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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
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SEQUENCE:0
UID:UW-Physics-Event-3534
DTSTART:20141120T213000Z
DTEND:20141120T230000Z
DTSTAMP:20260419T172043Z
LAST-MODIFIED:20141114T141310Z
LOCATION:4421 Sterling Hall
SUMMARY:The First Results From CHAOS: The Chemical Abundances Of Spira
 ls Project\, Astronomy Colloquium\, Danielle Berg\, Center for Gravita
 tion\, Cosmology and Astrophysics\, UW Milwaukee
DESCRIPTION:"The CHemical Abundances of Spirals (CHAOS) project seeks 
 to establish a broader understanding of the chemical evolution of spir
 al galaxies in general. CHAOS harnesses the combined power of the Larg
 e Binocular Telescope (LBT) with the large spectral range and sensitiv
 ity of the Multi Object Double Spectrographs (MODS) to observe “dire
 ct” abundances in a large sample of spiral galaxy H II regions. In t
 his manner\, we measure the largest sample of the highest quality spec
 tra to date in NGC 628\, with one or more temperature sensitive aurora
 l lines ([O III] λ4363\, [N II] λ5755\, and [S III]λ6312) being obs
 erved at a strength of 3σ or greater in 45 H II regions. This high qu
 ality\, homogeneous dataset allow us to examine trends in physical con
 ditions and abundances with an unprecedented statistical significance.
  This analysis provided some atypical results. The comparison of deriv
 ed temperatures where more than one auroral line is observed in an H I
 I region demonstrates\, unexpectedly\, that temperatures based on [S I
 II] λ6312 and [N II] λ5755 are consistent\, while those based on [O 
 II] λλ7320\,7330 and [O III] λ4363 can often show large discrepanci
 es. Understanding these temperature discrepancies will be a major goal
  for the CHAOS project. We examine the relative alpha-element abundanc
 es\, as well as measure the O/H and N/O gradients in NGC 628. We find 
 a large dispersion in O/H and posit that this dispersion represents an
  upper limit to the true dispersion in O/H at a given radius and that 
 some of that dispersion is due to systematic uncertainties arising fro
 m temperature measurements.”
URL:https://www.physics.wisc.edu/events/?id=3534
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