THE LAST SURVEY OF THE ‘OLD’ WSRT: TOOLS AND RESULTS FOR THE FUTURE HI ABSORPTION SURVEYS
F. Maccagni; R. Morganti; T. Oosterloo; K. Geréb; N. Maddox, J. Allison
A SURVEY BEFORE THE ‘BLIND’ SURVEYS
‣ During my PhD, WSRT was upgraded to Apertif: over time antennae went offline
‣ To detect HI absorption we don’t need complete uv-coverage
‣ Great opportunity for HI absorption studies
‣ Observe as many sources as possible before WSRT observations stop
‣ 4/6 hrs observation with variable number of antennae
‣ average noise in the spectra ~ 1 mJy
‣ Set strategy and tools for the ‘blind’ surveys: SHARP, MALS, FLASH
‣ What is the detection rate of HI in the local Universe?
‣ What features of the HI lines relate to the properties of the radio sources?
THE LAST SURVEY OF THE OLD WESTERBORK ‣ 248 sources
‣ 0.02 < z < 0.25
‣ SDSS spectroscopy
‣ SCont ≥ 30 mJy
‣ mostly AGN in ETG
1. 101 sources; SCont ≥ 50 mJy
‣ Stacking experiment [Geréb et al., 2014]
‣ Analysis of the detections [Geréb , Maccagni, et al., 2015]
2. All 248 sources
‣ This Talk [Maccagni et al., 2017]
39 40 41 42 43 44 45 46log10 L22µm [erg s�1]
18
19
20
21
22
23
24
25
26
log 1
0P
1.4G
Hz
[WH
z�1 ]
Jarrett et al. 2013
Dust-poor source
12µm bright source
4.6µm bright source
Interacting source
A3D Dust-poor source
A3D 12µm source
A3D 4.6µm source
ATLAS3D
This SAMPLE
Mid-InfraRed [22 µm] - Radio Power Relation
�10
�5
0
Flu
x[m
Jy]
1.326 1.328 1.330 1.332 1.334 1.336 1.338 1.340Frequency [⇥109 Hz]
0.81.01.21.41.6
Noi
se[m
Jy]
Detection
STRATEGY OF THE SURVEY
Continuum source finder: location continuum sources (down to 10mJy/
5mJy or even lower)
Similar to APERTIF observations Flagging and automatic calibration
Data Cube + Continuum Image
Identify HI absorption detections: Bayesian line-finder [Allison et al 2012]
Extract the spectra @ location continuum sources
beam
�4
�2
0
2
4
Flu
x[m
Jy]
1.306 1.308 1.310 1.312 1.314 1.316 1.318 1.320Frequency [⇥109 Hz]
0.81.01.21.41.61.8
Noi
se[m
Jy]
Non Detection
�10
�5
0
Flu
x[m
Jy]
1.326 1.328 1.330 1.332 1.334 1.336 1.338 1.340Frequency [⇥109 Hz]
0.81.01.21.41.6
Noi
se[m
Jy]
STRATEGY FOR HI ABSORPTION SURVEYS
Characterisation absorption (width, centre, asymmetry etc.
using e.g. busy function)
DATABASE
cross-correlation with LOFAR fields & other archives
(SDSS, WISE)
Intervening or associated?cross-correlation with spectral surveys
Detection �4
�2
0
2
4
Flu
x[m
Jy]
1.306 1.308 1.310 1.312 1.314 1.316 1.318 1.320Frequency [⇥109 Hz]
0.81.01.21.41.61.8
Noi
se[m
Jy]
Non Detection
Properties of radio continuum (extent, spectral
index, …)
Properties of the HI lines
HI ABSORPTION LINES‣ 66 detections
‣ line features measured with the BusyFunction [Westmeier, et al. 2014]
‣ 30 < FWHM < 570 km/s
‣ 70 < FW20 < 640 km/s
‣ 3 main groups:
‣ Narrow lines:
FWHM < 100 km/s
‣ Medium width lines:
100 km/s <FWHM < 200 < km/s
‣ Broad lines:
FWHM > 200 km/s
CHARACTERISATION OF THE SAMPLE
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0FIRST peak / integrated flux
1.0
1.2
1.4
1.6
1.8
2.0
NV
SSm
ajor
/m
inor
axis
Extended non-detection
Compact non-detection
Extended detection
Compact detection
Interacting detection
Interacting non-detection
‣ Compact sources (red):
‣ unresolved by FIRST.
‣ often radio-jets on sub-galactic scales.
‣ many compact sources are young AGN.
‣ Extended sources (blue):
‣ resolved by FIRST.
‣ radio-jets on super-galactic scales.
‣ usually older AGN than compact sources.
CHARACTERISATION OF THE SAMPLE‣ WISE MIR colours
‣ dust in the host galaxy
‣ Dust-poor sources (green)
‣ 12 µm-bright sources (orange)
‣ Emission from PAHs and heated dust.
‣ 4.6 µm-bright sources (black)
‣ The central AGN heats the surrounding circumnuclear dust.
