Constraints on Cold HI in the Halo of NGC 3079 from Absorption Measurements of Q0957+561

Publications of the Astronomical Society of Australia

Judith A. Irwin¹ 

[1] Lawrence M. Widrow

关键词: dark matter;    galaxies: halos;    galaxies: individual (NGC 3079);    ISM: structure;   

DOI  :  10.1071/AS99089

学科分类：天文学(综合)

来源: CSIRO

【 摘 要 】

We perform the first observational test of dark matter in the form of cold (3 K) fractal clouds, as described by Pfenniger et al. (1994) and Pfenniger & Combes (1994). This is accomplished by probing for HI absorption in the halo of NGC 3079 against the background quasar, Q 0957+561, which is separated from the centre of NGC 3079 by 64 kpc, in projection. No absorption is detected to a limit of 3ΔTb/(–Tc) = 0·01. We have considered models for HI + H2 clouds characterised by the cloud radius and fractal dimension. Using the upper limit on absorption, we have ruled out a limited but interesting region of this parameter space. The observations do not rule out the possibility that all the dark matter could be hidden in the form of cold fractal clouds. By contrast, if the gas is diffuse with unity filling factors, then HI cannot constitute more than ∼ 10−5, by mass, of the galaxy's dark matter.

【 授权许可】

Unknown