Slides of the presentation I gave at the colloquium of the institute for astronomy at Stockholm University for my birthday.

1. Deciphering Lyman α emitting galaxies with
integral field spectroscopy
Edmund Christian Herenz
Stockholm University
June 14, 2019

2. Motivation: Understanding galaxy formation via direct
observations of the early universe.
λobs. = λ0 · (1 + z)

3. Hydrogen Lyα emission (λ1216 ˚A):
A praise for studies of the high-z universe.
“Back of the envelope” argument:
SFR[M yr−1
] ≈ 10−53 ˙Nγ(hν ≥ 13.6eV)[s−1
]
Hydrogen recombination cascade → Lyα is the strongest line:
P(hν ≥ 13.6eV → Lyα) = 0.68
Thus:
LLyα[erg s−1
] ≈ 1042
× SFR[M yr−1
]
In 737 “concordance cosmology” this means:
FLyα[erg s−1
cm−2
] = {1.3 × 10−16
, 3.8 × 10−17
, 1.8 × 10−17
}
at z = {3, 5, 7}
(λobs
Lyα = {4864, 7296, 9728} ˚A)

4. Partridge & Peebles 1967:
Are young galaxies visible?

5. Pioneering high-z LAE searches provided null results
Review by Pritchet 1994 - only upper limits on Lyα emitter
luminosity function:
Some campaings reported ∼ 1 − 3 possible high-z LAE
candidates, but not at the expected number densities.

6. First confirmed high-z (z = 4) detection
Hu & McMahon 1996: 2.2m telescope (imaging), Keck 10m (spectroscopy)

7. Statistical studies of high-z LAE population
Ouchi+2008 (Subaru)

8. Lyα is resonant...
Absorption cross-section of Hydrogen for Lyα photons:
σLyα = σ0 × φ(ν)
with σ0 = 5.88 × 10−14 × T[104K] cm2 and φ(ν) being a Voigt
profile:
Typical ISM: nHI = 1cm−3 →
NHI = 1014cm−2 (i.e. τ0 = 1)
after 10−5pc (2 AU).
Complex radiative transfer
problem, “random walk” of Lyα
photons → spatial & spectral
diffusion.
Increased path length: Lyα
photons succeptible for
being absorbed by dust.

9. Large number of Lyα scatterings in ISM!
Analytical solution for “homogeneous slab” (Harrington 1979):
Nscat = 1.612τ0
Figure from Laursen+2009.

10. Spectral Lyα Diffusion - Analytically
Emergent line profile from “homogenous slab”
(Harrington 1973, Neufeld 1991):
J(±τ0, x) =
√
6
24
x2
√
πaτ0
1
cosh π3/54(x3 − x3
inj)/aτ0
Maxima xm = ±1.066 × (aτ0)1/3
(Figure from Laursen+2009)

11. Spectral Lyα diffusion - Numerically
Verhamme+2006, Schaerer+2011
“shell modell” - (Parameters: NH, vexp, τdust)

12. Observed Lyα profiles often agree with the “shell
modell”
Examples from Gronke (2017) from fits to MUSE-Wide survey
LAEs (Herenz et al. 2017).
However, physical meaning of derived shell-model parameters
(NH, vexp, τdust) unclear.

13. Lyα profiles from different simplified geometry -
rotation & outflows
Remolina-Guti´errez & Forero-Romero 2019

14. Scattering: Spatial Diffusion → Lyα halos.
Radiative transfer post-processing of a single galaxy by
Verhamme+2012 (computationally expensive)

15. Model of Lyα haloes at high-z
Smith+2019, Lyα radiative transfer post-processing of
M ∼ 108M simulated galaxy

16. Lyα halos observed at low-z (HST WFC3), ...
Lyman Alpha Reference Sample
(e.g. Hayes+2014, Herenz+2016, Bridge+2018)
Mrk259 – 17 kpc × 15 kpc – Lyα, Hα, UV cont. – ¨Ostlin+2014

17. ... and at high-z (thanks to MUSE).
Every Lyα emitting galaxy is surrounded by a faint low-SB Lyα
halo (Wisotzki+2015, Leclerq+2017).
Halos typically contain 10% - 50% of the total Lyα flux!

18. Selection of unknowns in the Lyα universe...
What regulates the Lyα escape in galaxies (star-formation,
dust content, and/or gas kinematics)?
Are there possible biases in our inventory of high-z LAE
population?
What is the nature of the most luminous and extended Lyα
emitters at high-z?
Insights into these issues from integral field spectroscopic
observations...

