1 Introduction

The reason for this large mapping project is twofold: i) the authors are heavily involved in the Odin project - a Swedish submillimetre wave spectroscopy satellite for astronomy and aeronomy (Hjalmarson [1997]), where the key astronomy goals are observations of H₂O and O₂ in the Galaxy. O₂ has not yet been detected in the interstellar medium even though lately several serious attempts have been made (in gas form: Combes et al. [1991]; Fuente et al. [1993]; Pagani et al. [1993]; Combes & Wiklind [1995]; Maréchal et al. [1997]; Combes et al. [1997]; Olofsson et al. [1998]; Melnick et al. [1999], and in solid form by ISO observations: Ehrenfreund & van Dishoeck [1998]; Vandenbussche et al. [1999]). This and associated papers deal with ground based support observations aiming at finding the best O₂ search targets. Secondly ii), according to current knowledge from modelling of interstellar chemistry the main formation and destruction routes for O₂ and SO are very similar. O₂ and SO are formed in reactions between O or S with OH, and are destroyed by reactions with C as long as carbon is abundant. This means that the O₂ and SO abundances are expected to stay low at early times and that both abundances will rapidly increase to a rather constant level when most C has been locked up in the formation of CO (e.g. Graedel et al. [1982]; Prasad & Huntress [1982]; Millar & Nejad [1985]; Millar & Herbst [1990]; Millar et al. [1991]; Bergin et al. [1995]; Bergin et al. [1997]; Millar et al. [1997]). Hence our second goal is to study observationally and by chemical modelling what is causing eventual abundance variations of SO and O₂.

The observational part of this work is based upon the SO/CS abundance ratio maps derived from observations of the SO(3₂-2₁) and CS(2-1) at 99.3 GHz and 98.0 GHz, respectively, supplemented by ³⁴SO(3₂-2₁) and C³⁴S(2-1) observations to handle optical depth problems. The reason why we are "normalizing'' with CS is that this species - according to the chemical models - is rising to a high abundance already at early times and then stays rather constant in time. The SO and CS transitions selected have rather similar upper state energies and excitation requirements. These questions will be treated in a subsequent paper (Nilsson et al. [2000], Paper II).

The organisation of this article is as follows. In Sect. 2 we describe the details of the observations and in Sect. 3 all the mapping data are presented as SO and CS integrated intensity contour maps. In crucial positions the lines ³⁴SO, C³⁴S, CS, and SO spectra are also shown.

 

 

Table 1: Source list

Source	Position		$V_{\rm LSR}$	Adopted distance	Reference
	$\alpha$(B1950.0)	$\delta$(B1950.0)	(kms-1)	(kpc)	Distance	Molecular
W3(IRS4)	02 </I>h21 </I>m43 $.\!\!^{\rm s}$5	+61$^\circ$52$^\prime$49 $^{\prime\prime}$	-43.0	2.4	1,2
W3(OH)	02 </I>h23 </I>m17 $.\!\!^{\rm s}$0	+61$^\circ$38$^\prime$53 $^{\prime\prime}$	-48.0	2.4	1,2
NGC 1333	03 </I>h25 </I>m58 $.\!\!^{\rm s}$2	+31$^\circ$05$^\prime$46 $^{\prime\prime}$	+7.0	0.35(0.22-0.5)	3	3, 9, 16, 17
Orion A	05 </I>h32 </I>m47 $.\!\!^{\rm s}$0	-05$^\circ$24$^\prime$24 $^{\prime\prime}$	+8.0	0.5	1	10, 18, 21
OMC-2	05 </I>h32 </I>m58 $.\!\!^{\rm s}$3	-05$^\circ$11$^\prime$52 $^{\prime\prime}$	+10.0	0.5	1,4
OMC-3	05 </I>h32 </I>m48 $.\!\!^{\rm s}$3	-05$^\circ$02$^\prime$10 $^{\prime\prime}$	+10.0	0.5	4
NGC 2023	05 </I>h39 </I>m07 $.\!\!^{\rm s}$0	-02$^\circ$17$^\prime$20 $^{\prime\prime}$	+10.0	0.4	5
NGC 2024	05 </I>h39 </I>m12 $.\!\!^{\rm s}$8	-01$^\circ$57$^\prime$04 $^{\prime\prime}$	+10.0	0.4	5	9, 12, 13
NGC 2068	05 </I>h43 </I>m34 $.\!\!^{\rm s}$9	-00$^\circ$11$^\prime$50 $^{\prime\prime}$	+10.0	0.4	5	15
NGC 2071	05 </I>h44 </I>m30 $.\!\!^{\rm s}$6	+00$^\circ$20$^\prime$42 $^{\prime\prime}$	+10.0	0.4	1, 5	9, 14, 20, 21
Mon R2	06 </I>h05 </I>m22 $.\!\!^{\rm s}$0	-06$^\circ$22$^\prime$25 $^{\prime\prime}$	+10.0	1.0	2
NGC 2264IR	06 </I>h38 </I>m25 $.\!\!^{\rm s}$0	+09$^\circ$32$^\prime$29 $^{\prime\prime}$	+8.0	0.9	1	9
G 34.3 +0.2	18 </I>h50 </I>m46 $.\!\!^{\rm s}$2	+01$^\circ$11$^\prime$13 $^{\prime\prime}$	+58.0	3.7	1,2
W 49N	19 </I>h07 </I>m49 $.\!\!^{\rm s}$9	+09$^\circ$01$^\prime$17 $^{\prime\prime}$	+5.0	11.4	6	6, 20
W 51Na	19 </I>h21 </I>m22 $.\!\!^{\rm s}$4	+14$^\circ$25$^\prime$13 $^{\prime\prime}$	+60.0	7.0	2
DR 21(OH)b	20 </I>h37 </I>m14 $.\!\!^{\rm s}$2	+42$^\circ$12$^\prime$10 $^{\prime\prime}$	-3.0	3.0	1,2
IRAS 21391+5802	21 </I>h39 </I>m10 $.\!\!^{\rm s}$3	+58$^\circ$02$^\prime$29 $^{\prime\prime}$	+0.0	0.8	7	19
S 140	22 </I>h17 </I>m42 $.\!\!^{\rm s}$0	+63$^\circ$03$^\prime$45 $^{\prime\prime}$	-7.0	0.9	8	8, 11, 12, 13, 21
NGC 7538(IRS1)	23 </I>h11 </I>m36 $.\!\!^{\rm s}$5	+61$^\circ$11$^\prime$49 $^{\prime\prime}$	-57.0	2.8	2	20

