相关论文: On Star Formation and the Non-Existence of Dark Ga…

We show that gas in a large fraction of low mass dark matter halos may form Toomre stable disks, if angular momentum is conserved when the gas contracts. Such halos would be stable to star formation and therefore remain dark. This may…

To make predictions for the existence of ``dark galaxies'', it is necessary to understand what determines whether a gas cloud will form stars. Star formation thresholds are generally explained in terms of the Toomre criterion for…

We present an analysis of the atomic hydrogen and stellar properties of 38 late-type galaxies in the local Universe covering a wide range of HI mass-to-light ratios (M_HI/L_B), stellar luminosities, and surface brightnesses. From these data…

We investigate the atomic (HI) and molecular (H_2) Hydrogen content of normal galaxies by combining observational studies linking galaxy stellar and gas budgets to their host dark matter (DM) properties, with a physically grounded galaxy…

High spatial and spectral resolution observations of the atomic interstellar medium in nearby dwarf galaxies reveal evidence for warm and cold neutral gas, just like the phases in our own Galaxy. The cold or quiescent phase (about 20% of…

The standard theory of galaxy formation predicts that all galaxies should contain dark matter, yet a handful of recently discovered galaxies appear to lack it, challenging our understanding of galaxy formation. We investigate whether such…

The HI in galaxies often extends past their conventionally defined optical extent. I report results from our team which has been probing low intensity star formation in outer disks using imaging in H-alpha and ultraviolet. Using a sample of…

Gravitational lensing studies suggest that the Universe may contain a population of dark galaxies; we investigate this intriguing possibility and propose a mechanism to explain their nature. In this mechanism a dark galaxy is formed with a…

We study global star formation thresholds in the outer parts of galaxies by investigating the stability of disk galaxies embedded in dark halos. The disks are self-gravitating, contain metals and dust, and are exposed to UV radiation. We…

Optically thin cooling gas at most temperatures above 30K will make condensations by pressure pushing material into cool dense regions. This works without gravity. Cooling condensations will flatten and become planar/similarity solutions.…

Models of hierarchical galaxy formation predict that large numbers of low-mass, dark matter halos remain around galaxies today. These models predict an order of magnitude more halos than observed stellar satellites in the Local Group. One…

How do stars manage to form within low-density, HI-dominated gas? Such environments provide a laboratory for studying star formation with physical conditions distinct from starbursts and the metal-rich disks of spiral galaxies where most…

The near proportionality between HI and dark matter in outer galactic disks prompted us to run N-body simulations of galactic disks in which the observed gas content is supplemented by a dark gas component representing between zero and five…

We develop a model for the outer gravitationally unstable regions of accretion disks around massive black holes, for primeval or solar abundances. First we study star formation and evolution in a purely gaseous marginally unstable disk, and…

We discuss the occurrence of subcritical star formation in the outskirts of some galactic discs and across LSB galaxies, contrary to the picture that star formation happens only when the gas surface density is above a critical threshold…

The apparent lack of cold molecular gas in blue compact dwarf (BCD) galaxies is at variance with their intense star-formation episode. The CO molecule, often used a tracer of H2 through a conversion function, is selectively photodissociated…

We use a high-resolution grid-based hydrodynamics method to simulate the multi-phase interstellar medium in a Milky Way-size quiescent disk galaxy. The models are global and three-dimensional, and include a treatment of star formation and…

A new class of models of stellar discs is introduced and used to build a self-consistent model of our Galaxy. The model is defined by the parameters that specify the action-based distribution functions (DFs) f(J) of four stellar discs…

We explore various instability models for the onset of star formation in irregular galaxies. Critical gas densities are calculated for gravitational instabilities with a thin, pure-gas disk, and with a thick disk composed of gas and a…

The radial profiles of gas, stars, and far ultraviolet radiation in 20 dwarf Irregular galaxies are converted to stability parameters and scale heights for a test of the importance of two-dimensional (2D) instabilities in promoting star…