8. 9. i0. II. 12. 13. 14. 15. 16.

ON

E. T. E. D. V D. E. E. R.

THE

E. F. E. W. N E. M. K. A.

Khachikyan, Astrofizika, 9, 139 (1973). Adams, Astrophys. J., 172, LIOI (1972). Khachikyan and D. W. Weedman, Astrofizika, 7, 389 (1971). Weedman, Astrophys. J., 171, 5 (1972). Popov, R. A Sarkisyan, and E. E Khachikyan, Astrofizika, 15 Osterbrock, Phys. Scr., 1__77,285 (1978). Burbidge and P. Strittmatter, Astrophys. J., 172, L37 (1972)~ Denisyuk and V. A. Afanas'ev, Astrofizika, 12, 665 (1976). Sramek and H. M. Tovmassian, Astrophys. J., 191, 633 (1974).

CONNECTION A.

R.

BETWEEN

SEYFERT

GALAXIES

AND

NEIGHBORING

189 ( ~ 9 ~ ) .

OBJECTS

Petrosyan

A sample of Seyfert galaxies containing 161 objects has been compiled. To consider the question of the connection between Seyfert galaxies and neighboring objects counts have been made of galaxies in circles of diameter 1.5 Mpc around fixed Seyfert galaxies. It is found that: i) the Seyfert galaxies participate in the clustering tendency of galaxies; 2) the type 2 Seyfert galaxies reveal a stronger tendency to participate in clustering of galaxies than the type I objects; 3) the type I Seyfert galaxies are more often isolated than the type 2 galaxies; 4) the type 2 Seyfert galaxies occur more often in isolated pairs of galaxies than the type I objects. The problem of the real and mathematically expected connection between Seyfert galaxies and Zwicky clusters has also been considered. It is found that: !) Seyfert galaxies exhibit a tendency to be found in Zwicky clusters; 2) Seyfert galaxies probably avoid compact clusters. They coincide with greater probability with clusters of mean compactness than with open clusters; 3) the type 2 Seyfert galaxies coincide more frequently with clusters than do the type 1 objects; 4) Seyfert galaxies that are probably members of Zwicky clusters have a tendency to be closer to the centers of concentration of galaxies in the clusters.

i. Introduction There is a belief that galaxies with emission lines in ~enera~~ [1-31 and Seyfert galaxies in particular [2-4] avoid rich clusters. Recently, Schmidt [5] published preliminary results that contradict this belief, namely, he found that the number of Sey~ert galaxies in clusters corresponds to the general increase in the number of galaxies in clusters. The number of known Seyfert galaxies now exceeds 150. consider in more detail the participation of Seyfert objects axies, which is the subject of the present paper. 2.

Sample of Seyfert

This makes it possible to in the clustering of gal-

Galaxies

Our sample c o n t a i n s o b j e c t s whose d e f i n i t i o n as S e y f e r t g a l a x i e s agrees with the standard definition (see, for example, [6]). We s e l e c t e d o n l y t h e S e y f e r t g a l a x i e s w h o s e i m a g e s o n t h e c h a r t s o f t h e P a l o m a r Sky S u r v e y h a v e d i a m e t e r s ~ 0 , 1 mm, d i f f e r i n g from star images. The s a m p l e d e f i n e d i n t h i s way c o n t a i n s 1 6 1 S e y f e r t galaxies (May, 1980). For brevity, we s h a l l d e n o t e t h e o b j e c t s o f t h i s s a m p l e b y SG. A b o u t 84% o f t h e s e objects occur in the lists of Markaryan Objects. D a t a on t h e S G ' s a r e t a k e n f r o m t h e original observations and the reviews [6, 7].

pp. for

312

Byurakan Astrophysical Observatory. Translated 548-562, October-December, 1982. Original article publication July 27, 1982.

0571-7132/82/1804-0312507.50

from Astrofizika, submitted January

9 1983 Plenum Publishing

Vol, 18, No~ 4 , 8, 1 9 8 2 ; accepted:

Corporation

I

o

r

I

I-

~

I

t

]

I "

I

[

I

1

t

~

I

t ~

]

]

"

~

-""

I

u

i11

I

I

m

,r-.i

m

313

3. M e t h o d Seyfert

of A n a l y z i n g

Galaxies

the C o n n e c t i o n

and N e i g h b o r i n g

between

Objects

To d e t e r m i n e w h e t h e r the SG's b e l o n g e d to the field or systems of various multiplicities we counted the g a l a x i e s around fixed SG's and c o m p a r e d the r e s u l t i n g n u m b e r s with the numbers of such objects in n e i g h b o r i n g sections of the sky. Since the systems of h i g h e s t m u l t i p l i c i t y w h o s e m e m b e r s could be Seyfert galaxies are clusters of galaxies, the counts around the fixed SG's were made w i t h i n circles with angular d i a m e t e r corresponding to fixed linear d i a m e t e r 1.5 Mpc, w h i c h is the mean for clusters [8] The counts were m a d e for each of the SG's on the blue charts of the P a l o m a r Sky Survey. In cal" c u l a t i n g the angular d i a m e t e r s of the circles, we assumed that H = 75 km, sec, l-Mpe7 ! As c r i t e r i o n of a p o s s i b l e c o n n e c t i o n b e t w e e n a SG and n e i g h b o r i n g galaxies a circle of d i a m e t e r 1.5 Mpc we took as a first a p p r o x i m a t i o n the r e l a t i o n s h i p 0.5 a s ~ <