19. Integral Field Spectroscopy
Potsdam Multi Aperture
Spectrophotometer @ Calar
Alto 3.5m Telescope
Multi Unit Spectroscopic
Explorer @ ESO’s VLT UT4
“Yepun” (Cerro Paranal)

20. What regulates the Lyα
escape in galaxies
(star-formation, dust
content, and/or gas
kinematics)?

21. Lyα imaging of LARS galaxies
Cool, but missing kinematical information.

22. Spatial and spectral properties of the LARS galaxies
intrinsic Lyα through Hα intergral field spectroscopy.
PMAS at Calar Alto 3.5m Telescope. Spectral range centered
on Hα.
(R1200 grating ⇒ R ∼ 5000, texp. ≈ 3 × 1800 s, mostly 16 ×16 FoV, seeing
∼ 1 )
1. Can we relate local “features” in Lyα flux to kinematical
features?
2. Do we see global trends between HII kinematics and Lyα
properties?
Results published in Herenz+2016.

23. Connection between local Hα kinematics and Lyα flux.
Example: LARS 1.
HST Hα → 13h28m44.5s 44.0s 43.5s 43.0s
43°55'55"
50"
45"
40"
0 2 4 6 8 10 12 14
0
2
4
6
8
10
12
14
10
0
10
1
10
2
10
3
←PMAS Hα
0
10
20
30
40
50
60
70
80
90
FLyα[10−18ergs−1cm−2]
60
75
90
105
120
135
150
165
180
vFWHM[kms−1]
60
45
30
15
0
15
30
45
60
vLOS[kms−1]
HST Lyα Hα vFWHM Hα vrad

24. Connection between local Hα kinematics and Lyα flux.
Example: LARS 5.
HST Hα → 13h59m50.0s 49.5s 49.0s 48.5s
57°26'45"
40"
35"
0 1 2 3 4 5 6 7
0
1
2
3
4
5
6
7
10
0
10
1
10
2
10
3
←PMAS Hα
0
15
30
45
60
75
90
105
120
FLyα[10−18ergs−1cm−2]
25
50
75
100
125
150
175
200
225
vFWHM[kms−1]
40
30
20
10
0
10
20
30
40
vLOS[kms−1]
HST Lyα Hα vFWHM Hα vrad

25. Can we relate “features” in Lyα flux to Hα kinematics?
Yes.
In some galaxies.
Consistent with the idea that
star-formation driven winds /
outflows promote Lyα escape
along some sightlines.
Radiative transfer sim. for
LARS 5
(Duval+ 2016)

26. Global kinematical statistics of LARS Hα velocity fields
via non-parametric esitmators: vshear, σ0 & vshear/σ0.
vshear: Measure for large-scale bulk motion along the line of
sight:
vshear =
1
2
(vmax − vmin)
σ0: Intrinsic velocity dispersion
σ0 =
FHα
bin σbin
FHα
bin
Ratio: vshear/σ0 - at high-z numerous galaxies with
vshear/σ0 < 1 (dispersion dominated)

27. Dispersion dominated systems are preferentially Lyα
emitters

28. Turbulent kinematics not always result in observable
Lyα...
LARS HST color-composites of Haro 11 and SBS 0335-052E
(low-z starbursts, ¨Ostlin+2009).

29. ... as line-of-sight effects may be important.
MUSE observations of SBS 0335-052E
Ionised cavities perpendicular to the line-of-sight may promote
Lyα (and possibly LyC) radiation.
Herenz+2017

30. Summary of LARS-PMAS results
Kinematic feedback appears to be an important ingredient
in driving Lyα escape.
Systems dominated by turbulent gas-kinematics are
preferentially Lyα emitters (currently a small sample).
Line of sight effects can be significant, especially in
gas-rich systems.

31. Are there possible biases in our
inventory of high-z LAE
population?
(Lyα Luminosity Function)

32. Why do we care about the Lyα Luminosity Function?
dNLAE = φ(LLyα)dLLyαdV
Luminosity functions provide the gold standard for
summarising the changing demographics of galaxies with
cosmic look back time.
Essential physical mechanisms of galaxy formation and
evolution are “frozen-in” into the LF.
Substantial high-redshift galaxy samples:
Continuum Selection (≈LBGs)
Emission Line Selection (LAEs)
LFs connected via EWLyα distribution: P(MUV|EWLyα)

33. Yeah, right... But why should we really care?
High-z Lyα LF allows for constraints on the reionisation history
of the universe.
(Matthee+2015)
Exact imprint of xHI on the
LAE LF also depends on
clustering.
Nevertheless, a robust and
comparable baseline LF at
redshifts where the
universe is completely
ionised is required.

