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Notes for object MESSIER 100

38 note(s) found in NED.


1. 2009ApJ...697.1870E
Re:NGC 4321
NGC 4321 (M 100) We measured 34 offsets at r = 1.6-6.6 kpc (0.3'-1.4'), and
found that the offsets in the arm region (r ~ 5-6.5 kpc) are almost zero, while
offsets close to the bar region (r~4.5 kpc) are about 10^deg^, which had
already been found by Sheth et al. (2002). There are several possible reasons
for no offsets found in the arms: (1) material arms, (2) corotation at where
offsets were measured, and (3) elliptical orbits nearly parallel to the spiral
arms. Since there are offsets close to the bar region, where orbits should have
higher ellipticity than in the arm region, (3) seems to be less plausible at
least for this galaxy. Rand & Wallin (2004) derived the pattern speed of this
galaxy to be 28^+4^_-5_ km s^-1^ kpc^-1^ with the TW method applied to the CO
data. With the RC from Sofue et al. (1999), this value locates the CR at about
10 kpc (~2') in radius. Previous studies listed in Table 6 also suggest R_CR_
>~ 2'. These measurements are well beyond where we measured offsets, so
that they cannot explain the lack of offsets.
The northern arm is weaker than the southern arm both in CO and H{alpha}.
This asymmetry is thought to be due to the existence of the companion galaxy NGC
4322, the ram pressure from intragalactic matter in the Virgo cluster, or the
central bar. Knapen et al. (1996) investigated the arm/interarm ratio of the
SFE, and found no symmetric patterns though this ratio was larger than unity for
most part of the two arms. They concluded that this was because their observed
region did not include any resonances, although star formation on arms was
actually enhanced and it might be triggered by spiral density waves. Thus, we
deduce that the spiral density wave might be rather unstable or localized at
least in the region we see, and that (1) would be the most plausible among the
three. If this grand-design galaxy is confirmed to be without density waves, it
will give a new picture of spiral galaxy formation.

2. 2009A&A...503..409H
Re:NGC 4321
NGC 4321 (M100): In this spiral galaxy, polarized emission is clearly detected
throughout most of the disk. In the northwest, bright polarized emission is
present throughout the interarm regions. But in the southeast the polarized
surface brigntess declines dramatically. The lowest brightness of polarized
emission occurs near the receding major axis (PA = 159^deg^, as tabulated in
Table 1). The polarized fraction in this disk is generally rather low, ranging
from less than or about 2% in the inner regions to about 5-10% in the interarm
regions, with the polarized fraction tending to be higher outside of the arm
than inside the arm. At the edges, the polarized fraction is higher at about the
15% level, and localized spots where the fraction reaches 30%. The appearance of
the magnetic field lines is highly ordered, and follows the orientations of the
optical spiral arms. An almost equal double in the field allows consistent
assessment of the Galactic foreground RM of -17 +/- 1 rad m^-2^.

3. 2008ApJS..174..337M
Re:NGC 4321
NGC 4321 (Fig. 5i).-The well-resolved full ring contains 57 detected H II
regions. Because missing data prevent the calculation of H{alpha} equivalent
widths and ages, we refer to Allard et al. (2006) for a similar analysis in
H{beta}. They find a bipolar age gradient corresponding to the ring PA (at
170^deg^ and 350^deg^) and the location of the youngest H II region in each
hemisphere. The age increases in a counterclockwise direction along the
direction of flow in the ring.

4. 2008ApJ...677..926S
Re:NGC 4321
NGC 4321 is an Sbc spiral galaxy (de Vaucouleurs et al. 1976) at a distance of
16.8 Mpc (Tully & Shaya 1984). At this distance, the aperture from which the [Ne
v] 14.3 micron line was detected corresponds to a projected size of ~0.9 x 1.4
kpc. This galaxy is optically classified as a transition object with no broad
lines detected (H97), implying that there is no firm evidence for an AGN based
solely only its optical spectrum. Previously published multiwavelength
observations reveal no signs of AGN activity in this galaxy. There are several
published radio observations displaying extended emission (Filho et al. 2000,
2006), but no evidence for a compact flat spectrum radio core (Nagar et al.
2002). The nucleus is not detected by Chandra, and the upper limit to the 2-10
keV luminosity is L_X_ ~3.6 x 10^38^ ergs s^-1^ (Dudik et al. 2005), implying
that the AGN is either weak or highly absorbed in the X-ray. Mid-infrared
(Wozniak et al. 1998), optical (Pierce 1986), H{alpha} (Knapen et al. 1995), and
CO (Rand 1995) observations display a prominent circumnuclear ring of star
formation activity which is also seen in the IRAC and [Ne II] images (see Fig.
4). However, the emission from the higher ionization potential [Ne III] and [O
IV] lines is clearly centrally concentrated and compact, strongly suggestive of
AGN activity in the nucleus. The central stellar velocity dispersion in this
galaxy is 83 +/- 12 km s^-1^ (Whitmore & Kirshner 1981).

