The Location and Kinematics of HI Absorbing Gas

The Location and Kinematics of HI Absorbing Gas
in GPS and CSS Radio Galaxies René Vermeulen Astron/NFRA, Dwingeloo, NL Work with Y.M. Pihlström, W. Tschager, W.H. de Vries, A. Labiano, P.D. Barthel, S.A. Baum, R. Braun, M.N. Bremer, J.E. Conway, G.K. Miley, C.P. O’Dea, H.J.A. Röttgering, R.T. Schilizzi, I.A.G. Snellen, G.B. Taylor.

CSO/GPS/CSS radio galaxies
Total radio extent is sub-galactic (15 kpc). Radio structure dominated by lobes; core may show free-free absorption. Now usually thought to be young sources ( years), rather than “frustrated” (e.g., based on observed velocities). But morphology is often distorted, and there is other evidence for a dense environment (ionised gas in optical, RM, X-rays, free-free absorption).

CSO/GPS/CSS radio galaxies
Studing gaseous environment of CSO/GPS/CSS radio galaxies is very interesting: --- What are conditions conducive to the birth of radio sources ? --- Feeding of the engine (infalling gas). --- Jet formation mechanisms (collimation, acceleration), and propagation through the ISM. --- Influence of the radio jets on their galactic environment.

Studing the neutral gas through HI absorption
Good technique because sensitivity is independent of distance. Needs bright radio structure to act as background. This is available at the right place in the compact radio sources. Jet/environment interactions are also likely sites of bright radio emission which can be studied.

Studing the neutral gas through HI absorption
Good technique because sensitivity is independent of distance. Needs bright radio structure to act as background. This is available at the right place in the compact radio sources. Jet/environment interactions are also likely sites of bright radio emission which can be studied. Most powerful CSO/GPS/CSS are at 0.2 < z < 1. But this is outside L-band 21cm range.

HI absorption line survey at the WSRT
UHF-high receivers: Wideband MHz, 0.2 < z < 0.9. Interferometer: superior RFI rejection and spectral calibration. 3C213.1 0.1 %

Vermeulen et al., Pihlström et al., 2003 A&A in press. Sample: all known compact sources (CSO, GPS, CSS) 19 detections out of 57 targets free of RFI at 0.2 < z < 0.9

Larger sources, lower column densities
N(HI)  (LS)-0.33

Line width typically 100-200 km/s
Some sources have narrow secondary line components

Line width typically 100-200 km/s
Some sources have narrow secondary line components FWHM is not strongly dependent on linear size

“Infall” or “outflow” ?  outflow infall  van Gorkom et al. 1989:
-500 500  outflow infall  van Gorkom et al. 1989: 8 nearby radio galaxies

“Infall” or “outflow” ?  outflow infall   outflow infall 
-500 500  outflow infall   outflow infall  van Gorkom et al. 1989: 8 nearby radio galaxies Our sample: 19 compact sources at 0.2 < z < 0.9 Optical redshifts may be imprecise but should not be biased

“Infall” or “outflow”; disks/tori or interaction/entrainment ?
Imaging of HI absorption in several nearby sources shows a circumnuclear, possibly toroidal or disk-like distribution. But in other nearby sources, HI absorption has been found in jet/cloud interaction regions (e.g. Morganti et al.).

Imaging of HI absorption in several nearby sources shows a circumnuclear, possibly toroidal or disk-like distribution. But in other nearby sources, HI absorption has been found in jet/cloud interaction regions (e.g. Morganti et al.). NGC1052: A detailed look shows complexity.

NGC 1052: closely resembling a GPS/CSS/CSO
Vermeulen et al. 2003 Elliptical Galaxy, LINER optical spectrum. cz=1474 km/s From starlight and emission lines. ==> 1 mas = 0.1 pc (D=22 Mpc H0=65 km/s/Mpc). Bright radio source (1Jy). Flat/inverted radio spectrum like a GPS. Twin radio jets, lobes spanning 3 kpc like a CSS. Bright twin inner jets, knots like a CSO.

NGC1052: 3 HI components, mostly local to AGN, redshifted

"Low velocity" HI broad: km/s, peak depth 2 % Asymmetrically straddles vsys. Galactic scale ?

"Patchy" HI narrow: 3-15 km/s, depths 5 % Several clouds in inner few pc region, extending a few tenths of a pc each. "Low velocity" HI broad: km/s, peak depth 2 % Asymmetrically straddles vsys. Galactic scale ?

"Patchy" HI narrow: 3-15 km/s, depths 5 % Several clouds in inner few pc region, extending a few tenths of a pc each. "Low velocity" HI broad: km/s, peak depth 2 % Asymmetrically straddles vsys. Galactic scale ? "High velocity" HI width km/s, depth varies % annulus/torus pc with central hole ?

