J/MNRAS/472/1850 Detecting damped Lyα absorbers (Garnett+, 2017)
Detecting damped Ly α absorbers with Gaussian processes.
Garnett R., Ho S., Bird S., Schneider J.
<Mon. Not. R. Astron. Soc., 472, 1850-1865 (2017)>
=2017MNRAS.472.1850G 2017MNRAS.472.1850G (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Redshifts
Keywords: methods: statistical - intergalactic medium -
quasars: absorption lines - galaxies: statistics
Abstract:
We develop an automated technique for detecting damped Lyα
absorbers (DLAs) along spectroscopic lines of sight to quasi-stellar
objects (QSOs or quasars). The detection of DLAs in large-scale
spectroscopic surveys such as SDSS III sheds light on galaxy formation
at high redshift, showing the nucleation of galaxies from diffuse gas.
We use nearly 50000 QSO spectra to learn a novel tailored Gaussian
process model for quasar emission spectra, which we apply to the DLA
detection problem via Bayesian model selection. We propose models for
identifying an arbitrary number of DLAs along a given line of sight.
We demonstrate our method's effectiveness using a large-scale
validation experiment, with excellent performance. We also provide a
catalogue of our results applied to 162858 spectra from SDSS-III data
release 12.
Description:
To verify the validity of our proposed method, we computed the
posterior probability of MDLA for 162858 quasar sightlines in the
DR12Q (Paris et al., Cat. VII/279) release of SDSS III.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 89 297301 The 297301 objects in the SDSS-III DR12Q catalog,
and the results of our cuts
table2.dat 108 162858 The 162858 objects in the SDSS-III DR12Q catalog
processed by our proposed GP DLA detection method,
and a summary of derived quantities of interest
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See also:
VII/279 : SDSS quasar catalog: twelfth data release (Paris+, 2017)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 9 I9 --- ID SDSS Thing id
11- 28 A18 --- SDSS SDSS name (HHMMSS.ss+DDMMSS.s)
30- 33 I4 --- Plate SDSS plate number
35- 39 I5 --- MJD SDSS MJD number
41- 44 I4 --- Fiber Fibre number
46- 56 F11.7 deg RAdeg Right ascension (J2000)
58- 68 F11.7 deg DEdeg Declination (J2000)
70- 75 F6.4 --- zQSO QSO redshift
77- 84 F8.4 --- SNR Signal-to-noise
86- 89 I4 --- FCut Cut flags
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 9 I9 --- ID Thing id
11- 16 F6.4 --- zmin Redshift search range, lower value
18- 23 F6.4 --- zmax Redshift search range, upper value
25- 32 F8.5 --- logPr1A Prior probability of the MDLA model,
logPr(-DLA|zQSO)
34- 41 F8.5 --- logPr1B Prior probability of the MDLA(1) model,
logPr(DLA|zQSO)
43- 54 E12.6 --- logpA Model evidence for MDLA model,
logp(y|lambda,v,zSAO,M-DLA)
56- 67 E12.6 --- logpB Model evidence for MDLA(1) model,
logp(y|lambda,v,zSAO,M-DLA(1))
69- 80 E12.6 --- Pr2A Posterior probability of the MDLA model,
Pr(tMDLA|DzQQSO)
82- 93 E12.6 --- Pr2B Posterior probability of the MDLA(1) model,
Pr(MDLA|DzQQSO)
95-100 F6.4 --- zSLA SLA redshift
102-108 F7.4 [cm-2] logNHI HI column density
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 24-Jun-2020