5. 2006MNRAS.366.1265B
Re:NGC 4321
This grand-design spiral galaxy is located in the Virgo cluster. It has been
frequently mapped in the H{alpha} emission line using high-resolution FP
interferometry (Arsenault, Roy & Boulesteix 1990; Cepa & Beckman 1990; Canzian &
Allen 1997; Knapen et al. 2000), in the molecular CO emission line (Canzian
1990; Rand 1995; Sakamoto et al. 1995; Garcia-Burillo et al. 1998; Helfer et al.
2003) and in the 21-cm H I emission line (Cayatte et al. 1990; Knapen et al.
1993). The H I disc is almost totally confined within the optical one but with a
slight lopsidedness towards the south-west (Knapen et al. 1993). The H I, CO and
H{alpha} velocity fields show kinematical disturbances such as streaming motions
along the spiral arms and a central S-shape distortion of the iso-velocity
contours along the bar axis. The circum-nuclear region shows the presence of an
enhanced star formation region as a four-armed H{alpha} ring-like structure and
a CO & H{alpha} spiral-like structure. Much more details can be found in
Hernandez et al. (2005a) and in Chemin et al. (2005).

6. 2006MNRAS.366..812C
Re:NGC 4321
The well-known galaxy NGC 4321 (M100) has often been mapped with FP
interferometry (Arsenault et al. 1990; Knapen et al. 1995; Canzian & Allen 1997;
Hernandez et al. 2005b). Evidence for three different pattern speeds (nuclear
structure, large-scale bar, spiral) has been shown using the Tremaine-Weinberg
method on this rather regular velocity field (Hernandez et al. 2005b), which
also shows signs of streaming motions (Knapen et al. 2000). The core of the
galaxy has a nuclear ring-like structure.

7. 2005MNRAS.360.1201H
Re:NGC 4321
NGC 4321. This grand-design spiral galaxy has been frequently mapped in the
H{alpha} emission line using high-resolution FP interferometry (Arsenault, Roy &
Boulesteix 1990; Cepa & Beckman 1990; Canzian & Allen 1997; Knapen et al.
2000a), in the molecular CO emission line (Canzian 1990; Rand 1995; Sakamoto et
al. 1995; Garcia-Burillo et al. 1998; Helfer et al. 2003) and in the 21-cm H I
emission line (Cayatte et al. 1990; Knapen et al. 1993). The H I disc is almost
totally confined within the optical one but with a slight lopsidedness towards
the south-west (Knapen et al. 1993). The H I, CO and H{alpha} velocity fields
show kinematical disturbances such as streaming motions along the spiral arms
and a central S-shape distortion of the isovelocity contours along the bar axis.
The circumnuclear region (CNR) and shows the presence of an enhanced star
formation region as a four-armed H{alpha} ring-like structure and a CO and
H{alpha} spiral-like structure. Many more details can be found in Hernandez et
al. (2 005).

8. 2005ApJS..160...76B
Re:NGC 4321
Low discordance and good S/N. Clear peak in {sigma}_*_ offset from the
photometric center. Clear regular rotation and a centrally peaked curve of
growth. See Figures 26 and 30a.

9. 2005ApJS..157...59L
Re:NGC 4321
NGC 4321 (M100) is a grand-design Sbc spiral galaxy at a distance of 14.13 Mpc.
ULX1 is identified with SN 1979C. ULX2 is on the tenuous tip of a spiral arm.

10. 2004A&A...415..941E
Re:NGC 4321
NGC 4321 (M 100): Pierce (1986), Shaw et al. (1995), Knapen et al.
(1995a). Outer-bar measurements are from ellipse fits to the 2MASS
K-band image, with L_bar_ from spiral arms crossing the ends of the
bar; inner-bar measurements are from the near-IR ellipse fits in
Perez-Ramirez et al. (2000). Outer-disk inclination and PA are from
the H I kinematics of Knapen et al. (1993); distance is from Cepheids
(Freedman et al. 2001).

11. 2003ApJ...598..827P
Re:NGC 4321
NGC 4321 (M100).-The B-band image of NGC 4321 displays grand spiral arms
embedded in a large disk, with a small inner bulge. The UV images have
low S/Ns. A nuclear point source dominates the UIT/FUV and MUV images,
which is probably due to nucleated star formation, but may result from a
weak AGN (see Roberts, Schurch, & Warwick 2001). Faint UV emission
traces the spiral arms. The internal color dispersion between the
UIT/FUV and UIT/ MUV bands is inconclusive because of the low S/Ns of
the images. NGC 4321 exhibits internal color dispersion between the
UIT/MUV and B-band images. This dispersion appears to result from color
differences between the nuclear region and the stellar populations of
the bulge and disk.

