J/A+A/440/783 OB associations in NGC 7793 (Pietrzynski+, 2005)
A survey for OB associations in the Sculptor Group spiral galaxy NGC 7793.
Pietrzynski G., Ulaczyk K., Gieren W., Bresolin F., Kudritzki R.P.
<Astron. Astrophys., 440, 783-789 (2005)>
=2005A&A...440..783P 2005A&A...440..783P
ADC_Keywords: Galaxies, photometry ; Associations, stellar
Keywords: Galaxy: open clusters and associations: individual: galaxy: NGC 7793
Abstract:
We report on the results from application of an objective algorithm
(PLC) to find OB associations, to B and V images of the Sculptor
spiral galaxy NGC 7793, which were obtained with the ESO VLT and FORS
instrument and basically cover the entire spatial extent of the
galaxy. We detected 148 associations. Statistical tests show that less
than 6 of these detections are caused by randomly concentrated blue
stars. In the size distribution, a sharp peak is observed at a value
of about 35 microradians, which corresponds to a linear diameter of
135pc, assuming a distance of 3.91Mpc to the galaxy. We also find 25
much larger objects. A second application of the PLC technique shows
that 20 of them are stellar complexes consisting of multiple
sub-associations with typical sizes on the order of 130pc. A
comparison of the size distribution of the detected OB associations in
NGC 7793 with observed distributions in other galaxies suggests that
the conditions in two Sculptor Group galaxies (NGC 300 and NGC 7793)
favour the formation of large associations. We provide a catalog
giving coordinates and physical parameters for all the associations
and stellar complexes we have found in our survey.
Description:
The observations were performed during two photometric nights in July
2001 with the ESO VLT and FORS1 instrument (see ESO website for
details) in imaging mode. The FORS1 field of view is approximately
6.8x6.8arcmin, and the pixel scale of the FORS1 detector is
0.2arcsec/pix. We obtained images in B, V, I, and Halpha filters for
two fields, which together cover almost the entire galaxy. The data
were obtained under 1-arcsec seeing conditions.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 39 148 Catalog of detected OB associations in NGC 7793
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- [PUG2005] Association name (AS NNN)
8- 9 I2 h RAh Right ascension (J2000)
11- 12 I2 min RAm Right ascension (J2000)
14- 17 F4.1 s RAs Right ascension (J2000)
19 A1 --- DE- Declination sign (J2000)
20- 21 I2 deg DEd Declination (J2000)
23- 24 I2 arcmin DEm Declination (J2000)
26- 27 I2 arcsec DEs Declination (J2000)
29- 31 I3 --- Nstar Number of stars in the association
33- 35 I3 urad angSize Angular size in µrad (∼ 0.2arcsec)
37- 39 I3 pc linSize Linear size in pc
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 28-Jul-2006