Image: Capella Observatory: Josef Pöpsel, Stefan Binnewies; 2006-05-03
R.A. (J2000) = 13h25m27.s6152 (201.o3650633) Decl. (J2000) = -43o01'08."805 (-43o0191125) lII = 309.o5158743 bII = 19.o4173247
1' = 1.1 kpc (at 3.8 Mpc)
z = 0.0006 (H0 = 50 km s-1 Mpc-1; q0 = 0.5)
All-Sky Milky Way panorama (credit: Axel Mellinger)
with the location of Cen A
Historically, Cen A has exhibited greater than an order of magnitude X-ray
(Bond et al. 1996)
with an intensity-independent
spectral shape below about 100 keV. Most measurements, when
fitted with models including a spectral break, show no distinct change of
the spectral index (alpha ~ 1.7 - 1.8)
below the break (i.e. at lower
energies than ~ 100 keV) when the intensity
Baity et al. 1981,
Feigelson et al. 1981,
Morini et al. 1989,
Maisack et al. 1992,
Jourdain et al. 1993).
A very early
detection made during a short rocket flight
(Lampton et al. 1972)
measured a very hard X-ray spectrum with a power-law index of 1.0 .
In gamma-rays, Cen A has been
observed in the past by various instruments and has been found to exhibit
states of high intensity as well (
Bond et al. 1996,
Kinzer et al. 1995,
Steinle et al. 1998).
The detection of a bright X-ray transient close (2'.5) to the nucleus of Cen A in ROSAT images taken in 1995 (Steinle et al. 2000) may shed new light on reported variability if measured with instruments with low spatial resolution.
The inner part of Cen A shows a circumnuclear disk of about
400 pc diameter and a central cavity of about 90 pc. This disk is
emitting in the (sub) millimeter range. Against this emission, a variety
of molecular absorption lines are seen
(Israel et al. 1990).
In addition, evidence for a 40 parsec diameter disk (2.5") of thin ionized gas centered on the nucleus of Centaurus A has been found in the light of PA-alpha using the NICMOS instrument on board HST (Schreier et al. 1998). This disk is not perpendicular to the jet and thus it is not the accretion disk of the black hole.
Narrow emission lines in the (sub) millimeter regime originate in the dust band that crosses the optical picture of Cen A (Eckart et al. 1990). (This dust lane is not to be confused with the circumnuclear dust disk!)
As in the literature often the radio structure elements are used to describe
the position of the features discussed, here is a coarse description of the
large scale features cited from
Alvarez et al. 2000:
Cen A "... is an extended, complex and fairly symmetric source that exhibits two Giant Outer Lobes (GLs), the northern one (GLN) and the southern one (GLS), that span declinations between approximately -38° and -48°.
Closer to the center are two smaller Inner Lobes (ILs), situated to the northeast and southwest of the center, which we will designate as ILNE and ILSW, respectively.
Approximately to the north of the ILNE is the Northern Middle Lobe, which has no symmetric counterpart in the south.
The large feature between approximately -38° and -40° has been called the Northern Loop in the literature (Junkes et al. 1993).
In the nuclear region are the nucleus, the jet, the counter jet and the knots.
Some authors refer to the ILs plus the region closer to the center as the central source or as the central component. Also some authors refer to the GLs as the extended source or simply as the outer lobes.
Good descriptions on Cen A morphology are found in Burns et al. (1983) and in the review by Israel (1998).
Smoothed 4.57 GHz map of the whole radio structure of Cen A from Alvarez et al. 2000 (Fig. 1) with regions indicated.
North is to the top, East to the left of the picture.
The northern lobes and the jet are generally believed to tilted towards the
observer i.e. the nothern part of Cen A is closer to the observer
(Burns et al. (1983),
van Gorkom et al. (1990),
Junkes et al. (1993),
Schreier et al. (1996),
The morphological definitions used in this web pages are as follows:
Details of the inner structures from the review of Israel (1998). (Fig. 3)
multicolor composite including APEX (870 µm) data
ESO press release 2009-01-28
The position of the nucleus, which is hidden in the optical by the dense dust lane, was determined finally using the Hubble Space Telescope (HST) optical WFPC2 image combined with the HST near infrared NICMOS image and the SOFI/NTT image. The derived position is marked on the following three images which show NGC 5128 with increasing resolution (see Marconi et al. 2000 and Kainulainen et al. 2009)).
ESO: VLT - Kueyen
HST: WFPC2 mosaic
SED including all data in the
NASA/IPAC EXTRAGALACTIC DATABASE and recent H.E.S.S. data:
New: the SED data from CGRO are listed in section "CGRO data points" of the page Observations!
SED from contemporaneous data obtained during a campaign in July 1995
(Steinle et al. 1999, Steinle 2001a, Steinle 2001b)
(Note that an error in the ROSAT and EGRET data points has been corrected!)
Name Type Name Type ================= ======= ====================== ====== 1FGL J1325.6-4300 Gamma 1322-427 MCG -07-28-001 G 1322-428 Mills 13-4A 13223-427 MOST 1322-427 1ES 1322-427 XrayS MRC 1322-427 RadioS 1H 1323-428 XrayS MSH 13-4-02 1Jy 1322-428 NGC 5128 G 1Jy 1322-42 NRL 7 1M 1322-427 PGC 046957 G 2A 1322-427 PMN J1325-4302 RadioS 2E 1322.5-4245 PMNM 132221.3-424700 RadioS 2EG J1324-4317 PKS 1322-42 RadioS 3EG J1324-4314 PKS 1322-427 3U 1322-42 PKS 1322-428 4U 1322-42 PKS B1322-428 RadioS ARP 153 G PKS J1325-4303 RadioS AM 1322-424 G PRC C-45 G Bennett 60 RORF 1322-427 Cen A RadioS RX J132524.4-430100 Centaurus A RadioS RX J1325.5-4301 XrayS CTA 59 SGC 132233-4245.4 G Cul 1322-427 RadioS SPB216 Dunlop 482 XRS QSO 3A 2E 3038 EGRET J1326-43 G [PT56] 27 ESO 132233-4245.4 G [VDD93] 184 ESO 270-IG 009 G [VV2000b] J132528.0-430100 ESO-LV 2700090 G [VV98b] J132528.0-430100 GRO J1314-42 [CRA98] 4 H 1322-427 [M98c] 132233.0-424524 ICRF J132527.6-430108 RadioS [KWP81] 1322-42 RadioS IERS B1322-427 RadioS [A94] 35 G IRAS 13225-4245 IrS IRAS F13225-4245 IrS LGG 344:[G93] 002 G
From radial velocity measurements (which give an average of
547 ± 5 km/s) a redshift z of
0.00183 ± 0.00002 is derived, which is often used.
(This would place Cen A at a distance of 12 Mpc!)
This redshift differs significantly from the calculated z value from the distance determined by other means. The discrepancy is due to the proximity of Cen A and the significant superposition of the proper motion of the galaxy within it's group and it's cosmological velocity. (see Graham (1978); NED)
Last update: 2012-04-11 | Copyright © Helmut Steinle, MPE | Impressum