12. 2003AJ....126..742H
Re:NGC 4321
The morphological classification as determined by us is indicated in
parentheses next to the galaxy name, with our "chaotic circumnuclear
dust" (C) category now not including those galaxies with obvious dust
lanes (DL). Where the classification has already been made by Martini
et al. (2003), we indicate this with "-mp."
.
3.26. NGC 4321
Figure 13 (top).
Spectra: Some patchy extended emission lines. These lines do not join
to the line emission at the continuum center. There is strong
continuum on the NUC spectrum.

13. 2002MNRAS.337..808K
Re:NGC 4321
A10 NGC 4321
NGC 4321 (M100) is a late-type barred galaxy with well-defined spiral arms
and a spectacular central region which only reveals some of its hidden
features through the use of the NIR observations. Knapen et al. (1995a,b)
discussed in detail the existence and origin of a stellar bar with a
large-scale and a small-scale component, a two-armed star-forming spiral in
the CNR, and a pair of leading arms inside the nuclear ring-like region. We
have used the same optical images as used by Knapen & Beckman (1996) and
refer the reader to that paper for a detailed discussion. In summary, the
B-I colour index map shows a pair of curved dust lanes in the bar
continuing into the disc spiral arms. A string of HII regions accompanies
the dust lanes in the bar. There is abundant H{alpha} emission from the CNR
and the disc of this galaxy. Knapen (1998) catalogued almost 2000
individual HII region s from the image shown here and presents a
statistical analysis of their properties, but also discusses the H{alpha}
morphology. Knapen & Beckman (1996) presented surface brightness profiles
for, among other tracers, B, I, B-I and H{alpha}. Although the profiles in
the present paper were determined using a different ellipse fitting
algorithm, we confirm the main characteristics of the surface brightness
and colour profiles. The ellipticity and PA profiles confirm the two parts
of the bar (Fig. 1j).
As discussed in detail in the literature (e.g. Knapen et al. 1995a,b,
2000b), images of the CNR of NGC 4321 (Fig. 2j) show good coincidence
between the features highlighted by the J-K colour map and the H{alpha}
contours. We can see clearly the SF clumps along the arms of the miniature
spiral structure (including the characteristic K1 and K2 points - red loci
accompanied by massive SF toward the SE and NW of the nucleus).

14. 2002AJ....124.2581S
Re:NGC 4321
NGC 4321 (Fig. 3): The bar in NGC 4321 is oriented at
a P.A. of 102^deg^. The molecular gas is mostly on the
leading side of the stellar bar with P.A. ~90^deg^;
this is more clearly seen in the western half of the
bar, where the CO emission runs continuously down the
entire half of the bar. In the western half the H{alpha}
emission is offset another 3-4" toward the leading
side, with approximately the same P.A. In the eastern
half the H{alpha} emission is weak and no clear offset
is seen.
In the western half of the bar a relatively narrow
lane (10" in width) of CO emission emerges from the
bright, central 40" x 20", oval-shaped distribution of
CO emission. This lane extends to the west
(C1-> C2-> C3) and then curves inward to the spiral arms
from C3 to C4. As in NGC 3627 the CO intensity decreases
away from the central region. A spurlike feature,
labeled "C5," is seen 5" south of C1 extending almost 10"
(~780 pc) on the trailing side of the bar. These spurs
may play an important role in forming stars because they
have high gas density but are located in an area with
lower shear (Sheth et al. 2000).
The discrete H{alpha} structures (H1, H2, and H3)
are evenly spaced (10) and are on the leading edge of
the CO emission. A narrow ridge of diffuse H{alpha}
emission connecting these structures is offset north
from the CO by about 4". Farther west, toward the bar
end, a bright concentration of molecular gas,
labeled "C4," is coincident with the brightest H{alpha}
emission in this half of the bar, labeled "H4."
In the eastern half of the bar the two main
concentrations of CO, C6, and C7 are on the leading side
of the stellar bar. Two H II regions, H5 and H6, are
offset ~5" west of C7 and C6, respectively. Unlike the
western half, there is no clear leading offset of H II
regions from the CO emission. At the eastern bar end
bright CO and H{alpha} emission are present in the
regions labeled "C8" and "H7."
CO and H{alpha} emission are distributed on the
trailing and leading sides at the bar ends (10" north
of C4 and 12"-15" south of C8 and H7). Such a
morphology seems to be common in bars and is most
likely associated with inner rings (Buta & Combes 1996)
that encircle bars.

