Copyright 2019-2026 Caltech, Support from NASA is acknowledged. This information is taken from a collection created and curated by the NASA/IPAC Extragalactic Database (NED), operated by the California Institute of Technology (Caltech). If your research benefits from the use of NED, the following acknowledgement in your paper would be appreciated: "This research has made use of the NASA/IPAC Extragalactic Database (NED), which is funded by the National Aeronautics and Space Administration and operated by the California Institute of Technology." See: https://ned.ipac.caltech.edu/Documents/Overview/Acknowledgments A row number applicable to this list only Bibliographic reference code Object name in NED standard format Note about the object, as transcribed from the referenced catalog or publication

1	2009MNRAS.397.2148G	MESSIER 031	NGC 224, better known as Andromeda, has not been included because the nucleus is not a pressure-supported star cluster in which the stars have random motions but is a rotationally supported nuclear disc.
2	2008MNRAS.386.2242H	NGC 0224	NGC 224 (M31), NGC 3031 (M81) and NGC 3115 in our sample are typical classical bulges listed in KK04.
3	2008MNRAS.386.2242H	NGC 0224	NGC 224 (M31), NGC 3031 (M81) and NGC 3115 in our sample are typical classical bulges listed in KK04.
4	2007MNRAS.382.1552L	NGC 0224	NGC 224 - M 31: The M31 nucleus is highly compact, and is the prototype of the central luminous star clusters found in many galaxies. The bulk of its stellar population corresponds to an old (>~10 Gyr) metal-rich component (Bica et al. 1990). This is also reproduced by our synthesis analysis. The central 1 kpc of M 31 contains several ionized gas clouds, which interestingly have different line ratios, placing them in the Seyfert, LINER or star-forming regions of line ratio diagrams (delBurgo et al. 2000).
5	2002ApJ...574..740T	MESSIER 031	M31. The modeling is complicated by the double nucleus. Kormendy & Bender (1999) find M_BH_ = (3.0 +/- 1.5) x 10^7^ M_sun_, although this result relies heavily on the small displacement between the center of light of the nucleus and bulge. Tremaine (1995) and Bacon et al. (2001) find M ~ 7 x 10^7^ M_sun_ but without detailed model fitting. We adopt the range (2.0-8.5) x 10^7^ M_sun_.
6	2002AJ....124..675C	UGC 00454	M31. The 1.4 GHz flux density is from the NRAO 91 m telescope (Dennison et al. 1975).
7	2001ApJS..132..129M	NGC 0224	Outside the bulge, the MUV light profile roughly parallels the R-band profile. However, the FUV profile flattens and even rises slightly with increasing radius, meaning that the (FUV-MUV) color becomes systematically bluer with radius. This result is preliminary because of the difficulty in determining the sky background (see section 4). The existence of a smooth radial distribution of FUV emission at small radii suggests the presence of an FUV-bright inner disk which spatially overlaps with the outer bulge. Such an inner disk is not seen in the case of M81 (NGC 3031, see Fig. 17a), where the combined FUV light of the bulge and disk is undetectable at inner radii (r < 3.5' = ~3.5 kpc). The surface brightness profiles are quite different between these two objects, despite the fact that M81 is only slightly earlier in Hubble type (Sab rather than Sb). The outer disk of M31 is rich in UV-bright massive stars, the brightest concentration of which is NGC 206, located ~5' from the southwestern edge of the mosaics shown in Figures 5a-5b. Hill et al. (1992a) provide UV photometry of 30 resolved stars in NGC 206; most are evolved OB stars with 30 <~ M/M_sun_ <~ 60. Hill et al. (1993c, 1995b) presented enlargements of the UIT images for some 60 OB associations in M31 and photometered individual stars and integrated light. They infer a maximum stellar mass of 85 M_sun_. Only about 40% of the integrated MUV light and 20% of the FUV light of a typical association comes directly from the resolved stars; the remainder may be dust-scattered starlight with a smaller contribution from fainter stars with T >~ 10,000 K. Bohlin et al. (1993) obtained UV photometry for 43 compact clusters; most of these are old globulars, but seven appear to be compact young clusters. The disk shows a strong (FUV-MUV) color gradient, becoming systematically bluer from r ~ 3' to r ~ 50' (~10 kpc) by about 2 mag. This reflects the increasing contribution of OB associations to the total integrated light at larger radii.
