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Notes for object MESSIER 033

22 note(s) found in NED.


1. 2009MNRAS.397.2148G
Re:NGC 0598
NGC 598 (M33). For the Scd galaxy M33, we corrected the galaxy's apparent B-band
magnitude of 6.27 mag (RC3) for 0.18 mag of Galactic extinction [via NASA/IPAC
Extragalactic Database (NED)], and using an inclination of 54{degree} we
corrected for 0.35 mag of internal extinction (Driver et al. 2007). This
resulted in an absolute B-band magnitude of -18.78 mag for this galaxy. The
average B-band B/T flux ratio for Scd galaxies is 0.027 (Graham & Worley 2008)
giving an expected bulge magnitude of -14.86 mag. From a bulge/disc
decomposition of M33, Bothun (1992) reports a comparable B-band bulge-to-disc
ratio of 0.02 (see also Minniti, Olszewski & Rieke 1993; Regan & Vogel 1994;
Mighell & Rich 1995). We do, however, note that while there is an obvious excess
of flux above the inward extrapolation of this galaxy's outer exponential light
distribution, M33 does not possess a traditional bulge (Wyse, Gilmore & Franx
1997; Brown 2009). The central excess of stars might be better thought of as a
'pseudo-bulge' rat her than a classical bulge, i.e. a small elliptical galaxy,
and readers may ignore this system if they wish.
The central bulge regions of M33 have been reported as 8-10 Gyr old (Li et
al. 2004), and Wyse et al. (1997) note -2.2 < [Fe/H] < -0.7. This implies
-0.11 < log[M/L_B_] < 0.17, and we adopt the mid-point giving M/L_B_= 1.1
for the (pseudo-)bulge in M33.
The NC mass of 2 * 10^6^ M_{sun}_ was obtained from Kormendy & McClure
(1993). NC masses should perhaps not be obtained from the virial theorem's
approximation, M~={sigma}^2^R, because they are not isolated systems, but
reside within the potential and pressure of their host spheroid.
As a rough check, we note that the nuclear V-I colour is 0.85 +/- 0.05,
while the galaxy V-I colour is 1.0 (Gebhardt et al. 2001). Schmidt, Bica &
Alloin (1990) have reported that intermediate to old stars, with [Fe/H]> 0.1,
dominate the NC, and so from a diagram of M/L_B_ versus V-I (akin to Fig.
A1) one has that log[M/L_B_]= 0.27 +/- 0.22 dex. Using the B-band NC magnitude
of -10.2 mag from Kormendy & McClure (1993), the NC mass is 3 * 10^6^
M_{sun}_.

2. 2008MNRAS.390..466E
Re:UGC 01117
UGC 1117. This galaxy is the famous M33. Because of the limited field of view of
GHASP, we only observed the solid body central part of the rotation curve. The
external round shape structures in the different images are due to edge-effects
of the interference filter vignetting the field of view.

3. 2007MNRAS.382.1552L
Re:NGC 0598
NGC 598 - M 33: This Local Group galaxy has a stellar cluster like nucleus with
a substantial colour gradient, the centre being bluer (Kormendy & McClure 1993;
Lauer et al. 1998). The X-ray and radio sources coincident with the nucleus have
properties very similar to those of high-state stellar black hole candidates
found in our Galaxy (Dubus & Long 1999; Gordon et al. 1999). The mass of any
central black hole in NGC 598 is constrained to be <1500 M_sun_ (et al.
2001). The peculiar [N II] {lambda}{lambda}6548,6584-H{alpha} features seen in
Fig. 2, with [N II] in emission and H{alpha} in sharp, deep absorption, have
been already noted by Rubin & Ford (1986). Our spectral analysis shows that the
nucleus underwent a strong starburst episode about 1 Gyr ago and has had little
star-forming activity ever since.

4. 2004ApJ...608...42S
Re:NGC 0598
NGC 598. Column (2) of Table 3 lists the distance published by Freedman
et al. (1991) based on BVRI CCD photometry of 19 Cepheids originally
discovered by Hubble (1926). The distance moduli calculated in this
paper are based on all Cepheids given a quality index of a, b, or c in
Freedman et al. (1991), for which both V and I magnitudes are available.

5. 2002AJ....124..675C
Re:UGC 01117
M33. The 1.4 GHz flux density is from the NRAO 91 m telescope
(Dennison et al. 1975).

