eprintid: 1427243
rev_number: 37
eprint_status: archive
userid: 608
dir: disk0/01/42/72/43
datestamp: 2014-04-19 18:50:41
lastmod: 2021-09-20 00:06:50
status_changed: 2014-04-19 18:50:41
type: article
metadata_visibility: show
item_issues_count: 0
creators_name: Etxaluze, M
creators_name: Cernicharo, J
creators_name: Goicoechea, JR
creators_name: Van Hoof, PAM
creators_name: Van De Steene, GC
creators_name: Groenewegen, MAT
creators_name: Swinyard, BM
creators_name: Barlow, MJ
creators_name: Matsuura, M
creators_name: Lim, TL
creators_name: Pearson, C
creators_name: Polehampton, ET
creators_name: Kerschbaum, F
creators_name: Lique, F
creators_name: Royer, P
creators_name: Ueta, T
title: Herschel spectral mapping of the Helix nebula (NGC 7293): Extended CO photodissociation and OH+ emission
ispublished: pub
divisions: UCL
divisions: B04
divisions: C06
divisions: F60
note: Reproduced with permission from Astronomy & Astrophysics, © ESO
abstract: Context. The Helix nebula (NGC 7293) is our closest planetary nebulae. Therefore, it is an ideal template for photochemical studies at small spatial scales in planetary nebulae. Aims. 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. Methods. 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. Results. For the first time, we have detected extended OH emission in a planetary nebula. The spectra towards the Helix nebula also show CO emission lines (from J = 4 to 8), [N ii] at 1461 GHz from ionized gas, and [C i] (P- P), which together with the OH lines trace extended CO photodissociation regions along the rims. The estimated OH column density is ~ 10 - 10 cm . 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(H) ~ (1 - 5) × 10 cm) and the gas temperature (T ~ 20-40 K). Conclusions. The SPIRE spectral-maps suggest that CO arises from dense and shielded clumps in the western rims of the Helix nebula, whereas OH and [C i] lines trace the diffuse gas and the UV and X-ray illuminated clump surfaces where molecules reform after CO photodissociation. The [N ii] line traces a more diffuse ionized gas component in the interclump medium. © ESO, 2014.
date: 2014-06
official_url: http://dx.doi.org/10.1051/0004-6361/201322941
vfaculties: VMPS
oa_status: green
full_text_type: pub
language: eng
primo: open
primo_central: open_green
verified: verified_manual
elements_source: Scopus
elements_id: 941603
doi: 10.1051/0004-6361/201322941
lyricists_name: Barlow, Michael
lyricists_name: Matsuura, Mikako
lyricists_name: Swinyard, Bruce
lyricists_id: MJBAR75
lyricists_id: MMATS97
lyricists_id: BSWIN93
full_text_status: public
publication: Astronomy and Astrophysics
volume: 566
article_number: A78
issn: 0004-6361
citation:        Etxaluze, M;    Cernicharo, J;    Goicoechea, JR;    Van Hoof, PAM;    Van De Steene, GC;    Groenewegen, MAT;    Swinyard, BM;                                     ... Ueta, T; + view all <#>        Etxaluze, M;  Cernicharo, J;  Goicoechea, JR;  Van Hoof, PAM;  Van De Steene, GC;  Groenewegen, MAT;  Swinyard, BM;  Barlow, MJ;  Matsuura, M;  Lim, TL;  Pearson, C;  Polehampton, ET;  Kerschbaum, F;  Lique, F;  Royer, P;  Ueta, T;   - view fewer <#>    (2014)    Herschel spectral mapping of the Helix nebula (NGC 7293): Extended CO photodissociation and OH+ emission.                   Astronomy and Astrophysics , 566     , Article A78.  10.1051/0004-6361/201322941 <https://doi.org/10.1051/0004-6361%2F201322941>.       Green open access   
 
document_url: https://discovery.ucl.ac.uk/id/eprint/1427243/1/aa22941-13.pdf