Institute
Galaxies
for Astronomy
in Absorption,
Colloquium,
Marseille,
13th
3rdNovember
Dec 2013 2013
Probing the Circumgalactic Medium with
Composite Spectra of the Lyman-alpha
Forest Absorbers
Mat Pieri
with Michael Mortonson, Stephan Frank, Neil Crighton,
David Weinberg, Nicolás Busca, Jim Rich, Timothée Delubac,
Stephen Bailey, KG Lee, Andreu Font, David Kirkby,
Anze Slosar & the BOSS LyαF and Quasar working groups
Friday, December 6, 13
Galaxies in Absorption, Marseille, 3rd Dec 2013
The Circumgalactic Medium: Inflow and
Outflow Caught in the Act
The challenge:
At low redshift (z<2) large surveys of galaxies are possible but
the IGM is difficult to probe
At high redshift (z>2) the IGM is well measured but galaxies
are hard to survey
So the Circumgalactic Medium is hard to study in detail at all
epochs
Friday, December 6, 13
Galaxies in Absorption, Marseille, 3rd Dec 2013
Weak, Distributed Signal of Metal Absorption
The Lyman α forest with a weak O VI forest
Distributed signal of weak absorption (e.g. Cowie & Songaila
1998, Schaye et al 2003)
UV background shape with
COS data (Frank, MP et al. in
prep)
log OVI
apparent
opacity
Volume enriched (MP &
Haehnelt 2004)
log Lyα opacity
log IGM density
Friday, December 6, 13
Galaxies in Absorption, Marseille, 3rd Dec 2013
Weak, Distributed Signal of Metal Absorption
log Lyα opacity
log IGM density
Calibrated O VI
Flux
log C IV
apparent
opacity
Near and far from known galaxies (MP, Schaye & Aguirre 2006)
Measure cosmic metal
density in IGM with
SDSS (MP et al 2010a)
log Lyα opacity
log IGM density
Friday, December 6, 13
Galaxies in Absorption, Marseille, 3rd Dec 2013
Stacking Lyman α Forest Absorbers
Shift the whole spectrum to the restframe of the Lyman α forest
absorber of interest and stack to see any metals available
(MP et al. 2010b using SDSS II data)
Gives a composite spectrum of Lyman α forest absorbers
Friday, December 6, 13
Galaxies in Absorption, Marseille, 3rd Dec 2013
Stacking Lyman α Forest Absorbers
Shift the whole spectrum to the restframe of the Lyman α forest
absorber of interest and stack to see any metals available
(MP et al. 2010b using SDSS II data)
Gives a composite spectrum of Lyman α forest absorbers
Friday, December 6, 13
Galaxies in Absorption, Marseille, 3rd Dec 2013
Stacking Lyman α Forest Absorbers
Shift the whole spectrum to the restframe of the Lyman α forest
absorber of interest and stack to see any metals available
(MP et al. 2010b using SDSS II data)
Gives a composite spectrum of Lyman α forest absorbers
Friday, December 6, 13
Galaxies in Absorption, Marseille, 3rd Dec 2013
Stacking Lyman α Forest Absorbers
Shift the whole spectrum to the restframe of the Lyman α forest
absorber of interest and stack to see any metals available
(MP et al. 2010b using SDSS II data)
Gives a composite spectrum of Lyman α forest absorbers
Friday, December 6, 13
Galaxies in Absorption, Marseille, 3rd Dec 2013
SDSS-III/ BOSS
Measure correlated structure
between LOS
H(z)/(1+z) (km/sec/Mpc)
Expansion rate
Probing the expansion of the
universe!
90
80
Lyα
70
“cepheids”
galaxies
60
50
Friday, December 6, 13
0
1
2
z
The current forest survey (DR9):
3,275 deg2
60,369 quasars of 2.1 ≤ z ≤ 3.5
48,640 quasars after removal of
BAL & DLA
publicly available sample (Lee et
al. 2013)
7
Galaxies in Absorption, Marseille, 3rd Dec 2013
A Composite Spectrum of Lyman α Forest
Absorbers using BOSS DR9
Stacking Ly α
absorbers with
2.4<z<3.1
Many elements/
lines/species
essential for
physical conditions
of gas
abundance
patterns
UV background
shape, intensity
MP et al. , astro-ph/1309.6768
Friday, December 6, 13
Galaxies in Absorption, Marseille, 3rd Dec 2013
Composites released to the community
Friday, December 6, 13
MP et al. , astro-ph/1309.6768
Galaxies in Absorption, Marseille, 3rd Dec 2013
Its pretty but what does it mean?
Lots of information here
Need to:
Understand selection
Characterise composite metal absorption
Characterise scatter
Friday, December 6, 13
Galaxies in Absorption, Marseille, 3rd Dec 2013
Lyman α Selection: Simulations
BOSS with noise
BOSS no noise
Perfect data
Probes blending at SDSS Resolution
MP et al. , astro-ph/1309.6768
Friday, December 6, 13
Galaxies in Absorption, Marseille, 3rd Dec 2013
Lyman α Selection: Proximity to Galaxies
Lyman break galaxies surveyed near high quality quasar spectra.
