Chin.Astron.Astrophys. Act,Astr~phys. Sin.
Pergamon
12 (1988) 304-310 _8 11988) 182-389
Press
plc.
Printed in Great Britain 0275..1062/‘88$10.00+.00
A SECT FORI~~~R~~ STELLAR OBJECTS IN VELA XIAO Zben and LI Jing Beijing Observatory, :lcademia
Keywords:
Sinica
Photcgraphic photometry infrared escess objects
- colours
of
stars
-
In a search for infrared excess objects near the galactic plane, a star field of 28.5 square degrees in Vela has been measured on UK Schmidt piates R4272 and 14183 with the Cosmos The magnitude limit is machine at Royal Observatory, Edinburgh. around 20 in R and around 19 in 1. 131 infrared excess objects with colour index R-I > 2.5 are discovered in the field, and 3 red stellar objects have been identified as the optical counterparts of IRA8 point sources. ABSTRACT
Received
1987 August
4
The tea-dimensional diqitised scannin:: measuring machine COS~fOS 121 of Royal Observatory-, Edinburgh was used to measure the UK Schmidt, R and I sky survey plates [3/ of galactic re ion so.261 in Bela. The _/ F” fii >Id is 3.33. x 3’3.~ . The plate centre is 1 = (1950.0 epoch): (X : 9h2Om, 6 = -l5 ‘00’; 269.0 b = +3.4>. The plate limit of plate R42’72 ts “20, that of plate I4138 is ~19. ‘The Harvard photoelectric sequence E4 in the
Vela region Id1 was used for brightness and COSMOS measures the colour calibration. brightness of star images in units of cosmag Least-squares fits between Cosmag R 151. and R and between Cosmag I and I for the E4 standards have mean errors ztO.06 mag and f0.07 mag, respectively. h’e used the VAX 11/780 computer of Beijing Observatory to count the star images in Cosma$ R and Cosmag I down to the plate
Coonas R
Fiq. 1 Differential counts of R images
number magnitude from plate H 42172
Fig. 2 counts
Differential of I images
number magnitude from plate I 4138
Infrared Objects
L’
..c....r....e
_-1OW
.
0
-1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5
I
Differentialnumber magnitude counts of colour R-I from paired :!.ates
TABLE 1 Relation Between the Two Colour Systems R-I
..L.....C
-SW
Comwj R-Comsp
Fig. 3
305
Cosmag r - Cosmag I -800.1 -691.3 -582.6 -473.8 -365.0 -256.2 - 47.5 - 38.7
limit. We counted 385,950 stars on the R4272 plate, and 349,661 on the I4138 plate. The distributions of counts are shown in Figs. 1 and 2, and we can take that the count down to Cosmag R w -1150 or Cosmag I * -850 are complete and reliable, [6]. The corresponding magnitudes are R N 20.2, I N 18.4. We used Starlink
catalogue treatment software to compare the R-I plate pair and find the magnitude difference, i.e., the R-I colour. For this, we first established the coordinate conversions between the two plates from 52 selected reference stars in 5 small regions within the Sky Region No.261. Since the position measurement by COSMOS gives the weighted density centre of the pixel elements in the star image, the position of the star on different colour plates may not be precisely coincident. We take an 8" x 8" error box as the criterion for position identificationon Schmidt survey plates. With this criterion, we determined the Cosmag R - Cosmag I
colours of the stars on our plate pair. The correspondencebetween the Cosmag R - Cosmag I colour and the R-I colour is given in TABLE 1. The frequency distribution of the colour index is shown in Fig. 3. We note that blue objects with R-I < -10 and extremely red objects with R-I > 2.5 are both very rare. According to the definitions in the internationalwide-band UBVRI photometric system, R-I = 0.0 for A0 stars and R-I q 1.0 for MO stars. Actual observations show that, for the latest types, e.g., M8, R-I m 2. Therefore, we shall take R-I t 2.5 as criterion for infrared excess objects. By this criterion, we discovered 131 infrared excess objects in this galactic region in Vela of 28.5 square degrees. Their equatorial coordinates were measured with the TV plate monitor of Beijing Observatory with a mean error of k2.0". TABLE 2 gives the measured positions and colour indicies of these 131 infrared excess objects. An examination of the IRAS catalogue of point sources yielded 336 sources in our region. According to our criterion, (6" x 8" error box), we have 3 identifications. These are the optical counterparts to IRAS point sources in this region. Their coordinates and identificationcharts are given in TABLE 3 and Figs. 4(l) and 4(2).
