The spectra of all detected sources are plotted in Fig. 1 (click here) (masers)
and Fig. 2 (click here) (thermal and absorption sources). Frequency and polarization are
marked in the upper right corner of each figure. When no polarization is
specified, the spectrum is an average of the right and left hand circular
polarizations.
Although we took all precautions to eliminate spurious observations, we
cannot exclude the possibility that unnoticed radio frequency interference,
in particular from satellites, may have corrupted some spectra.
These two sources are IRAS cores in IRAS dark clouds identified by Wood et al. (1994). Cas D1 has one association in the IRAS Catalog, but the associated point source is shifted from the position of Cas D1 core by 5' in right ascension and does not fall in the Nancay radiotelescope main beam. Cas C1 has no any known associated stars or IRAS point sources.
The spectra of Cas C1 and Cas D1 have broad thermal components at
3 
and -15 
respectively and
narrow maser lines at 1665 MHz at 16.11 
for Cas C1 and 15 
for Cas D1. The maser feature in Cas C1 is 100 percent left
circular polarized, but the maser in Cas D1 does not exhibit significant
circular polarization. The degree of circular polarization is hereafter
defined as the R-L/R+L intensity ratio.
The IRAS source lies in the S198 optical nebula. Blitz et al. (1982) observed the region in the CO (1-0) line and did not have a definite detection. The OH maser at 1665 MHz is unpolarized within errors and has a flux density of 0.2 Jy. At 1667 MHz, we obtained an upper limit of 0.05 Jy.
At 1665 MHz a maser emission was detected with a degree of circular
polarization of 78 percent. For our sample the flux density of this maser is
rather large - 1.6 Jy. At 1667 MHz we detected a broader thermal line. The
velocity of the 1665 MHz maser feature differs from that of the 1667 MHz
line by 38 
. This velocity difference probably suggests that
the 1665 MHz and 1667 MHz lines come from different objects within the
antenna main beam.
We detected a strong (2.7 Jy) maser emission at 1665 MHz with -54 percent
circular polarization. Furthermore, the degree of circular
polarization varies
with velocity and approaches 100 percent in the red wing. At 1667 MHz, an upper
limit of 0.09 Jy was obtained. Wouterloot & Brand (1989) observed this
source in CO (1-0) line at 
= -25.9 
which is
shifted from the OH maser line by 4.5 
.
A weak narrow maser at 1665 MHz with 33 percent circular polarization was
detected towards the infrared source AFGL 5142. Wouterloot & Brand
(1989) detected CO emission at -3.9 
coincident with the
velocity of the OH maser.
At 1665 MHz, the source emits two circularly polarized features with a
velocity difference of 5.2 
. The degree of circular
polarization of each feature is greater than 90 percent. Such a profile
structure is typical of Zeeman splitting. Supposing that this is a true
Zeeman doublet, we derive a value for the magnetic field of 8.8 mgauss
which is close to 10 mgauss, the maximum value measured in OH masers. In
the 1667 MHz line, the source emits a weak, broad and unpolarized feature at
-21.5 
. The IRAS source is situated near the position in the
optical nebula S235 observed in the four OH lines at 18 cm by
Turner (1979), the separation in right ascension being 5.6 arcminutes.
Turner did not detect OH emission. The IRAS source was observed in the
line at 22 GHz by Wouterloot et al. (1988), but no emission was
detected.
The 1665 MHz line in the right circular polarization
coincides with the
strongest 1667 MHz feature at 
= -4 
. But in
the left circular polarization at 1665 MHz, the velocity of the maser feature
is -12.9 
, shifted by 8 
. This velocity
difference cannot be attributed to Zeeman splitting because the degree of
circular polarization is only 18 percent. Wouterloot & Brand (1989)
detected CO emission towards this source at -9.6 and 2.6 
radial velocities.