Test by matching Ly-α selection requirements.
Fraction of absorbers with a
galaxy within 300 proper kpc
transverse and +- 300 km/s
along line-of-sight
From VLT LBG survey (Beilby et
al., 2011),VLT/FORS2 survey
(Crighton in prep), a subset of
KBSS (Rudie et al. 2012)
MP et al. , astro-ph/1309.6768
Friday, December 6, 13
Galaxies in Absorption, Marseille, 3rd Dec 2013
Lyman α Selection: Proximity to Galaxies
F<0.25 is associated with CGM ~60% of the time (noise free)
With noise, purity of F< 0.25 selection is 90%, 79% and 49%
in strongest 3 Lyα absorption bins
So LBG CGM purity of ~50% in two strongest bins
~18k+ galaxies
Note choice of 300 kpc and +- 300 km/s comes from Rudie
et al. (2012) CGM working definition
Rahmati et al (2013) sims show fainter dwarf galaxies closer
to the LOS dominate this CGM definition
Friday, December 6, 13
Galaxies in Absorption, Marseille, 3rd Dec 2013
Lyman α Selection: HI Column Density
Measured from
Lyman series in the
composite spectra
Friday, December 6, 13
Measured from the
Lyman limit in
modified stacks
Galaxies in Absorption, Marseille, 3rd Dec 2013
Measured
Lyman
series
Friday, December 6, 13
Measured Lyman
limit and
Galaxies in Absorption, Marseille, 3rd Dec 2013
Lyman α Selection: HI Column Density
7 Lyman series lines and opacity to ionizing photons (Lyman limit)
MP et al. , astro-ph/1309.6768
Friday, December 6, 13
Galaxies in Absorption, Marseille, 3rd Dec 2013
Metal Columns
Flux selected
Column
density
Friday, December 6, 13
Galaxies in Absorption, Marseille, 3rd Dec 2013
Metal Line Profiles
Line width probes structure and metal complexes
Mean flux decrement as low as ~0.3% (F=0.997)
MP et al. , astro-ph/1309.6768
Friday, December 6, 13
Galaxies in Absorption, Marseille, 3rd Dec 2013
Compared with Models
Column
density
Lower ionization potential
MP et al. , astro-ph/1309.6768
Friday, December 6, 13
Galaxies in Absorption, Marseille, 3rd Dec 2013
Compared with
Models
Column
density
Lower ionization potential
Friday, December 6, 13
Galaxies in Absorption, Marseille, 3rd Dec 2013
Compared with Models
Column
density
Lower ionization potential
MP et al. , astro-ph/1309.6768
Friday, December 6, 13
Galaxies in Absorption, Marseille, 3rd Dec 2013
Other results
Various studies showing sub-kpc clumping (e.g. high-z: Simcoe
et al. 2006, Schaye et al. 2007, low-z: Tripp et al 2002, Lehner
et al 2013)
Lehner et al. (2013) find interesting bimodal metallicity in low
-z analogues
would look a lot like our results if stacked
Friday, December 6, 13
Galaxies in Absorption, Marseille, 3rd Dec 2013
Lots to explore
Abundance patterns
[C/↵] & 1 (possible source explosions of Pop III stars)
[↵/Fe] ⇠ 0 (suggestive of significant Type Ia SN contribution)
UV background shape and intensity (star formation rate, quasar
duty cycles, IGM evolution and uncertainty)
Metallicity and physical conditions (feedback properties)
Line breadth (metal clustering/complexes)
MP et al. , astro-ph/1309.6768
Friday, December 6, 13
Galaxies in Absorption, Marseille, 3rd Dec 2013
Measurement of associated structure
From
DR11
Friday, December 6, 13
Galaxies in Absorption, Marseille, 3rd Dec 2013
IGM-Galaxies Coevolution - Summary
Stacking the BOSS Lyman α forest data set - better than
0.5% absorption measurements of the metals
Circumgalactic regions stacked with ~50% purity
Find ~30 pc scale clumping and ~solar metallicity
Wealth of detail to explore
To do:
Compare with simulations (Mortonson et al. to come)
Explore absorbing populations sizes
Multi-parameter interpretation
Explore metal contamination of cosmology
Friday, December 6, 13
Galaxies in Absorption, Marseille, 3rd Dec 2013
Future Growth of Quasar Surveys
Next year: full BOSS with 3xDR9 forest quasars
Followed by eBOSS with more forest quasars
eBOSS will add low-redshift quasar clustering
Some forest data, but I propose to use metal absorption to
measure BAO ...
DESI and WEAVE will provide 0.3-0.5M LyαF quasars from
~2017
I am the Quasar Absorption Survey lead for WEAVE
R~ 20000 survey with limited wavelength coverage (great
for z~2.5. forest data)
Friday, December 6, 13