Astronomy and Astrophysics – Astrophysics
Scientific paper
1999-08-07
ApJ 529 (2000) 615
Astronomy and Astrophysics
Astrophysics
38 pages, 16 figures, accepted for publication in ApJ
Scientific paper
10.1086/308296
The effects of the UV background radiation on the formation of sub-galactic clouds are studied by means of one-dimensional hydrodynamical simulations. The radiative transfer of the ionizing photons due to the absorption by HI, HeI and HeII, neglecting the emission, is explicitly taken into account. We find that the complete suppression of collapse occurs for the clouds with circular velocities typically in the range V_c \sim 15-40 km/s and the 50% reduction in the cooled gas mass with V_c \sim 20-55 km/s. These values depend most sensitively on the collapse epoch of the cloud, the shape of the UV spectrum, and the evolution of the UV intensity. Compared to the optically thin case, previously investigated by Thoul & Weinberg (1996), the absorption of the external UV photon by the intervening medium systematically lowers the above threshold values by \Delta V_c \sim 5 km/s. Whether the gas can contract or keeps expanding is roughly determined by the balance between the gravitational force and the thermal pressure gradient when it is maximally exposed to the external UV flux. Based on our simulation results, we discuss a number of implications on galaxy formation, cosmic star formation history, and the observations of quasar absorption lines. In Appendix, we derive analytical formulae for the photoionization coefficients and heating rates, which incorporate the frequency/direction-dependent transfer of external photons.
Ikeuchi Satoru
Kitayama Tetsu
No associations
LandOfFree
Formation of Sub-galactic Clouds under UV Background Radiation does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Formation of Sub-galactic Clouds under UV Background Radiation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Formation of Sub-galactic Clouds under UV Background Radiation will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-636364