15. 2002A&A...389...68G
Re:NGC 4321
NGC 4321 (M100): this galaxy is not very inclined and thus the value
of the PA is not well constrained. On the other hand, there is a
rough agreement about the IA for the rest of the methods. We adopt
the kinematical values of Guhatakurta (1988).

16. 2001MNRAS.324..737R
Re:NGC 4321
A3 NGC 4321
A remarkable feature of the well-known grand design spiral NGC 4321 (M100)
is the number of recent supernovae in the galaxy, numbering 4 in the last
100 years. The Einstein observatory targeted the most recent, SN1979C, two
years after its appearance, but it did not detected the SN in X-rays
(Palumbo et al. 1981). Instead, Einstein saw a bright nuclear source and
a second source in the northern spiral arm. Immler, Pietsch & Aschenbach
(1998) report the results of a ROSAT HRI observation of NGC 4321 which
detects several point sources within the D_25_ ellipse of the galaxy,
including the bright nuclear source (which has a luminosity of
L_X_ ~ 6 x 10^39^ erg s^-1^) and SN 1979C (at a luminosity of
L_X_ = 1 x 10^39^ erg s^-1^), 16 years after its initial outburst.
NGC 4321 has not been studied spectroscopically in X-rays to date.

17. 2001ApJS..132..129M
Re:NGC 4321
NGC 4321 (M100). - NGC 4321 is a well-studied, grand design spiral
galaxy, type SAB(s)bc, located within the Virgo Cluster. A prominent
circumnuclear ring of recent star formation is inferred from H{alpha}
imagery, with a radius of ~15". The Astro-1 images are underexposed (see
Fig. 22a), revealing the overall spiral arm pattern only faintly. The
principal feature observed in the UV is a horseshoe-shaped broken
circumnuclear ring, resolved into ~15-20 knots, bracketing the optically
defined nucleus, which itself is fainter than the ring. This structure is
~16" x 24" in diameter, corresponding to a physical size of 1.2 x 1.7 kpc.
The star-forming ring appears to be associated with a weak stellar bar
observed at I (Pierce 1986) and in the NIR (Knapen et al. 1995). Despite
the shallow exposure, it is apparent that the circumnuclear ring dominates
the global UV light in this system.

18. 2000MNRAS.317..234P
Re:NGC 4321
3.10 NGC 4321
The prominent star-forming CNR of NGC 4321 (M100) has been studied in
great detail using e.g. optical and NIR imaging, CO interferometry, and
modelling (e.g. Pogge 1989a; Knapen et al. 1995a,b; Knapen 1998;
Wada et al. 1998; Garcia-Burillo et al. 1998; Ryder & Knapen 1999;
Knapen et al. 2000). Knapen et al. (1995b) concluded that M100 has a
circumnuclear starburst maintained by a global bar-driven density wave.
As already shown in detail by Knapen et al. (1995a), the K image of
this region is generally smooth, in contrast to the appearance in the
optical and H{alpha}. Two symmetrically placed 'hotspots', named K1 and
K2, are obvious in Fig. 2(j), both in emission in the broad-band image,
and as red features in the colour index images. Ryder & Knapen (1999)
recently used NIR imaging and spectroscopy to confirm the suspicion that
K1 and K2 are in fact regions of enhanced SF, and the K emission from
those regions is partly due to young stars (Knapen et al. 1995a,b). Our
NIR imaging confirms the location of dust lanes and suspected SF
regions, shown by Knapen et al. (1995a) in their I-K colour index map.
The locus of the circumnuclear ring-like structure shows up prominently
in all radial profiles. Unfortunately, no HST NIR images are available.

19. 2000AstL...26..285C
Re:NGC 4321
NGC 4321. The rows are rather blurred and appear as straightened
segments of the principal spiral arms. Two long, linear (!) dust lanes
are clearly seen on the inside of the largest row.

20. 2000ApJS..129...93F
Re:NGC 4321
NGC 4321 (M100). - We detect about 16 mJy of low surface brightness
emission in the nuclear region of this well-known grand design spiral in
the Virgo cluster. The tapered map shows emission slightly extended to
the northwest. NVSS detected 87 mJy, while WB92 measured 323 mJy and
BWE91 87 mJy. At 1.49 GHz, 0.9' resolution, Condon (1987) measured
180 mJy total flux in a ~ 3' x 2' region. At 4.9 GHz, 1.5" resolution,
Collison et al. (1994) detect a ringlike structure coincident with our
main feature. At 8.5 GHz, 0.2" resolution, these authors detect two
unresolved sources, having peaks of 0.37 mJy beam^-1^ (east) and
0.22 mJy beam^-1^ (west), respectively. The eastern radio source is
coincident with their 4.9 GHz main component, while the one to the west
is coincident with the optical nucleus and has a flat spectrum (Collison
et al. 1994).
We also detect an unresolved source, 1.5' to the southeast, with
1.3 mJy integrated flux, apparently located near the middle of the
southern spiral arm of the galaxy. It is clearly visible on the NGC 4321
map. We have identified this object with SN 1979C (Weiler et al. 1981).
Collison et al. (1994) measured 2 mJy for this SN 1979C, at 4.9 GHz.