34. Lyα selection reveals continuum undetectable galaxy
population...
Connection UV LF Φ(MUV) ↔ Lyα LF Φ(LLyα)
Φ(LLyα) dLLyα ∝ dLLyα
Mmax
UV
Mmin
UV
dMUVΦ(MUV)P(LLyα|MUV)
(Dijkstra & Whyite 2012, Gronke+2015)
Faint end of LAE LF probes
deeper into UV LF than with
current and next generation
of instruments possible!
Direct detection of faint-end
cut-off of UV LF feasible?

35. The MUSE-Wide (MW) survey
Goal: Establishing a baseline of the bright end of the LAE LF.
Herenz et al. (2017) - 24 MUSE pointings - 237 LAEs
DR1: Urrutia et al. (2019) - 44 MUSE pointings - 479 LAEs

36. Emission line source detection with LSDCat
Line Source Detection
and Cataloguing Tool
(Herenz & Wisotzki 2017 -
ascl:1612:002)
Input
Flux Datacube
F
Associated
Variances σ2
3D Matched Filter
Spatial Filtering F' = F * Tspat.
Spectral Filtering F = F' * Tspec.~
F = F * T
~
Seeing PSF
Parameters
Spectral Line Template
Parameter vFWHM
Matched Filter
Output
Filtered
Datacube F
Propagated
Variances σ 2
~
~
Emission Line Source
Detection
Detection
Threshold
Intermediate Catalog
Source Parameterisation
Final Emission Line Catalog
Analysis
Threshold

37. MUSE-Wide LAE selection function fc(FLyα, λobs
Lyα) from
source insertion and recovery experiments
Artificial point sources:
3D Gaussian, FWHM(λ) as PSF, vFWHM = 250 km s−1
⇒ PSSF (point source selection function)
Flux rescaled MUSE-HDFS LAEs (degraded to
MUSE-Wide PSF)
⇒ RSSF (real source selection function)
4990 5000 5010
0.0
2.5
5.0
7.5
10.0
12.5
15.0
σλ[10−20ergs−1cm−2Å]
5000Å
6860 6870
0.0
2.5
5.0
7.5
10.0
12.5
15.0
σλ[10−20ergs−1cm−2Å]
6861.25Å
7090 7100 7110
0.0
2.5
5.0
7.5
10.0
12.5
15.0
σλ[10−20ergs−1cm−2Å]
7100Å
7240 7250
0.0
2.5
5.0
7.5
10.0
12.5
15.0
σλ[10−20ergs−1cm−2Å]
7242.5Å
8290 8300
0
5
10
15
20
σλ[10−20ergs−1cm−2Å]
8295Å
5000 6000 7000 8000 9000
λ[Å]
0
10
20
30
σλ[10−20ergs−1cm−2Å]

38. Final selection functions
Lyα haloes → smoother gradient from 0 - 100% completeness.
5000 6000 7000 8000 9000
λ[Å]
17.6
17.4
17.2
17.0
16.8
16.6
16.4
16.2
16.0
log(F[ergs−1cm−2])
Realistic LAEs
5000 6000 7000 8000 9000
λ[Å]
17.6
17.4
17.2
17.0
16.8
16.6
16.4
16.2
16.0
Point Source LAEs
0.0
0.2
0.4
0.6
0.8
1.0
fc
3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5
zLyα
41.5
42.0
42.5
43.0
43.5
44.0
log(LLyα[ergs−1])
Realistic LAEs
3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5
zLyα
41.5
42.0
42.5
43.0
43.5
44.0
Point Source LAEs
0.0
0.2
0.4
0.6
0.8
1.0
fc

39. Bias in LAE LF when not accounting for Lyα haloes!
ΦRSSF(log LLyα = 42.2) = 2.5 × ΦPSSF(log LLyα = 42.2)
10-6
10-5
10-4
10-3
10-2
Φ(LLyα)[Mpc−3]
ΦC− (RSSF)
ΦC− (PSSF)
ΦC− (RSSF)
ΦC− (PSSF)
42.2 42.4 42.6 42.8 43.0 43.2
log10(LLyα[ergs−1])
0
50
100
ΦRSSF−ΦPSSF
ΦPSSF
[%]
relative difference: ΦRSSF − ΦPSSF
ΦPSSF

