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BEGIN:VEVENT
DTSTART;TZID=Atlantic/Canary:20100208T000000
DTEND;TZID=Atlantic/Canary:20100208T010000
UID:iactalks-148
X-WR-CALNAME: IAC Talks: Open Astronomy Seminars
X-ORIGINAL-URL: /iactalks/Talks/view/148
CREATED:2010-02-08T00:00:00+00:00
X-WR-CALDESC: IAC Talks upcomming talks
SUMMARY:The huge (but forgotten) population of weak line galaxies in the SD
 SS: AGN or just retired galaxies
DESCRIPTION:The huge (but forgotten) population of weak line galaxies in th
 e SDSS: AGN or just retired galaxies\nDr. Roberto Cid Fernandes\n\nThis ta
 lk is divided into two related parts. First, we will call your attention t
 o a basic, but often overlooked worrying fact, and presents ways of dealin
 g with it. The fact is: an enormous number of galaxies in surveys like the
  SDSS have emission lines which are too weak (low S/N) to be classified by
  usual schemes (ie, diagnostic diagrams). It turns out that most of these 
 are AGN-like, so ignoring them on the basis of low S/N (which most people 
 do) leaves as much as 2/3 of these emission line galaxies unaccounted for.
  The solution: We present a number of alternative methods to rescue this n
 umerous population from the classification limbo. We find that about 1/3 o
 f these weak-line galaxies are massive, metal rich star-forming systems, w
 hile the remaining 2/3 are more like LINERs. In the second part, we revisi
 t the old idea by Binette et al (1994) that post-AGB stars can account for
  the emission line properties of some galaxies. A "retired galaxy" model i
 s presented and compared to data in the SDSS. We find that about 1/4 of th
 e galaxies classified as LINERs in the SDSS are consistent with this model
 , where all ionizing radiation is of stellar origin. More dramatically, ne
 arly 100% of weak-line LINERs are perfectly consistent with being just ret
 ired galaxies, with no active nucleus. If these ideas are correct, contrar
 y to current practice, relatively few LINERs should be counted as bona fid
 e AGN.\n\n
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