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Notes for object NGC 7793

16 note(s) found in NED.


1. 2011AJ....141...23B
Re:NGC 7793
A.20. NGC 7793
A member of the Sculptor group, NGC 7793 is an Sd spiral
galaxy at D = 3.9 Mpc. A detailed analysis revealed 27 HI
holes distributed almost uniformly across the HI disk with sizes
ranging from 0.19 to 1.05 kpc.

2. 2008MNRAS.385..553D
Re:NGC 7793
NGC 7793: The close-up view of this galaxy displays several H II regions
and the corresponding H{alpha} velocity field exhibits an S-shaped
distortion of the velocities along the minor axis. A kinematical
analysis of the fairly regular H I velocity field reveals a declining
rotation curve (Carignan & Puche 1990). Deep FP observations of the
diffuse gas have shown an extended H{alpha} disc that is detected all
the way to the edge of the H I disc.

3. 2008AJ....136.2648D
Re:NGC 7793
4.17. NGC 7793 is a late-type Sd spiral galaxy in the Sculptor group and was
observed before in H I by Carignan & Puche (1990). In Figure 20 we compare our
rotation curve with their results. The dynamical center and systemic velocity,
as well as P.A., as found by Carignan & Puche (1990) agree with ours within the
uncertainties. The behavior of the inclination is subtly different: whereas the
Carignan & Puche (1990) analysis indicates a rising inclination in the outer
parts, we find a (better defined) gradual decrease there. The resulting rotation
curves on the whole agree reasonably well with each other, but differ in small
but important respects. The most important one is the more gradual decline of
our rotation curve in the outer parts. Even though Carignan & Puche (1990) note
that this is "one of the very few cases with a truly declining rotation curve"
(their emphasis), we argue that any drop in rotation velocity is much less
extreme, especially as there is some evidence that the inclination might
decrease more strongly in the outer parts than we have assumed (see the
description of NGC 7793 in the Appendix). Adopting this steeper drop would raise
the rotation velocities we find in the outer parts by ~25 km s^-1^. We stress
that these inclination values are uncertain, and determined by only a small
number of pixels, but they seem to suggest that a declining rotation curve
cannot be unambiguously established.

4. 2008AJ....136.2648D
Re:NGC 7793
6.15. NGC 7793 The surface brightness profiles of NGC 7793 are shown in Figure
54. The 2MASS J, H, and K profiles can be traced out to ~325"; the 3.6 {mu}m
profile can be traced out to 400"-the entire extent of the H i disk. The 2MASS
profiles show a clear and sudden increase in surface brightness in the very
inner part. This is the signature of the nuclear star cluster in NGC 7793 (Boker
et al. 2002). Its photometric and dynamical importance has already become
negligible at the radius of the innermost point of the rotation curve. The
extent of the IRAC 3.6 {mu}m profile equals that of the H i data, and no
exponential extrapolations were necessary. The (J - K) profile shows a small but
consistent color gradient, translating in a gradient in {GAMMA}^3.6^_*_ from
~0.5 in the inner parts, to ~0.25 at the outermost radius where the 2MASS colors
were deemed reliable. Beyond this radius, we assume a constant {GAMMA}^3.6^_*_ =
0.25 as indicated in Figure 54. The rotation curve mass models are presented in
Figure 55. For the fixed {GAMMA}^3.6^_*_ model both ISO and NFW models give
roughly equal results: neither is fully able to describe the observed rotation
curve (independent of IMF). The "bump" in the rotation curve within R = 2 kpc
and its resemblance with the shape of the stellar disk rotation curve suggest
that the inner part of NGC 7793 could be close to a maximum disk. The ISO model
with {GAMMA}^3.6^_*_ as a free parameter does indeed prefer {GAMMA}^3.6^_*_
values that are slightly higher than the fixed {GAMMA}^3.6^_*_ diet Salpeter
value. For the NFW model, releasing {GAMMA}^3.6^_*_ has forced its value down to
unrealistic values in order to accommodate the more concentrated dark halo. As
remarked earlier (in Section 4.17), the possible observed decline in the outer
rotation curve is uncertain. We tested whether this decline could cause the low
quality of the fits by repeating the analysis with radii R > 4.7 kpc excluded.
This analysis is shown in Figure 56. For the fixed {GAMMA}^3.6^_*_ case the
situation does not change much. The biggest improvement is achieved for the ISO
model with a free {GAMMA}^3.6^_*_. The preferred value is close to a maximum
disk, with a significantly better overall fit.

5. 2007MNRAS.382.1552L
Re:NGC 7793
NGC 7793: This low-luminosity galaxy contains a nuclear stellar cluster (Boker
et al. 2002). Optical nuclear spectra show the presence of a weak nuclear
starburst (Diaz et al. 1982; Walcher et al. 2006).

6. 1994CAG1..B...0000S
Re:NGC 7793
South Polar Group
Sd(s)IV
CD-510-S
Sep 28/29, 1978
103aO + GG385
45 min
NGC 7793 is highly resolved into individual
stars beginning at about B = 18. A spiral pattern
can be discerned, but it is more disorganized
than in M33 or NGC 300, which are earlier
examples of the same type of massive-armed
spiral features.
Associations of early-type stars are evident
in the arms, similar to those in M33 and NGC 300.
The brightest stars may resolve starting
about 0.5 mag fainter than the brightest stars in
NGC 55, NGC 247, and NGC 300, also in the
South Polar Group. From the characteristics of
the Group set out in Table 2 in the introduction
to the RSA2, NGC 7793 and NGC 253 are said
to be more distant than NGC 55, NGC 247, and
NGC 300. The redshift of NGC 7793 is v_o = 241 km/s.
The v_o redshifts of NGC 55, NGC 247,
NGC 253, and NGC 300 are 115 km/s, 227
km/s, 293 km/s, and 128 km/s, respectively.
The order of the luminosity level of resolution
into stars in these galaxies is the same as the
order of the redshifts, showing the extreme quietness
of the local expansion velocity field and the
extension of the South Polar Group in the line of
sight. The velocity dispersion about an ideal
linear velocity flow is at a level of only a few tens
of km/s in this region immediately beyond the
Local Group. The same conclusion, based on
other data for galaxies extending more than
halfway to the Virgo Cluster, has been discussed
elsewhere (Sandage 1986a).

