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Notes for object NGC 6946

30 note(s) found in NED.

1. 2011AJ....141...23B
Re:NGC 6946
A.19. NGC 6946
Located at a distance of 5.9 Mpc, NGC 6946 is a large spiral
galaxy seen almost face-on. Previous HI studies by Kamphuis
(1993) and Boomsma (2007) revealed 19 and 121 HI holes,
respectively. We detected 56 holes, a subset of those detected by
Boomsma (2007). There is excellent agreement for holes larger
than 700 pc between our samples but not for smaller ones. This is
due to the strict criteria (Q > 5) we applied on holes whose size
is comparable to the resolution limit. NGC 6946 hosts the largest
hole in our sample (no 58) with a size of 2.1 kpc and energy
requirements in excess of 4 x 10^54^ erg, which corresponds to
~4000 SNe. Most of the holes detected (84%) are type 1, with
two holes (nos. 15 and 16) appearing as a superposition of more
than one holes.

2. 2009ApJ...697.1870E
Re:NGC 6946
NGC 6946 At the region where CO emission was detected, the spiral structure is
not clear, so we were able to measure only seven offsets at r = 1.1-2.4 kpc
(0.7'-1.5'). This small number of data resulted in the large uncertainty of
{OMEGA}_P_, so that we categorized this galaxy as A. The positive slope in the
{OMEGA}-{theta} plot, however, gives the fitted value of t_SF_ = 1.1 +/- 0.8
Myr. This is slightly smaller than that for C galaxies, but still has the same
order of magnitude.
Zimmer et al. (2004) applied the TW method to the IRAM 30 m CO data (Walsh et
al. 2002), and derived {OMEGA}_P_ = 39 +/- 8 km s^-1^ kpc^-1^, consistent with
our mean value of 38 km s^-1^ kpc^-1^. Fathi et al. (2007b) also applied the TW
method using H{alpha} data from Daigle et al. (2006), whose spatial resolution
was higher than that of CO data, and obtained two pattern speeds: {OMEGA}_P_ =
47^+3^_-2_ km s^-1^ kpc^-1^ for the inner structure (r <~ 1') and
{OMEGA}_P_ = 22^+4^_-1_ km s^-1^ kpc^-1^ for the outer structure (r ~> 1').
They also claimed that spatially smoothed H{alpha} data gave a comparable value
to {OMEGA}_P_ from Zimmer et al. (2004). As we measured offsets around the
border of the inner and outer structure, our {OMEGA}_P_, which is in between the
two values, is not inconsistent to their results despite the large uncertainty.
Since the spiral structure is more conspicuous and stronger CO emission is
detected in the outer regions (Walsh et al. 2002), further CO observations
pointed to such regions will give understanding of the property of the spiral
arms and star formation in this galaxy. We anticipate that this galaxy will be
recategorized as C if we can measure a larger number of offsets and thus derive
{OMEGA}_P_ with smaller uncertainty.