21. 2000ApJ...534..670T
Re:NGC 4321
NGC 4321.-The M/L in the disk increases slowly by 2.0 times from r = 3
to 8 kpc. In the bulge region it seems to decrease inward and then
increase near the center, though the error is large. Some luminous
bumps of about 0.5 mag arcsec^-2^ are found at r = 700 pc and 5 and
11 kpc, which may be caused by spiral arms. The M/L increases
systematically inward by about 2 times from r = 300 to 150 pc.

22. 1999ApJS..124..403S
Re:NGC 4321
5.8. NGC 4321
NGC 4321 (M100) is a weakly barred galaxy with a nuclear bar. There
are a prominent pair of nuclear CO arms in the central 3 kpc and a sharp
condensation of CO at the nucleus. The bar-driven CO structure in the
central region of this galaxy has been discussed in detail in
Sakamoto et al. (1995), Wada, Sakamoto, & Minezaki (1998), and
Garcia-Burillo et al. (1998). The CO channel maps used to make the
moment maps in this paper are presented in Sakamoto et al. (1995).

23. 1999AJ....118.2331V
Re:NGC 4321
As is the case for SN 1979C (Van Dyk et al. 1999), the environment
of the SN I 1959E in M100 can be analyzed using the deep HST Key Project
images in F555W and F814W. In Figure 16 we show the SN environment,
using the absolute position from Porter (1993). The SN site is seen
against a dust lane in this deep image. Within the 1.5" radius error
circle four stars are detected with magnitudes m_F555W_ from 24.1 to
25.5 (-6.9 to -5.5 for distance modulus m - M = 31.04; Ferrarese et al.
1996) and colors F555W - F814W from 0.1 to 1.3 mag (these stars are
likely cool or reddened supergiants). We performed PSF-fitting
photometry on the region of the galaxy beyond the error circle, out to
about 7" from the SN position; in Figure 17 we show the resulting CMD.
We also show the B94 isochrones, reddened only by the Galactic
foreground (Burstein & Heiles 1984), although the reddening must clearly
be larger than this. A large number of populations are revealed from
these deep images, from quite blue to very red, including hot main
sequence stars, red supergiants, and some bright red giants. Reddening
and crowding are undoubtedly affecting the observed stellar magnitudes
and colors. However, we see that the photometry does not probe very deep
in age (only to ~100 Myr), in part because of the dust and the
relatively bright background. Most of the measured stars appear to have
ages of about 20-50 Myr. After all resolved stars were subtracted away,
we estimated the magnitude and measured the color of the diffuse
background and found m_F555W_ ~ 29.5 mag (the magnitude of pixels
1{sigma} above the mean background) and F555W - F814W ~ 0.7 mag. This
is consistent with a background of G stars, presumably giants with ages
>~100 Myr, or possibly fainter, reddened early-type stars (considering
the extensive dust lanes in this environment). From these results, we
cannot rule out that SN 1959E was a SN Ib/c, with a massive progenitor;
however, we consider it more likely that it was a SN Ia, based on its
environment.

24. 1999A&AS..138..253B
Re:NGC 4321
NGC 4321 (M100) - SNe 1901B, 1914A, 1959E, 1979C: all environments show
relatively bright and blue patches of light. The SN 1979C environment is
possibly the most promising, as it is known from radio observations to
be characterized by a dense environment (Weiler et al. 1981; Weiler et
al. 1986). This SN has also been optically identified. Only in this one
case (in this galaxy) is an emission patch clearly visible within
5 arcsec from the SN nominal position. Less compelling evidence has been
gathered for the other supernovae. SN 1979C is classified as a candidate
(see Table 3). The positions of SNe 1959E and 1979C are also identified
on some archival WFPC-2 observations. Multiple sources are present in
the immediate surroundings of the SNe. Many may well be star clusters,
others more directly related to the SN event. For example we know the
optical counterpart to SN 1979C has been identified among all other
sources (Van Dyk, private communication).

25. 1998PASJ...50..427S
Re:NGC 4321
NGC 4321: This Sc galaxy has a high concentration of H{alpha} emission
near to the nucleus, and the PV diagram has a tilted double-horn
feature, representing a rotating ring of H II regions. However, the
central region within a few arcsec is associated with a broader [N II]
feature than H{alpha}, representing a slightly tilted PV ridge,
suggesting a more compact, rapidly rotating component with a steeply
rising rotation curve. Except for this [N II] steep component, the HNRs
in the nuclear and disk components are normal for the usual H II
regions.

