J/A+A/572/A10 (BV) photometry in Carina dSph (de Boer+, 2014)
The episodic star formation history of the Carina dwarf spheroidal galaxy.
de Boer T.J.L., Tolstoy E., Lemasle B., Saha A., Olszewski E.W., Mateo M.,
Irwin M.J., Battaglia G.
<Astron. Astrophys. 572, A10 (2014)>
=2014A&A...572A..10D 2014A&A...572A..10D
ADC_Keywords: Galaxies, nearby ; Galaxies, photometry ; Photometry, UBV
Keywords: Local Group - galaxies: evolution - galaxies: stellar content -
galaxies: dwarf - Hertzsprung-Russell and C-M diagrams
Abstract:
We present deep photometry of the Carina dwarf Spheroidal galaxy in
the B,V filters from CTIO/MOSAIC, out to and beyond the tidal radius
of rell∼0.48°. The accurately calibrated photometry is combined
with spectroscopic metallicity distributions of Red Giant Branch stars
to determine the detailed star formation and chemical evolution
history of Carina.
The star formation history confirms the episodic formation history of
Carina and quantifies the duration and strength of each episode in
great detail, as a function radius from the centre. Two main episodes
of star formation occurred at old (>8Gyr) and intermediate (2-8Gyr)
ages, both enriching stars starting from low metallicities
([Fe/H]←2dex). By dividing the SFH into two components, we determine
that 60±9 percent of the total number of stars formed within the
intermediate age episode. Furthermore, within the tidal radius
(0.48° or 888pc) a total mass in stars of
1.07±0.08x106M☉ was formed, giving Carina a stellar
mass-to-light ratio of 1.8±0.8.
Combining the detailed star formation history with spectroscopic
observations of RGB stars, we are able to determine the detailed
age-metallicity relation of each episode and the timescale of
alpha-element evolution of Carina from individual stars. The oldest
episode displays a tight age-metallicity relation during ∼6Gyr with
steadily declining alpha-element abundances and a possible
alpha-element knee visible at [Fe/H]~-2.5dex. The intermediate age
sequence displays a more complex age-metallicity relation starting
from low metallicity and a sequence in alpha-element abundances with a
slope much steeper than observed in the old episode, starting from
[Fe/H]=-1.8dex and [Mg/Fe]∼0.4dex and declining to Mg-poor values
([Mg/Fe]←0.5dex). This indicates clearly that both episodes of star
formation formed from gas with different abundance patterns ,
inconsistent with simple evolution in an isolated system.
Description:
Table 1 provides the photometric magnitudes derived for stars in the
Carina dwarf galaxy. For each star, are provided: RA and Dec and
elliptical radius from the centre of Carina; VB magnitudes and errors;
VB Photometric quality flag.
Table 2 provides the star formation rate as a function of age for
three annuli in the Carina dwarf spheroidal galaxy. Rates are given
for both the solution derived with Dartmouth isochrones as well as
BaSTI isochrones.
