J/A+A/614/A144 Photometry of stars in the LeoA HST WFC3 field (Stonkute+, 2018)
Dwarf irregular galaxy Leo A extends even farther, according to HST WFC3
photometry.
Stonkute R., Ceponis M., Lescinskaite A., Naujalis R., Vansevicius V.
<Astron. Astrophys. 614, A144 (2018)>
=2018A&A...614A.144S 2018A&A...614A.144S (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Photometry, HST ; Photometry, CCD
Keywords: galaxies: dwarf - galaxies: stellar content -
galaxies: individual: Leo A (DDO 69)
Abstract:
LeoA is an isolated gas-rich dwarf irregular galaxy of low stellar
mass and metallicity residing at the outskirts of the Local Group.
Ages of the stellar populations in LeoA range from ∼10Myr to ∼10Gyr.
A large stellar halo (up to the deprojected distance of ∼1.7kpc was
discovered based on Subaru wide-field photometry of red giant branch
stars.
We analysed HST WFC3 archive observation data in the field that is
partly located beyond the previously known limits of the LeoA galaxy.
We performed photometry of star-like objects in the F475W and F814W
passbands and studied the spatial distribution of the Leo A stars
below the horizontal branch. We report a discovery of stellar halo
populations (subgiants and faint red giants) in the Leo A galaxy
extending up to ∼2.3kpc deprojected distance from the galaxy centre.
Analysis of the colour-magnitude diagram suggests old (>5Gyr) stellar
populations of very low metallicity (Z∼0.0001).
Description:
We used archival HST WFC3 F475W and F814W passband observation data of
the LeoA galaxy downloaded from the Mikulski Archive for Space
Telescopes (MAST).
To perform stellar photometry, we used the software package DOLPHOT
2.0 (Dolphin, 2000PASP..112.1383D 2000PASP..112.1383D). We selected objects that had
measurements in both filters with magnitude errors (in any filter)
lower than 0.3mag. Then we visually inspected the measured objects in
the images and rejected those that lay on the obvious background
galaxies, bright MW stars, or large artefacts. This left us with N=756
objects.
Following the DOLPHOT prescription (Dolphin, 2000PASP..112.1383D 2000PASP..112.1383D), we
rejected diffuse sources that have overly negative sharpness in both
passbands and are therefore likely background galaxies or unresolved
blends of stars (sharpnessF457W>-0.099; sharpnessF814W>-0.078). As
a result of this selection, we ended up with 128 probable star-like
objects. However, some of these objects could still be unresolved
galaxies, Leo A blue stragglers, or Milky Way white dwarfs.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table.dat 58 128 Photometry parameters for 128 star-like objects
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See also:
J/AJ/123/3154 : RV light curves of variable stars in Leo A (Dolphin+, 2002)
J/ApJS/214/19 : Suprime-Cam wide-field photometry of Leo A (Stonkute+, 2014)
Byte-by-byte Description of file: table.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right ascension (J2000)
10- 18 F9.5 deg DEdeg Declination (J2000)
19- 25 F7.3 mag F475W Magnitude in the passband F475W
26- 31 F6.3 mag e_F475W Magnitude error in the passband F475W
32- 38 F7.3 --- shF475W Sharpness in the passband F475W
39- 45 F7.3 mag F814W Magnitude in the passband F814W
46- 51 F6.3 mag e_F814W Magnitude error in the passband F814W
52- 58 F7.3 --- shF814W Sharpness in the passband F814W
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Acknowledgements:
Vladas Vansevicius, vladas.vansevicius(at)ff.vu.lt
References:
Vansevicius et al. 2004ApJ...611L..93V 2004ApJ...611L..93V,
The full-fledged dwarf irregular galaxy Leo A.
(End) Patricia Vannier [CDS] 08-Jul-2018