8	2001ApJS..132..129M	NGC 0224	NGC 224 (M31). - The Andromeda galaxy, a member of the Local Group, is a disk system, type SA(s)b, ~690 kpc in distance, and inclined 78^deg^ to our line of sight. Several low-resolution, wide field UV images of M31 were obtained with both balloon (Deharveng et al. 1980) and rocket experiments (Deharveng et al. 1976; Carruthers, Heckathorn, & Opal 1978; Bohlin et al. 1985; Bohlin et al. 1988), the latter two in both FUV and MUV bands. The best of these images achieved a spatial resolution of ~15" and showed that the UV emission from M31 is dominated by the bulge and a broken ring of OB associations. UIT imagery was obtained in two overlapping fields during Astro-1; M31 completely fills the field of view in both. One field is centered on the bulge; the other is centered ~40' to the southwest along the major axis. Images in each filter have been combined and are displayed as mosaics in Figures 5a-5b. The radial UV surface brightness and color profiles plotted in Figures 5a-5b, respectively, are based on mean values within those segments of the elliptical apertures which lie within our mosaic. The profiles therefore reflect behavior only near the southwestern major axis for r < 50'. The R-band profile shown in Figures 5a5b was interpolated from the major axis profile data taken from Kent (1987). The bulge is extended in both FUV and MUV and displays a relatively smooth appearance; neither bright substructure nor dust lanes are evident. As in the case of M81, the bulge of M31 is considerably more prominent at longer wavelengths, though the contrast is not as extreme as in M81. In both FUV and MUV light, the inner bulge follows a reasonably good de Vaucouleurs r^0.25^ profile to r ~ 90". Except at very small radii where the spatial resolution of the data are mismatched, the bulge shows only a small color gradient in (25-R). However, the FUV light is more centrally concentrated, producing a strong radial color gradient in (FUV-MUV) for 0 <~ r <~ 150", in which the light gets redder with increasing radius. This behavior is typical of large spiral bulges and elliptical galaxies but is much larger in amplitude and is reversed in sense from gradients in the optical bands such as (B-V) or (V-K) (O'Connell et al. 1992; Ohl et al. 1998). There are no detected UV point sources in the bulge, even though individual stars as faint as B1 V (m(MUV) ~ 18.4) would be above the MUV threshold (O'Connell et al. 1992). If the FUV light from the bulge originated in recently formed massive stars with a normal initial mass function, there would be ~200 OB stars visible within r <~ 2'. Their absence supports the interpretation of the FUV light as originating from low-mass, post-giant branch stars (e.g., Greggio & Renzini 1990; O'Connell 1999). HST UV observations of the core of M31 have been presented by King et al. (1992); Bertola et al. (1995); King, Stanford, & Crane (1995); and Brown et al. (1998). At HST resolution, the nucleus of M31 is double, and the component coincident with the dynamical center has UV colors which are bluer than those of the background bulge and therefore may contain massive stars formed through stellar collisions (King et al. 1995; Lauer et al. 1998). The second, off-nuclear component has UV colors similar to the bulge. These sources are not resolved in the UIT photometry. Brown et al. (1998) have partially resolved the hot stellar population responsible for the FUV light in the central 14" x 14" using HST/FOC images. Color-magnitude diagrams of the resolved stars are consistent with objects that have evolved from the extreme horizontal branch.
9	2001A&A...374..394V	NGC 0224	NGC 224: The discrepancy observed along the NE axis between our data and those by Kormendy (1988) and by Dressler and Richstone (1988) may be the result of an incorrect sky subtraction in our data. An overestimation of the sky level due to the large size of the galaxy covering all the slit area may produce the higher {sigma}_*_ and shift in V_*_ we actually measure.
