Classification and Morphology of External Galaxies. G. DE VAUCOULEURS. Introduction. The earliest systems of classification of "nebulae" by W. Herschel and others have been described by H. D. Curtis in his article of the "Handbuch der Astrophysik" [A]. The spiral form of some nebulae was first detected visually by Lord Rosse and his assistants between 1845 and 1850[2] and the appellation elliptical first used in a purely descriptive way was applied to non-spiral tub presumably external stellar systems by S. Alexander in 1852[3]. The great abundance of the spiral type was brought to light by the photographic surveys of the end of the XIX-th century. The spiral structure of the Andromeda nebula was detected photographically in 1888 by I. Roberts. These surveys also revealed the great abundance of smaller objects of the smooth, structureless elliptical type and the very elongated objects described as "spindles". In 1918 Curtis [9] isolated a special type of spiral, the so-called "\PHI" type, characterized by a diametral bar across the nucleus and a general ring-like structure; he also identified the "spindle" nebulae with a longitudinal dark lane as edgewise spirals with peripheral dark matter [10]. An early alphabetical classification of apparent shapes, introduced by M. Wolf [4], has been extensively used at Heidelberg by Reinmuth [62] and at Lund by Lundmark [44], Holmberg, Reiz, Danver and others [5]. Its relation to the standard classification has been given by Shapley and Ames [68]. For faint nebulae which show little or no structure, a descriptive classification, based on "concentration" and "elongation", introduced by Shapley[6] in 1929, has been in use at Harvard for some years; it bears little relation to the standard classification. Rather similar systems of morphological classification were introduced, about 30 years ago, by Hubble [25] and by Lundmark [43] with three main types, viz. elliptical, spiral (normal and barred) and irregular. This scheme, extensively used and later further developed by Hubble, has been accepted as standard up to the present time. l The main references are listed at the end of the chapter "General physical properties of external galaxies", p. 311. ~ Earl of Ross~: Phil. Trans. Roy. Soc. Lond. 1850; 1861. 3 S. AL~x~~~E~: Astronom. 1.2,95. 1M. Wo~~: Verhff. Kbnigstuhl-Heidelberg 3, Mr. 5 (Plate V). ~ See Ann. Lund Obs. 6(1937); 9(1941); 10(1942). ~ H. Sx~~L~~: Harvard Bull. No. 849. I. Classification. 1. Standard classification. This is the Mt. Wilson classification as used by Hubble between 1925 and 1935; it has been so often described [A, B, D] that only a short summary will suffice here. It is illustrated by Hubble's well known "tuning-fork" diagram (Fig. 1). a) Description of types. ~) Elliptical nebulae (E), range from circular or globular objects, such as NGC3379, to elongated, lenticular objects, such as NGC3115. As a rule they show no structural details, besides a small, bright and strongly condensed nucleus around which the textureless nebulosity decreases smoothly outwards in all directions to an indefinite edge where it fades into the general luminosity of the night sky. Sub-types are defined by the index n = 10(1 - b/a), if a, b are the apparent major and minor axes measured on photographs. The most strongly elongated objects, type E7, such as NGC3115, depart notably from a geometrical "ellipti-cal" shape, being pointed near the ends of the major axis. fl) Normal spirals (S) show the characteristic spiral arms when seen pole-on and, as a rule, a "spindle" shape with heavy absorption lanes of dark matter when seen edge-on. In the normal spirals the arms emerge tangentially from a bright central nucleus at opposite points on its indefinite edge and vanish after about one complete turn of the best fitting logarithmic spiral [12]; (cf. Sect. 6). In the more regular or classical examples only two main arms, very nearly symmetrical with respect to the nucleus, are present. In most cases, however, additional or secondary arms may exist and the spiral pattern is often far from regular. Sub-types, noted a, b, c, are defined by the relative importance of the nucleus (decreasing from a to c) and the degree of unwinding and resolution of the arms (increasing from a to c). According to Hubble [25]:" the arms appear to build up at the expense of the nuclear regions and unwind as they grow; in the end the arms are wide open and the nuclei inconspicuous. Early in the series the arms begin to break up into condensations, the resolution commencing in the outer re ions and working inwards until in the final stages it reaches the nucleus itself'' . 