in

a i < 2asG

(I)

b e t w e e n their angular diameters, where the subscripts SG and i refer to the fixed SG and the n e i g h b o r i n g galaxies, r e s p e c t i v e l y . In other words, galaxy i is r e g a r d e d as "physically" c o n n e c t e d to the SG if its angular d i a m e t e r is w i t h i n the range given by (I) For comparison, we also made counts of galaxies in sections of the sky near the SG's in circles of the same d i a m e t e r as for the c o r r e s p o n d i n g SG. To d e c r e a s e the in, fluence of r a n d o m errors, the counts in the c o m p a r i s o n circles w e r e made in four positions -- to the north, south, east, and west of the SG -- and the centers of tlie c o m p a r i s o n circles were taken at a d i s t a n c e of two--five diameters from the c o r r e s p o n d i n g SG~ 4. R e s u l t s

of the Counts

The results of the counts of the galaxies w i t h i n each circle around the SG's are g i v e n in Table i. This contains s u c c e s s i v e l y the d e s i g n a t i o n of the SG, the n u m b e r of galaxies t o g e t h e r w i t h the SG s a t i s f y i n g the c r i t e r i o n (i) in a circle of diameter !~ Mpc around the SG (NSG) , and the real n u m b e r of n e i g h b o r s of the SG, c a l c u l a t e d as NSG -- Nc. c with the m e a n d e v i a t i o n (g) of the a r i t h m e t i c mean of the n u m b e r of g~laxies in the four c o m p a r i s o n circles. U s i n g the data in the third column of Table I, we c a l c u l a t e d the n u m b e r of all cases of the o c c u r r e n c e of the real number of n e i g h b o r s in d i f f e r e n t intervals of ~ for the c o m p l e t e sample of SG's; for type 1 SG's; for type 2 SG's, and for i n t e r m e d i a t e types. The o b t a i n e d data are given in Table 2, in w h i c h we also give the rati0s of the n u m b e r s of SG's of the first and second type to the t o t a l n u m b e r of SG's and~ in the last row, the total n u m b e r of SG's of the first, second, and i n t e r m e d i a t e types, and also the number of n o n e l a s s i f i e d SG's. Note that the c l a s s i f i c a t i o n of the SG's is b a s e d on the r e l a t i v e w i d t h s of the e m i s s i o n lines [9, i0]. F r o m the sample of SG's, we s e p a r a t e d the i s o l a t e d SG~s and the SG~s that are c o m p o n e n t s of i s o l a t e d pairs of galaxies. This was done, first, by means of catalogs of i s o l a t e d g a l a x i e s [II] and i s o l a t e d pairs of galaxies [12] and~ second, by an in, dependent s e p a r a t i o n of the SG's that s a t i s f y the c r i t e r i a o f i s o l a t i o n i n t r o d u c e d in [II] or the c r i t e r i a for b e l o n g i n g to an i s o l a t e d pair i n t r o d u c e d in [12] b u t were not

TABLE 2

(NaG--No. c)";-'--3~' - - 3 ~ < ( N s G - N c . c) ~<--~ -- z<(NsG--Nc, c.)~
< (NsG--Nc. c)<3= 3z < (NsG--Nc. c) Total

314

Ntot

NSGI

6

4

19

17

NaG2INs~.!N.o -2

q

-N~

2

--

--

20

1

3

51

27

40

22

16

I

1

45

22

22

1

--

16,

92160

3

6

I

I

NSG2 NaG

0.67

0

0.89

0,11

0.53

0.39

0.55

9.40

0.49

0.49

considered in [Ii, 12], mainly because either they or their neighbors did not occur in the catalog [13-16]. We note that the criteria of isolation and the criteria for belonging to an isolated pair introduced in [ii, 12] were intended for objects brighter than 15~7. The use of the same criteria for objects whose magnitudes have not been determined but are not fainter than 17 m leads to an increase in the probability of finding spurious cases of isolation and isolated pairs of galaxies. We now give the designations of the identified isolated SG's and SG's in isolated pairs of galaxies. For the objects in [ii, 12] we also give in brackets their corresponding catalog numbers.

507,

Isolated SG's: Harkaryan 309 975*, 1044, NGC 6814, 1 Zw 1.

