The K20 survey VII. The spectroscopic catalogue: Spectral properties and evolution of the galaxy population

被引:206
作者
Mignoli, M
Cimatti, A
Zamorani, G
Pozzetti, L
Daddi, E
Renzini, A
Broadhurst, T
Cristiani, S
D'Odorico, S
Fontana, A
Giallongo, E
Gilmozzi, R
Menci, N
Saracco, P
机构
[1] Osservatorio Astron Bologna, Ist Nazl Astrofis, I-40127 Bologna, Italy
[2] Osserv Astrofis Arcetri, Ist Nazl Astrofis, I-50125 Florence, Italy
[3] European So Observ, D-85748 Garching, Germany
[4] Hebrew Univ Jerusalem, Racah Inst Phys, IL-91904 Jerusalem, Israel
[5] Osserv Astron Trieste, Ist Nazl Astrofis, I-34131 Trieste, Italy
[6] Osserv Astron Roma, Ist Nazl Astrofis, Monte Porzio Catone, Italy
[7] Osserv Astron Brera, Ist Nazl Astrofis, Merate, Italy
关键词
galaxies : evolution; galaxies : distances and redshifts;
D O I
10.1051/0004-6361:20042434
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
The K20 survey is a near infrared-selected, deep (K-s < 20) redshift survey targeting galaxies in two independent regions of the sky, the Chandra Deep Field South and the field around the quasar 0055-2659, for a total area of 52 arcmin(2). The total K-s-selected sample includes 545 objects. Low-resolution (R approximate to 300- 600) optical spectra for 525 of them have been obtained with the FORS1/FORS2 spectrographs at the ESO/VLT, providing 501 spectroscopic identifications ( including 12 type-1 AGN and 45 stars); consequently, we were able to measure redshifts and identify stars in 96% of the observed objects, whereas the spectroscopic completeness with respect to the total photometrically selected sample is 92% (501/545). The K20 survey is therefore the most complete spectroscopic survey of a near infrared-selected sample to date. The K20 survey contains 444 spectroscopically identified galaxies, covering a redshift range of 0.05 < z < 2.73, with a mean redshift < z > = 0.75; excluding the 32 "low-quality" redshifts does not significantly change these values. This paper describes the final K20 spectroscopic catalogue, along with the technique used to determine redshifts, measure the spectral features and characterize the spectra. The classification of the galaxy spectra has been performed according to a simple parametric recipe that uses the equivalent widths of the two main emission lines ([OII]lambda 3727 and H alpha+[NII]) and two continuum indices ( the 4000 angstrom break index, D4000, and a near-UV color index, C(28-39)). We defined three main spectroscopic classes: red early-type galaxies, blue emission-line galaxies and the intermediate galaxies, which show emission lines but a red continuum. More than 95% of the examined galaxies is included in one of these spectral types and a composite spectrum is built for each of the three galaxy classes. The full spectroscopic catalogue, the reduced individual spectra and the composite spectra are released to the community through the K20 web page (http://www.arcetri.astro.it/similar to k20/). The blue emission-line and the early-type galaxies have been divided in redshift bins, and the corresponding composite spectra have been built, in order to investigate the evolution of the spectral properties of the K20 galaxies with redshift. The early-type average spectra are remarkable in their similarity, showing only subtle but systematic differences in the D4000 index, which are consistent with the ageing of the stellar population. Conversely, the star-forming galaxies present a significant "blueing" of the optical/near-UV continuum with redshift, although the [ OII] equivalent width remains constant (similar to 33 angstrom) in the same redshift intervals. We reproduce the observed properties with simple, dust-free population synthesis models, suggesting that the high-redshift galaxies are younger and more active than those detected at lower redshift, whilst the equivalent width of the emission lines apparently require a lower metallicity for the low-redshift objects. This may be consistent with the metallicity-luminosity relationship locally observed for star-forming galaxies.
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页码:883 / 897
页数:15
相关论文
共 64 条
[1]   The Gemini Deep Deep Survey. I. Introduction to the survey, catalogs, and composite spectra [J].
Abraham, RG ;
Glazebrook, K ;
McCarthy, PJ ;
Crampton, D ;
Murowinski, R ;
Jorgensen, I ;
Roth, K ;
Hook, IM ;
Savaglio, S ;
Chen, HW ;
Marzke, RO ;
Carlberg, RG .
ASTRONOMICAL JOURNAL, 2004, 127 (05) :2455-2483
[2]   The bimodal galaxy color distribution: Dependence on luminosity and environment [J].
Balogh, ML ;
Baldry, IK ;
Nichol, R ;
Miller, C ;
Bower, R ;
Glazebrook, K .
ASTROPHYSICAL JOURNAL, 2004, 615 (02) :L101-L104
[3]   Nearly 5000 distant early-type galaxies in combo-17:: A red sequence and its evolution since z ∼ 1 [J].
Bell, EF ;
Wolf, C ;
Meisenheimer, K ;
Rix, HW ;
Borch, A ;
Dye, S ;
Kleinheinrich, M ;
Wisotzki, L ;
McIntosh, DH .
ASTROPHYSICAL JOURNAL, 2004, 608 (02) :752-767
[4]   GALAXY SIZE EVOLUTION AT HIGH REDSHIFT AND SURFACE BRIGHTNESS SELECTION EFFECTS: CONSTRAINTS FROM THE HUBBLE ULTRA DEEP FIELD [J].
Bouwens, R. J. ;
Illingworth, G. D. ;
Blakeslee, J. P. ;
Broadhurst, T. J. ;
Franx, M. .
ASTROPHYSICAL JOURNAL, 2004, 611 (01) :L1-L4
[5]   Extremely red objects: An X-ray dichotomy [J].
Brusa, M ;
Comastri, A ;
Daddi, E ;
Cimatti, A ;
Mignoli, M ;
Pozzetti, L .
ASTROPHYSICAL JOURNAL, 2002, 581 (02) :L89-L92
[6]   Stellar population synthesis at the resolution of 2003 [J].
Bruzual, G ;
Charlot, S .
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 2003, 344 (04) :1000-1028
[7]   SPECTRAL EVOLUTION OF GALAXIES .1. EARLY-TYPE SYSTEMS [J].
BRUZUAL, G .
ASTROPHYSICAL JOURNAL, 1983, 273 (01) :105-127
[8]  
CAIRA G, 2004, THESIS U BOLOGNA
[9]  
CASSATA P, 2004, MNRAS, V357, P903
[10]   Star formation, metallicity and dust properties derived from the Stromlo-APM galaxy survey spectra [J].
Charlot, S ;
Kauffmann, G ;
Longhetti, M ;
Tresse, L ;
White, SDM ;
Maddox, SJ ;
Fall, SM .
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 2002, 330 (04) :876-888