6. 2002A&A...389...68G
Re:NGC 0598
NGC 598: our two methods are in good agreement but the values
that they give are not in agreement with the rest of the
literature values, probably due to an incomplete sampling of
the galaxy disk in the HII region catalog from Hodge (1999).
Thus, we prefer to keep the mean of the kinematically derived
values.

7. 2001ApJS..132..129M
Re:NGC 0598
NGC 598 (M33). - This object, of type SA(s)cd at a distance of
D ~ 700 kpc, 52' x 56' in size, and inclined ~55^deg^, is the least
luminous of the three spiral galaxies in the Local Group. The UIT images
were centered on OB association NGC 595 to permit the Hopkins Ultraviolet
Telescope to obtain spectra during the UIT exposures. M33 extends slightly
beyond the UIT field, but almost all of the UV-luminous regions are
contained within the 40' field. The UIT, H{alpha}, and R-band images are
presented in Figure 6a.
The UIT images are almost completely filled with UV-bright knots and
clusters, which roughly trace out spiral arms. High surface brightness UV
features are found at all radii, but there is considerable diffuse UV light
as well. The galaxy is considerably more irregular and much less centrally
concentrated in the UV than in the optical bands. Qualitatively, the spiral
structure is traced better by the UV continuum than by the (younger)
H{alpha}-emitting regions. Several giant extragalactic H II regions
(GEHRs), including NGC 604, are visible in these frames. NGC 604 is located
~12' NE of the nucleus and is prominent in both the UV and H{alpha} images.
Massey et al. (1996) have cataloged the 356 brightest UV objects on the UIT
frames and obtained follow-up spectroscopy for about half of these. Most
are classified as O and early-B supergiants.
The UV morphology of M33 has been discussed by Landsman et al. (1992)
using UIT data and by Buat et al. (1994) using lower resolution data
obtained with the FOCA balloon-borne telescope. The FOCA image contains the
entire galaxy at 20" resolution in a bandpass centered at 2000 A.
Buat et al. (1994) find that about 80% of the FUV light is contributed by
discrete sources rather than a diffuse background. This is a larger
discrete contribution than found in more luminous spirals like M74
(Cornett et al. 1994). Keel (1998) has used Voyager 2 data to obtain
one-dimensional spatial profiles for M33 in Ly{alpha} and the 800-1200 A
continuum and compared this to the UIT photometry.
The UV brightness profiles shown in Figure 6b display a steep decline to
a radius of 3', followed by a long plateau, then a gradual decline. This
pattern has been noted in other disk galaxies imaged by UIT (Fanelli et al.
1997b) and is distinct from the more smoothly declining optical broadband
radial profiles. For r >~ 3, the R-band profile is well fitted by an
exponential, whereas the UV bands exhibit considerably more structure.
Inflections in the UV profiles are caused by luminous OB associations, in
particular the "bump" at r ~ 14' due to NGC 604. Landsman et al. (1992)
find scale lengths for the best-fit exponentials of 5.6' in the MUV and
7.0' in the FUV. These values imply a gradient toward bluer (UV-visible)
and (FUV-MUV) colors with increasing radius, as seen in the color profiles
in Figure 6b, and in other disk galaxies imaged by UIT (M74 and M81). Over
the entire disk {DELTA}(FUV-MUV) ~ -0.6 mag, about of the gradient found
in M31. Over the same radius, {DELTA}(NUV-R) ~ -1.0 mag. Both internal
reddening and changes in the history of star formation can produce the
observed color changes (Landsman et al. 1992; Cornett et al. 1994),
although the larger amplitudes seen in objects like M74 and M81 argue for
the latter.

8. 2000MNRAS.319...17L
Re:NGC 0598
NGC 598 (M 33): No analysis of X-ray data for this galaxy has been done in
this paper. Several point sources have been detected with the Einstein and
ROSAT HRI in this spiral galaxy (Markert & Rallis 1983; Schulman & Bregman
1995). Those sources located within the central ~6 x 6 arcmin^2^ region
are listed in Table 6. The most striking source is the nucleus, with a
luminosity of 10^39^ erg s^-1^ which makes it a good AGN candidate.
However, the nucleus is not detected at radio wavelengths and shows very
little line emission in the optical, (Schulman & Bregman 1995; Paper III).
Nuclear dynamical studies also give a strict limit for a central black hole
mass of <~ 5 x 10^4^ M_sun_ (Kormendy & McClure 1993). ASCA observations
show that the X-ray emission from this source is much softer than the
typical AGN spectrum, and it does not show signs of variability to within
10 per cent on time-scales of 100 min (Takano et al. 1994). This almost
certainly excludes the possibility of an active nucleus in NGC 598. In
fact, a disc blackbody fit to the ASCA data shows that its emission is
similar to Galactic black hole candidates (Takano et al. 1994; Colbert &
Mushotzky 1999). Diffuse emission around the nucleus has been detected in
ROSAT HRI as well as PSPC observations (Long et al. 1994; Schulman &
Bregman 1995; Read et al. 1997).