(993),

382 (214), 493 (719),

885

(745),

34, 50, 142,

Seyfert galaxies that are members of isolated pairs of galaxies: Markaryan 266 (388), 506 (510b), 744 (295a), 984 (29a), 1376 (419a), NGC 3227 (234b), NGC 4151 (324b), NGC 7469 (575a), III Zw 55 (93a), M a r k a r y a n 40, 477, 504, 595, 612, 860, 1152, 3C120. When the excess number of galaxies in the regions around the SG's exceeded 3q, we considered the distribution of the galaxies in the circles. We found that with almost equal p r o b a b i l i t y the SG could be a member of a compact group or a loose group, the classification of compact and loose groups being as in [17]. Some bright SG's have been put in definite groups of galaxies in [8, 18]. The following SG's are members of Turner and Gott's groups [18] (the numbers of the groups in [18] are given in the brackets): M a r k a r y a n 744 (44), 759 (57), 766 (53), NGC 3227 (21), NGC 3516 (32), NGC 4151 (52), NGC 4235 (57), NGC 5548 (851. It is interesting to note that two SG's -- M a r k a r y a n 759 (NGC 4152) and NGC 4235 in [18] -- are put in one group (No. 57) of galaxies. The difference between their radial velocities is 450 km/sec, while the tangential distance between them is large: 8.83 degrees of arc or 4.3 ~pc for H = 75 km. sec-l.Mpc -I. In [8], the following SG's are put in nearby groups of galaxies (the name of the group is given in the brackets): NGC 1068 (Cet I), NGC 3227 (the group of NGC 3190), NGC 4051 (CVn II), NGC 4151 (UMa Z), NGC 4235 (Virgo W). The occurrence of Seyfert galaxies in clusters of galaxies will be considered below. We note only that among all the SG's for which (NsG -- Nc. c) < 3q, only 28% coincide with Zwicky clusters, whereas for all the SG's for which (NsG -- Nc. c) > 3~ there is coincidence for 63%. To determine possible selection effects in the galaxy counts, we calculated the sample coefficients of correlation between the numbers of galaxies in the circles around the SG's, in the comparison circles, and the real neighbors of the SG's and between the quantities log zSG , m~ G, and log d~G. Note that the apparent photographic magnitudes of the SG's are mainly taken from [13-16]. In the remaining cases, we used the estimates of the apparent magnitudes from [I, 19-23]. The diameters of the galaxies were determined from the Palomar Sky Survey to an accuracy of 0.05 minutes of arc. We also calculated the confidence interval at the confidence level p = 0.05 for the sample N = 161 under the assumption that the true correlation coefficient is equal to zero (zero hypothesis). The values with constant confidence interval • are given in Table 3. As can be seen from Table 3, the number of real neighbors

of the SG's is weakly

TABLE 3

Ig zSG S Gm~ ] NSG

--0.180

0.052 --0.153

--0.087

0.170 --0.284

--0.196

*This galaxy satisfies Sky Survey.

lg d"SG

--0.166

0.174

the criteria of isolation only on the blue chart of the Palomar

315

TABLE 4

Seyfertgalaxy

zSG

I

Cluster Zwicky NO.

Mark.

I 69* 291 298 352 423 504 673 699 728 993 1066 1073 1133 NGC 1275

0.016 0.076 0.035 0.034 0.015 0.032 0.036 0.036 0.034 0.034 0.017 0.012 0.024 0.024 0.018

0107.5+3212 133%9+3030 1600.4+1925 1600.44-1925 0107.5+3212 1123.9+3541 1701.4+2830 1424.0+2613 1625.5+4006 1058.6,-51049 0107.5.+3212 0303.0+4125 0303.0~-4125 2335.5+2449 0303.0+4125

Population -I of cluster

Abell No.

ace. Zwicky Zclu~tel

Open

0 018 0 0762 o o~6 0 036 0 018 0 0339

Av. comp

0 0337 0~034

Av. eomp

1781 2151 2151 1257

2199 1142

0,03!2 0.036

426 426 2634 426

0.0183 0.0183

0.018

0.0307

0.0183

~V,. kin/see 600 60 3O0 600 900 570 690 600 840 600 300 1890 1710 2010 9O

*The value of the red shift of the cluster Zw 1339.9 + 3030 = A 1781

is taken from [27]

c o r r e l a t e d to log zSG , and there is a b a r e l y n o t i c e a b l e c o r r e l a t i o n w i t h m and log dsG. In o t h e r words, the i n c r e a s e in the red shift of the galaxies, t h e i r v i s u a l d e c r e a s e i n b r i g h t n e s s , and the d e c r e a s e in the a p p a r e n t d i a m e t e r s lead e q u a l l y to a loss of n e i g h b o r s of the SG's. This is a s e l e c t i o n effect. 5. Cases of C o i n c i d e n c e

