J/ApJ/872/21 SDSS RM project: <10day CIV BAL variability (Hemler+, 2019)
The Sloan Digital Sky Survey Reverberation Mapping project: systematic
investigations of short-timescale CIV broad absorption line variability.
Hemler Z.S., Grier C.J., Brandt W.N., Hall P.B., Horne K., Shen Y.,
Trump J.R., Schneider D.P., Vivek M., Bizyaev D., Oravetz A., Oravetz D.,
Pan K.
<Astrophys. J., 872, 21 (2019)>
=2019ApJ...872...21H 2019ApJ...872...21H
ADC_Keywords: QSOs; Spectra, optical; Equivalent widths; Redshifts
Keywords: galaxies: active; galaxies: kinematics and dynamics; galaxies: nuclei;
quasars: absorption lines
Abstract:
We systematically investigate short-timescale (<10 day rest-frame) CIV
broad absorption-line (BAL) variability to constrain quasar-wind
properties and provide insights into BAL-variability mechanisms in
quasars. We employ data taken by the Sloan Digital Sky Survey
Reverberation Mapping project, as the rapid cadence of these
observations provides a novel opportunity to probe BAL variability on
shorter rest-frame timescales than have previously been explored. In a
sample of 27 quasars with a median of 58 spectral epochs per quasar,
we have identified 15 quasars (55-14+18%), 19 of 37 CIV BAL
troughs (51-12+15%), and 54 of 1460 epoch pairs (3.7%±0.5%) that
exhibit significant CIV BAL equivalent-width variability on timescales
of less than 10 days in the quasar rest frame. These frequencies
indicate that such variability is common among quasars and BALs,
though somewhat rare among epoch pairs. Thus, models describing BALs
and their behavior must account for variability on timescales down to
less than a day in the quasar rest frame. We also examine a variety of
spectral characteristics and find that, in some cases, BAL variability
is best described by ionization-state changes, while other cases are
more consistent with changes in covering fraction or column density.
We adopt a simple model to constrain the density and radial distance
of two outflows appearing to vary by ionization-state changes,
yielding outflow density lower limits consistent with previous work.
Description:
In 2014, the Sloan Digital Sky Survey Reverberation Mapping project
(SDSS-RM; Shen+ 2015, J/ApJS/216/4) obtained 32 epochs of spectra of
849 quasars using the Baryon Oscillation Spectroscopic Survey (BOSS)
spectrograph on the SDSS 2.5m telescope; 12-13 additional epochs per
year were taken subsequently in 2015, 2016, and 2017 as a part of the
SDSS-IV eBOSS program (Dawson+ 2016AJ....151...44D 2016AJ....151...44D and
Blanton+ 2017AJ....154...28B 2017AJ....154...28B), yielding 69 total epochs of
spectroscopy over the four years. The BOSS spectrograph covers a
wavelength range of 3650-10400Å and has a spectral resolution of
R=2000 with a field of view that is 3° in diameter.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 78 27 Final quasar sample information
table3.dat 50 37 CIV BAL measurements from 2014 mean spectra
table4.dat 38 1587 CIV BAL measurements per epoch
table5.dat 93 54 Short-timescale variability among epoch pairs
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See also:
VIII/90 : The FIRST Survey Catalog, Version 12Feb16 (Becker+ 2012)