3. 2009A&A...503..409H
Re:NGC 6946
The polarized emission is strongly detected from the northeast half of this
galaxy, tapering away toward the southwest. The minimum in polarized intensity
occurs at the PA of the receding major axis (PA = 243^deg^, as tabulated in
Table 1). The polarized fraction (in the northeast) is quite low in the inner
parts at less than 10%, moderate at intermediate radii at about 20-30%, and very
high in the outer parts, reaching up to (and perhaps above) 40-50%. The magnetic
field lines are closely related to the large-scale spiral morphology traced by
massive star formation and dust lanes, running largely parallel to the optical
arms. As has been pointed out by Beck (2007), the peaks in polarized emission
originate in the interarm regions. The Faraday depth distribution shows a very
clear systematic variation with azimuth, and will be discussed in Paper III.
Beck (2007) have recently reported VLA and Effelsberg observations of this
galaxy at 1.4, 2.6, 4.8, 8.5 and 10.6 GHz. They demonstrate that there is
substantial depolarization at 20 cm in the southwest quadrant relative to higher
frequencies. The large-scale features that he discusses are very similar to this
Unfortunately only a single well-resolved double background source is
detected in this field (about 10' southwest of NGC 6946), and this source is
quite asymmetric. The brighter lobe has a well-defined RM of -14 +/- 2 rad
m^-2^. Several other sources in the field are possibly influenced by RM
contributions from the disk of NGC 6946 itself; including the extended
background source at ({alpha} 20:35:19, {delta} +60:02:05) just 2' south of the
NGC 6946 disk that appears to be a barely resolved (30") double with a
well-defined RM of +23 +/- 2 rad m^-2^. As previously noted, the low Galactic
latitude of this field (b = +12^deg^, decreasing to the southeast) enhances the
likelihood of fluctuations in the foreground RM. We suggest that the most likely
value of the foreground affecting NGC 6946 is an RM of +23 +/- 2 rad m^-2^, but
stress that there is a substantial systematic uncertainty in this value. Ehle &
Beck (1993) and Beck (2007) have previously determined a value of ~ +40 rad
m^-2^ in this field, which is consistent with the mean Faraday depth that we
have observed in the disk of NGC 6946 (see Fig. 6). We note that their
foreground RM value is derived using the diffuse emission of NGC 6946 itself,
while our derivation was performed using only background sources in the field.
We postulate that the difference may be due to a non-zero contribution to the
rotation measures in NGC 6946 from a vertical component of the magnetic field in
the halo of that galaxy. We return to this possibility in Paper III.

4. 2008MNRAS.388..500E
Re:UGC 11597
UGC 11597 (NGC 6946). NGC 6946 is a very well studied nearby spiral galaxy. Our
H{alpha} Fabry-Perot observations are in perfect agreement with the H{alpha}
Fabry-Perot data recently published by Daigle et al. (2006a) who had a larger
field-of-view (we miss the outer parts of the optical disc). We find a
kinematical inclination of 40^deg^+/-10^deg^ close to their value (8.4^deg^+/-
3^deg^) and compatible with the photometric value (17^deg^+/- 19^deg^) within
the error bars.

5. 2008AJ....136.2648D
Re:NGC 6946
4.15. NGC 6946 is a late-type spiral which, in terms of H I studies, is better
known for its population of H I structures such as H I holes and high-velocity
gas (e.g., Kamphuis & Sancisi 1993; Boomsma 2007). Its global dynamics have been
relatively little studied. This can be partly attributed to its fairly low
inclination which is at the limit of what is feasible using tilted-ring studies.
The rotation curve of NGC 6946 was determined before by Carignan et al. (1990)
and more recently by Boomsma (2007). A comparison with our curve is made in
Figure 18. Both Carignan et al. (1990) and Boomsma (2007) used a constant value
of i = 38^deg^ in their analyses and these different inclinations, compared with
our average value of 32.6^deg^, explain the offset between the curves. Apart
from this, the only prominent difference is the large rotation velocity Boomsma
(2007) finds for the innermost point of the rotation curve. In our data the
corresponding area of the velocity field is below our 3{sigma} H I column
density level, and we can therefore not comment on the presence of this feature
in our data, though there is a hint of a turn-up in the major axis
position-velocity diagram (see the description of NGC 6946 in the Appendix).

