The Zurich Extragalactic Bayesian Redshift Analyzer and its first application: COSMOS

Feldmann, Robert; Carollo, C. M.; Porciani, Cristiano; Lilly, S. J.; Capak, P.; Taniguchi, Yuki; Fèvre, O. Le; Renzini, A.; Scoville, N. Z.; Ajiki, Masaru; Aussel, H.; Contini, T.; McCracken, H. J.; Mobasher, Bahram; Murayama, Takashi; Sanders, D. B.; Sasaki, S.; Scarlata, Claudia; Scodeggio, M.; Shioya, Yasuhiro; Silverman, John D.; Takahashi, Mari; Thompson, D. J.; Zamorani, G.

doi:10.1111/j.1365-2966.2006.10930.x

Cited by 254 publications

(224 citation statements)

References 24 publications

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“…We found that, usually, 3-4 iterations are necessary. In contrast with the method described in Feldmann et al (2006) (in which photometric redshifts can also be used), we only use objects with spectroscopic redshifts to derive the offsets. However, we show later in this section that the spectroscopic sample is sufficient to derive accurate systematic offsets even if it is much smaller than the whole galaxy photometric sample.…”

Section: Correction Of Systematic Offsetsmentioning

confidence: 99%

Photometric redshifts for the CFHTLS T0004 deep and wide fields

Coupon¹,

Ilbert

Kilbinger³

et al. 2009

A&A

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Aims. We compute photometric redshifts in the fourth public release of the Canada-France-Hawaii Telescope Legacy Survey. This unique multi-colour catalogue comprises u * , g , r , i , z photometry in four deep fields of 1 deg 2 each and 35 deg 2 distributed over three wide fields. Methods. We used a template-fitting method to compute photometric redshifts calibrated with a large catalogue of 16 983 high-quality spectroscopic redshifts from the VVDS-F02, VVDS-F22, DEEP2, and the zCOSMOS surveys. The method includes correction of systematic offsets, template adaptation, and the use of priors. We also separated stars from galaxies using both size and colour information.Results. Comparing with galaxy spectroscopic redshifts, we find a photometric redshift dispersion, σ Δz/(1+zs) , of 0.028-0.30 and an outlier rate, |Δz| ≥ 0.15 × (1 + z s ), of 3-4% in the deep field at i AB < 24. In the wide fields, we find a dispersion of 0.037-0.039 and an outlier rate of 3-4% at i AB < 22.5. Beyond i AB = 22.5 in the wide fields the number of outliers rises from 5% to 10% at i AB < 23 and i AB < 24, respectively. For the wide sample the systematic redshift bias stays below 1% to i AB < 22.5, whereas we find no significant bias in the deep fields. We investigated the effect of tile-to-tile photometric variations and demonstrated that the accuracy of our photometric redshifts is reduced by at most 21%. Application of our star-galaxy classifier reduced the contamination by stars in our catalogues from 60% to 8% at i AB < 22.5 in our field with the highest stellar density while keeping a complete galaxy sample. Our CFHTLS T0004 photometric redshifts are distributed to the community. Our release includes 592 891 (i AB < 22.5) and 244 701 (i AB < 24) reliable galaxy photometric redshifts in the wide and deep fields, respectively.

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Section: Correction Of Systematic Offsetsmentioning

confidence: 99%

Photometric redshifts for the CFHTLS T0004 deep and wide fields

Coupon¹,

Ilbert

Kilbinger³

et al. 2009

A&A

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190

303

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“…Additional details about the spectroscopic quality flags and their probability of being robust are given in Lilly et al (2009, see their Table 1). In addition to the confidence classes described in Lilly et al (2007), a decimal place (from 5 to 1, see Table 3 in Lilly et al 2009) in the class is added to indicate the level of consistency between the spectroscopic and photometric redshifts obtained by the Zurich Extragalactic Bayesian Redshift Analyzer (ZEBRA; Feldmann et al 2006), using the optical to infrared SED.…”

