NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-04-25 T07:40:17 PDT
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For refcode 1991A&AS...90...55v:
Retrieve 72 NED objects in this reference.
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Copyright by European Southern Observatory (ESO). Reproduced by permission
1991A&AS...90...55v A study of southern extreme IRAS galaxies. II. Radio continuum observations W. van Driel, AC. van den Broek and T de Jong Astronomical Institute `Anton Pannekoek", University of Amsterdam, Kruislaan 403, NL-1098 SJ Amsterdam, The Netherlands Received December 14, 1990; accepted February 11, 1991 Abstract. - As part of a multi-wavelength study of an infrared-complete sample of extreme IRAS galaxies with high far-infrared / blue luminosity ratios (L_FIR_/L^0^_B_ ~> 3) we have observed 76 of them at 6 cm wavelength with the VLA, in order to study the star forming regions unimpeded by dust. We also have CCD images and spectra of these objects, as well as CO(1-0) spectra of a subsample. Integration times were about ten minutes at both low- (12" HPBW) and high (1") resolution and we detected all objects. We found that 20 radio sources are clearly resolved with intrinsic sizes [H_0_ = 75 km s^-1^ Mpc^-1^] ranging from 0.6 to 2.2 kpc (average 1.1 kpc); the upper limits for the intrinsic size of the unresolved sources are 0.2-1.3 kpc (mean<0.8 kpc). The resolved sources have a surface brightness similar to that of galactic nuclei, but considerably higher than that of galactic disks. On average some 60% of the total flux density derived from the low-resolution maps is found back in the high-resolution data. Galaxies with a higher L_FIR_/L^0^_B_ratio appear to have more compact radio sources, implying that in objects with higher star formation activity, this activity is concentrated in smaller regions. With the exception of a single radio-loud Seyfert 2-type galaxy all objects in our sample follow the same tight far-infrared/radio luminosity correlation as other IRAS and RSA galaxies, indicating star formation as the main energy source, also in those with active nuclei. However, the galaxies with AGN-type spectra have a significantly higher average far-infrared luminosity and radio power than the H II-type galaxies, and they are not found below a certain luminosity limit, where we still find objects with H II-type spectra. Our data are consistent with a slope of unity for the correlation, expected if both quantities are a measure of the star formation activity. Using the correlation found between the extinction-corrected H{alpha} and far-infrared luminosities for the galaxies in our sample, we estimate that on average a substantial fraction, about 40%, of the total radio power emitted by the galaxies at 6 cm has a thermal origin. This ratio is consistent with published radio spectral indices of similar extreme IRAS galaxies. Key words: Galaxies: general.
Retrieve 72 NED objects in this reference.
Please click here for ADS abstract

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