V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
VII/286 : SDSS quasar catalog, fourteenth data release (Paris+, 2018)
J/A+AS/125/149 : CHIANTI --Atomic Database For Emission Lines I. (Dere+ 1997)
J/AJ/131/2766 : Quasar luminosity function from SDSS-DR3 (Richards+, 2006)
J/ApJ/685/773 : X-ray-UV relations in SDSS DR5 QSOs (Gibson+, 2008)
J/ApJ/696/924 : UV and X-Ray radio-quiet QSOs (Gibson+, 2009)
J/ApJ/692/758 : BAL QSOs in SDSS-DR5 (Gibson+, 2009)
J/ApJ/709/611 : The multi-component absorber QSO 0318-0600 (Dunn+, 2010)
J/MNRAS/434/1411 : Variability of broad emission lines in QSOs (Woo+, 2013)
J/ApJ/777/168 : CIV & SiIV BAL troughs in SDSS (Filiz+, 2013)
J/ApJ/791/88 : C IV BAL troughs properties in quasars (Filiz+, 2014)
J/MNRAS/440/799 : Low Ionization BALQSOs MgII & AlIII var. (Vivek+, 2014)
J/ApJS/216/4 : SDSS-RM project: technical overview (Shen+, 2015)
J/MNRAS/454/3962 : 188 CIV BAL QSOs from SDSS DR7 (He+, 2015)
J/ApJ/805/96 : SDSS-RM project: velocity dispersions of QSOs (Shen+, 2015)
J/ApJ/814/150 : Variability of SDSS broad absorption line QSOs (Wang+, 2015)
J/ApJS/219/39 : QSOs selection from SDSS and WISE (Richards+, 2015)
J/ApJ/824/130 : SDSS/BOSS/TDSS CIV BAL quasars (Grier+, 2016)
J/ApJ/818/30 : Lag measurements for z<0.8 QSOs from SDSS-RM (Shen+, 2016)
J/ApJ/831/7 : SDSS-RM project: peak velocities of QSOs (Shen+, 2016)
J/MNRAS/469/323 : SDSS quasars with PV broad absorption (Capellupo+, 2017)
J/ApJ/851/21 : SDSS RM project first year of observations (Grier+, 2017)
J/A+A/616/A114 : CIV BAL disappearance in SDSS QSOs (De Cicco+, 2018)
J/ApJ/862/22 : CIV BAL SDSS QSO obs. with Gemini (Rogerson+, 2018)
J/other/JAD/24.3 : Optically Variable Quasars in AllWISE/PS1 (Usatov, 2018)
J/A+A/622/A15 : Broad absorption line quasars in LDR1 (Morabito+, 2019)
J/ApJS/249/17 : SDSS QSO DR14 spectral properties (Rakshit+, 2020)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- SDSS SDSS DR10 designation (JHHMMSS.ss+DDMMSS.s)
21- 22 A2 --- --- [RM]
24- 26 I3 --- RMID [39/786] Reverberation Mapping (RM) ID
(from Shen+, 2015, J/ApJS/216/4)
28- 36 F9.5 deg RAdeg [211.47/216.1] Right Ascension (J2000) (1)
38- 45 F8.5 deg DEdeg [52/54.5] Declination (J2000) (1)
47- 50 F4.2 --- z [1.62/3.72] Redshift (Shen+ 2019ApJS..241...34S 2019ApJS..241...34S)
52- 56 F5.2 mag imag [16.4/20.4] SDSS i-band (AB) magnitude,
SDSS DR10 (1)
58- 62 F5.2 --- SN1700 [6/52] Median signal-to-noise (2)
64- 65 I2 --- Nep [3/69] Number of epochs
67- 71 F5.2 d dtRest [2/13.8] Median rest-frame time separation
between observations
73- 73 A1 --- cFit Continuum Fit (3)
75- 78 A4 --- eFit Emission-Line Fit (4)
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Note (1): J2000 Position and magnitude measurements were obtained
from SDSS Data Release 10 (Ahn+ 2014ApJS..211...17A 2014ApJS..211...17A). The
i-magnitudes provided are point-spread function magnitudes that have not
been corrected for Galactic extinction.
Note (2): The median SN of the pixels in the 1650-1750Å region in the quasar
rest frame.
Note (3): Continuum Fit explanations as follows:
R = a reddened power law continuum fit was used for this quasar;
U = an unreddened power law was used.