0.0 1.0 2.0 3.0 4.0 5.0W2 – W3 [4.6 - 12 µm]
0.0
0.5
1.0
1.5
W1
–W
2[3
.4-
4.6
µm
]
Dust-poor non-detection
12µm bright non-detection
4.6µm bright non-detection
Dust-poor detection
12µm bright detection
4.6µm bright detection
Interacting non-detection
Interacting detection
DETECTING HI ABSORPTION
‣ 248 sources / 66 Detections
‣ 27 % ± 5.5 % detection rate
‣ Constant in redshift and radio power
‣ Compact sources and MIR bright
‣ HI often detected (~40%).
‣ Extended sources & dust-poor sources
‣ HI is rarely detected (~13%).
0
5
10
15
20
25
Cou
nt
All sources
Detections
0.02 0.05 0.08 0.11 0.14 0.17 0.20 0.23z
0
20
40
60
80
Det
.R
ate
[%]
0
5
10
15
20
25
30
35
Cou
nt
All sources
Detections
23 24 25 26log10 P1.4GHz [W Hz�1]
0
20
40
60
80
Det
.R
ate
[%]
KINEMATICS OF THE HI
22 23 24 25 26log10 P1.4GHz [W Hz�1]
0
200
400
600
800
FW
20[k
ms�
1 ]
Interacting sources
Dust-poor sources
12µm bright sources
4.6µm bright sources
22 23 24 25 26log10 P1.4GHz [W Hz�1]
0
200
400
600
800
FW
20[k
ms�
1 ]
Interacting sources
Extended sources
Compact sources
‣ P1.4GHz< 1024 W Hz-1 ‣ widths ≤ rotational velocity ‣ HI likely in a rotating disk.
‣ P1.4GHz> 1024 W Hz-1
‣ broad asymmetric lines.
‣ Sources with broad lines are: ‣ Compact, i.e. jets within the galaxy. ‣ MIR bright, i.e. rich in heated dust.
22 23 24 25 26log10 P1.4GHz [W Hz�1]
�600
�400
�200
0
200
400
600
v cen
troi
d-
v sys
tem
ic[k
ms�
1 ]
Interacting sources
Extended sources
Compact sources
22 23 24 25 26log10 P1.4GHz [W Hz�1]
�600
�400
�200
0
200
400
600
v cen
troi
d-
v sys
tem
ic[k
ms�
1 ]
Interacting sources
Dust-poor sources
12µm bright sources
4.6µm bright sources
‣ P1.4GHz< 1024 W Hz-1
‣ lines centred at systemic velocity
‣ P1.4GHz> 1024 W Hz-1
‣ lines offset w.r.t. systemic velocity
‣ offset is blue-shifted.
‣ Broad, asymmetric, shifted absorption line
‣ Unsettled kinematics
‣ Powerful radio sources
‣ Compact, i.e. jets within the galaxy.
‣ MIR bright, i.e. rich in heated dust.
KINEMATICS OF THE HI
STACKING EXPERIMENT
�1500 �1000 �500 0 500 1000 1500Velocity [km s�1]
�0.002
0.000
0.002
0.004
0.006
⌧
Compact non-detections
Extended non-detections
�1500 �1000 �500 0 500 1000 1500Velocity [km s�1]
�0.002
0.000
0.002
0.004
0.006
⌧
12µm & 4.6µm-bright non-detections
Dust-poor non-detections
�1500 �1000 �500 0 500 1000 1500Velocity [km s�1]
�0.002
�0.001
0.000
0.001
0.002
0.003
⌧
Non Detections
‣ Non-detections are important!!!!
‣ Stacking of 170 non-detections
‣ NO LINE is detected at ~ 0.0015 (3𝛔)
‣ Stacking of sub-groups of sources
‣ NO LINE is detected at ~ 0.003 (3𝛔)
‣ Not even in compact sources or MIR bright sources.
STACKING THE ATLAS3D NON-DETECTIONS
�1000 �500 0 500 1000Velocity [km s�1]
�6
�4
�2
0
2
4
6
N(H
I)[⇥
1017
cm�
2bea
m�
1 ]
‣ 81 ATLAS3D sources HI is not detected in the centre.
‣ STACKING: 3𝛔 detection of HI emission
‣ N(HI) ~ 3.5 x 1017 (Tspin/cf) cm-2
‣ N(HI) converted in optical depth (Tspin~100 K, cf =1)
‣ 𝝉~ 0.0006 << 0.0015
‣ we need to stack more to detect this gas in absorption.
‣ The HI stacking ATLAS3D is warm?
‣ Tspin ↑ ⇒ 𝝉 ↓ ; Tspin ↓ ⇒ 𝝉 ↑
‣ Stacking in absorption even more difficult
INTERPRETING HI ABSORPTION
‣ Understand the overall distribution of the HI traced by the absorption line ‣ What to can we infer from only the integrated line and the continuum image? ‣ Model the rotating HI disk in front of the radio continuum:
3C 305
Plane of the sky : x,y Side view: z,y From above: x,z
Observation Model
INTERPRETING HI ABSORPTION ‣ 3C 305 ‣ Optical Image (SDSS or other): i, PA of the stellar body ‣ Continuum image: against which radio lobe there is absorption?
