J/A+A/660/A79 BHeB stars in the Leo A galaxy (Lescinskaite+, 2022)
Recent star formation history of the dwarf irregular galaxy Leo A.
Lescinskaite A., Stonkute R., Vansevicius V.
<Astron. Astrophys. 660, A79 (2022)>
=2022A&A...660A..79L 2022A&A...660A..79L (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Photometry, UBVRI ; Photometry, H-alpha ;
Stars, ages
Keywords: galaxies: dwarf - galaxies: individual: Leo A (DDO 69) -
galaxies: stellar content
Abstract:
Leo A is a gas-rich dwarf irregular galaxy of low stellar mass and
metallicity. Its star formation history extends up to ∼10Gyr. A few
prominent HII regions indicate that star formation processes are
active in the galaxy to this day. In the present epoch, Leo A is a
highly isolated galaxy, which allows for it to be studied in a
self-propagating star formation regime.
Our aim is to study the recent star formation history of the Leo A
galaxy over the last ∼300Myr.
We analysed populations of main sequence (MS) and blue helium-burning
(BHeB - 'blue loop') stars using multi-colour photometry data
obtained with the Subaru/Suprime-Cam (B, V, R, I, Hα) and the
Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) (F475W
and F814W) cameras. We made use of colour-magnitude diagrams and
stellar isochrones to determine individual ages of the BHeB stars,
which enabled us to study the spatial distribution of these stars in
different age bins. In addition, we used Hα emission and HI
column density maps to study the relationship between young stellar
populations and the surrounding interstellar medium.
We found that significant differences are visible in the morphology of
stellar distributions represented by the BHeB and MS stars of
different ages. We also studied a well-known HI hole in the Leo A
galaxy and found that there is a noticeable difference in the surface
number density of stars in the western and eastern parts of the hole.
The bright young (<20Myr) MS stars residing in the western part of
the hole indicate the recent star-forming activity in this region
after the quiescent period of ∼300Myr. Furthermore, there is a shock
front (prominent in Hα) that closely resembles the shape of the
western edge of the Hi hole. This shock front could have been formed
by the combined stellar feedback from the young MS stars or a Type II
supernova located within the Hi hole. Additionally, an analysis of the
Suprime-Cam photometry in Hα and R passbands enabled us to
identify 17 stars with a prominent Hα emission
(Hα-R≤-0.06) which indicate the presence of early-type (Be,
B[e], or A-shell) emission-line stars in the Leo A galaxy.
Description:
We analysed populations of main sequence (MS) and blue helium-burning
(BHeB - blue loop) stars using multi-colour photometry data obtained
with the Subaru/Suprime-Cam (B, V, R, I, Hα) and HST/ACS (F475W
and F814W) cameras. We made use of colour-magnitude diagrams and
stellar isochrones to determine individual ages of the BHeB stars,
which enabled us to study the spatial distribution of these stars in
different age bins. In addition, we used Ha emission and HI column
density maps to study the relationship between young stellar
populations and the surrounding interstellar medium. We found that
significant differences are visible in the morphology of stellar
distributions represented by the BHeB and MS stars of different ages.
Additionally, an analysis of the Suprime-Cam photometry in Ha and R
passbands enabled us to identify 17 stars with a prominent Ha emission
(Hα-R←0.06) that indicate the presence of early-type (Be, B[e],
or A-shell) emission-line stars in the Leo A galaxy.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 89 115 BHeB stars in the Leo A galaxy
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See also:
J/ApJS/214/19 : Suprime-Cam wide-field photometry of Leo A (Stonkute+, 2014)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- ID Source identifier in Suprime-Cam catalogue,
JHHMMSS.ss+DDMMSS.s (1)
20- 29 F10.5 deg RAd Right ascension (J2000)
30- 38 F9.5 deg DEd Declination (J2000)
39- 45 F7.3 mag Vmag Johnson-Cousins V band magnitude
46- 52 F7.3 mag B-V Johnson-Cousins (B-V) colour index
53- 59 F7.3 mag V-I Johnson-Cousins (V-I) colour index
60- 66 F7.3 mag Rmag ? Johnson-Cousins R band magnitude
(Stonkute et al., 2022ApJS..259....6S 2022ApJS..259....6S)
67- 73 F7.3 mag Ha-R ? Johnson-Cousins (Ha-R) colour index
74- 79 F6.3 mag e_Rmag ? 1σ error in Rmag
80- 85 F6.3 mag e_Ha-R ? 1σ error in Ha-R
86- 89 I4 Myr Age Estimated age
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Note (1): From Stonkute et al. (2014ApJS..214...19S 2014ApJS..214...19S, Cat. J/ApJS/214/19).
Will be [SAH2014] JHHMMSS.ss+DDMMSS.s in Simbad.
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Acknowledgements:
Vladas Vansevicius, vladas.vansevicius(at)ff.vu.lt
(End) Patricia Vannier [CDS] 31-Mar-2022