Note (4): Emission-Line explanations as follows:
V = A Voigt profile to was used to represent the CIV emission line;
DG = A double-Gaussian profile was used;
GH = A Gauss-Hermite profile was used;
None = Unable to obtain any acceptable emission-line fit, so the
continuum-only fit was adopted.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 A2 --- --- [RM]
4- 6 I3 --- RMID [39/786] Reverberation Mapping (RM) ID
(from Shen+, 2015, J/ApJS/216/4)
8- 8 A1 --- m_RMID [AB] BAL ID
10- 14 I5 km/s Vmax [2464/29148] BAL velocity bounds, max
16- 20 I5 km/s Vmin [-338/21819] BAL velocity bounds, min
22- 26 I5 km/s Vcent [1371/23559] Absorbed-flux weighted centroid
velocity
28- 31 F4.2 --- Depth [0.12/0.75] Normalized mean fractional depth
33- 36 F4.1 0.1nm EW [2.2/88.5] CIV equivalent width;
in Angstrom units
38- 40 F3.1 0.1nm e_EW [0.1/1.3] Uncertainty in EW
42- 48 A7 --- FA14 BAL designation (1)
50 A1 --- Pv Flag on PV or mini-BAL (2)
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Note (1): BAL designation according to whether or not BALs or mini-BALs are
present for SiIV and AlIII, as defined by Filiz Ak+ (2014, J/ApJ/791/8);
Classification as follows:
CIV00 = neither SiIVλλ1393,1403 nor
AlIIIλλ1855,1863 is present at velocities
corresponding to an identified CIV BAL (15 occurrences);
CIVS0 = a SiIV BAL is present but AlIII is not detected (13 occurrences);
CIVSA = both SiIV and AlIII BALs are present at corresponding velocities
(6 occurrences);
CIVN0 = the SiIV line is not completely covered by our spectrum at those
velocities or we are unable to otherwise determine whether or not it
is present, so we are unsure of the designation.
See Section 4.3.3 for further explanations.
Note (2): This column indicates whether or not there is a suspected
corresponding PV BAL or mini-BAL (see Section 4.3.4). Code as follows:
Y = PVλλ1112,1118 is suspected to be present (6 occurrences);
N = not suspected.
Entries with no data indicate that the PV region is not covered by the
SDSS spectra.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 A2 --- --- [RM]
4- 6 I3 --- RMID [39/786] Reverberation Mapping (RM) ID
(from Shen+, 2015, J/ApJS/216/4)
8- 8 A1 --- m_RMID [AB] BAL ID
10- 17 F8.2 d MJD Modified Julian Date (JD-2400000.5)
19- 23 I5 km/s Vcent [1320/33680] Absorbed-flux weighted centroid
velocity
25- 29 F5.2 --- Depth [-0.02/0.8] Normalized mean fractional depth
31- 34 F4.1 0.1nm EW [-0.2/94.3] CIV equivalent width;
in Angstrom units
36- 38 F3.1 0.1nm e_EW [0/1.4] Uncertainty in EW; in Angstrom units
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Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 A2 --- --- [RM]
4- 6 I3 --- RMID [128/786] Reverberation Mapping (RM) ID
(from Shen+, 2015, J/ApJS/216/4)
8- 8 A1 --- m_RMID [AB] BAL ID
10- 17 F8.2 d MJD1 First Epoch, Modified Julian Date
19- 26 F8.2 d MJD2 Second Epoch, Modified Julian Date
28- 31 F4.2 d dtRest [0.5/8.3] Rest-frame time separation
between first and second epochs
33- 36 F4.1 0.1nm EW1 [0.6/47.1] CIV equivalent width at MJD1;
in Angstrom units
38- 40 F3.1 0.1nm e_EW1 [0/0.7] Uncertainty in EW1
42- 45 F4.1 0.1nm EW2 [0.6/47.1] CIV equivalent width at MJD2;
in Angstrom units
47- 49 F3.1 0.1nm e_EW2 [0/0.7] Uncertainty in EW2
51- 54 F4.1 0.1nm dEW [-5.8/6.4] Change in equivalent width;
in Angstrom units
56- 58 F3.1 0.1nm e_dEW [0.1/1] Uncertainty in dEW
60- 65 F6.2 --- sigdEW [-22.4/10.1] Significance of the change in EW
67- 72 F6.2 --- GB [4.1/105.3] G value, BAL region (1)
74- 78 F5.2 --- GC [-1.4/1.9] G value, continuum region (1)
80- 83 F4.2 % fchip1 [0/0.93] fraction of pixels, χ>1
85- 88 F4.2 % fchim1 [0/0.86] fraction of pixels, χ<-1
90- 93 I4 km/s dVco [290/7250] Coordinated velocity (2)
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Note (1): Following Equation (3), G=(χ2-(N-1))/(2(N-1)0.5)
where the χ2 quantity is the square of the difference between fluxes
at two spectral epochs divided by their combined uncertainty, summed
over the N pixels within a specified region. See Section 3.3.
Note (2): Largest velocity width with "coordinated" variability across an
individual trough. See Section 4.3.1.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 31-Jul-2020