Ángeles I. Díaz, UAM
Marcelo Castellanos, OMP
Elena Terlevich, INAOE
HOW TO DEFINE A CIRCUMNUCLEAR REGION
1,5000
rad. externo
LOG(dist. al centro (Kpc))
1,0000
0,5000
radio interno
0,0000
radio nuclear
-0,5000
-1,0000
Datos del presente
trabajo
-1,5000
-23
-22
-21
-20
-19
-18
-17
-16
Magnitudes absolutas (B)
Buta & Crocker (1993)
logR1(Kpc) = -0.137 MB –2.4
Alvarez-Alvarez, 2002, PhD Thesis, UAM
HOW LUMINOUS ARE CNSFRs ?
Popescu & Hopp2000
Mayya 1994
Iglesias 1998
Alvarez-Alvarez 2002
Arsenault 1989
Terlevich et al 1991
HII GALAXIES
OBSERVATIONS
4.2 m WHT + ISIS
BLUE → R600B λλ 3600-7000 Å
RED → R600R λλ 8850-9650 Å
Average seeing
≈ 1.2 ´´
Slit width
1´´.5
Spectral resolution ≈ 2 Å
PA = 162 º
PA = 105 º
NGC 2903
D = 8.6 Mpc (Botinelli et al. 1984)
Scale 42 pc / ´´
NOT Hα contours
Planesas et al 1997
HST Hα image
(archive)
Observed regions are:
R1+R, R3, R4 and R6
PA = 10º
PA = 38º
NGC 3351
D = 10 Mpc (Graham et al. 1997)
Scale 50 pc / ´´
PA = 61º
NOT Hα contours
Planesas et al 1997
HST H 6000 Å image
(archive)
Observed regions are:
R1, R2, R3, R4, R5, R6 and R7
NGC 3304
D = 20 Mpc (Kenney et al. 1992)
Scale 100 pc / ´´
NOT Hα contours
Planesas et al 1997
HST H 6000 Å image
(archive)
Observed regions are:
R3+R4
EMISSION LINE SPECTRUM ANALYSIS
NGC 3351 R1
From [SII] lines, electron densities range from 180 to 650 cm-3, with
average values of around 350 cm-3, higher than found in GEHR
[OIII] lines (λλ 4959, 5007 Å) very weak → high metallicity
Measurement of t[OIII] requires detection of auroral [OIII] lines a
few percent of [OIII] λ 5007 Å → impossible
NGC 3351 R1
Measurement of other line temperatures possible, in principle.
Only in one region (R1+R2 in NGC 2903) we have succeded in
measuring t[SIII] by detecting the [SIII] λ 6312 Å line
[OI] λ 6300 Å
For this region we measure Te = 8400 K, higher than expected
in in regions of high metallicity ...
Measurement of other line temperatures possible, in principle.
Only in one region (R1+R2 in NGC 2903) we have succeded in
measuring t[SIII] by detecting the [SIII] λ 6312 Å line
[SIII]
For this region we measure Te = 8400 K, higher than expected
in in regions of high metallicity ...
Abundances for the rest of the regions require the use
of empirical methods
CNSFRs show values of
O23 = ([OII]+[OIII])/Hβ
which indicate oversolar
metallicities, but the
actual values are difficult
to estimate since O23
levels off.
At times [OIII] lines are
difficult to measure ...
O23 = ([OII]+[OIII])/Hβ
Hβ
[OIII]
O23 = ([OII]+[OIII])/Hβ
S23 = ([SII]+[SIII])/Hβ
CNSFR
O23 = ([OII]+[OIII])/Hβ
S23 = ([SII]+[SIII])/Hβ
C
N
S
F
R
The combined parameter
S23/O23 yields values of the
oxygen abundances higher
than twice solar.
IONIZING POPULATIONS
• Hα luminosities range from 3 x 1039 to 3 x 1040 erg/s
• Q(H) between 2 x 1051 and 2 x 1052 s-1
• M* between 5 x 105 and 5 x 106 M, for a Salpeter IMF
CIII 5696 Å
CIII 5808,12 Å
HeII 4686 Å
WR features present in, at least, 2 observed regions
which would imply ages between 3.5 and 4.5 Myr
Regarding the temperature of ionizing stars, CNSFRs
seem to share more properties with HII galaxies than
with disk GEHRs
[OII ] /[OIII ]
η ´=
[ SII ] /[ SIII ]
η´is a parameter
related to the shape of
the ionizing continuum .
Straight lines in this
plot are related to lines
of constant ionizing
temperature
CNSFRs seem to
have unexpectedly
high ionizing
temperatures
THE UNDERLYING STELLAR POPULATION
4,00
3,50
log(EW (H (Å))
3,00
2,50
2,00
1,50
1,00
Presente
trabajo
Alvarez-Alvarez
2002
Terlevich et al. 1991
Terlevich
Popescu & Hopp 2000
Popescu
0,50
0,00
0,10
0,60
1,10
1,60
2,10
2,60
log(EW.(Hβ)(Å))
Mar Álvarez-Álvarez, 2002, PhD Thesis, UAM
Underlying stellar populations are important and hamper
the analysis of emission line spectra
Hβ
NGC 2903 R4
Hβ
NGC 3351 R5
Preliminar application of population synthesis models point to a
composite stellar population with two “bursts”, one with an age of a
few Myr responsible for the ionization and an older one of up to 1
Gyr with contributions of 10 % and 90 % to the total mass of the
region respectively.
THE MASS OF CNSFRS
NGC 2903 R4
NGC 3351 R2
We have measured stellar
velocity dispersions from
the CaT lines finding values
between 15 and 28 Km/s
and corresponding
dynamical masses between
107 and 108 M which would
be consistent with our
preliminar stellar
population modelling.
See Poster by Hägele et
al. for details