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BEGIN:VEVENT
DTSTART;TZID=Atlantic/Canary:20150326T103000
DTEND;TZID=Atlantic/Canary:20150326T113000
UID:iactalks-769
X-WR-CALNAME: IAC Talks: Open Astronomy Seminars
X-ORIGINAL-URL: /iactalks/Talks/view/769
CREATED:2015-03-26T10:30:00+00:00
X-WR-CALDESC: IAC Talks upcomming talks
SUMMARY:Pieces to the puzzle of high-redshift galaxies
DESCRIPTION:Pieces to the puzzle of high-redshift galaxies\nDr. Stefan Geie
 r\n\nOur Universe is filled with a mind-blowing diversity and different  t
 ypes and appearances of galaxies. Finding out about how they formed and ev
 olved is one of the most  challenging tasks in astronomy. When looking abo
 ut 10 billion years back, to an epoch about 3 billion  years after the big
  bang, we can see galaxies at earlier stages of their  lives. In this talk
 , studies of different kinds of galaxies in the early  universe will be pr
 esented. Two examples of the very intriguing population of massive quiesce
 nt z~2  galaxies were analyzed in terms of their stellar populations and  
 morphologies. As the spectroscopic sample is still small, especially for g
 alaxies at  the faint end of the luminosity function, we make use of the b
 iggest  available "telescopes" in the universe: We search for red z~2 gala
 xies whose apparent brightnesses have been  boosted by the Gravitational L
 ensing effect of intermediate redshift  galaxy clusters with available mas
 s models. Our findings indicate older ages for these galaxies than expecte
 d. Also,  their remarkable compactness was corroborated. Furthermore, I'm 
 going to present a study of a special case of so-called  Damped Lyman-alph
 a Absorbers (DLAs), with two intervening galaxies in the  line of sight of
  a higher-redshift QSO, which is also one example of  only about a dozen k
 nown galaxy counterparts of a DLA. It fits into the emerging paradigm that
  galaxies which are responsible  for higher metallicity DLAs are more mass
 ive and luminous than typical  DLA galaxies. Motivated by that particular 
 discovery, during the past few years we  have undertaken a survey targetin
 g candidate dust-reddened quasars  missing in the sample from Sloan Digita
 l Sky Survey. Spectroscopic follow-up with the NOT and the NTT has demonst
 rated a very  high success rate of our selection (>90%). The main motiv
 ation is to search for quasars reddened by foreground  dusty galaxies and 
 we have found several such examples. We have also serendipitously found qu
 asars with abnormal, very UV-steep  extinction curves as well as a large n
 umber of broad absorption line  quasars (BALs). The latter allow us to stu
 dy the dependence of the BAL QSO population on  redshift, reddening and lu
 minosity. The results show a strong evolution  of the BAL QSO fraction wit
 h cosmic time, with a peak at z~2.5 where  several quantities in the Unive
 rse are also found to peak or vary. In  addition,the dependence of this fr
 action with reddening and luminosity  provides new constraints on the mode
 ls for broad absorption origin in  quasars. We are currently carrying out 
 a pilot study of a search for even redder  quasars selected from a combina
 tion of SDSS, UKIDSS and WISE photometry  with the aim of selecting very d
 ust-obscurred quasars or high-redshift  BALs at z>2. Preliminary result
 s from the first run et the NOT in March  2015 of the brightest candidates
  show very promising results which will  also be briefly shown in the talk
 .
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