The 2CG sources 218-00, 135+01, 121+04 and 95+04 have been observed at two radio frequencies and the flux values and spectra of the radio sources observed within the gamma-ray fields are catalogued down to a sensitivity of approx 30 mJy at lambda 11 cm. Possible gamma-ray counterpart candidate objects are briefly discussed

Oezel, M. E.

Schlickeiser, R.

Sieber, W.

English

NASA Technical Reports Server

225
OG 2.5-10
RADIO OBSERVATIONS OF FOUR ._TICENTER 2CG y-l_.Y SOURCES
M.E. _zel, R. Schlickeiser, W. Sieber
Max-Planck-lnstitut fur Radioastronomie
Auf dem HUgel 69, 5300 Bonn I, FRG
ABSTRACT
The 2CG sources 218-00, 135+01, 121+04 and 95+04 have been
observed at two radio frequencies and the flux values and
spectra of the radio sources observed within the y-ray
fields are catalogued down to a sensitivity of _30mJy at
%11 cm. Possible y-ray counterpart candidate objects are
briefly discussed.
I. Introduction. Identification of y-ray sources suffers from the
angular indeterminacy of their positions (A@ _ I°). Our program to help
their identification aims at the radio mapping of the regions at least at
2 frequencies, allowing a catalogue of radio sources with spectra and
fluxes down to _ 30mJy sensitivity limit at %11 cm. Possible scenarios
in view of the present observations are briefly given at the end.
2. Observations. Using the 100-m Effelsberg telescope of the MPIfR
error boxes as given by Swanenburg et al. (1981) are mapped in radio con-
tinuum at frequencies 1420 MHz (%21 cm), 1720 MHz (%18 cm), 2700 MHz (%11
cm) and 4750 MHz (%6 cm). Each y-ray region has been scanned at least at
two of these frequencies to facilitate spectral information about the
detected sources. Interesting fields have also been searched for polar-
ization characteristics. Here, only one map for each source is repro-
duced with some information about observations. Further details can be
found in Ozel et al. (1985a, hereafter referred to as Paper I).
3. Results. The resultant maps for the fields (I map for each) are
given as Figures I, 2, 3 and 4, respectively. Source lists and other
more detailed information are given in Paper I. Important radio objects
for each y-ray source field will be discussed below.
218-00: This field (Fig. I) contains the extended source 0657-040, which
is a catalogued HII region ($287 in Sharpless (1959)) and needs to be
considered further. Scenarios based on the excess activity in star for-
mation complexes require an enhancement of CR flux by a factor f _ 10 as
compared to solar cosmic ray densities. A hidden supernova near or with-
in the cloud is needed to connect the observed y-ray activity to 0657-040.
135+01: The major radio object in the field (Fig. 2), W4, covers almost
the total area. Scenarios similar to 218-00 under more favorable condi-
tions seem to be at work as suggested by Montmerle (1979) and others.
The "source" 0024+617 (which is part of the W4 complex) with its
enormous (_ 50 pc) jet-like protrusion might have important implications
for the nature of W4 in general.
12|+04: A previously unknown extended feature has been discovered in
th--_ield (Fig. 3). Preliminary calculations (polarization, morphology)
indicate that it probably is a SNR of age _ 105 yrs. The center-filled
nature suggests a Crab-like pulsar mechanism by a fast compact object, and
.. 
26 
 .5-10 
DIO S ATIONS   ANTICENTER 2  y-RAY  
.E. Ozel, R. Schlickeiser, . Sieber 
ax-Planck-Ins itut Ur adioastronomie 
uf de  Ugel 69,5300 Bonn 1, FRG 
BSTRACT 
he 2  sources 18- 0, 35+01, 1+04 a  04 ave een 
bserved t t  dio f uencies d t e l  alues d 
spectra of the radio sources observed ithin the y-ray 
fi lds are catal gued do n t  a sensitivity f 'V 30 mJy at 