7. 1994AJ....108.2128C
Re:PGC 073049
PGC 073049 = NGC 7793. (B-V)_T_ = 0.54 +- 0.02, (U-B)_T_ = -0.09 +- 0.02.

8. 1993ApJS...86....5K
Re:NGC 7793
NGC 7793; SA (s) d, H II.
NGC 7793 is a prototype Sd galaxy and the faintest of the five major
members of the Sculptor group. As a typical late-type spiral, it is
dominated by a disk component and has a much less dominant bulge
component. The spectrum of the nucleus of this galaxy is dominated in the
UV by the H II regions (see, for example, Rosa et al. 1984) and in the
optical by relatively early-type and almost solar metallicity stars
(B-A-F mixture; Diaz et al. 1982) coexisting with the older metal-poor
population. The H II regions can be seen in the absorption features in
the UV spectrum and the nebular C III] {lambda}1909.

9. 1985SGC...C...0000C
Re:NGC 7793
Plate 757
Overexposed, resolved, background group south-preceding.
Plate 840
Patchy arms with knots, resolved bright star. Background group with chain
of 6 south-preceding.

10. 1982ESOU..C...0000L
Re:ESO 235515-3252.1
=ESO 349- G 12
numerous emission regions

11. 1976RC2...C...0000d
Re:NGC 7793
Photograph:
J.R.A.S. Canada, 68, 117, 1974.
Photometry:
Atlas Gal. Australis, 1968.
Photometry (I.R.: 1-10.6 microns):
M.N.R.A.S., 164, 155, 1973.
Ap. J. (Letters), 191, L19, 1974.
HII Regions:
"Atlas and Catalogue", Univ. Washington, Seattle, 1966.
Ap. J., 155, 417, 1969.
H{alpha} Interferometry in the Disk:
Astr. Ap., 12, 379, 1971.

12. 1964RC1...C...0000d
Re:NGC 7793
Very small, very bright nucleus (or star?). Many irregular, partially resolved
arms with branches.
Sd classification was originally introduced by H. Shapley for this galaxy.
Helwan 9, Helwan 15 and Lund 7 dimensions are for the bright part only.
Photograph:
P.A.S.P., 53, 16, 1941.
P.N.A.S., 26, 31, 1940.
Photometry:
H.B., 907, 1938.
HII Regions:
Zeit. fur Ap., 50, 168, 1960.

13. 1961AJ.....66..541B
Re:NGC 7793
3. NGC 55 Group
De Vaucouleurs (1959) has argued that NGC 45, 55, 247, 253, 300, and 7793 form a
physical group about 8X 10^5^ pc in diameter. The group is only about 2.5 X
10^6^ pc distant and the galaxies are all spirals. The argument for their
forming a physical group is based on their distribution among the other bright
galaxies in the southern hemisphere. From the radial velocities, de Vaucouleurs
showed that the virial theorem would not be satisfied unless the average masses
of the galaxies were in excess of 10^12^ M_sun_, with a mass-to-light ratio
greater than 500. Thus if the galaxies form a physical group, it must be
expanding, unless there is a large concentration of intergalactic matter.

14. 1959ApJ...130..718D
Re:NGC 7793
NGC 7793
The velocity +190 +/- 50 km/sec is a weighted mean of two discordant
determinations: +292 +/- 200 km/sec measured by Hubble at Mount Wilson from two
low-dispersion plates (~400 A/mm), presumably of the nucleus, and +183 +/- 20
km/sec measured by Mayall at Lick from a low-dispersion spectrogram (~400 A/mm)
of the nucleus and of an emission knot 95" southwest; the latter, showing only a
very faint 3727 emission line, contributes little to the weight of this
determination. If the systematic difference, Mount Wilson - Lick = - 28 km/sec,
is applied (Humason et at. 1956, p. 134), the Lick value is reduced to + 155
km/sec. The adopted mean is admittedly uncertain.
Another factor to be considered in a discussion of radial velocities is the
depth of the group along the line of sight. Since the group is roughly circular
and about 20^deg^ in diameter, the depth is about 0.8 Mpc; if the galaxies are
not physically associated, the expected velocity range for a red shift strictly
proportional to distance is about 100 km/sec, or less than 20 per cent of the
observed range, about 550 km/sec. Another estimate of the expected velocity
range is one-third of the observed mean velocity, or about 50 km/sec, which is
even smaller.

15. 1957HPh....53..275d
Re:NGC 7793
SA(s)d
(Plate 20)
A very small, central nucleus, resembling a globular
cluster, is surrounded by several irregular and
broken spiral arms with very many knots.
Note that the arms still start from the nucleus.
The mean surface brightness decreases steadily from Sa to Sd.
Compare with NGC 1084 (Plate 19), NGC 6643 (Plate 24),
and NGC 0300 (Plate 33).

16. 1956AJ.....61...97H
Re:NGC 7793
HMS Note No. 230
Slit on nucleus and condensation approximately 95 arcsec [south-west],
which shows only a very faint {lambda} 3727.
This spiral has been studied photometrically
by Shapley, H, and Mohr, E (1938, Bull. Astr. Obs. Harv., No. 907, 6).


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