1995A&A...302..521C

Query : 1995A&A...302..521C

1995A&A...302..521C - Astronomy and Astrophysics, volume 302521-527 (1995/10-2)

H2O masers without associated diffuse HII regions: an earlier evolutionary phase?

CODELLA C. and FELLI M.

Abstract (from CDS):

In apparent contrast with the common belief that galactic H2O masers are always found associated with HII regions, the majority (80%) of H2O masers are without diffuse HII regions. The aim of this work is to confirm the lack of diffuse ionized gas around these masers, and to see if these sources represent a homogeneous sub-class in an earlier evolutionary phase in which a diffuse HII region has not yet formed. We present the results of a search for H89α (3 cm) hydrogen recombination line towards a sub-sample of 60 of these masers. The detection rate is very low: only 2 sources (3%) show recombination line emission. In order to explain this low detection rate, we have examined possible selection effects, such as sensitivity of the recombination line observations, or lack of ionized gas because of the low luminosity of the associated star. Although both effects can play some role, by no means can they account for the large number of masers without associated diffuse HII regions. The most probable answer is that masers form very early, much before the formation of a diffuse HII region, and spend most of their life in this evolutionary stage. The 20% positional agreement between HII regions and water masers found in low resolution (arcmin) surveys may indicate that maser emission continues for a fraction of the main-sequence life-time of the newly formed star. Alternatively (and more probably), this coincidence may reflect that more than one star-formation event (i.e. the formation of a new maser) occurs in a stellar cluster and that these are spread over an extended period, longer than that required by the first massive stars of the cluster to develop their own HII regions.

Abstract Copyright: ∼

Journal keyword(s): masers - stars: formation - HII regions - radio lines: ISM

Nomenclature: Table 1: [CF95] NN (Nos 1-60)