10	2000MNRAS.319...17L	NGC 0224	NGC 224 (M 31): No analysis of X-ray data for this galaxy has been done in this paper. Einstein and ROSAT HRI observations of M 31 have detected over 100 individual sources with luminosities 10^36^ <~ L_X_ <~ 10^38^ erg s^-1^ (Trinchieri & Fabbiano 1991; Primini, Forman & Jones 1993). The ROSAT PSPC, which is more sensitive than the HRI (but with worse spatial resolution), gives an upper limit for a diffuse component associated with the galactic bulge of 2.6 x 10^38^ erg s^-1^ (Supper et al. 1997). The point sources are associated with two components, the disc and the bulge, and are strongly concentrated towards the centre. PSPC data show that the bulge and disc components account for about one and two thirds of the total emission, respectively (Supper et al. 1997). Ginga (2-20 keV) and BeppoSAX (0.1-10 keV) observations have shown that this emission from the galaxy is consistent with a population of low-mass X-ray binaries (LMXRBs) (Makishima et al. 1989; Trinchieri et al. 1999). A list of the sources found within ~6 arcmin of the nucleus is shown in Table 6. The source coincident with the galactic nucleus has been reported to vary (Primini et al. 1993), and is probably an XRB.
11	1999A&AS..138..253B	NGC 0224	NGC 224 - SN 1885A: five small patches (<= 1 arcsec) have been detected. They all are red and bright (brighter than 20th V magnitude). The galaxy light might contaminate the environment.
12	1997AstL...23..644G	MESSIER 031	M 31. Van den Bergh (1992) (a recommendation that is based on an analysis of the studies of other authors); Berkhuijsen et al. (1988)(nos. 1583, 2621, 820), (nos. 4391, 4652, 4640). The brightest red stars were identified using the criteria (B-V> 1.8 and 0.8<(V-R)<1.2, and the brightest blue stars were identified using the criterion (U-B)<0.0. In Nedialkov et al. (1989), the brightest red stars (R4, R31, R36) and the brightest blue stars (nos. 79, 87, 27) are, respectively, 0.49^m^ and 1.90^m^ fainter. It should be noted that there are no sufficiently complete data in the literature on the brightest red and blue supergiants in M 31, and this is the least reliable case among our samples of the brightest stars.
13	1996ApJS..103...81C	NGC 0224	NGC 0224.--M31. Multiconfiguration mosaic of 1465 MHz VLA images in Braun (1990).
14	1994CAG1..B...0000S	NGC 0224	M31 Local Group SbI-II PS-0-Hendricks Hubble Atlas, p. 18 Sep 29/30, 1948 103aO 10 min The print of M31 here is made from the first plate taken with the Palomar 48-inch Schmidt telescope after the final optical adjustments had been made in 1948. The observer was Don 0. Hendricks, chief optician of the Mount Wilson Observatory and later the Mount Wilson and Palomar Observatories. Hendricks had made the optics of the 48-inch Schmidt, with its 72-inch primary mirror, in the optical shop in the Mount Wilson office complex between 1937 and 1941. The superior optics of this largest of the Schmidt telescopes (at the time) is well shown by the print here. The field of view is about 3^deg^ on the long side. A description of M31 itself, chief member of the Local Group, would be similar to that in the Hubble Atlas and is not repeated here.
15	1993ApJS...86....5K	NGC 0224	NGC 224 (M31, Andromeda); Sb. The UV spectrum of M 31 is basically concave, with a minimum in flux at around 2000 A and an increase in flux to both longer and shorter wavelengths. Absorption features of Si II, OI, Si III, and C II are present between 1200 and 1350A, as well as Mg II {lambda}2800 (both Galactic and from M 31) and Mg I {lambda}2850. M31 is the best example in the atlas of a spiral (Sb) galaxy with the center dominated by the bulge population (Burstein et al. 1988); the spectrum resembles that of an elliptical galaxy, but with a less prominent rising branch. Welsh (1982) observed the center of M 31 with IUE and concluded that the rising branch did not come from young, metal- rich stars because of the weak absorption features of Si IV and C IV near 1300 A. In the central region, Welsh also found that the blue stars are more centrally concentrated than are the metal-rich red giants, based on a comparison of the cross-dispersion profile in the UV with that in the optical. Deharveng et al. (1982) derived an upper limit for the star formation rate of 7.4 X 10^-5^ M_sun_ yr^-1^, by comparing the far-UV luminosity with the predictions of the steady state UV flux of Lequeux et al. (1981). The longer wavelength flux is presumably due to the main- sequence turnoff and is dominated by late F stars (see the stellar spectra in Fig. 5 for comparison).