326). The resolution referred to is into blue supergiants and emis- sion objects characteristic of a Type I population. The gradual decrease of the axial ratio nucleus/spiral arms is best seen in edgewise systems (see Plate VIII), while face-on systems show more clearly the increasing resolution and irregularity from "early" types (Sa) to "late" types (Sc) (Plate V)1. Intermediate types: Hubble also introduced the notion of "lateral" extension or width of the classification sequence in its intermediate section, giving M 81 with "large nuclear region and thin, rather open arms" and M 94 "having smaller nuclear region with closely coiled arms" as extreme cases. This distinction has been little used in practice. Of more importance was the recognition of objects intermediate between normal and barred spirals, such as M83 and M61 which have been classified alternatively as Sc or SBc. Their intermediate characteristics first noticed by Hubble ([B], p. 46) and Lundmark [43], [44] have been discussed by Lindblad and Langebartel [41] Z. They more or less fill the gap between the two branches of the tuning-fork diagram. y) Barred spirals (SB), include the "pin-wheel" or "a-type" first described by Curtis [9]. In it a very bright central nucleus is crossed diametrically by a bar at the- extremities of which spiral arms start at right angles (in "late" sub-types) or tangentially from the rim of a continuous ring of which the bar is a diameter (in "early" sub-types). Additional or secondary arms may exist, but as a rule the symmetry of the pattern is more regular than in normal spirals (see Plate VI). Sub-types, noted a, b, c, are defined as for the normal spirals by the relative size of the nucleus and the degree of resolution and opening of the spiral structure. In Hubble's original system the ring, closed in the SBa and SBb sub-types, opens at SBc, producing the aspect sometimes described as "5-shaped" spirals. SB a objects observed under various angles give rise to singular "Saturn-like" shapes (Plate X). 5) Irregulars (I), were described originally by Hubble [25] as a class of objects "lacking both dominating nuclei and rotational symmetry" and of which "the Magellanic Clouds are the most conspicuous examples" ([25], p. 328). These wered termed more specifically "Magellanic nebulae" by Lundmark [43], [44]. However, the class was broadened by Hubble to include peculiar or chaotic objects which "do not find a place in the sequence of classification" since "the remaining irregulars might be arbitrarily placed in the regular se- quence as highly peculiar objects, rather than in a separate class ... Others, such as M82, are merely nondescript" ([B], p. 47). In fact the symbol I has often been used as almost equivalent to the sub- script p for "peculiar"; such an extension of the notation is both confusing and unwarranted. As a result the relation of "irregulars" to other sections of the classification sequence was not clear, some of them being clearly related to late-type spirals and others to early-type spirals b) Frequency of types. From 600 bright galaxies in the Lick and Mt. Wilson plate collections Hubble [25] found the following apparent relative frequencies: Frequency 17% 19% 25% 36% 2.5% ~ In accordance with establish custom, the words "early" and "late" are used in connec- tion with the position in the spiral sequence but have no temporal connotation. ~ See also in [38] a discussion by Lindblad of the batted spiral characteristics in the Andromeda nebula. Handbnch der Physik, Sd. LIZ]. 18a Hence the spirals constituted about 80% of the sample, with (St SB)/E = 4 or 5 and, further, a ratio S/SB=2 or 3. However, SHAPLEY and AMES' found that in the Coma-Virgo region for m <12 spirals comprise only 46% of the population and for m<14, 5=48%, E=47%,I=5%. These early statistics, although not necessarily inconsistent, were affected by selection effects arising from clustering and different interpretations of some nebular types not included in the standard classification. Frequencies based on revised types are given in Sect. 3c. 2. Revisions and additions. About 1935 Hubble undertook a systematic morphological study of the approximately 1000 brighter galaxies listed in the Shapley-Ames Catalogue, north of - 300 declination, with a view to refining his original classification scheme. This work begun with the 100-inch reflector and later continued with the 200-inch reflector was practically completed at the time Cf Hubble's death in 1953; his notes collected and organized by Sandage will be published in the near future with a collection of about 175 photographs illustrating the morphological