The observations were performed in April 1995 with the Effelsberg 100-m
radio telescope. The (1, 1) and (2, 2) lines (frequencies equal
23694.495 MHz and 23722.633 MHz, respectively) were observed
simultaneously using a K-band maser amplifier. The system temperature
in the main beam temperature scale (see below)
was
. The spectrometer was a 1024 channel autocorrelator
split into 2 halves of 12.5 MHz each. The velocity resolution was
.
The antenna HPBW was .
The observations were performed in the position-switching
mode with
the reference position displaced by
to the west. The
integration times were
.
Initially,
point maps with 40
spacing were obtained for
most sources. Then, the mapping was continued with the same spacing
according to the initial
results and extended normally to
of the peak antenna
temperature value.
Pointing was checked periodically by observations of nearby continuum
sources; the pointing accuracy was
.
We express
the results in units of main beam brightness temperature (). The main beam efficiency of the antenna at this frequency is
.
The primary calibration source was NGC 7027 for which we assumed
the flux
density as given by Ott et al. (1994). The elevation gain
correction for point sources (Altenhoff, private communication) was applied
to the data. We saw no variations of the beam width with the elevation, so
this correction should be applicable to extended sources too.
The correction factor was
in the elevation range of our
observations.
Name | ![]() | ![]() | l | b | ![]() | d | z | IRAS PSC | ![]() | Remarks |
![]() | ![]() ![]() ![]() | ![]() | ![]() | (kpc) | (kpc) | (pc) | (![]() | |||
S 74 | 19 06 14.9 | 05 31 10 | 39.86 | -1.23 | 7.0 | 2.1![]() | -45 | 19062+0531 | ![]() | |
S 76 E | 18 53 46.2 | 07 49 30 | 40.50 | +2.54 | 7.0 | ![]() | 93 | 18537+0749 | ![]() | o![]() |
S 86 | 19 41 41.2 | 23 21 46 | 59.64 | -0.18 | 7.7 | 1.9![]() | -6 | 19416+2321 | ![]() | |
S 87 | 19 44 13.5 | 24 28 00 | 60.88 | -0.13 | 7.6 | 2.3![]() | -5 | 19442+2427 | ![]() | o |
S 88 B | 19 44 41.4 | 25 05 17 | 61.48 | +0.10 | 7.7 | ![]() | 3 | 19446+2505 | ![]() | o |
S 90 | 19 47 05.2 | 26 43 21 | 63.12 | +0.44 | 7.6 | 4.0![]() | 31 | 19470+2643 | ![]() | |
S 93 | 19 52 56.0 | 27 04 54 | 64.14 | -0.47 | 7.7 | 3.2![]() | -26 | 19529+2704 | ![]() | |
S 100 | 19 59 50.0 | 33 24 20 | 70.29 | +1.60 | 9.5 | 8.0![]() | 223 | 19598+3324 | ![]() | o, K3-50 |
S 145 | 22 27 12.2 | 63 58 21 | 108.19 | +5.52 | 8.8 | 0.9![]() | 87 | 22272+6358A | ![]() | o, L1206 |
S 146 | 22 47 30.9 | 59 39 03 | 108.20 | +0.58 | 10.9 | 4.7![]() | 48 | 22475+5939 | ![]() | |
S 161 B | 23 14 01.9 | 61 21 22 | 111.89 | +0.88 | 9.9 | 2.8![]() | 43 | 23140+6121 | ![]() | |
S 199 | 02 57 35.6 | 60 17 22 | 138.30 | +1.56 | 10.2 | ![]() | 57 | 02575+6017 | ![]() | o, IC1848A |
S 201 | 02 59 20.6 | 60 16 08 | 138.50 | +1.64 | 10.2 | 2.1![]() | 60 | 02593+6016 | ![]() | |
S 231 | 05 35 48.8 | 35 43 41 | 173.47 | +2.55 | 10.8 | 2.3![]() | 102 | 05358+3543 | ![]() | o |
S 255 | 06 09 57.9 | 18 00 12 | 192.60 | -0.05 | 11.0 | ![]() | -2 | 06099+1800 | ![]() | o, S254/S258 |
RNO1B | 00 33 53.3 | 63 12 32 | 121.30 | +0.66 | 9.4 | 0.85![]() | 18 | 00338+6312 | ![]() | o, L1287 |
BFS 48 | 05 48 04.8 | 25 45 29 | 183.35 | -0.58 | 10.6 | 2.1![]() | -21 | 05480+2545 | ![]() | |
|
The objects for the observations (Table 1 (click here))
were selected primarily from the
list of dense molecular clouds associated with Sharpless HII regions
studied earlier in the J=1-0 HCN, ,
and
lines by Burov et al. (1988), Zinchenko et al.