16	1976RC2...C...0000d	NGC 0224	Globular Clusters: Ap. J., 171, 403, 1972. Molecular Absorption: (2.1 and 2.3 micron, H2O and CO) Ap. Lett., 14, 1, 1973. Polarization: Astrofizika, 4, 409, 1968. Dynamics, Rotation Curve, Mass Determination and M/L ratio: Ap. J., 142, 1376, 1965. Ap. J., 159, 379, 1970. Ap. J., 170, 25, 1971. Ap. J., 180, 605, 1973. Ap. J., 184, 735, 1973. Ap. J., 190, 283, 1974. Ap. J., 194, 257, 1974. IAU Symp. No. 38, 42-61, 1970. Tartu Obs. Publ. No. 26, 23, 1970. P.A.S.P., 86, 861, 1974. Mass Determination and Models: Astrofizika, 4, 364, 1968. Astrofizika, 5, 317, 1969. Astrofizika, 6, 149, 1970. Astrofizika, 6, 241, 1970. Kinematics: Tartu Obs. Publ. No. 36, 55, 1972. IAU Symp. No. 44, 37, 1972. HII Regions: Ap. J., 139, 1027, 1964. Ap. J., 159, 379, 1970. Ap. J., 163, 431, 1971. Ap. J., 179, 445, 1973. At 10 and 20 microns: Ap. J. (Letters), 193, L7, 1974. Radio Observations: IAU Symp. No. 60, 229, 1974. Interferometry: (H{Alpha}) Astr. Ap., 1, 208, 1969. IAU Symp. No. 60, 229, 1974. SN1885A: Search at 2695 Mhz, Bull. A.A.S., 5, 322, 1973. HI 21cm: A.N., 288, 19, 1964. A.J., 70, 669, 1965. Ap. J., 141, 750, 1965 Ap. J., 144, 639, 1966 Ap. J., 175, 347, 1972. Science, 153, 411, 1966. M.N.R.A.S., 133, 359, 1966 M.N.R.A.S., 149, 237, 1970 M.N.R.A.S., 165, 9P, 1963 M.N.R.A.S., 169, 607, 1974. Mem. R.A.S., 74, 43, 1970. Astrophys. Lett., 4, 47, 1969. IAU Symp. No. 44, 12, 1972. Astr. Ap. Suppl., 12, No. 12, 1973. Astr. Ap., 30, 353, 1974. Companion at 1.5 degrees, IAU Symp. No. 58, 122, 1974. Radio Observations: Ann. Ap., 26, 343, 1963. Nature, 198, 844, 1963 Nature, 202, 269, 1964 Nature, 202, 1202, 1964 Nature, 207, 587, 1965 Nature, 214, 1190, 1967. A.J., 69, 374, 1964 A.J., 70, 324, 1965. A.J., 72, 809, 1967 A.J., 77, 637, 1972. Science, 145, 389, 1964 Science, 156, 1087, 1967. Observatory, 85, 24, 1965. Ap. J., 142, 1333, 1965. Bull. A.A.S., 3, 445, 1971. Bull. A.A.S., 5, 29, 1973. Astr. Ap., 34, 173, 1974. X-Rays: Ap. J., 179, 375, 1973 Ap. J., 190, 285, 1974.