40. Comparison to literature
41.5 42.0 42.5 43.0 43.5
log10(LLyα[ergs−1])
10-5
10-4
10-3
10-2
φ(LLyα)[Mpc−3(∆log10LLyα[ergs−1])−1]
3<z 4
M17z=3.1
C11z∼ 3− 4
O08z∼ 3
G09z∼ 3
S18z∼ 3.1
MW3<z 4 (PSSF)
MW (AGN)
41.5 42.0 42.5 43.0 43.5
log10(LLyα[ergs−1])
10-5
10-4
10-3
10-2
φ(LLyα)[Mpc−3(∆log10LLyα[ergs−1])−1]
4<z 5
O08z∼ 4
D07z∼ 4
S09z∼ 4
P18z=4.8
S18z∼ 4.7
S18z∼ 3.9
MW4<z 5 (PSSF)
41.5 42.0 42.5 43.0 43.5
log10(LLyα[ergs−1])
10-5
10-4
10-3
10-2
φ(LLyα)[Mpc−3(∆log10LLyα[ergs−1])−1]
z>5
S18z∼ 5.4
C11z∼ 4.5− 6.5
K18z∼ 6
O08z∼ 6
S16z∼ 6
S06z∼ 6
MWz>5 (PSSF)
42.0 42.5 43.0 43.5 44.0
log10(LLyα[ergs−1])
10-5
10-4
10-3
10-2
φ(LLyα)[Mpc−3(∆log10LLyα[ergs−1])−1]
Global: 3<z<6.7
S18SC4K/noAGN
MW (RSSF)
MW (PSSF)

41. Summary of LAE LF results
(LLyα, z)-space probed by MUSE-Wide:
42.2 ≤ log LLyα[erg s−1
] ≤ 43.5 2.9 ≤ z ≤ 6.7
(Herenz+2017 sample: ω = 22.2 ˆ= V = 2.3 × 105 Mpc3)
Within this sampled region (LLyα, z)-space LAE LF.
appears non-evolving.
Schechter parameterisation provides good fit - Power law
not (see Paper).
log L∗
[erg s−1
] = 42.66+0.22
−0.16 α = −1.84+0.42
−0.42
log φ∗
[Mpc−3
] = −2.71
Literature LFs not accounting for extended low-SB Lyα
halos (basically all, except MUSE studies) are
significantly biased at L < L∗.

42. What is the nature of the
most luminous and
extended Lyα emitters at
high-z?

43. Lyα blobs (LABs)
Discovered by Steidel+2000 via Lyα imaging of a proto-cluster
region at z = 3.1. LLyα > 1043 . . . 1044 erg s−1, extend
100 kpc
What drives the Lyα luminosity?

44. LABs are rare, but more frequent in overdensities
(prot-cluster regions)
Erb+2011 blobs align with their major axis - “cosmic web”?

45. Possible powering mechansims
1. Photoionisation of obscured galaxies and/or AGN?
2. Cooling of shock-heated gas from driven via outflows from
buried galaxie(s)/AGN(s)?
3. Cooling of gravitationally heated gas (filamentary cooling
flows) falling into the halo?
Observations:
1. Sub-mm / radio continuum / X-Ray follow-up (or polarisation)
2. & 3. Line profile analysis / Emission-line diagnostics.

46. Possible evidence for a central engine in LAB 1 from
polarisation (Hayes+2011)
left: polarisation fraction – right: polarisation orientation
Later follow-up campaings with ALMA found [CII] emission
850µ continuum sources in the blob, that could provide the
required ˙Qion (Geach+2016, Umehata+2017, Ao+2017)
(SFRs ∼ 103M yr−1).

47. Problem solved - LAB 1 powered by photoionisation?
Situation is more challenging:
Only our sightline is obscured from the sources, but
perpendicular to our sightlines no obscuration?
What is feeding the imense star-formation? Cooling flows...
Newer models predict Lyα emmisivity from cooling flows
strongest close to the center of the halo.
Feedback from the extreme dusty star-burst is expected to
shock-heat the circum-galactic regions...

