J/A+AS/142/347 BVRI photometry of NGC 6789 (Drozdovsky+, 2000)
The stellar content and distance to the nearby
blue compact dwarf galaxy NGC 6789.
Drozdovsky I., Tikhonov N.
<Astron. Astrophys. Suppl. Ser. 142, 347 (2000)>
=2000A&AS..142..347D 2000A&AS..142..347D
ADC_Keywords: Galaxies, nearby ; Photometry, UBVRI ; Photometry, CCD
Keywords: nearby galaxies - dwarf galaxies - distance moduli - star content
Abstract:
In this paper we present the results of a detailed B, V, R, I, and
Hα study of the isolated nearby blue compact dwarf (BCD) galaxy
NGC 6789. The observed galaxy has not yet been resolved into stars up
to now. On CCD frames obtained with 6m BTA telescope and 2.5m Nordic
telescope the galaxy is well resolved. Its colour-magnitude diagram
confirms the two component (core-halo) galaxy morphology, which
consists of two stellar populations distinct in structure and colour:
an inner high surface-brightness young population within 150pc from
the center of the galaxy, and a relatively low surface-brightness
intermediate-age population extending out to at least 600pc. The
distance to the galaxy, estimated from the tip of the red giant branch
(TRGB) is 2.1Mpc which places NGC 6789 close to the Local Group. From
the mean colour of the RGB, the mean metal abundance of the halo
population is estimated as [Fe/H]≃-1dex.
Description:
Results of the DAOPHOT/ALLSTAR photometry of the resolved stars in the
nearby blue compact dwarf galaxy NGC 6789. Based on observations made
with the 2.5m Nordic (La Palma, Spain) telescope.
Objects:
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RA (2000) DE Designation(s)
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19 16 41.9 +63 58 22 NGC 6789
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 46 337 Stellar photometry of NGC 6789
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See also:
J/A+AS/124/559 : VI photometry of dwarf galaxies (Karanchentsev+ 1997)
J/A+AS/128/459 : BV photometry of irregular galaxies (Makarova+ 1998)
J/A+AS/131/1 : BVI photometry of 5 CVn cloud galaxies (Karachentsev+ 1998)
J/A+AS/133/181 : BVI imaging of 20 irregular galaxies (Makarova+ 1998)
J/A+AS/142/425 : BVRI photometry of 6 galaxies (Drozdovsky+, 2000)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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7- 9 I3 --- Ident Running number
11- 14 I4 pix Xpos X coordinate (1)
16- 19 I4 pix Ypos Y coordinate (1)
22- 26 F5.2 mag Vmag V magnitude
28- 32 F5.2 mag V-I V-Ic colour index (4)
34- 38 F5.2 --- Sharp Stellar sharpness (2)
40- 43 F4.2 --- Chi ALLSTAR stellar image quality diagnostic
(see Stetson 1994)
46 A1 --- Locate Location in reference to the galaxy (3)
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Note (1): 1 pix = 0.11arcsec. North is to the left, East is to the top.
The lower left corner corresponds to X=0, Y=0 of the frame coordinates
given in the photometry tables, i.e. X increases to the South and Y
to the East.
Note (2): Sharp is a measure of the difference between the observed width
of the object and the width of the PSF model
Note (3): For the analysis of stellar content, the observed field has been
divided into several parts as indicated in the figure 1 caption
of the Paper.
0: The central region of NGC 6789.
1: The perefery region of NGC 6789.
2: Foreground stars
Note (4): As it was shown in our latest paper submitted to the ApJL
(Drozdovsky, Schulte-Ladbeck et al., 2001) and based on the HST photometry
these data are not deep enough to locate the tip of the red giant branch.
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Acknowledgements: Igor Drozdovsky
References:
Stetson P.B., 1994PASP..106..250S 1994PASP..106..250S
(End) Patricia Bauer [CDS] 23-Nov-2000