17	1976RC2...C...0000d	NGC 0224	= Messier 031 Brightest in M31 (Local) Group. Faint companions: Ap. J. (Letters), 171, L31, 1972. Andromeda I = A0043+37 Andromeda II = A0113+33 Andromeda III = A0032+36 Andromeda IV = A0039+40 Photograph: Ap. J., 139, 1056, 1964. P.A.S.P., 78, 367, 1966. P.A.S.P., 78, 496, 1966. A.J., 72, 65, 1967. Astr. Ap., 9, 181, 1970. Astrophys. Lett., 11, 173, 1972. Ap. J. (Letters), 174, L71, 1972. Ap. J., 179, 445, 1973. Nucleus: Ap. J., 140, 1467, 1964. Ap. J., 170, 25, 1971. Ap. J., 194, 257, 1974. "Nuclei of Galaxies", 271, 1971. IAU Symp. No.58, 336, 1974. Photometry: (UBV) Ap. J., 142, 1376, 1965. Ap. J., 143, 187, 1966. Ap. J., 157, 55, 1969. Ap. J., 194, 257, 1974. A.J., 71, 867, 1966. Astr. Ap., 12, 1, 1971. Bull. A.A.S., 4, 332, 1972. Photometry: (12 Color) Ap. J., 146, 36, 1966. Photometry: (5 Color) A.J., 73, 313, 1968. Photometry: (10 Color) Ap. J., 179, 731, 1973. Photographic Isophotometry: P.A.S.P., 82, 1032, 1970. Photometry: (I.R. 1-25 microns) Ap. J., 138, 1317, 1963. Ap. J., 143, 187, 1966. Ap. J. (Letters), 159, L165, 1970. Bull. A.A.S., 1, 248, 1969. Absorption and Color Excess: A.J., 72, 526, 1967. A.J., 74, 1000, 1969. Astr. Ap., 24, 47, 1973. Resolution and Distance Modulus: A.J., 72, 526, 1967. A.J., 72, 65, 69, 1967. OB stars: Ap. J. Suppl., 9, No. 86, 1964. A.J., 71, 219, 1966. IAU Symp. No. 38, 39, 1970. A.N., 292, 103, 1970. A.N., 292, 275, 1971. A.N., 294, 79, 1972. Variable Stars: (Novae, Cepheids) IAU Circ. No. 1878, 1964. A.J., 69, 610, 1964. A.J., 70, 212, 1965. A.J., 72, 1356, 1967. Coll. Int. C.N.R.S., Paris, 125, 1965. Ast. Tsirk., No. 560, 1970. Ast. Tsirk., No. 579, 1970. Sov. A.J., 12, 265, 1968. Sov. A.J., 15, 1001, 1972. Info. Bull. Var. Stars., No. 622, 1972. Ast. Tsirk., No. 799, 1973. Astr. Ap., 22, 453, 1973. Astr. Ap. Suppl., 9, No. 3, 1973. Distance Modulus: (From Cepheids) Sov. A.J., 7, 293, 1963. Bull. A.A.S., 3, 398, 1971. Globular Clusters: Vet. Publ. Astr. Inst. Univ. Brno., No. 5, 1966. Bull. A.A.S., 1, 208, 1969. J.R.A.S. Canada, 63, 95, 1969. Ap. J.Suppl., 19, No. 171, 1969. Sov. A.J., 12, 116, 1968. 17, 174, 1973. Spectrum, Description and Photograph: A.J., 74, 515, 1968. Internal Motions: IAU Symp. No. 29, 71, 1968. Ap. J., 159, 379, 1970. Ap. J., 181, 61, 1973. Velocity Dispersion: IAU Symp. No.15, 112, 1962. Bull. A.A.S., 4, 315, 1972. Ap. J., 180, 705, 1973. IAU Symp. No. 58, 20, 1974. Redshifts of Faint Background Objects: Sov. A.J., 18, 144, 1974. Spectrophotometry: Ap. J., 139, 532, 1964. Ap. J., 141, 109, 1965. Ap. J., 154, 21, 1968. Ap. J., 163, 249, 1971. Ap. J., 164, 11, 1971. Ap. J., 170, 25, 1971. Ap. J., 177, 31, 1972. A.J., 74, 150, 1969. P.A.S.P., 82, 760, 1970. IAU Symp. No. 44, 49, 1972. Wells, Don, Univ. Texas. Dissertation, Austin, 1972. Mem. S. A. Ital., 43, 263, 1972. Bull. A.A.S., 4, 230, 1972. Bull. A.A.S., 6, 442, 1974. Astr. Ap., 26, 95, 1973. Astr. Ap., 27, 433, 1973. IAU Symp. No. 58, 169, 1974. Spectrophotmetry (near UV): IAU Symp. No. 36, 130, 1970. Spectrophotmetry (far UV): P.A.S.P., 81, 475, 1969. N.A.S.A. SP 310, pp. 559-575, 1972. Population Models: P.A.S.P., 78, 380, 1966. Ap. J. Suppl., No. 193, 1971. Ap. J., 175, 649, 1972. Astr. Ap., 20, 361, 1972 Astr. Ap., 33, 177, 1974.