Distance references: (1) Mangum & Wootten ([1993]), (2) Plume, Jaffe & Evans II ([1992]), (3) Blake et al. ([1995]), (4) Castets & Langer ([1995]), (5) Lada ([1992]), (6) Serabyn, Güsten & Schulz ([1993]), (7) Wilking et al. ([1993]), (8) Zhou et al. ([1994]), SO references: (9) Chernin et al. ([1994]), (10) Friberg ([1984]), (11) Wilner & Welch ([1994]), Multi CS transition references: (12) Mundy et al. ([1986]), (6) Serabyn et al. ([1993]), (13) Snell et al. ([1984a]), (14) Zhou et al. ([1991]), (8) Zhou et al. ([1994]), (16) Langer et al. ([1996]), Molecular outflow references: (3) Blake et al. ([1995]), (9) Chernin et al. ([1994]), (15) Edwards & Snell (1984), (10) Friberg ([1984]), (17) Liseau et al. ([1988]), (18) Olofsson et al. ([1982]), (19) Patel et al. (1995), (20) Scoville et al. ([1986]), (21) Snell et al. ([1984b]), (11) Wilner & Welch ([1994]).
$^a\,$The W 51M core is located approximately at an offset (40 $^{\prime\prime}$, -40 $^{\prime\prime}$) relative to W 51N.
$^b\,$The DR 21 core is located approximately 160 $^{\prime\prime}$south of DR 21(OH).

 

 

