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[1208.1491] The Clustering of Galaxies in SDSS-III DR9 Bary

Posted: April 13 2013
by YinZhe Ma
This is an interesting paper. The original idea of primordial non-Gaussanity and its relation with power spectrum can be found at Dalal, Dore, Huterer, and Shirokov, 0710.4560. I have a few questions regarding the bias and local nG:

1. The scale-dependent part of additional bias (A(k), in Eq.(4) in
1208.1491) is plotted in the attached figure "akfig.pdf". It seems that additional bias contribute more power on large scales than small scales. How do we understand this?


2. If A(k) I plotted is correct, then b_tot(k)=b+ Delta b(k) is shown in "btotfig1.pdf". Just want to make clearer about the relations between different choices of parameter values and the shape of the b_tot. There are four cases:


(a) bL>0,(b>1) and fNL>0: purple line. This means that galaxy is more correlated with matter fluctuations, and small scale galaxy fluctuation is correlated with large scale fluctuations, so b_tot at large scale becomes large. Is this right?

(b) bL<0 (b<1) and fNL>0: green line. Galaxy initially is anti-correlated with matter fluctuations (bL<0), therefore after evolution (extra 1 factor), Galaxy is less correlated with matter fluctuation and matter auto-correlation (0<b<1). fNL>0 means small scale gravity potential is correlated with large scale potential fluctuation, right? But how to understand these two things combined to give the large scale suppression?

In "pgfig1.pdf", we plot P_g(k), you can find that the green line and
purple line are combined with each other on k<10^(-3). Why these two sets of parameter choice give same power on very large scale?


(c)bL>0(b>1) and fNL<0: brown line. Why this set of parameter choice give a suppression on large scales.

(d) bL<0(b<1) and fNL<0: blue line. galaxy is initially anti-correlated
with matter fluctuation (bL<0), and small scale and large scale potential fluctuations are anti-correlated as well. Why this set of parameter choice results in a boost on large scales as well?

Thank you guys!