6. 2008AJ....136.2648D
Re:NGC 6946
6.13. NGC 6946 The surface brightness profiles of NGC 6946 are shown in Figure
49. The 2MASS J, H, and K profiles as well as the 3.6 {mu}m profile can all be
traced out to ~360". The profiles show clear evidence for a compact central
component. We modeled this component as an exponential disk with parameters
{mu}_0_ = 12.8 mag arcsec^-2^ and h = 0.15 kpc. For the outer disk we used the
observed profile with the inner component subtracted. For larger radii we
extended the profile with an exponential fit with parameters {mu}_0_ = 16.3 mag
arcsec^-2^ and h = 2.97 kpc. There is evidence for a slight excess of light in
the "shoulder" of the profile at R ~ 50". This small excess does, however, have
negligible effect on the results of the rotation curve fit, and we therefore use
a two-component model for the stellar disk. The outer disk of NGC 6946 shows no
strong evidence for a (J - K) color gradient and we use a constant
{GAMMA}^3.6^_*_ = 0.64. Within R ~ 30", the change in color is, however, very
pronounced, resulting in very red central components [(J - K)>1.4 at the
innermost point]. Taking these colors at face value would imply {GAMMA}^3.6^_*_
> 2.0. Such colors are only found for extreme star formation histories (see Oh
et al. 2008), and it is therefore likely that other effects contribute to this
extreme color. For the purposes of the rotation curve analysis we therefore
assume {GAMMA}^3.6^_*_ = 1.0 for the inner disk (which is also the value one
gets when averaging over the entire radial extent of the stellar component). The
halo model fits are presented in Figure 50. They show that the inner disk
component prefers a value for {GAMMA}^3.6^_*_ that is lower than the (J - K)
color would suggest. The values derived for the outer disk are reasonably close
to the predicted values. The NFW and ISO models all produce very similar quality

7. 2007MNRAS.382.1552L
Re:NGC 6946
NGC 6946: Fig. 2 shows a bright central nucleus. The central regions are
affected by dust extinction (Elmegreen et al. 1998). There is radio emission
coincident with the nucleus (Turner & Ho 1983). Strong emission lines can be
appreciated in the nuclear spectrum. The steep red continuum and the large
Balmer decrement denotes the strong extinction that affects the region. Despite
the large [N II] {lambda}{lambda}6548,6584/H{alpha} ratio, the observed strength
of the [S II] lines is not enough to imply a significant contribution from SNRs.
The weak oxygen emission lines but large [S II]/H{alpha} and [N II]/H{alpha}
line ratios imply high metallicities. The non-detection of the [O II] {lambda}
3727 line prevents an estimation of the abundances.

8. 2006MNRAS.366.1265B
Re:NGC 6946
According to H I studies (Carignan et al. 1990), the H I distribution is not
symmetric but is more extended to the north-eastern side. This feature is also
seen in the H{alpha} emission map. The overall H{alpha} velocity map is regular
but shows some non-circular motions near the centre, confirmed by the PV
diagram. It has been recently observed in FP by Blais-Ouellette et al. (2004)
leading to the same conclusions. Once again, the wide field of FaNTOmM and its
high sensitivity are clearly an advantage to obtain better H{alpha} velocity
fields. CO data have been gathered by Young et al. (1995).

9. 2005MNRAS.360.1201H
Re:NGC 6946
NGC 6946. According to H I studies (Carignan et al. 1990), the H I distribution
is not symmetric but is more extended to the north-east side. This feature is
also seen in the H{alpha} emission map. The overall H{alpha} velocity map is
regular but shows some non-circular motions near the centre, confirmed by the PV
diagram. It has been recently observed in FP by Blais-Ouellette et al. (2004)
leading to the same conclusions. Once again, the wide field of FaNTOmM and its
high sensitivity is clearly an advantage to obtain better H{alpha} velocity

10. 2005ApJS..157...59L
Re:NGC 6946
NGC 6946 is a Scd spiral at a distance of 5.5 Mpc with recent star formation
throughout the spiral arm structure and a mild starburst at the center.
ULX1 (IXO 85) and ULX2 are on knotty spiral arms. ULX1 showed a steady
luminosity decrease from 1.8 * 10^39^ to below 0.7 * 10^39^ ergs s^-1^ in
800 days. ULX3 is on the edge of a spiral arm and coincident with a
cocoon shaped supernova remnant (Dunne et al. 2001). Its extreme
luminosity L_X_ = 11 * 10^39^ ergs s^-1^ either comes from the colliding
SNR or from accretion onto a newborn black hole (Roberts & Colbert 2003).

11. 2004A&A...419..501F
Re:NGC 6946
NGC 6946 - We combined the Br{gamma} flux of Puxley et al. (1988) with
the H{alpha} flux integrated in the same aperture from an H{alpha} +
[N II] map. Keel (1984) gives [N II]{lambda} 6583 {Angstrom}/(H{alpha}
+ [N II] {lambda}6583 {Angstrom}) {approx}0.37 in the central 8.1". We
assumed the same ratio throughout our larger aperture to calibrate the
H{alpha} + [N II] map. The nucleus is saturated in the ISOCAM LW2 and
LW3 maps, more severely for LW2. As for NGC 5236, we used maps simulated
from the CVF spectral cube, and we estimate that the missing flux
fractions due to saturation are 27% and 13%, respectively.