Table 2: Integrated intensities in K km s^-1 for certain positions and lines

Source	Offset	SO(32-21)	34SO(32-21)	CS(2-1)	C34S(2-1)
	( $^{\prime\prime}$, $^{\prime\prime}$)
DR21 (OH)	(0,-160)	8.7(0.5)	0.4(0.1)	32.8(0.4)	4.1(0.1)
DR21 (OH)	(0,-40)	21.1(0.5)		49.5(0.4)	7.8(0.1)
DR21 (OH)	(-40,0)	15.2(0.5)		36.6(0.5)	4.4(0.2)
DR21 (OH)	(0,0)	27.8(0.3)	1.4(0.1)	59.6(0.3)	9.0(0.1)
DR21 (OH)	(40,0)	6.5(0.5)		24.0(0.5)	2.2(0.2)
DR21 (OH)	(0,40)	15.4(0.5)		31.4(0.7)	4.2(0.2)
G 34.3+0.2	(0,-40)	12.7(0.8)		38.9(0.5)	6.9(0.6)
G 34.3+0.2	(-40,0)	17.9(1.0)		45.9(0.5)	8.8(0.6)
G 34.3+0.2	(0,0)	24.9(0.3)	1.4(0.1)	62.0(0.3)	12.9(0.2)
G 34.3+0.2	(40,0)	11.4(0.8)		22.4(0.5)	4.2(0.3)
G 34.3+0.2	(0,40)	10.7(0.8)		28.2(0.5)	6.0(0.4)
IRAS 21391+5802	(0,0)	10.1(0.3)	0.5(0.1)	24.5(0.5)	1.6(0.1)
Mon R2	(0,0)	5.6(0.2)		22.4(0.2)	2.9(0.1)
Mon R2	(0,40)	4.7(0.3)	0.1(0.1)	26.5(0.3)	2.7(0.2)
NGC 1333	(120,-200)	4.8(0.3)	0.8(0.1)	6.3(0.2)	0.7(0.1)
NGC 1333	(40,-160)	5.6(0.3)	0.3(0.1)	9.2(0.2)	1.0(0.1)
NGC 1333	(80,-160)	9.3(0.3)	0.9(0.1)	11.7(0.2)	1.0(0.1)
NGC 1333	(120,-160)	8.4(0.1)	1.5(0.1)	6.5(0.1)	1.0(0.1)
NGC 1333	(160,-160)	5.4(0.2)	0.6(0.1)	5.1(0.2)	0.7(0.1)
NGC 1333	(80,-120)	7.8(0.2)	0.7(0.1)	9.3(0.2)	1.6(0.1)
NGC 1333	(120,-120)	6.9(0.2)	0.5(0.1)	7.7(0.2)	1.0(0.1)
NGC 1333	(160,-120)	3.3(0.2)	0.5(0.1)	5.3(0.2)	0.3(0.1)
NGC 1333	(80,-80)	10.2(0.3)	0.7(0.1)	9.2(0.2)	0.7(0.2)
NGC 1333	(120,-80)	5.1(0.3)	0.5(0.2)	6.2(0.2)	0.4(0.1)
NGC 1333	(40,-40)	9.8(0.2)	0.4(0.1)	13.6(0.2)	0.8(0.3)
NGC 1333	(80,-40)	10.1(0.2)	0.9(0.1)	10.9(0.2)	1.3(0.1)
NGC 1333	(120,-40)	7.7(0.3)	0.7(0.1)	7.5(0.2)	0.6(0.1)
NGC 1333	(0,0)	2.4(0.1)	0.1(0.1)	10.6(0.2)	0.9(0.1)
NGC 1333	(80,0)	8.7(0.2)	0.6(0.1)	11.1(0.2)	1.2(0.1)
NGC 1333	(120,0)	5.3(0.3)	0.5(0.1)	7.4(0.1)	0.5(0.1)
NGC 1333	(80,40)	6.2(0.3)	0.6(0.1)	7.3(0.2)	0.3(0.1)
NGC 1333	(120,40)	4.1(0.3)	0.1(0.1)	6.3(0.2)	0.6(0.1)
NGC 1333	(120,80)	2.6(0.3)	0.2(0.1)	6.0(0.2)	0.0(0.1)
NGC 2023	(0,0)	0.8(0.1)		3.7(0.3)	0.1(0.1)
NGC 2024	(0,-40)	10.8(0.3)	0.6(0.1)	40.8(0.9)	4.9(0.2)
NGC 2024	(-40,0)	4.2(0.4)		18.5(0.9)	1.9(0.2)
NGC 2024	(0,0)	9.7(0.2)		31.0(0.5)	4.3(0.1)
NGC 2024	(40,0)	6.3(0.4)		13.6(0.9)	2.3(0.2)
NGC 2024	(0,40)	8.4(0.3)	0.6(0.1)	33.9(0.5)	4.4(0.2)
NGC 2068	(120,-80)	4.1(0.3)	0.3(0.1)	3.3(0.6)	0.1(0.1)
NGC 2068	(0,0)	1.5(0.1)		5.9(0.4)	0.5(0.1)
NGC 2071	(0,0)	2.2(0.2)		11.1(0.3)	1.9(0.1)
NGC 2264IR	(0,-40)	10.2(0.3)		28.0(0.4)	3.4(0.1)
NGC 2264IR	(-40,0)	8.1(0.3)		27.1(0.4)	2.6(0.1)
NGC 2264IR	(0,0)	20.1(0.2)	1.1(0.1)	35.9(0.2)	3.7(0.1)
NGC 2264IR	(40,0)	14.4(0.3)		24.3(0.4)	2.9(0.2)
NGC 2264IR	(0,40)	12.4(0.3)		18.4(0.4)	2.7(0.2)
NGC 7538	(0,-40)	28.8(0.4)	1.4(0.1)	62.1(0.5)	7.5(0.2)
NGC 7538	(-40,0)	9.9(0.6)		30.7(0.6)	2.2(0.2)
NGC 7538	(0,0)	14.9(0.2)	0.8(0.1)	53.4(0.4)	6.3(0.2)
NGC 7538	(40,0)	20.5(0.5)		31.4(0.5)	5.6(0.3)
NGC 7538	(0,40)	6.3(0.6)		12.4(0.5)	1.2(0.1)
OMC-2	(0,0)	2.1(0.1)		14.8(0.3)	1.0(0.1)
OMC-3	(0,0)	6.9(0.3)	0.0(0.1)	11.9(0.5)	1.1(0.1)
Orion A	(0,-80)	13.9(0.3)	0.3(0.3)	63.4(0.8)	12.8(0.4)

a(b) denotes value(1$\sigma$ error).

