warm-hot intergalactic medium
madim-e andar-kahkašâni garm-dâq
Fr.: milieu intergalactique chaud
The space containing a cluster of galaxies filled with a tenuous gas of temperature 105 to 107 K and density 10-6 to 10-4 cm-3. WHIM has been continuously shock-heated during the process of structure formation. It is so highly ionized that it can only absorb or emit far-ultraviolet and soft X-ray photons, primarily at spectral lines of highly ionized C, O, Ne, and Fe. WHIM is thought to be the main reservoir of missing baryons.
→ warm; → hot; → intergalactic medium.
The process of becoming warmer; a rising temperature. → backwarming, → heating.
weak arm spiral galaxy
kahkešân-e mârpic bâ bâzu-ye nezâr
Fr.: galaxie spirale à faibles bras
A gas-rich galaxy that has weak stellar → spiral arms with → interarm gas and star formation more important than a typical → spiral galaxy, such as NGC 4414.