J/ApJ/788/72 Observed sample of z∼0.7 massive galaxies (Gallazzi+, 2014)
Charting the evolution of the ages and metallicities of massive galaxies
since z=0.7.
Gallazzi A., Bell E.F., Zibetti S., Brinchmann J., Kelson D.D.
<Astrophys. J., 788, 72 (2014)>
=2014ApJ...788...72G 2014ApJ...788...72G (SIMBAD/NED BibCode)
ADC_Keywords: Galaxy catalogs ; Redshifts ; Magnitudes ; Photometry, infrared
Keywords: galaxies: evolution - galaxies: general - galaxies: stellar content
Abstract:
Detailed studies of the stellar populations of intermediate-redshift
galaxies can shed light onto the processes responsible for the growth
of the massive galaxy population in the last 8 billion years. We here
take a step toward this goal by means of deep, multiobject rest-frame
optical spectroscopy, performed with the Inamori Magellan Areal Camera
and Spectrograph on the Magellan telescope, of a sample of ∼70 galaxies
in the Extended Chandra Deep Field South survey with redshift
0.65≤z≤0.75, apparent R>22.7 magVega, and stellar mass
>1010 M☉. We measure velocity dispersion and stellar
absorption features for individual sources. We interpret them by means
of a large Monte Carlo library of star formation histories, following
the Bayesian approach adopted for previous low redshift studies, and
derive constraints on the stellar mass, mean stellar age, and stellar
metallicity of these galaxies. We characterize for the first time the
relations between stellar age and stellar mass and between stellar
metallicity and stellar mass at z∼0.7 for the galaxy population as a
whole and for quiescent and star-forming galaxies separately. These
relations of increasing age and metallicity with galaxy mass for the
galaxy population as a whole have a similar shape as the z∼0.1
analog derived for Sloan Digital Sky Survey galaxies but are shifted
by -0.28 dex in age and by -0.13 dex in metallicity, at odds with
simple passive evolution. Considering z=0.7 quiescent galaxies alone,
we find that no additional star formation and chemical enrichment are
required for them to evolve into the present-day quiescent population.
However, other observations require the quiescent population to grow
from z=0.7 to the present day. This growth could be supplied by the
quenching of a fraction of z=0.7 M{sstarf}>1011 M☉ star-forming
galaxies with metallicities already comparable to those of quiescent
galaxies, thus leading to the observed increase of the scatter in age
without affecting the metallicity distribution. However, rapid
quenching of the entire population of massive star-forming galaxies at
z=0.7 would be inconsistent with the age- and metallicity-mass
relations for the population as a whole and with the metallicity
distribution of star-forming galaxies only, which are, on average,
0.12 dex less metal rich than their local counterparts. This indicates
chemical enrichment until the present in at least a fraction of
the z=0.7 star-forming galaxies in our sample.
Description:
The sample has been selected from the COMBO-17 catalog of the Extended
Chandra Deep Field South (E-CDFS) survey (Wolf et al. 2004A&A...421..913W 2004A&A...421..913W,
Cat. II/253; see also Section 2.4.1) to have photometric redshift (or
spectroscopic when available) in the range 0.65=<z=<0.75 and to have
stellar mass larger than 1010 M☉ (as estimated from spectral
energy distribution (SED) fitting by Borch et al. 2006A&A...453..869B 2006A&A...453..869B).
These criteria give a sample of 717 galaxies (of which 200 already had
a spectroscopic redshift from the literature at the time at which the
targets were selected). We further restrict the selection to galaxies
with apparent R-band magnitude R<22.7, which allows sampling the red
sequence down to its completeness limit of 3x1010 M☉ at this
redshift (Borch et al. 2006A&A...453..869B 2006A&A...453..869B) and the massive end of the
blue cloud. From the so-selected sample of 521 galaxies we observed a
final sample of 77 galaxies with a single IMACS mask designed.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 93 77 Summary of the Observed Sample
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See also:
II/253 : Chandra Deep Field South: multi-colour data (Wolf+, 2008)
J/ApJS/174/136 : GEMS survey data and catalog (Caldwell+, 2008)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- IMACSID Galaxy ID on IMACS mask (obsNNN)
8 A1 --- n_IMACSID [abc] Note on IMACSID (1)
10- 14 I5 --- COMBOID Galaxy ID in COMBO-17 catalog (Wolf et al.
2004A&A...421..913W 2004A&A...421..913W, Cat. II/253 ;
[WDK2001] NNNNN)
16- 38 A23 --- GEMSID Galaxy ID in GEMS catalog if available
(Caldwell et al. 2008, J/ApJS/174/136)
40- 41 I2 h RAh Hour of Right Ascension (J2000)
43- 44 I2 min RAm Minute of Right Ascension (J2000)
46- 51 F6.3 s RAs Second of Right Ascension (J2000)
53 A1 --- DE- Sign of the Declination (J2000)
54- 55 I2 deg DEd Degree of Declination (J2000)
57- 58 I2 arcmin DEm Arcminute of Declination (J2000)
60- 64 F5.2 arcsec DEs Arcsecond of Declination (J2000)
66- 72 F7.5 --- z Redshift from IMACS spectra
74- 80 F7.5 --- e_z Uncertainty in z
82- 86 F5.2 mag Rmag R-band MAGBEST Vega magnitude (2)
88 A1 --- l_F24 [<] Limit flag on F24
89- 93 F5.1 uJy F24 ?=- FIDEL Spitzer 24 µm flux (3)
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Note (1): Note as follows:
a = The spectrum is contaminated by the light from an object very close and
similar in morphology and color to the target. While the inferred stellar
population properties may be slightly affected, the line broadening and
inferred velocity dispersion may be wrong.
b = The spectrum is contaminated by the light of a very blue object close in
projection but at a different redshift which manifests itself from the
presence of emission lines at a redshift of 0.821.
c = The spectrum suffers from a bad spectrophotometric calibration because of
contamination at red wavelengths.
Note (2): From COMBO-17 catalog (Wolf et al. 2004A&A...421..913W 2004A&A...421..913W, Cat. II/253),
which has formal errors <0.05 mag.
Note (3): Nondetections are set to 3sigma limit of 24.6 µJy; fluxes of
detections are accurate at the 30% level typically.
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History:
From electronic version of the journal
(End) Prepared by Tiphaine Pouvreau [CDS] 07-Jul-2017