Showing papers by "Carol J. Lonsdale published in 1993"
TL;DR: In this paper, the authors present new observations and theoretical models for the continuous ultraviolet-to-radio spectrum of the ultraluminous protogalaxy candidate IRAS F 10214 + 4724.
Abstract: We present new observations and theoretical models for the continuous ultraviolet-to-radio spectrum of the ultraluminous protogalaxy candidate IRAS F 10214 + 4724. The radio spectrum at 1.49-8.44 GHz (consistent with a power law of slope 0.9 0.1) and the resolved nature of the radio source are compatible with a synchrotron origin of the radio radiation associated with a luminous starburst. The object has an exceptionally high ratio of far-infrared to radio emission, however, and this could imply that the starburst is unusually young. The submillimetre and far-infrared spectrum is modelled in terms of emission from both spherically symmetric dust clouds and an axially symmetric flared disc
94 citations
TL;DR: The results of an 18 cm VLBI survey of 31 luminous, radio-compact IR galaxies are presented in this paper, showing that over half the sample galaxies show high-brightness temperature emission, with T sub b greater than 10 exp 5 K and structure on scales of 5-150 mas.
Abstract: Results of an 18 cm VLBI survey of 31 luminous, radio-compact IR galaxies are presented. Over half the sample galaxies show high-brightness temperature emission, with T sub b greater than 10 exp 5 K and structure on scales of 5-150 mas. The limits for nondetected sources are similar, consistent with a picture in which most of these galaxies have compact cores at a level of a few percent of the total radio flux density. Characteristics of the extended radio structure, infrared properties, and optical excitation are not good indicators of the detectability of VLBI-scale emission. Structural information and energetic considerations rule out a single supernova interpretation of the compact emission in these galaxies, although we cannot exclude the possibility of several simultaneous extraordinarily luminous radio supernovae within the central few hundred cubic parsec. Our results instead favor the presence of an AGN obscured by starburst-related dust.
86 citations
TL;DR: In this paper, the space density of blue-selected galaxies at moderate redshifts is determined directly by deriving the luminosity function, and evidence is found for density evolution for moderate luminosity galaxies at a rate of (1+z) exp delta, with a best fit of delta + 4 +/- 2.
Abstract: The space density of blue-selected galaxies at moderate redshifts is determined here directly by deriving the luminosity function. Evidence is found for density evolution for moderate luminosity galaxies at a rate of (1+z) exp delta, with a best fit of delta + 4 +/- 2, between the current epoch and Z greater than about 0.1. At M(b) less than -22 evidence is found for about 0.5-1.5 mag of luminosity evolution in addition to the density evolution, corresponding to an evolutionary rate of about (1+z) exp gamma, with gamma = 0.5-2.5, but a redshift of about 0.4. Assuming a steeper faint end slope of alpha = -1.3 similar to that observed in the Virgo cluster, could explain the data with a luminosity evolution rate of gamma = 1-2, without need for any density evolution. Acceptable fits are found by comparing composite density and luminosity evolution models to faint IRAS 60 micron source counts, implying that the blue and far-IR evolutionary rates may be similar.
5 citations
01 Jan 1993
TL;DR: The spectral energy distributions for many of these objects peak at or close to 25µm as discussed by the authors, which suggests that this sample of 25 µm emitters may be a rich source of new PNe and PPNe.
Abstract: The IRAS Point Source Catalogue containing about 250,000 sources has yielded a large number of previously unknown planetary nebulae (PNe) and a smaller number of proto-planetary nebulae (PPNe). The spectral energy distributions for many of these objects peak at or close to 25µm. A program to optically identify sources in the complete IRAS Faint Source Database, which comprises about 750,000 sources, is currently under way (Wolstencroft et al. 1991), and in a related study Wolstencroft, Parker & Lonsdale are carrying out a spectroscopic survey of a small sample of the approximately 106,000 sources which either peak or are detected only at 25µm. So far spectra of 150 sources have been obtained: 3 of these sources are PNe and 1 is a PPNe. This suggests that this sample of 25µm emitters may be a rich source of new PNe and PPNe. In this note we discuss two of these four sources.