منابع مشابه
Deuterium Abundance in the Local Ism Andpossible Spatial
Excellent HST/GHRS spectra of interstellar hydrogen and deuterium Lyman-absorption toward nearby stars allow us to identify systematic errors that have plagued earlier work and to measure accurate values of the D/H ratio in local interstellar gas. Analysis of 12 sightlines through the Local Interstellar Cloud leads to a mean value of D/H = (1:50 0:10) 10 ?5 with all data points lying within 1 o...
متن کاملCosmological Implications of the First Measurement of the Local Ism Abundance of He
Deuterium plays a crucial role in testing big-bang nucleosynthesis. Its chemical evolution, while simple (it is burned to He), is intertwined with the more complicated evolution of He. Gloeckler & Geiss’ new measurement of the He abundance and the HST measurement of D, both in the local ISM today, can be compared to the pre-solar nebula abundances of D and He. Within the uncertainties, the sum ...
متن کاملThe Deuterium Abundance towards QSO 1009 + 2956
We present a measurement of the deuterium to hydrogen ratio (D/H) in a metal-poor absorption system at redshift z = 2.504 towards the QSO 1009+2956. We apply the new method of Burles & Tytler (1997) to robustly determine D/H in high resolution Lyα forest spectra, and include a constraint on the neutral hydrogen column density determined from the Lyman continuum optical depth in low resolution s...
متن کاملThe Deuterium Abundance Towards Q 1937 – 1009
We present a new measurement of the deuterium-to-hydrogen ratio (D/H) in the Lyman limit absorption system at z = 3.572 towards Q1937–1009. Tytler, Fan & Burles (1996; hereafter TFB) made the first extragalactic detection of deuterium in this absorption system, which remains the best location for a high accuracy measurement of primordial D/H. Their detailed analysis of Keck spectra gave a low v...
متن کاملTiny Hi Clouds in the Local Ism
We report deep, high spectral resolution WSRT H I 21cm observations of four high latitude compact radio sources, that have revealed a new population of tiny, discrete clouds in the diffuse ISM, with peak optical depths τ ∼ 0.1−2%, H I column densities of 0.4–8 ×1018 cm−2 and core temperatures of 20–80 K. Imaging detections confirm these low column densities and imply linear core dimensions of a...
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ژورنال
عنوان ژورنال: Symposium - International Astronomical Union
سال: 2002
ISSN: 0074-1809
DOI: 10.1017/s0074180900113762