Power Spectrum of the density of cold atomic gas in the Galaxy towards Cas A and Cygnus A
نویسندگان
چکیده
We have obtained the power spectral description of the density and opacity fluctuations of the cold HI gas in the Galaxy towards Cas A, and Cygnus A. We have employed a method of deconvolution, based on CLEAN, to estimate the true power spectrum of optical depth of cold HI gas from the observed distribution, taking into account the finite extent of the background source and the incomplete sampling of optical depth over the extent of the source. We investigate the nature of the underlying spectrum of density fluctuations in the cold HI gas which would be consistent with that of the observed HI optical depth fluctuations. These power spectra for the Perseus arm towards Cas A, and for the Outer arm towards Cygnus A have a slope of 2.75±0.25 (3σ error). The slope in the case of the Local arm towards Cygnus A is 2.5, and is significantly shallower in comparison. The linear scales probed here range from 0.01 to 3 pc. We discuss the implications of our results, the non-Kolmogorov nature of the spectrum, and the observed HI opacity variations on small
منابع مشابه
H I Absorption toward the Nucleus of the Powerful Radio Galaxy Cygnus A: Evidence for an Atomic Obscuring Torus?
We report the detection of broad (FWHM 270 km s) H I z 21 cm absorption toward the compact (,15 h pc) radio nucleus of the nearby powerful radio galaxy Cygnus A. The absorption corresponds to a column density of hydrogen atoms of at least 2.54H 0.44 3 10 Tspin cm. Observations of OH and H2CO yielded upper limits. While other possibilities exist, we argue that the observed H I absorption plausib...
متن کاملabsorption toward the nucleus of the powerful radio galaxy Cygnus A : evidence for an atomic obscuring torus ?
We report the detection of broad (FWHM 270kms 1) H I 21 cm absorption toward the compact (<15h 1 pc) radio nucleus of the nearby powerful radio galaxy Cygnus A. The absorption corresponds to a column density of hydrogen atoms of at least 2.54 0.44 1019 Tspin cm 2. Observations of OH and H2CO yielded upper limits. While other possibilities exist, we argue that the observed H I absorption plausib...
متن کاملThe Cavity of Cygnus A
In this paper, we focus on the limb-brightened, prolate spheroidal cavity of the radio galaxy Cygnus A, as revealed by the Chandra X-ray Observatory. We use the shock heated, thermal intracluster medium around the expanding cavity to infer the properties of the radio synchrotron-emitting gas inside the cavity. The gas along the N and S edges of the cavity is found to have an average temperature...
متن کاملThe effect of variation of stellar dispersion velocities by the galactic latitude in interpreting gravitational microlensing observations
Our galaxy is a spiral galaxy and its stars are mostly in a thin disk and rotate around the galactic center. The vertical component of the dispersion velocity of stars is a function of the galactic latitude and decreases with increasing it. In the galactic Besancon model, this dependence is ignored and they just consider the dependence of dispersion velocity on the stellar age. Becanson model i...
متن کاملExergy Analysis of a Novel Combined System Consisting of a Gas Turbine, an Organic Rankine Cycle and an Absorption Chiller to Produce Power, Heat and Cold
The current work investigates the exergy analysis of a new system to generate power, heat, and refrigeration. In the proposed system, the heat loss of a gas turbine (GT) is first recovered by a Heat Recovery Steam Generator (HRSD), then by an Organic Rankine Cycle (ORC) to generate warm water and additional power, respectively. In the ORC, reheating is used to increase the output power, the req...
متن کامل