J/MNRAS/323/839 HST photometry of A2218 early-type galaxies (Smail+, 2001)
A photometric study of the ages and metallicities of
early-type galaxies in A 2218.
Smail I., Kuntschner H., Kodama T., Smith G.P., Packham C., Fruchter A.S.,
Hook R.N.
<Mon. Not. R. Astron. Soc. 323, 839 (2001)>
=2001MNRAS.323..839S 2001MNRAS.323..839S (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Galaxies, photometry
Mission_Name: HST
Keywords: galaxies: clusters: individual: A2218 -
galaxies: elliptical and lenticular, cD - galaxies: evolution -
galaxies: stellar content - infrared: galaxies
Abstract:
We present deep optical and near-infrared imaging of the rich cluster
A2218 at z=0.17. Our optical imaging comes from new multicolour Hubble
Space Telescope WFPC2 observations in the F450W (B450), F606W
(V606) and F814W (I814) passbands. These observations are
complemented by deep near-infrared, Ks-band imaging from the new
INGRID imager on the 4.2-m William Herschel Telescope. This
combination provides unique high-precision multicolour
optical-infrared photometry and morphological information for a large
sample of galaxies in the core of this rich cluster, at a look-back
time of ∼3Gyr. We analyse the (B450-I814), (V606-I814) and
(I814-Ks) colours of galaxies spanning a range of a factor of 100
in K-band luminosity in this region, and compare them with grids of
stellar population models. We find that the locus of the colours of
the stellar populations in the luminous (≳LK*) early-type galaxies,
both ellipticals and S0s, traces a sequence of varying metallicity at
a single age. At fainter luminosities (≲0.1LK*), this sequence is
extended to lower metallicities by the morphologically classified
ellipticals. However, the faintest S0s exhibit very different
behaviour, showing a wide range of colours, including a large fraction
(30 per cent) with relatively blue colours that appear to have younger
luminosity-weighted ages for their stellar populations; 2-5Gyr. We
show that the proportion of these young S0s in the cluster population
is consistent with the observed decrease in the S0 population seen in
distant clusters, when interpreted within the framework of a two-step
spectroscopic and morphological transformation of accreted spiral
field galaxies into cluster S0s.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 100 81 Galaxy catalogue
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2001)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- ID Identification number
6- 10 A5 --- Name Other identifications (1)
12- 13 I2 h RAh Right ascension (J2000)
15- 16 I2 min RAm Right ascension (J2000)
18- 22 F5.2 s RAs Right ascension (J2000)
24 A1 --- DE- Declination sign (J2000)
25- 26 I2 deg DEd Declination sign (J2000)
28- 29 I2 arcmin DEm Declination (J2000)
31- 34 F4.1 arcsec DEs Declination (J2000)
36- 40 F5.2 mag Kmag Total Ks magnitude
42- 45 F4.2 mag e_Kmag rms uncertainty on Kmag
47 A1 --- l_B-I Limit flag on B-I (2)
48- 51 F4.2 mag B-I B450-I814 colour index
53- 56 F4.2 mag e_B-I ? rms uncertainty on B-I
58- 61 F4.2 mag V-I V606-I814 colour index
63- 66 F4.2 mag e_V-I rms uncertainty on V-I
68- 71 F4.2 mag I-K I814-Ks colour index
73- 76 F4.2 mag e_I-K rms uncertainty on I-K
78- 81 F4.2 arcsec r Radius (rhl)
83- 87 A5 --- MType Morphological type (?: unclassifiable morphology)
89- 94 F6.4 --- z ? Redshift
96-100 A5 --- Note Notes (3)
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Note (1): Other identifications:
Z: Ziegler, Bower, Smail, Davies & Lee (2001, MNRAS, submitted)
ZNNNN = [ZBS2001] NNNN in Simbad
B: Butcher et al. (1983ApJS...52..183B 1983ApJS...52..183B)
BNNN = BOW ACO 2218 CCNNN in Simbad
L: Le Borgne et al., (1992A&AS...95...87L 1992A&AS...95...87L)
LNNN = LPS NNN in Simbad
K: Kristian et al., (1978ApJ...221..383K 1978ApJ...221..383K)
KN = [KSW78], ACO 2218 GN in Simbad
Note (2): When upper limits for B-I index, the error is 2σ
Note (3): Ziegler, Bower, Smail, Davies & Lee et al. (2001, MNRAS, submitted)
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History:
From electronic version of the journal
(End) Patricia Bauer [CDS] 16-Oct-2001