J/A+A/544/A73 BVI photometry of Fornax dSph galaxy (de Boer+, 2012)
The star formation and chemical evolution history of the Fornax dwarf spheroidal
galaxy.
de Boer T.J.L., Tolstoy E., Hill V., Saha A., Olszewski E.W., Mateo M.,
Starkenburg E., Battaglia G., Walker M.G.
<Astron. Astrophys. 544, A73 (2012)>
=2012A&A...544A..73D 2012A&A...544A..73D
ADC_Keywords: Galaxies, nearby ; Galaxies, photometry ; Photometry, UBVRI
Keywords: galaxies: dwarf - galaxies: evolution - galaxies: stellar content -
Local Group - Hertzsprung-Russell and C-M diagrams
Abstract:
We present deep photometry in the B,V and I filters from CTIO/MOSAIC
for about 270.000 stars in the Fornax dwarf Spheroidal galaxy, out to
a radius of rell∼0.8°. By combining the accurately calibrated
photometry with the spectroscopic metallicity distributions of
individual Red Giant Branch stars we obtain the detailed star
formation and chemical evolution history of Fornax. Fornax is
dominated by intermediate age (1-10Gyr) stellar populations, but also
includes ancient (10-14Gyr), and young (<1Gyr) stars. We show that
Fornax displays a radial age gradient, with younger, more metal-rich
populations dominating the central region. This confirms results from
previous works. Within an elliptical radius of 0.8 degrees, or 1.9kpc
from the centre, a total mass in stars of 4.3*107M☉ was
formed, from the earliest times until 250Myr ago. Using the detailed
star formation history, age estimates are determined for individual
stars on the upper RGB, for which spectroscopic abundances are
available, giving an age-metallicity relation of the Fornax dSph from
individual stars. This shows that the average metallicity of Fornax
went up rapidly from [Fe/H]←2.5dex to [Fe/H]=-1.5dex between 8-12Gyr
ago, after which a more gradual enrichment resulted in a narrow,
well-defined sequence which reaches [Fe/H]~-0.8dex, ∼3Gyr ago. These
ages also allow us to measure the build-up of chemical elements as a
function of time, and thus determine detailed timescales for the
evolution of individual chemical elements. A rapid decrease in [Mg/Fe]
is seen for the stars with [Fe/H]>-1.5dex, with a clear trend in age.
Description:
Deep optical photometry of the Fornax dSph in the B, V and I filters
was obtained using the CTIO 4-m MOSAIC II camera over 9 nights in
October 2008 and November 2009. Deep photometry for the outer fields
was obtained as part of observing proposal 2008B-0397 (PI M. Mateo)
supplemented by deep pointings covering the centre of Fornax as part
of observing proposal 2009B-0157 (PI A. Saha). Our observing strategy
was to obtain several non-dithered, long (600s) exposures for each
pointing, which were stacked together to obtain the deepest photometry
possible. Short (10s, 90s) exposures were also obtained, in order to
sample the bright stars that are saturated in the deep images.
In order to ensure accurate photometric calibration of the data set,
several fields were observed in Fornax using the 0.9m CTIO telescope,
under photometric conditions. Furthermore, observations were also made
of Landolt standard fields (Landolt 1992, Cat II/183; Landolt 2007,
Cat. J/AJ/133/2502) covering a range of different airmass and colour.
Medium and high resolution spectroscopic observations are available
for individual stars on the RGB in Fornax, giving measurements of
[Fe/H] and the detailed abundance patterns of individual stars, from
Battaglia et al. 2006, Cat. J/A+A/459/423; 2008, Cat. J/MNRAS/383/183);
Starkenburg et al. 2010A&A...513A..34S 2010A&A...513A..34S; Letarte et al. 2010, Cat.
J/A+A/523/A17
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 75 276283 VBI photometry for all our targets in Fornax
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See also:
J/PASP/110/533 : BR photometry of Fornax bright stars (Stetson+ 1998)
J/AJ/123/840 : VI photometry of variable stars in Fornax (Bersier+, 2002)
J/AJ/127/840 : VRI photometry of Fornax red giants (Pont+, 2004)
J/AJ/131/912 : BR photometry of Fornax dSph center (Olszewski+, 2006)
J/AJ/131/2114 : Radial velocities in Fornax dSph (Walker+, 2006)
J/A+A/459/423 : VI and [Fe/H] of Fornax dSph RGB stars (Battaglia+, 2006)
J/A+A/467/1025 : JHK photometry of Fornax red giant branch (Gullieuszik+ 2007)
J/ApJ/685/947 : SX Phe stars in Fornax. II. (Poretti+, 2008)
J/ApJ/701/1323 : Variable stars in Fornax dSph. III. (Greco+, 2009)
J/MNRAS/394/795 : AGB stars in Fornax dwarf spheroidal galaxy (Whitelock+ 2009)
J/A+A/523/A17 : Individual stars in Fornax dSph center (Letarte+, 2010)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 h RAh Right Ascension J2000 (hours)
4- 5 I2 min RAm Right Ascension J2000 (minutes)
7- 11 F5.2 s RAs Right Ascension J2000 (seconds)
13 A1 --- DE- Declination J2000 (sign)
14- 15 I2 deg DEd Declination J2000 (degrees)
17- 18 I2 arcmin DEm Declination J2000 (arcminutes)
20- 24 F5.2 arcsec DEs Declination J2000 (arcseconds)
26- 32 F7.3 mag Vmag V magnitude
34- 39 F6.3 mag e_Vmag ?=0 Error on V magnitude
41- 47 F7.3 mag Bmag ?=-59 B magnitude
49- 54 F6.3 mag e_Bmag ?=0 Error on B magnitude
56- 62 F7.3 mag Imag ?=-79 I magnitude
64- 69 F6.3 mag e_Imag ?=0 Error on I magnitude
71 I1 --- q_Vmag [0/3] Quality flag for V magnitude (1)
73 I1 --- q_Bmag [0/3] Quality flag for B magnitude (1)
75 I1 --- q_Imag [0/3] Quality flag for I magnitude (1)
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Note (1): Quality flag as follows:
1 = perfect, all PSF parameters determined,
3 = part of photometric binary (overlapping stars) but PSF
parameters determined
0 = non-detection in this band
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Acknowledgements:
Thomas de Boer, deboer(at)astro.rug.nl
History:
* 27-Jun-2012: Original version (sign of declination wrong)
* 23-Oct-2012: Version with corrected declination (from Thomas de Boer)
(End) T. de Boer [Kapteyn Inst., The Netherlands], P. Vannier [CDS] 27-Jun-2012