9. 2000ApJ...534..670T
Re:NGC 0598
NGC 598.-This is a small-mass galaxy that has a mildly rising RC
reaching only about 100 km s^-1^ in the disk region. The M/L increases
slowly by 1.7 times from r = 1 to 3 kpc. In the bulge region it appears
to decrease inward rapidly, with large errors. It also appears to
increase inward within 150 pc, but that is not conclusive because the
spatial resolution is 210 pc.

10. 1999ApJ...519...89C
Re:NGC 0598
NGC 598 (M33).-M33 is a normal spiral galaxy in the Local Group. Of
all of the galaxies in the Local Group, it has the most luminous X-ray
nucleus. Recently, Dubus et al. (1997) have found evidence for 106 day
periodic variability of the nuclear X-ray source and argue that the
source is a black hole X-ray binary with a ~10 M_sun_ primary (for an
Eddington ratio of unity). The ASCA spectra of the central X-ray source
have been analyzed by Takano et al. (1994). We discuss ASCA observations
of this X-ray source in section 5.

11. 1997AstL...23..656G
Re:MESSIER 033
M 33. Ivanov et al. (1993) (photographic photometry). The LF that was
constructed from the data of Humphreys and Sandage (1980)(Fig. 1a, dashed line)
suggests that the magnitude V(5) is slightly fainter.

12. 1997AstL...23..644G
Re:MESSIER 033
M 33. Van den Bergh (1992) (a recommendation that is based on an analysis of
the studies of other authors); Ivanov et al. (1993) (no. 226, R96, R341),
(VarC, nos. 324, 448).

13. 1997AJ....114.2428S
Re:NGC 0598
NGC 598 (M33): This nearby Sc galaxy is a member of the local group, showing
diffuse, rather amorphous, spiral arms, and the bulge is small in size and
luminosity. The PV diagram has been obtained along PA=54^deg^, about 30^deg^
different from the true PA at 23^deg^. The CO emission is weak, and no rotating
disk is visible in the central 30" (110 pc). Therefore, no rotation curve was
obtained for this galaxy.

14. 1996ApJ...473..117S
Re:MESSIER 033
M33.--The observed rotation curve of this classic nearby Sc spiral is from an
unpublished analysis by O. M. Kolllman (1995) based upon observations of Deul
& van der Hulst (1987; see also Rhee 1996). The large number of independent
observed points on the rotation curve, due to the large angular size this
object, and the well-established Cepheid distance (Madore & Freedman 1991)
make this a good case for detailed rotation-curve fitting, although there is a
significant warp in the outer regions.

15. 1995ApJ...441..568S
Re:[SB95] 16
RH 16 (M33 X-8).-This source is located at the optical nucleus, to
within the positional accuracy of the ROSAT HRI and is the strongest X-
ray source in M33, by about a factor of 10.
The origin of the X-ray emission from M33 X-8 has been a mystery for
some time (Markert & Rallis 1983). Its X-ray luminosity of about 10^39^
ergs s^-1^ is low for an AGN but quite high for a Galactic X-ray source,
although a number of point sources outside the Local Group have been
found with comparable or larger X-ray luminosities (most recently,
Collura et al. 1994 determined the X-ray luminosity of a variable point
source in M82 to be at least 5 x 10^39^ ergs s^-1^). The observed optical
and near-infrared spectra and colors of the semistellar (optical FWHM ~
0.8") nucleus might be produced by a young, metal-rich population,
suggesting that it was formed by bursts of star formation resulting from
inflow of gas into the center of M33 (van den Bergh 1991).
The nucleus has no detected 20 cm continuum emission (van der Kruit
1973), no hydrogen line emission observed (O'Connell 1983), little
forbidden line emission (Rubin & Ford 1986), and infrared colors quite
unlike those of an AGN (Gallagher, Goad, & Mould 1982). The IPC spectrum
can be fitted with a power law with energy index, {alpha}, between 1 and
2 (Trinchieri et al. 1988). Wilkes & Elvis (1987) find that the best-fit
power-law slopes of 33 quasars observed with the Einstein IPC have a wide
range (-0.2 <= {alpha} <= 1.8) but are strongly grouped around values of
~0.5 for radio-loud quasars and ~1.0 for radio-quiet quasars. If there is
a low-luminosity active nucleus in M33, the lack of activity at
wavelengths other than the X-ray band would make it very unusual.
The stars in the nucleus comprise only a small fraction of all the
stars in M33, so that the a priori probability of a binary in the nucleus
with an X-ray luminosity 10 times that of any other source in M33 is
small. The source is variable by a factor of 2 on 6 month timescales
(Markert & Rallis 1983; Peres et al. 1989) and so is unlikely to be the
superposition of more than two X-ray binaries. The Einstein IPC spectrum
is not consistent with any of the known spectra of X-ray binary sources
(Trinchieri et al. 1988).
RH 16 is 26.5" +/- 4" away from SNR 013100+30241, so any X-ray emission
from the supernova remnant will formally contribute to the flux listed in
Table 1, but this contribution is small compared to that of the nuclear
source.

