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PRODID:UW-Madison-Physics-Events
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SEQUENCE:0
UID:UW-Physics-Event-1281
DTSTART:20080930T203000Z
DURATION:PT1H0M0S
DTSTAMP:20260423T010345Z
LAST-MODIFIED:20080929T130454Z
LOCATION:6515 Sterling Hall
SUMMARY:The Assembly of Galaxy Disks and Evolution of Galactic Structu
 res in COSMOS - Reconstructing the Hubble Sequence\, Astronomy Colloqu
 ium\, Kartik Sheth\, CALTECH
DESCRIPTION:We have analyzed the redshift-dependent fraction of galact
 ic bars over 0.2&lt\;z&lt\;0.84 in 2\,157 luminous face-on spiral gala
 xies from the COSMOS2-square degree field. Our sample is an order of m
 agnitude larger than that used in any previous investigation\, and is 
 based on substantially deeper imaging data than that available from ea
 rlier wide-area studies of high-redshift galaxy morphology. We find th
 at the fraction of barred spirals declines rapidly with redshift. Wher
 eas in the local Universe about 65% of luminous spiral galaxies contai
 n bars (SB+SAB)\, at z~0.84 this fraction drops to about 20%. Over thi
 s redshift range the fraction of strong (SB) bars drops from about 30%
  to under 10%. It is clear that when the Universe was half its present
  age\, the census of galaxies on the Hubble sequence was fundamentally
  different from that of the present day. A major clue to understanding
  this phenomenon has also emerged from our analysis\, which shows that
  the bar fraction in spiral galaxies is a strong function of stellar m
 ass\, integrated color and bulge prominence. The bar fraction in very 
 massive\, luminous spirals is about constant out to z~0.84 whereas for
  the low mass\, blue spirals it declines significantly with redshift b
 eyond z=0.3. There is also a slight preference for bars in bulge domin
 ated systems at high redshifts which may be an important clue towards 
 the co-evolution of bars\, bulges and black holes. Our results thus ha
 ve important ramifications for the processes responsible for galactic 
 downsizing\, suggesting that massive galaxies matured early in a dynam
 ical sense\, and not just as a result of the regulation of their star 
 formation rate. <br><br>
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URL:https://www.physics.wisc.edu/events/?id=1281
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