48. 17.5 hours of ESO / MUSE observations
3 ESO Programmes (PI Hayes (2×), Bower)
22h
17m
28s 27s
26s
25s
24s
23s
0°13'00"
12'40"
20"
00"
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
17.2
texp[h]

49. Slicing the Lyα blob in velocity space.
-3134 km/s4971.5Å -2517 km/s4974.0Å -1900 km/s4976.5Å -1284 km/s4979.0Å
-667 km/s4981.5Å -50 km/s4984.0Å 566 km/s4986.5Å 1183 km/s4989.0Å
1800 km/s4991.5Å 2416 km/s4994.0Å 3033 km/s4996.5Å 3650 km/s4999.0Å
0 2 4 6 8 10
FLyα [10−20 ergs−1cm−2]

50. S/N Map of the Lyα blob
22h
17m
28s
27s
26s
25s
24s
0°13'00"
12'45"
30"
15"
00"
4
10
15
30
50
20
40
60
80
100
120
LSDCatS/Nmax
Detection of shell-like feature in SW, four new LAEs neighbours,
and multiple distinct emission peaks (individual galaxies?).

51. Optimally extracted narrow-band image
22h
17m
28.0s
27.0s
26.0s
25.0s
24.0s
0°13'00.0"
12'45.0"
30.0"
15.0"
00.0" 0
20
40
60
80
100
FLyα[10−20ergs−1cm2]
Detection of shell-like feature in SW, four new LAEs neighbours,
and multiple distinct emission peaks (individual galaxies?).

52. Complex Lyα line profiles everywhere
4960 4980 5000
0
50
100
s=0.99
b=2.91
=3.89
4
4960 4980 5000
0
50
100
150
s= − 0.03
b=2.39
=2.39
6
4960 4980 5000
0
100
200
300
400
500
s= − 0.31
b=3.06
=3.16
7
4960 4980 5000
0
50
100
150
200
250 s= − 0.02
b=3.22
=3.22
8
4960 4980 5000
0
100
200
s= − 0.32
b=2.65
=2.76
3
4960 4980 5000
25
0
25
50
75
100s= − 0.85
b=2.53
=3.26
9
4960 4980 5000
0
50
100
s= − 0.34
b=3.01
=3.13
2
4960 4980 5000
0
50
100
150
200
s=0.11
b=2.81
=2.82
10
4960 4980 5000
0
50
100
150 s= − 0.2
b=2.4
=2.44
1
4960 4980 5000
0
200
400
600
800 s=0.14
b=2.73
=2.75
13
4960 4980 5000
0
50
100
150
200 s=0.02
b=2.31
=2.31
12
4960 4980 5000
0
100
200
s= − 0.24
b=2.58
=2.64
11

53. Mapping the Lyα profile characteristics via
non-parametric statistics
“Line of sight velocity” & line width (first & second moment).
2000
1000
0
1000
2000
v1[kms−1]
0
100
200
300
400
500
600
σ=v2[kms−1]

54. Higher moment based stastics
Skewness
1.00
0.75
0.50
0.25
0.00
0.25
0.50
0.75
1.00
s
Kurtosis
2.0
2.5
3.0
3.5
4.0
Bimodality
1.5
2.0
2.5
3.0
3.5
b
WIP Interpretation: Signatures of feedback close to the known
sources, while more quiescent gas in the outer parts.

55. Finally: Detection of HeII λ1640 emission
Maybe shocks?

56. 1630 1640 1650
λ0(z=3.1) [Å]
2000 1000 0 1000 2000
∆v(z=3.1) [kms−1]
0
25
50
75
100
Fλ[10−20ergs−1Å−1]
south Lyα/10
1630 1640 1650
λ0(z=3.1) [Å]
2000 1000 0 1000 2000
∆v(z=3.1) [kms−1]
0
25
50
75
100
north Lyα/5
1630 1640 1650
λ0(z=3.1) [Å]
2000 1000 0 1000 2000
∆v(z=3.1) [kms−1]
0
25
50
75
100
LAB8 Lyα/5

57. Summary for LAB 1 MUSE Observations
MUSE offers an unprecedented view at LAB 1
Multiple photometric peaks hint at multiple galaxies within
the blob.
Possible evidence for shock-heated gas near the main
star-bursts.
Filamentary morphology and quiescent Lyα line in the
outskirts reminiscent of cooling flows.
Being in a proto-cluster, this system is a likely progenitor of
a giant eliptical (if not a BCG) of local universe clusters.

58. Thank you for your attention!