12. 2003ApJS..146..353M
Re:NGC 6946
NGC 6946 (C)
There is a great deal of dust in the circumnuclear region of this
spiral galaxy, yet no spiral pattern. This galaxy is one of the
prototypes of the chaotic class.

13. 2002AJ....124.2581S
Re:NGC 6946
NGC 6946 (Fig. 5): The stellar bar in NGC 6946 is
oriented at a P.A. of 19^deg^. In the bar the molecular
gas is distributed asymmetrically about the center. To
the north of the circumnuclear region the CO emission
covers a rather broad 40" x 40" area, with a sharp ridge
of CO emission on the leading side of the bar with a
P.A. of ~0^deg^. In the southern half of the bar the
broadly distributed CO emission is truncated to the south,
extending only 20" south of the circumnuclear area. While
the CO and H emission overlap considerably, the brightest
H{alpha} emission tends to be on the leading edge of the CO.
In the northern half of the bar a ridge of CO emission
extending from the circumnuclear region toward C1 gradually
decreases in intensity. Along this ridge there is an H II
region 10" north of the nucleus, labeled "H1," a CO peak
10" farther north, labeled "C1," and two H{alpha} peaks,
labeled "H2" and "H3," even farther north of C1. We find a
significant amount of CO emission on the trailing side of
this bar. There is a concentration of CO emission,
labeled "C2," curving east from C1. An H II region is
coincident with it. On the trailing side of the bar there
is CO emission C3, C4, and C5 and H{alpha} peaks at H4 and
In the southern half a ridge of CO emission extends
from the nuclear region toward C7. Associated with C7 is
the brightest H{alpha} emission in this half of the bar.
Farther south of C7 the CO emission narrows into a ridge,
labeled "C9," and then ends in a broader peak at C10. On
the trailing side of C9 is an H II region, labeled "H8."
Two H II regions, H9 and H10, are seen in the leading side
of the bar, a few arcseconds northeast of C10. There is
also a trailing extension of CO emission to the east of
H7, labeled "C8."

14. 2002AJ....124..675C
Re:UGC 11597
Huge radio source; flux from (Condon 1987).

15. 2001ApJS..137..139S
Re:NGC 6946
NGC 6946. - Pierce (1994) gives a Tully-Fisher distance of 5.5 Mpc.
Schmidt et al. (1994) give an SN II expanding photosphere distance of
5.7 Mpc. Schoniger & Sofue (1994) give a CO Tully-Fisher distance of
5.4 Mpc. We adopt 5.5 Mpc.

