2 Observation and data analysis

Far-infrared data:

we searched for faint, small, cold sources with no IRAS associations in the region $95\hbox{$^\circ$ }<l<115\hbox{$^\circ$ }$, $10\hbox{$^\circ$ }<b<20\hbox{$^\circ$ }$, where the ISOSS survey has over 50% coverage. ISOSS 170 $\mu$m data were smoothed to the IRAS ISSA (Wheelock et al. 1994) resolution, and processed according to Tóth et al. (2000) and Hotzel (2001). Sources were selected using the following criteria: a size $FWHM \le 6\hbox{$^\prime$ }$, a 170 $\mu$m source surface brightness $8\pm 5$ MJy sr^-1, and a background corrected colour parameter $CP=6.4\pm 0.5$, no associations in the IRAS Point Source Catalogue, or in the IRAS Faint Source Catalogue within 5 $\hbox{$^\prime$ }$, and no excess in the IRAS ISSA maps above 0.6 MJy sr^-1. We located 50 objects fullfilling our criteria. ISOSS J20246+6540 was also detected as an $I_{170}(\rm peak)= 4$ MJy sr^-1 (>$4\sigma$) pointlike source at RA(2000 $)=20^{\rm h}$24$^{\rm m}$36$^{\rm s}$ Dec(2000 $)=+65\hbox{$^\circ$ }$40 $\hbox{$^\prime$ }$ ( $l=99.8\hbox{$^\circ$ }$, $b=15.7\hbox{$^\circ$ }$). with an unsmoothed ${\it FWHM} \le 150\hbox{$^{\prime\prime}$ }$. We note that the unsmoothed ISOSS point-spread function is nearly Gaussian with $FWHM\approx 130\hbox{$^{\prime\prime}$ }$.

Optical data:

the Digital Sky Survey (DSS2) blue plates indicated optical counterparts for 41 of the 50 ISOSS sources, out of which 5 isolated, globule like sources were found. Three of them bear opaque cores resembling the globule of Dickman & Clemens (1983) and two are without any opaque core: ISOSS J20215+6820 and ISOSS J20246+6540. Table 1 lists (1) ISOSS names, (2, 3) galactic coordinates, (4) optical dimensions in arcminutes, (5) the distance to the nearest cloud neighbours

 

 

Table 1: Five ISOSS globules and their nearest cloud neighbours, CB88: Clemens & Barvainis (1988), YDM97: Yonekura (1997) (*) refers to an unnumbered peak, LM99: Lee & Myers (1999).

ISOSS name	l	b	$a\times b$	nearest
	[ $\hbox{$^\circ$ }$]	[ $\hbox{$^\circ$ }$]	[ $\hbox{$^\prime$ }$]	neighbour
ISOSS J20180+6345	97.71	15.29	$5\times 3$	8'CB88 #219
ISOSS J20215+6820	102.00	17.34	$3\times 2$	45'YDM97 #4
ISOSS J20246+6540	99.79	15.69	$4\times 2$	20'YDM97(*)
ISOSS J20380+6352	99.05	13.51	$5\times 2$	12'CB88 #224
ISOSS J20474+6014	96.72	10.46	$5\times 5$	14'LM99 #349

Further 8 sources were associated with complexes of reflecting clouds. Detailed optical study of the 5 globule like clouds and a study of statistical issues will be given elsewhere. As an example we present results on ISOSS J20246+6540 which was studied using DSS2 blue and red images. In order to make surface brightness maps of ISOSS J20246+6540, stars were removed from the optical images by substituting the average surrounding photographical density value.

Radio spectroscopic measurements:

the J=(1-0) and (2-1) rotational lines of CO, ¹³CO and C¹⁸O were measured in Aug. 1998 with the IRAM-30 m telescope. A $4.5\hbox{$^\prime$ }\times 4.5\hbox{$^\prime$ }$ region centered on ISOSS 20246+6540 was mapped in on-the-fly mode in ¹²CO(1-0), ¹²CO(2-1) and ¹³CO(1-0) with angular resolutions of 22 $^{\prime\prime}$, 11 $^{\prime\prime}$, 22 $^{\prime\prime}$ respectively. Pointed measurements were performed in all the above mentioned transitions at the ¹³CO(1-0) peak position (22$^{\rm h}$24$^{\rm m}$46$^{\rm s}$, 65$^\circ$40$^\prime$01 $^{\prime\prime}$). Spectral resolutions of 0.1, 0.05 and 0.03 km s^-1 were used. These spectra are shown in Fig. 1.

Figure 1: CO spectra at the 13CO(1-0) peak, (2-1) lines are overlaid as filled histograms. a) 12CO(1-0) and (2-1) spectra. b) 13CO(1-0) and (2-1) spectra. c) C18O(1-0) and (2-1) spectra.

The lines are narrow with a FWHM of $\le$0.5 km s^-1. The results of the 1998 C¹⁸O pointed measurements were confirmed in Sep. 2000 when also the CS(2-1) and (3-2) as well as the HCO⁺(1-0) and (2-1) transitions were observed with the IRAM-30 telescope. The C¹⁸O, CS(2-1) and HCO⁺(1-0) lines were detected with S/N>5 and well resolved with the 0.03 km s^-1 spectral channels. The data were calibrated to the scale of corrected antenna temperature, $T^*_{\rm A}$, by observing loads at ambient and cold temperature, as in the conventional "chopper-wheel'' calibration for millimetre wavelength observations. The data were converted to the main-beam scale by applying the relation $T_{\rm MB} = T^*_{\rm A} (F_{\rm eff}/B_{\rm eff})$. The values for the main-beam efficiency, $B_{\rm eff}$, are 0.70 and 0.42 (July 1998), and 0.75 and 0.53 (September 2000), and the values for the forward efficiency, $F_{\rm eff}$, are 0.92 and 0.85 for CO(1-0) and CO(2-1), respectively. We checked the calibration by observing the standard sources DR 21 and W3OH and found it always to be better than 20%. Results are listed in Table 2.

 

 

Table 2: Radio spectroscopy results for pointed measurements towards the NE lobe, $\Delta T_{\rm rms}$ is given in parentheses after $T_{\rm MB}$, errors of the Gaussian line fit are given in parentheses for FWHM and $v_{\rm LSR}$, asterisk marks selfabsorbed lines.

line	$T_{\rm MB}$	FWHM	$v_{\rm LSR}$
	[K]	[km s-1]	[km s-1]
12CO(1-0)	6.7* (0.11)	0.43 (0.01)	-2.70 (0.01)
12CO(2-1)	5.41 (0.17)	0.47 (0.01)	-2.69 (0.01)
13CO(1-0)	4.3* (0.14)	0.32 (0.03)	-2.68 (0.01)
13CO(2-1)	3.60 (0.08)	0.31 (0.01)	-2.70 (0.01)
C18O(1-0)	0.11 (0.02)	0.25 (0.02)	-2.68 (0.01)
C18O(2-1)	0.10 (0.03)	0.24 (0.03)	-2.76 (0.02)
CS(2-1)	0.09 (0.02)	0.25 (0.02)	-2.69 (0.01)
HCO+(1-0)	0.20 (0.03)	0.29 (0.03)	-2.70 (0.01)