Bayesian Photometric Redshift Estimation

Benítez, N.

doi:10.1086/308947

Cited by 1,206 publications

(1,475 citation statements)

References 40 publications

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“…The photometric redshifts obtained for this survey have been calculated with BPZ2.0 (Benitez in prep), an improved version of BPZ (Benítez 2000) capable of also providing stellar masses. The catalogues, including a full range of measured properties of the galaxies, are publicly available 3 (see Molino et al 2014 for details).…”

Section: The Alhambra Surveymentioning

confidence: 99%

Galaxy clusters and groups in the ALHAMBRA survey

Ascaso

Benı́tez

Fernández-Soto

et al. 2015

Mon. Not. R. Astron. Soc.

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We present a catalogue of 348 galaxy clusters and groups with 0.2 < z < 1.2 selected in the 2.78 deg 2 ALHAMBRA Survey. The high precision of our photometric redshifts, close to 1%, and the wide spread of the seven ALHAMBRA pointings ensure that this catalogue has better mass sensitivity and is less affected by cosmic variance than comparable samples.The detection has been carried out with the Bayesian Cluster Finder (BCF), whose performance has been checked in ALHAMBRA-like light-cone mock catalogues. Great care has been taken to ensure that the observable properties of the mocks photometry accurately correspond to those of real catalogues. From our simulations, we expect to detect galaxy clusters and groups with both 70% completeness and purity down to dark matter halo masses of M h ∼ 3 × 10 13 M ⊙ for z < 0.85. Cluster redshifts are expected to be recovered with ∼ 0.6% precision for z < 1. We also expect to measure cluster masses with σ M h |M * CL ∼ 0.25 − 0.35 dex precision down to ∼ 3 × 10 13 M ⊙ , masses which are 50% smaller than those reached by similar work.We have compared these detections with previous optical, spectroscopic and Xrays work, finding an excellent agreement with the rates reported from the simulations. We have also explored the overall properties of these detections such as the presence of a colour-magnitude relation, the evolution of the photometric blue fraction and the clustering of these sources in the different ALHAMBRA fields. Despite the small numbers, we observe tentative evidence that, for a fixed stellar mass, the environment is playing a crucial role at lower redshifts (z<0.5).

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Section: The Alhambra Surveymentioning

confidence: 99%

Galaxy clusters and groups in the ALHAMBRA survey

Ascaso

Benı́tez

Fernández-Soto

et al. 2015

Mon. Not. R. Astron. Soc.

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“…Our photometric redshift estimates are made with two different techniques: Le Phare (LPZ) 15 and Bayesian Photometric Redshifts (BPZ) 16 . LPZ photometric redshifts are based on a template fitting procedure with a maximum likelihood (χ 2 ) estimate.…”

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confidence: 99%

A magnified young galaxy from about 500 million years after the Big Bang

Zheng

Postman

Zitrin

et al. 2012

Nature

309

342

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The early Universe at redshift z∼6-11 marks the reionization of the intergalactic medium, following the formation of the first generation of stars. However, those young galaxies at a cosmic age of < ∼ 500 million years (Myr, at z > ∼ 10) remain largely unexplored as they are at or beyond the sensitivity limits of current large telescopes. Gravitational lensing by galaxy clusters enables the detection of high-redshift galaxies that are fainter than what otherwise could be found in the deepest images of the sky. We report the discovery of an object found in the multi-band observations of the cluster MACS1149+22 that has a high probability of being a gravitationally magnified object from the early universe. The object is firmly detected (12σ) in the two reddest bands of HST/WFC3, and not detected below 1.2 µm, matching the characteristics of z∼9 objects. We derive a robust photometric redshift of z = 9.6 ± 0.2, corresponding to a cosmic age of 490 ± 15 Myr (i.e., 3.6% of the age of the Universe).The large number of bands used to derive the redshift estimate make it one of the most accurate estimates ever obtained for such a distant object. The significant magnification by cluster lensing (a factor of ∼15) allows us to analyze the object's ultra-violet and optical luminosity in its rest-2 frame, thus enabling us to constrain on its stellar mass, star-formation rate and age. If the galaxy is indeed at such a large redshift, then its age is less than 200 Myr (at the 95% confidence level), implying a formation redshift of z f < ∼ 14. The object is the first z>9 candidate that is bright enough for detailed spectroscopic studies with JWST, demonstrating the unique potential of galaxy cluster fields for finding highly magnified, intrinsically faint galaxies at the highest redshifts.Observational cosmology has established that the age of the Universe is 13.7 billion years, and the reionization of the vast intergalactic medium (IGM) started around redshift z ∼ 11, 1 as the result of radiation from the first generation of stars. The task of probing the most distant Universe is progressively challenging: While more than 10 5 quasars have been found, only one is at z > 7; 2 while thousands of gamma-ray burst events have been recorded, only one 3 is confirmed at z=8.3; and while thousands of galaxy candidates have been found at z ∼ 6, only one has been reported at z ∼ 10, 4 which is based on a single-band detection. Galaxies at z ∼ 10 are expected to be at a magnitude of ∼ 29 (in the AB system, used hereafter) 4, 5 , near the detection limits of the deepest fields observed by Hubble Space Telescope (HST), and beyond the spectroscopic capability of even the next generation of large telescopes.In this Letter we report the discovery of a gravitationally lensed source whose most likely redshift is z ∼ 9.6. The source, hereafter called MACS1149-JD1, is selected from a near-infrared detection image at significance of 22σ. MACS1149-JD1 has a unique flux distribution characterized by a) no detection at Galaxy clusters are the largest r...

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“…This will be done using the Bayesian approach implemented in BPZ (Benítez 2000), updated in BPZ2.0. It has been shown that the analysis of the residuals of the photo-z procedure in the different bands can help to detect offsets in the original photometry, that applied to all the objects can improve the final photometric redshifts (Molino et al 2014).…”

Section: Challenge 6 Photometric Redshiftmentioning

confidence: 99%

Statistical Challenges in the Photometric Calibration for 21st Century Cosmology: The J-PAS case

Varela¹,

Cristóbal-Hornillos²,

Cenarro³

et al. 2014

Proc. IAU

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Abstract. The success of many cosmological surveys in the near future is highly grounded on the quality of their photometry. The Javalambre-PAU Astrophysical Survey (J-PAS) will image more than 8500 deg 2 of the Northern Sky Hemisphere in 54 narrow + 2 medium/broad optical bands plus Sloan u, g and r bands. The main goal of J-PAS is to provide the best constrains on the cosmological parameters before the arrival of projects like Euclid or LSST. To achieve this goal the uncertainty in photo-z cannot be larger than 0.3% for several millions of galaxies and this is highly dependent on the photometric accuracy.The photometric calibration of J-PAS will imply the intensive use of huge amounts of data and the use of statistical tools is unavoidable. Here, we present some of the key steps in the photometric calibration of J-PAS that will demand a suitable statistical approach.

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Bayesian Photometric Redshift Estimation

Cited by 1,206 publications

References 40 publications

Galaxy clusters and groups in the ALHAMBRA survey

Galaxy clusters and groups in the ALHAMBRA survey

A magnified young galaxy from about 500 million years after the Big Bang

Statistical Challenges in the Photometric Calibration for 21st Century Cosmology: The J-PAS case

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