Observations of H I absorbing gas in compact radio sources at cosmological redshifts

Vermeulen, R. C.; Pihlström, Y. M.; Tschager, W.; Vries, W. H. de; Conway, J.; Barthel, P. D.; Baum, Stefi A.; Braun, Róbert; Bremer, M. N.; Miley, G. K.; O’Dea, C. P.; Röttgering, H. J. A.; Schilizzi, R. T.; Snellen, I. A. G.; Taylor, G. B.

doi:10.1051/0004-6361:20030468

Cited by 137 publications

(265 citation statements)

References 27 publications

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“…However, as well as occuring in outflowing gas (e.g. Vermeulen et al 2003;Morganti et al 2003Morganti et al , 2005aMorganti et al ,b, 2007Allison et al 2016), the bulk of the absorption is believed to occur in the large-scale galactic disk, rather than the sub-pc torus 13 , which is expected to have a random orientation to the radio jets (Curran & Whiting 2010 and references therein).…”

Section: Discussionmentioning

confidence: 99%

Atomic and molecular absorption in redshifted radio sources

Curran

Whiting

Allison

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We report on a survey for associated H I 21-cm and OH 18-cm absorption with the Giant Metrewave Radio Telescope at redshifts z ≈ 0.2 − 0.4. Although the low redshift selection ensures that our targets are below the critical ultra-violet luminosity (L UV ∼ 10 23 W Hz −1 ), which is hypothesised to ionise all of the neutral gas in the host galaxy, we do not obtain any detections in the six sources searched. Analysing these in context of the previous surveys, in addition to the anti-correlation with the ultra-violet luminosity (ionising photon rate), we find a correlation between the strength of the absorption and the blue -near-infrared colour, as well as the radio-band turnover frequency. We believe that these are due to the photo-ionisation of the neutral gas, an obscured sight-line being more conducive to the presence of cold gas and the compact radio emission being better intercepted by the absorbing gas, maximising the flux coverage, respectively. Regarding the photo-ionisation, the compilation of the previous surveys increases the significance of the critical ionising photon rate, above which all of the gas in the host galaxy is hypothesised to be ionised (Q H I ≈ 3 × 10 56 sec −1 ), to > 5σ. This reaffirms that this is an ubiquitous effect, which has profound implications for the detection of neutral gas in these objects with the Square Kilometre Array.

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Section: Discussionmentioning

confidence: 99%

Atomic and molecular absorption in redshifted radio sources

Curran

Whiting

Allison

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…This sample is composed of 21 sources, belonging to at least one of the following GPS samples: Stanghellini et al (1998), Snellen et al (1998), Torniainen et al (2007), and Vermeulen et al (2003). All of these sources were also classified as CSOs.…”

Section: Source Samplementioning

confidence: 99%

“…The observing band was 10 to 20 MHz wide, with 1024 spectral channels, and was centered at the frequency where the HI absorption line is expected to occur based on the optical redshift. Compared to the HI survey of compact sources by Vermeulen et al (2003), our observations could benefit from a larger ratio between number of spectral channels and observing band width: this improvement, together with the longer exposure times, enabled a more effective separation of narrow HI absorption features from radio frequency interferences (RFI) in most of the previously observed sources. The data reduction process and the results of the analysis will be presented elsewhere.…”

Section: Hi Observations With the Wsrtmentioning

confidence: 99%

N_H‐N_HI correlation in gigahertz‐peaked‐spectrum galaxies

et al. 2016

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With the Westerbork Synthesis Radio Telescope, we performed HI observations of a sample of known X-ray emitting Gigahertz-peaked-spectrum galaxies with compact-symmetric-object morphology (GPS/CSOs) that lacked an HI absorption detection. We combined radio and X-ray data of the full sample of X-ray emitting GPS/CSOs and found a significant, positive correlation between the column densities of the total and neutral hydrogen (NH and NHI, respectively). Using a Bayesian approach, we simultaneously quantified the parameters of the NH -NHI relation and the intrinsic spread of the data set. For a specific subset of our sample, we found NH∝NHI b , with b = 0.93 +0.49 −0.33 , and σint(NH) = 1.27 +1.30 −0.40 . The NH -NHI correlation suggests a connection between the physical properties of the radio and X-ray absorbing gas.

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“…with detection rates of ∼20 -40% in Vermeulen et al 2003; Gupta et al 2006;Chandola et al 2011). Fur-thermore, Curran et al (2016c) shows that the Hi detection rate is proportional to the turnover frequency, which is inversely proportional to source size.…”

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confidence: 99%

Hi absorption in nearby compact radio galaxies

Glowacki

Allison

Sadler

et al. 2017

Mon. Not. R. Astron. Soc.

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Hi absorption studies yield information on both AGN feeding and feedback processes. This AGN activity interacts with the neutral gas in compact radio sources, which are believed to represent the young or recently re-triggered AGN population. We present the results of a survey for Hi absorption in a sample of 66 compact radio sources at 0.040 < z < 0.096 with the Australia Telescope Compact Array. In total, we obtained seven detections, five of which are new, with a large range of peak optical depths (3% to 87%). Of the detections, 71% exhibit asymmetric, broad (∆v FWHM > 100 km s −1 ) features, indicative of disturbed gas kinematics. Such broad, shallow and offset features are also found within low-excitation radio galaxies which is attributed to disturbed circumnuclear gas, consistent with early-type galaxies typically devoid of a gas-rich disk. Comparing mid-infrared colours of our galaxies with Hi detections indicates that narrow and deep absorption features are preferentially found in late-type and high-excitation radio galaxies in our sample. These features are attributed to gas in galactic disks. By combining XMM-Newton archival data with 21-cm data, we find support that absorbed X-ray sources may be good tracers of HI content within the host galaxy. This sample extends previous Hi surveys in compact radio galaxies to lower radio luminosities and provides a basis for future work exploring the higher redshift universe.

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Observations of H I absorbing gas in compact radio sources at cosmological redshifts

Cited by 137 publications

References 27 publications

Atomic and molecular absorption in redshifted radio sources

Atomic and molecular absorption in redshifted radio sources

N_H‐N_HI correlation in gigahertz‐peaked‐spectrum galaxies

Hi absorption in nearby compact radio galaxies

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Observations of H I absorbing gas in compact radio sources at cosmological redshifts

Cited by 137 publications

References 27 publications

Atomic and molecular absorption in redshifted radio sources

Atomic and molecular absorption in redshifted radio sources

NH‐NHI correlation in gigahertz‐peaked‐spectrum galaxies

Hi absorption in nearby compact radio galaxies

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N_H‐N_HI correlation in gigahertz‐peaked‐spectrum galaxies