2009MNRAS.394..900C

Query : 2009MNRAS.394..900C

2009MNRAS.394..900C - Mon. Not. R. Astron. Soc., 394, 900-915 (2009/April-1)

Unveiling the birth and evolution of the HII region Sh2-173.

CICHOWOLSKI S., ROMERO G.A., ORTEGA M.E., CAPPA C.E. and VASQUEZ J.

Abstract (from CDS):

Based on a multiwavelength study, the interstellar medium around the Hii region Sh2-173 has been analysed. The ionized region is clearly detected in the optical and the radio continuum images. The analysis of the Hi data shows a region of low emissivity that has an excellent morphological correlation with the radio continuum emission. The Hii region is partially bordered by a photodissociation region, which, in turn, is encircled by a molecular structure. The Hi and CO structures related to Sh2-173 are observed in the velocity ranges from -25 to -31 km/s and from -27 to -39 km/s, respectively. Taking into account the presence of non-circular motions in the Perseus spiral arm, together with previous distance estimates for the region, we adopt a distance of 2.5±0.5 kpc for Sh2-173. Seven hot stars were identified in the field of Sh2-173, being only one O-type star. The amount of energetic photons emitted by this star is enough to keep the region ionized and heat the dust. Given that an expanding Hii region may trigger star formation, a search for young stellar object (YSO) candidates was made using different infrared point source catalogues. A population of 46 YSO candidates was identified, projected on to the molecular clouds.

On the other hand, Sh2-173 is located in a dense edge of a large (∼5°) Hi shell, GSH117.8+1.5-35. The possibility of Sh2-173 being part of a hierarchical system of three generations is suggested. In this scenario, the large Hi shell, which probably originated due to the action of CasOB5, would have triggered the formation of Sh2-173, which, in turn, is triggering new stars in its surrounding molecular cloud. To test this hypothesis, the ages of both the Hii region and the large shell were estimated and compared. We concluded that Sh2-173 is a young Hii region of about 0.6-1.0 Myr old. As for the large shell, we obtained a dynamical age of 5±1 Myr. These age estimates, together with the relative location of the different structures, support the hypothesis that Sh2-173 is part of a hierarchical system.


Abstract Copyright: © 2009 The Authors. Journal compilation © 2009 RAS

Journal keyword(s): stars: formation - Hii regions - ISM: individual: Sh2-173 - ISM: kinematics and dynamics

VizieR on-line data: <Available at CDS (J/MNRAS/394/900): table6.dat>

Nomenclature: Table 6: [CRO2009] NN (Nos 1-46). Fig. 7: [CRO2009] Cloud A (Nos A-B). Fig. 9: [CRO2009] gN (Nos g1-G4).

Status at CDS : All or part of tables of objects could be ingested in SIMBAD with priority 2. // All or part of tables of objects will not be ingested in SIMBAD.

Simbad objects: 44

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Number of rows : 44
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 GIRL G117+00 IR 00 00 +63.2           ~ 2 0
2 NGC 7822 HII 00 01 08.58 +67 25 17.0           ~ 121 3
3 LBN 117.62+02.29 HII 00 01 29 +64 39.0           ~ 41 0
4 HD 108 SB* 00 06 03.3890541936 +63 40 46.771220928 6.79 7.58 7.40     O4-8f?p 338 0
5 SH 2-172 HII 00 15 29.1 +61 14 41           ~ 30 0
6 LBN 119.57-00.92 HII 00 21 16 +61 43.5           ~ 39 0
7 LS I +61 137 * 00 21 27.1454351136 +61 44 12.978553380 11.6 11.98 11.42     B0.5V 15 0
8 LS I +61 139 * 00 21 52.1405541288 +61 45 26.839797480 11.75 12.20 11.82     B2IV 16 0
9 BD+60 39 * 00 21 53.8989746616 +61 45 02.610093816 9 9.66 9.46     O9V 45 0
10 LS I +61 142 * 00 22 04.9572905808 +61 33 57.707236404 10.38 10.97 10.64     B0.5V 11 0
11 LS I +61 143 * 00 22 12.7866684576 +61 44 40.511322276 12.17 12.66 12.39     B2V 10 0
12 BD+60 42 * 00 22 19.6950696984 +61 39 10.348394976 9.91 10.39 10.17     B2IV 15 0
13 LS I +61 145 EB* 00 22 26.5161565656 +61 49 39.754219728 10.75 11.3 10.9     B1V 20 0
14 SN 1572A SN* 00 25 21.5 +64 08 27           B8 1254 1
15 PN BV 2 PN 00 40 21.614 +62 51 34.28     21.5     ~ 37 0
16 SH 2-180 HII 00 48.8 +62 55           ~ 11 0
17 LBN 122.92+02.39 HII 00 49 22.0 +65 15 37           ~ 17 0
18 Ass Cas OB 7 As* 00 50 14 +64 04.3           ~ 65 0
19 SH 2-182 HII 00 50.3 +64 44           ~ 12 0
20 RRF 1343 HII 02 20 05.6 +61 07 04           ~ 38 1
21 IC 1795 HII 02 25 43.5 +62 06 13           ~ 247 0
22 W 3 MoC 02 27 04.10 +61 52 27.1           ~ 1064 3
23 NAME Heart Nebula HII 02 32.7 +61 27           ~ 336 1
24 NAME Per Arm PoG 03 30 +45.0           ~ 1672 0
25 GSH 263-02+45 sh 08 37 -44.           ~ 8 0
26 Cl Bochum 7 OpC 08 44 28.2 -45 55 19   6.94 6.8     ~ 52 0
27 NAME Cepheus Bubble PoC 21 44 +61.7           ~ 39 0
28 Ass Cep OB 2 As* 21 51 +60.0           ~ 303 0
29 LBN 113.53-00.67 HII 23 32 57.9 +60 48 01           ~ 38 0
30 SH 2-167 HII 23 35 30 +64 52.3     14.5     ~ 24 2
31 SNR G114.3+00.3 SNR 23 37 05.780 +61 51 01.69           ~ 130 1
32 LBN 113.05-04.51 HII 23 38 23.7 +59 58 40           ~ 24 0
33 LBN 114.55+00.22 HII 23 39.8 +61 56           ~ 38 0
34 LBN 114.63-00.85 HII 23 40 11 +60 57.6           ~ 17 0
35 BD+62 2296B WR* 23 47 20.3859297600 +63 13 14.245862124   11.92 11.11     WN4 7 0
36 BD+62 2299 * 23 48 04.4658884280 +63 23 50.911432620 9.72 10.07 9.6     O8II(f) 31 0
37 BD+61 2550 * 23 52 19.5384794064 +62 07 06.592403604 8.99 9.58 9.4     O9.5II 41 0
38 LBN 115.71-01.61 HII 23 52 56.5 +60 29 04           ~ 41 0
39 SNR G116.5+01.1 SNR 23 53 42.000 +63 15 00.00           ~ 74 0
40 BD+61 2559 * 23 53 43.8362132688 +62 25 24.641529312 9.35 9.96 9.8     O9V 41 0
41 SH 2-169 HII 23 54.0 +60 22           ~ 22 0
42 Ass Cas OB 5 As* 23 54 +61.6           ~ 78 0
43 CTB 1 SNR 23 59 13 +62 26.2           ~ 173 0
44 NAME HI Supershell in Perseus Arm PoC ~ ~           ~ 3 1

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