J/A+AS/71/297 CCD UBV photometry of stars in Sex A (Aparicio+, 1987)
CCD photometry of resolved dwarf irregular galaxies. I. Sextans A.
Aparicio A., Garcia-Pelayo J.M., Moles M., Melnick J.
<Astron. Astrophys. Suppl. Ser. 71, 297 (1987)>
=1987A&AS...71..297A 1987A&AS...71..297A
ADC_Keywords: Galaxies, photometry ; Photometry, UBV ; Photometry, CCD
Keywords: galaxies: irregular - stellar content -
luminosity function, mass function
Abstract:
CCD UBV photometry of 2279 stars in Sextans A is presented.
Differences with the photometric scales of Sandage and Carlson
(1985AJ.....90.1019S 1985AJ.....90.1019S) and Hoessel et al. (1983ApJ...274..577H 1983ApJ...274..577H) are
discussed; recalibration of the Sandage and Carlson data for Cepheids
in Sextans A results in a smaller value for the distance modulus,
µ=25.6. A similar value for the distance modulus is obtained from
the colour-colour diagram. Colour-colour and colour-magnitude diagrams
for the whole galaxy and for different parts are presented indicating
a general star formation activity all over Sextans A. The contribution
of stars brighter than Mpg=-3 to the total blue light of the galaxy
amounts to 25%, a much higher value than what is found for other dwarf
irregular galaxies in the Local Group. The integrated birthrate per
unit mass of massive stars for the galaxy is found to be much higher
than in the Magellanic Clouds, suggesting that the rate in Sextans A
was probably smaller in the past. Different slopes for high mass and
low mass IMF parts are needed to account for its low surface
brightness. The formation of massive stars seems to be favoured for
systems of decreasing mass or, given the relation between total mass
and metal content, for galaxies of decreasing metallicity.
Objects:
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RA (2000) DE Designation(s)
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10 11 05.7 -04 42 28 Sextans A = UGCA 205 = PGC 29653
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 51 2279 CCD UBV photometry results
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See also:
J/AJ/116/2341 : UBVRI photometry in Sextans A (Van Dyk+ 1998)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- AGM [1/2279]+ Sequential number
( in Simbad)
6- 11 F6.2 pix Xpos X position (1)
13- 18 F6.2 pix Ypos Y position (1)
20- 24 F5.2 mag U-B ? U-B colour index
26- 29 F4.2 mag e_U-B ? rms uncertainty on U-B
31- 35 F5.2 mag B-V B-V colour index
37- 40 F4.2 mag e_B-V rms uncertainty on B-V
42- 46 F5.2 mag Vmag V magnitude
48- 51 F4.2 mag e_Vmag rms uncertainty on Vmag
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Note (1): x increases to the East, y increases to the Norh.
Origin is in the left down corner.
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History:
Prepared via OCR at CDS.
(End) James Marcout, Patricia Bauer [CDS] 29-Jul-2000