THE LAST SURVEY OF THE ‘OLD’ WSRT: DISCOVERING HI ABSORPTION IN LOW POWER RADIO SOURCES

F. Maccagni; R. Morganti; T. Oosterloo; K. Geréb; N. Maddox, J. Allison

ASSOCIATED HI ABSORPTION

[Struve, et al., 2012]

‣ ~ 40% of early-type galaxies have HI: ATLAS3D [Serra et. al 2012]

‣ Early-type galaxies are the typical host of a radio-AGN.

‣ In radio-AGN is possible to detect HI in absorption against the radio continuum.

‣ Detection of absorption is independent of redshift (if the background continuum is strong enough).

‣ HI absorption studies can be carried out in a shallow survey, with a few hours of exposure time per object.

‣ Absorption allows us to study the HI content of galaxies to high redshifts (z<1).

‣ HI absorption studies are complementary to HI emission studies.

HI ABSORPTION IN RADIO AGN‣ HI absorption can trace positive feedback between the

radio source and the host galaxy.

‣ Shallow blue shifted wings in the absorption line often trace outflows of cold gas pushed by the radio jet.

‣ The HI has the same kinematics as the other molecular cold gas components (e.g. CO, H2, etc).

‣ Study feedback between AGN and cold gas.4C +12.50

[Morganti et al. 2013]

THE LAST SURVEY OF THE OLD WESTERBORK ‣ 248 sources

‣ 0.02 < z < 0.25

‣ SDSS spectroscopy

‣ SCont ≥ 30 mJy

‣ Wide range of Radio Powers

‣ mostly AGN in early-type galaxies

‣ Two separate Data Releases:

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., submitted]

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

CHARACTERISATION OF THE SAMPLE

‣ WISE MIR colours characterise the host galaxy of the radio-AGN.

‣ 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

CHARACTERISATION OF THE SAMPLE

‣ 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.

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

DETECTING HI ABSORPTION

‣ Observe all sources with flux > 30 mJy and available SDSS spectrum.

‣ Bulk of the radio population is at low fluxes [Mauch & Sadler 2007]

‣ Detection of HI absorption at all redshifts.

‣ Shallow survey: mostly limited to high optical depths (𝝉~ 0.05-0.1)

‣ We also detect lines with very shallow peak (𝝉<0.007)

30 50 100 200 400 1000 2000S1.4GHz [mJy]

0

5

10

15

20

25

30

35

40

Cou

nt

All sources

Detections

0.001 0.005 0.020 0.100 0.300⌧

0

10

20

30

40

Cou

nt

All sources

Detections

DETECTING HI ABSORPTION

‣ 248 sources / 66 Detections

‣ 27 % ± 5.5 % detection rate

‣ We detect HI absorption at all redshifts and at all radio powers.

‣ Detection of HI constant with z, and radio power.

‣ Compact sources, 4.6 µm-bright and 12 µm-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

[%]

HI ABSORPTION LINES‣ 66 detections

‣ line properties 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

INTERPRETING HI ABSORPTION

3C 305

Plane of the sky : x,y Side view: z,y From above: x,z

Observation Model

• Understand the overall distribution of the HI traced by the absorption line • Narrow lines at the systemic velocity usually identify a rotating disk • What to can we infer from only the integrated line and the continuum image? • Help of a kinematical model:

• Model the rotating HI disk in front of the radio continuum:

INTERPRETING HI ABSORPTION

Parameters of the disk

‣ We fix the parameters of the disk from available information on the galaxy:

‣ Optical Image: i, PA ‣ Continuum image ‣ Tully Fisher -> Vflat

‣ We find which disk best reproduces the line

‣ The bulk of the absorption is well reproduced by a rotating disk

‣ Blue-shifted wing not reproduced by the model

INTERPRETING HI ABSORPTION

!!! Work in Progress‣ MCMC wrap: investigate the parameter space of I &

PA automatically

‣ find which combination best reproduces the line

‣ Future applications:

‣ can we reproduce the observed distributions of properties of the lines (e.g. FWHM , tau) by simulating 10N disks?

‣ investigate the degeneracy between parameters of the disk.

‣ understand when orientation effects between the host galaxy and the radio continuum play a role in detecting HI absorption.

�600 �400 �200 0 200 400 600

�0.0020

�0.0015

�0.0010

�0.0005

0.0000

0.0005

0.0010

Flu

x[J

y]

Spectrum

WSRT

model

rin (max) = 1500.0 pc

rin (min) = 0.0 pc

hin = 50.0 pc

pain = 50.0 �

iin = 30.0 �

rout (max) = 0.0 pc

rout (min) = 0.0 pc

hout = 0.0 pc

paout = 0.0 �

iout = 0.0 �

v (rot) = 229.0 km s�1

pa (cont) = 0.0 �

med res = 0.0 Jy

disp res = 0.0 Jy

Disk parameters

�600 �400 �200 0 200 400 600Velocity [km s�1]

�0.0020�0.0015�0.0010�0.0005

0.00000.00050.0010

WSRT

residuals

�1500�1000�500 0 500 1000 1500x [kpc]

�1500

�1000

�500

0

500

1000

1500

y[k

pc]

Plane of the sky

�1500�1000�500 0 500 1000 1500x [kpc]

�1500

�1000

�500

0

500

1000

1500

z[k

pc]

View from ‘above‘

�1500�1000�500 0 500 1000 1500z [kpc]

�1500

�1000

�500

0

500

1000

1500

y[k

pc]

View from ‘the side‘

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 ‣ lines have widths ≤ rotational

velocity of the galaxy. ‣ the HI is probably settled in a

rotating disk. ‣ P1.4GHz> 1024 W Hz-1

‣ we detect broad lines. ‣ the HI has unsettled kinematics.