 

Table 2: continued

Source	Offset	SO(32-21)	34SO(32-21)	CS(2-1)	C34S(2-1)
	( $^{\prime\prime}$, $^{\prime\prime}$)
Orion A	(0,-40)	7.5(0.5)		48.7(0.4)	4.8(0.3)
Orion A	(-40,0)	4.3(0.3)		45.5(0.4)	7.1(0.3)
Orion A	(0,0)	5.9(0.3)		52.4(0.4)	9.2(0.2)
Orion A	(40,0)	5.3(0.3)		17.3(0.5)	2.2(0.3)
Orion A	(0,40)	6.2(0.5)		38.6(0.5)	5.2(0.3)
S 140	(0,-40)	6.1(0.2)		22.2(0.3)	2.0(0.2)
S 140	(-40,0)	12.5(0.2)		27.0(0.3)	3.1(0.2)
S 140	(0,0)	14.0(0.1)	1.8(0.2)	34.8(0.2)	3.9(0.2)
S 140	(40,0)	6.7(0.2)		21.9(0.3)	3.0(0.2)
S 140	(0,40)	13.8(0.3)		31.2(0.4)	3.6(0.2)
W3(IRS4)	(-40,-40)	7.8(0.4)		24.9(0.4)	2.3(0.1)
W3(IRS4)	(0,-40)	17.0(0.3)	0.9(0.1)	50.4(0.4)	6.9(0.2)
W3(IRS4)	(40,-40)	14.2(0.4)		31.2(0.4)	2.7(0.2)
W3(IRS4)	(-40,0)	7.6(0.4)		17.4(0.4)	2.2(0.2)
W3(IRS4)	(0,0)	13.8(0.1)		47.5(0.2)	7.2(0.1)
W3(IRS4)	(40,0)	10.9(0.4)		29.8(0.4)	2.3(0.2)
W3(IRS4)	(-40,40)	3.5(0.3)		9.8(0.3)	0.5(0.2)
W3(IRS4)	(0,40)	3.7(0.4)		16.3(0.4)	2.0(0.2)
W3(IRS4)	(40,40)	3.2(0.4)		16.2(0.4)	0.8(0.2)
W3(OH)	(0,-40)	9.1(0.3)		29.2(0.5)	1.9(0.2)
W3(OH)	(-40,0)	10.2(0.3)		22.0(0.6)	3.1(0.2)
W3(OH)	(-20,0)	16.2(0.4)	1.1(0.1)	42.7(0.6)
W3(OH)	(0,0)	22.1(0.2)	0.9(0.1)	45.2(0.3)	6.1(0.1)
W3(OH)	(40,0)	6.2(0.3)		20.6(0.5)	1.9(0.1)
W3(OH)	(0,40)	6.4(0.3)		28.2(0.5)	2.2(0.2)
W 49N	(0,-40)	11.3(0.5)		27.4(0.4)	3.0(0.2)
W 49N	(-40,0)	17.6(0.4)		46.7(0.4)	7.7(0.2)
W 49N	(0,0)	66.9(0.3)	6.2(0.1)	87.7(0.3)	11.5(0.1)
W 49N	(40,0)	19.8(0.4)		45.7(0.4)	5.9(0.2)
W 49N	(0,40)	12.3(0.4)		36.3(0.3)	5.4(0.2)
W 51N	(-40,-40)	31.8(0.5)		88.8(0.3)	13.6(0.3)
W 51N	(0,-40)	25.6(0.5)		94.7(0.3)	15.5(0.3)
W 51N	(40,-40)	47.4(0.4)	2.7(0.1)	129.2(0.3)	26.6(0.3)
W 51N	(-40,0)	32.4(0.5)		85.8(0.3)	12.4(0.3)
W 51N	(0,0)	32.8(0.4)	1.6(0.1)	90.2(0.2)	14.9(0.2)
W 51N	(40,0)	23.8(0.5)		71.6(0.3)	12.5(0.3)
W 51N	(-40,40)	12.7(0.3)		44.8(0.3)	3.7(0.2)
W 51N	(0,40)	11.6(0.3)		49.7(0.3)	5.2(0.3)
W 51N	(40,40)	10.7(0.4)		40.0(0.3)	5.3(0.3)

a(b) denotes value(1$\sigma$ error).