Original Article

Astrophysics and Space Science

, Volume 350, Issue 2, pp 741-754

Spaxel analysis: probing the physics of star formation in ultraluminous infrared galaxies

  • Michael A. DopitaAffiliated withResearch School of Astronomy and Astrophysics, Australian National UniversityAstronomy Department, King Abdulaziz UniversityInstitute for Astronomy, University of Hawaii Email author 
  • , Jeffrey RichAffiliated withCarnegie Observatories
  • , Frédéric P. A. VogtAffiliated withResearch School of Astronomy and Astrophysics, Australian National University
  • , Lisa J. KewleyAffiliated withResearch School of Astronomy and Astrophysics, Australian National UniversityInstitute for Astronomy, University of Hawaii
  • , I-Ting HoAffiliated withInstitute for Astronomy, University of Hawaii
  • , Hassan M. BasurahAffiliated withAstronomy Department, King Abdulaziz University
  • , Alaa AliAffiliated withAstronomy Department, King Abdulaziz University
  • , Morsi A. AmerAffiliated withAstronomy Department, King Abdulaziz University

Rent the article at a discount

Rent now

* Final gross prices may vary according to local VAT.

Get Access

Abstract

This paper presents a detailed spectral pixel (spaxel) analysis of the ten Luminous Infrared Galaxies (LIRGs) previously observed with the Wide Field Spectrograph (WiFeS), an integral field spectrograph mounted on the ANU 2.3 m telescope, and for which an abundance gradient analysis has already been presented by Rich et al. (Astrophys. J., 753:5, 2012). Here we use the strong emission line analysis techniques developed by Dopita et al. (Astrophys. J. Suppl. Ser., accepted, 2013) to measure the ionisation parameter and the oxygen abundance in each spaxel. In addition, we use the observed Hα flux to determine the surface rate of star formation (\(\mathrm {M}_{\odot }{\rm yr}^{-1}\)kpc−2) and use the [S II] λλ6717/6731 ratio to estimate the local pressure in the ionised plasma. We discuss the correlations discovered between these physical quantities, and use them to infer aspects of the physics of star formation in these extreme star forming environments. In particular, we find a correlation between the star formation rate and the inferred ionisation parameter. We examine the possible reasons for this correlation, and determine that the most likely explanation is that the more active star forming regions have a different distribution of molecular gas which favour higher ionisation parameters in the ionised plasma.

Keywords

Stars: star formation Interstellar medium: HII regions Galaxies: starburst, Chemical abundances