16. 2000MNRAS.319...17L
Re:NGC 6946
NGC 6946: Einstein IPC observations showed X-ray emission associated with
the whole body of this galaxy. Two peaks of emission were detected, one
coincident with its starburst nucleus, and the other associated with a
prominent northern spiral arm (Fabbiano & Trinchieri 1987). The spectral
fit to these data was consistent with a soft and a hard component, probably
associated with diffuse emission and individual accreting sources
respectively. The presence of diffuse emission across the disc of the
galaxy was confirmed by ROSAT PSPC observations (Schlegel 1994b), and can
also be appreciated in our HRI image (Fig. 29). The PSPC also resolved the
nucleus into three sources, which correspond to X3, X4 and X7 in the HRI
data. Fig. 39 shows the profile of the nuclear source X3 and of an
off-nuclear source (X7). Comparing both plots, it is clear that the nuclear
source is extended up to ~20 arcsec away from the central peak. From the
analysis of ASCA and PSPC data, Ptak et al. (1999) found that a composite
spectrum (a Raymond-Smith plasma with kT ~ 1 keV, plus a power law with
photon index {GAMMA} ~ 2.5) was a good fit to the observations. It
should be remembered, however, that due to the poor spatial resolution of
ASCA most of the sources seen in Fig. 29 were probably contained in the
extraction apertures of the X-ray spectra.
Six historic supernovae have been seen in this spiral galaxy (SNs 1917A,
1939C, 1948B, 1968D, 1969P and 1980K) (Barbon, Capellaro & Turatto 1989).
A total of 27 remnants (not including the historic supernovae) have been
detected by Matonick & Fesen (1997). SN 1980K has been observed in X-rays
(Schlegel 1994a), but the source lies outside the ~6 x 6 arcmin^2^ JKT
optical image of the galaxy. The extreme northern source seen in this
galaxy (X8 in Fig. 29) seems to belong to an extreme group of SNRs with
>~ 10^39^ erg s^-1^ (Schlegel 1994c). A faint, red (R = 18.81;
B - V = 1.43) counterpart is seen at the position of this source in our
optical images, which also corresponds to the object No. 16 in the
Matonick & Fesen (1997)'s list of SNRs. Recent PC2 HST images show that
the optical source has an intricate morphology, with a small bright shell
and what seem to be two outer loops or arcs, as can be seen in the narrow
filter image (F673N) shown in Fig. 40. Based on this morphology, Blair,
Fesen & Schlegel (1997) suggested that the source could be explained as
two interacting remnants of different age, with the smaller shell being a
young remnant colliding with the outer, older shells. However, Chu, Chen
& Shih-Ping (2000) have found no high-velocity components in their optical
high-dispersion spectra of the source, which is not consistent with the
presence of a very young and compact SNR. From the H{alpha} flux they
derived a kinetic energy of ~7 x 10^50^ erg for the shocked gas.
Although this value is somewhat larger than what is normally assumed for
supernova explosions, it is still within the range of normal events.

17. 2000AstL...26..285C
Re:NGC 6946
NGC 6946. The rows are rather blurred, especially in the galaxy's
outer regions.

18. 2000ApJ...534..670T
Re:NGC 6946
NGC 6946.-The SMD profile for this galaxy has been calculated with the
highest accuracy among the 11 galaxies of the present sample (FWHM of
110 pc). The M/L in the disk region is flat from r = 1 to 3 kpc, and
then it increases slowly by 2.8 times from r = 3 to 10 kpc. In the
compact bulge region, it shows a remarkable increase toward the center
by about an order of magnitude from r = 1 kpc to 50 pc.

19. 1999ApJS..124..403S
Re:NGC 6946
5.20. NGC 6946
The maps are made from the combination of the data used in
Ishizuki et al. (1990b) and additional data obtained in more sparse
array configurations. The very strong condensation of CO emission at
the nucleus and the barlike gas distribution have been also seen in
Ball et al. (1985) and Regan & Vogel (1995). It has been controversial
whether the gas structure is due to a bar (Ball et al. 1985; Ishizuki
et al. 1990b) or due to open spiral arms (Regan & Vogel 1995), though
the oval distortion of the stellar distribution in the central
kiloparsecs is established from near-IR observations.

20. 1999ApJ...519...89C
Re:NGC 6946
NGC 6946.-This is a face-on spiral galaxy that has an H II region
nucleus (HFS95). We find several compact X-ray sources associated with
NGC 6946, the closest one to the nucleus being coincident (offset < 10")
with the galaxy nucleus.

21. 1999A&AS..138..253B
Re:NGC 6946
NGC 6946/field A+field B - SNe 1917A, 1939C, 1948B, 1968D, 1969P,
1980K: at the sites of SNe 1948B, 1968D and 1980K some patches are
located: they all are bright and quite blue. SN 1980K is likely the
most interesting of all SNe in this galaxy; in fact from all the data
collected at radio wavelengths over a long period of time (Weiler et al.
1986, 1991) and from the fact that its optical counterpart has also been
identified, it appears a good candidate to look at because of dense
circumstellar and interstellar environments. At the sites of SNe 1917A
and 1969P bright blue patches are observed. Star-like objects appear in
the environment. In the case of SN 1939C some objects are visible as
well. SNe 1917A, 1969P and 1980K are classified as candidates
(see Table 3).

