NGC 5566 .SBR2..-Shows a nuclear spiral in HST F606W. The surface brightness
profile does not resemble a traditional bulge plus disk structure. We do not
include this galaxy in any of the structural plots and publish only the
kinematic profile here. The rotational velocity starts to flatten at 6". The
velocity dispersion profile rises toward the center and peaks at a value of
about 150 km s^-1^. The h_3_ moments are anti-correlated with velocity and reach
values of up to 0.15. The h_4_ moments are small in the central arcseconds but
rise to values of about 0.1 at ~= +/- 5 arcsec.
NGC 5566: Suggested as double-barred by Jungwiert et al. (1997); the orientation
of inner structure would make it an inner disk. However, unsharp masking of
WFPC2 F606W images suggests that the inner elliptical feature is a pair of
spiral arms. Due to the presence of numerous dust lanes, this is an uncertain
classification; high-resolution near-IR images are needed to be certain one way
or the other.
NGC 5566 (SBab, 1"~100 pc, I=79.5^deg^)
In spite of the high inclination of the galaxy, we interpret the profiles in
terms of a double barred structure with the higher maximum in ellipticity (
e_max_^s^=0.56 at a~6") corresponding to the nuclear bar. The large-scale bar
has, due to projection, only a low ellipticity peak (e_max_^p^=0.24 at a~24")
and a short PA dip. We think that the deprojected profiles are not meaningful
- because I~80^deg^ - and show them only as illustration of how weak the
deprojection procedure is for such high inclinations (e.g. note the constancy
of the deprojected ellipticity at a high value near the center).
It is interesting to compare this galaxy with NGC 3166 since both are highly
inclined and their morphology is apparently similar on undeprojected images: at
first sight, both seem to show a double barred structure with the components
roughly perpendicular. Nevertheless, in the light of Sect. 3 and Figs. 1 and 3,
we classify NGC 3166 as having only a large-scale bar while NGC 5566 is claimed
to have two bars. To grasp the difference, note that in the (undeprojected)
ellipticity profile of NGC 3166, there is no local maximum interior to that of
the large bar; rather, the ellipticity monotonically climbs towards the center.
This is characteristic of projection effects: the behaviour is qualitatively
similar to Fig. 1b in which the bar is projected along its minor axis as is the
case of NGC 3166 (in comparison, keep in mind that the profile NGC 3166
reflects also the disk - which adds the change of ellipticity and PA rightwards
from the bar ellipticity maximum - and that the inclinations are different -
which changes the relative height of the peak). On the other hand, NGC 5566
shows two ellipticity peaks (excluding the outer raising slope related to the
disk); ellipticity decreases towards the center. That is why we interpret the
structure as double barred: no projection of a single bar with reasonable
ellipticity profile (monotonically increasing as suggested by face-on single
barred galaxies) can generate a secondary ellipticity peak.
Hubble Atlas, p. 43
March 24/25, 1955
103aD + GG11
NGC 5566 is in a physical triplet with NGC 5569 (Sc, at upper
right in the print here), at 4.2' separation, and NGC 5560 (Sc, lower
right at the border, partly cut off), at 5.0' separation. The
redshifts listed in Huchtmeier and Richter (1989), corrected to the
centroid of the Local Group, are v_o(5566) = 1465 km/s, v_o(5560) =
1610 km/s, and v_o(5569) = 1669 km/s. The near equality of these
redshifts suggests physical association. The projected linear
distances from NGC 5566 are 39 kpc for NGC 5569 and 46 kpc for NGC
5560, at a redshift distance of 32 Mpc.
The center of NGC 5566 has the normal morphology of a late-type
SBa with a bright near-ring of the type described and illustrated on
panels 97-99 and on the final summary page of this section, panel
107. The prototype examples are NGC 1452 (SBa; panels 97, 107), NGC
3783 (SBa; panels 98, 107), and NGC 3081 and IC 5240 (SBa; panel
99). The internal near-ring in NGC 5566 is formed by two nearly
overlapping bright arms, which themselves spring from the ends of the
bar in the (s)-like configuration. This internal morphology is burned
out in the facing print, made with a contrast that shows the arm
structures. Some of the internal morphology is shown in the insert
print in the Hubble Atlas (p. 43), made from the same plate used here.
The outer disk of NGC 5566 appears warped. The dust lane in the
arm that itself may be a tidal plume is prominent; a symmetrical dust
lane exists in the opposite arm but is less prominent, presumably
because of poorer silhouetting against an inadequate background.
= Holm 630a
In Arp 286
NGC 5560 and NGC 5566 at 5.0 arcmin, distorted.
NGC 5566 and NGC 5569 at 4.2 arcmin
See UGC 09172
SB(r)ab (de Vaucouleurs)
UGC 09172 at 5.3, 313
UGC 09176 at 4.1, 46
In Arp's class "double galaxies, infall and attraction"
"Connection not visible" (Arp)
= Holm 630a
Extremely bright nucleus. Smooth bar with (r): 1.4 arcmin x 0.75 arcmin.
Faint, smooth outer arms with a strong dark lane. One very faint extension
towards NGC 5560.
Interacting pair with NGC 5560 at 5.0 arcmin.
Non-interacting pair with NGC 5569 at 4.2 arcmin.
Ap. J. 46, 44, 1917.
Lund 6 dimensions rejected, (r) only.
Lund 9 and Lund 10 dimensions are for the bright part only.
Photograph and Photometry:
B.A.N., 16, 1, 1961.
Ap. J. 127, 487, 1958.
Mar. 24/25, 1955
103aD + GG11
This is the only good example of an SBa(r) galaxy shown
in the atlas. The reproduction is overprinted for the nuclear
regions, to bring out the faint arm pattern and the
two thin dust lanes. The insert shows the complete internal
ring with the broad, rather ill-defined bar that terminates
on the ring. Note that the bar is not along the major
axis of the projected ring.
Details of the bar and the lens, as seen from "along" are inset.
There is an "(r)" structure in the lens which does not show
up on this print.
Note the lane, or layer of obscuring material, splitting
the outer arms.
Very bright oval nucleus; whorls make a faint oval 1.6' x 0.8' in p.a. 30^deg^,
and are considerably fainter at the ends of the major axis. Exceedingly faint
condensations. Moderately bright. 5 s.n.