1. The nuclear starburst of M83 revealed with SINFONI
Liesbeth Vermaas
Paul van der Werf (Leiden Observatory)
M83 large SAB(s)c, distance 4.5 Mpc
nuclear starburst - offset from optical nucleus
= optical peak
× = center K-isophotes ×
Questions: - Double nucleus? center K-isophotes
- Where is the dynamical center?
Conclusions from SINFONI data:
- dynamical nucleus offset from optical peak by 3″
- no mass concentration detected at dynamical nucleus
- mass of optical peak ~108 M (dynamics)
M83: large nearby spiral hosting a nuclear starburst. (see talk by Lundgren) It has some peculiarities:
The starburst is offset from the optical nucleus.
Thatte noted that the center of the K-band isophotes does not coincide with the optical nucleus. Some groups have suggested that there is a double nucleus.
From our SINFONI observations, we conclude that optical peak is the mass-peak, but that the dynamical center is offset from the optical peak.
We also conclude that there is no sign of a mass concentration at this dynamical nucleus
K-band isophotes (Thatte et al. 2000)

2. VLT/SINFONI: near-IR 1-2.5 μm integral field spectroscopy
3 pointings in central 15''x15'' = 330x330 pc
M83: nuclear starburst
8'' = 175 pc
Brγ
young stars
K-band
(super)giants
H2 flux
15'' = 330 pc
44 pc
2''
starburst offset!
We have near infrared data taken with SINFONI, the integral field spectrometer on UT4 of the VLT. Most of the central 15 by 15 arcseconds were mapped with 3 field of 8 by 8 arcseconds.
This is the result of the SINFONI observations. 1 arcsecond corresponds to 22 parsec.
Middle: The 3 observed fields. K-band continuum, with the optical peak standing out. This traces the supergiant stage of the star formation.
Left: Br-gamma recombination line from HII regions around the hot, young stars, the first (observable) stage of the starburst. None of it is associated with the optical peak.
Warm molecular gas, H micron line. Most of the gas is concentrated on the optical peak, some associated with the star formation site in the upper field
= optical peak

3. from dynamical nucleus (×) inner-outer edge 2.5 - 5.0''
Gas dynamics from H2 (2.12μm)
H2 flux
H2 velocity × ×
Ring in M83:
optical peak ( ) offset 3''
from dynamical nucleus (×)
inner-outer edge ''
i=24°, PA=50° and position
adopted from CO observations
by Sakamoto et al. 2004
(P,V) diagram
position
velocity (km/s)
= optical peak
× = dynamical nucleus
rotating ring
Explain velocity field along line of sight (inclination 24deg):
First show the field of the optical peak. Nucleus, gradient, (P,V) nucleus
Larger scale: have to see it in perspective
We see a ring (point out), because of inclination
position velocity diagram: along the slice, where is the ring. What is the center X
Sakamoto et al. also found a ring of CO-gas (mm-interferometry) on that position,
and this coincides with Thatte’s center of K-isophotes as well.
6. Test the ring: take the velocity as function of position angle, this should result in a
sine-curve (corrected for inclination effects)
NB: aanpassen positie ring, binnen- en buitenrand. PA-V diagram tot 360gr.
Corrigeren voor inclinatie: ring-vorm en diagram. ×

4. - dynamical nucleus (×) offset from optical peak ( ) by 3"
Stellar dynamics from CO-absorption (2.29μm)
= optical peak
× = dynamical nucleus
stellar velocity [-80,80] km/s
velocity dispersion σ [0,80] km/s
σ:
NO CLEAR
PEAK! H2 × ×
Conclusions:
- dynamical nucleus (×) offset from optical peak ( ) by 3"
- no mass concentration detected at dynamical nucleus
- mass of optical peak ( ) ~108 M (dynamics)
Also gradient in velocity field nucleus, but also on larger scale symmetric
If there would be a mass concentration, would expect a peak in the velocity dispersion: but is not observed! No clear peak standing out. (some kind of peak on the optical peak site)
We conclude that the nucleus is not just an (old) big star cluster, the mass is too high (10^8 from dynamics). it could be the leftover of a captured dwarf galaxy.
NB: kleurschaal sigma-figuur