J/A+A/630/A116 Tucana dSph CMD and star formation history (Savino+, 2019)
The HST/ACS star formation history of the Tucana dwarf spheroidal galaxy:
clues from the horizontal branch.
Savino A., Tolstoy E., Salaris M., Monelli M., de Boer T.J.L.
<Astron. Astrophys. 630, A116 (2019)>
=2019A&A...630A.116S 2019A&A...630A.116S (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Stars, ages ; Photometry, HST ; HR diagrams
Keywords: galaxies: dwarf - galaxies: evolution - galaxies: stellar content -
Hertzsprung-Russell and C-M diagrams - stars: horizontal-branch -
stars: mass-loss
Abstract:
We report a new star formation history for the Tucana dwarf spheroidal
galaxy, obtained from a new look at a deep HST/ACS colour-magnitude
diagram. We combined information from the main sequence turn-off and
the horizontal branch to resolve the ancient star formation rates on a
finer temporal scale than previously possible. We show that Tucana
experienced three major phases of star formation, two very close
together at ancient times and the last one ending between 6 and 8 Gyr
ago. We show that the three discrete clumps of stars on the horizontal
branch are linked to the distinct episodes of star formation in
Tucana. The spatial distribution of the clumps reveals that each
generation of stars presents a higher concentration than the previous
one. The simultaneous modelling of the horizontal branch and the main
sequence turn-off also allows us to measure the amount of mass lost by
red giant branch stars in Tucana with unprecedented precision,
confirming dwarf spheroidals to be excellent laboratories to study the
advanced evolution of low-mass stars.
Description:
Photometry of the Tucana dwarf spheroidal galaxy, transformed into the
absolute photometric reference frame. Data obtained with the Advanced
Camera for Survey on board of the Hubble Space Telescope. The best-fit
star formation history (Table 1 in the paper) is also presented.
Objects:
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RA (ICRS) DE Designation(s)
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22 41 49.6 -64 25 10 Tucana dSph = LEDA 69519
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 44 260 Star formation history
phot.dat 50 54223 HST/ACS photometry
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See also:
J/A+A/315/40 : Photometry of the Tuc dwarf galaxy (Saviane, 1996)
J/ApJ/699/1742 : LCID project. I. Cetus and Tucana variables (Bernard+, 2009)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 5 F5.2 --- [alpha/Fe] Mean alpha enhancement of the bin
9- 13 F5.2 --- [Fe/H] Mean [Fe/H] of the bin
16- 20 F5.2 Gyr Age Mean look back time of the bin
25- 32 E8.2 Msun/yr SFR Star formation rate in the bin
37- 44 E8.2 Msun/yr e_SFR Uncertainty on the star formation rate
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Byte-by-byte Description of file: phot.dat
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Bytes Format Units Label Explanations
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8- 14 F7.4 mag F475W Magnitude in the F475W band
20- 26 F7.4 mag e_F475W ?=-9.9999 Error on the F475W magnitude (1)
32- 38 F7.4 mag F814W Magnitude in the F814W band
44- 50 E7.4 mag e_F814W ?=-9.9999 Error on the F814W magnitude (1)
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Note (1): Entries with photometric uncertainty values of -9.9999 are known
RR Lyrae and do not have a photometric uncertainty estimate.
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Acknowledgements:
Alessandro Savino, A.savino(at)uni-heidelberg.de
(End) A. Savino [ZAH-Heidelberg, Germany], P. Vannier [CDS] 13-Sep-2019