26. 1997AstL...23..656G
Re:MESSIER 100
M 100. Freedman et al. (1994b). The Hubble Space Telescope did not survey the
periphery and a quarter of the central part of the galaxy. The number of the
brightest blue stars must be considerably greater for the location of the
observed LF to be reconciled with the Cepheid distance modulus. The survey of
the brightest blue stars appears to be far from being complete even in the
observed part of the galaxy [see comments in Freedman et al. (1994b)]. There is
another possibility: M 101, as other Sb galaxies (M 31, M 81), may be a galaxy
with a deficit of blue stars. In such cases, the calibration relation (5) (see
below) of the LF method does not hold.

27. 1997ApJS..112..391H
Re:NGC 4321
NGC 4321.--The extended and highly asymmetric wings of the narrow lines in the
transition nucleus of NGC 4321 (M100) superficially resemble broad H{alpha}
emission. Indeed, if one naively assumed that the [S II] lines can be used to
model the narrow components of H{alpha} and [N II], one could force a broad
feature in the fit (e.g., as in NGC 1358). Fortunately, the data have high
enough S/N that differences in the narrow-line profiles are discernible. An
excellent fit to the complex can be achieved simply by constraining narrow
H{alpha} and [N II] to have identical profiles (Fig. 12b), and no broad
H{alpha} is necessary to fit this spectrum.

28. 1995AJ....109.1608R
Re:NGC 4321
With a total B magnitude B = 10.10, the SAB(s)bc starburst galaxy
NGC 4321 is the brightest spiral galaxy in the Virgo cluster (Sandage
1961).
The most striking features of the K band image are the H II regions at
the ends of the bar. In the K image, the bar is near the limit of
detectability. The bar is not at all evident in the B images. The I image
does not unambiguously reveal the bar.
The B image does, however, reveal a pair of dust lanes spiraling
inward to the smallest resolvable scales. These lanes cut across the bar,
giving the appearance of a ring of star formation around the nucleus. The
bar is hidden by the dust lanes. The situation is very similar to the
Seyfert galaxy NGC 1068 where Thronson et al. (1989) argue that a bar is
driving vigorous star formation in a ring that surrounds the central
disk.
The spectrum of the nuclear region of this galaxy is dominated by H II
emission (Keel 1983). Keel's 8.1 arcsec diameter aperture was small
enough that the star formation at the ends of the bar would have been
excluded.
Arsenault et al. (1988) obtained Fabrey-Perot spectra H{alpha} of
NGC 4321. Their data show a ring of H{alpha} around the nucleus at a
distance ~7 arcsec. Their peak H {alpha} flux corresponds to knots in my B
image. These knots fall on a line nearly orthogonal to the K band bar.
Their study indicates that the northwestern arm of the galaxy is
blueshifted and the southeastern arm is redshifted. In this galaxy, as in
most spiral galaxies, the spiral arms are trailing. Their velocity field
map indicated a steep velocity gradient in the nuclear region of ~230 km
s^-1^ kpc^-1^, indicative of a high mass concentration.
Further, Arsenault et al. see a strong perturbation of the velocity
field at a radius of 18 arcsec. They found that an oval stellar mass
distribution was a better fit to their kinematic data than a bar.
Examination of the K image reveals a strong oval-shaped component of
light aligned with the bar. Arsenault's data argue that the bar is likely
to be quite weak, and that the mass is dominated by the oval mass
distribution.
The isophotal structure of NGC 4321 is highly complex. Since the bar
is so weak (it is only slightly above the read noise), I have opted to
fit elliptical isophotes and note the perturbations one would expect to
arise from the bar.
The nuclear region isophotes twist by > 50^deg^. The twisting is well
above the error in the position angle determination. Arsenault et al.
(1988) also noted twisting and ellipticity changes in their H{alpha}
data. However, their data were not adequately sampled to measure these
effects. The twist are consistent with Arsenault's contour plots.

29. 1994MNRAS.268..203C
Re:NGC 4321
NGC 4321 (M100) is a `grand design' spiral galaxy of type Sc(s)I in the
Virgo Cluster. It has two well-developed spiral arms delineated by
ordered H II regions which are clearly seen in the H{alpha} maps of
Arsenault, Roy & Boulesteix (1990) and Cepa & Beckman (1990). The 6-cm
VLA B-array image shows clearly the radio supernova SN 1979c (Panagia et
al. 1980; de Vaucouleurs et al. 1981; Weiler et al. 1992) which in our
image has a peak brightness of 2 mJy beam^-1^. The radio emission in the
nuclear region forms a ring-like structure with several compact knots, in
addition to the emission from near the centre of the ring.
There are only two compact components seen in the 3.6-cm map, both of
which are unresolved. The rest of the extended emission is resolved out.
The stronger source, 23.46+57.7, is coincident with the dominant peak in
the ring-like structure seen in the 6-cm image and might be related to an
optical condensation seen in short-exposure plates (Weiler et al. 1981),
while the weaker source, 22.98 + 57.8, is likely to be associated with
the optical nucleus at {alpha}(B1950)= 12^h^20^m^22.96^s^,
{delta}(B1950) = 16^deg^05'56.5" (Penhallow 1980). Comparison of the two
images suggests that this central feature has a flat radio spectrum,
which is consistent with its being a nuclear component.