22. 1998A&A...335..807A
Re:NGC 6946
This is an Sc galaxy viewed at an inclination of about 31^deg^. There is
recent star formation throughout the spiral arm structure and a mild
starburst at the centre (Tacconi & Young 1990). Our IRAS HiRes data,
before convolution to the ISO 200 micron resolution, appear to follow
the spiral arms quite closely with maxima at the nucleus and prominent
HII regions. The 200 micron map in Fig. 1 exhibits a similar morphology
to the 100 micron data.

23. 1996ApJS..103...81C
Re:NGC 6946
NGC 6946.--WSRT 49 and 21 continuum maps in Boulanger & Viallefond (1992). VLA
D-configuration polarization maps in Beck (1991). Bonn 100-m telescope
polarization map at 4.75 GHz in Harnett, Beck, & Buczilowski (1989).

24. 1996ApJ...458..120S
Re:NGC 6946
NGC 6946
This is a nearly face-on galaxy at a 5.5 Mpc distance and has been observed in
high resolution in the CO line (Sofue et al. 1988; Ishizuki et al. 1990b;
Casoli et al. 1990). Ishizuki et al. (l990b) have obtained a CO PV diagram
using the NMA at a resolution of 4", which showed a very steep rise of the
rotation velocity up to a sharp maximum at 220-230 km s^-1^ within the central
2"(53 pe). An inner rotation curve obtained from this PV diagram is shown in
Figure 10a-1. Sofue et a]. (1988) have obtained a wide-area rotation curve by
combining CO data from the NRO 45 m observations with an H I rotation curve by
Tacconi & Young (1986). They have shown that the rotation is almost perfectly
flat from the very center to the outskirts at R ~ 15 kpc. Casoli et al. (1990)
have combined the CO PV diagram from IRAM 30 m observations with an H I PV
diagram, showing that the rotation is almost flat toward the center. We used
this PV diagram to obtain the CO rotation curve shown in Figure 10a-2.
We have combined all these rotation curves in Figures 10a-1 and 10a-2, and
obtained a rotation curve as show in Figures 10a-3 and 10b. Here we have
corrected for the inclination of i = 30^deg^. The steep rising near the
nucleus is followed by a decrease to a dip at ~ 1 kpc, followed by a flat
minimum at 185 km s^-1^ until 3 kpc. Then the rotation velocity gradually
increases to attain 220 km s^-1^ at R ~ 7 kpc, beyond which the rotation is
nearly flat. The flat rotation appears to continue until the observed edge of
the galaxy at R ~ 16 kpc. The rotation curve mimics the one for our Galaxy, as
shown in the next subsection.

25. 1994CAG1..B...0000S
Re:NGC 6946
Aug 6/7, 1961
103aE + RG2
120 min
NGC 6946 is among the closest galaxies to
the Local Group as judged by the large angular
extent (D_25_ = 18'), the moderately easy resolution
into brightest stars beginning at about B = 21,
and the large angular size of the several
largest HII regions at a core + halo diameter of
10". The resolution into stars is not as easy as in
M101, whose distance modulus is 29.3, or in
members of the NGC 4395/NGC 4214 Group at
m - M of about 28.5, but the Galactic latitude of
NGC 6946 is low at b = 12^deg^, opening the
possibility of appreciable Galactic absorption.
Note that the plate used here is red sensitive,
favoring the detection of HII regions rather
than individual brightest blue stars.
The redshift of NGC 6946 is low at v_o = 336

