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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 (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, 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). 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) 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:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 93 77 Summary of the Observed Sample
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
Bytes Format Units Label Explanations
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, 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 muJy F24 ? FIDEL Spitzer 24 µm flux (3)
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, 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.
History: From electronic version of the journal
(End) Prepared by Tiphaine Pouvreau [CDS] 07-Jul-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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