‣ Sources with broad lines are: ‣ Compact, i.e. jets within the galaxy. ‣ MIR bright, i.e. rich in heated dust.

KINEMATICS OF THE HI

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 are centred at the systemic

velocity ‣ P1.4GHz> 1024 W Hz-1

‣ lines are offset w.r.t. systemic velocity ‣ the offset is mainly in blue-shifted

velocities. ‣ Sources with asymmetric, shifted lines are:

‣ Compact, i.e. jets within the galaxy. ‣ MIR bright, i.e. rich in heated dust.

‣ Dust-poor sources ‣ lines are narrow, mainly centred at the

systemic velocity. ‣ Typical signature of a rotating disk.

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 experiment to search for HI absorption at very-low optical depths.

‣ 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 ]

‣ Stacking of 81 ATLAS3D sources where the HI is non detected in the centre.

‣ 3𝛔 detection of an HI emission line

‣ N(HI) ~ 7.7 x 1018 cm-2

‣ On average, early-type galaxies have HI at very low column densities in the centre.

‣ The low column density HI we find from stacking may be present also in the stronger radio sources of our sample.

‣ N(HI) converted in optical depth (Tspin~100 K)

‣ 𝝉~ 0.0006 << 0.0015

‣ we need to stack more to detect this gas in absorption.

‣ N(HI) < 2x1020 cm-2 if Tspin > 600 K.

‣ The HI we see stacking ATLAS 3D may be warm!

‣ Tspin ↑ ⇒ 𝝉 ↓ ; Tspin ↓ ⇒ 𝝉 ↑

‣ Stacking in absorption even more difficult if Tspin ~ 103 K.

THE UPCOMING HI ABSORPTION SURVEYS‣ HI absorption surveys with the SKA

pathfinders and precursors

‣ SHARP at Apertif

‣ MALS at MeerKAT

‣ FLASH at ASKAP

‣ WALLABY: absorption at low redshift “for free”.

‣ From the continuum source population and our detection rate (27%) we predict what these surveys will detect for HI absorption

‣ The surveys are complementary to investigate the HI content in sources of radio power between 1022 and 1027 W Hz-1

‣ SHARP (and WALLABY) will allow us to detect HI absorption in low-power radio sources.

THE UPCOMING HI ABSORPTION SURVEYS‣ All surveys will detect all the different

kinds of HI absorption lines

‣ High optical depth (>0.1)

‣ Intermediate optical depth (0.02)

‣ Low optical depth (> 0.002)

‣ typical signatures of outflows.

‣ Only SHARP and WALLABY will be able to detect low optical depth HI lines (𝝉 > 0.002) in low power sources (P1.4GHz ~ 1024 W Hz-1)

CONCLUSIONS

‣ 27%±5.5% detection rate of HI in absorption

‣ HI detected at all redshifts (0.02 < z < 0.23) and radio powers

‣ AGN with radio power < 1024 W Hz-1 only show narrow lines. AGN with P1.4GHz>1024 W Hz-1 show broad lines which can trace HI with unsettled kinematics

‣ Broad lines are found in compact, i.e. often young, radio AGN, and in MIR-bright sources.

‣ Dust poor sources only show narrow lines.

‣ Stacking experiment suggests a low optical depth HI component is present in the centre of non-detections. This gas may be warmer than the one detected by single observations.

‣ Upcoming HI absorption surveys are complementary. We will be able to investigate the HI content in radio sources of all radio powers (1022 - 1026 W Hz-1), out to z~1.

ADVERTISEMENT‣ HI absorption with the new radio telescopes

‣ WORKSHOP at ASTRON

‣ 14 -16 June 2017‣ status of the telescopes and data

available for early science;

‣ planning for HI absorption surveys;

‣ experience built in the last years and tools available for the handling and analysis of new data;

‣ follow-up and ancillary data: molecular gas, optical identifications, high resolution radio data;

‣ requirements and possibilities for comparison with numerical simulations.

SOC: Raffaella Morganti Elaine Sadler

Tom Oosterloo James Allison Neeraj Gupta

credits: V. Moss

KINEMATICS OF THE HI

0.001 0.005 0.020 0.100 0.500⌧

05

1015202530 Distribution of the 3–� detection limits

Interacting sources

12µm bright sources

4.6µm bright sources

Dust-poor sources

0.001 0.005 0.020 0.100 0.500⌧

0

200

400

600

800FW

20[k

ms�

1 ]Peak optical depth vs. width of the lines

‣ Dust-poor sources ‣ lines are narrow. ‣ lines have high optical depth. ‣ Typical signature of a rotating disk.

‣ MIR bright sources ‣ lines can be shallow and broad, if P1.4GHz> 1024 W Hz-1 ‣ lines can also be asymmetric because they have a blue-shifted wing

‣ In powerful radio sources the jets may unsettle the HI.

‣ via outflows pushed by the radio jets

‣ ⇒ blue shifted wing in the

absorption line

SURVEY STRATEGY‣ 247 observations pointed at the radio source:

‣ Radio continuum + data cube

�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]

�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]

Detection

Non Detection

‣ 1 serendipitous detection of a field source

‣ promising result for the upcoming Apertif-Sharp and ASKAP-FLASH surveys, which will search for HI absorption in every source of the field.

beam

Extract spectrum against central source