16. 1994CAG1..B...0000S
Re:NGC 0598
M33
Hubble Atlas, p. 36
Sc(s)II-III
PR-243-Schweizer
Aug 23/24, 1974
103aO + GG13
120 min
The wide-field image of M33 here was taken
with the Palomar 60-inch reflector by Schweizer.
The telescope's remarkable field of more than 1^deg^
(diameter) with its large plate scale of 16 arc
seconds per mm is the optical design of I. S.
Bowen. His design of the 60-inch Palomar reflector
was the prototype for the even-wider-field Las
Campanas 40-inch Swope Telescope and the
remarkable Las Campanas 100-inch du Pont
reflector, both of whose optics were also designed
by Bowen.
The stellar content of M33 has been
discussed in detail by Humphreys and Sandage
(1980). They addressed the spiral pattern, the
associations, the dust patterns, and the brightest
resolved red and blue stars. The brightest blue
stars begin to resolve at B = 15; the brightest red
supergiants begin to resolve at V = 16.5.
Ten spiral arms were identified and mapped
in that study. The two main inner arms have a
different projected geometry than the outer eight
arms. This was interpreted (Sandage and
Humphreys 1980) as a warp of the spiral-arm
plane, as in the tilted angular ring model of
Rogstad, Wright, and Lockhart (1976).
The surface brightness of the disk is
moderate-to-light. M33, the prototype for ScII-III
galaxies, is the template by which other
galaxies of this type and luminosity class are
compared. Its near-twin is NGC 300, shown on
the previous panel.

17. 1993ApJS...86....5K
Re:NGC 0598
NGC 598 (M33); Scd.
The spectrum of the center of this nearby Scd galaxy is basically flat
(F_{lambda}_ is proportional to {lambda}^0^) across the entire IUE wave
band. At shorter wavelengths the continuum is rich in absorption features
from massive hot stars.
M33 is a bright galaxy in the X-ray band, and indeed its nucleus is the
brightest X-ray source in the Local Group (Markert & Rallis 1983). An
interpretation of the nucleus as a low-luminosity active nucleus has been
suggested by Trinchieri, Fabbiano, & Peres (1988). Ciani, D'Odorico, &
Benvenuti (1984) compared stellar synthesis models against the IUE
spectrum of the center and found a best fit with a multigenerational
model, with a young component of age ~10^7^ yr and an old component with
age ~10^10^ yr superposed.
M33 has been very thoroughly studied in the UV; but most work concerns
the properties of individual constituents of the galaxy, as opposed to
the general stellar population of the central regions. The OB stars of
M33 were studied by Massey, Hutchings, & Bianchi (1985); the M33
supernova remnants were studied by Blair, Kirshner, & Raymond (1984a);
and the M33 Hubble-Sandage variables were studied by Humphreys et al.
(1984). Surprisingly, only three short-wavelength spectra and one
long-wavelength spectrum of the center of M33 are in the IUE archives.

