J/ApJ/524/536 Nearby Lyα quasar absorbers (Impey+, 1999)
A study of Lyα quasar absorbers in the nearby universe
Impey C.D., Petry C.E., Flint K.P.
<Astrophys. J. 524, 536 (1999)>
=1999ApJ...524..536I 1999ApJ...524..536I
ADC_Keywords: QSOs ; Spectroscopy
Mission_Name: HST
Keywords: galaxies: halos - intergalactic medium - large-scale structure
of universe - quasars: absorption lines
Abstract:
Spectroscopy of 10 quasars obtained with the Goddard High Resolution
Spectrograph (GHRS) of the Hubble Space Telescope (HST) is presented.
In the 10 sight lines, we detect 357 absorption lines above a
significance level of 3σ and 272 lines above a significance
level of 4.5σ. Automated software is used to detect and identify
the lines, almost all of which are unresolved at the GHRS G140L
resolution of 200km/s. After identifying Galactic lines, intervening
metal lines, and higher order Lyman lines, we are left with 139
Lyα absorbers in the redshift range 0<z<0.22 (lines within
900km/s of geocoronal Lyα are not selected). These diffuse
hydrogen absorbers have column densities that are mostly in the range
1013-1015cm-2 for an assumed Doppler parameter of 30km/s. The
number density of lines above a rest equivalent width of 0.24Å,
dN/dz=38.3±5.3, agrees well with the measurement from the Quasar
Absorption-Line Key Project. There is marginal evidence for cosmic
variance in the number of absorbers detected among the 10 sight lines.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 132 355 Absorption-Line measurements & identifications
--------------------------------------------------------------------------------
See also:
VII/23 : A catalogue of absorption lines in QSO spectra
J/ApJS/77/203 : QSO absorption systems (Junkkarinen+ 1991)
J/ApJS/97/1 : HST Quasar Absorption Line Key Project. X. (Lockman+ 1995)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 13 A13 --- Name QSO name
15- 18 F4.2 --- z QSO redshift
21- 22 I2 --- Number Absorption line number
25- 31 F7.2 0.1nm Wave Observed vacuum heliocentric line
wavelength in Angstroms
34- 37 F4.2 0.1nm e_Wave Error in Wave in Angstroms
39 A1 --- f_Wave [h] Flag on Wave (1)
41- 45 F5.3 0.1nm EqWidth Equivalent width in Angstroms
48- 52 F5.3 0.1nm e_EqWidth Error in EqWidth in Angstroms
57- 60 F4.2 0.1nm FWHM Full Width Half Maximum in Angstroms (2)
63- 66 F4.2 0.1nm e_FWHM Error in the FWHM in Angstroms
69- 73 F5.2 --- Chi2 The Χ2 of the line fit
79- 83 F5.2 --- Signif Significance of the line width (3)
86- 91 F6.2 --- SignifL Significance of the line width (4)
93 A1 --- f_SignifL [i] Flag on SignifL (5)
95-101 F7.5 --- zAbsorp ? Redshift of the absorption system
103-113 A11 --- ID Line identification
115 A1 --- f_ID [*] Indicates excited transitions
116 A1 --- n_ID [fg] Note on ID (6)
118-121 I4 0.1nm RWave ? Rest wavelength of line
122 A1 --- f_RWave [ab] Indicates one of the two strongest
transitions of the N I 1200 angstrom triplet
127-131 F5.2 0.1nm DWave ? Wavelength residual in Angstroms (7)
--------------------------------------------------------------------------------
Note (1): On wing of damped Lyα; Wave is very uncertain
Note (2): Lines with a value of 0.80±0.00 were fit with the FWHM set
to the minimum allowed value.
Note (3): Significance of the line defined as EqWidth/σW, where
σW is the error in the measured equivalent width.
Note (4): Significance of the line defined as EqWidth/σlim, where
σlim is the 1σ (observed) limiting equivalent width.
Note (5): Based on a single comparison with a higher resolution
spectrum of 3C 273, a significant fraction of lines with
3.0 < SignifL < 4.5 may be false detections.
Note (6):
f = Alternately identified as Si II 1304 at z = 0.0000 with
residual 0.45 Angstroms.
g = Alternately identified as Si II 1190 at z = 0.1419 with
residual -0.53 Angstroms.
Note (7): Defined as (λmeasured - λpredicted)
--------------------------------------------------------------------------------
History:
From ApJ electronic edition
(End) Greg Schwarz [AAS] 13-Mar-2000