J/AJ/113/1001 Stellar photometry in NGC 147 (Han+ 1997)
Stellar Populations in the Dwarf Elliptical Galaxy NGC 147
Han M., Hoessel J.G., Gallagher J.S.III, Holtzman J., Stetson P.B.,
Trauger J., Ballester G.E., Burrows C., Clarke J., Crisp D.,
Griffiths R., Grillmair C., Hester J., Krist J., Mould J.R., Scowen P.,
Stapelfeldt K., Watson A., Westphal J.
<Astron. J. 113, 1001 (1997)>
=1997AJ....113.1001H 1997AJ....113.1001H
ADC_Keywords: Galaxies, photometry
Mission_Name: HST
Abstract:
Deep V and I CCD images in a central and an outer field of the Local
Group dwarf elliptical galaxy NGC 147 have been obtained with the Wide
Field and Planetary Camera-2 (WFPC2) on board of the Hubble Space
Telescope. The color-magnitude diagram shows a number of interesting
features, including a well defined red giant branch (RGB), a red
horizontal branch (HB), a strong red clump, and a small number of
extended asymptotic giant branch (EAGB) stars. A mean distance modulus
of (m-M)0=24.39 is derived based on both the HB and the RGB tip
brightness. The metallicity [Fe/H] as determined from the RGB color
has a mean value of -0.91 in the central field, and -1.0 in the outer
field; and the outer field shows a weak tendency of increasing
metallicity with galactocentric radius. A metallicity dispersion is
also present in the galaxy, and it shows a clear radial variation in
the sense that a larger dispersion is seen at smaller radii. The small
population of EAGB stars indicates the presence of intermediate-aged
(several Gyr) stars in the galaxy, while the absence of the main
sequence stars with MV<1 shows that star formation ceased at least 1
Gyr ago. The distribution of the EAGB stars indicates that the younger
stars are more centrally concentrated than the majority of older
stars. A similar age gradient is also implied by the relative
distribution of the HB stars, which appear to be more populous at
larger radii. These results are considered within the context of
theoretical models for the evolution of dwarf elliptical galaxies.
(Copyright) 1997 American Astronomical Society.
Objects:
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RA (2000) DE Designation(s)
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00 33.1 +48 31 NGC 147
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2a.dat 46 78421 NGC 147 - inner field photometry
table2b.dat 46 38203 NGC 147 - outer field photometry
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Byte-by-byte Description of file: table2a.dat table2b.dat
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Bytes Format Units Label Explanations
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1- 8 F8.2 pix Xpos *X pixel coordinate
10- 16 F7.2 pix Ypos *Y pixel coordinate
18- 24 F7.3 mag Vmag V magnitude
26- 31 F6.3 mag e_Vmag Error in Vmag
33- 39 F7.3 mag Imag I magnitude
41- 46 F6.3 mag e_Imag Error in Imag
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Note on Xpos, Ypos:
The coordinate system is defined by simply stacking up the
contiguous fields of the 4 chips in each field (see HST/WFPC2
Handbook v3.0), and defining the central joining point to be
at (800,800). X and Y are in units of WF pixels.
North is up, East left.
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Origin: AAS CD-ROM series, Volume 8, 1997 Lee Brotzman [ADS] 09-Apr-1997
(End) [CDS] 04-Jul-1997