18	1973UGC...C...0000N	UGC 00454	The Andromeda Nebula, brightest in Local Group SA(s)b (de Vaucouleurs), Sb- (Holmberg) Companions UGC 00426 = NGC 205 at 37, 314 and UGC 00452 = NGC 221 at 24, 181 SN 1885 Possible SN 1664b (?), 1898 (probably nova), 1919 (probably nova)
19	1964RC1...C...0000d	NGC 0224	= Messier 031 Brightest galaxy in the M31 (Local) Group. Photograph: Ap. J., 76, 44, 1932. Ritchey, L'Evolution de L'Astrophotographie..., S.A.F., Paris, 1929. Monograph: Ap. J., 69, 103, 1929. (= MWC 376). Ap. J., 76, 44, 1932. (= MWC 452). Ap. J., 100, 137, 1944 (=MWC 696). Ap. J., 101, 179, 1945. Ap. J., 102, 377, 1945. Stockholm Ann., 19, No.2, 1956. P.A.S.P., 50, 99, 1938. Photometry: M.N.R.A.S., 74, 132, 1913. M.N.R.A.S., 87, 112, 1926. M.N.R.A.S., 94, 805, 1934. M.N.R.A.S., 97, 416, 1937. M.N.R.A.S., 110, 416, 1950. P.N.A.S., 20, 93, 1934. Publ. Michigan, VIII, No. 7, 103, 1941. Stockholm Ann., 13, 10, 1941. Stockholm Ann., 19, 2, 1956. Medd. Lund II, 128, 1950. Medd. Lund II, 137, 1959. Ap. J., 50, 384, 1919. Ap. J., 83, 424, 1936. Ap. J., 108, 413, 1948. Ap. J., 128, 465, 1958. Ap. J., 133, 309, 1961. Zeit. fur Ap., 34, 137, 1954. Zeit. fur Ap., 56, 194, 1962. Izv. Pulkovo, 20, No. 156, 87, 1956. Sov. A.J., 32, 16, 1955. L'Astronomie, 76, 359, 1962. Ap. J., 138, 1317, 1963. Orientation: P.A.S.P., 54, 72, 1942. Ap. J., 104, 220, 1946. Spectrum: Ap. J., 88, 605, 1938. Ap. J., 108, 415, 1948. Ap. J., 135, 725, 1962. P.A.S.P., 48, 17, 1936. P.A.S.P., 69, 293, 1957. P.A.S.P., 72, 76, 1960. Lick Obs. Bull., 19, 498, 41, 1939. A.J., 61, 97, 1956. Polarization: Stockholm Ann., 14, No.4, 1942. Bull. Abastumani, No.18, 15, 1955. Rotation and Mass: Ap. J., 55, 406, 1922. Ap. J., 95, 24, 1942. Ap. J., 97, 112, 1943. Ap. J., 136, 352, 1962. P.N.A.S., 4, 21, 1918. P.A.S.P., 50, 174, 1938. P.A.S.P., 53, 270, 1941. P.A.S.P., 72, 76, 1960. Lick Obs. Bull., 19, 498, 41, 1939. Zeit. fur Ap., 35, 159, 1954. B.A.N., 14, 17, 1957. A.J., 59, 273, 1954. HII Regions: Observatory, 79, 54, 1959. Zeit. fur Ap., 50, 168, 1960. SN 1885 Ap. J., 83, 245, 1936. Ap. J., 88, 289, 1938. Ap. J., 89, 141, 1939. HI Emission: B.A.N., 14, 1, 1957. Radio Emission: M.N.R.A.S., 110, 508, 1950. M.N.R.A.S., 111, 357, 1951. M.N.R.A.S., 119, 297, 1959. M.N.R.A.S., 121, 413, 1960. M.N.R.A.S., 122, 479, 1961. Nature, 174, 320, 1954. Nature, 175, 202, 1955. Nature, 180, 60, 1957. Nature, 183, 1251, 1959. Ap. J., 126, 585, 1957. A.J., 67, 580, 1962. A.J., 68, 70, 1963. A.J., 68, 274, 1963.