of S e y f e r t G a l a x i e s w i t h C l u s t e r s

To study the q u e s t i o n of the real c o n n e c t i o n b e t w e e n SG's and clusters~ we u s e d the data on Z w i c k y c l u s t e r s g i v e n in the c a t a l o g [13-16], since t h e c o n t o u r lines of the c l u s t e r s in the c a t a l o g s i m p l i f y the p r o b l e m of e s t a b l i s h i n g w h e t h e r a p a r t i c u l a r SG b e l o n g s to a cluster. S i n c e the d i s t a n c e s are k n o w n for all the SG's, we c o n s i d e r not o n l y the q u e s t i o n of g e o m e t r i c a l c o i n c i d e n c e of the p o s i t i o n of the SG's w i t h a c l u s t e r but also the q u e s t i o n of c o i n c i d e n c e w i t h the d i s t a n c e class of the clusters. It s h o u l d be n o t e d that due to the r e s t r i c t i o n s in ~ (the c a t a l o g [13-16] c o n t a i n s o b j e c t s w i t h ~ ~ --4~ the c o i n c i d e n c e w i t h Z w i c k y c l u s t e r s was c o n s i d e r e d for o n l y 144 of the SG's in the c o m p l e t e sample. C o n s i d e r a t i o n of the c o i n c i d e n c e in p o s i t i o n and red shift of the SG's w i s h c l u s t e r s r e v e a l e d that of the 144 g a l a x i e s o n l y 54 could be m e m b e r s of Z w i c k y clusters. The r e m a i n i n g 90 o b j e c t s w e r e e i t h e r o u t s i d e the c o n t o u r lines of the c l u s t e r s or the d i s t a n c e s of the SG's did not agree w i t h the d i s t a n c e class of the cluster. D a t a On the 54 SG's that in a c c o r d a n c e w i t h the above can be m e m b e r s of Z w i c k y c l u s t e r s are g i v e n in T a b l e s 4-7. C a t a l o g s of c l u s t e r s of g a l a x i e s w i t h k n o w n red shifts were r e c e n t l y p u b l i s h e d in [24, 25]. On the b a s i s of these catalogs, one can c o n s i d e r w i t h m o r e c o n f i d e n c e the q u e s t i o n of w h e t h e r v a r i o u s SG's b e l o n g to clusters.

TABLE 5

316

S~yl'~,r't galaxy

zSG

Mark. 176 739 766 789

0.027 0.030 0.013 0.032

Zwicky No. i of c l u s t e r I Z e l u s t e r 1138.7,4-5650 ] 1142.1+2126 1217.5+2915 1327.3+1145

t

0.0342 0.0214 0.003 0.0223

"SYr (km/sec) 216o 2580

27oo 2910

TABLE 6 Si~yI't~i'l. gll I uxy

zs(i

Mark. 268 358 533

0.041 0.046 0.029

NI~. ]

Zwiclf, y C 1.HS[.I~I" ;

o1"

ZC I il:;I

I'l'

AV r ( kin/.scc.

1339.9+3030 1

0.0762

10560

0107.5+3212 1 2320.0~-0845

0.018 0.0134

8400

)

4680

B e c a u s e the v e l o c i t i e s of real m e m b e r s of a c l u s t e r of g a l a x i e s may d i f f e r f r o m the m e a n for the c l u s t e r b y as m u c h as 5000 k m / s e c (see, for: example, [26]), it is a s s u m e d that a SG is a c t u a l l y a m e m b e r of a c l u s t e r if the d i f f e r e n c e b e t w e e n the r a d i a l v e l o c i t y of the c l u s t e r and the SG is less than 2000 km/sec. S u c h cases are g i v e n in T a b l e 4, w h i c h c o n t a i n s the d e s i g n a t i o n of the SG, its red shift, the n u m b e r of the Z w i c k y cluster, the n u m b e r of the A b e l l c l u s t e r i d e n t i f i e d w i t h the g i v e n Z w i c k y cluster, the p o p u l a t i o n of the Z w i c k y cluster, the red s h i f t of the cluster, and the d i f f e r e n c e b e t w e e n the r a d i a l v e l o c i t i e s of the c l u s t e r and the galaxy. If the d i f f e r e n c e b e t w e e n the r a d i a l v e l o c i t i e s of the c l u s t e r and the SG lies in the r a n g e 2000 k m / s e c < AV r < 4000 km/sec, the m e m b e r s h i p of the SG to the c l u s t e r is q u e s t i o n e d . S u c h cases are c o l l e c t e d t o g e t h e r in T a b l e 5. If the d i f f e r e n c e b e t w e e n the radial v e l o c i t y of the c l u s t e r and the SG is greater than 4000 km/sec, it is p r o b a b l e that the SG c o i n c i d e s w i t h the c l u s t e r b e c a u s e of p r o j e c tion. A m o n g the cases we c o n s i d e r e d , t h r e e come u n d e r this category. T h e s e cases are g i v e n in T a b l e 6. In T a b l e 7, w e g i v e red s h i f t s of the c l u s t e r s

the c a s e s of are u n k n o w n .

coincidence

for w h i c h

the e x a c t

values

of the

We note also that in [27] the S e y f e r t g a l a x y M a r k a r y a n 106 is r e g a r d e d as a p r o b a b l e m e m b e r of the c l u s t e r A 7 8 4 (Zw 0 9 1 7 . 9 + 5508) a l t h o u g h it is 25 m i n u t e s of arc f r o m the c e n t e r of the c l u s t e r and is not s u r r o u n d e d by the c o n t o u r line c o r r e s p o n d i n g to the Z w i c k y c l u s t e r A 7 8 4 and, t h e r e f o r e , is not i n c l u d e d a m o n g the 54 g a l a x i e s disc u s s e d above.

