6,802 research outputs found
Voids in the Local Volume: a limit on appearance of a galaxy in a DM halo
Current explanation of the overabundance of dark matter subhalos in the Local
Group (LG) indicates that there maybe a limit on mass of a halo, which can host
a galaxy. This idea can be tested using voids in the distribution of galaxies:
at some level small voids should not contain any (even dwarf) galaxies. We use
observational samples complete to M_B = -12 with distances less than 8 Mpc to
construct the void function (VF): the distribution of sizes of voids empty of
any galaxies. There are ~30 voids with sizes ranging from 1 to 5 Mpc. We then
study the distribution of dark matter halos in very high resolution simulations
of the LCDM model. The theoretical VF matches the observations remarkably well
only if we use halos with circular velocities larger than 45 +/- 10 km/s. This
agrees with the Local Group predictions. There are smaller halos in the voids,
but they should not produce any luminous matter. Small voids look quite similar
to their giant cousins: the density has a minimum at the center of a void and
it increases as we get closer to the border. Small nonluminous halos inside the
void form a web of tiny filaments. Thus, both the Local Group data and the
nearby voids indicate that isolated halos below 45 +/- 10 km/s must not host
galaxies and that small (few Mpc) voids are truly dark.Comment: 5 pages, 1 figur
Hydration of a B-DNA Fragment in the Method of Atom-atom Correlation Functions with the Reference Interaction Site Model Approximation
We propose an efficient numerical algorithm for solving integral equations of
the theory of liquids in the Reference Interaction Site Model (RISM)
approximation for infinitely dilute solution of macromolecules with a large
number of atoms. The algorithm is based on applying the nonstationary iterative
methods for solving systems of linear algebraic equations. We calculate the
solvent-solute atom-atom correlation functions for a fragment of the B-DNA
duplex d(GGGGG).d(CCCCC) in infinitely dilute aqueous solution. The obtained
results are compared with available experimental data and results from computer
simulations.Comment: 9 pages, RevTeX, 9 pages of ps figures, accepted for publications in
JC
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