features characterizing the various galaxy types. Through the courtesy of Dr. A. R. Sandage the main revisions introduced by Hubble to his system can be briefly described here. a) The most important addition was the introduction of the S0 and SB0 types regarded as transition stages between the ellipticals and spirals at the branching off point of the tuning-fork. S0 objects have the smooth appearance of ellipticals, but a luminosity distribution more like that of spirals, although no spiral arms are visible. They are characterized by a sharp, bright nucleus in the centre of a more or less uniform disc or "lens" having a rather sharp outer rim and surrounded by a faint, diffuse "envelope" with indefinite boundaries; the diameter of the lens in which dark crescents or rings of obscuring matter are often observed is usually about one- third of that of the envelope (see Plate III). There is apparently a continuous transition from "late" ellipticals, such as NGC4270, NGC4958, etc. and "early" S0's such as NGC3630, NGC4564, etc., then through various stages of the S0 sequence to the "earliest" regular spirals. HUBBLE distinguished two groups of SO objects: S0(1): smooth lens and envelope; early examples are NGC1201, NGC1332, and late examples NGC3065, NGC4684. S0 (2): some structure in the envelope in the form of a dark zone and ring; examples are NGC4459 and NGC4111, the latter seen edgewise. In edgewise objects the presence of rings manifests itself by the appearance of "ansae" simulating Saturn's ring, such as in NGC4215, NGC7332, etc. (Plate IX). The transition stage S0/a between S0 and Sa shows incipient spiral structure in the envelope. SB0 objects are characterized by a bar through the central lens, sometimes broad and hazy, sometimes narrow and sharp; the envelope may form faint outer rings, sometimes conspicuous, sometimes vague or imperceptible (Plate IV). Hubble distinguished three groups of SB0 objects: SB0(1): a bright lens, with broad, hazy bar and no ring, surrounded by a larger, fainter envelope, e.g. as in NGC3384, NGC4262, etc., some have circular envelopes, e.g. NGC4203. SB0(2): a broad, weak bar across a primary ring, with faint outer secondary rings, e.g. NGC2859. L H. Shapley and A. A~~s: Harvard Bull. 1926, No. 838, 3; 1930, No. 876, 39. the S·BO (3): well developed bar and ring pattern, with the bar stronger than ring, e.g. NGC4643, NGC5101. b) Many of the objects originally classified as S B a were then reclassified as SBo and the SBa sub-division had to be redefined as follows: SBa: smooth bar and lens, with poorly developed, closely coiled arms in envelope and either massive and structureless or filamentary and partially resolved. Hubble further distinguished two or three groups of barred spirals, one in which the arms extend from the rim of a ring crossed by a bar, e.g. NGC2217, NGC5566, NGC5701 (SBa), NGC ~~~~? NGC5950 (SBb), and one in which the arms start at the ends of the bar without ring, e.g. NGC2798, NGC4290, NGC7743 (SBa), NGC1300, NGC5430, NGC6951 (SBb). In another group still the ring is formed of closely coiled filamentary arms, e.g. NGC3185, NGC4037, NGC4385, NGC4389. This distinction remains well marked at the S B b stage, showing well developed, partially resolved arms going through more than one revolution, but there is no spiral structure in the lens; primary rings consist of spiral arms, secondary rings are seldom found. It was not followed up into the S Bc sub-division, characterized by wide open, well resolved spiral arms with absorption lanes and spiral structure in the lens, but no ring pattern. Sandage has also recognized two types of normal spirals, one in which the arms start at the rim of a ring structure, the other in which they start from a central nucleus. Some objects of the ringed type had previously been described by Shapley and P~~~sxEvoPoULos' as "plate spirals" and an investigation of ring structures was made by Randers [57]. There are further differences in the multiplicity of the spiral pattern, some objects showing only two main regular arms, others having a great many tightly coiled whorls. Reynolds had already pointed out2 that some spirals have "massive" arms, e.g. M31) M33, while others have "filamentary" arms, e.g. M81, M101. The importance of this distinction was acknowledged by Hubble [B] but could not be incorporated in the classification. c) An extension of the normal spiral sequence beyond the stage Sc was proposed by Shapley who used the notation Sd for objects such as NGC7793 (Plate V, 20), showing a very small, bright nucleus and many knotty irregular spiral arms. This notation could also, and perhaps more