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BEGIN:VEVENT
DTSTART;TZID=Atlantic/Canary:20110524T000000
DTEND;TZID=Atlantic/Canary:20110524T010000
UID:iactalks-282
X-WR-CALNAME: IAC Talks: Open Astronomy Seminars
X-ORIGINAL-URL: /iactalks/Talks/view/282
CREATED:2011-05-24T00:00:00+01:00
X-WR-CALDESC: IAC Talks upcomming talks
SUMMARY:Relationship between Hubble type and spectroscopic class in local g
 alaxies
DESCRIPTION:Relationship between Hubble type and spectroscopic class in loc
 al galaxies\nDr. Jorge Sánchez Almeida\n\nWe compare the Hubble type and 
 the spectroscopic class of the galaxies  with spectra in SDSS/DR7.  As it 
 is long known, elliptical galaxies tend  to be red  whereas spiral galaxie
 s tend to be blue, however,  this  relationship presents a large scatter, 
  which we measure and quantify in  detail. We compare the  Automatic Spect
 roscopic K-means based  classification (ASK) with most of the commonly use
 d morphological  classifications. All of them provide consistent results. 
 Given a  spectral class, the morphological type wavers with a standard dev
 iation   between 2 and 3 T types, and the same large dispersion characteri
 zes  the variability of spectral classes fixed the morphological type. The
   distributions of Hubble types given an ASK class are very skewed -- they
   present long tails that go to the late morphological types for the red  
 galaxies, and to the early morphological types for the blue  spectroscopic
  classes. The scatter is not produced by problems in the  classification, 
 and it remains when particular subsets are considered. A  considerable fra
 ction of the red galaxies are spirals (40--60 %), but  they never present 
 very late Hubble types (Sd or later). Even though red  spectra are not ass
 ociated with ellipticals, most ellipticals do have  red spectra: 97 % of t
 he ellipticals in the morphological catalog by  Nair & Abraham, used h
 ere for reference, belong to ASK 0, 2 or 3. It  contains only a 3 % of blu
 e ellipticals. The galaxies in the green  valley class (ASK~5) are mostly 
 spirals, and the AGN class (ASK 6)  presents a large scatter  of Hubble ty
 pes from E to Sd. We investigate  variations with redshift using a  volume
  limited subsample. From  redshift 0.25 to now the galaxies redden from AS
 K 2 to ASK 0, as  expected from the passive evolution of their stellar pop
 ulations. Two of  the ASK classes (1 and 4) gather edge-on spirals, and th
 ey may be  useful in studies requiring knowing the intrinsic shape of a ga
 laxy  (e.g., weak lensing calibration).
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