Table 3 provides the star formation rate as a function of metallicity
[Fe/H] for three annuli in the Carina dwarf spheroidal galaxy. Rates
are given for both the solution derived with Dartmouth isochrones as
well as BaSTI isochrones.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 65 78514 BV photometry for all our targets in Carina dSph
table2.dat 143 31 Star formation rates as a function of age
table3.dat 130 9 Star formation rates as a function of metallicity
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See also:
J/AJ/115/1840 : BV photometry in Carina dwarf galaxy (Hurley-Keller+ 1998)
J/A+A/410/523 : Carina Spiral Feature ubvybeta photometry (Kaltcheva, 2003)
J/A+A/514/A59 : uvbyβ photometry in Carina. II (Kaltcheva+, 2010)
J/ApJ/667/963 : Near-infrared photometry of Carina nebula (Sanchawala+, 2007)
J/ApJ/649/201 : Carina dSph velocities and Washington photometry (Munoz+, 2008)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 11 F11.7 deg RAdeg Right ascension (J2000)
13- 23 F11.7 deg DEdeg Declination (J2000)
25- 31 F7.5 deg Rell [0/1.7] Ellipitcal radius from centre of Carina
33- 39 F7.3 mag Vmag [12.8/25.8] V magnitude
41- 46 F6.3 mag e_Vmag Error on V magnitude
48- 54 F7.3 mag Bmag [13.3/26.5] B magnitude
56- 61 F6.3 mag e_Bmag Error on B magnitude
63 I1 --- q_Vmag [1/3] Quality flag for V magnitude, 1=ok (1)
65 I1 --- q_Bmag [1/3] Quality flag for B magnitude, 1=ok (1)
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Note (1): Quality flag as follows:
0 = non-detection in this band
1 = perfect, all PSF parameters determined
3 = part of photometric binary (overlapping stars)
but PSF parameters determined
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 6 F6.3 Gyr Age Mean age of star formation history (SFH) bin
8- 11 F4.2 Gyr e_Age Binsize of SFH age bin
13- 22 F10.8 Msun/yr SFR1 Star formation rate using DSEP isochrones
in first annulus (0<rad<0.15deg)
24- 33 F10.8 Msun/yr e_SFR1 Error on SFR1
35- 44 F10.8 Msun/yr SFR2 Star formation rate using DSEP isochrones
in second annulus (0.15<rad<0.30deg)
46- 55 F10.8 Msun/yr e_SFR2 Error on SFR2
57- 66 F10.8 Msun/yr SFR3 Star formation rate using DSEP isochrones
in third annulus (0.30<rad<0.48deg)
68- 77 F10.8 Msun/yr e_SFR3 Error on SFR3
79- 88 F10.8 Msun/yr SFRBaS1 Star formation rate using BaSTI isochrones
in first annulus (0<rad<0.15deg)
90- 99 F10.8 Msun/yr e_SFRBaS1 Error on SFRBaS1
101-110 F10.8 Msun/yr SFRBaS2 Star formation rate using BaSTI isochrones
in second annulus (0.15<rad<0.30deg)
112-121 F10.8 Msun/yr e_SFRBaS2 Error on SFRBaS2
123-132 F10.8 Msun/yr SFRBaS3 Star formation rate using BaSTI isochrones
in third annulus (0.30<rad<0.48deg)
134-143 F10.8 Msun/yr e_SFRBaS3 Error on SFRBaS3
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 5 F5.2 [Sun] [Fe/H] Mean [Fe/H] of star formation history (SFH) bin
7- 10 F4.2 [Sun] e_[Fe/H] Binsize of Star Formation History bin in dex
12- 20 F9.2 Msun SFR1 Star formation rate (Msun/dex) using DSEP
isochrones in first annulus (0<rad<0.15deg)
22- 30 F9.2 Msun e_SFR1 Error on SFR1
32- 40 F9.2 Msun SFR2 Star formation rate (Msun/dex) using DSEP
isochrones in second annulus (0.15<rad<0.30deg)
42- 50 F9.2 Msun e_SFR2 Error on SFR2
52- 60 F9.2 Msun SFR3 Star formation rate (Msun/dex) using DSEP
isochrones in third annulus (0.30<rad<0.48deg)
62- 70 F9.2 Msun e_SFR3 Error on SFR3
72- 80 F9.2 Msun SFRB1 Star formation rate (Msun/dex) using BaSTI
isochrones in first annulus (0<rad<0.15deg)
82- 90 F9.2 Msun e_SFRB1 Error on SFRB1
92-100 F9.2 Msun SFRB2 Star formation rate (Msun/dex) using BaSTI
isochrones in second annulus (0.15<rad<0.30deg)
102-110 F9.2 Msun e_SFRB2 Error on SFRB2
112-120 F9.2 Msun SFRB3 Star formation rate (Msun/dex) using BaSTI
isochrones in third annulus (0.30<rad<0.48deg)
122-130 F9.2 Msun e_SFRB3 Error on SFRB3
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Acknowledgements:
Thomas de Boer, tdeboer(at)ast.cam.ac.uk, Institute of Astronomy, UK
(End) Thomas de Boer [Inst. of Astron., UK], Patricia Vannier [CDS] 11-Sep-2014