appropriately, be applied to highly disorganized and complex spirals of low surface brightness, such as NGC4395-4401 (see Plate VII). A parallel extension of the barred spiral sequence beyond the stage SBc was introduced by de Vaucouleurs 9 through the recognition of spiral structure in the Magellanic Clouds and objects of similar type, such as NGC1313 (Plate VI, 32), NGC4027, NGC4618, etc., which may be noted as SBd or SBm. Still "later" stages extending the spiral sequence into the irregulartypes may be represented by objects such as IC2574 or NGC2366, IC4662, etc. These objects are characterized by low surface brightness, high degree of resolution and sometimes outstanding emission nebulosities similar to 30 Doradus in the Large Cloud. They always show an abundance of blue supergiants and strong emission lines in their spectrum. L H. SHAPLEY and ]. s. P~~AsxEvopouLos: Proc. Nat. Acad. Sci. U.S.A. 26, 31 - 36 (1940) = Harvard Rep. 184. 2 J· H. R~~~oL~s: Observatory 50, 185 - 189 (1927); with comments by HUBBLE, Ob- servatory 50,276-281 and by Reynolds, Observatory 50,308. ~ G. de Vaucouleurs: Observatory 74, 23-31 (1954). - Astronom. J. 60, 126-140, 219-230(1955). An important characteristic of the group of irregulars related to the Magellanic type I(m) is their small diameter and low luminosity which marks them as dwarf galaxies. Typical objects of this group are NGC6822, IC1613, the Sextans system, the Wolf-Lundmark-Melotte nebula, etc.1 (Plate VII). In the poorest and smallest of them emission objects may be few or absent, but when their distance is small enough they are always well resolved into blue supergiants and giants. d) The existence of dwarf ellipticals (dE) of very low surface brightness was first brought to notice in 1938 through the discovery of the Fornax and Sculptor systems by Shapley 2· These are close enough to be resolved on blue plates at m ~~ 18; except for their very low density they seem to share all other population characteristics of normal ellipticals. Because of their very low surface brightness such systems are difficult to detect and might be much more abundant in space than their belated discovery suggests; nevertheless a special search for them on Harvard plates failed to disclose other examples. A few more "Sculptor type" systems have, however, been found since 1949 with the 48-inch Palomar Schmidt3. Dwarf galaxies of a possibly related type have been investigated in 1952 by Reaves [58] on plates of the Virgo cluster taken by C. D. Shane with the Lick 20-inch astrograph. These objects of which the brightest example in the Virgo cluster is IC3475 have the same smooth, circular or little elongated ap- pearance as the dwarf ellipticals and likewise show little central condensation. Hubble and Reaves suggested that they may be related to a group of dwarf spirals of low surface brightness exemplified by NGC3299 because their colour was at first thought to be blueish; however, recent observations indicate them to be reddish and this strengthens the similarity with the Sculptor-type systems. e) After all such additional types or variants have been weaned out, there remains a hard core of "irregular" or "peculiar" objects which do not seem to fit in any of the recognized types. One group of such objects consists of strongly interacting or colliding systems such as NGC1275, NGC4038-39, NGC5128, etc.4 which can often be identified by their distorted structure, abnormal spectrum and strong radio-emission; these systems are discussed in the article by B. Y. Mills. Double or multiple systems showing moderate interaction in the form of connecting links, distorted spiral arms or irregular filamentary extensions are discussed by F. Zwicxv. Only isolated galaxies or weakly interacting systems are considered in the present article. Even among them, however, there remains a small number o~ objects not clearly assignable to any of the previous types; one possible group, exemplified by NGC3034, NGC3077, etc. is characterized by an early-type spectrum (A, F) contrasting with a reddish colour (C ~~ 10.8), irregular absorption patches and filaments and a smooth, unresolved nebulous structure indicating an absence of blue supergiants and of discrete emission nebulosities (see Plate XI). Another possible group, exemplified by NGC5253~ is characterized by fairly strong emission lines and a complex structure unlike that of the Magellanic irregulars or late-type spirals. Still other puzzling objects such as Mayall's nebula [1], also show strong emission lines but have a fairly smooth structure a. l See F. HUBBLE: Astrophys. ]ourn. 62.409-433 (1925) = M.W.C. 304. - W. B~~D~: Astronom. Nachr. 