Obscuration of the Parsec‐Scale Jets in the Compact Symmetric Object 1946+708

Peck, A. B.; Taylor, G. B.; Conway, J. E.

doi:10.1086/307535

Cited by 93 publications

(107 citation statements)

References 36 publications

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“…VLBI studies available in the literature can be inspected to verify if such a trend exists. The covering factor is close to c f = 1 in the compact source 1946+708 (Peck et al 1999), however one can also find examples for compact sources with lower covering factor of c f ∼ 0.2 in B2352+495 (Araya et al 2010) and in 4C 12.5 . In extended sources c f = 1 is estimated in the re-started source 3C 293 (Beswick et al 2004).…”

Section: H I and Radio Morphologymentioning

confidence: 72%

Probing the gas content of radio galaxies through H I absorption stacking

Geréb

Morganti

Oosterloo

2014

A&A

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Using the Westerbork Synthesis Radio Telescope, we carried out shallow H i absorption observations of a flux-selected (S 1.4 GHz > 50 mJy) sample of 93 radio active galactic nuclei (AGN), which have available SDSS (Sloan Digital Sky Survey) redshifts between 0.02 < z < 0.23. Our main goal is to study the gas properties of radio sources down to S 1.4 GHz flux densities not systematically explored before using, for the first time, stacking of absorption spectra of extragalactic H i. Despite the shallow observations, we obtained a direct detection rate of ∼29%, comparable with deeper studies of radio galaxies. Furthermore, detections are found at every S 1.4 GHz flux level, showing that H i absorption detections are not biased toward brighter sources. The stacked profiles of detections and non-detections reveal a clear dichotomy in the presence of H i, with the 27 detections showing an average peak τ = 0.02 corresponding to N(H i) ∼ (7.4 ± 0.2) × 10 18 (T spin /c f ) cm −2 , while the 66 non-detections remain undetected upon stacking with a peak optical depth upper limit τ < 0.002 corresponding to N(H i) < (2.26 ± 0.06) × 10 17 (T spin /c f ) cm −2 (using a FWHM of 62 km s −1 , derived from the mean width of the detections). Separating the sample into compact and extended radio sources increases the detection rate, optical depth, and FWHM for the compact sample. The dichotomy for the stacked profiles of detections and non-detections still holds between these two groups of objects. We argue that orientation effects connected to a disk-like distribution of the H i can be partly responsible for the dichotomy that we see in our sample. However, orientation effects alone cannot explain all the observational results, and some of our galaxies must be genuinely depleted of cold gas. A fraction of the compact sources in the sample are confirmed by previous studies as likely young radio sources (compact steep spectrum and gigahertz peaked spectrum sources). These show an even higher detection rate of 55%. Along with their high integrated optical depth and wider profile, this reinforces the idea that young radio AGN are embedded in a medium that is rich in atomic gas. Part of our motivation is to probe for the presence of faint H i outflows at low optical depth using stacking. However, the stacked profiles do not reveal any significant blueshifted wing. We are currently collecting more data to investigate the presence of outflows. The results presented in this paper are particularly relevant for future surveys in two ways. The lack of bias toward bright sources is encouraging for the search for H i in sources with even lower radio fluxes planned by such surveys. The results also represent a reference point when searching for H i absorption at higher redshifts.

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Section: H I and Radio Morphologymentioning

confidence: 72%

Probing the gas content of radio galaxies through H I absorption stacking

Geréb

Morganti

Oosterloo

2014

A&A

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“…More sources are reported by Mack et al (2009). OH: Peck et al (1999), O'Dea et al (2005), Gupta et al (2006) observed, in total, a dozen objects without success. Their upper limits on OH column density are in the range 10 14 -10 15 cm −2 which is at least ten times less than in the galactic Giant Molecular Clouds and less than in other types of (few) radio galaxies.…”

Section: Moleculesmentioning

confidence: 95%

Radio properties of CSSs and GPSs

Fanti¹

2009

Astron Nachr

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“…However, the location of the radio and Xray absorbers in the host galaxy of the radio source are still debated too. In the limited sample of compact sources with available high angular resolution HI absorption measurements, the HI is typically detected against one or both radio lobes (Araya et al 2010, and references therein; Morganti et al 2013), with estimated covering factors, C f , vari-⋆ Data from the Westerbork Synthesis Radio Telescope ⋆⋆ Corresponding author:e-mail: ostorero@ph.unito.it able from ∼0.2 to ∼1 (e.g., Peck et al 1999;Morganti et al 2004). The general consensus is that the HI absorber has an inhomogeneous or clumpy nature, although the actual distribution of the gas is not known.…”

Section: Introductionmentioning

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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Obscuration of the Parsec‐Scale Jets in the Compact Symmetric Object 1946+708

Cited by 93 publications

References 36 publications

Probing the gas content of radio galaxies through H I absorption stacking

Probing the gas content of radio galaxies through H I absorption stacking

Radio properties of CSSs and GPSs

N_H‐N_HI correlation in gigahertz‐peaked‐spectrum galaxies

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Obscuration of the Parsec‐Scale Jets in the Compact Symmetric Object 1946+708

Cited by 93 publications

References 36 publications

Probing the gas content of radio galaxies through H I absorption stacking

Probing the gas content of radio galaxies through H I absorption stacking

Radio properties of CSSs and GPSs

NH‐NHI correlation in gigahertz‐peaked‐spectrum galaxies

Contact Info

Product

Resources

About

N_H‐N_HI correlation in gigahertz‐peaked‐spectrum galaxies