J/A+A/345/419 Star formation in early-type galaxies (Longhetti+ 1999)
Star formation history of early-type galaxies in low density environments.
V. Blue line-strength indices for the nuclear region
Longhetti M., Bressan A., Chiosi C., Rampazzo R.
<Astron. Astrophys. 345, 419 (1999)>
=1999A&A...345..419L 1999A&A...345..419L (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, spectra ; Models, evolutionary
Keywords: galaxies: elliptical and lenticular, cD - Galaxies: evolution -
galaxies: formation - galaxies: fundamental parameters -
galaxies: interactions - galaxies: star-burst
Abstract:
We analyze the star formation properties of a sample of 21 shell
galaxies and 30 early-type galaxies members of interacting pairs,
located in low density environments (Longhetti et al., 1998,
Cat. J/A+AS/130/251, 1998A&AS..130..267L 1998A&AS..130..267L). The study is based on new
models developed to interpret the information coming from `blue'
HδFeI, H+K(CaII) and D4000 line-strength indices proposed by
Rose (1984AJ.....89.1238R 1984AJ.....89.1238R; 1985AJ.....90.1927R 1985AJ.....90.1927R) and Hamilton
(1985ApJ...297..371H 1985ApJ...297..371H). We find that the last star forming event that
occurred in the nuclear region of shell galaxies is statistically old
(from 0.1 up to several Gyr) with respect to the corresponding one in
the sub-sample of pair galaxies (<0.1Gyr or even ongoing star
formation). If the stellar activity is somehow related to the
formation of shells, as predicted by several dynamical models of
galaxy interaction, shells have to be considered long lasting
structures. Since pair members show evidence of very recent star
formation, we suggest that either large reservoirs of gas have to be
present to maintain active star formation, if these galaxies are on
periodic orbits, or most of the pair members in the present sample are
experiencing unbound encounters.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 59 25 Blue indices for Simple Stellar Populations (SSP)
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See also:
J/A+AS/130/251 : Star Formation in Early-type galaxies. I. (Longhetti+ 1998)
J/A+A/311/361 : Evolution models of elliptical galaxies. II. (Tantalo+, 1996)
III/92 : A Library of Stellar Spectra (Jacoby+ 1984)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 5 F5.2 [yr] Log(age) Logarithm of age
6- 11 F6.2 --- D4000a Index Δ4000 at Z=0.004
12- 17 F6.2 --- H+K(CaII)a Index H+K(CaII) at Z=0.004
18- 23 F6.2 --- Hd/FeIa Index Hδ/FeI at Z=0.004
24- 29 F6.2 --- D4000b Index Δ4000 at Z=0.02
30- 35 F6.2 --- H+K(CaII)b Index H+K(CaII) at Z=0.02
36- 41 F6.2 --- Hd/FeIb Index Hδ/FeI at Z=0.02
42- 47 F6.2 --- D4000c Index Δ4000 at Z=0.05
48- 53 F6.2 --- H+K(CaII)c Index H+K(CaII) at Z=0.05
54- 59 F6.2 --- Hd/FeIc Index Hδ/FeI at Z=0.05
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Acknowledgements: Marcella Longhetti
References:
Longhetti et al., Paper I. 1998A&AS..130..251L 1998A&AS..130..251L, Cat. J/A+AS/130/251
Longhetti et al., Paper II. 1998A&AS..130..267L 1998A&AS..130..267L
Rampazzo et al., Paper III. 1999A&A...341..357R 1999A&A...341..357R
(End) Patricia Bauer [CDS] 26-Apr-1999