‣ i ∊ [0°,180°] ‣ PA ∊ [180°, 360°]
INTERPRETING HI ABSORPTION
247
495
742
989
1237
1484
Cou
nt
0 15 30 45 60 75I [�]
180
210
240
270
300
330
360
PA
[�]
180 210 240 270 300 330 360PA [�]
280
560
840
1119
1399
1679
1959
Cou
nt
‣ MCMC algorithm
‣ find combination of parameters that best fits the observed line the line
‣ i = 45°; PA = 270 °
‣ 3C 305 ‣ Optical Image (SDSS or other): i, PA of the stellar body ‣ Continuum image: against which radio lobe there is absorption?
‣ i ∊ [0°,180°] ‣ PA ∊ [180°, 360°]
INTERPRETING HI ABSORPTION ‣ The bulk of the absorption generated by a rotating disk: i = 45°; PA = 270 ° ‣ Blue-shifted wing not reproduced by the model
�1000 �500 0 500 1000Velocity [km s�1]
�0.010
�0.005
0.000
0.005
Flu
x[m
Jy]
Spectrum
observation
model
-1250 -1000 -750 -500 -250 0 250 500 750 1000 1250�0.004
�0.002
0.000
0.002
0.004
Flu
x[m
Jy]
resitudals
-4.0 -2.0 0.0 2.0 4.0x [kpc]
-4.0
-2.0
0.0
2.0
4.0
y[k
pc]
Plane of the sky
-4.0 -2.0 0.0 2.0 4.0x [kpc]
-4.0
-2.0
0.0
2.0
4.0
z[k
pc]
View from ‘above’
-4.0 -2.0 0.0 2.0 4.0z [kpc]
-4.0
-2.0
0.0
2.0
4.0
y[k
pc]
View from the ‘side’
INTERPRETING HI ABSORPTION
�1000 �500 0 500 1000Velocity [km s�1]
�0.0020
�0.0015
�0.0010
�0.0005
0.0000
0.0005
0.0010
Flu
x[m
Jy]
Spectrum
observation
model
-1250 -1000 -750 -500 -250 0 250 500 750 1000 1250�0.0010
�0.0005
0.0000
0.0005
Flu
x[m
Jy]
resitudals
-800.0 -400.0 0.0 400.0 800x [pc]
-800.0
-400.0
0.0
400.0
800
y[p
c]
Plane of the sky
-800.0 -400.0 0.0 400.0 800x [pc]
-800.0
-400.0
0.0
400.0
800
z[p
c]
View from ‘above’
-800.0 -400.0 0.0 400.0 800z [pc]
-800.0
-400.0
0.0
400.0
800
y[p
c]
View from the ‘side’
320
641
962
1282
1602
1923
Cou
nt
0 20 40 60 80 100 120 140 160 180I [�]
0
60
120
180
240
300
360
PA
[�]
0 60 120 180 240 300 360PA [�]
106.6
213.1
319.7
426.3
532.9
639.4
746.0
Cou
nt
‣ Less information on the source?
‣ i ∊ [0°,180°] ‣ PA ∊ [0°, 360°]
‣ Best-fit solution: i = 55°; PA = 240 °
‣ VLBI high resolution continuum ‣ Likely we can improve the fit
CONCLUSIONS
‣ 27%±5.5% detection rate of HI in absorption
‣ HI detected at all redshifts (0.02 < z < 0.23) and radio powers:
‣ promising for SHARP, MALS, FLASH
‣ Narrow lines
‣ HI mainly in a rotating disk
‣ P1.4GHz< 1024 W Hz-1, Extended sources, dust poor sources
‣ Broad asymmetric shifted lines:
‣ HI has unsettled kinematics
‣ P1.4GHz> 1024 W Hz-1, Compact sources (i.e. often young AGN), MIR bright sources
‣ Stacking experiments:
‣ low optical depth HI is present in the centre of ETGs, warmer HI (Tspin >100 K)?
�10
�5
0
Flu
x[m
Jy]
1.326 1.328 1.330 1.332 1.334 1.336 1.338 1.340Frequency [⇥109 Hz]
0.81.01.21.41.6
Noi
se[m
Jy]
BLIND SURVEYS: AUTOMATIC SEARCH FOR HI ABSORPTION
Characterisation absorption (width, centre, asymmetry etc.
e.g. busy function)
DATABASE
Stackingcross-correlation with LOFAR fields & other archives (SDSS, WISE)
other ideas...Comparison with models
Intervening or associated? cross-correlation with spectral surveys
Detection�4
�2
0
2
4
Flu
x[m
Jy]
1.306 1.308 1.310 1.312 1.314 1.316 1.318 1.320Frequency [⇥109 Hz]
0.81.01.21.41.61.8
Noi
se[m
Jy]
Non Detection
Line-finder: which one? Extract the spectra @ location of every
continuum source in the FOV
Properties of the HI lines
Properties of radio continuum
(size, spectral index, …)
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