J/A+A/566/A44 gr photometry of Sextans A and Sextans B (Bellazzini+, 2014)
The extended structure of the dwarf irregular galaxies Sextans A and Sextans B.
Bellazzini M., Beccari G., Fraternali F., Oosterloo T.A., Sollima A.,
Testa V., Galleti S., Perina S., Faccini M., Cusano F.
<Astron. Astrophys. 566, A44 (2014)>
=2014A&A...566A..44B 2014A&A...566A..44B
ADC_Keywords: Galaxies, nearby ; Galaxies, photometry ; Photometry, ugriz
Keywords: galaxies: dwarf - Local Group - galaxies: structure - galaxies: ISM -
galaxies: stellar content
Abstract:
We present a detailed study of the stellar and HI structure of the
dwarf irregular galaxies Sextans A and Sextans B, members of the
NGC3109 association. We use newly obtained deep (r∼26.5) and wide
field g,r photometry to extend the Surface Brightness (SB) profiles of
the two galaxies down to muV∼31.0mag/arcsec2. We find that both
galaxies are significantly more extended than what previously traced
with surface photometry, out to ∼4kpc from their centers along their
major axis. Older stars are found to have more extended distribution
with respect to younger populations. We obtain the first estimate of
the mean metallicity for the old stars in Sex B, from the color
distribution of the Red Giant Branch, <[Fe/H]≥-1.6. The SB profiles
show significant changes of slope and cannot be fitted with a single
Sersic model. Both galaxies have HI discs as massive as their
respective stellar components. In both cases the HI discs display
solid-body rotation with maximum amplitude of ∼50km/s (albeit with
significant uncertainty due to the poorly constrained inclination),
implying a dynamical mass ∼109∼M☉, a mass-to-light ratio
M/LV∼25 and a dark to-barionic mass ratio of ∼10. The distribution
of the stellar components is more extended than the gaseous disc in
both galaxies. We find that the main, approximately round-shaped,
stellar body of Sex A is surrounded by an elongated low-SB stellar
halo that can be interpreted as a tidal tail, similar to that found in
another member of the same association (Antlia). We discuss these, as
well as other evidences of tidal disturbance, in the framework of a
past passage of the NGC3109 association close to the Milky Way, that
has been hypothesized by several authors and is also supported by the
recently discovered filamentary configuration of the association
itself
Description:
The tables present deep LBT/LBC g and r photometry of the stars having
image quality parameters (provided by DAOPHOTII) CHI≤2 and SHARP
within magnitude-dependent contours traced to include the bulk of
stellar objects.
The observations were achieved on the night og 2012-02-21 with the
Large Binocular Camera at the Large Binocular Telescope in binocular
mode; g images were acquired with the blue arm and r images with the
red arm of the telescope/camera. The astrometry and the photometry
were calibrated with stars in common with SDSS-DR9 (V/139).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
sex_a.dat 66 52598 Stellar photometry in the dwarf galaxy Sextans A
sex_b.dat 66 68396 Stellar photometry in the dwarf galaxy Sextans B
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See also:
J/A+AS/71/297 : CCD UBV photometry of stars in Sex A (Aparicio+, 1987)
J/AJ/110/2166 : Variables in Sextans dSph galaxy (Mateo+ 1995)
J/AJ/116/2341 : UBVRI photometry in Sextans A (Van Dyk+ 1998)
J/AJ/125/1261 : VI photometry of Sextans A Cepheids (Dolphin+, 2003)
J/AJ/126/2840 : BVI CCD photometry of Sextans dSph galaxy (Lee+, 2003)
J/AJ/127/2723 : Abundances of 3 supergiants in Sextans A (Kaufer+, 2004)
J/MNRAS/411/1013 : CaII triplet in Sextans dSph galaxy (Battaglia+, 2011)
Byte-by-byte Description of file: sex_a.dat sex_b.dat
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Bytes Format Units Label Explanations
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3- 8 I6 --- Seq Identification number within the galaxy (1)
9- 17 F9.3 mag gmag g magnitude
18- 24 F7.3 mag e_gmag Error of the g magnitude
25- 33 F9.3 mag rmag r magnitude
34- 40 F7.3 mag e_rmag Error of the r magnitude
41- 53 F13.7 deg RAdeg Right ascension in decimal degrees (J2000.0)
54- 66 F13.7 deg DEdeg Declination in decimal degrees (J2000.0)
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Note (1): the first digit in the identification number identifies the chip.
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Acknowledgements:
Michele Bellazzini, michele.bellazzini(at)oabo.inaf.it
(End) Patricia Vannier [CDS] 14-Apr-2014