ACKNOWLEDGEMENT XIAO Zhen thanks Professor M.S. Longair for support during her visit in Edinburgh and Dr. R.S. Stobie and colleagues in the plate library for providing the original plates of the UK Schmidt Near Infrared Survey and for the use of COSMOS.
XIAO
306
TABLE
2
Position
and
Zhen
Colour
et
al.
Indices
RA
of
(1950.0)
131 Infrared Excess Obiec :S L
DEC
R-I
1
423
9
6
55.8
-46
55
19
2.6
2 3 4 5 6 7 8 9 10
424
9
6
59.8
-46
49
12
2.6
835
9
7
11.2
-45
8
39
2.8
422
9
7
17.1
-46
31
3
2.6
B
1675
9
7
29.3
-43
17
6
2.7
AI
1249.
9
7
33.3
-43
51
5V
2.6
1248
9
7
37.7
-44
2
3
2.6
1677
9
7
41.2
-4.?
17
28
2.6
1676
9
7
41.9
-42
I7
53
3.6
1678
9
7
45.0
-42
I5
37
3.1
II
1671
9
7
49.3
-41
25
54
2.6
12
1670
9
7
49.9
-42
27
19
3.8
13
1668
9
7
51.0
-42
30
28
2.6
14
1674
9
7
51.2
-42
16
30
3.2
15
1666
9
7
51.3
-42
41
14
2.7
16
1667
9
7
51.7
-42
37
37
2.7
17
1672
9
7
55.0
-42
22
27
3.8
18
1669
9
7
55.4
-42
30
13
2.6 3.3
B
19
1673
9
7
57.1
-42
21
56
20
1665
9
7
59.7
-42
41
39
2.7
B
21
i 664
9
8
0.8
-42
53
13
2.9
nr
22
1247
9
8
4.3
-44
21
43
2.8
B
23
1661
9
8
9.3
-42
48
21
3.1
24
1662
9
8
10.7
-42
23
27
2.8
25
1660
9
8
14.2
-43
10
59
2.7
26
1663
9
8
20.2
-42
23
11
3.4
27
1656
9
8
28.1
-42
27
43
2.6
28
1657
9
8
32.4
-42
26
43
3.3
29
1655
9
8
32.6
-42
29
48
3.0
30
1659
9
8
34.5
-42
20
41
3.4
31
1658
V
8
34.7
-42
21
11
3.0
32
1653
9
8
35.1
-42
31
5
2.6
33
1651
9
8
35.4
-42
38
i
3.4
34
1650
9
8
37.5
-43
4
I1
2.8
B
B
35
1654
Y
8
38.2
-42
20
16
3.4
36
1652
9
8
41.6
-41
31
30
3.3
37
1645
Y
8
47.0
-42
42
39
2.6
38
1246
9
8
51.3
-43
52
53
3.2
B
39
1646
9
8
55.9
-42
36
50
2.8
M
40
1649
V
8
58.8
-42
19
2
3.5
41
1648
9
8
59.5
-42
20
43
2.6
42
1647
9
8
59.7
-42
26
30
3.0
43
1245
9
9
1.6
-43
34
43
3.0
B
44
1642
Y
9
10.5
-??
36
36
2.7
D
B: double Image
M: multiple
image
D:
.ffUSl image
Infrared
307
Objects
TABLE 2 Continued NO.
