2014A&A...566A..78E


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.13CEST06:39:37

2014A&A...566A..78E - Astronomy and Astrophysics, volume 566A, 78-78 (2014/6-1)

Herschel spectral mapping of the Helix nebula (NGC 7293). Extended CO photodissociation and OH+ emission.

ETXALUZE M., CERNICHARO J., GOICOECHEA J.R., VAN HOOF P.A.M., SWINYARD B.M., BARLOW M.J., VAN DE STEENE G.C., GROENEWEGEN M.A.T., KERSCHBAUM F., LIM T.L., LIQUE F., MATSUURA M., PEARSON C., POLEHAMPTON E.T., ROYER P. and UETA T.

Abstract (from CDS):

The Helix nebula (NGC7293) is our closest planetary nebulae. Therefore, it is an ideal template for photochemical studies at small spatial scales in planetary nebulae. We aim to study the spatial distribution of the atomic and the molecular gas, and the structure of the photodissociation region along the western rims of the Helix nebula as seen in the submillimeter range with Herschel. We used five SPIRE FTS pointing observations to make atomic and molecular spectral maps. We analyzed the molecular gas by modeling the CO rotational lines using a non-local thermodynamic equilibrium (non-LTE) radiative transfer model. For the first time, we have detected extended OH+ emission in a planetary nebula. The spectra towards the Helix nebula also show COemission lines (from J=4 to 8), [NII] at 1461 GHz from ionized gas, and [CI] (3P2-3P1), which together with the OH+ lines trace extended CO photodissociation regions along the rims. The estimated OH+ column density is ∼1012-1013cm–2. The CH+ (1-0) line was not detected at the sensitivity of our observations. Non-LTE models of the CO excitation were used to constrain the average gas density (n(H2)~(1-5)x105cm–3) and the gas temperature (Tk∼20-40K). The SPIRE spectral-maps suggest that CO arises from dense and shielded clumps in the western rims of the Helix nebula, whereas OH+ and [CI] lines trace the diffuse gas and the UV and X-ray illuminated clump surfaces where molecules reform after CO photodissociation. The [NII] line traces a more diffuse ionized gas component in the interclump medium.

Abstract Copyright:

Journal keyword(s): planetary nebulae: individual: NGC7293 - infrared: ISM - photon-dominated region (PDR) - ISM: molecules - ISM: lines and bands

CDS comments: Table 3 knots not in SIMBAD.

Simbad objects: 13

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Number of rows : 13

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 M 77 GiP 02 42 40.771 -00 00 47.84 9.70 9.61 8.87 10.1 9.9 ~ 4093 2
2 RAFGL 618 pA* 04 42 53.6245215366 +36 06 53.397219192   16.32   12.59   C-rich 954 0
3 NAME Orion-KL SFR 05 35 14.16 -05 22 21.5           ~ 2001 1
4 NAME Orion Bright Bar reg 05 35 22.30 -05 24 33.0           ~ 716 0
5 NGC 3188 rG 10 19 42.8148398020 +57 25 24.353375798   14.7       ~ 44 0
6 NAME Sgr A* X 17 45 40.03599 -29 00 28.1699           ~ 3452 3
7 NAME Sgr B2 MoC 17 47 20.4 -28 23 07           ~ 1909 1
8 NGC 6445 PN 17 49 15.21 -20 00 34.5   18.9       ~ 284 0
9 M 57 PN 18 53 35.0969571234 +33 01 44.883146221   15.405 15.769 15.901 16.062 DA(O?) 790 2
10 NGC 6781 PN 19 18 28.085 +06 32 19.29     11.8     ~ 248 0
11 M 27 PN 19 59 36.3632092274 +22 43 16.312364964   13.749 14.089 14.247 14.405 DAO.6 566 0
12 NGC 7027 PN 21 07 01.8 +42 14 10   9.1 10.9     ~ 2323 1
13 NGC 7293 PN 22 29 38.5453078023 -20 50 13.746093105 11.894 13.158 13.524 13.689 13.898 DAO.5 896 0

    Equat.    Gal    SGal    Ecl

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2020.07.13-06:39:37

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