THE LAST SURVEY OF THE OLD WSRT: TOOLS AND RESULTS FOR THE FUTURE HI ABSORPTION SURVEYS

Transcription

1 F. Maccagni; R. Morganti; T. Oosterloo; K. Geréb; N. Maddox, J. Allison THE LAST SURVEY OF THE OLD WSRT: TOOLS AND RESULTS FOR THE FUTURE HI ABSORPTION SURVEYS

2 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?

3 THE LAST SURVEY OF THE OLD WESTERBORK 248 sources.2 < z <.25 SDSS spectroscopy S Cont 3 mjy mostly AGN in ETG log 1 P1.4GHz [W Hz 1 ] Jarrett et al. 213 Dust-poor source 12µm bright source 4.6µm bright source Interacting source A3D Dust-poor source A3D 12µm source A3D 4.6µm source This SAMPLE sources; S Cont 5 mjy Stacking experiment [Geréb et al., 214] ATLAS 3D log 1 L 22µm [erg s 1 ] Analysis of the detections [Geréb, Maccagni, et al., 215] 2. All 248 sources Mid-InfraRed [22 µm] - Radio Power Relation This Talk [Maccagni et al., 217]

4 STRATEGY OF THE SURVEY Similar to APERTIF observations Flagging and automatic calibration Data Cube + Continuum Image Continuum source finder: location continuum sources (down to 1mJy/ 5mJy or even lower) Extract the location continuum sources Identify HI absorption detections: beam Bayesian line-finder [Allison et al 212] 4 2 Flux [mjy] 5 Flux [mjy] Noise [mjy] 1 Detection Frequency [ 1 9 Hz] Noise [mjy] 2 Non Detection Frequency [ 1 9 Hz]

5 STRATEGY FOR HI ABSORPTION SURVEYS 4 2 Flux [mjy] 5 Flux [mjy] 1 2 Noise [mjy] Detection Frequency [ 1 9 Hz] Noise [mjy] Non Detection Frequency [ 1 9 Hz] Intervening or associated? cross-correlation with spectral surveys Characterisation absorption (width, centre, asymmetry etc. using e.g. busy function) cross-correlation with LOFAR fields & other archives (SDSS, WISE) DATABASE Properties of the HI lines Properties of radio continuum (extent, spectral index, )

6 HI ABSORPTION LINES 66 detections line features measured with the BusyFunction [Westmeier, et al. 214] 3 < FWHM < 57 km/s 7 < FW2 < 64 km/s 3 main groups: Narrow lines: FWHM < 1 km/s Medium width lines: 1 km/s <FWHM < 2 < km/s Broad lines: FWHM > 2 km/s

7 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. NVSS major / minor axis Extended non-detection Compact non-detection Extended detection Compact detection Interacting detection Interacting non-detection FIRST peak / integrated flux

8 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) W1 W2 [ 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 The central AGN heats the surrounding circumnuclear dust W2 W3 [ µm]

9 DETECTING HI ABSORPTION 248 sources / 66 Detections 27 % ± 5.5 % detection rate Count All sources Detections Constant in redshift and radio power Det. Rate [%] z Compact sources and MIR bright HI often detected (~4%). Extended sources & dust-poor sources HI is rarely detected (~13%). Count Det. Rate [%] log 1 P 1.4GHz [W Hz 1 ] All sources Detections

10 KINEMATICS OF THE HI 8 Interacting sources Extended sources Compact sources P 1.4GHz < 1 24 W Hz -1 widths rotational velocity HI likely in a rotating disk. P 1.4GHz > 1 24 W Hz -1 broad asymmetric lines. FW2 [km s 1 ] log 1 P 1.4GHz [W Hz 1 ] Sources with broad lines are: Compact, i.e. jets within the galaxy. MIR bright, i.e. rich in heated dust. FW2 [km s 1 ] Interacting sources Dust-poor sources 12µm bright sources 4.6µm bright sources log 1 P 1.4GHz [W Hz 1 ]