All c . possible y-ray counterpart candidate objects are 
briefly discussed. 
1. I troduction. I entification f -ray s urces suffers fro  t e 
angular indeterminacy of their positions (~e 'V 1°). ur program to help 
t eir i entification i s t t e io a ping f t e ions t l ast t 
2 frequencies, allo ing a catalogue of radio sources ith spectra and 
fl es n t  'V  mJy nsitivity li it t All . o sible enarios 
in vie  of the present observations are briefly given at the end. 
2. bservations. sing the 100-  ffelsberg telescope of the PlfR 
error boxes as given by Swanenburg et al. (1981) are apped in radio con-
tinuum at frequencies 1420 MHz (A21 cm), 1720 MHz (A18 cm), 2700 MHz (All 
) d 50 Hz (A  ). ach -r y r ion as een nned t l ast t 
t o of these frequencies to facilitate s ectral infor ation about the 
etected s urces. I teresting fi l s ve l  en s arched f r olar-
ization characteristics. ere, only one ap for each source is repro-
ced ith e f r ation out bservations. urther etails  e 
found in ozel et al. (1985a, hereafter referred to as Paper I). 
. esults. e r sultant aps f r t  fi l s (1 ap f r ch) re 
given as i ures 1, ,3 and , respectively. ource lists and t er 
ore etailed i f r ation r  i en i  aper I. I portant r io bjects 
for each y-ray source field ill be discussed belo . 
8- 0: his fi l  ( i . 1) ntains t  t ded s urce 57-040, hich 
is a catal gued II re ion (S287 i  harpless ( 59)) and eeds t  e 
nsidered rt er. cenarios sed  t  ce s tivity i  t r r-
ation c plexes r uire a  e ancement f  fl   a f ctor f ~  as 
co pared to solar cos ic ray densities.  hidden supernova near or ith-
i  t  l d i  eeded t  c nect t  served -r y tivity t  57-040. 
135+01: The ajor radio object in the field (Fig. 2), 4, covers al ost 
•  t l . enarios ilar  8-00 der ore orable ndi-
ti s see  t   t ork s s gested  ontmerle ( 9) a  t ers. 
he urce" +617 ( hich i  art f t  4 plex) ith  
enor ous ('V 50 pc) j t-like r trusion ight have i portant i plications 
for the nature of W4 in general. 
121 04:  reviously unkno n extended feat re has been discovered i  
t is field ( i . ). r li inary l ulations ( larization, orphology) 
indicate that it probably is a S R of age ~ 105 yrs. he center-filled 
nature suggests a rab-like pulsar echanism by a fast co pact obj ect, and 
https://ntrs.nasa.gov/search.jsp?R=19850025652 2020-03-20T17:53:28+00:00Z
F i g .  1 :  
2CG218-00 f i e l d  a t  A2 1 
cm. C i r c l e  deno te s  90% 
COS-B e r r o r  box. Zero 
l e v e l  i s  dashed. Contour 
s t e p  s i z e  (10) i s  19mJy. 
Maxima a r e  enc losed  by 
CCW arrows.  0657-040 
l i e s  a t  upper c e n t e r .  
(HPBW i s  9!4 x 9!4, t h e  
c i r c l e  a t  uppe r - l e f t  
c o r n e r .  ) 
Fig.  2: 
2CG135+01 f i e l d  a t  All 
cm. The f i r s t  contour  
above z e r o  i s  a t  15 mJy 
(1 0 ) .  Subsequent con- 
t o u r s  a r e  a t  30 i n t e r -  
v a l s .  HPBW i s  4!4 x 4!4. 
A p r o t r u s i o n  s t a r t i n g  
from 0024+6 17 (lower 
c e n t e r )  towards 6 62P1 
i s  obse rvab le .  
2.28 
OG 2.5-10 
Fig. 1: 
2C 218-00 field at A21 
c . ircle denotes 90% 
COS-B error box. Zero 
level is dashed. Contour 
step size (10') is 19mJy. 
axima are enclosed by 
CCW arro s. 0657-040 
lies at upper center. 
(HPB  is 9!4 x 9!4, the 
circle at upper-left 
corner.) 
Fig. 2: 
2CG135+01 field at All 
cm. The first contour 
above zero is at 15 mJy 
(10). Subsequent con-
tours are at 30 inter-
vals. HPB  is 4!4 x4!4. 
A protrusion starting 
from 0024+617 (lower 
center) towards 8 ~ 62? 1 
is observable. 
• 
227 OG 2.5-10
o.--<' ..... " .:l,oJIIffJ
*G7
*G7
: '. _......'.':'" Fig. 3:2CG121+04 field at X18
•66 _-_C-_ , :i,,
_" ___ _"i.;:; cm. The first contour
