J/A+A/543/A61 SINFONI data cube of NGC 7552 (Brandl+, 2012)
High resolution IR observations of the starburst ring in NGC 7552.
One ring to rule them all?
Brandl B.R., Marti-Hernadez N.L., Schaerer D., Rosenberg M.,
van der Werf P.P.
<Astron. Astrophys. 543, A61 (2012)>
=2012A&A...543A..61B 2012A&A...543A..61B
ADC_Keywords: Galaxies, IR
Keywords: ISM: kinematics and dynamics - HII regions - galaxies: nuclei -
galaxies: starburst - galaxies: star clusters: general - infrared: ISM
Abstract:
Approximately 20% of all spiral galaxies display starburst activity in
nuclear rings of a few hundred parsecs in diameter. It is our main aim
to investigate how the starburst ignites and propagates within the
ring, leading to the formation of massive stellar clusters.
We observed the ring galaxy NGC 7552 with the mid-infrared (MIR)
instrument VISIR at an angular resolution of 0.3"-0.4" and with the
near-infrared (NIR) integral-field spectrograph SINFONI on the VLT,
and complement these observations with data from ISO and Spitzer.
The starburst ring is clearly detected at MIR wavelengths at the
location of the dust-extincted, dark ring seen in HST observations.
This "ring", however, is a rather complex annular region of more than
100 parsec width. We find a large fraction of diffuse [NeII] and PAH
emission in the central region that is not associated with the MIR
peaks on spatial scales of ∼30pc. We do not detect MIR emission from
the nucleus of NGC 7552, which is very prominent at optical and NIR
continuum wavelengths. However, we have identified nine unresolved MIR
peaks within the ring. The average extinction of these peaks is
AV=7.4 and their total infrared luminosity is
LIR=2.1x1010L☉. The properties of these peaks are typical
for MIR-selected massive clusters found in other galaxies. The ages of
the MIR-selected clusters are in the range of 5.9±0.3Myr. The age
spread among the clusters of 0.8Myr is small compared to the travel
time of ∼5.6Myr for half an orbit within the starburst ring. We find
no strong evidence for a scenario where the continuous inflow of gas
leads to the ongoing formation of massive clusters at the contact
points between galactic bar and starburst ring. Instead, it appears
more likely that the gas density build up more gradually over larger
ring segments, and that the local physical conditions govern cluster
formation. We note that the fundamental limitation on the accurate
derivation of cluster age, mass and initial mass function slope is the
lack of higher angular resolution. Resolving the highly embedded,
massive clusters requires milli-arcsecond resolution at infrared
wavelengths, which will be provided by the next generation of
instruments on extremely large telescopes (ELTs).
Objects:
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RA (2000) DE Designation(s)
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23 16 11.00 -42 34 59.0 NGC 7552 = IC 5294
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 70 2 List of FITS data cube files
fits/* . 2 *FITS data cube files
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Note on fits/*: All relevant technical data are included in the FITS header
of the data cube. The flux units are in [ergs/s/cm2/µm].
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 24 F5.3 arcsec/pix scale [0.125] Scale of the image
26- 27 I2 pix Nx Number of pixels along X-axis
28 A1 --- --- [x]
29- 30 I2 pix Ny Number of pixels along Y-axis
31 A1 --- --- [x]
32- 35 I4 --- Nz Number of slices along λ
37- 43 F7.5 um lmin Minimum wavelength (resolution=0.145nm)
45- 51 F7.5 um lmax Maximum wavelength (resolution=0.145nm)
53- 70 A18 --- FileName Name of FITS file in subdirectory fits
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Acknowledgements:
Bernhard Brandl, brandl(at)strw.leidenuniv.nl
(End) Bernhard Brandl [Leiden University], Patricia Vannier [CDS] 18-Jul-2012