20	1961Hubbl.B...0000S	NGC 0224	MESSIER 031 Sb PS-0-H 48" Schmidt Sept. 29/30, 1948 103aO 10 min Enlarged 2.5X M31 is probably of the NGC 2841 type of multiple-arm galaxy although it differs from such type examples as NGC 0488, NGC 5055, and NGC 4699. The arms in M31 are thicker and less well defined than in these prototypes. Baade has made a long and careful study of M31, both of its geometric form and of its stellar content. A short description of part of this work is given by Baade in his report to the Rome Conference on Stellar Populations (vol. 5 of Ricerche Astronomiche, Specola Vaticana, 1958, pp. 3-21). Baade has noted seven distinct spiral arms in M31 (see Table 2 of his report). The inner two arms are dust arms; the outer five arms contain supergiant O and B stars. The first two arms cross the north-following half of the major axis at distances of 3.4 and 8.0 sec of arc from the center. These angles correspond to 1.5 mm and 3.6 mm from the center on the scale of the illustration. Both arms, designated as N1 and N2 by Baade, are within the burned-out central region of the illustration. The texture of the background luminosity of the central portion of M31 is smooth and amorphous on plates taken with small telescopes. Baade has shown, however, that this central region can be resolved into red stars whose color indices are about international 1.3 and whose absolute magnitudes are about Mv = -3.0 (Baade, Ap. J., 100, 79, 1944). The resolved images resemble those in NGC 0205, which is the E5 companion galaxy west of the center of M31. NGC 0205 is illustrated on page 3 of this Atlas. Dust lanes and dust patches are present in the central region of M31. Again, these are not visible on the illustration. But a negative print of lower intensity is reproduced by Hubble and Sandage in Ap. J., 118, 353, 1953 (Fig. 2). The dust arms and patches are similar to those in NGC 3031 (M81) shown on page 19 of this Atlas. The distance modulus of M31 is probably close to (m-M) = 24.6 (Th. Schmidt, Z. Astrophys., 41, 182, 1957; Sandage, Ap. J., 127, 513, 1958). The limiting photographic magnitude of the 48-inch Schmidt telescope is m(pg) = 21.1 (Abell, Ap. J., Suppl. Sec., III, 211, 1958). Therefore all resolved stars on this illustration are brighter than M(pg) = -3.5.
21	1961AJ.....66..541B	NGC 0224	1. Local Group Membership and velocities in the local group of galaxies have been discussed by Humason and Wahlquist (1955). Clearly the bulk of the mass of the group is contributed by NGC 224 and our Galaxy. Humason and Wahlquist pointed out that in using the virial theorem the numerical values are very sensitive to the value of the velocity of the center of the galaxy relative to the local group, which depends on the velocity of rotation of the sun relative to the center. Kahn and Woltjer (1959) used a value of 216 km/sec for the circular velocity of the sun and concluded that unless the volume of the group was filled with intergalactic matter to provide the large part of the total mass, the group would be unstable. Godfredson (1961) reanalyzed the same data and showed that for a circular velocity of 260 km/sec at the sun, the local group could be stable without intergalactic matter being present. Thus the result is inconclusive.
22	1956AJ.....61...97H	NGC 0224	HMS Note No. 006 Nucleus, drifted length of slit for all plates. HMS Note No. 007 On major axis, 14.0 arcmin south preceding nucleus. Absorption lines in unresolved nebulosity.
23	1918PLicO..13....9C	NGC 0224	The Great Nebula in Andromeda, Vol. VIII, Plate 1. This wonderful object, the largest of the spiral nebulae, is too well known to need description. Expo- sures of 1m to 3m on S23 show an almost stellar nucleus, with traces of spiral structure in the surrounding nebular matter. See Abs. Eff.