234. 407(1929). - F. ZwicxY: Phys. Rev. 58. 478 (1940). - K. LUND- MARK: V.J.S. 68, 382 (1933) = Lund. Medd. (I), Nr. 135. ~ H. S~~p~EY: Bull. Harvard Coil. Obs. 1938, No. 908.- ~ R. G. HARRINGToN and A. G. W~~so~: Proc. Astr. Soc. Pacific 62,118-120(1950). - A. G. Wz~sori: Proc. Astr. Soc. Pacific 67, 27-29(1955). & See W. BAADE and R. M~~xowsxI: Astrophys. Journ. 119, 215-231 (1954). - F. Zwicx~: Ergebn. exakt. Naturw. 29. 344-385(1956). 5D. S.Ev~~s: Observatory 72,164-166(1952). ` R. T. S~I~H: Proc. Astr. Soc. Pacific 53, 1S7 (1941); also Astrophys. [ourn. 119. 225 (Fig. 14) (1954). ~ Some early-type spirals are known to show abnormally wide emission lines in the spectra of their nuclei, although the origin of such high random velocities (~ 5000 km/sec) is not 14, sB nlakc' up just o~'er fifty pc1rcent of tile sample, ellipticals and lenticulars close to a quarter each. The discrepancies between earlier statistics (cf. Sect. lb) may therefore have hinged mainly on whether the lenticulars were counted as ellipticals or spirals the ratio S/E changing correspondingly from 1/1 to 3/1. Note also that the ordinary spirals appear no longer more abundant than the barred spirals despite the inclusion of inter- mediate types (5A B) with the 5A group in the table. Table 1. Frey we ttcy of revised types. class/Family So 5A SB I Pcc Frequency(%) . . 23.4 21.0 24.4 26.3 3.4 1.5 Table 2. Frequency of sub-divisions. Type E E/SO So SO/a So Sob Sb Sbc Sc Scd Sd Sm Frequency 22.0 9.5 10.5 9.0 4.5 6.5 7.5 7.5 10.5 $.5 2.0 2.0 The detailed frequency in each of the sub-divisions along the regular classification sequence is given in Table 2, in which E/50 = E+, SO and 50/a = S0+, 5a'. A plot of the frequencies (Fig. 4) gives a fairly smooth curve indicating maxima at Sc and E separated by a minimum at 5a. The low apparent frequency of the Sd, S m stages is certainly due to a large extent to the low absolute luminosity and surface brightness of galaxies at these stages, but it is not yet possible to correct the apparent frequencies for such selection effects. On the other hand the high frequency of ellipticals cannot be due in general to an abnormally high absolute luminosity, so that it probably reflects the actual great abundance of this class'. `It should be emphasized that these provisional data based on a rather small sample of 200 objects are still subject to further revision; more definite and detailed results will eventually be forthcoming through the current reclassification of 1250 bright galaxies in the Shapley-Ames Catalogue. II. Morphology. a) Qualitative morphology. 4. Description of typical examples. The following eleven plates illustrate the revised classification system and will serve to support the description of the main morphological characteristics used as classification criteria. Since the revised three-dimensional classification recognizes at least 16 stages along the sequence from E to Im and 9 or more pure or mixed types at each stage across it (at least in the spiral sequences), a fully illustrated description, allowing also for tilt and orientation effects, would require several hundred examples. How- ever, the main criteria used to define the position of any normal galaxy along and across the classification volume can be illustrated with only a fraction of the total number of possible cases. Plates I and I I describe the main criteria used to distinguish between families and varieties in a central cross-section near the stage Sb. Plates III and IV illustrate the ellipticals and principal stages of the lenticular sequences. Plates V and VI illustrate the four main stages along each of the four principal sequences of ordinary and barred spirals. Plate VI I shows the (magellanic) irregular later stages of the spiral sequences. Plates VIII and IX illustrate the appearance of edgewise system of the lenticular, spiral and irregular classes. Plate X illustrates the effects of tilt and orientation on the appearance of SB(s)aor5B(r)aspirals. Plate XI shows some peculiar lenticulars and (non-magellanic) irregulars of the M 82 type. In order to minimize as far as possible the complications arising from diqfferences in scale and resolution, several sources of illustrations were used as follows: 1. Mt. Palomar 200-inch reflector (P 200") and 48-inch telescope (P 48"). 2. Mt. Wilson 100-inch and 60-inch reflectors (W 100"; W 60")'. 3. Mt. Stromlo 74-inch and 30-inch reflectors (S 74"; S 30"). 