TABLE

7

Suyfert galaxy Mark.

] ]

6 Zw 91 10 42 79 205 236 374 382 391 403 463 493 506 530 595

Zwicky No. of clustt}r

0642.0+7334 0133.4 6102 0733.4+6102 1058.6-54611 0739.8-54949 1230.3-]-7450 1302.2-56243 0628.9-55232 0745.5+4020 0836.3-]-4147 0941.7+2430 1354.0+1834 1552.5+3435 1722,8+3120 2316,5+0046 0240.6.-@0740

Suy]ert valaxy

Zwicky No. of cluster

Mark. 622 Zw 0801.3+3954 1353.2--F2508 662 1704.9+3056 700 0909.7-51814 704 1003.6+1443 715 716 1006.3--I-2320 1628.0--I-2438 883 0226.0-52600 1040 2256.8+2445 1127 0226,0-52600 1179 0248.0-51307 1187 Arak. 347 1202.2-1-2028 1020.1 -t--2046 NGC 3227 1112.7--7259 3516 1916.8-}-4855 6764 2259.6--50746 7469

317

TABLE 8

ClusLer type aec. to Zwicky

N o•

Open Av. compactness Compact All Zwicky clusters Field

random

cases [ observed

l

11.5-1-3.4 7.9!-2.8 o.6+_o.s 20.0___4.5 89.2~9.4

I ]

20 24

[

44 65

0

I

6. Expected Cases of Coincidence of Seyfert Galaxies with Clusters To determine the expected number of cases of coincidence of SG~s with clusters~ it is necessary to fix the volume of space occupied by them. First, we r e s t r i c t the space with respect to z, considering only objects with z ~< 0.050 (the "near" distance class according to Zwicky). Second, we consider a region of the sky d e t e r m i n e d by con~ ditions analogous to the conditions of [28] : h

=

~. '

and

h

3 0-~5.5, 6hO--18.hO, h

h

~=20.5--3.0,

]b"] >7 20 ~ .

__

o .j

4 -,~ ~ -~ 100, "

~ > -- 4 ~

The area of such a region is ~13000 square degrees.

Out of the sample of SG's, 109 objects are in this space. In accordance with the catalog [13-16], this space contains 236 "open" Zwicky clusters with a total area of 1370 square degrees, 185 clusters of "average compactness" with total area of 937 square degrees~ and 24 "compact" clusters with total area 69 square degrees. If it is assumed that the probability of independent appearance of a certain nu~bet of SG's on the total area of the clusters is determined by Poisson's iaw~ then the most probable outcome is that the random number of coincidences should be equal to ~he observed mean number of coincidences. On the basis of this we have compiled Table 8, in which we give the numbers of expected random coincidences and the observed coincidences of SG's with "near" Zwicky c l u s t e r s of different populations, with all clusters, a n d with the field, irrespective of the exact values of the radial velocities of any of these objects. 7. Discussion From the results of the counts ~f the galaxies in circles of diameter 1.5 Mpc around the SG's and in the comparison circles we can draw the following conclusions. I. The Seyfert galaxies participate in the tendency of galaxies to cluster. This can be seen, first, from Table 2, in which for more 50% of the SG's the n~mber of real neighbors exceeds ~. Second, w h e n the function Nc. c = f(NsG) is approximated by:a linear dependence, the slope angle o f the approximated line is found to be 36 ~ (the sample Correlation coefficient between Nc. c and NSG is r = 0.799 • 0.162). 2. 12 of the SG's

(7~ of the sample)

are isolated in accordance with the criterion

of [11]. 3. 17 of the SG's (11% of the sample) in accordance with the c r i t e r i a of [12].

are components

of isolated pairs of galaxies

4. i0 bright SG's are identified as belonging to nearby groups of galaxies [8~ 18]~ but it must be assumed that not only these but also the m a j o r i t y of o t h e r SG's for which the real number of neighbors is greater than u probably belong to groups of galaxies~ Comparing the number of real and expected random coincidences of SG~s with Zwicky clusters of various populations, with clusters generally~ and With the field (see Table 8), we can draw the followin~ conclusions.