Imaging of HI absorption in several nearby sources shows a circumnuclear, possibly toroidal or disk-like distribution. But in other nearby sources, HI absorption has been found in jet/cloud interaction regions (e.g. Morganti et al.). NGC1052 shows 3 different regions with neutral gas.

Imaging of HI absorption in several nearby sources shows a circumnuclear, possibly toroidal or disk-like distribution. But in other nearby sources, HI absorption has been found in jet/cloud interaction regions (e.g. Morganti et al.). NGC1052, z=0.005, shows 3 different regions with neutral gas. In order to access HI at z0.2, we have pushed to have VLBI at UHF frequencies on the EVN.

VLBI at UHF Frequencies
MHz, 0.2 < z < 0.9 for HI F. Briggs I. Browne C. Carilli J. Conway G. de Bruyn A. Kus K. Menten C. Moore R. Vermeulen Effelsberg 100m purpose-built receiver Jodrell Bank 76m "960MHz receiver" Onsala 25m purpose-built receiver Torun 32m purpose-built-receiver Westerbork "94m" UHF receivers Green Bank (140ft, GBT) VLBA (down to 1140 MHz only)

Locus of absorption in Pearson-Readhead CSOs.
Flux-limited 6cm Pearson-Readhead of 65 sources contains 7 CSOs. Name Peak optical depth 0.44 0.014 ? <0.0048 0.006 <0.0013 0.017 FWHM (km/s) 100 60 ? - 170 82

0108+388: HI in a free-free absorbing torus ?
852 MHz 44% absorption km/s wide

WSRT

Not yet resolved by VLBI at UHF WSRT Spectrum Carilli et al. 1997 WSRT

Not yet resolved by VLBI at UHF WSRT WSRT Shows substantial free-free absorption. VLBA

Not yet resolved by VLBI at UHF WSRT WSRT Shows substantial free-free absorption. VLBA  HI absorption in pc-scale torus ?

0404+768: HI in a jet/cloud interaction ?
886 MHz 1.4% absorption km/s wide 0.3% absorption 150 km/s wide

150 pc

150 pc Core has less total flux density than absorption line. Absorption line detected on EVN baselines.

150 pc Core has less total flux density than absorption line. Absorption line detected on EVN baselines.  Absorption must be in ~100 pc-scale lobe feature(s)

1031+567: No HI because core undetectable ?
973 MHz No HI detected <0.48% absorption

973 MHz No HI detected <0.48% absorption Core undetectable; probably free-free absorbed.

973 MHz No HI detected <0.48% absorption Core undetectable; probably free-free absorbed.  A pc-scale torus may have neutral gas, but there is no background to see it.

1358+624: large-scale absorption ?
993 MHz 0.6% absorption 170 km/s wide

1667 MHz and 993 MHz structures are hard to match. Line and continuum visibility seem to show the same amount of compact and extended structure (comparing EVN vs. Gb baselines).

1667 MHz and 993 MHz structures are hard to match. Line and continuum visibility seem to show the same amount of compact and extended structure (comparing EVN vs. Gb baselines).  HI absorption probably covers most of the (lobe) structure.

2021+614: no HI because core undetectable ?
1157 MHz No HI detected <0.13% absorption

1157 MHz No HI detected <0.13% absorption Core undetectable at low frequency; probably free-free absorbed.

1157 MHz No HI detected <0.13% absorption Core undetectable at low frequency; probably free-free absorbed.  A pc-scale torus may have neutral gas, but there is no background to see it.

2352+495: circumnuclear HI ? 1147 MHz 1.7% absorption 82 km/s wide

: circumnuclear HI ? 50 pc

2352+495: circumnuclear HI ? All of the absorbed flux density
50 pc All of the absorbed flux density is from the inner component.

2352+495: circumnuclear HI ? The inner component is mostly
50 pc The inner component is mostly an inner Northern jet, <50 pc.

is from the inner Northern jet, <50 pc.

is from the inner Northern jet, <50 pc.  Circumnuclear HI, in a 10 pc scale torus ?

Locus of absorption: PR-CSOs.
Flux-limited 6cm Pearson-Readhead of 65 sources contains 7 CSOs. Name Peak optical depth 0.44 0.014 ? <0.0048 0.006 <0.0013 0.017 FWHM (km/s) 100 60 ? - 170 82 Tentative Scenario Torus Interaction ? FFA Torus

2050+364: another complex case
1048 MHz 16.1% absorption 16 km/s wide 4.4% absorption 32 km/s wide

with A. Labiano

Deepest absorption only shifts 10 km/s over several hundred pc.