Section: Cosmos and The Bright 10k Zcosmos Spectroscopic Samplementioning

confidence: 99%

zCOSMOS – 10k-bright spectroscopic sample

Pozzetti

Bolzonella

Zucca

et al. 2010

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We present the galaxy stellar mass function (GSMF) to redshift z 1, based on the analysis of about 8500 galaxies with I < 22.5 (AB mag) over 1.4 deg 2 , which are part of the zCOSMOS-bright 10k spectroscopic sample. We investigate the total GSMF, as well as the contributions of early-and late-type galaxies (ETGs and LTGs, respectively), defined by different criteria (broad-band spectral energy distribution, morphology, spectral properties, or star formation activities). We unveil a galaxy bimodality in the global GSMF, whose shape is more accurately represented by 2 Schechter functions, one linked to the ETG and the other to the LTG populations. For the global population, we confirm a mass-dependent evolution ("mass-assembly downsizing"), i.e., galaxy number density increases with cosmic time by a factor of two between z = 1 and z = 0 for intermediate-to-low mass (log(M/M ) ∼ 10.5) galaxies but less than 15% for log(M/M ) > 11. We find that the GSMF evolution at intermediateto-low values of M (log(M/M ) < 10.6) is mostly explained by the growth in stellar mass driven by smoothly decreasing star formation activities, despite the redder colours predicted in particular at low redshift. The low residual evolution is consistent, on average, with ∼0.16 merger per galaxy per Gyr (of which fewer than 0.1 are major), with a hint of a decrease with cosmic time but not a clear dependence on the mass. From the analysis of different galaxy types, we find that ETGs, regardless of the classification method, increase in number density with cosmic time more rapidly with decreasing M, i.e., follow a top-down building history, with a median "building redshift" increasing with mass (z > 1 for log(M/M ) > 11), in contrast to hierarchical model predictions. For LTGs, we find that the number density of blue or spiral galaxies with log(M/M ) > 10 remains almost constant with cosmic time from z ∼ 1. Instead, the most extreme population of star-forming galaxies (with high specific star formation), at intermediate/high-mass, rapidly decreases in number density with cosmic time. Our data can be interpreted as a combination of different effects. Firstly, we suggest a transformation, driven mainly by SFH, from blue, active, spiral galaxies of intermediate mass to blue quiescent and subsequently (1−2 Gyr after) red, passive types of low specific star formation. We find an indication that the complete morphological transformation, probably driven by dynamical processes, into red spheroidal galaxies, occurred on longer timescales or followed after 1−2 Gyr. A continuous replacement of blue galaxies is expected to be accomplished by low-mass active spirals increasing their stellar mass. We estimate the growth rate in number and mass density of the red galaxies at different redshifts and masses. The corresponding fraction of blue galaxies that, at any given time, is transforming into red galaxies per Gyr, due to the quenching of their SFR, is on average ∼25% for log(M/M ) < 11. We conclude that the build-up of galaxies and in particular of...

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“…Rest frame absolute magnitudes have been computed from the best fitting template normalized to each galaxy photometry and redshift, using the code ZEBRA (Feldmann et al 2006). The template set is composed by six observed galaxy spectra (four from Coleman et al 1980 and two from Kinney et al 1996).…”

Section: Galaxy Propertiesmentioning

confidence: 99%

The zCOSMOS 10k-sample: the role of galaxy stellar mass in the colour-density relation up toz ~ 1

Cucciati

Iovino

Kovač

et al. 2010

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Aims. With the first ∼10 000 spectra of the flux limited zCOSMOS sample (I AB ≤ 22.5) we want to study the evolution of environmental effects on galaxy properties since z ∼ 1.0, and to disentangle the dependence among galaxy colour, stellar mass and local density. Methods. We use our previously derived 3D local density contrast δ, computed with the 5th nearest neighbour approach, to study the evolution with z of the environmental effects on galaxy U-B colour, D4000 Å break and [OII]λ3727 equivalent width (EW [OII]). We also analyze the implications due to the use of different galaxy selections, using luminosity or stellar mass, and we disentangle the relations among colour, stellar mass and δ studying the colour-density relation in narrow mass bins. Results. We confirm that within a luminosity-limited sample (M B ≤ −20.5 − z) the fraction of red (U − B ≥ 1) galaxies depends on δ at least up to z ∼ 1, with red galaxies residing mainly in high densities. This trend becomes weaker for increasing redshifts, and it is mirrored by the behaviour of the fraction of galaxies with D4000 Å break ≥1.4. We also find that up to z ∼ 1 the fraction of galaxies with log(EW[OII]) ≥ 1.15 is higher for lower δ, and also this dependence weakens for increasing z. Given the triple dependence among galaxy colours, stellar mass and δ, the colour-δ relation that we find in the luminosity-selected sample can be due to the broad range of stellar masses embedded in the sample. Thus, we study the colour-δ relation in narrow mass bins within mass complete subsamples, defining red galaxies with a colour threshold roughly parallel to the red sequence in the colour-mass plane. We find that once mass is fixed the colour-δ relation is globally flat up to z ∼ 1 for galaxies with log(M/M ) 10.7. This means that for these masses any colour-δ relation found within a luminosity-selected sample is the result of the combined colour-mass and mass-δ relations. On the contrary, even at fixed mass we observe that within 0.1 ≤ z ≤ 0.5 the fraction of red galaxies with log(M/M ) 10.7 depends on δ. For these mass and redshift ranges, environment affects directly also galaxy colours. Conclusions. We suggest a scenario in which the colour depends primarily on stellar mass, but for an intermediate mass regime (10.2 log(M/M ) 10.7) the local density modulates this dependence. These relatively low mass galaxies formed more recently, in an epoch when more evolved structures were already in place, and their longer SFH allowed environment-driven physical processes to operate during longer periods of time.

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The Zurich Extragalactic Bayesian Redshift Analyzer and its first application: COSMOS

Cited by 254 publications

References 24 publications

Photometric redshifts for the CFHTLS T0004 deep and wide fields

Photometric redshifts for the CFHTLS T0004 deep and wide fields

zCOSMOS – 10k-bright spectroscopic sample

The zCOSMOS 10k-sample: the role of galaxy stellar mass in the colour-density relation up toz ~ 1

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