J/MNRAS/449/4277 GAMA blended spectra catalogue (Holwerda+, 2015)
Galaxy And Mass Assembly (GAMA) blended spectra catalogue:
strong galaxy-galaxy lens and occulting galaxy pair candidates.
Holwerda B.W., Baldry I.K., Alpaslan M., Bauer A., Bland-Hawthorn J.,
Brough S., Brown M.J.I., Cluver M.E., Conselice C., Driver S.P.,
Hopkins A.M., Jones D.H., Lopez-Sanchez A.R., Loveday J., Meyer M.J.,
Moffett A.
<Mon. Not. R. Astron. Soc., 449, 4277-4287 (2015)>
=2015MNRAS.449.4277H 2015MNRAS.449.4277H (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, spectra ; Redshifts ; Gravitational lensing
Keywords: gravitational lensing: strong - catalogues - dust, extinction -
galaxies: distances and redshifts - galaxies: statistics
Abstract:
We present the catalogue of blended galaxy spectra from the Galaxy And
Mass Assembly (GAMA) survey. These are cases where light from two
galaxies are significantly detected in a single GAMA fibre. Galaxy
pairs identified from their blended spectrum fall into two principal
classes: they are either strong lenses, a passive galaxy lensing an
emission-line galaxy; or occulting galaxies, serendipitous overlaps of
two galaxies, of any type. Blended spectra can thus be used to
reliably identify strong lenses for follow-up observations
(high-resolution imaging) and occulting pairs, especially those that
are a late-type partly obscuring an early-type galaxy which are of
interest for the study of dust content of spiral and irregular
galaxies. The GAMA survey setup and its AUTOZ automated redshift
determination were used to identify candidate blended galaxy spectra
from the cross-correlation peaks. We identify 280 blended spectra with
a minimum velocity separation of 600km/s, of which 104 are lens pair
candidates, 71 emission-line-passive pairs, 78 are pairs of
emission-line galaxies and 27 are pairs of galaxies with passive
spectra. We have visually inspected the candidates in the Sloan
Digital Sky Survey (SDSS) and Kilo Degree Survey (KiDS) images. Many
blended objects are ellipticals with blue fuzz (Ef in our
classification). These latter 'Ef' classifications are candidates for
possible strong lenses, massive ellipticals with an emission-line
galaxy in one or more lensed images. The GAMA lens and occulting
galaxy candidate samples are similar in size to those identified in
the entire SDSS. This blended spectrum sample stands as a testament of
the power of this highly complete, second-largest spectroscopic survey
in existence and offers the possibility to expand e.g. strong
gravitational lens surveys.
Description:
Galaxy redshifts were initially determined by a supervised fit (Liske
2015, MNRAS, submitted) but a recent upgrade to the GAMA survey
pipeline includes a fully automated template-based redshift
determination (AUTOZ; Baldry et al. 2014MNRAS.441.2440B 2014MNRAS.441.2440B). In certain
cases, the fits for different templates resulted in two high fidelity,
but different redshifts; these are the candidate blended objects of
interest to us here.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 74 280 The complete catalogue of blended spectra in
the GAMA survey
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See also:
J/MNRAS/413/971 : Galaxy And Mass Assembly (GAMA) DR1 (Driver+, 2011)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Field Field designation
5- 11 I7 --- GAMA GAMA identification number
13- 21 F9.5 deg RAdeg Right ascension (J2000)
23- 31 F9.5 deg DEdeg Declination (J2000)
33- 37 F5.3 --- z Redshift of the first peak of normalized
cross-correlation function
39- 40 I2 --- T1 Template number for the first peak of
normalized cross-correlation function
42- 45 F4.1 --- rx Height and position of the first peak of
normalized cross-correlation function (1)
47- 51 F5.3 --- z2 Redshift of the second peak of normalized
cross-correlation function
53- 54 I2 --- T2 Template number for the second peak of
normalized cross-correlation function
56- 59 F4.1 --- rx2 Height and position of the second peak of
normalized cross-correlation function (1)
61- 67 A7 -- SpType Spectral classification (2)
69- 74 A6 --- VType Visual classification
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Note (1): The AUTOZ code obtains cross-correlation redshifts against stellar and
galaxy templates with varying strength of emission and absorption line
features. The height and position of the first four peaks of normalized
cross-correlation functions are obtained. These are called rx, rx2, rx3 and
rx4 each with a corresponding redshift and template number, with the peaks
separated by at least 600km/s. High values of rx and rx2, particularly
relative to rx3 and rx4, can then be used to select candidate blended spectra.
Note (2): Spectral classification as follows:
PG = passive template
ELG = emission line template
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 12-Jan-2016