As well as in the previous source, we observe two narrow spectral
features
in right and left hand circular polarizations at 1665 MHz. But the velocity
difference is less than 0.01 
, which gives an upper limit
of 0.017 mgauss for the magnetic field. The degree of circular
polarization is also small 
8 percent. The line profile has a red wing
which could be fitted with a Gaussian at a velocity shifted by 0.31 
from the main feature and with an intensity about 6 times
smaller. The source was not detected at 1667 MHz. Wouterloot & Brand (1989)
detected a CO line towards this source at 44.3 
radial velocity
which differs by 5 
from the OH maser line. They also report
the presence of wings in the line profile.
The source is rather weak, but the strongest feature in the right circular
polarization at 1665 MHz suggests maser excitation. The degree of
polarization of the 1665 MHz line is 37 percent. Wouterloot & Brand
(1989) detected CO emission at 
= 15.24 
.
This maser was detected by MacLeod (1991) only in the 1665 MHz line.
We also detected emission at 1667 MHz with a radial velocity shifted from the
1665 MHz features. We observed with higher velocity resolution and signal-to-
noise ratio than MacLeod (1991) and find that the 1665 MHz
line consists of three very narrow features shifted in velocity by equal
amounts of 0.3 
. The degrees of circular polarization of the
1665 MHz features are respectively 51, 52 and -11 percent. At 1667 MHz,
we observed one narrow left-polarized feature shifted by 1.6 
from the center of 1665 MHz line. Wouterloot & Brand (1989) detected CO
emission at 67.4 
. The CO line has a red asymmetric top.
The detection of a possible OH maser towards this source was reported in Paper I. We reobserved it at 1665 MHz with higher frequency resolution and confirm the presence of the OH maser with a flux density of 0.4 Jy.
These sources resemble OH/IR stars with their typical double peaked spectra at
1667 MHz. 17269-2235 was also observed at 1612 MHz with the same OH/IR line
profile as at 1667 MHz. 17416-2112 has a weak broad line at 1665 MHz in the
velocity range extending between the two narrow 1667 MHz components. 17579-3121
was not detected at 1665 MHz. However, both 20361+5733 and 21432+4719 show a
double-peaked pattern at 1665 MHz. Towards 21432+4719, Wouterloot &
Brand (1989) detected CO line emission at 4.80 
.
At 1665 MHz, this source emits a 100 percent circularly polarized line
at 
= 19 
. At 1667 MHz we detected a broad
absorption feature, possibly from a cloud in which the 1665 MHz maser is
embedded.
This OH maser near W28 was discovered by Gaylard et al. (1994). The maser features are superimposed on a strong broad absorption. The maximum flux density at 1665 MHz is 4.7 Jy. The degree of left circular polarization of the strongest feature at 1665 MHz is close to 100 percent.
The source contains a broad maser (flux density at 1665 MHz greater than at
1667 MHz) unpolarized line at 
= 6 
. But at
1667 MHz, a narrow feature is also present at 14 
. The spectra
resemble 20361+5733 where, along with a broad unpolarized maser
feature at -1.5 
, we detected a narrow and weak line at
1665 MHz at 
= 14 
.
The source exhibits three maser features at 1665 MHz with radial
velocities of
-76, -72 and -68 
. The first and third features
are unpolarized
within errors, while the second one has almost 100 percent left circular
polarization. At 1667 MHz, the maximum flux density is about 0.15 Jy which
is
more than 3 times weaker than the 1665 MHz emission.
The source has a two-peaked line profile at 1667 MHz with a velocity
difference of 5 
. The flux ratio of the peaks is 3. At 1665 MHz,
only the strongest feature is seen, so the ratio must be greater than 6.
Towards this source, a weak unpolarized emission was detected at 1665 MHz.
At 1667 MHz, an upper limit of 0.05 Jy was set. Wouterloot & Brand (1989)
detected towards this source CO emission at 
= -62.39 
. The CO velocity differs from that of OH by 73 
,
the 
of OH maser being 10 
. The features are
thus different objects in the antenna main beam.
At 1665 MHz, we detected towards this source a weak unpolarized emission at
8.5 
. The emission at 1667 MHz is shifted by -10 
and its radial velocity coincides with the CO line detected
at
= -1.75 
by Wouterloot & Brand (1989).