CDS comments: Table 1: WB = WB89, p. 524 : WB89 621 misprint for 261

Simbad objects: 115

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Number of rows : 115
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 IRAS 00420+5530 Y*? 00 44 57.31 +55 47 18.1           ~ 61 0
2 [PBC91] B004205.3+553054 Mas 00 44 57.5 +55 47 18           ~ 3 0
3 GAL 125.63+02.02 Mas 01 16 47.32 +64 45 42.6           ~ 19 0
4 RAFGL 5077 HII 02 43 28.62213 +62 57 08.7770           ~ 77 0
5 [CF95] 3 Mas 02 43 29.1 +62 56 59           ~ 1 0
6 IRAS 02485+6902 * 02 53 06.31656 +69 14 36.6828           ~ 15 0
7 [CF95] 5 Mas 03 27 38.1 +30 12 59           ~ 1 0
8 NAME LDN 1455 IRS 1 cor 03 27 39.08 +30 13 03.1           ~ 173 0
9 RAFGL 5113 Or* 04 10 11.8514463792 +50 59 54.681713664           ~ 29 0
10 SH 2-209 HII 04 11 06.7 +51 09 44           ~ 105 0
11 IRAS 04579+4703 Y*O 05 01 39.661 +47 07 21.92           ~ 51 0
12 IRAS 05137+3919 Cld 05 17 13.3 +39 22 14           ~ 75 0
13 GAL 174.20-00.08 Cld 05 30 45.9 +33 47 56           ~ 210 2
14 [CF95] 9 Mas 05 30 48.8 +33 47 26           ~ 1 0
15 NGC 1985 RNe 05 37 47.8 +31 59 24           ~ 145 2
16 [CF95] 10 Mas 05 37 53.1 +31 59 35           ~ 1 0
17 GAL 192.16-03.82 HII 05 58 13.4 +16 32 00           ~ 145 1
18 [PBC91] B055520.3+163146 Mas 05 58 13.9 +16 32 00           ~ 4 0
19 RAFGL 6366S HII 06 08 41.0 +21 31 01           ~ 95 0
20 [PBC91] B060607.3+215112 Mas 06 09 07.8 +21 50 39           ~ 3 0
21 IRAS 06061+2151 SFR 06 09 07.8 +21 50 39           ~ 87 0
22 [CF95] 13 Mas 06 52 45.5 +01 40 15           ~ 1 0
23 IRAS 06501+0143 HII 06 52 46.18 +01 40 19.0           ~ 22 0
24 [CF95] 14 Mas 07 23 01.3 -14 41 32           ~ 1 0
25 IRAS 07207-1435 HII 07 23 01.8935434392 -14 41 38.218885080           ~ 20 0
26 IRAS 07422-2001 HII 07 44 28.2367 -20 08 30.606           ~ 24 0
27 OH 000.55-00.85 Mas 17 50 14.35 -28 54 31.1           ~ 34 0
28 RCW 142 HII 17 50 15.3 -28 54 03           ~ 64 0
29 OH 004.827+00.231 Mas 17 55 48.880 -24 40 18.77           ~ 3 0
30 IRAS 17527-2439 HII 17 55 49.1 -24 40 20           ~ 18 0
31 [CF95] 18 Mas 18 01 18.0 -22 34 57           ~ 1 0
32 IRAS 17582-2234 Y*O 18 01 18.52464 -22 34 57.5364           ~ 18 0
33 IRAS 18024-2119 IR 18 05 25.4 -21 19 41           ~ 17 0
34 [CF95] 19 Mas 18 05 25.4 -21 19 40           ~ 1 0
35 [CF95] 20 Mas 18 07 51.5 -20 18 36           ~ 2 0
36 IRAS 18048-2019 HII 18 07 51.6 -20 18 36           ~ 20 1
37 [WBH98] 18048-2019 HII 18 07 51.7 -20 18 35           ~ 17 0
38 AGAL G012.418+00.506 cor 18 10 51.09792 -17 55 49.6272           ~ 74 0
39 [BE83] Maser 012.42+00.50 Mas 18 10 51.8 -17 55 56           ~ 10 0
40 GAL 012.89+00.49 HII 18 11 51.3 -17 31 29           ~ 217 0
41 OH 012.889+00.489 Mas 18 11 51.4450 -17 31 29.412           ~ 48 0
42 W 33b SFR 18 13 54.68 -18 01 48.1           ~ 85 0
43 OH 012.68-00.18 Mas 18 13 54.7457 -18 01 46.588           ~ 49 0
44 IRAS 18134-1942 HII 18 16 22.1327 -19 41 27.219           ~ 72 0
45 [PBC91] B181429.7-172322 Mas 18 17 24.3 -17 22 12           ~ 2 0
46 IRAS 18144-1723 IR 18 17 24.4 -17 22 13           ~ 35 0
47 GAL 013.66-00.60 Mas 18 17 24.9 -17 22 12           ~ 8 0
48 GRS G013.66 -00.60 Rad 18 17 24.9 -17 22 12           ~ 3 0
49 IRAS 18152-1346 Y*O 18 18 07.5 -13 45 06           ~ 13 0
50 [CF95] 28 Mas 18 18 09.5 -13 45 17           ~ 1 0
51 GAL 014.23-00.51 Mas 18 18 12.7 -16 49 34           ~ 7 0
52 IRAS 18153-1651 IR 18 18 16.0 -16 50 39           ~ 22 0
53 GAL 014.33-00.64 HII 18 18 53.5 -16 47 39           ~ 75 0
54 [CF95] 29 Mas 18 18 53.8 -16 47 50           ~ 2 0
55 [BE83] Maser 014.33-00.64 cor 18 18 54.6744 -16 47 50.264           ~ 24 0
56 GAL 019.36-00.02 HII 18 26 24.3 -12 03 47           ~ 39 0
57 [CF95] 30 Mas 18 26 24.3 -12 03 46           ~ 1 0
