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BEGIN:VEVENT
DTSTART;TZID=Atlantic/Canary:20090128T000000
DTEND;TZID=Atlantic/Canary:20090128T010000
UID:iactalks-117
X-WR-CALNAME: IAC Talks: Open Astronomy Seminars
X-ORIGINAL-URL: /iactalks/Talks/view/117
CREATED:2009-01-28T00:00:00+00:00
X-WR-CALDESC: IAC Talks upcomming talks
SUMMARY:The large scale inhomogeneity of the galaxy distribution
DESCRIPTION:The large scale inhomogeneity of the galaxy distribution\nDr. F
 rancesco Sylos Labini\n\nThe Sloan Digital Sky Survey is currently the lar
 gest spectroscopic survey of extragalactic objects and one of the most amb
 itious observational programs ever undertaken in astronomy, measuring abou
 t 1 million redshifts and thus providing a three dimensional mapping of th
 e local universe up to a depth of several hundreds of Mpc. The main charac
 teristic of galaxy distribution in this survey, and in the Two degree Fiel
 d Galaxy redshift Survey completed few years ago, is that large scale stru
 ctures have been found to extend to scales of the order of hundreds of meg
 a parsecs. However the standard determination of a characteristic length s
 cale, statistically describing galaxy correlations, is of only few mega pa
 rsecs: the standard explanation of this apparent mismatch is that large sc
 ale structures have small amplitude relative to the average density. We sh
 ow that, in the newest galaxy samples, large scale structures are quite ty
 pical and correspond to large fluctuation in the galaxy density field, mak
 ing the standard interpretation untenable. We show that the standard stati
 stical analysis is affected by systematics which are due to inconsistent a
 ssumptions. We point out that standard theoretical models of structure for
 mation are unable to explain the existence of the large fluctuations in th
 e galaxy density field detected in these samples. This conclusion is reach
 ed in two ways: by considering the scale, determined by a linear perturbat
 ion analysis of a self-gravitating fluid, below which large fluctuations a
 re expected in standard models and through the determination of statistica
 l properties of mock galaxy catalogs generated from cosmological N-body si
 mulations. Finally we discuss the implications of this results in relation
  to recent attempts to describe inhomogeneous models in general relativity
  and to the recent discoveries of large scale coherent bulk flows.
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