Mary Cesetti PhD Student

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Mary Cesetti PhD Student

• Degree thesis Padova Univesity
• PhD Padova University Supervisor
  Alessandro Pizzella Francesco Bertola
• ESO Vitacura
• Supervisor Valentin Ivanov
• -Lorenzo Morelli
• (Univ. Catolica, Chile)

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NUCLEAR STELLAR DISKS (NSD) IN ELLIPTICALS AND
BULGES
1st PhD. part
Spiral and S0 galaxies main disks
1-10 kpc scale lengths size
Elliptical galaxies embedded disks
100 pc 1 k scale lengths size
(Scorza Bender 1995 Seifert Scorza 1996)
Early type galaxies nuclear disks
10-50 pc scalelengths size
(Morelli et al. 2004 Krajnovic Jaffe 2004)
?
HST high resolution imaging
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Why study NSD?

• NSD as clues to formation scenario

• NSD as final product of star formation of a
  merging event

• NSD as finals product of secular evolution of a
  bar

?
Study of NSD stellar population by integrate
colors
The sample
NSD parameters have been studied for 12 galaxies
photometric observation in at least three bands
with HST
? NGC4570 (UBVI ) ? NGC4478 (BVI)
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• Bulge only ? Perfect elliptical isophotes
• Bulge Disk ? Disky isophotes
• Parameters of diskyness ? A4 coefficient
  profiles
• ISOPHOTE DISKYNESS IS ASSUMED AS THE SIGNATURE OF
  THE PRESENCE OF A NUCLEAR STELLAR DISK
• LIMITATIONS OF THE SB METHOD
• Disk detection possible only if inclination is i
  gt 50
• Effective for elliptical and S0 galaxies without
  dust

A4 gt 0 ? disky isophotes A4 0 ? perfect
elliptical isophote A4 lt 0 ? boxy isophotes
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SB method procedure

• Assumptions
• The bulge have perfectly elliptical isophote
• The disk is infinitely thin and exponential

• The method is iterative
• A disk is generated with
• I0 ? central surface brightness
• h ? scalelength
• i ? inclination
• A bulge image is obtained bulgegalaxy-disk
• A4 radial profiles is performed on the disk
  subtracted image
• Evaluation of the good quality of the model
• New values of I0, h, i

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Results
Error estimation

• FOR EACH DISK MODEL I DEFINED A NORMALIZED ?2
• THE MINIMUM VALUE OF ?2 CORRESPOND TO THE BEST
  FITTING MODEL.
• THEN I DERIVE THE CONFIDENCE LIMITS IN THE
  PARAMETERS SPACE

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NSD parameters

• Scale lengths consistent with each-other
• Inclinations consistent with each-other

?
NSD Color
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Age and chemical composition of stellar
populations

NGC4478 (Halliday at al. 2001) NGC4570 (van den
Bosch Emsellem 1998) complex kinematic
?
The two NSD stars are formed by pre-enriched gas
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2nd PhD. part
DEVELOP SPECTRAL DIAGNOSTIC OF STELLAR POPULATION
IN THE INFRARED FOR UNRESOLVED STELLAR
POPULATIONS IN GALAXIES

• Develop near-IR spectral indicators
• ? SOFI/NTT spectra for 18 elliptical galaxies
• test relations between H? ?Br?
• optical-IR features Mgb ? MgI 1.51?m
• for galaxies Mg2 ? CO 1.62 ?m

• Estimate metallicity (Mgb ? MgI 1.51 ?m )
• ? ISAAC/VLT spectra of 31 Starburst, active
• and normal galaxies

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An example
MgI