318

1. The SG~s e x h i b i t a t e n d e n c y to o c c u r in Z w i c k y is also c h a r a c t e r i s t i c of the r e m a i n i n g g a l a x i e s .

galaxies,

which,

as is well known,

2. In [2, 3], it is c o n c l u d e d that S e y f e r t g a l a x i e s a v o i d c o m p a c t clusters. According to our data, this is not so o b v i o u s . It is n e c e s s a r y to m a k e a m o r e d e t a i l e d S t u d y of this q u e s t i o n w i t h a l l o w a n c e for the total n u m b e r of g a l a x i e s in c o m p a c t Z w i c k y clusters. 3. The SG's c o i n c i d e w i t h g r e a t e r p r o b a b i l i t y w i t h c l u s t e r s t h a n w i t h o p e n clusters.

of m e a n c o m p a c t n e s s

It is i n t e r e s t i n g to s t u d y the p o s i t i o n of the SG's r e l a t i v e to the c o n t o u r lines of the Z w i c k y clusters. We f o u n d that a m o n g the 54 SG's 27 are s i t u a t e d at the edges of the c l u s t e r s ( f u r t h e r t h a n 2/3 of the radius of the c i r c l e c e n t e r e d on the c o n c e n t r a t i o n of g a l a x i e s n e a r e s t the SG w i t h radius equal to the d i s t a n c e f r o m this c o n c e n t r a tion to the c o r r e s p o n d i n g s e c t i o n of the c o n t o u r line of the cluster), 12 SG's are n e a r the c e n t e r s of the c l u s t e r s (closer to the c e n t e r s of the c o n c e n t r a t i o n s of g a l a x i e s in the c l u s t e r t h a n 1/3 of the radius), and 15 o c c u p y i n t e r m e d i a t e p o s i t i o n s . If in a first a p p r o x i m a t i o n we assume that a SG can o c c u r w i t h equal p r o b a b i l i t y a n y w h e r e w i t h i n the c o n t o u r line of a cluster, then in the above r e g i o n s the e x p e c t e d n u m b e r of SG's m u s t be 30:6:18. The o b s e r v a t i o n s give the n u m b e r s 27:12:15. Thus, the SG's c o i n c i d e twice as o f t e n w i t h the c e n t e r s of c o n c e n t r a t i o n of g a l a x i e s in c l u s t e r s than one w o u l d expect in the case of u n i f o r m o c c u r r e n c e a n y w h e r e w i t h i n the clusters. S i n c e it is w e l l k n o w n that the r e m a i n i n g g a l a x i e s in the c l u s t e r s e x h i b i t a s i m i l a r tendency, it can, in all p r o b a b i l i t y , be a s s e r t e d that the d i s t r i b u t i o n of the SG's w i t h r e s p e c t to the d i s t a n c e s from the c e n t e r s of the c l u s t e r s does not d i f f e r from the c o r r e s p o n d i n g d i s t r i b u t i o n of the o t h e r g a l a x i e s (see [29]). This can be r e g a r d e d as an a d d i t i o n a l p r o o f of c o n n e c t i o n b e t w e e n SG's and clusters. Of the 161 g a l a x i e s in the s a m p l e of SG's, 92 are o b j e c t s of the first type, 60 o b j e c t s of the s e c o n d type, w h i l e three are o b j e c t s of the i n t e r m e d i a t e 1.5 type. Therefore, in the case of e q u a l l y p r o b a b l e a p p e a r a n c e of SG's of the first and s e c o n d types in s y s t e m s of g a l a x i e s of d i f f e r e n t m u l t i p l i c i t i e s the r a t i o of the n u m b e r s of SG's of the first and the s e c o n d type to the total n u m b e r of SG's in the sample s h o u l d be 0.57 and 0.37, r e s p e c t i v e l y . The values of the r a t i o s N S G I / N s G and N S G 2 / N s G g i v e n in the last two columns of T a b l e 2 s h o w how the n u m b e r of SG's of the first and s e c o n d types v a r i e s r e l a t i v e to the total n u m b e r of SG's as a f u n c t i o n of the g interval. It can be s e e n that SG's of the s e c o n d type have a s t r o n g e r t e n d e n c y to p a r t i c i p a t e in the c l u s t e r i n g of g a l a x i e s than the o b j e c t s of the first type. In the s a m p l e of SG's, the m e a n value of the red shift for o b j e c t s of the first type is 0 . 0 4 5 • 0 . 0 0 3 and for o b j e c t s of the s e c o n d 0 . 0 2 8 • 0.002. Thus, in the s a m p l e the SG's of the first type are on the average f u r t h e r away than those of the s e c o n d type, which, o b v i o u s l y , is due to the h i g h e r l u m i n o s i t y of the former. As we n o t e d above, there is w e a k s e l e c t i o n w i t h r e s p e c t to z in the c o u n t s of the g a l a x i e s w i t h i n the circles. T h e n the t e n d e n c y we h a v e n o t e d above for SG's of the s e c o n d type to c l u s t e r m o r e s t r o n g l y than those of the first is to some e x t e n t s t r e n g t h e n e d by the effect of s e l e c t i o n w i t h r e s p e c t to z. A m o n g the SG's that are m e m b e r s of i s o l a t e d pairs of galaxies, nine are o b j e c t s of the s e c o n d type and six are of the first (NSGI/NSG = 0.4, N S G 2 / N s G = 0.6). Therefore, SG's of the s e c o n d type o c c u r a l m o s t twice as o f t e n in i s o l a t e d pairs of g a l a x i e s than one w o u l d e x p e c t in the case of e q u a l l y p r o b a b l e o c c u r r e n c e of o b j e c t s of b o t h types in pairs. Of the 12 i s o l a t e d SG's, e i g h t are o b j e c t s of the first type, three are of the s e c o n d type, and t h e r e is one i n t e r m e d i a t e 1.5 type object ( N S G 1 / N s G = 0.67, N S G 2 / N s G = 0.25). This m e a n s that the actual n u m b e r of SG's of the first type that are i s o l a t e d is 1.8 times g r e a t e r t h a n w o u l d be the case for e q u a l p r o b a b i l i t y w i t h SG's of the s e c o n d type for o c c u r r e n c e as i s o l a t e d galaxies. Of the 54 SG's that c o i n c i d e w i t h clusters,

