eprintid: 10095264
rev_number: 14
eprint_status: archive
userid: 608
dir: disk0/10/09/52/64
datestamp: 2020-05-13 13:13:52
lastmod: 2021-10-05 00:18:18
status_changed: 2020-05-13 13:13:52
type: article
metadata_visibility: show
creators_name: James, BL
creators_name: Tsamis, YG
creators_name: Barlow, MJ
creators_name: Walsh, JR
creators_name: Westmoquette, MS
title: The merging dwarf galaxy UM 448: chemodynamics of the ionized gas from VLT integral field spectroscopy
ispublished: pub
divisions: UCL
divisions: B04
divisions: C06
divisions: F60
keywords: stars: Wolf–Rayet, galaxies: abundances, galaxies: dwarf, galaxies: individual: UM 448, galaxies: interactions, galaxies: kinematics and dynamics
note: This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
abstract: Using Very Large Telescope/Fibre Large Array Multi Element Spectrograph optical integral field unit observations, we present a detailed study of UM 448, a nearby blue compact galaxy (BCG) previously reported to have an anomalously high N/O abundance ratio. New Technology Telescope/Superb-Seeing Imager images reveal a morphology suggestive of a merger of two systems of contrasting colour, whilst our Hα  emission maps resolve UM 448 into three separate regions that do not coincide with the stellar continuum peaks. UM 448 exhibits complex emission line profiles, with most lines consisting of a narrow [full width at half-maximum (FWHM) ≲ 100 km s−1], central component, an underlying broad component (FWHM ∼ 150–300 km s−1) and a third, narrow blueshifted component. Radial velocity maps of all three components show signs of solid body rotation across UM 448, with a projected rotation axis that correlates with the continuum morphology of the galaxy. A spatially resolved, chemodynamical analysis, based on the [O III] λλ4363, 4959, [N II] λ6584, [S II] λλ6716, 6731 and [Ne III] λ3868 line maps, is presented. Whilst the eastern tail of UM 448 has electron temperatures (Te) that are typical of BCGs, we find a region within the main body of the galaxy where the narrow and broad [O III] λ4363 line components trace temperatures differing by 5000 K and oxygen abundances differing by 0.4 dex. We measure spatially resolved and integrated ionic and elemental abundances for O, N, S and Ne throughout UM 448, and find that they do not agree, possibly due the flux weighting of Te  from the integrated spectrum. This has significant implications for abundances derived from long-slit and integrated spectra of star-forming galaxies in the nearby and distant universe. A region of enhanced N/O ratio is indeed found, extended over a ∼0.6 kpc2 region within the main body of the galaxy. Contrary to previous studies, however, we do not find evidence for a large Wolf–Rayet (WR) population, and conclude that WR stars alone cannot be responsible for producing the observed N/O excess. Instead, the location and disturbed morphology of the N-enriched region suggest that interaction-induced inflow of metal-poor gas may be responsible.
date: 2013-01-01
date_type: published
publisher: OXFORD UNIV PRESS
official_url: https://doi.org/10.1093/mnras/sts004
oa_status: green
full_text_type: pub
language: eng
primo: open
primo_central: open_green
verified: verified_manual
elements_id: 793406
doi: 10.1093/mnras/sts004
lyricists_name: Barlow, Michael
lyricists_id: MJBAR75
actors_name: Barlow, Michael
actors_id: MJBAR75
actors_role: owner
full_text_status: public
publication: Monthly Notices of the Royal Astronomical Society
volume: 428
number: 1
pagerange: 86-102
pages: 17
citation:        James, BL;    Tsamis, YG;    Barlow, MJ;    Walsh, JR;    Westmoquette, MS;      (2013)    The merging dwarf galaxy UM 448: chemodynamics of the ionized gas from VLT integral field spectroscopy.                   Monthly Notices of the Royal Astronomical Society , 428  (1)   pp. 86-102.    10.1093/mnras/sts004 <https://doi.org/10.1093/mnras%2Fsts004>.       Green open access   
 
document_url: https://discovery.ucl.ac.uk/id/eprint/10095264/1/James2012_UM448.pdf