RA nlma
(1950.0)
r
DEC
R-l
45
1644
9
9
13.9
-42
16
1
2.8
46
1643
9
9
20.5
-42
22
14
2.8
47
1638
9
9
26.6
-42
25
39
2.9
48
1640
9
9
27.3
-42
19
48
3.2
49
1639
9
9
27.4
-42
20
11
2.7
50
1634
9
9
35.4
-42
41
49
2.7
51
1637
9
9
35.9
-42
31
2
2.9
52
1635
9
9
36.5
-42
38
53
2.9
1636
9
9
48.8
-42
29
27
3.6
54
1631
9
9
51.5
-42
40
16
2.9
55
1633
9
9
52.6
-42
18
52
3.1
56
1632
9
9
58.3
-42
31
17
2.8
57
1629
9
10
6.9
-42
22
57
2.7
58
1628
9
10
7.2
-42
31
52
2.6
59
1630
9
10
14.5
-42
17
5
3.0
60
1244
9
10
16.2
-43
33
49
3.0
61
1626
9
10
19.1
-42
39
I7
2.7
62
1627
9
10
24.0
-42
23
7
3.2
63
834
9
IO
31.9
-44
51
39
2.9
64
1625
9
10
33.8
-42
17
55
3.1
65 66 67 68 69
1243
9
10
34.2
-43
37
36
2*7
1624
9
10
37.4
-42
19
55
3.8
53
1623
9
10
46.5
-42
41
0
3.2
1242
9
10
48.8
-44
45
8
2.6
421
9
10
55.8
-46
56
6
2.6
70
1622
9
11
3.9
-42
IS
48
2.9
‘II
1618
9
11
4.2
-42
29
29
2.9
72
1619
9
11
6.6
-42
28
17
2.6
73
1620
9
11
11.7
-42
18
29
2.6
74
1621
9
il
I2.1
-42
18
15
2.7
75
1617
9
Ii
19.8
-42
IS
2
3.3
76
1615
9
11
21.9
-42
36
32
2.9
77
1616
Y
I1
27.5
-42
15
54
3.0
78
410
9
11
39.1
-46
57
2
2.8
79
1614
9
11
51.8
-42
15
34
2.8
80
1612
9
11
57.8
-42
18
48
2.7
81
418
9
12
0.0
-47
8
5
2.7
82
1613
9
12
3.5
-42
16
13
2.7
83
419
Y
I?
7.0
-46
30
34
2.6
84
1610
Y
IL
8.1
-42
33
51
3.3
85
1611
9
12
15.1
-42
14
58
3.7
86
417
9
12
17.2
-47
11
34
2.9
87
833
9
12
17.6
-45
27
37
2.7
88
632
9
13
0.8
-44
59
39
2.7
89
1609
9
13
14.5
-42
19
7
2.8
90
1608
9
13
38.7
-42
13
38
3.9
B
B
B
B
D
B
B
B
D
B
B
B
308
XIAO Zhen et al.
TABLE 2 Continued
-
NO.
name
I
RA
I
DEC (1950.0)
R-I
91
1607
9
13
45.1
-42
53
24
2.6
92
1606
9
13
59.9
-42
I4
6
3.0
93
1241
9
14
3.4
-43
48
35
2.9
94
1602
9
14
6.9
-43
8
54
3.0
95
416
9
14
9.4
-46
24
34
2.6
96
1603
9
14
9.8
-42
46
4
2.8
97
1604
9
14
13.1
-42
26
28
3.0
90
1605
9
14
22.4
-42
15
28
3.0
99
1601
9
14
37.2
-42
23
19
3.3
100
1559
9
14
52.3
-42
37
15
2.7
JO1
731
9
14
55.0
-45
13
28
2.7
102
1558
9
15
30.3
-42
21
17
2.8
103
1557
9
15
34.5
-42
36
SO
3.2
104
1555
9
16
J9.2
-43
17
11
2.6
JO5
1556
9
16
21.5
-42
43
53
2.9
106
315
9
18
18.7
-47
24
52
2.8
107
1554
9
18
41.0
-42
35
28
2.7 3.2
D
D
B
JO8
1453
9
20
29.2
-42
14
28
JO9
730
9
20
33.5
-45
14
20
2.6
B
110
314
9
20
56.2
-46
48
49
2.6
M
111
B
1139
9
21
34.9
-44
8
2
2.6
112
629
9
12
57.9
-45
9
47
3.7
113
1452
9
25
39.9
-42
25
33
2.7
3
114
213
9
25
Si.2
-47
28
4
2.8
B
115
212
9
29
26.1
-47
24
29
2.7
116
JJJ
9
31
17.7
-47
24
39
2.6
B
117
110
9
31
44.8
-47
24
29
2.8
B
118
109
9
32
1.5
-47
22
10
2.6
119
937
9
32
3.6
-43
58
11
2.9
120
108
9
32
33.6
-46
29
S
2.6
I?i
JO?
