Photometric redshifts determinations for galaxies by means of multicolor photometry

2007 ◽  
Author(s):  
Nedelia A. Popescu
Keyword(s):  
Photometric Redshifts ◽  
Multicolor Photometry

scholarly journals Liquid-Mirror Telescope Surveys

1998 ◽  
Vol 11 (1) ◽  
pp. 464-467
Author(s):  
P. Hickson
Keyword(s):  
Integration Time ◽  
Spectral Energy ◽  
Energy Distributions ◽  
Ccd Cameras ◽  
Photometric Redshifts ◽  
Rotating Liquid ◽  
Liquid Mirrors ◽  
Under Construction ◽  
Optical Telescopes ◽  
Mirror Telescope

Abstract Recent advances in the technology of rotating liquid-mirrors now make feasible the construction of large optical telescopes for dedicated survey programs. Two three-metre-class astronomical telescopes have been built and asix-metre telescope is under construction. These instruments observe in zenith-pointing mode, using drift-scanning CCD cameras to record continuous imaging of a strip of sky typically 20 arcmin wide. This enables them to observe of order 100 square degrees of sky with an integration time of a few minutes per night. Data can be co-added from night to night in order to increase the depth of the survey. Liquid-mirror telescopes are particularly wellsuited to surveys using broad or intermediate bandwidth filters to obtain photometric redshifts and spectral energy distributions for faint galaxies and quasars.

scholarly journals Blending and obscuration in weak lensing magnification

2021 ◽  
Author(s):  
E Gaztanaga ◽  
S J Schmidt ◽  
M D Schneider ◽  
J A Tyson
Keyword(s):  
Systematic Errors ◽  
Weak Lensing ◽  
Wide Field ◽  
Photometric Redshifts ◽  
Field Surveys ◽  
Systematic Effects ◽  
The Impact ◽  
Close Pairs ◽  
Mass Profiles

Abstract We test the impact of some systematic errors in weak lensing magnification measurements with the COSMOS 30-band photo-z Survey flux limited to Iauto < 25.0 using correlations of both source galaxy counts and magnitudes. Systematic obscuration effects are measured by comparing counts and magnification correlations. We use the ACS-HST catalogs to identify potential blending objects (close pairs) and perform the magnification analyses with and without blended objects. We find that blending effects start to be important (∼ 0.04 mag obscuration) at angular scales smaller than 0.1 arcmin. Extinction and other systematic obscuration effects can be as large as 0.10 mag (U-band) but are typically smaller than 0.02 mag depending on the band. After applying these corrections, we measure a 3.9σ magnification signal that is consistent for both counts and magnitudes. The corresponding projected mass profiles of galaxies at redshift z ≃ 0.6 (MI ≃ −21) is Σ = 25 ± 6M⊙h3/pc2 at 0.1 Mpc/h, consistent with NFW type profile with M200 ≃ 2 × 1012M⊙h/pc2. Tangential shear and flux-size magnification over the same lenses show similar mass profiles. We conclude that magnification from counts and fluxes using photometric redshifts has the potential to provide complementary weak lensing information in future wide field surveys once we carefully take into account systematic effects, such as obscuration and blending.

scholarly journals Photometric redshifts with surface brightness priors

2008 ◽  
Vol 387 (3) ◽  
pp. 1215-1226 ◽  
Author(s):  
Hans F. Stabenau ◽  
Andrew Connolly ◽  
Bhuvnesh Jain
Keyword(s):  
Surface Brightness ◽  
Photometric Redshifts

scholarly journals Hierarchical Matching and Regression with Application to Photometric Redshift Estimation

2016 ◽  
Vol 12 (S325) ◽  
pp. 145-155
Author(s):  
Fionn Murtagh
Keyword(s):  
Information Structure ◽  
Data Analytics ◽  
A Priori ◽  
Sloan Digital Sky Survey ◽  
Photometric Redshifts ◽  
Merging Galaxies ◽  
Photometric Redshift ◽  
Sky Survey ◽  
Wide Range ◽  
Regression Problems

AbstractThis work emphasizes that heterogeneity, diversity, discontinuity, and discreteness in data is to be exploited in classification and regression problems. A global a priori model may not be desirable. For data analytics in cosmology, this is motivated by the variety of cosmological objects such as elliptical, spiral, active, and merging galaxies at a wide range of redshifts. Our aim is matching and similarity-based analytics that takes account of discrete relationships in the data. The information structure of the data is represented by a hierarchy or tree where the branch structure, rather than just the proximity, is important. The representation is related to p-adic number theory. The clustering or binning of the data values, related to the precision of the measurements, has a central role in this methodology. If used for regression, our approach is a method of cluster-wise regression, generalizing nearest neighbour regression. Both to exemplify this analytics approach, and to demonstrate computational benefits, we address the well-known photometric redshift or ‘photo-z’ problem, seeking to match Sloan Digital Sky Survey (SDSS) spectroscopic and photometric redshifts.

scholarly journals The ALHAMBRA Survey: Bayesian photometric redshifts with 23 bands for 3 deg2

2014 ◽  
Vol 441 (4) ◽  
pp. 2891-2922 ◽  
Author(s):  
A. Molino ◽  
N. Benítez ◽  
M. Moles ◽  
A. Fernández-Soto ◽  
D. Cristóbal-Hornillos ◽  
...  
Keyword(s):  
Photometric Redshifts

scholarly journals Calibrating photometric redshifts with intensity mapping observations

2017 ◽  
Vol 96 (4) ◽  
Author(s):  
David Alonso ◽  
Pedro G. Ferreira ◽  
Matt J. Jarvis ◽  
Kavilan Moodley
Keyword(s):  
Photometric Redshifts ◽  
Intensity Mapping

scholarly journals Photometric Redshifts in the IRAC Shallow Survey

2006 ◽  
Vol 651 (2) ◽  
pp. 791-803 ◽  
Author(s):  
M. Brodwin ◽  
M. J. I. Brown ◽  
M. L. N. Ashby ◽  
C. Bian ◽  
K. Brand ◽  
...  
Keyword(s):  
Photometric Redshifts

Measuring the Probabilistic Photometric Redshifts of X-ray Quasars Based on the Quantile Regression of Ensembles of Decision Trees

2018 ◽  
Vol 44 (12) ◽  
pp. 735-753 ◽  
Author(s):  
A. V. Meshcheryakov ◽  
V. V. Glazkova ◽  
S. V. Gerasimov ◽  
I. V. Mashechkin
Keyword(s):  
Quantile Regression ◽  
Decision Trees ◽  
Photometric Redshifts ◽  
X Ray
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