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BEGIN:VEVENT
DTSTART;TZID=Atlantic/Canary:20130611T123000
DTEND;TZID=Atlantic/Canary:20130611T133000
UID:iactalks-504
X-WR-CALNAME: IAC Talks: Open Astronomy Seminars
X-ORIGINAL-URL: /iactalks/Talks/view/504
CREATED:2013-06-11T12:30:00+01:00
X-WR-CALDESC: IAC Talks upcomming talks
SUMMARY:Star formation driven by cold-flow accretion in the local Universe 
DESCRIPTION:Star formation driven by cold-flow accretion in the local Unive
 rse \nDr. Jorge Sánchez Almeida\n\nThe direct accretion of pristine gas s
 treams is predicted to be the main mode of galaxy disk growth in the early
  universe (cold-flows). We (think we) have discovered this physical proces
 s at work in the local Universe.  The finding is one of the outcomes of ou
 r in-depth study of local extremely metal poor (XMP) galaxies. I will expl
 ain the main observational properties of XMPs, in particular, their tenden
 cy to have cometary or tadpole morphology, with a bright peripheral clump 
 (the head) on a faint tail. Tadpole galaxies are rare in the nearby univer
 se but turn out to be very common at high redshift, where they are usually
  interpreted as disk galaxies in early stages  of assembling. We have foun
 d the heads to be giant HII regions displaced with respect to the rotation
  center, with the galaxy metallicity being smallest at the head and larger
  elsewhere.  The resulting chemical abundance gradient is opposite to the 
 one observed in local spirals, and suggests a recent gas accretion episode
  onto the head. Thus, local XMP galaxies seem to be primitive disks,  with
  their star formation sustained by accretion of external metal poor gas. I
  will argue how the same mechanism may be driving the star formation in ma
 ny other local galaxies. Ongoing observational projects to confirm these f
 indings and conjectures will be briefly mentioned.
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