J/ApJ/901/123 Ghostly damped Lyα systems in SDSS DR14 (Fathivavsari, 2020)
Using machine learning to find ghostly damped Lyα systems in the SDSS
DR14.
Fathivavsari H.
<Astrophys. J., 901, 123 (2020)>
=2020ApJ...901..123F 2020ApJ...901..123F
ADC_Keywords: QSOs; Spectra, optical; Redshifts; Intergalactic medium
Keywords: Interstellar absorption ; Interstellar line absorption ; Quasars ;
Quasar absorption line spectroscopy ; Active galactic nuclei ;
Intergalactic medium ; Circumgalactic medium
Abstract:
We report the discovery of 59 new ghostly absorbers from the Sloan
Digital Sky Survey Data Release 14. These absorbers, with
zabs∼zQSO, reveal no Lyα absorption, and they are mainly
identified through the detection of strong metal absorption lines in
the spectra. The number of such previously known systems is 30. The
new systems are found with the aid of machine-learning algorithms. The
spectra of 41 (out of total of 89) absorbers also cover the Lyβ
spectral region. By fitting the damping wings of the Lyβ
absorption in the stacked spectrum of 21 (out of 41) absorbers with
relatively stronger Lyβ absorption, we measured an HI column
density of log N(HI)=21.50. This column density is 0.5dex higher than
that of the previous work. We also found that the metal absorption
lines in the stacked spectrum of the 21 ghostly absorbers with
stronger Lyβ absorption have similar properties as those in the
stacked spectrum of the remaining systems. This circumstantial
evidence strongly suggests that the majority of our ghostly absorbers
are indeed DLAs.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table5.dat 30 89 Newly found ghostly absorbers
--------------------------------------------------------------------------------
See also:
V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
VII/286 : SDSS quasar catalog, fourteenth data release (Paris+, 2018)
VII/289 : SDSS quasar catalog, sixteenth data release (DR16Q) (Lyke+, 2020)
J/ApJ/508/200 : QSO low-z Lyα absorbers (Tripp+, 1998)
J/ApJ/524/536 : Nearby Lyα quasar absorbers (Impey+, 1999)
J/PASP/116/622 : SDSS damped Lyα survey: DR1 (Prochaska+, 2004)
J/ApJ/635/123 : The SDSS-DR3 damped Lyα survey (Prochaska+, 2005)
J/A+A/547/L1 : SDSS-III DR9 DLA catalogue (Noterdaeme+, 2012)
J/MNRAS/449/1536 : New damped Lyα absorbers (Turnshek+, 2015)
J/MNRAS/472/1850 : Detecting damped Lyα absorbers (Garnett+, 2017)
J/MNRAS/477/5625 : SDSSDR12 eclipsing damped Lya systems (Fathivavsari+, 2018)
J/ApJ/888/85 : Ghostly strong Lya abs. in SDSS DR12 (Fathivavsari, 2020)
Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- SDSS SDSS identifier (HHMMSS.ss+DDMMSS.s; J2000)
20- 24 F5.3 --- zQSO [2.045/3.73] QSO emission redshift
26- 30 F5.3 --- zabs [2.035/3.71] Ghostly absorber absorption redshift
--------------------------------------------------------------------------------
History:
Table sent by Greg Gus [AAS] via the author
* SDSS J004730.84+140228.8 is a misprint for J004703.08+140228.8;
corrected by CDS.
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 07-Jan-2022