30. 1994CAG1..B...0000S
Re:NGC 4321
VCC 596
Hubble Atlas, pp. 28, 31
Sc(s)I
PH-742-S
April 8/9, 1954
M100
103aE + RG2
90 min
Two of the largest spirals in the Virgo
Cluster are shown on this page. As listed in the
RC2, the angular sizes of NGC 4321 and NGC 4303
are 6.9' and 6.0', respectively, measured
to an isophote of 25 mag arc sec^2^. Photographs
of many Virgo Cluster spirals are shown
elsewhere (Sandage, Binggeli, and Tammann
1985a), printed to a common angular scale,
showing thereby that the two galaxies on this
panel are among the largest spirals in the cluster.
The print shown here of NGC 4321 is from
a red plate sensitive to H{alpha} radiation. It was from
this plate, taken in 1954, that it came to be
understood that most of the knots in spiral
galaxies which Hubble (1936a) had used with his
calibrations of brightest stars are HII regions
(Humason, Mayall, and Sandage 1956, Appendix C).
From this it was evident that Hubble's
distance scale must be revised upward by a much
larger factor than the correction determined by
Baade for M31.
The two principal arms in NGC 4321 begin
near the center as dust lanes. A side of one lane
attaches smoothly to the beginning of one of the
principal luminous arms. The principal dust lane
on the other side cuts across the beginning of the
first luminous arm at a steep angle.
The largest HII regions resolve at about the
2" level. Individual brightest stars are difficult to
separate from HII regions on blue or red plates.
On yellow plates, where no HII-region emission
lines exist, brightest-star candidates may exist,
starting at apparent magnitude about V = 21.5.

31. 1993ApJS...86....5K
Re:NGC 4321
NGC 4321; Sbc, hot spot.
This is the largest spiral in the Virgo Cluster and is another example of
a "hot spot" galaxy. The ring, about 13" in radius, contains four
distinct H II regions, where strong star formation is present (Pierce
1986; Arsenault et al. 1988). The UV spectra presented here are of two of
these H II regions which are contained in the nuclear region of the
galaxy, and have been studied by Panagia et al. (1980). They conclude
that the absorption features are mostly due to the interstellar medium
present in the halos and in the disks of both our Galaxy and NGC 4321.

32. 1993A&AS...97..887B
Re:NGC 4321
NGC 4321 is a bright Virgo cluster galaxy with a nuclear ring seen in
ionized gas (P89). The KY observations show somewhat lower brightness
temperatures, even taking beam dilution into account.

33. 1976RC2...C...0000d
Re:NGC 4321
= M100
= Holm 387a
Pair with NGC 4312 at 18 arcmin
Description and Classification:
P.A.S.P., 77, 287, 1965.
P.A.S.P.,79, 152, 1967.
IAU Symp. No.38, 11, 1970.
Photograph:
A.J., 74, 515, 1969.
Ap. J., 176, 21, 1972.
Ap. J., 194, 559, 1974.
Astr. Ap., 29, 249, 1973.
IAU Symp. No.38, p.11, 1970.
Photometry (UBV):
Sov. A.J., 16, 71, 1972.
Ap. J., 176, 21, 1972 (Dwarf companions).
Spectrum:
A.J., 74, 515, 1969.
Ap. J., 186, 807, 1973.
Spectrophotometry:
Observatory, 88, 239, 1968.
Rotation Curve and Mass Determination:
Ap. J., 186, 807, 1973.
HII Regions:
Ap. J. Suppl., 27, No. 239, 1974.
Ap. J., 194, 559, 1974.
Distance Modulus:
Ap. J., 194, 559, 1974.
SN1901B and SN1914A:
P.A.S.P., 29, 180, 1917.
P.A.S.P., 29, 213, 1917.
Ap. J., 88, 285, 1938.
SN1959E (noted as SN1960 in RC1).
HI 21cm:
M.N.R.A.S., 150, 337, 1970.
Radio Observations:
A.J., 78, 18, 1973.
Astr. Ap., 29, 249, 1973.

