Open AccessCold filaments in galaxy clusters: effects of heat conduction
Author(s) -
Nipoti Carlo,
Binney James
Publication year - 2004
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2004.07628.x
Subject(s) - physics , protein filament , astrophysics , radius , galaxy , thermal conduction , radiative cooling , cluster (spacecraft) , thermal conductivity , condensation , galaxy cluster , luminosity , atomic physics , thermodynamics , genetics , computer security , computer science , biology , programming language
We determine the critical size l crit of a filament of cold ( T ∼ 10 4 K ) gas that is in radiative equilibrium with X‐ray emitting gas at temperatures T out ∼ 10 6 –10 8 K . Filaments smaller than l crit will be rapidly evaporated, while longer ones will induce the condensation of the ambient medium. At fixed pressure P , l crit increases as T 11/4 out , while at fixed T out , it scales as P −1 . It scales as f 1/2 , where f is the factor by which the magnetic field depresses the thermal conductivity below Spitzer's benchmark value. For plausible values of f , l crit is similar to the lengths of observed filaments. In a cluster such as Perseus, the value of l crit increases by over an order of magnitude between the centre and a radius of 100 kpc. If the spectrum of seed filament lengths l is strongly falling with l , as is natural, then these results explain why filaments are only seen within a few kiloparsecs of the centres of clusters, and are not seen in clusters that have no cooling flow. We calculate the differential emission measure as a function of temperature for the interface between filaments and ambient gas of various temperatures. We discuss the implications of our results for the origin of the galaxy luminosity function.