Contents of: VI/111/./abstract/DSANDERS_ULIGS.abs

The following document lists the file abstract/DSANDERS_ULIGS.abs from catalogue VI/111.
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 Perhaps the most important finding from the IRAS survey was the
 discovery of a significant population of galaxies whose infrared
 luminosities are equivalent to the bolometric luminosities of
 optically-selected quasars. Assessing the relative importance of
 an AGN and massive stars for powering ultraluminous IR galaxies
 (ULIGs) is essential for understanding these objects as massive
 galaxies and/or quasars in formation, and for testing suggestions
 of an evolutionary connection between starburst and AGN phenomena.
 The target galaxies were taken from a recently compiled sample of
 ULIGs which contains the brightest objects at a given L_ir (< 10^13
 L_sun) and which is not biased towards `warm' quasar-like objects
 with large S(25 um)/S(60 um) ratios. The galaxies in our sample span
 the luminosity range log[L_ir/L_sun] = 12.3 - 13, currently not
 explored spectroscopically by the ISO Central Program. The Central
 Programme focuses on previously published objects that typically lie
 below this range of L_ir, and the few exotic `hyperluminous'
 (L_ir > 10^13 L_sun) objects at much higher redshifts. Our sample
 therefore provides an important bridge between these two extremes
 that could prove critical to the interpretation of the more distant
 `hyperluminous' objects. We plan to measure the fluxes of the
 fine-structure lines [Ne II] 12.8 um, [Ne III] 15.6 um,
 [Ne III] 36.0 um, [Ne V] 14.3 um, [O III] 52 um, and [O III]
 88 um. These data will then be combined with our optical and
 near-infrared measurements to (1) determine the physical conditions
 and ionization mechanisms of the nebular gas in these galaxies,
 (2) measure the stellar content in the objects powered by stars, and
 (3) evaluate the importance of dust extinction. This study will
 provide new insights into the relative role of starbursts and AGN in
 powering ULIGs, and possible evolutionary links between these two
 phenomona.

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