We include feedback in global hydrodynamic simulations in order to study the star formation properties, and gas structure and dynamics, in models of galactic disks. In previous work we studied the growth of clouds and spiral substructure due to gravitational instability.We extend thesemodels by implementing feedback in gravitationally bound clouds; momentum (due to massive stars) is injected at...

Although the basic physics of star formation is classical, numerical simulations have yielded several essential insights into how stars form. They show that star formation is a highly nonuniform runaway process characterized by the emergence of nearly singular peaks in density, followed by the accretional growth of embryo stars that form at these density peaks. Circumstellar disks often form fr...

We revisit the problem of the star formation timescale and the ages of molecular clouds. The apparent overabundance of star-forming molecular clouds over clouds without active star formation has been thought to indicate that molecular clouds are “short-lived” and that star formation is “rapid”. We show that this statistical argument lacks self-consistency and, even within the rapid star-formati...

We investigate the relationship between the star formation rate per unit area and the surface density of the ISM (the local Kennicutt-Schmitt law) using a simplified model of the ISM and a simple estimate of the star formation rate based on the mass of gas in bound clumps, the local dynamical timescales of the clumps, and an efficiency parameter of around ≈ 5 per cent. Despite the simplicity of...

We consider a setting where every pair of players that undertake a transaction (e.g. exchange goods or information) create a unit surplus. A transaction can take place only if the players involved have a connection. If the connection is direct the two players split the surplus equally while if it is indirect then intermediate players also get an equal share of the surplus. Thus individuals form...

We model star formation in a wide range of isolated disk galaxies, using a three-dimensional, smoothed particle hydrodynamics code. The model galaxies include a dark matter halo and a disk of stars and isothermal gas. Absorbing sink particles are used to directly measure the mass of gravitationally collapsing gas. Below the density at which they are inserted, the collapsing gas is fully resolve...

Star formation is probably the most fundamental of all astrophysical processes: not only do the properties of stellar systems of all types depend on how their stars were formed, but the properties of the interstellar medium in galaxies are controlled to a large extent by various feedback effects of star formation. Thus there are many reasons why it is important to understand how stars form, and...

We present a general star formation law where star formation rate depends upon efficiency α, timescale τ of star formation, gas component σg of surface mass density and a real exponent n. A given exponent n determines τ which however yields the corresponding star formation rate. Current nominal Schmidt exponent ns for our model is 2 < ns < 3. Based on a gravitational instability parameter QA an...