26. 1976RC2...C...0000d
Re:NGC 6946
= 4C 059.31.1
P.A.S.P., 79, 29, 1967.
IAU Symp. No. 38, pp. 29-87, 1970.
P.A.S.P., 78, 395, 1966.
P.A.S.P., 79, 29, 1967.
Astrofizika, 2, 431, 1966.
Ap. J., 154, 845, 1968.
Ap. J., 194, 559, 1974.
Astr. Ap., 12, 379, 1971.
Publ. U.S. Naval Obs., XX, Part IV, 1971.
Astrofizika, 2, 431, 1966.
Astrofizica, 6, 177, 1970.
Publ. U.S. Naval Obs., XX, Part IV, 1971.
Photometry (5 Color):
A.J., 73, 313, 1968.
Photometry (I.R. 10-21 microns):
Ap. J. (Letters), 176, L95, 1972.
HII Regions:
"Atlas and Catalogue", Univ. Washington, Seattle, 1966.
Ap. J., 155, 417, 1969.
Ap. J., m194, 559, 1974.
Distance Modulus:
Ap. J., 194, 559, 1974.
H{alpha} Interferometry:
Astr. Ap., 12, 379, 1971.
P.A.S.P., 29, 180, 213, 1917.
Harvard Bull., 641, 1917.
IAU Circ. No. 793, 1939,
Ap. J., 96, 28, 1942.
Ann. Rev. Ast. Ap., Vol. 2, 248, 1964.
IAU Circ. No. 1172, 1948.
P.A.S.P., 65, 242, 1953.
"Supernovae & SN Remnants", Ap. & Space Sc. Lib., 45, 204, 1974.
IAU Circ. No. 2057, 1968.
IAU Circ. No. 2072, 1968.
Ast. Tsirk. No. 456, 1968.
SN1969? (Not confirmed)
IAU Circ. No. 2305, 1971.
Inf. Bull.Var. Stars No. 515, 1971.
HI 21cm:
Ap. J., 150, 8, 1967.
Ap. J., 154, 845, 1968.
Ap. J., 176, 315, 1972.
A.J., 73, S95, 1968.
Astr. Ap., 22, 111, 1973.
Sources R (A.J., 69, 490, 1964) and R2 (Astr. Ap., 3, 292, 1969) discordant,
Radio Observations:
A.J., 73, 876, 1968.
Sov. A.J., 13, 881, 1970.
Ap. J., 176, 315, 1972.
Proc. 1st European Ast. Meeting, Vol. 3, 1, 1974.

27. 1973UGC...C...0000N
Re:UGC 11597
Arp 29
SAB(rs)cd (de Vaucouleurs), Sc- (Holmberg)
SN 1917a, SN 1939c, SN 1948b
"Supernova once observed in tip of thick arm" (Arp)

28. 1964RC1...C...0000d
Re:NGC 6946
Extremely small, bright nucleus. Hexagonal pseudo (r): 2.4 arcmin x 2.2 arcmin.
3 or 4 main, massive, partially resolved arms with many branches. Low
surface brightness.
Possible membership in Local Group is not confirmed.
Mt. Wilson Velocity is for an emission patch 4.1 arcmin north-following the
nucleus: V = +222 km/sec. Lick 1956 velocity for 2 emission patches:
V = +221 km/sec.
P.A.S.P., 60, 266, 1948.
P.A.S.P., 61, 98, 1949.
P.A.S.P., 50, 238, 1938.
Radio Emission:
M.N.R.A.S., 122, 479, 1961.
HI Emission:
Epstein, Harvard Thesis. 1962.
SN 1917
P.A.S.P., 29, 211, 1917.
Ap. J., 88, 294, 1938.
Ap. J., 89, 195, 1938.
SN 1939
Ap. J., 96, 28, 1942.
L'Astronomie, 55, 159, 1941.
SN 1948
P.A.S.P., 60, 266, 1948.
P.A.S.P., 61, 97, 1949.
H.B., 919, 26, 1949.

29. 1956AJ.....61...97H
Re:NGC 6946
HMS Note No. 208
Brightest emission patch 250 arcsec [north-east] of nucleus.
Near location of the third supernova found in this spiral
(Mayall, N.U. 1948, P.A.S.P., 60, 266).
HMS Note No. 209
Fainter emission patch 165 arcsec [south-west] of nucleus.

30. 1918PLicO..13....9C
Re:NGC 6946
Vol. VIII, Plate 62. Faint, open, nearly round spiral 8' in diameter. Bright,
slightly elongated nucleus; many almost stellar condensations in the whorls.
5 s.n.

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