J/MNRAS/434/163 QSOs narrow absorption line variability (Hacker+, 2013)
Narrow absorption line variability in repeat quasar observations from the Sloan
Digital Sky Survey.
Hacker T.L., Brunner R.J., Lundgren B.F., York D.G.
<Mon. Not. R. Astron. Soc. 434, 163 (2013)>
=2013MNRAS.434..163H 2013MNRAS.434..163H
ADC_Keywords: QSOs ; Redshifts ; Equivalent widths
Keywords: catalogues - surveys - quasars: absorption lines - quasars: general
Abstract:
We present the results from a time domain study of absorption lines
detected in quasar spectra with repeat observations from the Sloan
Digital Sky Survey Data Release 7 (SDSS DR7). Beginning with over
4,500 unique time separation baselines of various absorption line
species identified in the SDSS DR7 quasar spectra, we create a
catalogue of 2,522 quasar absorption line (QAL) systems with two to
eight repeat observations, representing the largest, unbiased, and
homogeneous collection of multi-epoch absorption systems ever
published. To investigate these systems for time-variability of narrow
absorption lines, we refine this sample based on the reliability of
the system detection, the proximity of pixels with bright sky
contamination to individual absorption lines, and the quality of the
continuum fit. Variability measurements of this sub-sample based on
the absorption line equivalent widths yield a total of 33 systems with
indications of significantly variable absorption strengths on
time-scales ranging from one day to several years in the rest frame of
the absorption system. Of these, at least 10 are from a class known as
intervening absorption systems caused by foreground galaxies along the
line of sight to the background quasar. This is the first evidence of
possible absorption line variability detected in intervening systems,
and their short time-scale variations suggest that small-scale
structures (∼10-100AU) are likely to exist in their host foreground
galaxies.
Description:
Catalogues of 2,522 QAL systems and 33 variable NAL systems detected
in SDSS DR7 quasars with repeat observations. The object identifiers,
position coordinates, and plate-MJD-fibre designations are taken from
the SpecObjAll table in the SDSS Catalogue Archive Server (CAS) while
the quasar redshifts (zqso) are from Hewett & Wild (2010, Cat.
J/MNRAS/405/2302). The absorption system redshift (zabs), system
grade, and detected lines are outputs of the York et al. (2013, in.
prep.) QAL detection pipeline. Some absorption lines are flagged based
on alternate identifications (a), proximity of masked pixels (b), or
questionable continuum fits (c).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 694 5794 Catalogue of Quasar Absorption Line (QAL) systems
with repeat observations
table3.dat 171 341 Variable NAL systems (Narrow-Line absorption)
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See also:
VII/260 : The SDSS-DR7 quasar catalog (Schneider+, 2010)
J/MNRAS/405/2302 : Improved redshifts for SDSS quasar spectra (Hewett+, 2010)
http://www.sdss.org : SDSS Home Page
http://casjobs.sdss.org/CasJobs/ : SDSS CAS Home Page
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- SDSS SDSS object designation (HHMMSS.ss+DDMMSS.s)
20- 31 F12.8 deg RAdeg Right ascension (J2000)
33- 46 F14.10 deg DEdeg Declination (J2000)
48- 53 F6.4 --- zqso [0.3/4.5] Quasar redshift (Hewett & Wild 2010,
Cat. J/MNRAS/405/2302)
55- 60 F6.4 --- zabs i[0.3/3.7] Absorption system redshift
62- 74 E13.9 --- beta Absorption system velocity β=v/c
(in quasar rest frame)
76- 79 I4 --- Plate SDSS spectroscopic plate number
81- 85 I5 d MJD SDSS Modified Julian Date (MJD) of observation
87- 89 I3 --- Fiber SDSS spectroscopic fiber number
91- 93 A3 --- Grade Absorption system confidence grade (1)
95-537 A443 --- Lines Detected absorption lines (2)
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Note (1): Confidence grades are assigned by the York et al. (2013, in
prep.) QAL pipeline to each identified absorption system, according
to the following criteria (only unblended lines detected longward of
the Lymanα forest contribute to the grade of a system):
A = ≥ 4 lines, σ≥4
B = 3 lines, σ≥4
C = 2 lines, σ≥4 (CIV or MgII doublet)
C* = 2 lines, σ≥4 (CIV or MgII line and 1 other)
C** = 2 lines, σ≥4 (neither belongs to CIV or MgII)
D = 1 line, σ≥4 and 1 line, 3≤σ<4
D* = 2 lines, 3≤σ<4
E = 1 line, σ≥ 4
E* = 1 line, 3≤σ<4
N = no identified systems present
Note (2): The detected absorption lines are reported by the York QAL pipeline
comprised of an absorption line-finding algorithm followed by a code that
sorts detected lines into systems at the same redshift; the equivalent
widths of observed absorbers are calculated in the absorber frame of
reference: (Wobs/(1+zabs)), and 1-σ errors are calculated using the
error array provided by the SDSS. Each detected line is written here as
"Elλabc", where "El" is the element and ionization (e.g. FeII),
λ the rest wavelength in Angstroms, and "abc" are flags described
in section 2.3, meaning:
a = alternate line identification
b = proximity of masked pixels
c = questionable continuum fit
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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- 2 I2 --- Sys [1/33] System number index
4- 21 A18 --- SDSS SDSS object designation (HHMMSS.ss+DDMMSS.s)
23- 32 F10.6 deg RAdeg Right ascension (J2000)
34- 45 F12.8 deg DEdeg Declination (J2000)
47- 52 F6.4 --- zqso [1.2/3.9] Quasar redshift (Hewett & Wild 2010,
Cat. J/MNRAS/405/2302)
54- 59 F6.4 --- zabs [0.6/3.0] Narrow Absorption Line (NAL)
system redshift
61- 69 F9.7 --- beta NAL system velocity
(β=v/c in quasar rest frame)
71- 74 I4 --- Plate1 SDSS plate number - first observation
76- 78 I3 --- Fiber1 SDSS fibre number - first observation
80- 84 I5 d MJD1 SDSS MJD - first observation
86- 89 I4 --- Plate2 SDSS plate number - second observation
91- 93 I3 --- Fiber2 SDSS fibre number - second observation
95- 99 I5 d MJD2 SDSS MJD - second observation
101-111 F11.6 d trest Time between observations (quasar rest frame)
113-117 A5 --- Ion Absorption line ion
119-125 F7.2 0.1nm lam0 Absorption line rest wavelength λ0
127-134 F8.6 0.1nm EW1 Equivalent width - first observation
136-144 F9.7 0.1nm e_EW1 Equivalent width error - first observation
146-148 A3 --- f_EW1 Absorption line flag - first observation (3)
150-157 F8.6 0.1nm EW2 Equivalent width - second observation
159-167 F9.7 0.1nm e_EW2 Equivalent width error - second observation
169-171 A3 --- f_EW2 Absorption line flag - second observation (3)
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Note (3): Absorption line flag conditions (see Section 2.3), as follows:
a = alternate line identification
b = proximity of masked pixels
c = questionable continuum fit
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Acknowledgements:
Troy Hacker, troyhacker(at)hotmail.com
(End) Patricia Vannier [CDS] 24-Jun-2013