Date and Time of the Query: 2018-07-22 T13:16:37 PDT
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Notes for object MESSIER 108

15 note(s) found in NED.

1. 2008ApJ...677..926S
Re:NGC 3556
NGC 3556 is an isolated edge-on Scd galaxy (de Vaucouleurs et al. 1976) that is
also optically classified as an H II galaxy. As can be seen in Figure 1, its
optical line ratios are at the extreme low end occupied by H II galaxies, well
to the left of the starburst theoretical-limit line from Kewley et al. (2001).
There is therefore absolutely no hint of the presence of an AGN in this galaxy
in its optical spectrum. Adopting the distance to this galaxy from H97, the
aperture from which the [Ne v] 14.3 micron line was detected corresponds to a
projected size of ~320 x 770 pc. There are some previously published data that
may be consistent with a weak AGN, as well as strong nuclear star formation in
this galaxy. Chandra observations reveal numerous X-ray point sources scattered
around the central regions, with one source coincident with the optical nucleus
that has a power-law X-ray spectrum typical for an AGN (Wang et al. 2003).
Prominent extraplanar diffuse X-ray emission is seen with substructure similar
to that seen in H{alpha} images (Collins et al. 2000) possibly representing
superbubbles of hot gas heated in massive star-forming regions. There are no
published observations of the central stellar velocity dispersion in this

2. 2005A&A...436...75H
Re:NGC 3556
3.3 NGC 3556 (M 108)
NGC 3556 is an edge-on spiral galaxy located at a distance of ~12 Mpc.
Its FIR luminosity, L_FIR_ ~ 10^10^ L_sun_, is similar to that of the
Milky Way. Radio continuum, H I and X-ray data indicate a violent disk
halo interaction, including a prominent radio halo (e.g. de Bruyn &
Hummel 1979), large H I extensions possibly delineating expanding
supershells (King & Irwin 1997), compact radio continuum sources, likely
representing supernova remnants (Irwin et al. 2000), and extraplanar
diffuse X-ray emission (Wang et al. 2003). ^12^CO and HCN observations
(Gao & Solomon 2004) indicate a substantial molecular gas content. No OH
maser was detected (Unger et al. 1986).
With a peak flux density of 20-40 mJy, the H_2_O maser has an isotropic
luminosity of ~1 L_sun_. One or two velocity components are seen. The
profiles are shown in Fig. 5.

3. 2005A&A...436...75H
Re:NGC 3556
4.2.2 NGC 3556
The position of the H_2_O kilomaser in NGC 3556 is not yet accurately
known. From the relative number of nuclear versus non-nuclear masers of
similar luminosity, the most likely interpretation is an association
with a site of massive star formation. In view of NGC 253 and NGC 5194,
however, there is a small chance for a nuclear maser in NGC 3556.

4. 2002AJ....124..675C
Re:UGC 06225
All three nearby NVSS components comprise this extended radio source.

5. 2000ApJ...536..645C
Re:NGC 3556
The continuum image of Figure 4 shows a late-type disk with a fairly
prominent bulge. Prominent dust features are visible along the northern
side of the galaxy. Spiral structure is clearly visible in the disk,
demonstrating that this galaxy is not as edge-on (i = 78^deg^ as
measured by King & Irwin 1997) as the others in our sample.
The H{alpha} image has very little [N II] contamination, as the
throughput of the [N II] lines is low. The relatively low inclination of
the galaxy coupled with the poor flattening make it difficult to detect
a widespread extraplanar layer. A DIG layer extending to z = 1 kpc in a
galaxy inclined greater than 10^deg^ would be almost entirely projected
onto the disk. There is, however, much diffuse emission between H II
regions in the disk. This emission is likely due to a combination of
extraplanar and in-plane DIG. Some of the emission on the eastern side
of the galaxy does appear to be extraplanar. One interesting feature, a
prominent loop of extraplanar gas at R = 3 kpc east of center, extends
about 26" to the south of a cluster of H II regions in the disk. If we
assume this angular distance is entirely in the z-direction, the loop
extends to a height of about z = 1.5 kpc. On the northeast side of the
galaxy, there is much diffuse emission that appears to extend above H II
regions in the disk, parallel to the minor axis. The most prominent
filaments extend from the central region to a height of about
z = 1.5 kpc, assuming the angular extent is entirely in the

6. 2000ApJ...536..645C
Re:NGC 3556
King & Irwin (1997) have performed an H I survey of NGC 3556,
discovering a number of neutral hydrogen shells and extensions.
Observations by BDI93 have detected a radio continuum halo. The H{alpha}
image, both the unsmoothed version and one smoothed to 1.5" resolution,
are shown in Figure 11, with contour overlays of H I column density and
6 cm radio continuum. The beam size of the H I map is 20" x 12", while
the radio continuum map has a 32" x 17" beam size.
As mentioned previously, the low inclination of NGC 3556 makes the
identification of any but the most extended DIG features for comparison
to radio features very difficult. However, the prominent southern
H{alpha} loop at R = 3 kpc east of center is spatially correlated with
an H I spur. It is difficult to tell whether either of these features
are extraplanar or whether they lie in the disk. Though the radio
continuum halo is prominent in this region, the loops do not appear to
be associated with a radio spur. The DIG filaments extending above the
central region of the disk appear to be correlated with a large H I
shell, indicated with an arrow in Figure 11, though the shell is not
identified as expanding by King & Irwin (1997). A spur of radio
continuum emission also appears to be associated with the filaments.
However, there are many H I features and radio continuum spurs that do
not have a DIG counterpart. In addition, the small field of view of our
image does not include the edges of the disk. Thus, we are unable to
find DIG counterparts to the highly energetic features identified by
King & Irwin as the "eastern" and "western" H I supershells.

