Pulsar Studies of Tiny - Scale Structure in the Neutral ISM
نویسنده
چکیده
We describe the use of pulsars to study small-scale neutral structure in the interstellar medium (ISM). Because pulsars are high velocity objects, the pulsarEarth line of sight sweeps rapidly across the ISM. Multiepoch measurements of pulsar interstellar spectral line spectra therefore probe ISM structures on AU scales. We review pulsar measurements of small scale structure in HI and OH and compare these results with those obtained through other techniques.
منابع مشابه
Does Tiny-scale Atomic Structure Exist in the Interstellar Medium ?
We report on preliminary results from the recent multi-epoch neutral hydrogen absorption measurements toward three pulsars, B0823+26, B1133+16 and B2016+28, using the Arecibo telescope. We do not find significant variations in optical depth profiles over periods of 0.3 and 9–10 yr, or on spatial scales of 10–20 and 70–85 AU. The large number of non detections of the tiny scale atomic structure ...
متن کاملThe Thinnest Cold Hi Clouds in the Diffuse Interstellar Medium?
We confirm and discuss recently discovered cold HI clouds with column densities among the lowest ever detected. The column densities of Cold Neutral Medium (CNM) towards 3C286 and 3C287 are ∼ 10 cm, below an observational lower limit, and also below tiny-scale-atomic clouds detected by VLBI and time-variable profiles against pulsars. These column densities are close to the minimum imposed by th...
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...
متن کاملHow Long Can Tiny H I Clouds Survive?
We estimate the evaporation timescale for spherical H I clouds consisting of the cold neutral medium surrounded by the warm neutral medium. We focus on clouds smaller than 1pc, which corresponds to tiny H I clouds recently discovered by Braun & Kanekar and Stanimirović & Heiles. By performing one-dimensional spherically symmetric numerical simulations of the two-phase interstellar medium (ISM),...
متن کاملA Model for the Moving ‘wisps’ in the Crab Nebula
I propose that the moving ‘wisps’ near the center of the Crab Nebula result from nonlinear KelvinHelmholtz instabilities in the equatorial plane of the shocked pulsar wind. Recent observations suggest that the wisps trace out circular wavefronts in this plane, expanding radially at speeds<∼ c/3. Instabilities could develop if there is sufficient velocity shear between a faster-moving equatorial...
متن کامل