G'day from the land of ozzzzz
Understanding what happens to AGN and the ejected matter reducing in redshift with distance is an important point.
This paper is quite interesting.
[0812.0926] A Surprisingly High Pair Fraction for Extremely Massive Galaxies at z ~ 3 in the GOODS NICMOS Survey
A Surprisingly High Pair Fraction for Extremely Massive Galaxies at z ~ 3 in the GOODS NICMOS Survey
Authors: Asa F. L. Bluck, Christopher J. Conselice, Rychard J. Bouwens, Emanuele Daddi, Mark Dickinson, Casey Papovich, Haojing Yan
(Submitted on 4 Dec 2008 (v1), last revised 5 Dec 2008 (this version, v2))
Quote:
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Abstract: We calculate the major pair fraction and derive the major merger fraction and rate for 82 massive ($M_{*}>10^{11}M_{\odot}$) galaxies at $1.7 < z < 3.0$ utilising deep HST NICMOS data taken in the GOODS North and South fields. For the first time, our NICMOS data provides imaging with sufficient angular resolution and depth to collate a sufficiently large sample of massive galaxies at z $>$ 1.5 to reliably measure their pair fraction history. We find strong evidence that the pair fraction of massive galaxies evolves with redshift. We calculate a pair fraction of $f_{m}$ = 0.29 +/- 0.06 for our whole sample at $1.7 < z < 3.0$. Specifically, we fit a power law function of the form $f_{m}=f_{0}(1+z)^{m}$ to a combined sample of low redshift data from Conselice et al. (2007) and recently acquired high redshift data from the GOODS NICMOS Survey. We find a best fit to the free parameters of $f_{0}$ = 0.008 +/- 0.003 and $m$ = 3.0 +/- 0.4. We go on to fit a theoretically motivated Press-Schechter curve to this data. This Press-Schechter fit, and the data, show no sign of levelling off or turning over, implying that the merger fraction of massive galaxies continues to rise with redshift out to z $\sim$ 3. Since previous work has established that the merger fraction for lower mass galaxies turns over at z $\sim$ 1.5 - 2.0, this is evidence that higher mass galaxies experience more mergers earlier than their lower mass counterparts, i.e. a galaxy assembly downsizing. Finally, we calculate a merger rate at z = 2.6 of $\Re$ $<$ 5 $\times$ 10$^{5}$ Gpc$^{-3}$ Gyr$^{-1}$, which experiences no significant change to $\Re$ $<$ 1.2 $\times$ 10$^{5}$ Gpc$^{-3}$ Gyr$^{-1}$ at z = 0.5. This corresponds to an average $M_{*}>10^{11}M_{\odot}$ galaxy experiencing 1.7 +/- 0.5 mergers between z = 3 and z = 0.
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My opinion is that we do not know enough about the intrinsic properties and the workings of condensed matter found through out any galaxy and growing larger as it approaches the centre where we find huge condensed matter that we call black holes.