18. 1976RC2...C...0000d
Re:NGC 0598
= Messier 033
Member of the Local Group.
Spiral Structure:
A.J., 69, 744, 1964.
P.A.S.P., 79, 119, 1967.
Astr. Ap., 11, 468, 1971.
Ap. J., 164, 411, 1971.
Ap. J., 191, 317, 1974.
Photograph:
A.J., 69, 744, 1964.
Ann. Ap., 28, 683, 1965.
P.A.S.P., 79, 119, 1967.
IAU Symp. No. 29, 434, 1968.
IAU Symp. No. 38, 73, 1970.
Astr. Ap., 11, 468, 1971.
Astr. Ap., 12, 379, 1971.
Astr. Ap., 29, 231, 1973.
Astr. Ap., 33, 161, 1974.
Astr. Ap., 37, 33, 1974.
Ap. J., 179, 445, 1973.
Ap. J., 190, 525, 1974.
Ap. J., 191, 63, 1974.
Photometry: (UBV)
A.J., 69, 744, 1964.
Astr. Ap., 5, 13, 1970.
Ap. J., 164, 411, 1971.
Bull. A.A.S., 4, 332, 1972
Bull. A.A.S., 5, 348, 1973.
Ap. J., 191, 63, 1974.
Photometry: (5 Color)
A.J., 73, 313, 1968.
Photometry: (IR)
N.R.A.S., 162, 359, 1972.
Photometry: (Absorption and Color Excess)
A.J., 72, 526, 1967
A.J., 74, 1000, 1969.
Ap. J., 191, 63, 1974.
Photometry: (Distance Modulus)
A.J., 72, 526, 1967.
Ap. J., 191, 603, 1974.
Photometry: (Star Counts)
Ap. J., 191, 317, 1974.
Photometry: (Wolf-Rayet Stars)
Bull. A.A.S., 3, 240, 1971.
Ap. J., 172, 577, 1972.
Photometry: (Variable Stars and Novae)
Astr. Ap., 22, 453, 461, 1973.
Spectrum and Internal Motions:
A.J., 69, 744, 1964.
Spectrophotometry:
Sov. A.J., 16, 628, 1973.
Ap. J. Let., 193, L49, 1974.
Spectrophotometry: (Far UV)
N.A.S.A., SP 310, 559, 1972.
Polarization:
Astrofizika, 4, 409, 1968.
Dynamics and Rotation Curve and Mass Determination:
M.N.R.A.S., 129, 313, 1974.
Ann. Ap., 31, 63, 1968.
Astr. Ap., 9, 350, 1970.
Astrophys. Lett., 8, 17, 1971.
Ap. Space Sc., 29, 61, 1964.
Cont. Asiago Obs. No. 300, 109, 1973.
HI 21cm:
A.J., 75, 514, 1968.
Astrophys. Lett., 4, 47, 1969.
Astrophys. Lett., 7, 209, 1970.
Mem. R.A.S., 74, 123, 1970.
M.N.R.A.S., 153, 9, 1971
M.N.R.A.S., 155, 337, 1972
M.N.R.A.S., 163, 163, 1973.
I.A.U. Symp. No. 44, 12, 67, 1972.
Astr. Ap. Suppl., 7, No. 4, 1972.
Ap. J., 169, 235, 1971
Ap. J., 179, 453, 1973.
IAU Symp. No. 58, 122, 1974.
HII Regions:
Ann. Ap., 28, 633, 1965.
Ap. Space Sc., 4, 327, 1969.
Ap. J., 179, 445, 1973
Ap. J., 190, 525, 1974.
Astr. Ap., 37, 33, 1974.
HII Regions: (Spectrum)
M.N.R.A.S., 129, 309, 1964.
Astrophys. Lett., 8, 17, 1971.
HII Regions: (Spectrophotometry)
A.J., 72, 783, 1967.
Ap. J., 151, 491, 1968
Ap. J., 159, 809, 1970.
Ap. J., 161, 33, 1970
Ap. J., 168, 327, 1971.
P.A.S.P., 82, 636, 1970.
Bull. A.A.S., 5, 349, 448, 1973.
Astr. Ap., 28, 447, 1973
Astr. Ap., 33, 61, 1974.
HII Regions: (H2O upper limit)
Ap. J., 169, 207, 1971.
HII Regions: (Photometry: 10 and 20 microns)
Ap. J. (Letters), 193, L7, 1974.
HII Regions: (1415 MHz)
Astr. Ap., 32, 363, 1974.
H{alpha} Interferometry:
Ann. Ap., 31, 63, 1968.
Astr. Ap., 9, 181, 1970.
Astr. Ap., 12, 379, 1971.
Astr. Ap., 28, 447, 1973.
Astr. Ap., 33, 161, 1974.
IAU Symp. No. 60, 249, 1974.
Radio Observations:
Ann. Ap., 26, 343, 1963.
P.A.S.P., 75, 404, 1963.
Ap. J., 142, 1333, 1965
Ap. J., 174, 293, 1972.
Sov. A.J., 13, 881, 1970.
M.N.R.A.S., 155, 337, 1972.
Bull. A.A.S., 5, 29, 1973.
Astr. Ap., 29, 231, 1973
Astr. Ap., 32, 363, 1974.