27 o b j e c t s

are of the first

type

319

and 26 of the second.* Therefore, for SG's that are probably members of clusters we have the ratios NSGI/NsG = 0.50 and NSG2/NsG = 0.48, i.e., SG's of the second type coincide 1.5 times more frequently with clusters than objects of the first type if the probability of coincidence with clusters for objects of both types is the same. Only for SG's that actually are members of clusters (Table 4), SG's of the second type exhibit coincidence with clusters about 2.3 times more often than objects of the first type. This conclusion confirms the preliminary analysis result of Schmidt [5]. 8. Conclusions Thus, we have found that: I. Seyfert

galaxies

participate

in the tendency

of galaxies

to clustering~

2. Seyfert galaxies, which exhibit a tendency to occur in Zwicky clusters, probably avoid compact clusters. They have a tendency to be nearer the centers of concentration of galaxies in clusters. 3. Seyfert second type.

galaxies

of the first type are more often isolated

than those of the

4. Seyfert galaxies of the second type occur more often in isolated pairs of galaxies than those of the first type. objects

5. Seyfert galaxies of the second type more often coincide with clusters of the first type.

than

The last three conclusions confirm the result obtained above, namely, that Seyfert galaxies of the second type generally have a stronger tendency to participate in clustering of galaxies than objects of the first type. I should like to thank the referee

for helpful

LITERATURE i. 2. 3. 4. 5. 6. 7. 8. 9. I0. ii. 12. 13. 14. 15. 16.

17.

comments. %

CITED

B. E. Markaryan, Astrofizika, 3, 55 (1967). B. V. Komberg, Preprint No. 274 [in Russian], Institute of Cosmic Research (i976) o G. R. Gisler, M. N., 183, 633 (1978). S. van den Bergh, Astrophys. J., 198, L1 (1975). K.-H. Schmidt, in: The Large Scale Structure of the Universe (IAU S y m p o s i ~ No. 791 (ads. M. S. Longair and J. Einasto), Dordrecht (1978). D. W. Weedman, Ann. Rev. Astron. Astrophys., 15, 69 (1977). D. W. Weedman, M. N., 184, lIP (1978). G. de Vaueouleurs, in: Stars and Stellar Systems, Vol. 9 (eds. A. Sandage, ~.~. Sandage, J. Kristian), Univ. of Chicago Press, Chicago (1975), p. 557. D. W. Weedman, Astrophys. J., 159, 405 (1976). E. Ye. Khachikian and D. Weedman, Astrofizika, 7, 389 (1971). V. E. Karachentseva, Soobshch. SAO AN SSSR, No. 8, 3 (1973) o I. D. Karachentsev, Soobshch. SAO AN SSSR, No. 7, 3 (1972). F. Zwicky, E. Herzog, and P. Wild, Catalog of Galaxies and of Clusters of Galaxies; Vol. I (1961). F. Zwicky and E. Herzog, Catalog of Galaxies and of Clusters of Galaxies~ Vols. 2, 3, 4 (1963, 1966, 1968). F. Zwicky, M. Karpowicz, and C. T. Kowal, Catalog of Galaxies and of Clusters of Galaxies, Vol. 5 (1965). F. Zwieky and C. T. Kowal, Catalog of Galaxies and of Clusters of Galaxies, Vol. 6 (1968). H. J . Rood, A s t r o p h y s . J . , 188, 451 ( 1 9 7 4 ) .

*All objects coincident with the clusters were taken into account, since, first~ the r e d shifts of the clusters require confirmation, and, second, among the remaining: supernovae for which the question of membership to a definite cluster was not considered cases of : optical projection onto a cluster are also probable. %After the paper had been sent to press, we were acquainted with the note [30] of Arakelyan a n d Terebizh. The table given in [30] contains similar data for some of the Seyfert~galaxles included in Table 4 of the present paper.

320

and

18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30.