11 KINEMATICS OF THE HI P 1.4GHz < 1 24 W Hz -1 lines centred at systemic velocity P 1.4GHz > 1 24 W Hz -1 lines offset w.r.t. systemic velocity offset is blue-shifted. vcentroid -vsystemic [km s 1 ] Interacting sources Extended sources Compact sources log 1 P 1.4GHz [W Hz 1 ] 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. vcentroid -vsystemic [km s 1 ] Interacting sources Dust-poor sources 12µm bright sources 4.6µm bright sources log 1 P 1.4GHz [W Hz 1 ]

12 STACKING EXPERIMENT Non-detections are important!!!!.3.2 Non Detections Stacking of 17 non-detections NO LINE is detected at ~.15 (3σ).1..1 Stacking of sub-groups of sources NO LINE is detected at ~.3 (3σ) Velocity [km s 1 ] Not even in compact sources or MIR.6.4 Compact non-detections Extended non-detections µm &4.6µm-bright non-detections Dust-poor non-detections.2.2 bright sources Velocity [km s 1 ] Velocity [km s 1 ]

13 STACKING THE ATLAS 3D NON-DETECTIONS ATLAS3D sources HI is not detected in the centre. STACKING: 3σ detection of HI emission N(HI) [ 1 17 cm 2 beam 1 ] N(HI) ~ 3.5 x 1 17 (T spin /c f ) cm -2 N(HI) converted in optical depth (T spin ~1 K, c f =1) τ~.6 <<.15 we need to stack more to detect this gas in absorption Velocity [km s 1 ] The HI stacking ATLAS 3D is warm? T spin τ ; T spin τ Stacking in absorption even more difficult

14 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 35 Observation Model Plane of the sky : x,y Side view: z,y From above: x,z

15 INTERPRETING HI ABSORPTION 3C 35 Optical Image (SDSS or other): i, PA of the stellar body Continuum image: against which radio lobe there is absorption? i [,18 ] PA [18, 36 ]

16 INTERPRETING HI ABSORPTION 3C 35 Optical Image (SDSS or other): i, PA of the stellar body Continuum image: against which radio lobe there is absorption? i [,18 ] PA [18, 36 ] MCMC algorithm Count find combination of parameters that best fits the observed line the line i = 45 ; PA = 27 PA [ ] Count I[] PA [ ]

17 INTERPRETING HI ABSORPTION The bulk of the absorption generated by a rotating disk: i = 45 ; PA = 27 Blue-shifted wing not reproduced by the model.5 Spectrum. Flux [mjy].5 Flux [mjy] Velocity [km s 1 ] observation model resitudals Plane of the sky View from above View from the side y [kpc]. z [kpc]. y [kpc] x [kpc] x [kpc] z [kpc]

18 INTERPRETING HI ABSORPTION Less information on the source? i [,18 ] PA [, 36 ] Count Flux [mjy] Flux [mjy] Spectrum Velocity [km s 1 ] observation model.1 resitudals PA [ ] I[] PA [ ] Best-fit solution: i = 55 ; PA = Count 8 4. Plane of the sky 8 4. View from above 8 4. View from the side VLBI high resolution continuum y [pc]. -4. z [pc]. -4. y [pc]. -4. Likely we can improve the fit x [pc] x [pc] z [pc]

19 CONCLUSIONS 27%±5.5% detection rate of HI in absorption HI detected at all redshifts (.2 < z <.23) and radio powers: promising for SHARP, MALS, FLASH Narrow lines HI mainly in a rotating disk P 1.4GHz < 1 24 W Hz -1, Extended sources, dust poor sources Broad asymmetric shifted lines: HI has unsettled kinematics P 1.4GHz> 1 24 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 (T spin >1 K)?

20 BLIND SURVEYS: AUTOMATIC SEARCH FOR HI ABSORPTION Extract the location of every continuum source in the FOV Line-finder: which one? Flux [mjy] Noise [mjy] 5 1 Detection Frequency [ 1 9 Hz] Flux [mjy] Noise [mjy] Non Detection Frequency [ 1 9 Hz] Intervening or associated? cross-correlation with spectral surveys Characterisation absorption (width, centre, asymmetry etc. e.g. busy function) DATABASE Properties of the HI lines Properties of radio continuum (size, spectral index, ) cross-correlation with LOFAR fields & other archives (SDSS, WISE) Comparison with models Stacking other ideas...