2005ApJ...625..181R


C.D.S. - SIMBAD4 rel 1.7 - 2021.05.17CEST04:05:57

2005ApJ...625..181R - Astrophys. J., 625, 181-193 (2005/May-3)

An 8.5 GHz Arecibo survey of carbon recombination lines toward ultracompact H II regions: physical properties of dense molecular material.

ROSHI D.A., BALSER D.S., BANIA T.M., GOSS W.M. and DE PREE C.G.

Abstract (from CDS):

We report here on a survey of carbon recombination lines (RLs) near 8.5 GHz toward 17 ultracompact H II regions (UCHs). Carbon RLs are detected in 11 directions, indicating the presence of dense photodissociation regions (PDRs) associated with the UCHs. In this paper, we show that the carbon RLs provide important, complementary information on the kinematics and physical properties of the ambient medium near UCHs. Non-LTE models for the carbon line-forming region are developed, assuming that the PDRs surround the UCHs, and we constrained the model parameters by multifrequency RL data. Modeling shows that carbon RL emission near 8.5 GHz is dominated by stimulated emission, and hence we preferentially observe the PDR material that is in front of the UCH continuum. We find that the relative motion between ionized gas and the associated PDR is about half that estimated earlier, and it has an rms velocity difference of 3.3 km/s. Our models also give estimates for the PDR density and pressure. We found that the neutral density of PDRs is typically >5x105/cm3, and UCHs can be embedded in regions with high ambient pressure. Our results are consistent with a pressure-confined H II region model in which the stars are moving relative to the cloud core. Other models cannot be ruled out, however. Interestingly, in most cases, the PDR pressure is an order of magnitude larger than the pressure of the ionized gas. Further investigation is needed to understand this large pressure difference.

Abstract Copyright:

Journal keyword(s): ISM: H II Regions - ISM: General - Line: Formation - Radio Lines: ISM - Stars: Formation - Surveys

Simbad objects: 24

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Number of rows : 24

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 2C 1590 BLL 18 45 37.60 +09 53 44.0           ~ 72 1
2 [KCW94] 032.797+00.191 Rad 18 50 30.709 -00 01 58.13           ~ 3 0
3 OH 34.26 +0.15 SFR 18 53 18.54 +01 14 57.9           ~ 473 0
4 AGAL G035.579-00.031 cor 18 56 22.6865 +02 20 19.057           ~ 30 0
5 3C 394 Rad 18 59 23.36 +12 59 12.1           ~ 54 1
6 [WC89] 035.20-1.74 HII 19 01 46.4 +01 13 25           ~ 12 0
7 [KCW94] 035.200-01.741 Rad 19 01 46.497 +01 13 24.52           ~ 2 0
8 GAL 035.19-01.75 HII 19 01 47.4 +01 13 00           ~ 22 0
9 [KB94] 38 HII 19 01 53.2 +04 12 43           ~ 8 0
10 [WBH2005] G041.742+0.096 HII 19 07 15.5 +07 52 43           ~ 22 2
11 W 49a SFR 19 10 15.7 +09 06 05           ~ 267 2
12 W 49 SFR 19 10 20 +09 07.7           ~ 524 1
13 [KCW94] 043.237-00.045 Rad 19 10 33.524 +09 08 25.11           ~ 5 0
14 Caswell OH 045.12+00.13 HII 19 13 27.845 +10 53 36.74           ~ 114 0
15 GAL 045.5+00.0 HII 19 14 20.8 +11 09 04           ~ 138 0
16 [GPD88] 045.454+0.060 HII 19 14 21.3 +11 09 13           ~ 151 1
17 GAL 043.89-00.78 HII 19 14 26.16 +09 22 34.0           ~ 50 0
18 GAL 048.61+00.02 HII 19 20 31.3 +13 55 24           ~ 51 0
19 GAL 050.32+00.68 HII 19 21 27.55 +15 44 21.3           ~ 8 0
20 SH 2-87 HII 19 46 20.7 +24 35 15           ~ 152 2
21 SH 2-88 B HII 19 46 47.329 +25 12 45.62           ~ 154 2
22 W 58a HII 20 01 45.8 +33 32 43           ~ 278 4
23 [KC97c] G070.3+01.6 HII 20 01 46.8 +33 33 05           ~ 9 0
24 3C 410 QSO 20 20 06.5624875736 +29 42 14.183853306   19.5       ~ 109 0

    Equat.    Gal    SGal    Ecl

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2021.05.17-04:05:57

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