ON

E. L. Turner and J. R. Gott III, Astrophys. J. Suppl. Ser., 32, 409 (1976). B. E. Markaryan, Astrofizika, 5, 443, 581 (1969). B. E. Markaryan and V. A. Lipovetskii, Astrofizika, Z, 571 (1971); 8, 155 (1972); 9, 487 (1973); i__00, 307 (1974); i__22, 389, 657 (1976). B. E. Markaryan, V. A. Lipovetskii, and Dzh. A. Stepanyan, Astrofizika, I__33, 225, 397 (1977); 15, 201 (1979). G. de Vaucouleurs, A. de Vaucouleurs, and M. Corwin, Second Reference Catalog of Bright Galaxies, Austin (1976). S. W. Prata, P. A. S. P., 78, 61 (1966). T. W. Noonan, Astrophys. J. Suppl. Ser., 45, 613 (1981). T. S. Fetisova, Astron. Zh., 58, 1137 (1981). S. A. Gregory, Astrophys. J., 199, 1 (1975). H. G. Corwin (Jr), Astron. J., 7__99, 1356 (1974). V. Yu. Terebizh, Astrofizika, 16, 45 (1980). M. A. Arakelyan and V. Yu. Terebizh, Pis'ma Astron. Zh., 8, 139 (1982). M. A. Arakelyan and V. Yu. Terebizh, Astron. Tsirk., No. 1188, 1 (1981).

TIIE FREQUENCY R.

G.

OF

SUPERNOVA

FLARES

IN

Sc

GALAXIES

Mnatsakanyan

The mean frequency of supernova explosions in Sc by a method used to calculate the mean frequency stars in star aggregates [i0-ii]. The mean time successive supernova explosions in one Sc galaxy 48 years. It has not been possible to find clear quency of supernova explosions on the luminosity for the considered group of galaxies.

galaxies is determined of flares of flare interval between two brighter than 12mo is dependence of the freof the parent galaxy

i. I n t r o d u c t i o n S u p e r n o v a e x p l o s i o n s are the m o s t r a p i d and, at the same time, a m o n g the o p t i c a l l y o b s e r v e d c h a n g e s in distant galaxies.

striking processes

The d e t e r m i n a t i o n of the m e a n f r e q u e n c y of s u p e r n o v a e is one of the most c o m m o n d i r e c t i o n s of i n v e s t i g a t i o n . However, the results of such i n v e s t i g a t i o n s are very c o n t r a d i c t o r y [1-6] and we are far f r o m a w e l l - f o u n d e d and d e f i n i t i v e solution. Ever more p u b l i c a t i o n s c o n t a i n p r o p o s a l s for v a r i o u s m e t h o d s of d e t e r m i n i n g the m e a n f r e q u e n c y of s u p e r n o v a e [7-9]. In the p r e s e n t paper, to d e t e r m i n e the m e a n f r e q u e n c y of s u p e r n o v a e we use the m e t h o d s e m p l o y e d to d e t e r m i n e the m e a n f r e q u e n c y of flares of flare stars in s t a r a g g r e g a t e s (see, for example, [i0, ii]. S u p e r n o v a e x p l o s i o n s in d i f f e r e n t g a l a x i e s are random, m u t u a l l y i n d e p e n d e n t phenomena. S u c c e s s i v e s u p e r n o v a e in one g a l a x y are also i n d e p e n d e n t p h e n o m e n a . This f o l l o w s f r o m the fact that w h e n m o r e than one s u p e r n o v a is o b s e r v e d in a p a r t i c u l a r g a l a x y they are s i t u a t e d far f r o m e a c h other. It is t h e r e f o r e to be e x p e c t e d that the s u c c e s s i o n of s u p e r n o v a e in one g a l a x y can be r e p r e s e n t e d , at least o v e r a time up to one m i l l i o n years, as a s e q u e n c e of r a n d o m e v e n t s s a t i s f y i n g P o i s s o n ' s law. On the o t h e r hand, there are v e r y few g a l a x i e s in w h i c h s e v e r a l s u p e r n o v a e h a v e been observed. But the d e t e r m i n a t i o n of the m e a n f r e q u e n c y of s u p e r n o v a e , i.e., the v a l u e of the p a r a m e t e r that o c c u r s in P o i s s o n ' s law, f r o m o b s e r v a t i o n s of i n d i v i d u a l g a l a x i e s r e q u i r e s the d e t e c t i o n of not f o u r or five s u p e r n o v a e but at least s e v e r a l tens of t h e m in one galaxy, for w h i c h t h o u s a n d s of years of o b s e r v a t i o n s are needed. It is t h e r e f o r e v i r t u a l l y i m p o s s i b l e to a t t a c k the p r o b l e m of d e t e r m i n i n g the s u p e r n o v a Byurakan Astrophysical Observatory. T r a n s l a t e d from A s t r o f i z i k a , Vol. 18, No. pp. 563-573, O c t o b e r - D e c e m b e r , 1982. O r i g i n a l a r t i c l e s u b m i t t e d F e b r u a r y 5, 1982; a c c e p t e d for p u b l i c a t i o n J u l y 27, 1982.

0571-7132/82/1804-0321507.50

9 1983 P l e n u m P u b l i s h i n g C o r p o r a t i o n

4,

321