J/MNRAS/469/1186 Emission-line strengths for 129 galaxies (Speagle+, 2017)
Deriving photometric redshifts using fuzzy archetypes and self-organizing maps.
I. Methodology.
Speagle J.S., Eisenstein D.J.
<Mon. Not. R. Astron. Soc., 469, 1186-1204 (2017)>
=2017MNRAS.469.1186S 2017MNRAS.469.1186S (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Photometry, ultraviolet ; Equivalent widths
Keywords: methods: statistical - techniques: photometric -
galaxies: distances and redshifts
Abstract:
We propose a method to substantially increase the flexibility and
power of template fitting-based photometric redshifts by transforming
a large number of galaxy spectral templates into a corresponding
collection of 'fuzzy archetypes' using a suitable set of perturbative
priors designed to account for empirical variation in dust attenuation
and emission-line strengths. To bypass widely separated degeneracies
in parameter space (e.g. the redshift-reddening degeneracy), we train
self-organizing maps (SOMs) on large 'model catalogues' generated from
Monte Carlo sampling of our fuzzy archetypes to cluster the predicted
observables in a topologically smooth fashion. Subsequent sampling
over the SOM then allows full reconstruction of the relevant
probability distribution functions (PDFs). This combined approach
enables the multimodal exploration of known variation among galaxy
spectral energy distributions with minimal modelling assumptions. We
demonstrate the power of this approach to recover full redshift PDFs
using discrete Markov chain Monte Carlo sampling methods combined with
SOMs constructed from Large Synoptic Survey Telescope ugrizY and
Euclid YJH mock photometry.
Description:
For each galaxy, we measure the corresponding EWs of {Hα+N[II],
Hβ, Hγ, O[II], O[III]5008, O[III]4960} assuming
corresponding effective central wavelengths of
λline={6564.6, 4862.7, 4341.7, 3727.0, 5008.2, 4960.3}. We
model the continuum using a linear fit over the regions contained
within ±100-155 per cent of the corresponding
Δv=±{2000, 1500, 1500, 1500, 1500, 1250}km/s spread. After
combining both O[III] lines into a single template, we are left with
five emission-line templates per archetype. Our derived EWs for each
galaxy are listed in Table A1.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 72 129 Emission-line strengths for the 129
Brown et al. (2014, Cat. J/ApJS/212/18) templates
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See also:
J/ApJS/212/18 : An atlas of UV-to-MIR galaxy SEDs (Brown+, 2014)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- Name Name
17- 19 I3 --- ID [1/129] ID number, ordered by FUV flux in
the GALEX FUV filter after normalizing each
template to 1.6um
21- 25 F5.3 [-] log10(FUV) FUV flux in the GALEX FUV filter
27- 33 F7.3 --- Halpha+NII Hα+NII emission-line strength (1)
35- 41 F7.3 --- Hbeta Hβ emission-line strength (1)
43- 48 F6.3 --- Hgamma Hγ emission-line strength (1)
50- 56 F7.3 --- OII O[II] emission-line strength (1)
58- 64 F7.3 --- OIII4 O[III]4960 emission-line strength (1)
66- 72 F7.3 --- OIII5 O[III]5008 emission-line strength (1)
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Note (1): Emission-line strengths are measured using EWs in Å.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 30-Mar-2020