The structure of Doppler peaks induced by active perturbations
ArXiv astro-ph/9605047 (1996)
Abstract:
We investigate how the qualitative structure of Doppler peaks in the angular power spectrum of the cosmic microwave anisotropy is affected by basic assumptions going into theories of structure formation. We define the concepts of ``coherent'' and ``incoherent'' fluctuations, and also of ``active'' and ``passive'' fluctuations. In these terms inflationary fluctuations are passive and coherent while topological defects are active incoherent fluctuations. Causality and scale invariance are shown to have different implementations in theories differing in the above senses. We then extend the formalism of Hu and Sugiyama to treat models with cosmic defects. Using this formalism we show that the existence or absence of secondary Doppler peaks and the rough placing of the primary peak are very sensitive to the fundamental properties defined. We claim therefore that even a rough measurement of the angular power spectrum $C_l$ shape at $100A search for star formation around the Galactic halo B-type star PHL 346
Astronomy and Astrophysics 306:1 (1996) 119-124
Abstract:
A search is presented for stars that may have formed coevally with the apparently young halo star PHL 346. Candidates were selected for spectroscopy from UBR Schmidt Telescope plates in U.K. Schmidt Telescope survey field 603 scanned with the COSMOS facility at the Royal Observatory, Edinburgh. Spectroscopic observations at ∼ 3.5 Å resolution were made of 72 field stars using the 1.9m telescope at the South African Astronomical Observatory; 16 A- and B-type stars were found, one of which had the appropriate spectral type and radial velocity to be associated with PHL 346. Further photometry and spectroscopy confirmed this identification. The remaining low gravity early-type stars have a mean LSR radial velocity of -75 km s-1, consistent with a non-rotating halo Population.Causality, randomness, and the microwave background
PHYSICAL REVIEW LETTERS 76:9 (1996) 1413-1416
Doppler peaks from active perturbations
PHYSICAL REVIEW LETTERS 76:15 (1996) 2617-2620
How anisotropic is our Universe?
PHYSICAL REVIEW LETTERS 77:14 (1996) 2883-2886