J/AJ/114/1458 The Carina Dwarf (Mighell 1997)
WFPC2 observations of the Carina dwarf spheroidal galaxy
Mighell K.J.
<Astron. J. 114, 1458 (1997)>
=1997AJ....114.1458M 1997AJ....114.1458M
ADC_Keywords: Galaxies, photometry
Mission_Name: HST
Abstract:
We present our analysis of Hubble Space Telescope Wide Field Planetary
Camera 2 observations in F555W (∼V) and F814W (∼I) of the Carina dwarf
spheroidal galaxy. The resulting V vs V-I color-magnitude diagrams
reach V∼27.1mag. The reddening of Carina is estimated to be
E(V-I)=0.08±0.02 mag. A new estimate of the distance modulus of
Carina, (m-M)0=19.87±0.11mag, has been derived primarily from
existing photometry in the literature. The apparent distance moduli in
V and I were determined to be (m-M)V=20.05±0.11mag and
(m-M)I=19.98±0.12mag, respectively. These determinations assumed
that Carina has a metallicity of [Fe/H]=-1.9±0.2dex. This
space-based observation, when combined with previous ground-based
observations, is consistent with (but does not necessarily prove) the
following star formation scenario. The Carina dwarf spheroidal galaxy
formed its old stellar population in a short burst (≲3Gyr) at about
the same time the Milky Way formed its globular clusters. The dominant
burst of intermediate-age star formation then began in the central
region of the galaxy where stars formed for several billion years
before the process of star formation became efficient enough in the
outer regions of the galaxy to allow for the formation of large
numbers of stars. There has been negligible star formation during the
last few billion years. This observation provides evidence that at
least some dwarf galaxies can have complex global star formation
histories with local variations of the rate of star formation as a
function of time and position within the galaxy.
(c) 1997 American Astronomical Society.
Description:
The FITS ASCII Table version of table2.dat is exactly as supplied by
the author.
Objects:
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RA (2000) DE Designation(s)
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06 41 37 -50 58.0 Carina dwarf galaxy = PGC 19441
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 39 3302 WFPC2 stellar photometry in the Carina dSph galaxy
table2.fit 2880 92 FITS ASCII Table version of table2.dat
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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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2- 10 I9 --- ID *Coded identification
13- 18 F6.3 mag Vmag V magnitude
21- 25 F5.3 mag e_Vmag rms error of V magnitude
27- 32 F6.3 mag V-I (V-I) color
35- 39 F5.3 mag e_V-I rms error of (V-I) color
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Note on ID:
The left-most digit of the ID gives the WFPC2 chip number where the
star may be found (2, 3, or 4). The right-most 4 digits of the ID
gives the x coordinate of the star multiplied by 10. The remaining
4 digits gives the y coordinate of the star multiplied by 10.
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Origin: AAS CD-ROM series, Volume 9, 1997 Lee Brotzman [ADS] 31-Oct-1997
(End) [CDS] 05-Feb-1998