A MERLIN neutral hydrogen absorption study of the luminous infrared merger NGC 6240

R. J. Beswick, A. Pedlar, C. G. Mundell, J. F. Gallimore

Research output: Contribution to journalArticle

48 Citations (Scopus)

Abstract

We present neutral hydrogen absorption observations of the luminous infrared merger NGC 6240 using MERLIN with a resolution of 0.2 arcsec. Broad absorption (a few hundred km s-1) has been found against two compact radio sources within the central kpc providing dynamical information about the neutral gas components in front of these sources. A narrow absorption component is also detected superimposed upon this broad absorption and additionally against some of the extended L-band continuum. From these results we deduce that the broad component is a result of absorption by a highly disturbed disc-like structure of neutral gas aligned along the position angle of the two compact radio sources, similar to the model previously proposed by Tacconi et al. at the end of the last century based on spectral CO emission data. The narrow component is likely to arise from absorption by less disturbed neutral gas at much larger scales within the system. Continuum observations presented here at 1.4 and 5 GHz support the view that NGC 6240 contains a double nucleus resulting from a galactic merger event and show these as two compact radio sources separated by 1.52 arcsec. We have also applied luminosity and morphological considerations to the continuum results to determine the most feasible source of radio emission for this luminous merger galaxy. We conclude that the most likely source of the radio flux found in NGC 6240 is a combination of starburst emission from radio luminous supernova remnants, similar to those found in Arp 220, and emission from a weak AGN probably triggered by a merger event.

Original languageEnglish
Pages (from-to)151-158
Number of pages8
JournalMonthly Notices of the Royal Astronomical Society
Volume325
Issue number1
DOIs
Publication statusPublished - 21 Jul 2001

Fingerprint

merger
hydrogen
radio
neutral gases
continuums
gas
spectral emission
ultrahigh frequencies
supernova remnants
radio emission
luminosity
galaxies
nuclei

Keywords

  • Galaxies: active
  • Galaxies: individual: NGC 6240
  • Galaxies: ISM
  • Galaxies: starburst
  • Infrared: galaxies
  • Radio lines: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

A MERLIN neutral hydrogen absorption study of the luminous infrared merger NGC 6240. / Beswick, R. J.; Pedlar, A.; Mundell, C. G.; Gallimore, J. F.

In: Monthly Notices of the Royal Astronomical Society, Vol. 325, No. 1, 21.07.2001, p. 151-158.

Research output: Contribution to journalArticle

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AB - We present neutral hydrogen absorption observations of the luminous infrared merger NGC 6240 using MERLIN with a resolution of 0.2 arcsec. Broad absorption (a few hundred km s-1) has been found against two compact radio sources within the central kpc providing dynamical information about the neutral gas components in front of these sources. A narrow absorption component is also detected superimposed upon this broad absorption and additionally against some of the extended L-band continuum. From these results we deduce that the broad component is a result of absorption by a highly disturbed disc-like structure of neutral gas aligned along the position angle of the two compact radio sources, similar to the model previously proposed by Tacconi et al. at the end of the last century based on spectral CO emission data. The narrow component is likely to arise from absorption by less disturbed neutral gas at much larger scales within the system. Continuum observations presented here at 1.4 and 5 GHz support the view that NGC 6240 contains a double nucleus resulting from a galactic merger event and show these as two compact radio sources separated by 1.52 arcsec. We have also applied luminosity and morphological considerations to the continuum results to determine the most feasible source of radio emission for this luminous merger galaxy. We conclude that the most likely source of the radio flux found in NGC 6240 is a combination of starburst emission from radio luminous supernova remnants, similar to those found in Arp 220, and emission from a weak AGN probably triggered by a merger event.

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