Deepest absorption only shifts 10 km/s over several hundred pc.  (Sub)galactic scale flow

Deepest absorption only shifts 10 km/s over several hundred pc. Shallow higher velocity absorption seen only to the West.  (Sub)galactic scale flow

Is a classical Compact Double or a bent Core-Jet source ? 1.05 GHz

Is a classical Compact Double or a bent Core-Jet source ? 0.6 GHz Lazio & Fey 2001

Is a classical Compact Double or a bent Core-Jet source ? 0.6 GHz 1.6 GHz Lazio & Fey 2001

Is a classical Compact Double or a bent Core-Jet source ? 0.6 GHz 1.6 GHz Lazio & Fey 2001 8.4 GHz

Is a classical Compact Double or a bent Core-Jet source ? 0.6 GHz 1.6 GHz Lazio & Fey 2001 Flattest spectrum, most compact: core + inner jet ? Steepest spectrum, most extended: continuation of jet Shock/bend in jet ? 8.4 GHz

Deepest absorption only shifts 10 km/s over several hundred pc. Shallow higher velocity absorption seen only to the West.  (Sub)galactic scale flow

Deepest absorption only shifts 10 km/s over several hundred pc. Shallow higher velocity absorption seen only to the West.  (Sub)galactic scale flow gets disturbed towards the core ?

3C49: Larger scale source with HI in one radio lobe
877 MHz 1.7% absorption 7 km/s wide 1.4% absorption 35 km/s wide

All of the HI aborption is in 1 lobe

All of the HI aborption is in 1 lobe  HI is associated with “aligned” [OII] emission in a sub-kpc sized lobe.

Summary WSRT survey detected HI absorption in 1/3 of compact sources:
wide range of opacities:   – 0.2, anticorrelated with linear size. VLBI follow-up shows disks/tori and interactions and flows (in and out). In different objects Within single objects

Summary Could it be that ... ?? --- Disks/tori with HI are ubiquitous, and are seen when the core is prominent enough and/or the lobes are close by (10 pc ?). --- Interactions with clouds containing HI happen in some sources. --- (Sub)galactic-sized flows can be detected if sensitivity allows.

Molecular gas: 4 OH lines, non-LTE, velocity regions
WSRT Spectrum

Molecular gas: 4 OH lines
18cm WSRT observations Vsys = 1474 km/s A) "Main lines" 1667 MHz and 1665 MHz: 1) % centred on Vsys, width 30 km/s 2) Red extension to 1570 km/s Together form the "low velocity" system ? 1667/1665 line ratio close to 1 : 1 (non-LTE) Is there a "patchy" system in OH ? 3) % feature over km/s Profile identical to "high velocity” HI system 1667/1665 ratio near 1.8 : 1 (LTE ??)

Molecular gas: 4 OH lines
18cm WSRT observations Vsys = 1474 km/s B) "Satellite lines" 1612 MHz, 1720 MHz: Only detectable in "high velocity" system. Peak depth 0.4 % 1612 MHz in absorption, 1720 MHz in emission. Mirror profiles. Shock excited ?

The inner jets: two-sided near-relativistic motions
Part of the 2cm VLBA Survey (Kellermann et al. 1998, AJ, 115, 1295). 10 observing epochs 1995 Jul Feb. Unambiguous 2-sided, probably linear motions. Near-relativistic: 0.78 ± 0.12 mas/yr = ± 0.04 c each side. Thus jets near plane of sky, angle >57°. Had to overcome "registration", "stroboscopic" effects: -- Central gap. -- Every few months new features emerge. -- Flux densities vary up and down as features move. Suggests patchy surrounding medium.

Ionised gas in inner parsec: disk/torus and more ?
Multi-wavelength VLBA observations: 1997 July, frequencies 1.4, 1.6, 5, 8, 15, 22, 43 GHz. Source almost symmetric at 43 GHz without gap. Deepening, widening gap towards lower frequencies: -- "hole" in central pc. -- western jet attenuated out to at least 1 pc. -- eastern jet also attenuated, but less deeply. Steeply inverted spectra: Free-Free Absorption. =1 at 43 GHz, l =0.5 pc, T=104 K  ne=105 cm-3

Atomic gas: 3 components, mostly local, redshifted
Vsys = 1474 km/s A) "Low velocity" component. broad: km/s, peak depth 2 % Asymmetrically straddles systemic velocity. B) "Patchy" component. narrow: 3-15 km/s, depths 5 %, in km/s C) "High velocity" component. width km/s, depth overall 10 % =0.02, l =0.5 pc, Tsp=100 K  nH=100 cm-3

21cm VLBA+Y27 observations Vsys = 1474 km/s A) "Low velocity" component. broad: km/s, peak depth 2 % Asymmetrically straddles systemic velocity. Visible wherever s/n allows: could be on galactic scales ? B) "Patchy" component. narrow: 3-15 km/s, depths 5 %, in km/s C) "High velocity" component. width km/s, depth overall 10 %