: . above dashed (zero)
+66 __:___ __ level is at 60 mJy (20);
subsequent contours are
separated by I_. The
+66 ) ¢ <Jr'-. _J° ° "_.__ --_---_--,. extended feature
_,¢_--_" '_) <, (; G120.6+3.2 is approxi-•_5 z_r'_"_/_ _-__ mately centered at _ _
_S_Lj_.j_-_k_j_ _o/ g,_j_ ,-_ 0hm6m, _ _ 65040 ''and
+85 >_ I" __._',_S _,_, has a center-filled
_O l _ti_ _ t ............ (/I morphology. It is
,6_ -_<_ / "'Jt_ <_ _ . ifi/'..' J. _ tentatively identified
OOH4OMOOX36MO0.32M OOH2SM00.24,, 00.20,, o0x,_M as a supernova remnant.
o"
.............i_o_0,, ' .f-_ Oi '".. o . .. ,-
54°00' _<-') r /_ _ _i j Fig. 4:
5,0,0. ,-'__., x__ :, . ,, _-.',v,_ rated by 24 m;;e(;3_ a-
21h24m 2f20m 21h16m 21h12m 21h08m HPBW as in Fig. 1.
227 
.. 
.. 
G . -10 
Fig. 3: 
G121+04 i l  t \  
cm. The first contour 
above dashed (zero) 
level is at 60 mJy (20); 
s bsequent ontours r  
separated by 10. he 
extended feature 
G120.6+3.2 is approxi-
ately centered at a ~ 
Oh26m, <5 ~ 65 0 40" and 
has a center-filled 
morphology. It is 
tentatively identified 
  pernova r nant . 
Fig. 4: 
2CG095+04 field at \21 
cm. Contours are sepa-
rated by 24 Jy (20). 
HPBW as in Fig. 1. 
|28
OG 2.5-10
such a search (for P _ 5 ms) has been undertaken as a further work for
this field (Ozel et al., 1985b).
95+04: This field (Fig. 4) is full of (extragalactic?) non-thermal radio
sources. Near to its center lies one of the few flat-spectrum sources,
21i6+541. Cold dark matter in the region is already catalogued as LDN
1060, 1062, 1072 by Lynds (1962). Diffuse mechanisms of enhanced CR-
matter interactions might be at work in this field.
4. Conclusion. These new observations give us further information
about the objects in the 4 y-ray source fields. Tentative scenarios
noted above are byno way conclusive. Further work is required to under-
stand the message of radio observations.
References
Lynds, B., (1962), Astrophys. J. Suppl. _, I
Montmerle, T., (1979), Astrophys. J. 231, 95
_zel, M.E., Schlickeiser, R., Sieber, W---_,(1985a), submitted to Astron.
Astrophys. (Paper I)
Ozel, M.E., Buccheri, R., D'Amico, N., Schlickeiser, R., Seiradakis,
J.H., Sieber, W., (1985b), in preparation
Sharpless, S., (1959), Astrophys. J. Suppl. 4, 257
Swanenburg, B.N., Bennett, K., Bignami, G.F._ Buccheri, R., Caraveo, P.,
Hermsen, W., Kanbach, G., Lichti, G.G., Masnou, J.L., Mayer-Hassel-
wander, H.A., Paul, J.A., Sacco, B., Scarsi, L., Wills, R.D., (1981),
Astrophys. J. 243, L69
118 
OG 2. -10 
such a search (for  ~ 5 s) has been undertaken as a further ork for 
th s field (O  e   )  
95+04: his field (Fig. 4) is f ll of (extragalactic?) non-ther al radio 
sources. ear to its center lies one of the few flat-spectru  sources, 
2116+541. old dark atter in the region is already catalogued as LON 
, 1 , 072  s (1 ). iff s  ec a is s of  -
att  intera io  i t   r  in th  ie  
. onclusi n. s  e  s r ati s iv  s f rt r infor ati  
t th  j t  i  th    r  ield . t ti  ri  
noted above are by no way conclusive. Further work is required to under-
ta  t,  essa e  i  r ati s. 
ef r es 
Lynds, B., (1962), Astrophys. J. Supple 7, 1 
ontmerle, ., (1979), strophys. J. : 95 
ozel, .E., Schlickeiser, ., Sieber,~, (1985a), sub itted to stron. 
str hys. r  
ozel, .E., Buccheri, R., D'A ico, N., Schlickeiser, R., Seiradakis, 
J. ., Sieber, ., (1985b), in preparation 
harpless, ., ( 9), str hys. J. le ,  
Swanenburg, B.N., Bennett, K., Bignami, G.F.: Buccheri, R., Caraveo, P., 
Her sen, ., Kanbach, ., Lichti, G.G., asnou, J. ., ayer-Hassel-
wander, H.A., Paul, J.A., Sacco, B., Scarsi, L., ills, R.D., (1981), 
strophys. J. 243, L69 


Radio observations of four anticenter 2CG gamma-ray sources

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