J/A+A/472/785 Radio continuum survey of M33 (Tabatabaei+, 2007)
High-resolution radio continuum survey of M33. I. The radio maps.
Tabatabaei F.S., Krause M., Beck R.
<Astron. Astrophys. 472, 785 (2007)>
=2007A&A...472..785T 2007A&A...472..785T
ADC_Keywords: Galaxies, radio ; Radio continuum
Keywords: galaxies: individual: M33 - radio continuum: galaxies -
galaxies: magnetic field - galaxies: ISM
Abstract:
We study the exponential scale length of total radio emission, the
spectral index distribution, and the linear radio polarization in the
Scd galaxy M33. Observations were carried out using the 3.6cm dual
channel and the 6.2cm four-channel receivers of the 100-m Effelsberg
telescope along with the L-band VLA D-array at 20cm. High spatial
resolution and sensitivity in both total and linearly polarized radio
continuum emission from M33 were achieved. We found considerable
extended emission, not only from the main arms IS and IN, but also
from the weaker arms. The large-scale magnetic field exhibits
well-ordered spiral structure with almost the same orientation as
that of the optical spiral arms; however, it does not show a clear
structural correlation or anti-correlation with the optical arms.
There is a north-south asymmetry in polarization that is
frequency-dependent. We found that the ring mean spectral index versus
radius increases faster beyond R=4kpc. At each wavelength, the
exponential scale length is larger inside than outside R=4kpc. From
the larger scale lengths at R<4kpc, we conclude that star-forming
regions are mainly spread over the region R<4kpc without a dominant
nuclear concentration. Furthermore, at R>4kpc, a spatial
correlation between cosmic rays and star-forming regions may exist.
From the behavior of the mean spectral indices obtained from different
pairs of the radio continuum data at 3.6, 6.2, and 20cm, we confirm
that a decrease in the thermal fraction causes an increase in the
spectral index.
Description:
We present the total flux density map of M33 at 3.6cm (8350MHz). M33
was scanned along RA and DEC with a scanning velocity of 50 arcmin/min
on a grid of 30 arcsec. The scanned area of 40*50 arcmin was centered
on the nucleus of the galaxy. Combining the total number of 56
coverages this image is obtained. The half power beam width (HPBW) is
83.6 arcsec which corresponds to a linear resolution of about 335pc. A
Fits file of this image is given with a table of the total flux
density for each pixel (80*108 pixels). We use the radio convention
for the map units (microJy/beam). More information can be found in the
file header.
Objects:
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RA (2000) DE Designation(s) (File)
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01 33 51.0 +30 39 37 M33 = UGC 1117 (m33-3.6cmI.fits)
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
m33-3.6cmI.fits 2880 16 Total flux density map of M33 at 3.6cm (8.35GHz)
observed with the Effelsberg telescope
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Acknowledgements:
Fatemeh Tabatabaei, tabataba(at)mpifr-bonn.mpg.de
References:
Tabatabaei et al., 2007A&A...466..509T 2007A&A...466..509T
A multi-scale study of infrared and radio emission from Scd galaxy M33
(End) Patricia Vannier [CDS] 29-Jun-2007