9
32
47.1
-47
12
40
2.6
122
196
9
33
10.6
-46
40
52
2.4
4
2.7
a4
2.7
M
123
104
9
33
45.7
-46
15
124
103
9
33
54.9
-46
56
125
JO5
9
33
55.2
-47
29
126
1351
Y
34
23.1
-43
5
127
526
9
34
57.3
-45
32
128
102
9
35
9.4
-47
10
129
1350
9
36
32.5
-42
33
130
936
9
36
53.9
-44
4
131
JO1
9
37
35.1
-47
18
3 19 42 15 42 59 58 10
D
2.7 2.8 2.7 2.9
B
2.6 2.6
hf
3.0
B
Infrared Objects
_r.TABLE 3
Data of the Three Identified IRAS Sources
COSMOS
1R
exeer-
sobjcct No.
RA
78
-46
IRAS source
COSMOS IR ercessobject
!J116-1657
9 11 3Y.l
DEC
No.
-46
57.3
-42.
0.342
0.248
0.611
0.463
56.0(11)50.0) MAGNITUDES
+
+
0
+ t + + b
.
+
4 0
4’- I
9+
I ++ + +
+
at
ao:
0
-I i
a+
‘+ -.-
t +
+
+I+
4”
Fig. 4(2)
3 09 f8 00, -4G 55.0([email protected])
EPOCH:IYSO.O
MAGNITUDES 1
0
+ l00
oO-l-
oo ++
4
O
00
a t
+ 0
Fig. 4(l) F26 i CENTRE:
UDES /
7+
+
9+
-tp ++
0
0%
-
6 -;-
u) i-
0
MAGNI
S-i--
0
8$_
el
0
+
T
+
+
++
a 0
44.0([email protected])
-1s
I1 +
t
+.a
0.437 12.58
15 ?261 :ENTRE: 09 IQ 16, -42 IPOCH:IO~~.O + T
7-k
0
19.0
24 49
0.698
6 -;-
+Qtt*
+“-I-0 90 -;-
+
18
-47
201.13
5-t-
+
it2I”
i+
0
+
‘, ++
o+
Y
24 52
I
l-
+
-6 0
--47
5.150
4
a
9 18 18.7
42 5&
2.Y
36.37
l
106
20.354
4
+++
-42
1.9
CENTRE: 09 10 50, -46 EPOCH:1950.0
0
No.
__
9 16’21.4
43--U
30.622
flux 25 flux 60 flux 100flux 12
F261
COSMOS IR excessobject
_Y163-4242
105
9 16 21.5
9 11 40.2
57 2
2.6
R-l
309
a
I
+ s-l-
++
O
--I-- +f
-I-
s --I-
0
7+ 8+
0
4+
p +
IO + + +
Fig. 4(3)
Fig. 4 Identificationchart of (1) IRAS 9116-4657 with Infrared Excess Object No.78, (2) IRAS 9163-4242 and Object No.105 and, (3) IRAS 9183-4742 and Object No.106.
Ii+
Crosses
are SAO stars, circles are IRAS sources, the crossed square is the identified source
310
XIAO
Zhen
et
al.
REFERENCES
[ I]
Joint
IRAS
[2]
Pratt,
N. M., Virrnr
Science
[3]
Hartley,
[ 4]
Argue,
[ 5]
MacGillivray,
[ 6]
Stobie, R. S. et al., Mon. Nor. R. Arrroa.
[ 7]
COSMOS
M. et al.,
Working
Group,
in Asrronomy, Proc.
ASA,
4(1981),
A. N. et al., A Catalogue
User
H. T. et al., Manual,
IRAS
21(1977),
Virw
Edinburgh,
Catatogue
of Point
Sources,
1984.
1.
251.
of Photometric
Sequences,
in Arrtmomy,
27( 1984). 433.
Sot.,
1981.
222(1986),
Supplement
473.
3, (Ricks
College
Press),
1983.