19. 1973UGC...C...0000N
Re:UGC 01117
SA(s)cd (de Vaucouleurs), Sc+ (Holmberg)
M 31 sub-group
SN? 1928 (Baade), probably nova

20. 1964RC1...C...0000d
Re:NGC 0598
= Messier 033
Local Group member.
Photograph:
Ap. J., 63, 236, 1926.
Ritchey, L'Evolution de l'Astrophotographie..., S.A.F., Paris, 1929.
Photometry:
Ap. J., 83, 424, 1936.
Ap. J., 91, 528, 1940.
Ap. J., 108, 415, 1948.
Ap. J., 130, 728, 1959.
M.N.R.A.S., 97, 423, 1937.
Medd. Lund, I, 175, 1950.
Medd. Lund, II, 128, 1950.
Izv. Pulkovo, 20, No.156, 87, 1956.
Sov. A.J., 32, 16, 1955.
Spectrum:
Ap. J., 95, 52, 1942.
P.A.S.P., 51, 112, 1939.
P.A.S.P., 72, 283, 1960.
Polarization:
Bull. Abastumani, No.18, 15, 1955.
Dynamics, Rotation and Mass:
Ap. J., 63, 67, 1926.
Ap. J., 95, 5, 1942.
Ap. J., 95, 24, 1942.
Ap. J., 97, 117, 1943.
Ap. J., 104, 223, 1946.
Zeit. fur Ap., 35, 159, 1954.
A.J., 59, 273, 1954.
A.J., 67, 592, 1962.
HII Regions:
Obs., 79, 54, 1959.
Zeit. fur Ap., 50, 168, 1960.
HII Emission:
P.A.S.P., 69, 356, 1957.
B.A.N., 14, 19, 323, 1957.
A.J., 67, 217, 1962.
Radio Emission:
M.N.R.A.S., 119, 297, 1959.
M.N.R.A.S., 122, 479, 1961.
P.A.S.P., 72, 368, 1960.
Ap. J., 133, 322, 1961.
A.J., 68, 70, 295, 1963.

21. 1961Hubbl.B...0000S
Re:NGC 0598
Messie 033
Sc
PS-421
Jan. 6/7, 1951
103aO
12min
Enlarged 4.9X
NGC 0598 (M33) is the nearest Sc to our own galaxy.
It is a member of the Local Group. The distance modulus is
probably close to (m-M) = 24.5 (Sandage, Ap. J, 127 513,
1958). The limiting magnitude of the 200-inch is about
m(pg) = 23.0. This means that the stellar content of M33
can be studied in detail down to stars of absolute magnitude
M(pg) = -1.5. Bright O and B stars, Cepheid variables,
globular and open star clusters, novae, irregular variables,
and HII regions are known in M33. The first extensive
study of the stellar content was made by Hubble in 1926
(Ap. J., 63, 236, 1926). No comparable study has been
made in recent times.
Spiral structure is easy to trace in M33. The arms are
"massive" in the sense used by Reynolds and by Hubble
(Observatory, 50, 1927). The arms are completely re-
solved into bright stars. Most of these are blue super-
giants, but there are also at least 3000 red supergiants of
M_v_= -5 which are similar to those found in h and {chi}
Persei.
The brightest HII region is NGC 0604, in the northeast
quadrant. This has a linear diameter of about 320 parsecs.
Many smaller HII regions abound in the spiral arms.
Detailed, large-scale photographs of parts of M33 are
given as negative prints in Ap. J., 127, 513, 1958.
The integrated color index of the system is CI (Inter-
national) = 0.40 (Holmberg).

22. 1918PLicO..13....9C
Re:NGC 0598
Vol. VIII, Plate 3. A close rival to the Nebula of Andromeda as the most
beautiful spiral known. With its faintest extensions it covers an area at
least 55' x 40'. Messier 33 Trianguli. 588, 592, 595, and 603 are simply
brighter portions of 598. It is uncertain whether there is an actual stellar
nucleus. A multitude of stellar condensations in the whorls; the spiral
which furnishes the best known example of "resolution" into stars. 7 s.n.


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