1999A&AS..136..333C


C.D.S. - SIMBAD4 rel 1.7 - 2020.02.17CET17:58:18

1999A&AS..136..333C - Astron. Astrophys., Suppl. Ser., 136, 333-361 (1999/April-2)

High density molecular clumps around protostellar candidates.

CESARONI R., FELLI M. and WALMSLEY C.M.

Abstract (from CDS):

There are several indications that strong H2O maser emission arises at the very beginning of the evolution of a massive star and disappears when an Hii region becomes detectable in the radio continuum. If this is the case, one expects to find dense hot molecular gas surrounding embedded far IR sources coincident with H2O masers. In order to test this hypothesis, we have used the Pico Veleta 30-m radiotelescope to search for molecular line emission towards a sample of 12 H2O masers located in regions of massive star formation, but not directly associated with bright compact radio Hii regions, with the intention to identify the sites of newly born massive (proto)stars in their earliest stages and to study their properties. Our main goals were: a) to confirm the hypothesis that the H2O masers not associated with compact radio continuum emission are indeed located at the centre of high density clumps within a molecular cloud; b) to use several molecular transitions (namely: 13CO(2-1), CS(3-2), C34S(2-1), C34S(3-2), C34S(5-4), HCN(1-0), CH3CN(8-7), CH3CN(12-11), HCO+(1-0), CH3OH(3-2), CH3OH(5-4)) in order to derive information on the size, kinematics, temperature, density, and ionisation degree of the molecular gas in the places where star formation has just begun, as well as to search for the presence of outflows on scale sizes of 10"-30". In this paper we present the large amount of data obtained at Pico Veleta in a compressed way, but still sufficiently ample to give usable informations for further studies. General results from a first analysis of the data are also presented. Our first goal is amply verified since in all cases and in molecules tracing high density gas we find a barely resolved peak at the position of the maser, confirming the validity of our selection criteria. Our sample thus provides a valid reference list of regions of massive star formation in their earliest phases. As far as the second goal is concerned, the large variety of intensity ratios of different molecules, as well as of other derived parameters, point out that the molecular clumps where star formation is taking place are far from identical and that chemical evolution and influence of the newborn star may amply affect the line intensity ratios. In some cases small scale (seconds of arc) outflows were detected, not necessarily related to the minute of arc scale outflows present in the same regions. More detailed studies of each region are presented in separate papers.

Abstract Copyright:

Journal keyword(s): ISM: clouds - ISM: molecules - radio lines: interstellar

Simbad objects: 28

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Number of rows : 28

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 NGC 281 HII 00 52 25.1 +56 33 54           ~ 228 1
2 NAME W 3 OH HII 02 27 04.1 +61 52 22           ~ 935 2
3 GAL 174.20-00.08 Cld 05 30 45.9 +33 47 56           ~ 182 2
4 SH 2-233 HII 05 38 31.5 +35 51 19           ~ 59 1
5 IRAS 05358+3543 mul 05 39 10.4 +35 45 19           ~ 132 1
6 NAME SH 2-233 IR Cl* 05 39 10.4 +35 45 19           ~ 93 0
7 CPM 19 Y*O 05 40 24.4 +23 50 54           ~ 48 0
8 GGD 4 HH 05 40 25 +23 50.9           ~ 41 0
9 SH 2-235 B HII 05 40 52.366 +35 41 29.43   17       ~ 171 1
10 BFS 46 HII 05 40 52.90 +35 42 16.7           ~ 49 0
11 SH 2-235 HII 05 41.1 +35 50           ~ 184 0
12 NAME Mon R2 HII 06 07 46.6 -06 22 59           ~ 642 2
13 Ass Mon R 2 As* 06 07 47.8 -06 22 55           ~ 46 1
14 GGD 15 HH 06 10.8 -06 11           ~ 47 1
15 NGC 2183 HII 06 10 50.2 -06 12 01           ~ 72 0
16 GGD 12 HH 06 10 50.6 -06 11 50           ~ 59 1
17 NAME GGD 12-15 Cl* 06 10 51.0 -06 11 54           ~ 78 1
18 NAME Mon I MoC 06 35 +10.1           ~ 206 0
19 NGC 2264 OpC 06 40 58 +09 53.7     3.9     ~ 1564 1
20 RAFGL 989 Y*O 06 41 10.1592954288 +09 29 33.635497596   17.4 16.8 18.26 17.28 B2 237 0
21 NAME Mon OB1 C PoC 06 41 11 +09 29.1           ~ 46 1
22 IRAS 20126+4104 Y*O 20 14 25.8816186803 +41 13 36.869078243           B2.5-B0.5 392 0
23 IC 1396 OpC 21 39 00 +57 29.4           ~ 442 1
24 [BGE2002] BIMA 2 Y*O 21 40 42.36 +58 16 09.7           ~ 114 0
25 NAME IC 1396 North CGb 21 40 42.6537 +58 16 01.882           ~ 182 1
26 LDN 1204A DNe 22 21 22.5 +63 51 13           ~ 87 0
27 LDN 1204 DNe 22 26.7 +63 15           ~ 84 1
28 IRAS 23151+5912 HII 23 17 21.0 +59 28 49           ~ 90 0

    Equat.    Gal    SGal    Ecl

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