Archive for 十月, 2009


星期二, 十月 20th, 2009




Testing Standard Cosmology with Large Scale Structure

星期二, 十月 13th, 2009

The galaxy power spectrum contains information on the growth of structure, the growth rate through redshift space distortions, and the cosmic expansion through baryon acoustic oscillation features.

We study the ability of two proposed experiments, BigBOSS and JDEM-PS,


理论和观测联系:dimensionless growth rate f

数据分析工具: Fisher matrix

sparked my dig into this issue

星期二, 十月 13th, 2009

sparked my dig into this issue


星期二, 十月 13th, 2009

Observational surveys of elliptical galaxies at high redshift have in recent years revealed a further interesting fact: ellipticals at high redshift appear to be much smaller in size than those in our local Universe, but have about the same mass and density of stars.


Lyman alpha systems and cosmology- Lyman alpha forest

星期四, 十月 8th, 2009

1 why forest
Neutral hydrogen atoms in their lowest state will interact with whatever light has been redshifted to a wavelength of 1216 angstroms when it reaches them. The rest of the light will keep travelling to us.

2 why absorption lines

if you shine a light with wavelength 1216 at a bunch of neutral hydrogen atoms in their ground state, the atoms will absorb the light, using it to boost the electron to a higher energy state. If there are a lot of neutral hydrogen atoms in their ground state, they will absorb more and more of the light. So if you look at the light you receive, intensity as a function of wavelength, you will see a dip in the intensity at 1216 angstroms, depending on the amount of neutral hydrogen present in its ground state. The amount of light absorbed (‘optical depth’) is proportional to the probability that the hydrogen will absorb the photon (cross section) times the number of hydrogen atoms along its path.

The chemical evolution of the Galaxy

星期四, 十月 8th, 2009

The model for the chemical evolution of the Galaxy was described in detail by Ferrini et al. (1992) and it was updated by Travaglio et al. (1999, 2001, 2004).


星期四, 十月 8th, 2009

It’s something to motivate calculations, not something backed up by calculations.


星期三, 十月 7th, 2009






星期三, 十月 7th, 2009

Today, in a seminar, a Prof. asked: in the future, if more and more the data show w=-1 with a little error bar, like today’s data most likely shows but with a bigger error, what that means? Can we rule out all the dynamical model or can still can say any thing about the nature of the DE?

which data we need more ? the data at z~1 or higher z?


it should be z<~1, at different bin