34. 1973UGC...C...0000N
Re:UGC 07450
SAB(s)bc (de Vaucouleurs), Sc- (Holmberg)
SN 1901b, 1914a, 1959e
12 20.5 +16 11 = NGC 4322 = NGC 4323 at 5.2,19, 0.9: x 0.7:, late spiral?,
S0: (de Vaucouleurs), m=15.7
12 20.8 +16 05 = NGC 4328 at 6.1, 92, (0.9 x 0.8), S0:, m={15.0}
{UGC incorrectly notes "15.2". H. Corwin}

35. 1964RC1...C...0000d
Re:NGC 4321
= Messier 100
= Holm 387a
Very bright nucleus with inner spiral structure: 0.4 arcmin x 0.3 arcmin.
Broad, weak, diffuse bar: 1.9 arcmin x 1.2 arcmin. Spiral pattern of dark
lanes in the lens. Pseudo (r): 1.9 arcmin x 1.7 arcmin. Partially resolved,
regular arms. Pseudo (R):5.0 arcmin x 3.9 arcmin.
Lick 13, Heid 9 and Lund dimensions are for the bright part only.
(B-V) constant with log A/D(0).
Pair with NGC 4312 at 18 arcmin.
Photograph:
A.J., 61, 160, 1956.
Ap. J., 127, 522, 1958.
Ap. J., 135, 7, 1962.
Handbuch der Ap., 5, 2, 803, 1933.
Photometry:
Izv. Pulkovo, 20, No.156, 87, 1956.
Sov. A.J., 32, 16, 1955.
HII Regions:
Zeits. fur Ap., 50, 168, 1960.
Observatory, 79, 54, 1959.
SN 1901
P.A.S.P., 29, 180, 1917.
Lick Obs. Bull., 300, 1917.
Ap. J., 88, 292, 1938.
SN 1960
P.A.S.P., 73, 175, 1961.

36. 1961Hubbl.B...0000S
Re:NGC 4321
Messier 100
Sc
PH-743-S
Apr. 8/9, 1954
103aD + GGl4
60 min
Enlarged 5.2X
NGC 4321 is the brightest spiral in the Virgo Cluster.
The galaxy has characteristics of both NGC 5194 (M51)
and NGC 5457 (M101). There are multiple arms, but
only two of the arms are bright. The faint secondary
arms lie between the principal arms on the east side of the
nucleus, completely filling the space between the bright
arm closest to the nucleus on the north side and the
extension of the second main arm in the northeast quadrant
after it has spiraled through 360 degrees. The illustration on the
facing page was slightly overexposed to show these faint
details. A negative reproduction is given in Ap. J., 127
513, 1958, which shows not only the outer spiral features
but also the details of the multiple dust lanes crossing the
central lens.
Two principal dust lanes go into the very center of M100
in a spiral pattern. The center is illustrated on page 31.
Most of the knots that appear in the two main spiral
arms are HII regions, as can be seen from the reproduction
of a plate sensitive to H{alpha} and a second plate sensitive
to an emission-free spectral region shown in Figure 9 of the
Ap. J. reference above.
Individual stars do appear in M100, but they are much
fainter than the H II regions. Comparison of the illustration
of M100 in the Atlas with the negative prints in Figure
9 of Ap. J., 127, is interesting. The photographic plate
from which the negative print was made for the left half of
the reproduction in Ap. J. is the same one that this Atlas
illustration comes from.
The estimated distance modulus of M100 is (m-M) = 30.7.
Measurement on the original plate shows that, at this
distance, the linear width of the two spiral arms averages
about 900 parsecs -- about 3 times the width of arms
in M101 and about twice what is estimated for our own
galaxy.

37. 1961Hubbl.B...0000S
Re:NGC 4321
Messier 100
Sc
H-1602-H
Mar. 6/7, 1934
E40
15 min
Enlarged 25.0X
The four illustrations on the facing page are greatly
enlarged reproductions of the nuclear regions of near-by Sc
galaxies. The spiral arms which begin near the center of
most galaxies are dust arms. The arms usually do not
become luminous until they have left the nucleus. There is
no question that the dark regions between the luminous
arcs in this picture of M100 are filled with dust.
Continuations of these dark lanes form the two principal dust
arms which wind out through the lens and end on the
insides of the two most luminous outer arms. Page 28
gives the complete view of M100. The continuation of the
inner dust lanes shown here as they wind outward is best
shown in a negative print in Ap. J., 127, 513, 1958.

38. 1918PLicO..13....9C
Re:NGC 4321
Vol. VIII, Plate 35. A bright, regular, nearly round spiral 5' in diameter.
Very faint stellar nucleus surrounded by bright, short whorls, forming a
central oval. The outer whorls are rather open, quite regular, and show
many stellar condensations. Two novae have appeared in this spiral.
M. 100. 15 s.n.


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