J/A+A/616/A114 CIV BAL disappearance in SDSS QSOs (De Cicco+, 2018)
C IV broad absorption line disappearance in a large SDSS QSO sample.
De Cicco D., Brandt W.N., Grier C.J., Paolillo M., Filiz Ak N.,
Schneider D.P., Trump J.R.
<Astron. Astrophys., 616, A114 (2018)>
=2018A&A...616A.114D 2018A&A...616A.114D (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Spectroscopy ; Redshifts ; Equivalent widths
Keywords: galaxies: active - quasars: general - quasars: absorption lines -
galaxies: evolution
Abstract:
Broad absorption lines (BALs) in the spectra of quasi-stellar
objects (QSOs) originate from outflowing winds along our line of
sight; winds are thought to originate from the inner regions of the
QSO accretion disk, close to the central supermassive black hole
(SMBH). These winds likely play a role in galaxy evolution and are
responsible for aiding the accretion mechanism onto the SMBH. Several
works have shown that BAL equivalent widths can change on typical
timescales from months to years; such variability is generally
attributed to changes in the covering factor (due to rotation and/or
changes in the wind structure) and/or in the ionization level of the
gas.
We investigate BAL variability, focusing on BAL disappearance.
We analyze multi-epoch spectra of more than 1500 QSOs - the largest
sample ever used for such a study - observed by different programs
from the Sloan Digital Sky Survey-I/II/III (SDSS-I/II/III), and search
for disappearing CIV BALs. The spectra cover a rest-frame time
baseline ranging from 0.28 to 4.9yr; the source redshifts range from
1.68 to 4.27.
We detect 73 disappearing BALs in the spectra of 67 unique sources.
This corresponds to 3.9% of BALs disappearing within 4.9yr (rest
frame), and 5.1% of our BAL QSOs exhibit at least one disappearing BAL
within 4.9yr (rest frame). We estimate the average lifetime of a BAL
along our line of sight (~=80-100yr), which appears consistent with
the accretion disk orbital time at distances where winds are thought
to originate. We inspect various properties of the disappearing BAL
sample and compare them to the corresponding properties of our main
sample. We also investigate the existence of a correlation in the
variability of multiple troughs in the same spectrum, and find it
persistent at large velocity offsets between BAL pairs, suggesting
that a mechanism extending on a global scale is necessary to explain
the phenomenon. We select a more reliable sample of disappearing BALs
on the basis of some criteria adopted in a previous publication, where
a subset of our current sample was analyzed, and compare the findings
from the two works, obtaining generally consistent results.
Description:
Our analysis of CIV BAL disappearance is based on data from BOSS,
which is the largest of the four SDSS-III surveys (Eisenstein et al.,
2011AJ....142...72E 2011AJ....142...72E).
Observations were made with the 2.5m SDSS telescope (Gunn et al.,
2006AJ....131.2332G 2006AJ....131.2332G) at Apache Point Observatory, New Mexico, USA.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 91 67 QSOs in the P4 sample
tablea2.dat 67 72 Parameters of disappearing BAL troughs
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See also:
VII/252 : SDSS-DR5 quasar catalog (Schneider+, 2007)
J/MNRAS/405/2302 : Improved redshifts for SDSS quasar spectra (Hewett+, 2010)
J/ApJS/194/45 : QSO properties from SDSS-DR7 (Shen+, 2011)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- ID Source identification number in this work
6- 24 A19 --- SDSS Source SDSS identification (JHHMMSS.ss+DDMMSS.s)
26- 31 F6.4 --- z Redshift from Hewett & Wild
(2010, Cat. J/MNRAS/405/2302)
33- 38 F6.4 --- e_z rms uncertainty on z
40- 44 F5.2 mag imag i-band magnitude from Schneider et al.
(2007AJ....134..102S 2007AJ....134..102S, Cat. VII/252)
46- 49 F4.2 mag e_imag rms uncertainty on imag
51- 57 F7.3 mag iMAG Absolute i-band magnitude from Shen et al.
(2011, Cat. J/ApJS/194/45)
59- 72 A14 --- PMF1 Plate-MJD-fiber identifying each SDSS-I/II
spectrum where a BAL trough is detected
74 I1 --- Ntr1 Number of BAL troughs detected in the same
spectrum
76- 89 A14 --- PMF2 Plate-MJD-fiber of corresponding BOSS spectrum
(MJD≥55176) where disappearance occurs (1)
91 I1 --- Ntr2 Number of BAL troughs detected in the same
spectrum
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Note (1): in cases of multiple spectra, we adopt the rule defined in Sect. 4.1.
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Byte-by-byte Description of file: tablea2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- ID Source identification number in this work
6- 24 A19 --- SDSS Source SDSS identification (JHHMMSS.ss+DDMMSS.s)
26- 30 I5 d MJD MJD of the SDSS-I/II epoch where the EW of the
disappearing BAL trough is measured (1)
32- 36 F5.2 0.1nm EW Rest-frame EW measurement
38- 41 F4.2 0.1nm e_EW rms uncertainty on EW
43- 48 I6 km/s vmax Maximum velocity of the BAL trough
50- 55 I6 km/s vmin Minimum velocity of the BAL trough
57- 63 F7.2 d DT Rest-frame Δt between the SDSS-I/II
epoch where the BAL trough is detected and the
BOSS epoch where disappearance of the same
BAL is observed
65 A1 --- P8 [0/1] BALs belonging to the P8 sample? (2)
67 A1 --- PP [0/1] BALs belonging to the pristine sample? (2)
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Note (1): that is, the latest SDSS-I/II epoch where the BAL trough is detected.
Note (2): Flag as follows:
1 = BALs belonging to the sample
0 = BALs not belonging to the sample
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 23-Oct-2018