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BEGIN:VEVENT
DTSTART;TZID=Atlantic/Canary:20081024T000000
DTEND;TZID=Atlantic/Canary:20081024T010000
UID:iactalks-50
X-WR-CALNAME: IAC Talks: Open Astronomy Seminars
X-ORIGINAL-URL: /iactalks/Talks/view/50
CREATED:2008-10-24T00:00:00+01:00
X-WR-CALDESC: IAC Talks upcomming talks
SUMMARY:(1) Stellar kinematics in double-barred galaxies: the sigma-hollows
   (2) A colorful view on the outskirt of spiral galaxies: clues on disk-fo
 rmation scenarios
DESCRIPTION:(1) Stellar kinematics in double-barred galaxies: the sigma-hol
 lows  (2) A colorful view on the outskirt of spiral galaxies: clues on dis
 k-formation scenarios\nMiss Adriana de Lorenzo-Cáceres, Miss Judit Bakos\
 n\n(1) We present SAURON integral-field stellar velocity and velocity disp
 ersion maps for four double-barred early-type galaxies: NGC2859, NGC3941,N
 GC4725 and NGC5850. The presence of the nuclear bar is not evident from th
 e radial velocity, but it appears to have an important effect in the stell
 ar velocity dispersion maps: we find two sigma-hollows of amplitudes betwe
 en 10 and 40 km/s at either sides of the center, at the ends of the nuclea
 r bars. We have performed numerical simulations to explain these features.
  Ruling out other possibilities, we finally conclude that, although the si
 gma-hollows may be originated by a younger stellar population component wi
 th low velocity dispersion, more likely they are an effect of the contrast
  between two kinematically different components: the high velocity dispers
 ion of the bulge and the ordered motion (low velocity dispersion) of the n
 uclear bar.\n\n\n  \n\n(2) We have explored radial color and stellar surfa
 ce mass density profiles for a sample of 85 late-type galaxies with availa
 ble deep (down to ~27.0 mag/arcsec2 SDSS g'- and r'-band surface brightnes
 s profiles. About 90% of the light profiles have been classified as broken
  exponentials, exhibiting either truncations (Type II galaxies) or antitru
 ncations (Type III galaxies). Their associated color profiles show signifi
 cantly different behavior. For the truncated galaxies a radial inside-out 
 bluing reaches a minimum of (g' - r')  = 0.47 +/- 0.02 mag at the position
  of the break radius, this is followed by a reddening outwards. The anti-t
 runcated galaxies reveal a more complex behavior: at the break position (c
 alculated from the light profiles) the color profile reaches a plateau reg
 ion - preceded with a reddening - with a mean color of about (g' - r') = 0
 .57 +/- 0.02 mag. Using the color to calculate the stellar surface mass de
 nsity profiles reveals a surprising result. The breaks, well established i
 n the light profiles of the Type II galaxies, are almost gone, and the mas
 s profiles resemble now those of the pure exponential Type I galaxies. Thi
 s result suggests that the origin of the break in Type II galaxies are mos
 t likely to be a radial change in stellar population, rather than being ca
 used by an actual drop in the distribution of mass. The  anti-truncated ga
 laxies on the other hand preserve their shape to some extent in the stella
 r surface mass density profiles. We find that the stellar surface mass den
 sity at the break for truncated (Type II) galaxies is 13.6 +/- 1.6 Msun/pc
 2 and 9.9 +/- 1.3 Msun/pc2 for the anti-truncated (Type III) ones. We esti
 mate that ~15% of the total stellar mass in case of Type II galaxies and ~
 9% in case of Type III galaxies are to be found beyond the measured break 
 radii.\n\n\n
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