
CosmoCoffee

[astroph/0509212] Age of High Redshift Objects  a Litmus Test for the Dark Energy Models

Authors:  Deepak Jain, Abha Dev 
Abstract:  The discovery of the quasar, the APM 08279+5255 at z = 3.91 whose age is 2.1
Gyr has once again led to ``age crisis''. The noticeable fact about this object
is that it cannot be accommodated in a universe with $\Omega_m = 0.27$,
currently accepted value of matter density parameter and $\omega =
\mathrm{constant}$. In this work, we explore the concordance of various dark
energy parameterizations ($w(z)$ models) with the age estimates of the old high
redshift objects. It is alarming to note that the quasar cannot be accommodated
in any dark energy model even for $\Omega_m = 0.23$, which corresponds to $1
\sigma$ deviation below the best fit value provided by WMAP. There is a need to
look for alternative cosmologies or some other dark energy parameterizations
which allow the existence of the high redshift objects. 

[PDF]
[PS] [BibTex] [Bookmark]

View previous topic :: View next topic 
Author 
Message 
Garth Antony Barber
Joined: 19 Jul 2005 Posts: 71 Affiliation: Published independent

Posted: September 09 2005 


Any comments on these extraordinary claims? 

Back to top 


Boud Roukema
Joined: 24 Feb 2005 Posts: 84 Affiliation: Torun Centre for Astronomy, University of Nicolaus Copernicus

Posted: September 09 2005 


Garth Antony Barber wrote:  Any comments on these extraordinary claims? 
The title is not so extraordinary: this is a good type of test. But the interesting question is how precise the 2.1Gyr estimate is.
If this estimate were 2.1 ± 0.1 Gyr (no h dependence) including random and systematic error, then it would start to become significantly (several sigma) in contradiction with the concordance values of the local cosmological parameters (e.g. 71,0.27,0.73,−1.0).
If it's 2.1 ± 0.5 Gyr (no h dependence) then it's not yet precise enough.
From a 5 minute scan of Hamann & Ferland (1993) + Komossa & Hasinger (2002) it is not obvious to me that we have 2.1 ± 0.1 Gyr (no h dependence), but maybe that's simply because 5 minutes is not enough. If you are interested, then please read the papers, understand them, and then you can summarise for us. :) 

Back to top 


Garth Antony Barber
Joined: 19 Jul 2005 Posts: 71 Affiliation: Published independent

Posted: September 09 2005 


Yes, the age is determined from the Fe/O and Fe/Ne relative abundances and it takes time to form Fe in the observed quantities; Fe/O ~ 3. It would be essential to firm up on the error bars of this age determination for APM08279+5255, is there any more recent information about this?
Jain & Dev seem to have pulled the value of 2.1 Gyr out of thin air, with no error bars at all. Is this a generally accepted value for that system or have they just 'made it up'? 

Back to top 


Garth Antony Barber
Joined: 19 Jul 2005 Posts: 71 Affiliation: Published independent

Posted: September 11 2005 


In answer to my last question I found http://www.ingentaconnect.com/content/bsc/mnr/2003/00000340/00000004/art00002
"Cosmological implications of APM 08279+5255, an old quasar at z= 3.91" Alcaniz J.S.; Lima J.A.S.; Cunha J.V, MNRAS, Volume 340, Number 4, April 2003, pp. L39L42(1) Quote:  The existence of old highredshift objects provides an important tool for constraining the expanding age of the Universe and the formation epoch of the first objects. In a recent paper, Hasinger, Schartel & Komossa reported the discovery of the quasar APM 08279 + 5255 at redshift z= 3.91 with an extremely high iron abundance, and estimated age of 2−3 Gyr. By assuming the lower limit for this age estimate and the latest measurements of the Hubble parameter as given by the HST key project, we study some cosmological implications from the existence of this object. In particular, we derive new limits on the dark matter and vacuum energy contribution. Our analysis is also extended to quintessence scenarios in which the dark energy is parametrized by a smooth component with an equation of state px= x x (−1 x < 0) . For flat models with a relic cosmological constant we show that the vacuum energy density parameter is constrained to be 0.78 , a result that is marginally compatible with recent observations from type Ia supernovae (SNe Ia) and cosmic microwave background (CMB). For quintessence scenarios the same analysis restricts the cosmic parameter to x −0.22 . Limits on a possible first epoch of quasar formation are also briefly discussed. The existence of this object pushes the formation era back to extremely high redshifts.  (emphasis mine)
So it looks as if Jain and Dev we quoting the lower end of that age range, with a possible lower error of −0.1 Gyr. May their conclusions therefore be of some significance? 

Back to top 




You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum

