Calibrating the use of
quasar Lyman-α emission lines as
probes of reionization
Roban Hultman Kramer
with Zoltán Haiman
Department of Astronomy, Columbia University
[email protected]
[email protected]
Context
Studying this technique: inferring an IGM neutral fraction by measuring the Lyman-α damping wing (statistically, e.g. Mesinger and
Haiman 2007) in the transmission window created by a quasar HII
region.
Goal: to quantify the effect of uncertainties in quasar Lyman-α line
profile fits on the determination of the IGM neutral fraction.
Conclusion: line profile uncertainties introduce substantial but manageable scatter in the IGM neutral fraction determination, with some
important caveats for low neutral fractions.
Using the quasar HII region
The importance of the Ly-α line.
Low-redshift quasar emission lines
Assembling our catalog.
HST Instruments
FOS
HRS
STIS (forthcoming)
MAST query
for observer designation of "QSO" or "quasar".
NED redshifts
are used to determine which observations contain the Ly-α emission
line.
Modeling the line
Red-wing-only fits
Optical depth fits
1.0
1e
12
halfXin55 half_3C 273.fos.h13.b-1
0.8
F
0.6
0.4
0.2
0.0
6
5
4
input: RHII =40.5 Mpc, XHI,in =3.16
fit: RHII =40.5 Mpc, XHI,in =3.23
3
2
10
10
06
06
, XHI,IGM =0.30
, XHI,IGM =0.26
1
0
1
1200
1205
1210
0
1215
1220
Recovered optical depth fit parameters
XHI,IGM = 0.3
5.35
5.40
log(XHI,in)
5.45
5.50
5.55
5.60
5.65
0.40
5.70
0.15
XHI,IGM
0.30
0.25
0.20
40.40
0.25
0.30
XHI,IGM
0.35
0.15
40.35
0.20
40.45
40.50
RHII
40.55
40.60
0.35
0.40
Recovered IGM neutral fraction values
XHI,IGM = 0.3
5
N (objects)
4
3
2
1
0
0.15
0.20
0.25
0.30
XHI,IGM
0.35
0.40
Recovered IGM neutral fraction values
XHI,IGM = 0.04
16
N (objects)
14
12
10
8
6
4
2
0
0.00
0.05
0.10
0.15
0.20
0.25
0.30
XHI,IGM
9
8
N (objects)
7
6
5
4
3
2
1
0
2.2
2.0
1.8
1.6
1.4
1.2
log(XHI,IGM)
1.0
0.8
0.6
0.4
Recovered optical depth fit parameters
XHI,IGM = 0.04
5.40
5.45
log(XHI,in)
5.50
5.55
5.60
5.65
5.70
5.75
0.30
5.80
0.00
0.10
0.15
XHI,IGM
0.25
0.20
XHI,IGM
0.05
0.15
0.10
0.05
0.00
40.2 40.4 40.6 40.8 41.0 41.2 41.4 41.6 41.8
RHII
0.20
0.25
0.30
Future directions
We will:
simulate realistic high-z spectra (including density fluctuations) and
neutral fraction measurement procedures,
investigate correlations between line profile parameters and luminosity and look for trends with redshift,
explore improved line-profile models, perhaps including constraints
from correlations between line components or other lines.
Summary
We are assembling a catalog of spectra of low-redshift quasar Lymanalpha emission line profiles.
Line profile fitting uncertainties affect the measurement of the IGM
neutral fraction from the damping wing.
For XHI,IGM ∼ 0.3
the scatter induced by line-profile uncertainties ∼ 25%.
For XHI,IGM ∼ 0.04
the scatter induced by line-profile uncertainties ∼ 0.2 dex,
but with some very large overestimates.
Acknowledgments
Andrei Mesinger
Josh Schroeder
David Schiminovich
Multimission Archive at the Space Telescope Science Institute (MAST)
NASA/IPAC Extragalactic Database (NED)
The Perl Data Language (PDL)
levmar
SciPy + NumPy
OpenOpt