composite starburst/AGN nature. The starburst/AGN activity is obviously triggered by an interacting fainter companion galaxy close to the west (see image above).
In the POSS-image above, I Zw 1 appears as an extended object with a photographic diameter of 30". The filamentary structure is very obvious and represents the spiral arm pattern of the quasar host galaxy. The point source just north of the galaxy disk is a foreground star.

Visually, observers need at least a telescope of 8- to 10-inch of aperture to detect I Zw 1 as a faint stellar object of about mag 14.0-14.4. Through larger apertures, observers may recognize hints of the quasar host: The stellar appearance increasingly changes and becomes more extended and diffuse, with a star-like nucleus. CCD observers, as well as visual observers, shall use the comparison stars given above. Another photometric sequence was published by Gonzŕlez-Pérez et al. (2001).

The close vicinity around quasar I Zw 1 is void of bright deep sky objects. However, by enlarging the radius to about 10°, observers find some beautiful highlights that shall not be missed.
M 74: Stop down for famous M 74, a bright face-on spiral galaxy, about 11° E of I Zw 1. M 74 is located
in the eastern portions of Pisces. Latest Supernova SN2013ej reached a maximum of about 12.4 mv.
NGC 488: Heading 10° SE from I Zw 1, you find 11-mag galaxy NGC 488, a pretty bright Sb-spiral with
“delicate spiral pattern“.
NGC 470 galaxy group: About 2° S of NGC 488 you reach the NGC 470 galaxy group. The group consists
of at least 3 galaxies and is dominated by NGC 474, a giant elliptical, that shows an interesting shell structure due to interactions with neighbouring NGC 470 (Arp 227).
IC 1613: a large and faint irregular galaxy, which is a member of the local group; located 11° S.

Observers who like to hunt down some more very old quasi-stellar photons may turn to BL Lac object
S2 0109+22
, a variable 15-mag object at a distance of nearly 3×109 light-years, 11° NE of I Zw 1.

Crenshaw, D.M., Kraemer, S.B., Gabel, J.R. 2003, AJ, 126, 1690; The Host Galaxies of Narrow-Line Seyfert 1
     Galaxies: Evidence for bar-driven Fueling.
Halpern, J.P., Oke, J.B. 1987, ApJ, 312, 91; Narrow-Line Seyfert Galaxies with permitted FE II Emission:
     Markarian 507, 5C 3.100 and I ZW 1.
Hansen, T. 1991, Deep Sky Magazine 34, 32; The “Deepest” Deep Sky Objects.
Hutchings, J.B., Crampton, D. 1990, AJ, 99, 37; Images and off-nuclear spectroscopy of QSOs.
Karge, S.; Helle Quasare für 8- bis 10-Zoll Teleskope. Ein Beobachtungsführer zur visuellen Beobachtung von
     Quasaren und BL Lacertae Objekten; Frankfurt 2005.
Osterbrock, D.E. 1977, ApJ, 215, 733; Spectrophotometry of Seyfert 1 galaxies.
Penston, M.J., et al. 1971, PASP, 83, 783; Stars observed photoelectrically near quasars and related objects.
Sargent, W.L.W. 1968, AJ, 73, 893; New observations of compact galaxies.
Sargent, W.L.W. 1970, ApJ, 160, 405; A Spectroscopic Survey of Compact and Peculiar Galaxies.
Schinnerer, E., Eckart, A., Tacconi, L.J. 1998, ApJ, 500, 147; Molecular Gas and Star Formation in the Host
     Galaxy of the QSO I ZW 1.
Schmidt, M., Green, R.F. 1983, ApJ, 269, 352; Quasar evolution derived from the Palomar Bright Quasar
     Survey and other complete quasar surveys.
Steinicke, W. 1998, Interstellarum 14, 24; Im Quasar-Fieber.
Steinicke, W.; Katalog heller Quasare und BL Lacertae Objekte; Umkirch 1998.
Steinicke, W.; Beobachtungsliste für helle Quasare; Umkirch 1999.
Véron-Cetty, M.-P., Véron, P. 2001, A&A 374, 92; A Catalogue of Quasars and Active Nuclei: 10th edition.
Véron-Cetty, M.-P., Véron, P. 2003, A&A 412, 399; A Catalogue of Quasars and Active Nuclei: 11th edition.
Véron-Cetty, M.-P., Véron, P. 2006, A&A 455, 776; A Catalogue of Quasars and Active Nuclei: 12th edition.
Véron-Cetty, M.-P., Véron, P. 2010, A&A 518, 10; A Catalogue of Quasars and Active Nuclei: 13th edition.
Zwicky F., et al. 1960-1968; Catalogue of Galaxies and of Clusters of Galaxies; Vol. 1-6, California Institute
     of Technology.


I Zw 1 (Sasmirala, Univ. of Heidelberg)


© Stefan Karge  /  last obs. 2022-12-24