4. Isaac Roberts 20-inch reflector (IR 20") 2. For technical reasons all photographs are reproduced here as inverted negative prints, i.e. are mirror images of the objects as they appear on the sky, and the orientation with respect to the celestial coordinates is arbitrary. The classification criteria are described in relation to the three main parts of a galaxy defined by Hubble: a) the nucleus, i.e. the very small, very bright central condensation often sharply defined as the centre of symmetry of the structure; it is round in SA, elliptical in SB. b) the lens, smooth, bright and sharply defined in the lenticulars and early spirals, being crossed by the bar in SB and brighter at the edge in S(r). c) the envelope, generally faint and smooth with indefinite outer boundary in the lenticulars, brighter and occupied by the spiral arms in spirals. The outer (R) structure appears often in its outer parts near the stage 50/a. The distinction between these three regions is most definite near the middle of the classification sequence (S0/a) and vanishes at E and Im. `The Mt. \\ilson and Palomar photographs are reproductions from the "Hubble Memorial Volume" generously communicated in advance of publication by Dr. A.R. SANDA&E. ~ The Isaac Roberts photographs are from direct prints of the original plates, now stored at the Paris observatory and kindly made available some years ago by Prof. P. Couu~~c. The spirals of the ordinary family SA are above. of the barred family SB below; the ringed variety S(r) is to the right. the S-shaped variety S(s) to the left. The mixed types SAa(rs) are in the centre. There is a continuous transition between each type and only the main forms are illustrated; actual objects can occupy any intermediate position in the plane (volume). The main classification criteria are as follows: SA(r): has a small. sharp. very bright and round nucleus isolated in the centre of a circular ring at the edge of which emerge many tightly wound filamentary spiral arms or arcs; the nucleus and ring often merge and disappear in the over-exposed image of the central bulge (as illustrated). but the high multiplicity of the spiral pattern is usually sufficient for identification; a weak outer ring (R) made up of many closely coiled spiral arcs is often present in early stages of this sequence. Examples are NGC488 (illustrated from P 200"), NGC7217, NGC6753 (Plate V, 22); other examples: NGC4736 (M94) (Plate V. 21), Sub and NGC5055 (M63). Sbc. SA(rs): has a fairly small, fairly sharp. bright and round nucleus in the centre of a diffuse lens or bulge out of which two main arms and two or more additional. weaker arms emerge tangentially; the two main arms simulate an incomplete ring around the lens; weak outer arms simulate an (R) structure in the early stages. Examples are NGC1068 (M77) NGC3147, NGC4237. possibly NGC3521, NGC4800, NGC7079, NGC7590, NGC5194 (M51) (illustrated from IR 20") is not a very good example as it is more nearly Sbc and intermediate between SA(rs) and SA(s). SA(s): This is the typical. regular logarithnlic spiral; it has a fairly large, diffuse, round nucleus extending smoothly into the circular or little elongated lens which shows some spiral pattern of dark matter; two main spiral arms with occasional branching or weaker secondary arms start at the rim of the lens. Examples are NGC 3031 (M 81), Sub (illustrated from IR 20"), NGC4569, NGC7205 (Plate V. 18) NGC7331. One diameter of the lens is occasionally slightly brighter and longer and the outer arms may have a tendency to "return" to the lens. indicating a transition toward the 5AB (s) type; examples are NGC224 (M31). 5b and NGC4321 (M100), Sbc. SAB(s): Has a fairly small. bright. elongited nucleus crossed by a weak, twisted dark lane in the centre of a weak and broad bar marking the major axis of a faint. diffuse and elongated lens with much spiral pattern of d·irk matter having a tendency to run parallel to the bar. T~vo main arms emerge near the extremities of the bar along a smooth. curved path turning sharply just outside the lens; their faint extremities tend to return to the lens along an alniost circular outer loop. simiilating an ([?) structure in the early stages. Examples are NGE1566 (illustratec] from S 30"). NGC5236 (\I \3) Sbc, NGC4579. Sub and NGC7392. SB(s): This is the typical "5-shaped barred spiral; it has a small. very bright and elongtted nucleus distorted by a strong. twisted dark lane as it crosses over from one side to the other of the strong. narrow bar marking the major axis of a much elongated lens. Two strong. main arms start sharply at right angles to the bar at both ends and return faintly to it after completing a turn oi a cliiasi-circular loop. Examples are NGC1097, NGC1300, NGC1365 (i]liistratc'l from S 3o"). NGC5383. Later stages in tliis sc