(1990) and Pirogov et al. (1995). The selection was
made according to the criteria similar to those used in Paper I, i.e.
the flux in the IRAS Point Source Catalogue at
should be larger than 500 Jy. However, the
right ascension of
instead of
as in Paper I
was considered.
In addition, several clouds from Papers I and II were included for
detailed mapping in the ammonia lines. Most of these objects are
associated with
masers.
Almost all of the selected targets represent sites of high mass star formation except S 145 (L 1206) and RNO 1B (L 1287) where mostly intermediate mass stars are born.
The source coordinates are presented in Table 1 (click here) together
with the estimates of the galacto-centric distance of the source
(), its
distance from the earth (d) and its height above the galactic plane
(z).
We adopted IRAS positions as central coordinates of the sources.
For some clouds very different distance estimates have been published.
For the sake of the
homogeneity of the results we adopted, where available,
the spectrophotometric
distances given by Brand & Blitz (1993). Some other
references to the distance estimates are given in Table 1 (click here).
The galacto-centric distances were calculated using the standard IAU
value for
of 8.5 kpc.
In Col. (10) we present the IRAS luminosities of our sources calculated as in Henning et al. (1990).
We have reduced the data and produced maps using the GAG
(Groupe d'Astrophysique de Grenoble)
software package.
The measured spectra were fitted by the function
(
is the optical depth in the j-th component)
describing one or more ammonia
hfs patterns assuming gaussian velocity distributions and equal widths
of the hfs components in each pattern.
The derived parameters were the line intensities, LSR velocities
and FWHM for the opacity distribution.
For the spectra of sufficiently good quality
it was possible to derive the optical depth as a sum of the peak opacities
of the main group of hyperfine components from this fit.
The next steps in the data analysis were the derivation of the rotation
temperature , kinetic temperature
and total ammonia
column density
).
These estimates have been made according to the
procedure described by Harju et al. (1993).
From the ammonia column densities we derived hydrogen column densities
and masses of the cores assuming the relative abundance of
(see the discussion by Harju et al.).
We estimated the source areas (A) by integrating the column densities over
the maps presented in Sect. 3 (click here) and dividing these values
by the peak column densities. The angular sizes were found then from
.
It is worth mentioning that for a gaussian brightness distribution this
estimate gives the size at the
level which is by a factor of
larger than the size at the half-power level.
Then the linear dimensions (L) were determined
using the distances from Table 1 (click here). Some sources are
elongated so that these sizes represent geometric mean values between their
axes.
We attempted to take into account the beam size in an approximate
way (as in Zinchenko 1995).
We use ``deconvolved'' sizes
defined as
where
is the antenna beam width at the corresponding
level.
Of course, this procedure
accounts for the beam size only approximately because many cores are
elongated or have a rather complex brightness distribution. The density
estimates have been corrected accordingly. Actually, these corrections
do not exceed a few percent.
The mean densities were obtained as the peak column densities divided by these sizes. The masses were estimated from the integrals of the column densities. A factor of 1.36 (the ratio of total gas mass to hydrogen mass, e.g. Hildebrand 1983) was applied to derive the total mass of the cloud. The average line widths are the widths of the average source spectra and include therefore velocity gradients in the source. The virial masses have been calculated as in Paper II.
Figure 1: The integrated (1, 1) line intensity maps
(grey-scale). The levels start from 15% of the
peak intensities in steps of 7.5%.
The velocity ranges are indicated in Table 2 (click here).
Solid and dashed contours correspond to the blue- and red-shifted
velocity intervals, respectively (see text). The levels for these contours
are the following: from
with
increment a), from
with
increment b), from
with
increment c, g, h, j), from
with
increment f),
from
with
increment
i) The crosses show the positions of the strong IRAS point sources listed
in Table 1 (click here). The triangles indicate the positions of the
masers. The asterisks mark the positions of near-IR sources from
the CIO catalogue. The dotted contours correspond to the CS J=2-1 maps
from Paper II