7. 2000AJ....119.1592I
Re:NGC 3556
NGC 3556 (M108). This galaxy has a complex optical morphology,
similar to NGC 253, with no apparent stellar bulge. Kodaira & Yamshita
(1996) find evidence for a nuclear bar from their NIR photometry and the
galaxy appears to have a very faint H II region nuclear spectrum
(Heckman 1980). A FIR image can be found in Alton et al. (1998).
The large-scale radio continuum emission shows a prominent radio
halo (de Bruyn & Hummel 1979; Condon 1987; Bloemen, Duric, & Irwin 1993;
Paper I). Our high-resolution images reveal a number of components, most
of which form a partial ring. Given the optical complexity of the
nuclear region, the optical nucleus (denoted with an asterisk in Fig. 1)
is most likely displaced from the true nucleus, which we take to be the
H I kinematical center modeled by King & Irwin (1997) and marked with a
cross in the figure. Thus the partial ring likely denotes a ring of star
forming complexes about the nucleus of the galaxy.
NGC 3556 has been mapped in H I by King & Irwin (1997), who find a
number of kiloparsec-scale H I extensions. One extremely large (~7 kpc
diameter) feature, in particular, shows the signature of an expanding
half-shell. It occurs on the eastern major axis about 12 kpc from the
nucleus and extends far beyond the optical disk to the east. Another
smaller partial shell is visible about the same distance from the
nucleus to the west. These authors argue that the symmetry of the shells
and the apparent isolation of the galaxy favor a scenario in which the
shells are internally generated, but they point out that it is difficult
for underlying energy sources to produce the few x 10^56^ ergs that are
apparently required to produce the eastern shell.
The image of NGC 3556 in Figure 1 shows one component about 20"
north of the nucleus, or 1.1 kpc in projection. It is actually a blend
of two components, the fainter secondary visible as an extension to the
southwest. If these components are in the midplane of the galaxy, then
they would be 20"/cos (80) = 115", or 6.5 kpc, from the nucleus, using
the mean inclination of Paper I. Gaussian fitting to the two components
yields, respectively, flux densities of 1.5 +/- 0.1 mJy and
0.58 +/- 0.05 mJy and deconvolved sizes of 1.8" +/- 0.1" x 1.3" +/- 0.1"
at P.A. = 147^deg^ +/- 10^deg^ (101 pc x 73 pc) for the primary and
unresolved for the secondary. The flux densities correspond to radio
luminosities of 2.4 x 10^19^ W Hz^-1^ and 9.3 x 10^18^ W Hz^-1^,
respectively. This northern component is also visible in the VLA
B-configuration FIRST survey image as well as the 6 cm image of
de Bruyn & Hummel (1979). The latter authors indicate that the
feature is coincident with an H II region.

8. 1994CAG1..B...0000S
Re:NGC 3556
Hubble Atlas, p. 35
Dec 6/7, 1937
Imp. Ecl.
60 min
The original Mount Wilson 60-inch plate
used for NGC 3556 here is the same used in the
Hubble Atlas. The description there suggests the
morphological similarity of NGC 3556 and NGC 253.
Several HII-region candidates exist in parts
of the arms not obscured by the dust lanes on the
near side. The largest of these regions may begin
to resolve at about the 2" level. The redshift of
NGC 3556 is v_o = 790 km/s.

9. 1976RC2...C...0000d
Re:NGC 3556
Mem. S.A.Ital., 43, 145, 1971 = Cont. Asiago No. 254
Astr. Ap., 29, 249, 1973.
Rotation Curve (Systemic Velocity):
Astr. Ap., 8, 364, 1970.
IAU Circ. No. 2131, 2134, 1969.
Ast. Tsirk. No. 494, 1969.
Mem. S.A. Ital., 42, 145, 1971 = Cont. Asiago, No. 254.
HI 21cm:
Ap. J., 150, 8, 1967.
Radio Observations:
Astr. Ap., 29, 249, 1973.

10. 1973UGC...C...0000N
Re:UGC 06225
SB(s)cd (de Vaucouleurs), Sc+ (Holmberg)
SN 1969b

11. 1973AISAO...8....3K
Re:KIG 0469
Lumpy condensations in the arms.
Hazy spiral structure.

12. 1964RC1...C...0000d
Re:NGC 3556
Broad, not very bright bar seen end-on. Several complex, partially resolved
arms with many dark lanes on one side. Classification difficult.
See H.A. 105, 230, 1937.
Ap. J., 127, 487, 1958.
Photograph, Rotation and Mass:
Ap. J., 131, 549, 1960.
Ap. J., 135, 697, 1962.

13. 1961Hubbl.B...0000S
Re:NGC 3556
Dec. 6/7, 1937
Imp. Ecl.
60 min
Enlarged 4.0X
NGC 3556 is a member of the NGC 0253 class. It is seen almost
on edge. A negative print, made from the same original,
is shown by de Vaucouleurs in Ap. J., 127, 487, 1958.
Note the lack of a central nuclear bulge. If a large nuclear
region were present it would be visible in this photograph
because the galaxy is nearly on edge. Compare this
illustration with the Sc systems on page 25.

14. 1956AJ.....61...97H
Re:NGC 3556
HMS Note No. 109
Redshift is for approximate center of the system.
H{beta} and H{gamma} present in faint emission.

15. 1918PLicO..13....9C
Re:NGC 3556
Vol. VIII, Plate 26. An irregular, patchy spiral 8' x 1.5' in p.a. 84^deg^;
quite bright. Has a faint nucleus and shows a number of condensations, three of
which are almost stellar; a star of magn. 11 near the nucleus. See Abs. Eff.
35 s.n.

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