21cm VLBA+Y27 observations Vsys = 1474 km/s A) "Low velocity" component. broad: km/s, peak depth 2 % Asymmetrically straddles systemic velocity. Visible wherever s/n allows: could be on galactic scales ? B) "Patchy" component. narrow: 3-15 km/s, depths 5 %, in km/s Several features, extending few tenths of a pc each, detected along the inner 2 pc of the eastern jet. C) "High velocity" component. width km/s, depth overall 10 %

21cm VLBA+Y27 observations Vsys = 1474 km/s A) "Low velocity" component. broad: km/s, peak depth 2 % Asymmetrically straddles systemic velocity. Visible wherever s/n allows: could be on galactic scales ? B) "Patchy" component. narrow: 3-15 km/s, depths 5 %, in km/s Several features, extending few tenths of a pc each, detected along the inner 2 pc of the eastern jet. C) "High velocity" component. width km/s, depth varies % annulus pc with central hole, continuous velocity gradient 10 km/s/pc ?

Where are the absorbers in NGC 1052 ?
Central hole of radius 0.5 pc in high-velocity atomic gas. Corresponds to region of deepest free-free absorption. ==> Ionised inner region ! Agrees with X-ray low-energy absorption spectra. OH molecular gas follows same profile. But if edge-on disk, torus, annulus, then expect no velocity gradients, and no velocity offset from Vsys. And why are there "high velocity" water masers (molecular gas) within the Central Hole ( pc western jet) ? Is there CO in any of the velocity systems ?

UHF-high receivers: Wideband MHz, 0.2 < z < 0.9. Interferometer: superior RFI rejection and spectral calibration. Multi-channel backend IVC/DZB: superior RFI rejection and velocity resolution. Up to 1024 channels for all baselines in 2 polarisations.

Papers Vermeulen et al., Pihlström et al., 2003 A&A in press. Sample: all known compact sources (CSO, GPS, CSS) 19 detections out of 57 targets free of RFI at 0.2 < z < 0.9

Detection rate not flux density limited

Larger sources, lower column densities
N(HI)  (LS)-0.33

Possible radial density profiles
Spherical Distribution

Dotted: King profile: unlikely

Dotted: King profile: unlikely Solid: spherical model: quite possible, best fit n  r -1.25

Spherical Distribution Disk

Dotted: King profile: unlikely Disk model families: quite possible Solid: spherical model: quite possible, best fit n  r -1.25

2050+364: a complex case ? GPS at z=0.35
8.4 GHz GPS at z=0.35 Could this be a bent core-jet ?? Lazio & Fey 2001 0.6 GHz 1.6 GHz

: a complex case ? Is a Compact Double or a bent Core-Jet source ? 0.6 GHz Lazio & Fey 2001

2050+364: a complex case ? Complex kinematics over several 100 pc.
1.0 GHz Complex kinematics over several 100 pc. 8.4 GHz 0.6 GHz 1.6 GHz

with A. Labiano

0404+768: absorption in a jet/cloud interaction ?
(beware the bandwidth...) Core does not contain enough flux density for the absorption depth:  must be 100 pc-scale lobe(s)

In disks/tori, interactions, or flows ? Infall or outflow ?
Study individual examples: NGC 1052 at z=0.005 Some CSO/GPS at higher z with UHF VLBI Disks/tori and interactions and flows. Infall and outflow. In different objects Within single objects

Infall or outflow; disks/tori or interaction/entrainment ?
HI observations in several nearby sources suggested a circumnuclear, possibly toroidal or disk-like distribution. e.g. NGC315, NGC1275, NGC4261, Hydra-A, 4C31.04, NGC 3894, But in several other nearby sources HI has now also been found in jet/cloud interaction regions (e.g. Morganti et al.) GPS/CSS sources are unresolved with the WSRT, and the HI absorption regions need to be imaged with VLBI. In order to access HI at z0.2, we have developed VLBI at UHF frequencies on the EVN.

Advantages of spectroscopy with VLBI
VLBI arrays are very sensitive. - Can combine the collecting area of the entire Global Network. Long baselines can circumvent RFI. - Receivers often stay linear even with "typical RFI". - For optimal calibration one needs: + Good total power monitoring + Good uv-coverage and many stations

Locus of absorption: PR-CSOs.
Flux-limited 6cm Pearson-Readhead of 65 sources contains 7 CSOs. Est. ne (cm-3) 10000 10 ? - 1000 Name Peak optical depth 0.44 0.014 ? <0.0048 0.006 <0.0013 0.017 FWHM (km/s) 100 60 ? - 170 82 Est. N(H) (1020 cm-2 ) 7000 10 ? - 4 1000 Tentative Scenario Torus Interaction ? FFA Torus

The Location and Kinematics of HI Absorbing Gas

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The Location and Kinematics of HI Absorbing Gas

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