Constraining Variable High Velocity Winds from Broad Absorption Line Quasars with Multi-Epoch Spectroscopy

0.14 MB·English

by  Daryl Haggard

**VolumeTitle**
ASPConferenceSeries,Vol.**VolumeNumber**
**Author**
(cid:13)c**CopyrightYear**AstronomicalSocietyofthePacific
Constraining VariableHighVelocityWinds from Broad Absorption
Line QuasarswithMulti-Epoch Spectroscopy
2
1
0 DarylHaggard,1 KenzaS.Arraki,2 PaulJ.Green,3 TomAldcroft,3 andScottF.
2 Anderson4

n
1CenterforInterdisciplinary Exploration andResearchinAstrophysics
a
J (CIERA),NorthwesternUniversity, Evanston,IL60208, USA

3
2DepartmentofAstronomy,NewMexicoStateUniversity, LasCruces,NM
1
88003, USA

]
O 3Harvard-Smithsonian CenterforAstrophysics, Cambridge,MA02138, USA
C 4DepartmentofAstronomy,University ofWashington, Seattle, WA98195, USA
.
h
p Abstract. Broadabsorptionline(BAL)quasarsprobethehighvelocitygasejected
- by luminous accreting black holes. BAL variability timescales place constraints on
o
thesize, location,anddynamicsoftheemittingandabsorbinggasnearthesupermas-
r
t sive black hole. We presentmulti-epochspectroscopyof seventeenBAL QSOs from
s
a theSloanDigitalSkySurvey(SDSS)usingtheFredLawrenceWhippleObservatory’s
[ 1.5mtelescope’sFASTSpectrograph.TheseobjectswereidentifiedasBALsinSDSS,

observedwithChandra,andthenmonitoredwithFASTatobserved-framecadencesof
1
1, 3, 9, 27, and81days, aswellas1and2years. We alsomonitora setofnon-BAL
v
quasarswithmatchedredshiftandluminosityascontrols. Weidentifysignificantvari-
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abilityintheBALs,particularlyatthe1and2yearcadences,anduseitsmagnitudeand
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frequencytoconstraintheoutflowsimpactingthebroadabsorptionlineregion.
8
2
.
1
0
2
1 1. Introduction
:
v
i Studies of quasar mass outflows are rapidly reshaping our understanding of physics
X
near the SMBH. Though the ∼parsec scale emitting/absorbing regions near SMBHs
r willremainspatiallyunresolvedfortheforeseeablefuture(milliarcsecatz∼0.01),time-
a
dependent calculations (Progaetal. 2000) show that disk wind instabilities result in
a filamentary substructure, which gives rise to column density variations along our
sightline. Combined withrotation, spectroscopic variability timescale information can
therefore constrain absorber size scales, viz. a ∼ v ∆t. Though outflows likely
V trans
accompany allluminous accretion disks, broad absorption line (BAL)quasars provide
themostdramaticexamples(e.g.,Halletal. 2011)—theirmassiveoutflowsdisplayP-
Cygniprofilesthatspanvelocitiesto∼ 0.3candarevisibleinthespectraof15−40%of
optically-selected quasars(e.g.,Daietal.2008;Gibsonetal.2009;Allenetal.2011).
WepresentaBALspectroscopicvariabilitycampaign(D.Haggardetal.2011,inpreparation)
thatincludesseventeeni< 17BALQSOsfromtheSDSSwithChandraX-rayfluxand
spectral information, aswellas f /f (another keyindicator ofabsorption). Wedraw
x opt
from the huge population of non-BAL SDSS QSOs to derive a sample of 10 control
1
2 DarylHaggard,etal
Figure1. (Left)AverageCIVBALequivalentwidth(<EW>,units: 1000km/s;top),the
changeinEW(∆EW,units: 1000km/s;middle),andthemagnitudeofthefractionalchange
inEW(bottom) against therest-frametimebetween epochs (∆t). Dataarefromour FAST
study(circles,D.Haggardetal.2011,inpreparation),andseveralpreviousstudies(triangles,
Barlowetal. 1993; crosses,Lundgrenetal. 2007; squares,Gibsonetal. 2008). Solidlines
(middle)markthesquarerootoftheunbiasedsamplevariancefromaslidingwindowof15
time-orderedentries. Theenvelopeof∆EW expandswithtime. The6yearcadence(∆t=2
years rest-frame at z = 2) scheduled for early 2012 will fill the crucial gap at 1 ≤ ∆t ≤ 3
years. (Right) Thetotalwidthof each CIV variableregion displayed versus rest-frame∆t.
Thesub-paneldisplaysahistogramofthenumberofpointswithagivenvelocitywidth.
QSOs, well-matched in i magand redshift (and thus in absolute mag M). Monitoring
i
is performed with the FAST spectrograph at the Fred Lawrence Whipple Observatory
1.5m Tillinghast telescope. Since the variability timescale is not known, we sample
geometricallyacross3nights,thenonenighteachat9,27,and81days,and1,2,and6
years(the6yearcadenceobservations arescheduled forearly2012).
2. Results&Discussion
OurensemblesampleisrepresentedinFigure1,whereweshowvariationsinequivalent
widthandvelocitywidth. WeobservevariabilityinmorethanoneBAL(CIVandSiIV)
and most strongly at multi-year times scales (Fig. 1). In early 2012, wewill complete
the6-yearcadence,fillingacrucialgap,andincludespectroscopyfromSDSStoextend
our baseline to > 10 years (> 5 years rest-frame). We are also developing an analysis
∼ ∼
pipeline with an eye toward future spectroscopic variability studies, in anticipation of
theexplosion intime-domain imaging(e.g.,PanSTARRSandLSST).
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