J/ApJ/718/392 SDSS Lyman limit systems at z∼3.5 (Prochaska+, 2010)
A definitive survey for Lyman limit systems at z ∼ 3.5 with the Sloan Digital
Sky Survey.
Prochaska J.X., O'Meara J.M., Worseck G.
<Astrophys. J., 718, 392-416 (2010)>
=2010ApJ...718..392P 2010ApJ...718..392P
ADC_Keywords: Redshifts ; QSOs ; Spectroscopy
Keywords: diffuse radiation - intergalactic medium
Abstract:
We perform a semi-automated survey for τ912≥2 Lyman limit
systems (LLSs) in quasar spectra from the Sloan Digital Sky Survey,
Data Release 7. From a starting sample of 2473 quasars with
zem=3.6-5.0, we analyze 429 spectra meeting strict selection
criteria for a total redshift path Δz=93.8 and identify 190
intervening systems at zLLS≥3.3. We also perform a survey for
proximate LLSs (PLLSs) and find that lPLLS(z) is systematically
lower (∼25%) than intervening systems.
Description:
To assess uncertainties (statistical and systematic) of surveying LLSs
in the SDSS quasar spectra, we obtained independent, higher quality
spectra using the LRIS spectrometer on the Keck I telescope. All
observations were obtained using a 1 arcsec slit which provides an
∼4pix FWHM corresponding to ∼290km/s and ∼220km/s for the blue
(3100-5600Å) and red (5600-8200Å) data, respectively, during a
four night run in 2008 October.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 69 3759 SDSS-DR7 quasar sample
table2.dat 54 607 SDSS-DR7 intervening τ912≥2 LLS survey
table3.dat 41 2593 SDSS-DR7 non-statistical LLS systems and candidates
table6.dat 31 468 SDSS-DR7 proximate τ912≥2 LLS survey
table8.dat 55 32 SDSS-DR7 quasars with KECK+LRIS comparison spectra
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See also:
VII/260 : The SDSS-DR7 quasar catalog (Schneider+, 2010)
II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
J/ApJ/736/42 : HST QSO Catalog (Ribaudo+, 2011)
J/ApJS/195/16 : HST survey for Lyman limit systems. I. (O'Meara+, 2011)
J/ApJ/648/L97 : 2 SDSS QSOs supersolar super-Lyman limit systems (Prochaska+
2006)
http://www.ucolick.org/~xavier/SDSSLLS/ : SDSS LLS survey home page
http://www.sdss.org/ : SDSS home page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Plate Plate number
6- 10 I5 d MJD Modified Julian Date of observation
12- 14 I3 --- Fiber Fiber identification
16- 34 A19 --- SDSS Object name (JHHMMSS.ss+DDMMSS.s)
36- 40 F5.3 --- z Emission line derived redshift (1)
42 I1 --- f_z Flag on z (0=normal) (2)
44- 49 F6.2 --- A ? Absorbed continuum fitting parameter A (3)
51- 57 F7.2 --- B ? Absorbed continuum fitting parameter B (3)
59- 62 F4.2 --- Scale ? Additional scaling factor (4)
64- 67 F4.1 --- S/N ? Estimated signal-to-noise (5)
69 A1 --- f_S/N [I] I: indicates an infinity value for S/N
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Note (1): List of all objects tagged as QSO or HIZ_QSO in the SDSS Data
Release 7 with estimated redshift 5≥z≥3.4.
Note (2): Redshift flag as follows:
0 = Normal;
1 = Not at SDSS reported redshift and/or not a quasar (excluded);
2 = Too low S/N for evaluation (excluded);
3 = Strong BAL (excluded).
Note (3): Absorbed continuum fitting parameters of the form:
C=A+Blog10(λ/Å). We caution the reader that these
models are not meant to describe the intrinsic spectral energy
distributions of the quasars (see the text).
Note (4): Imposed by the authors on the best-fit absorbed quasar continuum.
Note (5): For the absorbed quasar continuum at
λ=λ912(1+zem).
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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- 5 A5 --- --- [zem]
6- 10 A5 --- Range The zem range (< 3.6 or >=3.6) (1)
12- 30 A19 --- SDSS Quasar name (JHHMMSS.ss+DDMMSS.s)
32- 36 F5.3 --- z Emission line derived redshift
38- 42 F5.3 --- zS/N2 Starting redshift at S/N=2 (2)
44- 48 F5.3 --- zS/N3 ? Starting redshift at S/N=3 (2)
50- 54 F5.3 --- zLLS ? Lyman Limit System redshift
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Note (1): The quasars with zem<3.6 are not included in the final analysis.
Note (2): The starting redshifts correspond to the wavelength at which the
absorbed continuum model, starting from zem, no longer exceeds the
smoothed noise array by the specified S/NA912 threshold. This
value is limited to a maximum offset from zem of δz=0.4.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- SDSS Quasar name (JHHMMSS.ss+DDMMSS.s)
21- 25 F5.3 --- z Emission line derived redshift
27- 31 F5.3 --- zLLS Lyman Limit System redshift
33- 36 F4.1 [cm-2] logNHI Log of HI column density (1)
38- 41 A4 --- S/N Signal-to-noise (2)
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Note (1): The logNHI values listed serve as a rough estimate. Typical
uncertainties for systems with NHI<1017.5cm-2 are at
least 0.2dex.
Note (2): Estimate of the S/N of the absorbed continuum (ignoring the effects
of pLLS) at λ=λ912(1+zLLS).
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- SDSS Quasar name
21- 25 F5.3 --- z Emission line derived redshift
27- 31 F5.3 --- zLLS ? Lyman Limit System redshift
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Byte-by-byte Description of file: table8.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- SDSS SDSS name (JHHMMSS.ss+DDMMSS.s)
21- 24 F4.2 --- z Emission line redshift
26- 29 F4.1 --- S/N Signal to noise of the absorbed continuum at
the Lyman limit (S/NA912)
31 I1 --- f_SDSS [1/3] Flag indication (1=no LLS,
2=τ912≥2LLS, 3=τ912<2LLS) (1)
33- 37 F5.3 --- SLLS ? SDSS LLS modeling result
39- 43 F5.3 --- SpLLS ? SDSS proximate LLS modeling result
45- 49 F5.3 --- LLLS ? LRIS LLS modeling result
51- 55 F5.3 --- LpLLS ? LRIS proximate LLS modeling result
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Note (1): τ912 being the optical depth at the Lyman Limit (912Å),
we define a "standard" Lyman Limit System (LLS) to be 1 (LLS=1) when
τ912≥2, i.e. N(HI)≥1017.5cm-2. A flag=2 therefore indicates
a "strong" LLS, a flag=3 a partial LLS.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 07-Jun-2012