eprintid: 10093768
rev_number: 20
eprint_status: archive
userid: 608
dir: disk0/10/09/37/68
datestamp: 2020-04-27 13:52:32
lastmod: 2021-10-04 01:19:49
status_changed: 2020-04-27 13:52:32
type: article
metadata_visibility: show
creators_name: Bisbas, TG
creators_name: Bell, TA
creators_name: Viti, S
creators_name: Barlow, MJ
creators_name: Yates, J
creators_name: Vasta, M
title: A photodissociation region study of NGC 4038
ispublished: pub
divisions: UCL
divisions: B04
divisions: C05
divisions: F48
divisions: C06
divisions: F60
keywords: astrochemistry, radiative transfer, methods: numerical, photodissociation region (PDR), galaxies: ISM
note: This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
abstract: We present a model of the photodissociation regions of NGC 4038, which is part of the Antennae galaxies. We have considered one-dimensional slabs of uniform density, all having a maximum AV = 10 mag, interacting with plane-parallel radiation. The density range in our simulations spans four orders of magnitude (100 ≤ n ≤ 106 cm−3) and the UV field strength spans more than three orders of magnitude (10 ≤ χ ≤ 104.5 multiples of the Draine field), from which we generated a grid of about 1400 simulations. We compare our results with Herschel SPIRE-FTS, CSO and ISO-LWS observations of eight CO transition lines (J = 1-0 to 8-7) and the [C I] 609 μm and [O I] 146 μm fine-structure lines. We find that the molecular and atomic emission lines trace different gas components of NGC 4038; thus, single emission models are insufficient to reproduce the observed values. In general, low-J CO transition lines correspond to either low-density regions interacting with low UV field strengths, or high-density regions interacting with high UV field strengths. Higher J CO transition lines are less dependent on the UV field strength and are fitted by gas with density n ∼ 104.5-105.2 cm− 3. We find that the observed fine-structure line ratio of [C I] 609 μm/[O I] 146 μm is reproduced by clouds subject to weaker UV fields compared to the CO lines. We make estimates of the XCO factor which relates the CO emission with the column density of molecular hydrogen, and find that it is less than the canonical Milky Way value.
date: 2014-09-01
date_type: published
publisher: OXFORD UNIV PRESS
official_url: https://doi.org/10.1093/mnras/stu1143
oa_status: green
full_text_type: pub
language: eng
primo: open
primo_central: open_green
verified: verified_manual
elements_id: 972825
doi: 10.1093/mnras/stu1143
lyricists_name: Barlow, Michael
lyricists_name: Bisbas, Thomas
lyricists_name: Viti, Serena
lyricists_name: Yates, Jeremy
lyricists_id: MJBAR75
lyricists_id: TBISM37
lyricists_id: SVITI18
lyricists_id: JAYAT84
actors_name: Allington-Smith, Dominic
actors_id: DAALL44
actors_role: owner
full_text_status: public
publication: Monthly Notices of the Royal Astronomical Society
volume: 443
number: 1
pagerange: 111-121
pages: 11
citation:        Bisbas, TG;    Bell, TA;    Viti, S;    Barlow, MJ;    Yates, J;    Vasta, M;      (2014)    A photodissociation region study of NGC 4038.                   Monthly Notices of the Royal Astronomical Society , 443  (1)   pp. 111-121.    10.1093/mnras/stu1143 <https://doi.org/10.1093/mnras%2Fstu1143>.       Green open access   
 
document_url: https://discovery.ucl.ac.uk/id/eprint/10093768/7/Barlow_stu1143.pdf