58 [CF95] 31 Mas 18 29 05.8 +00 30 36           ~ 1 0
59 IRAS 18265+0028 cor 18 29 06.694 +00 30 31.24           ~ 17 0
60 LDN 379 DNe 18 30 34.0 -15 15 10           ~ 35 0
61 [XT92] 6 Mas 18 30 35.0 -15 14 36           ~ 15 0
62 IRAS 18277-1516 FIR 18 30 35.3 -15 14 38           ~ 27 0
63 [CF95] 32 Mas 18 30 35.3 -15 14 38           ~ 1 0
64 [HLB98] SEST 169 Mas 18 34 19.7 -05 59 43           ~ 4 0
65 RAFGL 7009S HII 18 34 20.911 -05 59 42.23           ~ 231 0
66 OH 024.7+00.3 OH* 18 35 29.21616 -07 13 10.9740           O-rich 40 0
67 IRAS 18359-0334 Mas 18 38 34.4 -03 32 06           ~ 9 0
68 SH 2-76 W HII 18 55 57.5 +07 53 03           ~ 11 0
69 [BE83] Maser 040.48+02.59 Mas 18 55 58.7 +07 53 42           ~ 3 0
70 GAL 035.2-00.74 cor 18 58 13.00 +01 40 36.0           ~ 176 0
71 OH 035.2-00.7 Mas 18 58 13.0517 +01 40 35.674           ~ 49 0
72 IRAS 18556+0136 mul 18 58 13.1 +01 40 35           ~ 142 0
73 [PBC91] B190435.3+081358 Mas 19 06 59.7 +08 18 42           ~ 2 0
74 [BNM96] 042.096+0.354 Y*O 19 07 00.527 +08 18 44.48           ~ 17 0
75 [PBC91] B190852.3+090225 Mas 19 11 15.8 +09 07 27           ~ 4 0
76 IRAS 19088+0902 Rad 19 11 15.9 +09 07 27           ~ 22 0
77 [PBC91] B190913.4+084127 Mas 19 11 37.3 +08 46 30           ~ 2 0
78 IRAS 19092+0841 Rad 19 11 37.4 +08 46 30           ~ 30 0
79 [CF95] 41 Mas 19 32 31.7 +16 57 33           ~ 2 0
80 [BNM96] 052.660-1.090 HII 19 32 32.3027695224 +16 57 34.130933064           ~ 11 0
81 [PBC91] B193726.4+235257 Mas 19 39 33.2 +23 59 55           ~ 2 0
82 MSX6C G059.6032+00.9116 HII 19 39 34.8 +23 59 51           ~ 22 0
83 MSX6C G059.7831+00.0648 Y*O 19 43 11.2464 +23 44 03.270           ~ 159 0
84 IRAS 19410+2336 SFR 19 43 11.5 +23 44 06           ~ 160 0
85 IRAS 19474+2637 IR 19 49 32.2352001912 +26 45 26.312895432           ~ 12 0
86 [CF95] 44 Mas 19 49 32.6 +26 45 14           ~ 1 0
87 IRAS 20050+2720 Y*O 20 07 06.549 +27 28 49.10           ~ 107 0
88 [HLB98] Onsala 117 Mas 20 07 06.7 +27 28 53           ~ 3 0
89 NAME IRAS 20050+2720 Cluster Cl* 20 07 06.7 +27 28 53           ~ 83 0
90 IRAS 20056+3350 Mas 20 07 31.5 +33 59 39           ~ 30 0
91 IRAS 20110+3321 HII 20 12 57.87840 +33 30 26.8344           ~ 20 0
92 [CF95] 47 Mas 20 13 01.9 +33 30 17           ~ 1 0
93 IRAS 20126+4104 Y*O 20 14 25.8816769656 +41 13 36.879427236           B2.5-B0.5 469 0
94 IRAS 20227+4154 HII 20 24 31.4 +42 04 17           ~ 32 0
95 [CF95] 49 Mas 20 24 31.4 +42 04 17           ~ 1 0
96 IRAS 21144+5430 HII 21 15 55.636 +54 43 31.01           ~ 28 0
97 [CF95] 50 Mas 21 15 55.9 +54 43 31           ~ 1 0
98 SH 2-128 HII 21 32 09.9 +55 52 53           ~ 173 1
99 GAL 097.52+03.17 Mas 21 32 13.09 +55 52 55.8           ~ 5 0
100 IRAS 21307+5049 Y*O 21 32 30.59280 +51 02 16.0368           ~ 49 0
101 [CF95] 52 Mas 21 32 31.5 +51 02 22           ~ 1 0
102 IRAS 21553+5908 HII 21 56 59.209 +59 22 39.38           ~ 11 0
103 [CF95] 53 Mas 21 56 59.4 +59 22 38           ~ 1 0
104 LDN 1204A HII 22 21 26.68 +63 51 38.2           ~ 120 0
105 [CF95] 54 Mas 22 21 27.6 +63 51 45           ~ 2 0
106 LDN 1204B DNe 22 21 30.2 +63 36 23           ~ 27 0
107 [CF95] 55 Mas 22 21 33.3 +63 37 21           ~ 2 0
108 [CF95] 56 Mas 22 52 36.9 +60 00 48           ~ 4 0
109 [CF95] 57 Mas 22 56 17.8 +62 01 47           ~ 3 0
110 NAME Cepheus A SFR 22 56 17.9 +62 01 49           ~ 760 2
111 [BNM96] 109.098-0.346 HII 22 59 05.5344256224 +59 28 23.280817692           ~ 45 0
112 [CF95] 58 Mas 22 59 06.4 +59 28 28           ~ 1 0
113 IRAS 23004+5642 Cld 23 02 35.0 +56 58 54           ~ 28 0
114 SH 2-159 Y*O 23 15 31.2384366062 +61 07 10.181362705           ~ 188 1
115 IRAS 23151+5912 HII 23 17 21.0 +59 28 49           ~ 102 0

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